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[Yohei Onodera](https://orcid.org/0000-0002-3080-6991), Yasuyuki Takimoto, Hiroyuki Hijiya, Noriyoshi Kayaba, Masamichi Tanida, [Kazutaka Ikeda](https://orcid.org/0000-0002-1257-1850), [Shinji Kohara](https://orcid.org/0000-0001-9596-2680)

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[Lithium coordination disorder controlling ionic conductivity in mixed-halide borate glasses](https://mdr.nims.go.jp/datasets/22914342-7281-4d25-a434-ebaeefa34fc3)

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Lithium coordination disorder controlling ionic conductivity in mixed-halide borate glassesJournal ofMaterials Chemistry APAPEROpen Access Article. Published on 01 April 2026. Downloaded on 6/17/2026 12:35:29 AM.  This article is licensed under a Creative Commons Attribution 3.0 Unported Licence.View Article OnlineView Journal  | View IssueLithium coordinaaCenter for Basic Research on Materials, Natio1-2-1, Tsukuba, Ibaraki 305-0047, Japan. E-mbInnovative Technology Laboratories, AGYokohama, Kanagawa 230-0045, JapancMaterials Integration Laboratories, AGCYokohama, Kanagawa 230-0045, JapandElectronic Materials General Division,Marunouchi, Chiyoda-Ku, Tokyo 100-8405,eNeutron Industrial Application PromotOrganization for Science and Society, 1621106, JapanCite this: J. Mater. Chem. A, 2026, 14,23026Received 11th December 2025Accepted 23rd March 2026DOI: 10.1039/d5ta10123arsc.li/materials-a23026 | J. Mater. Chem. A, 2026, 14tion disorder controlling ionicconductivity in mixed-halide borate glassesYohei Onodera, *a Yasuyuki Takimoto,b Hiroyuki Hijiya,c Noriyoshi Kayaba,cMasamichi Tanida,d Kazutaka Ikeda e and Shinji Kohara aUnderstanding the structure–property relationships in glasses remains challenging owing to their structuralcomplexity, especially in multicomponent practical glasses. In this work, neutron diffraction with isotopicsubstitution was employed to investigate lithium coordination environments in halide (chloride and/orbromide)-doped borate glasses, which exhibit variations in lithium-ion conductivity associated with anionmixing. Lithium-specific neutron pair distribution function analysis reveals that the conductivityenhancement in oxide–halide mixed glasses originates from the breaking of one short Li–O bond andthe formation of two longer Li–halogen bonds. The formation of LiO3Cl2 and LiO3Br2 units is observed inchloride- and bromide-doped glasses, respectively, whereas a glass containing equal amounts ofchloride and bromide exhibits LiO3ClBr units in addition to LiO3Cl2 and LiO3Br2 units. These resultssuggest that the coexistence of multiple lithium–oxygen–halogen polyhedral units hinders lithium-ionmigration, leading to reduced ionic conductivity in halide–halide mixed glasses. This work provides newinsights into the structure–property relationships in lithium-ion conducting glasses through lithium-specific structural analysis.1. IntroductionGlasses with high ionic conductivity have attracted considerableattention since the discovery of superionic conducting glassesby Minami and coworkers in 1977.1,2 In recent years, there hasbeen an increase in research focusing on the practical utiliza-tion of ionic conducting glasses as solid electrolytes for lithium-ion batteries, particularly for portable devices and electricvehicles.3,4 The substitution of a ammable organic electrolytein conventional lithium-ion batteries with a solid electrolyte hasthe potential to enhance battery safety and improve energy andpower densities. Consequently, candidate materials mustexhibit high ionic conductivity when utilized as solid electro-lytes. A comprehensive understanding of lithium-ion conduc-tion mechanisms in solid electrolytes is essential for thedevelopment of new materials with high ionic conductivity. Themechanism of lithium-ion conduction in crystalline ionicnal Institute for Materials Science, Sengenail: ONODERA.Yohei@nims.go.jpC, Inc., 1-1 Suehiro-cho, Tsurumi-ku,, Inc., 1-1 Suehiro-cho, Tsurumi-ku,Electronics Company, AGC Inc., 1-5-1Japanion Center, Comprehensive Research-1 Shirakata, Tokai, Naka, Ibaraki 319-, 23026–23037conductors has been elucidated through crystal structureanalysis,5,6 which has accelerated materials development. Incontrast, the absence of long-range order in glasses makesanalytical approaches developed for crystalline materials inap-plicable. Therefore, structural studies of glasses requirea combination of techniques, including diffraction, spectros-copy, and computer simulations, to elucidate the mechanismunderlying ionic conductivity.Numerous studies have been conducted on ionic conductingoxide and sulde glasses to date. In oxide glasses, borate-7 andphosphate-8 based glasses are known to exhibit lithium-ionconductivity. Recently, ternary lithium borovanadate (Li2O–V2O5–B2O3) glasses have been reported to exhibit an ionic conductivity ofthe order of 10−4 S cm−1 at room temperature, representing thehighest level of ionic conductivity among oxide glasses.9 Structuralstudies have shown that lithium incorporation signicantlymodies the glass network. For example, 10B nuclear magneticresonance (NMR) spectroscopy revealed that the structural units inbinary Li2O–B2O3 glasses transform from boroxol, diborate, andtetraborate units to metaborate, pyroborate, orthoborate, andloose BO4 tetrahedral units with increasing Li2O content, creatingnon-bridging oxygens.10 An increase in the number of non-bridging oxygens with increasing Li2O content has also beenobserved in Li2O–V2O5–B2O3 glasses.9 Similar depolymerization ofthe network consisting of PO4 tetrahedra has also been observed inLi2O–P2O5 glasses based on 31P magic angle spinning (MAS) NMRmeasurements.11On the other hand, X-ray and neutron diffractionstudies demonstrated that lithium ions are tetrahedrallyThis journal is © The Royal Society of Chemistry 2026http://crossmark.crossref.org/dialog/?doi=10.1039/d5ta10123a&domain=pdf&date_stamp=2026-06-11http://orcid.org/0000-0002-3080-6991http://orcid.org/0000-0002-1257-1850http://orcid.org/0000-0001-9596-2680http://creativecommons.org/licenses/by/3.0/http://creativecommons.org/licenses/by/3.0/https://doi.org/10.1039/d5ta10123ahttps://pubs.rsc.org/en/journals/journal/TAhttps://pubs.rsc.org/en/journals/journal/TA?issueid=TA014035Paper Journal of Materials Chemistry AOpen Access Article. Published on 01 April 2026. Downloaded on 6/17/2026 12:35:29 AM.  