Phase separation enables dual ionic and thermal transport in solid-state cathodes

Abstract

Coupled limitations in ionic and thermal transport remain a central challenge for practical solid-state batteries (SSBs), particularly under fast-charging conditions and with high-mass-loading cathodes. Here we introduce a bicontinuous architecture in composite cathodes, achieved through controlled phase separation between an ionic liquid and a polymer matrix. Phase separation is induced by the solvent-dependent solubility difference between polymer and the ionic liquid complex, generating a bicontinuous network that offers continuous pathways for accelerated Li⁺ transport and efficient thermal dissipation simultaneously. Density functional theory calculations and finite-element simulations reveal that this structure concurrently accelerates lithium-ion transport and facilitates thermal dissipation. This dual enhancement suppresses reaction polarization in thick cathodes, markedly boosting the rate capability of SSBs. A LiNi_0.6Co_0.2Mn_0.2O₂ cathode containing 90 wt% active material with a practical loading of 15 mg cm⁻² delivers a specific capacity of 107.7 mAh g⁻¹ at 5 C and room temperature, over two orders of magnitude higher than conventional homogeneous cathodes. The system further sustains >100 mAh g⁻¹ across an exceptionally wide temperature window, from −10°C (0.7 C) to 100°C (30 C). At an even higher loading of 25 mg cm⁻², the cell achieves an areal capacity of 3.2 mAh cm⁻² at 1 C (4.5 mA cm⁻²). These findings establish a generalizable design principle for multifunctional cathodes that integrate high energy and power density with robust thermal regulation, advancing the development of next-generation SSBs.

Keywords

efficient ion transport / high-loading / phase-separate / solid-state battery / thermal management

References

[1] Zhang S, Li R, Deng T, et al. Oscillatory solvation chemistry for a 500 Wh kg⁻¹ Li-metal pouch cell. Nat Energy. 2024; 9(10): 1285-1296.

[2] Huo H, Chen Y, Li R, et al. Design of a mixed conductive garnet/Li interface for dendrite-free solid lithium metal batteries. Energ Environ Sci. 2020; 13(1): 127-134.

[3] Bates AM, Preger Y, Torres-Castro L, Harrison KL, Harris SJ, Hewson J. Are solid-state batteries safer than lithium-ion batteries? Joule. 2022; 6(4): 742-755.

[4] Peng P, Zhou J, Liang L, et al. Regulating thermogalvanic effect and mechanical robustness via redox ions for flexible quasi-solid-state thermocells. Nano Micro Lett. 2022; 14(1): 81.

[5] Kim C, Li Y, Jang I, et al. Pushing the limits: maximizing energy density in silicon sulfide solid-state batteries. Adv Mater. 2025; 37:2502300.

[6] Luo Y, Chen Y, Koratkar N, Liu W. Densification of alloying anodes for high energy lithium-ion batteries: critical perspective on inter-versus intra-particle porosity. Adv Sci. 2024; 11(34):2403530.

[7] Fu Y, Singh RK, Feng S, et al. Understanding of low-porosity sulfur electrode for high-energy lithium-sulfur batteries. Adv Energy Mater. 2023; 13(13):2203386.

[8] Zhang M, Zhou K, Ma D, et al. Constructing the high-areal-capacity, solid-state Li polymer battery via the multiscale ion transport pathway design. Mater Today. 2022; 56: 53-65.

[9] Gan L, Xu X, Yu X, Li H. Assessing the thermal runaway characteristics of solid-state lithium batteries based on thermochemical reaction properties at material level. Energy Storage Mater. 2025; 78:104223.

[10] Tomaszewska A, Chu Z, Feng X, et al. Lithium-ion battery fast charging: a review. eTransportation. 2019; 1:100011.

[11] Zhou K, Lu S, Mish C, et al. Tailored cathode composite microstructure enables long cycle life at low pressure for all-solid-state batteries. ACS Energy Lett. 2025; 10(2): 966-974.