This article is licensed under a Creative Commons Attribution 3.0 Unported Licence.View Article Onlinecoordinated by four oxygen atoms in borate and phosphateglasses.12–14 Moreover, ionic conduction pathways in these glasseshave been visualized using bond valence (BV) analysis of structuremodels generated by reverse Monte Carlo (RMC) modelling basedon diffraction data.15–18 In sulde glasses, the development ofLi7P3S11 glass ceramic obtained by partial crystallization of 70Li2S–30P2S5 glass, which exhibits an ionic conductivity exceeding10−3 S cm−1 comparable to that of organic liquid electrolytes, hassignicantly stimulated research in the Li2S–P2S5 system.19 Spec-troscopic studies using Raman19 and 31P MAS NMR20,21 techniquesrevealed that the fundamental structural units in 70Li2S–30P2S5glass and Li7P3S11 glass ceramic are thiophosphate species such asP2S74− and PS43−. Structural analyses combining diffractionexperiments and RMC modelling have indicated that fourfoldcoordination around lithium ions plays an important role in ionicconduction22 and have enabled visualization of conduction path-ways23 through BV analysis.15–18 Recent studies combining RMCmodelling and rst-principles calculations have further clariedthe structural and dynamical features associated with lithium-ionmigration in Li2S–P2S5 glasses.24–26Consequently, lithium-ion-conducting glasses have beenextensively investigated in response to growing interest in all-solid-state lithium-ion batteries. However, the intricate interplaybetween the lithium coordination environment and the conduc-tion mechanism in glasses remains incompletely understood.Understanding this relationship is crucial for the rational designof glassy solid electrolytes with improved ionic conductivity.Beyond studies focused directly on ionic conduction, it is wellrecognized that the physical and functional properties of multi-component glasses can be systematically tuned through compo-sitional variation. Variations in cation and anion species havebeen shown to modify optical, dielectric, and mechanical prop-erties in a variety of multicomponent oxide glasses, includingrare-earth-doped lead–silicate27 and lead–borate28 glasses, lithiumuoroborophosphate glasses,29 CuO-doped silicate30 and alumi-nosilicate31 glasses, and halide-substituted borophosphateglasses.32 These ndings highlight that compositional diversitystrongly inuences both local structures and macroscopic prop-erties in glasses. In particular, glasses containing mixed anionshave attracted attention because combining different anionspecies can signicantly inuence ionic conductivity.33,34 Never-theless, only a limited number of structural studies have beenreported for such mixed-anion glasses.One major challenge arises from the difficulty of extractinglithium-related structural information from the disorderedatomic arrangements of multicomponent glasses, even whenneutron diffraction, which is sensitive to light elements, isemployed. Lithium exhibits a negative neutron coherent scat-tering length (b = −1.90 fm),35 and atomic correlations betweenlithium and other atoms appear as negative peaks in the pairdistribution function (PDF) obtained by neutron diffraction.However, in multicomponent glasses, these negative peaksoen overlap with other positive peaks, making quantitativestructural analysis extremely difficult. Therefore, an element-specic experimental approach is required to determine thelithium coordination environment and to clarify its role in ionicconduction.This journal is © The Royal Society of Chemistry 2026In this study, we investigated ve compositions of 1/3Li2O–1/3B2O3–1/3LiCl1−xBrx glasses, in which single Cl, single Br, andmixtures of Cl and Br in the ratios of 1 : 3, 1 : 1, and 3 : 1 wereadopted. To clarify the effect of the addition and mixing ofhalide anions on ionic conductivity, the structures of the glasseswere examined using a combination of high-energy X-ray andneutron diffraction measurements. Specically, in this study,we employed the neutron diffraction with isotopic substitution(NDIS) technique36–38 to investigate lithium-specic atomiccorrelations. The NDIS technique utilizes the difference inneutron coherent scattering lengths between isotopes andallows us to obtain element-specic structural information.Indeed, structural studies with a particular focus on lithiumusing NDIS have been reported for Li2O–2SiO2,39 Li2O–2B2O3,40and LiAlSiO4 glasses.41 In this study, two glasses with differentlithium isotopic enrichments were prepared, enabling lithium-specic structural data to be obtained from the differencebetween neutron diffraction data. Consequently, the inter-atomic distances and coordination numbers around lithiumcations were determined by lithium-specic PDF analysisemploying the NDIS data. The coordination numbers for non-lithium-related correlations were also determined usingneutron diffraction data of nullLi-enriched glasses, where thecoherent neutron scattering length of lithium is adjusted tozero. In addition, the structural parameters obtained wereveried through their application to the reproduction of high-energy X-ray diffraction data. Thus, a cutting-edge structuralanalysis, founded upon element-specic quantum beammeasurements, has been meticulously executed. In this work,we investigate the relationship between the lithium coordina-tion environments and ionic conductivity in 1/3Li2O–1/3B2O3–1/3LiCl1−xBrx glasses using lithium-specic structural infor-mation obtained by our novel structural analysis.2. Experimental2.1 Preparation of glassesThe 1/3Li2O–1/3B2O3–1/3LiCl1−xBrx (x= 0, 0.25, 0.5, 0.75, and 1)glasses were prepared from mixtures of reagent-grade Li2CO3,H311BO3, LiCl, and LiBr. The mixtures were melted at 900–1000 °C for 15 min, and each melt was then quenched by thetwin-roller method. In this study, two types of glasses withdifferent lithium isotope ratios were prepared: natLi-enriched 1/3Li2O–1/3B2O3–1/3LiCl1−xBrx glasses (natLi glasses) and nullLi-enriched 1/3Li2O–1/3B2O3–1/3LiCl1–xBrx glasses (nullLi glasses).For the preparation of the nullLi glasses, a mixture of natLi2CO3and 6Li2CO3 was used to achieve the nullLi composition (6Li : 7Li= 0.5265 : 0.4735). For comparison, the 0.5Li2O–0.5B2O3 (LiBO2)glass was also prepared in a similar manner to the 1/3Li2O–1/3B2O3–1/3LiCl1−xBrx glasses. The densities of the glasses weremeasured by helium gas pycnometry using a AccuPyc II 1340 gaspycnometer (Micrometrics, USA).2.2 Conductivity measurementsThe electrical conductivities of the 1/3Li2O–1/3B2O3–1/3LiCl1−xBrx glasses were measured at room temperature by theJ. Mater. Chem. A, 2026, 14, 23026–23037 | 23027http://creativecommons.org/licenses/by/3.0/http://creativecommons.org/licenses/by/3.0/https://doi.org/10.1039/d5ta10123aJournal of Materials Chemistry A PaperOpen Access Article. Published on 01 April 2026. Downloaded on 6/17/2026 12:35:29 AM.  This article is licensed under a Creative Commons Attribution 3.0 Unported Licence.View Article Onlineac four-probe method using a Solartron SI 1287 frequencyresponse analyser (Solartron Analytical, UK). Au electrodes witha diameter of 4 mmwere formed on both sides of the glass-akesamples by vacuum deposition. The applied voltage was 50 mV,and the frequency range was from 1 Hz to 1 MHz. Allmeasurements were carried out under a dry-air atmosphere.The electrical conductivities of the glasses were determinedfrom the resistance values obtained at the real-axis intercept ofthe Nyquist plots.2.3 NMR measurements11B MAS NMR experiments were conducted on the 1/3Li2O–1/3B2O3–1/3LiCl1−xBrx glass samples at room temperature usingan ECA600 spectrometer (JEOL, Japan). The experiments wereconducted with a 11B Larmor frequency of 192.55 MHz witha spin rate of 20 kHz and a pulse delay of 3 s. The 11B chemicalshis were estimated with respect to an external saturated boricacid solution (19.6 ppm). The obtained spectra were subse-quently deconvoluted into two components.2.4 Diffraction measurementsThe high-energy X-ray diffraction experiments were conductedat beamline BL04B2 at SPring-8 (Hyogo, Japan) using a diffrac-tometer dedicated to disordered materials.42 Crushed glasssamples were loaded into SiO2 glass capillaries. The incident X-ray energy was 61.23 keV. The diffraction patterns of the glasseswere measured at room temperature in transmission geometry.The intensity of the incident X-rays was monitored in an Ar-lled ionization chamber, and the scattered X-rays were detec-ted using four CdTe detectors and three Ge detectors. A vacuumchamber was used to suppress air scattering around the sample.The raw data were corrected for polarization, absorption, andbackground, and the contribution of Compton scattering wassubtracted using standard data analysis soware.43The neutron diffraction measurements were conducted onthe high-intensity total diffractometer, NOVA,44 installed atbeamline BL21 of the Materials and Life Science ExperimentalFacility (MLF) at the J-PARC spallation neutron source (Ibaraki,Japan). The crushed glass samples were loaded into vanadium–nickel (V–Ni) null alloy cells with an outer diameter of 6.0 mmand a thickness of 0.1 mm. The wavelength range of the inci-dent neutron beam was 0.12 < l < 8.3 Å. Measurements wereperformed for the samples contained in the V–Ni cell, the emptyV–Ni cell, the empty instrument, and a vanadium standard fornormalization at room temperature. The observed scatteringintensities for the samples were corrected for the instrumentbackground and for attenuation by the sample and cell.Subsequently, the corrected intensities were normalized usingthe incident beam prole and further corrected for multiple andincoherent scattering.The fully corrected X-ray and neutron diffraction data werenormalized to give the Faber–Ziman total structure factor S(Q):45SðQÞ ¼ 1þ 1jhWðQÞij2Xna¼1Xnb¼1cacbwaðQÞwbðQÞ½SabðQÞ � 1�;(1)23028 | J. Mater. Chem. A, 2026, 14, 23026–23037where ca is the atomic fraction of chemical species a and wa(Q)represents either a Q-dependent atomic scattering (form) factor[fa(Q)] with a dispersion term in X-ray diffraction or a Q-inde-pendent coherent scattering length (ba) in neutron diffraction.Sab(Q) is the partial structure factor for the chemical speciesa and b, andhWðQÞi ¼Xna¼1cawaðQÞ: (2)Total correlation functions, T(r), were obtained by a Fouriertransform of S(Q) with a Lorch function, M(Q).46TðrÞ ¼ 4prrþ 2pðQmaxQminðSðQÞ � 1ÞsinðQrÞMðQÞdQ (3)Here, r is the average number density.To obtain lithium-specic structural information, the NDISwas employed. The NDIS technique allows element-specicstructural information to be obtained by utilizing the differ-ence in coherent neutron scattering lengths between isotopes.In the present study, two glasses with identical chemicalcompositions but different lithium isotopic ratios (natLi andnullLi glasses) were prepared. Because only the neutron scat-tering length of lithium differs between the two samples, takingthe difference between the diffraction data extract structuralcorrelations involving lithium atoms. The differential intensityDLiI(Q) between the scattering intensities of the natLi and nullLiglasses is expressed asDLiIcoh(Q) = DLi[hb2i − hbi2] + DLi[hb2i]DLiS(Q), (4)andhbi2 ¼ Xacaba!2; (5)hbi2 ¼Xacaba2; (6)where the term DLi[ ] denotes the difference between the valuesin the brackets for the natLi and nullLi glasses. The differentialstructure factor DLiS(Q) can be expressed as a linear combina-tion of the partial structure factors, Sab(Q), as follows:DLiSðQÞ ¼Xna¼1Xnb¼1DLiwabSabðQÞ; (7)where the weighting factors DLiwab are given byDLiwab ¼ cacbDLi½babb�DLihhbi2i: (8)Compared with the total structure factors S(Q) obtained fromX-ray and neutron diffraction, DLiS(Q) signicantly enhancesthe contributions from Li-related Sab(Q) while suppressingcontributions from the other partials. Accordingly, DLiS(Q) forthe 1/3Li2O–1/3B2O3–1/3LiCl1−xBrx glasses can be expressed asThis journal is © The Royal Society of Chemistry 2026http://creativecommons.org/licenses/by/3.0/http://creativecommons.org/licenses/by/3.0/https://doi.org/10.1039/d5ta10123aTable 1 Compositions of glassesGlass sampleElement (at%)Li B O Cl BrBr100 31.6 18.9 39.1 0 10.4Cl25Br75 30.6 19.6 39.7 2.5 7.5Cl50Br50 30.1 20.3 41.3 4.3 4.0Cl75Br25 28.0 21.5 42.0 6.7 1.8Cl100 29.4 20.5 40.8 9.3 0Table 2 Mass density and atomic number density of glassesGlass sample Density (g cm−3) Number density (Å−3)Br100 2.47 0.0790Cl25Br75 2.38 0.0817Cl50Br50 2.28 0.0874Cl75Br25 2.18 0.0884Cl100 2.06 0.0880Fig. 1 Electrical conductivity of the 1/3Li2O–1/3B2O3–1/3LiCl1−xBrxglasses.Paper Journal of Materials Chemistry AOpen Access Article. Published on 01 April 2026. Downloaded on 6/17/2026 12:35:29 AM.  