[12] Chen Y-H, Lennartz P, Liu KL, et al. Towards all-solid-state polymer batteries: going beyond PEO with hybrid concepts. Adv Funct Mater. 2023; 33(32):2300501.

[13] Kunz A, Berg C, Friedrich F, Gasteiger HA, Jossen A. Time-resolved electrochemical heat flow calorimetry for the analysis of highly dynamic processes in lithium-ion batteries. J Electrochem Soc. 2022; 169(8):080513.

[14] Wu F, Chen Z, Fang S, Zuo W, Kim GT, Passerini S. The role of ionic liquids in resolving the interfacial chemistry for (quasi-) solid-state batteries. Energy Storage Mater. 2023; 63:103062.

[15] Zhang Y, Huang J, Liu H, et al. Lamellar ionic liquid composite electrolyte for wide-temperature solid-state lithium-metal battery. Adv Energy Mater. 2023; 13(23):2300156.

[16] Jeng M-S, Yang R, Song D, Chen G. Modeling the thermal conductivity and phonon transport in nanoparticle composites using monte carlo simulation. J Heat Transfer. 2008; 130(4):042410.

[17] Chen X, Put B, Sagara A, et al. Silica gel solid nanocomposite electrolytes with interfacial conductivity promotion exceeding the bulk Li-ion conductivity of the ionic liquid electrolyte filler. Sci Adv. 2020; 6(2):eaav3400.

[18] MacFarlane DR, Tachikawa N, Forsyth M, et al. Energy applications of ionic liquids. Energ Environ Sci. 2014; 7(1): 232-250.

[19] Ding Y, Zhang J, Chang L, Zhang X, Liu H, Jiang L. Preparation of high-performance ionogels with excellent transparency, good mechanical strength, and high conductivity. Adv Mater. 2017; 29(47):1704253.

[20] Arya RK, Gupta AK. The effect of nitrogen-rich ionic liquid EMIMDCA on the electronic structure of solid polymer electrolyte (PEO-LiTFSI). J Mol Model. 2022; 28(11): 363.

[21] Bertrand M, Johnson NB, Jin L, et al. Unveiling the thermite-driven lithium fire ignition in solid-state batteries. Joule. 2025; 9(5):101953.

[22] Ketter L, Greb N, Bernges T, Zeier WG. Using resistor network models to predict the transport properties of solid-state battery composites. Nat Commun. 2025; 16(1): 1411.

[23] Shi X, Jia Z, Wang D, et al. Phonon engineering in solid polymer electrolyte toward high safety for solid-state lithium batteries. Adv Mater. 2024; 36(33):2405097.

[24] Ye G, Hong X, He M, et al. All-solid-state lithium metal batteries with microdomain-regulated polycationic solid electrolytes. Adv Mater. 2025; 37(12):2417829.

[25] Chattoraj J, Diddens D, Heuer A. Effects of ionic liquids on cation dynamics in amorphous polyethylene oxide electrolytes. J Chem Phys. 2014; 140(2):024906.

[26] Zhong T, Liu W, Liu H. Green electrospinning of chitin propionate to manufacture nanofiber mats. Carbohydr Polym. 2021; 273:118593.

[27] Liu X, Ji X, Zhu R, et al. A microphase-separated design toward an all-round ionic hydrogel with discriminable and anti-disturbance multisensory functions. Adv Mater. 2024; 36(15):2309508.

[28] Zhao W, Zheng Y, Huang A, et al. Metal-halogen interactions inducing phase separation for self-healing and tough ionogels with tunable thermoelectric performance. Adv Mater. 2024; 36(30):2402386.

[29] Dieter KM, Dymek CJ, Heimer NE, Rovang JW, Wilkes JS. Ionic structure and interactions in 1-methyl-3-ethylimidazolium chloride-aluminum chloride molten salts. J Am Chem Soc. 1988; 110(9): 2722-2726.

[30] Fu F, Zheng Y, Jiang N, et al. A dual-salt PEO-based polymer electrolyte with cross-linked polymer network for high-voltage lithium metal batteries. Chem Eng J. 2022; 450:137776.