This article is licensed under a Creative Commons Attribution 3.0 Unported Licence.View Article OnlineDLiS(Q) = DLiwLiLiSLiLi(Q) + 2DLiwLiBSLiB(Q)+ 2DLiwLiOSLiO(Q) + 2DLiwLiClSLiCl(Q)+ 2DLiwLiBrSLiBr(Q), (9)where the weighting factors for the partials other than thosementioned above were negligible; therefore, these partialstructure factors were effectively eliminated in DLiS(Q).To obtain detailed structural information on the short range,S(Q) and T(r) were analysed using the pair function methodproposed by Mozzi and Warren.47 The pair function method isuseful for analysing real-space functions from which thestructural parameters such as the interatomic distance andcoordination number can be determined. Utilizing the pairfunction formalism, the calculated total correlation functionTcalc(r) was obtained using the following equation for theinteratomic distance ra–b and coordination number Na–b of thea–b pair:T calca�bðrÞ ¼2pðQmaxQmin2caNa�bwaðQÞwbðQÞhWðQÞi2 exp�� 12la�b2Q2�� sinðpQ=QmaxÞpQ=QmaxsinðQra�bÞra�bsin QrdQ: (10)The term la–b is a convergence factor representing the staticand thermal disorders of the a–b correlation. The calculateddifferential total correlation function DLiTcalc(r) was also ob-tained using the following equation for the interatomic distancerLi–b and coordination number NLi–b of the Li–b pair:DLiTcalcLi�bðrÞ ¼2pðQmaxQmin2cLiNLi�bDLi½bLibb�DLihbi2exp�� 12lLi�b2Q2�� sinðpQ=QmaxÞpQ=QmaxsinðQrLi�bÞrLi�bsin QrdQ:(11)The variations in ra–b (rLi–b) and Na–b (NLi–b) obtained fromthe tting T(r) and DLiT(r) were estimated to be ±0.02 Å and±0.3, respectively.3. Results and discussion3.1 Glass composition and densityThe chemical compositions of the obtained 1/3Li2O–1/3B2O3–1/3LiCl1−xBrx glasses are listed in Table 1. The glasses are designatedby the ratio of Cl to Br, e.g., Cl50Br50 refers to a glass containing anequal mixture of Cl and Br (1/3Li2O–1/3B2O3–1/3LiCl0.5Br0.5 glass).The densities of the 1/3Li2O–1/3B2O3–1/3LiCl1–xBrx glasses aresummarized in Table 2. The density increases monotonically withthe degree of Br substitution. The average number densities r ofthe 1/3Li2O–1/3B2O3–1/3LiCl1−xBrx glasses, calculated from thesedensities, are also listed in Table 2.3.2 ConductivityThe electrical conductivities of the 1/3Li2O–1/3B2O3–1/3LiCl1−xBrx glasses range from 2.7 × 10−6 to 6.6 × 10−6 S cm−1at room temperature (Fig. 1). These values are approximatelyThis journal is © The Royal Society of Chemistry 2026one order of magnitude higher than those of LiBO2 glass(∼10−7 S cm−1),48–50 indicating that the addition of halideanions enhances the lithium-ion conductivity. Similar behav-iour has been reported in other glass systems, including Li2O–B2O3–LiX (X = F, Cl, Br, I),7 LiPO3–LiX (X = Cl, Br, I),51 and Li2S–B2S3–LiI.52It is well established that the mixing of different types ofanion, known as the mixed-anion effect, enhances lithium-ionconductivity in various glass systems.33,34 Indeed, the 1/3Li2O–1/3B2O3–1/3LiCl1−xBrx glasses exhibit enhanced conductivity incomparison with LiBO2 glass, attributable to themixing of oxideand halide anions. In contrast, the Cl25Br75, Cl50Br50, andCl75Br25 glasses exhibit a substantial decrease in conductivitycompared with the Cl100 and Br100 glasses, as shown in Fig. 1.In particular, the Cl50Br50 glass exhibits the lowest conductivityamong the 1/3Li2O–1/3B2O3–1/3LiCl1−xBrx glasses, suggestingthat the mixing of halide anions leads to a reduction inconductivity. Therefore, the variation in ionic conductivity forthe 1/3Li2O–1/3B2O3–1/3LiCl1−xBrx glasses can be interpreted inJ. Mater. Chem. A, 2026, 14, 23026–23037 | 23029http://creativecommons.org/licenses/by/3.0/http://creativecommons.org/licenses/by/3.0/https://doi.org/10.1039/d5ta10123aFig. 2 X-ray diffraction data of LiBO2 glasses in (a)Q space and (b) realspace. Red solid curves represent experimental data, and black brokencurves represent calculated data.Journal of Materials Chemistry A PaperOpen Access Article. Published on 01 April 2026. Downloaded on 6/17/2026 12:35:29 AM.  This article is licensed under a Creative Commons Attribution 3.0 Unported Licence.View Article Onlinetwo stages: (i) enhancement of ionic conductivity induced by themixing of oxide and halide anions, and (ii) reduction of ionicconductivity caused by the mixing of halide (chloride andbromide) anions. A comparable phenomenon is observed insilicate glasses exhibiting the mixed alkali effect, where alkalimixing leads to substantial reductions in conductivity, viscosity,and dielectric constant.53–55 In our previous study, a combina-tion of PDF analysis with structural modelling revealed thatpotassium ions were trapped within highly coordinated potas-sium–oxygen polyhedra, forming a correlated pair arrangementwith sodium–oxygen polyhedra in a silicate glass with the mixedalkali effect.55 Therefore, the variation in ionic conductivityshown in Fig. 1 is closely related to changes in the lithiumcoordination environment in the 1/3Li2O–1/3B2O3–1/3LiCl1−x-Brx glasses. To elucidate the structural origin of this behaviour,the local atomistic structure around lithium ions was examinedby combining high-energy X-ray diffraction and NDIS.Table 3 Structural parameters for B–O, Li–O, O–O, B–B, and Li–B corB–O (I) B–O (II) Li–O (I)rB–O (Å) NB–O rB–O (Å) NB–O rLi–O (Å) NLiLiBO2 glass (this study) 1.42 2.75 1.63 0.45 1.98 3.2LiBO2 glass59 1.42 3.00 1.63 0.25 1.98 2.923030 | J. Mater. Chem. A, 2026, 14, 23026–230373.3 Coordination number analyses using diffraction data3.3.1 B2O3 glass. The ternary or quaternary 1/3Li2O–1/3B2O3–1/3LiCl1−xBrx glasses contain structural information on10 or 15 atomic pairs in the X-ray and neutron diffraction data.Prior to the structural analysis of these complicated glasses, weanalyse the diffraction data of B2O3 (ref. 56) and LiBO2 glasses.The B–O, O–O, and B–B coordination numbers in B2O3 glass,obtained using the pair function method based on neutron andX-ray S(Q) and T(r) (Fig. S1), are 3.0, 4.0, and 3.0, respectively.These results are consistent with the reported structure of B2O3glass, in which trigonal planar BO3 units form a network bysharing vertex oxygen atoms.56–583.3.2 LiBO2 glass. Fig. 2(a) shows the X-ray S(Q) for LiBO2glass prepared in this study together with previously reporteddata.59 The LiBO2 glass prepared in this study exhibits severalBragg peaks in S(Q), indicating partial crystallization. In contrast,the behaviour of S(Q) in the higher-Q region (Q > 4.8 Å−1) is similarbetween the two LiBO2 glasses. Compared with the X-ray S(Q) ofB2O3 glass (Fig. S1(a)), the rst sharp diffraction peak (FSDP),a signature of intermediate-range order in the B–O covalentnetwork,56–58 shis to higher Q values and becomes broader inboth LiBO2 glasses, indicating modication of the B–O covalentnetwork upon lithium incorporation. The T(r) functions obtainedfrom the Fourier transform of S(Q) are shown in Fig. 2(b). Inaddition to the B–O, O–O, and B–B correlations observed in B2O3glass (Fig. S1(b)), a Li–O correlation peak appears at approximately2.0 Å. Furthermore, the B–O peak shis to a longer r and becomesasymmetric. The X-ray S(Q) and T(r) were analysed using the pairfunctionmethod (eqn (10)). Two pair functions were used for eachcorrelation to reproduce the asymmetric B–O and Li–O peaks. Thecalculated curves, shown as black broken lines in Fig. 2a and (b),reproduce the experimental S(Q) and T(r) well. The derived struc-tural parameters are summarized in Table 3. The B–O peak in T(r)was reproduced by two B–O pair functions at 1.42 and 1.63 Å. TheB–O coordination numbers were 3.2 (this study) and 3.25 (previousdiffraction data59), indicating the presence of BO4 tetrahedralunits, consistent with previous NMR and Raman spectroscopicstudies.10,50,60 The Li–O correlation peak was also reproduced bytwo pair functions at 1.98 and 2.35 Å, yielding a Li–O coordinationnumber of 4.1. This suggests that lithium cations are tetrahedrallycoordinated by oxygen atoms, with three shorter Li–O bonds at1.98 Å and one longer interaction extending to approximately 2.35Å. This conguration is consistent with a previous NDIS study onLi2O–2SiO2 glass.39 The O–O distance (2.41–2.42 Å) and coordina-tion number (4.4) are slightly larger than those in B2O3 glass (TableS1), reecting the formation of BO4 tetrahedral units. The B–Bdistance also increases slightly to 2.42 Å, suggesting an increase inthe distance between the centres of neighbouring BOx (BO3 orrelations in LiBO2 glasses, derived from X-ray diffraction dataLi–O (II) O–O B–B Li–B–O rLi–O (Å) NLi–O rO–O (Å) NO–O rB–B (Å) NB–B rLi–B (Å) NLi–B2.35 0.9 2.42 4.4 2.42 2.4 2.70 4.02.35 1.2 2.41 4.4 2.42 2.4 2.70 4.0This journal is © The Royal Society of Chemistry 2026http://creativecommons.org/licenses/by/3.0/http://creativecommons.org/licenses/by/3.0/https://doi.org/10.1039/d5ta10123aFig. 3 X-ray and neutron diffraction data of the 1/3Li2O–1/3B2O3–1/3LiCl1−xBrx glasses in Q space. (a) X-ray structure factors, (b) neutronstructure factors of natLi glasses, and (c) neutron structure factors of nullLi glasses. Coloured solid curves represent experimental data, and blackbroken curves in panel (c) represent calculated data.Paper Journal of Materials Chemistry AOpen Access Article. Published on 01 April 2026. Downloaded on 6/17/2026 12:35:29 AM.  This article is licensed under a Creative Commons Attribution 3.0 Unported Licence.View Article OnlineBO4) units upon lithium incorporation. To examine the spatialrelationship between lithium cations and BOx units, a Li–Bcorrelation was included in the pair function analysis. In LiBO2glass, Li2O acts as a networkmodier, converting bridging oxygens(B–O–B) into non-bridging oxygens, with Li+ cations locatednearby to maintain local charge neutrality.61 The oxygen atomsintroduced by Li2O either form BO4 units or exist as non-bridgingoxygens. These oxygens are predominantly coordinated to lithiumcations, giving rise to Li–O–B linkages. The resulting Li–B coor-dination number of approximately 4.0 is consistent with the Li–Ocoordination number (4.1), supporting this structural model.Based on the structural features identied for LiBO2 glass, weproceed to analyse the structure of halide-containing 1/3Li2O–1/3B2O3–1/3LiCl1–xBrx glasses.3.3.3 1/3Li2O–1/3B2O3–1/3LiCl1−xBrx glasses. Fig. 3 showsthe X-ray and neutron total structure factors, S(Q), of the 1/3Li2O–1/3B2O3–1/3LiCl1−xBrx glasses. The neutron S(Q) exhibitsdifferent behaviours between the natLi (Fig. 3(b)) and nullLi(Fig. 3(c)) glasses, owing to the absence of Li-related weightingFig. 4 X-ray and neutron diffraction data of the 1/3Li2O–1/3B2O3–1/3Lneutron total correlation functions of natLi glasses, and (c) neutron totalexperimental data, and black broken curves in panel (c) represent calculThis journal is © The Royal Society of Chemistry 2026factors in the nullLi glasses. The FSDP observed at Q ∼1.6 Å−1,which is prominent in B2O3 glass (Fig. S1(a)), is not clearlyobserved in either the X-ray or neutron S(Q) for the 1/3Li2O–1/3B2O3–1/3LiCl1−xBrx glasses due to the large weighting factorsof chlorine and bromine for both X-rays and neutrons. The X-rayand neutron T(r) functions, obtained from the Fourier trans-forms of S(Q), are shown in Fig. 4. In the X-ray T(r) data(Fig. 4(a)), the B–O and Li–O correlations exhibit small peaks atapproximately 1.4 and 2.0 Å, respectively, in all the glasses. Thepeak observed at approximately 2.4 Å in all the glasses corre-sponds to overlapping O–O and B–B correlations. In the Cl100glass, the Li–Cl correlation contributes to this peak, whereas inthe Br100 glass, the Li–Br correlation appears at approximately2.7 Å (as indicated by the arrow in Fig. 4(a)). In the neutron T(r)for the natLi glasses (Fig. 4(b)), B–O and Li–O peaks are clearlyobserved in all the glasses. The Li–O peak appears as a negativepeak owing to the negative neutron coherent scattering lengthof natLi (b = −1.90 fm).35 Assignment of peaks beyond the B–Oand Li–O correlations is difficult due to the overlap betweeniCl1−xBrx glasses in real space. (a) X-ray total correlation functions, (b)correlation functions of nullLi glasses. Coloured solid curves representated data.J. Mater. Chem. A, 2026, 14, 23026–23037 | 23031http://creativecommons.org/licenses/by/3.0/http://creativecommons.org/licenses/by/3.0/https://doi.org/10.1039/d5ta10123aTable 4 Structural parameters for B–O, O–O, and B–B correlations inthe 1/3Li2O–1/3B2O3–1/3LiCl1–xBrx glasses, derived from neutrondiffraction data of nullLi glassesB–O (I) B–O (II) O–O B–BrB–O (Å) NB–O rB–O (Å) NB–O rO–O (Å) NO–O rB–B (Å) NB–BBr100 1.40 3.0 1.52 0.4 2.41 4.0 2.42 2.4Cl25Br75 1.40 3.0 1.52 0.4 2.41 4.0 2.42 2.4Cl50Br50 1.40 3.0 1.52 0.4 2.41 4.0 2.41 2.4Cl75Br25 1.40 3.0 1.52 0.4 2.41 4.0 2.42 2.4Cl100 1.40 3.0 1.52 0.4 2.41 4.0 2.42 2.4Journal of Materials Chemistry A PaperOpen Access Article. Published on 01 April 2026. Downloaded on 6/17/2026 12:35:29 AM.  This article is licensed under a Creative Commons Attribution 3.0 Unported Licence.View Article Onlinepositive correlations (e.g., O–O, B–B, and halogen–halogenpeaks) and negative correlations (e.g., Li–Cl, Li–Br, and Li–Bpeaks). In contrast, the nullLi glasses (Fig. 4(c)) show the absenceof Li–O peaks, while the B–O peaks remain, demonstrating theeffective elimination of Li-related correlations. The second peakat 2.4 Å can therefore be assigned to overlapping O–O and B–Bcorrelations. Notably, B–Cl and B–Br correlations, expected at1.75 Å in BCl3 (ref. 62) and 1.90 Å in BBr3,63 are not observed,indicating that boron atoms primarily bond with oxygen atoms,and that boron–halogen bonds are rare in these glasses. Theneutron S(Q) and T(r) for the nullLi glasses were further analysedusing the pair function method, with B–O, O–O, and B–Bcorrelations adopted to reproduce the rst and second peaks inT(r). The calculated S(Q) and T(r) (black broken curves inFig. 3(c) and 4(c)) reproduce the experimental data well. Thestructural parameters derived from the pair function analysisare summarized in Table 4. The B–O coordination number is 3.4(3.0 + 0.4) in all the glasses, indicating that the network consistsprimarily of triangular BO3 and tetrahedral BO4 units, consis-tent with the 11B MAS NMR results (Fig. S2 and Table S2). Thestructural parameters for the O–O and B–B correlations areFig. 