[31] Takechi K, Kato Y, Hase Y. A highly concentrated catholyte based on a solvate ionic liquid for rechargeable flow batteries. Adv Mater. 2015; 27(15): 2501-2506.

[32] Wen SJ, Richardson TJ, Ghantous DI, et al. FTIR characterization of PEO+LiN(CF₃SO₂)₂ electrolytes. J Electroanal Chem. 1996; 408(1): 113-118.

[33] Cheng Q, Xu W, Qin S, et al. Full dissolution of the whole lithium sulfide family (Li₂S₈ to Li₂S) in a safe eutectic solvent for rechargeable lithium-sulfur batteries. Angew Chem Int ed. 2019; 58(17): 5557-5561.

[34] Li P, Yang S, Zhu J, et al. Achieving high-concentration Cl⁻ ions in non-aqueous electrolytes for high-energy-density Li-Cl₂ batteries. Matter. 2024; 7(5): 1867-1878.

[35] Wan J, Xie J, Kong X, et al. Ultrathin, flexible, solid polymer composite electrolyte enabled with aligned nanoporous host for lithium batteries. Nat Nanotechnol. 2019; 14(7): 705-711.

[36] Weng S, Zhang X, Yang G, et al. Temperature-dependent interphase formation and Li⁺ transport in lithium metal batteries. Nat Commun. 2023; 14(1): 4474.

[37] Zhao Y, Li L, Zhou D, et al. Opening and constructing stable lithium-ion channels within polymer electrolytes. Angew Chem Int ed. 2024; 63(31):e202404728.

[38] Cui H, Gao X, Guo K, et al. Lewis acid-base synergistically enhancing practical composite electrolyte for fluoride-ion batteries at room temperature. Adv Sci. 2025; 12(27):2502824.

[39] Liu Y-N, Xiao Z, Zhang W-K, et al. Poly(m-phenylene isophthalamide)-reinforced polyethylene oxide composite electrolyte with high mechanical strength and thermostability for all-solid-state lithium metal batteries. Rare Met. 2022; 41(11): 3762-3773.

[40] Zhao X, Wang C, Fan X, et al. Addressing the interface issues of all-solid-state lithium batteries by ultra-thin composite solid-state electrolyte combined with the integrated preparation technology. InfoMat. 2025; 7(8):e70012.

[41] Zheng H, Lv Y, Sun Q, et al. Thermodynamic evidence for cluster ordering in Cu₄₆Zr₄₂Al₇Y₅ ribbons during glass transition. Sci Bull. 2016; 61(9): 706-713.

[42] Wang Z, Yang L, Xu C, et al. Advances in reactive co-precipitation technology for preparing high-performance cathodes. Green Carbon. 2023; 1(2): 193-209.

[43] Zhou L, Zhang Z, Sangroniz A, et al. Chain-end controlled depolymerization selectivity in α,α-disubstituted propionate PHAs with dual closed-loop recycling and record-high melting temperature. J Am Chem Soc. 2024; 146(43): 29895-29904.

[44] Xu X, Chen J, Zhou J, et al. Thermal cnductivity of plymers and their nanocomposites. Adv Mater. 2018; 30(17):1705544.

[45] Li J, Hu H, Zhu J, et al. Solid polymer electrolyte with compatible cathode-electrolyte interfacial design enabling lithium metal batteries operation at 4.8 V with long cycle life. Adv Mater. 2025; 37(19):2501659.

[46] Gong Y, Wang C, Xin M, et al. Ultra-thin and high-voltage-stable Bi-phasic solid polymer electrolytes for high-energy-density Li metal batteries. Nano Energy. 2024; 119:109054.

[47] Lee K, Shang Y, Bobrin VA, et al. 3D printing nanostructured solid polymer electrolytes with high modulus and conductivity. Adv Mater. 2022; 34(42):2204816.

[48] Lockett V, Sedev R, Ralston J, Horne M, Rodopoulos T. Differential capacitance of the electrical double layer in imidazolium-based ionic liquids: influence of potential, cation size, and temperature. J Phys Chem C. 2008; 112(19): 7486-7495.

[49] Cheng G, Sun H, Wang H, et al. Efficient ion percolating network for high-performance all-solid-state cathodes. Adv Mater. 2024; 36(21):2312927.

[50] Ren X, Pickup PG. An impedance study of electron transport and electron transfer in composite polypyrrole+polystyrenesulphonate films. J Electroanal Chem. 1997; 420(1): 251-257.

[51] Siroma Z, Sato T, Takeuchi T, Nagai R, Ota A, Ioroi T. AC impedance analysis of ionic and electronic conductivities in electrode mixture layers for an all-solid-state lithium-ion battery. J Power Sources. 2016; 316: 215-223.

[52] Rana M, Rudel Y, Heuer P, et al. Toward achieving high areal capacity in silicon-based solid-state battery anodes: what influences the rate-performance? ACS Energy Lett. 2023; 8(7): 3196-3203.

[53] Yang K, Chen L, Ma J, et al. Stable interface chemistry and multiple ion transport of composite electrolyte contribute to ultra-long cycling solid-state LiNi_0.8Co_0.1Mn_0.1O₂/lithium metal batteries. Angew Chem Int Ed. 2021; 60(46): 24668-24675.

[54] Sun S, Zhao C-Z, Yuan H, et al. Eliminating interfacial O-involving degradation in Li-rich Mn-based cathodes for all-solid-state lithium batteries. Sci Adv. 2022; 8(47):eadd5189.

[55] Li C, Lin Y, Liu J, et al. Liquid-phase preparation of low-tortuosity composite cathode for high active material content all-solid-state lithium batteries. Adv Energy Mater. 2024; 14(31):2400985.

[56] Yuan L, Peng W, Zhan Z, et al. Enhancing ionic transport at primary interparticle boundaries of polycrystalline lithium-rich oxide in all-solid-state batteries. Angew Chem Int ed. 2025; 64(46):e202508605.

[57] Li D, Li Y, Liu H, et al. Constructing uniform ionic conductor coatings on LiCoO₂ cathode to realize 4.6 V high-voltage all-solid-state lithium batteries. Interdiscip Mater. 2025; 4(5): 775-785.

[58] Hao S, Yang J, Li Y, Liu S, Jiang S, He Z. Utilizing oxygen-vacancy-rich violet tungsten oxide enabling ultralong cycling of nickel-rich cathodes at high voltage. ACS Nano. 2025; 19(7): 7263-7272.

[59] Hu Q, Gao K, Wang R, et al. Revealing cycling rate-dependent capacity decay in LiNi_0.6Co_0.2Mn_0.2O₂ at 4.6 V. Energy Storage Mater. 2025; 77:104187.

[60] Hu Q, Wu Y, Ren D, et al. Revisiting the initial irreversible capacity loss of LiNi_0.6Co_0.2Mn_0.2O₂ cathode material batteries. Energy Storage Mater. 2022; 50: 373-379.

[61] Fu C, Zhang X, Huo H, et al. Regulating micro-phase structure in plastic crystal gel polymer electrolyte for quasi-solid-state lithium metal batteries. Adv Funct Mater. 2024; 34(9):2312187.

[62] Liu Y, Zou H, Huang Z, et al. In situ polymerization of 1,3-dioxane as a highly compatible polymer electrolyte to enable the stable operation of 4.5 V Li-metal batteries. Energ Environ Sci. 2023; 16(12): 6110-6119.

[63] Huo S, Sheng L, Xue W, et al. Challenges of polymer electrolyte with wide electrochemical window for high energy solid-state lithium batteries. InfoMat. 2023; 5(3):e12394.

[64] Bai C, Li Y, Xiao G, et al. Understanding the electrochemical window of solid-state electrolyte in full battery application. Chem Rev. 2025; 125(14): 6541-6608.