5 (a) Differential structure factors and (b) differential total correlatisolid curves and black broken curves represent experimental and calcucorrelations are highlighted in red, blue, magenta, and black, respectively,are plotted as cyan curves in panel (b).23032 | J. Mater. Chem. A, 2026, 14, 23026–23037comparable to those in B2O3 (Table S1) and LiBO2 (Table 3)glasses. It should be noted that lithium–halogen correlationsoverlap with other peaks in all the T(r) data, making it difficultto extract precise lithium–halogen coordination numbers.Therefore, although the presence of lithium–halogen correla-tions is suggested, their coordination numbers cannot be reli-ably determined from conventional diffraction measurements.3.4 Lithium-specic coordination number analyses usingNDIS dataTo obtain Li-specic structural information, DLiS(Q) for theCl100, Cl50Br50, and Br100 glasses were analysed (Fig. 5(a)).These data were obtained by taking the difference between theneutron diffraction data of the natLi and nullLi glasses. A nega-tive peak is observed at Q∼2 Å−1 in all the glasses. Majérus et al.reported that a similar negative peak originates from Li-centredintermediate-range ordering in Li2O–2B2O3 glass.40 However, inthe present 1/3Li2O–1/3B2O3–1/3LiCl1−xBrx glasses, the peakappears at a higher Q position and exhibits an asymmetricshape, suggesting the formation of a Li-centred intermediate-range structure with a different characteristic length scale.The differential total correlation functions, DLiT(r), obtainedfrom the Fourier transforms of DLiS(Q) are shown in Fig. 5(b).Three broad peaks arising from Li-related correlations areobserved at approximately 1.8–3.0 Å in all the glasses. The rstpeak at approximately 2.0 Å corresponds to the Li–O correlation,consistent with the negative peak observed in the neutron T(r)data for the natLi glasses (Fig. 4(b)). The second peak atapproximately 2.4 Å is evident in the Cl100 and Cl50Br50 glassesand is mainly attributed to the Li–Cl correlation, in agreementwith the Li–Cl distance (2.45 Å) reported for molten LiCl.64 Inthe Br100 glass, the second peak appears as a shoulder peak atapproximately 2.5–2.7 Å and is assigned to the Li–Br correlation,on functions of the 1/3Li2O–1/3B2O3–1/3LiCl1−xBrx glasses. Colouredlated data, respectively. The calculated Li–O, Li–Cl, Li–Br, and Li–Bin panel (b). The differences between experimental and calculated dataThis journal is © The Royal Society of Chemistry 2026http://creativecommons.org/licenses/by/3.0/http://creativecommons.org/licenses/by/3.0/https://doi.org/10.1039/d5ta10123aTable 5 Structural parameters for Li-related correlations in the 1/3Li2O–1/3B2O3–1/3LiCl1–xBrx glasses, derived from NDIS dataLi–O (I) Li–O (II) Li–Cl Li–Br Li–BrLi–O (Å) NLi–O rLi–O (Å) NLi–O rLi–Cl (Å) NLi–Cl rLi–Br (Å) NLi–Br rLi–B (Å) NLi–BBr100 1.95 2.3 2.36 0.8 — — 2.64 1.9 2.95 3.0Cl50Br50 1.96 2.3 2.33 0.9 2.45 1.1 2.64 1.0 2.91 3.1Cl100 1.96 2.3 2.30 0.8 2.46 1.8 — — 2.85 3.1Paper Journal of Materials Chemistry AOpen Access Article. Published on 01 April 2026. Downloaded on 6/17/2026 12:35:29 AM.  This article is licensed under a Creative Commons Attribution 3.0 Unported Licence.View Article Onlineconsistent with the Li–Br distance (2.68 Å) in molten LiBr.64 Thethird peak mainly originates from the Li–B correlation associ-ated with Li–O–B linkages, as discussed in the X-ray diffractionresults for the LiBO2 glasses.The Li–O, Li–Cl, Li–Br, and Li–B coordination numbers weredetermined by tting calculated DLiS(Q) and DLiT(r) to the exper-imental data using eqn (11). Two Li–O pair functions wereadopted based on the results for the LiBO2 glasses. As shown inFig. 5(a), the calculated DLiS(Q) reproduces the experimental datawell for Q > 2 Å−1, and good agreement between the calculatedand experimental DLiT(r) is also obtained (Fig. 5(b)). The derivedstructural parameters are summarized in Table 5. The Li–Ocoordination number is 3.1–3.2 in all the glasses, indicating thatthe tetrahedral coordination around lithium cations collapses inthe halide-containing glasses. Lithium cations are threefoldcoordinated by oxygen atoms, with two oxygen atoms at approxi-mately 1.95–1.96 Å and one additional oxygen atom at approxi-mately 2.30–2.36 Å, indicating the breaking of one short Li–Obond upon halide addition. The Li–Cl coordination numberdecreases from 1.8 in the Cl100 glass to 1.1 in the Cl50Br50(mixed-halide) glass. Similarly, the Li–Br coordination numberdecreases from 1.9 (Br100) to 1.0 (Cl50Br50). The Li–B coordina-tion number is approximately 3.0 in all the glasses. This behaviouris consistent with the results observed in the LiBO2 glasses, wherethe Li–B coordination number was almost identical to that of Li–Fig. 6 Schematic representations of typical lithium–anion polyhedra and1/3LiCl1−xBrx glasses. (a) LiO4, (b) LiO3Cl2, (c) LiO3ClBr, and (d) LiO3Br2 ppolyhedra in (e) Cl100, (f) Cl50Br50, and (g) Br100 glasses. Green: lithiumThis journal is © The Royal Society of Chemistry 2026O, suggesting the presence of Li–O–B linkages. To further validatethese results, high-energy X-ray diffraction data were analysedbased on the NDIS results using the pair-function analysis (eqn(10)). The calculated X-ray S(Q) and T(r) (Fig. S3(a) and (b))reproduce the experimental data well. The structural parametersfor lithium-related correlations derived from the X-ray diffractiondata (Tables S3 and S4) agree with those obtained from the NDISdata (Table 5). Additionally, the structural parameters for the B–O,O–O, and B–B correlations also agree with those obtained fromthe neutron diffraction data of the nullLi glasses (Table 4). Theseresults demonstrate that reliable coordination numbers in the 1/3Li2O–1/3B2O3–1/3LiCl1–xBrx glasses were obtained through anelement-specic PDF analysis combining NDIS and high-energyX-ray diffraction data.3.5 Origin of the improvement in ionic conductivity bymixing of oxide and halide anionsThe ionic conductivity of the 1/3Li2O–1/3B2O3–1/3LiCl1−xBrxglasses (∼10−6 S cm−1) is approximately one order of magnitudehigher than that of LiBO2 glass (∼10−7 S cm−1).48–50 Thisenhancement is attributed to the mixing of oxide and halideanions. To clarify the lithium environment responsible for thisbehaviour, representative lithium–anion polyhedra in LiBO2and the 1/3Li2O–1/3B2O3–1/3LiCl1−xBrx glasses were visualizedbased on the coordination number analyses (Fig. 6(a–d)).lithium-ion conduction pathways in LiBO2 and the 1/3Li2O–1/3B2O3–olyhedra. Lithium-ion conduction pathways formed by lithium–anion, red: oxygen, blue: chlorine, magenta: bromine.J. Mater. Chem. A, 2026, 14, 23026–23037 | 23033http://creativecommons.org/licenses/by/3.0/http://creativecommons.org/licenses/by/3.0/https://doi.org/10.1039/d5ta10123aJournal of Materials Chemistry A PaperOpen Access Article. Published on 01 April 2026. Downloaded on 6/17/2026 12:35:29 AM.  