[65] Kong Z, Wu Y, Wu J-F, et al. Balanced anion-cation-EO interaction enables ultrahigh lithium-ion transport in 4.5 V-class PEO-based all-solid-state lithium batteries. Adv Mater. 2026; 38(5):e14236.

[66] Kong Z-X, Xiong Z, Wu J-F, et al. Suppressing ionic-to-electronic conduction transition on cathode interface enables 4.4 V poly(ethylene oxide)-based all-solid-state batteries. ACS Energy Lett. 2025; 10(1): 287-295.

[67] Wang T, Chen B, Li T, Liu C, Liu X. Constructing stable high-energy polymer-based all-solid-state lithium battery at room temperature through breaking multi-electron transfer barriers. Energy Storage Mater. 2025; 82:104595.

[68] Li Z, Yu R, Weng S, Zhang Q, Wang X, Guo X. Tailoring polymer electrolyte ionic conductivity for production of low-temperature operating quasi-all-solid-state lithium metal batteries. Nat Commun. 2023; 14(1):482.

[69] Liu S, Zhou L, Han J, et al. Super long-cycling all-solid-state battery with thin Li₆PS₅Cl-based electrolyte. Adv Energy Mater. 2022; 12(25):2200660.

[70] Wang Y, Liu K, Xiao H, et al. Delicate design of lithium-ion bridges in hybrid solid electrolyte for wide-temperature adaptive solid-state lithium metal batteries. InfoMat. 2026; 8(3):e70095.

[71] Mu Y, Yu S, Chen Y, et al. Highly efficient aligned ion-conducting network and interface chemistries for depolarized all-solid-state lithium metal batteries. Nano Micro Lett. 2024; 16(1): 86.

[72] Liu Y, An X, Yang K, et al. Achieving a high loading of cathode in PVDF-based solid-state battery. Energ Environ Sci. 2024; 17(1): 344-353.

[73] Su Y, Liu X, Yan H, et al. Assembly of an elastic & sticky interfacial layer for sulfide-based all-solid-state batteries. Nano Energy. 2023; 113:108572.

[74] Dong X, Mayer A, Liu X, et al. Single-ion conducting multi-block copolymer electrolyte for lithium-metal batteries with high mass loading NCM811 cathodes. ACS Energy Lett. 2023; 8(2): 1114-1121.

[75] Ye S, Zhang Y, Huang Y, et al. Regulating ion transport through direct coordination in composite gel polymer electrolytes toward high-voltage and high-loading quasi-solid-state lithium metal batteries. Angew Chem Int ed. 2025; 64(28):e202506662.

[76] Xiao Z, Liu X, Hai F, et al. Wide temperature 500 Wh kg⁻¹ lithium metal pouch cells. Angew Chem Int Ed. 2025; 64(29):e202503693.

[77] Doerrer C, Gao X, Bu J, et al. Fast-charging all-solid-state battery cathodes with long cycle life. Nano Energy. 2025; 134:110531.

[78] An X, Liu Y, Yang K, et al. Dielectric filler-induced hybrid interphase enabling robust solid-state Li metal batteries at high areal capacity. Adv Mater. 2024; 36(13):2311195.

[79] An H, Liu Q, Deng B, et al. Eliminating local electrolyte failure induced by asynchronous reaction for high-loading and long-lifespan all-solid-state batteries. Adv Funct Mater. 2023; 33(45):2305186.

[80] Ge S, Sasaki T, Gupta N, et al. Quantification of lithium battery fires in internal short circuit. ACS Energy Lett. 2024; 9(12): 5747-5755.

[81] Wang C-j, Zhu Y-l, Gao F, et al. Internal short circuit and thermal runaway evolution mechanism of fresh and retired lithium-ion batteries with LiFePO₄ cathode during overcharge. Appl Energy. 2022; 328:120224.

[82] Guo Y, Wu S, He Y-B, et al. Solid-state lithium batteries: safety and prospects. eScience. 2022; 2(2): 138-163.

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