This article is licensed under a Creative Commons Attribution 3.0 Unported Licence.View Article OnlineIn LiBO2 glasses, lithium cations are tetrahedrally coordi-nated by four oxygen atoms: three at 1.98 Å and one at 2.35 Å(Li–O coordination number is 4.1, Table 3) (Fig. 6(a)). Similartetrahedrally coordinated lithium sites have been reported inbinary oxide39 and sulde22,65 glasses, where asymmetric Li–Oand Li–S correlation peaks indicate distorted tetrahedra. Uponincorporation of halide anions, the Li–O coordination numberdecreases from 4.1 to 3.1–3.2 (Table 5). The number of shorterLi–O bonds (1.95–1.98 Å) decreases from 2.9–3.2 to 2.3, whereasthe longer Li–O bonds (2.30–2.36 Å) remain nearly unchanged(0.8–1.2). Simultaneously, lithium–halogen coordinationnumbers of 1.8, 2.1 (1.1 + 1.0), and 1.9 were obtained for theCl100, Cl50Br50, and Br100 glasses, respectively. These resultsindicate that lithium cations occupy vefold-coordinated sitesin the halide-containing glasses, denoted as LiO3X2 (X= Cl and/or Br) (Fig. 6(b–d)).The LiO3Cl2 (Fig. 6(b)) and LiO3Br2 (Fig. 6(d)) units are char-acteristic of the Cl100 and Br100 glasses, respectively, whereasLiO3ClBr units (Fig. 6(c)) are additionally present in the mixed-halide Cl50Br50 glass. Similar decreases in Li–O coordinationnumber and the formation of Li–Cl bonds with increasing LiClcontent have been reported for (LiCl)x(Li2O–2B2O3)1−x glasses byneutron diffraction with the aid of RMC modelling.66 The changein the lithium coordination environments in ternary and quater-nary glasses has been observed exclusively through simulationstudies; however, the present study directly reveals such changesusing Li-specic PDF analysis with NDIS data. The change inlithium coordination numbers plays a pivotal role in enhancingionic conductivity upon oxide–halide mixing. Incorporation ofhalide anions replaces one short Li–O bond (1.95–1.98 Å) with twolonger Li–halogen bonds (2.45–2.46 Å for Li–Cl; 2.64 Å for Li–Br).According to bond-strength–bond-distance relationships,67,68these longer Li–halogen bonds are weaker than Li–O bonds. Thisis also reected in bond valence calculations, which relate bondstrength to bond length.69,70 For example, when compared incrystalline lithium oxide (Li2O) and halides (LiCl and LiBr), thebond valence decreases from 0.236 for Li2O (Li–Odistance: 2.00 Å)to 0.170 for LiCl (Li–Cl distance: 2.565 Å) and 0.141 for LiBr (Li–Brdistance: 2.745 Å). Similarly, the single bond strengths calculatedfrom the dissociation energies show that Li–Cl (115 kJ mol−1) andLi–Br (104 kJ mol−1)71 are weaker than Li–O (150 kJ mol−1).72Consequently, replacing one short Li–O bond with two longer Li–halogen bonds reduces the local constraints on lithium cations,facilitating lithium-ion migration and enhancing ionic conduc-tivity in the 1/3Li2O–1/3B2O3–1/3LiCl1–xBrx glasses. This interpre-tation is also consistent with the lower melting points of LiCl (605°C) and LiBr (552 °C) compared with Li2O (1570 °C), suggestingthat lithium cations bonded to halogens require less thermalenergy to become mobile than those bonded to oxygens, despiteLiCl or LiBr exhibiting Li–Cl/Br coordination numbers of 6 (higherthan the Li–O coordination number of 4 in Li2O). The speciclithium coordination environments identied in the glasses(Fig. 6(b–d)) are rarely observed in crystalline materials, as therigid glass network can sustain such metastable structuralunits.55,73–75 These unique local structures can provide usefulinsights into the structural design of glasses with high ionicconductivity.23034 | J. Mater. Chem. A, 2026, 14, 23026–230373.6 Cause of the reduction in ionic conductivity uponmixingof halide anionsLithium-ion conduction in glasses occurs through pathwaysformed by interconnected lithium-centred polyhedra.5,14–17,22,23,66Therefore, understanding the connectivity of the lithium–oxygen–halogen polyhedra (Fig. 6(b–d)) is essential for eluci-dating the reduction in ionic conductivity in the 1/3Li2O–1/3B2O3–1/3LiCl1–xBrx glasses caused by halide–halide mixing.Schematic representations of clusters of LiO3X2 units in theCl100, Cl50Br50, and Br100 glasses are shown in Fig. 6(e–g). Inthese gures, the network consisting of BO3 triangles and BO4tetrahedra is omitted. In the Cl100 and Br100 glasses, lithiumcations predominantly occupy LiO3Cl2 (Fig. 6(e)) or LiO3Br2 (Fig.6(g)) polyhedra, forming continuous conduction pathwaysthrough vefold-coordinated sites consisting of three oxide andtwo halide anions. In contrast, the Cl50Br50 glass containsLiO3Cl2, LiO3Br2, and LiO3ClBr units (Fig. 6(f)). The halide-mixed LiO3ClBr polyhedra create an intermediate local envi-ronment with slightly different lithium–halide bond lengthscompared with the LiO3Cl2 and LiO3Br2 units. This structuraldiversity introduces a mismatch in the occupation energies ofthe lithium sites, which disrupts lithium-ionmigration betweendifferent polyhedra. Molecular dynamics simulations of mixedalkali metasilicate glasses have demonstrated that alkali cationsmigrate along independent pathways and that the ionicconduction among the sites occupied by other types of alkalications is restricted by energy mismatches.76,77 Similarly, in theCl50Br50 glass, the variation in lithium coordination environ-ments leads to a partial inhibition of lithium-ion conduction.The mixed-halogen effect observed in this study differs fromthe classical mixed-alkali effect, where conductivity candecrease by several orders of magnitude.53–55 In the Cl50Br50glass, the reduction in conductivity is only about half an orderof magnitude (Fig. 1), because the substituted halide anions donot act as charge carriers (in contrast to the mixed-alkali effect,where the alkali cations functioning as carriers themselves aresubstituted). Therefore, the energy mismatch between lithiumsites in mixed-halide glasses is smaller than that betweendifferent alkali cations in mixed-alkali glasses.Traditionally, the mixed-anion effect has been associatedwith the combination of anions with different valences (e.g.,oxide and halide), which improves ionic conductivity inglasses.7,33,34,51,52 However, this study demonstrates that mixingmonovalent halides can reduce ionic conductivity. Li-specicPDF analysis combining NDIS data enabled the determinationof the lithium-related intermediate-range structure formed byinterconnected LiO3X2 units. This conguration was identiedas the origin of the reduced lithium-ion conductivity in themixed-halide Cl50Br50 glass.Anion mixing has a long history in glass science for tuningmaterial properties, and recent studies have extended thisstrategy to crystalline materials.78 Well-designed crystallinemixed-anion compounds exhibit unique coordination environ-ments within long-range ordered atomic arrangements andenhanced physicochemical properties, such as pure hydride(H−) conduction in La2−x−ySrx+yLiH1−x+yO3−y oxyhydrides,79This journal is © The Royal Society of Chemistry 2026http://creativecommons.org/licenses/by/3.0/http://creativecommons.org/licenses/by/3.0/https://doi.org/10.1039/d5ta10123aPaper Journal of Materials Chemistry AOpen Access Article. Published on 01 April 2026. Downloaded on 6/17/2026 12:35:29 AM.  This article is licensed under a Creative Commons Attribution 3.0 Unported Licence.View Article Onlinecorrelated disorder in SrMO2N (M = Nb, Ta) perovskite oxy-nitrides,80 a signicant spin–orbit interaction effect in bulkBiTeI,81 and exceptionally high lithium-ion conductivity inLi9.54Si1.74P1.44S11.7Cl0.3 solid electrolyte.82 Conversely, inglasses, the compositional and structural exibility allowsdiverse lithium environments to form, as demonstrated in thisstudy. Although designing new glasses with tailored structuresand properties is still challenging, the insights from element-specic quantum-beam analyses, as demonstrated in thisstudy, pave the way for future glass design.4. ConclusionsIn this study, we investigated the lithium-cation environment in1/3Li2O–1/3B2O3–1/3LiCl1−xBrx glasses, which exhibit variationsin ionic conductivity due to anion mixing. We found that oxide–halide mixing enhances ionic conductivity by an order ofmagnitude compared with LiBO2 glass, whereas halide–halidemixing reduces ionic conductivity to nearly half of the valueobserved prior to mixing. Lithium-specic coordinationnumber analysis based on neutron diffraction with isotopicsubstitution for natLi- and nullLi-enriched glasses revealed thatthe conductivity enhancement in oxide–halide mixed glassesarises from the breaking of short lithium–oxygen bonds and theformation of longer lithium–halogen bonds, which weakenconstraints on lithiummobility. In a halide–halide mixed glass,analysis of lithium–anion coordination numbers showed theformation of three distinct vefold lithium–oxygen–halogenpolyhedral units. The coexistence of these units forms a poly-hedral network that hinders lithium-ion migration due tomismatched site occupation energies. These ndings providenew insights into the structure–property relationships oflithium-ion conducting glasses and offer guidance fordesigning glassy electrolytes with improved ionic conductivity.Author contributionsY. O. and Y. T. designed the study. The samples were preparedby H. H. and N. K. Electrical conductivity measurement wasperformed by N. K. The high-energy X-ray diffraction experi-ment was conducted by Y. O., Y. T., and S. K. The neutrondiffraction experiment was conducted by Y. O., Y. T., and K. I.The obtained data were analysed by Y. O., Y. T., H. H., N. K., M.T. and S. K. Y. O. wrote the manuscript with input from all theauthors.Conflicts of interestThe authors declare that they have no conict of interest.Data availabilityThe data that support the ndings of this study are presented inthe paper and the supplementary information (SI) le and areavailable from the corresponding author upon reasonablerequest. Supplementary information is available. See DOI:https://doi.org/10.1039/d5ta10123a.This journal is © The Royal Society of Chemistry 2026AcknowledgementsThis work was partially supported by JSPS Grant-in-Aid forTransformative Research Areas (A) “Hyper-Ordered StructuresScience” [grant numbers 20H05878 (to S. K.) and 20H05881 (toY. O. and S. K.)]. The synchrotron radiation experiments wereperformed at BL04B2 of SPring-8 with the approval of the JapanSynchrotron Radiation Research Institute (JASRI) (Proposalnumber 2019B1233). The neutron experiments at the Materialsand Life Science Facility of J-PARC were performed under a userprogram (Proposal number 2019B0082).References1 T. Minami, Y. Takuma and M. Tanaka, J. Electrochem. Soc.,1977, 124, 1659–1662.2 T. Minami, H. Nambu and M. Tanaka, J. Am. Ceram. Soc.,1977, 60, 467–469.3 Z. Wang, S. Luo, X. Zhang, S. Guo, P. Li and S. Yan, J. Non-Cryst. Solids, 2023, 619, 122581.4 Y. Daiko, A. Sakuda, T. Honma and A. Hayashi, J. Ceram. Soc.Jpn., 2022, 130, 552–557.5 N. Kamaya, K. Honma, Y. 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A, 2026, 14, 23026–23037 | 23037http://creativecommons.org/licenses/by/3.0/http://creativecommons.org/licenses/by/3.0/https://doi.org/10.1039/d5ta10123a Lithium coordination disorder controlling ionic conductivity in mixed-halide borate glasses Lithium coordination disorder controlling ionic conductivity in mixed-halide borate glasses Lithium coordination disorder controlling ionic conductivity in mixed-halide borate glasses Lithium coordination disorder controlling ionic conductivity in mixed-halide borate glasses Lithium coordination disorder controlling ionic conductivity in mixed-halide borate glasses Lithium coordination disorder controlling ionic conductivity in mixed-halide borate glasses Lithium coordination disorder controlling ionic conductivity in mixed-halide borate glasses Lithium coordination disorder controlling ionic conductivity in mixed-halide borate glasses Lithium coordination disorder controlling ionic conductivity in mixed-halide borate glasses Lithium coordination disorder controlling ionic conductivity in mixed-halide borate glasses Lithium coordination disorder controlling ionic conductivity in mixed-halide borate glasses Lithium coordination disorder controlling ionic conductivity in mixed-halide borate glasses Lithium coordination disorder controlling ionic conductivity in mixed-halide borate glasses Lithium coordination disorder controlling ionic conductivity in mixed-halide borate glasses Lithium coordination disorder controlling ionic conductivity in mixed-halide borate glasses Lithium coordination disorder controlling ionic conductivity in mixed-halide borate glasses Lithium coordination disorder controlling ionic conductivity in mixed-halide borate glasses Lithium coordination disorder controlling ionic conductivity in mixed-halide borate glasses Lithium coordination disorder controlling ionic conductivity in mixed-halide borate glasses Lithium coordination disorder controlling ionic conductivity in mixed-halide borate glasses Lithium coordination disorder controlling ionic conductivity in mixed-halide borate glasses Lithium coordination disorder controlling ionic conductivity in mixed-halide borate glasses