Patel Vivaan, Dato Michael A, Chakraborty Saheli, Jiang Xi, Chen Min, Moy Matthew, Yu Xiaopeng, Maslyn Jacqueline A, Hu Linhua, Cabana Jordi, Balsara Nitash P
Department of Chemical and Biomolecular Engineering, University of California, Berkeley, Berkeley, CA, United States.
Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, United States.
Front Chem. 2023 Jun 2;11:1199677. doi: 10.3389/fchem.2023.1199677. eCollection 2023.
Solid polymer and perovskite-type ceramic electrolytes have both shown promise in advancing solid-state lithium metal batteries. Despite their favorable interfacial stability against lithium metal, polymer electrolytes face issues due to their low ionic conductivity and poor mechanical strength. Highly conductive and mechanically robust ceramics, on the other hand, cannot physically remain in contact with redox-active particles that expand and contract during charge-discharge cycles unless excessive pressures are used. To overcome the disadvantages of each material, polymer-ceramic composites can be formed; however, depletion interactions will always lead to aggregation of the ceramic particles if a homopolymer above its melting temperature is used. In this study, we incorporate LiLaTiO (LLTO) nanoparticles into a block copolymer, polystyrene--poly (ethylene oxide) (SEO), to develop a polymer-composite electrolyte (SEO-LLTO). TEMs of the same nanoparticles in polyethylene oxide (PEO) show highly aggregated particles whereas a significant fraction of the nanoparticles are dispersed within the PEO-rich lamellae of the SEO-LLTO electrolyte. We use synchrotron hard x-ray microtomography to study the cell failure and interfacial stability of SEO-LLTO in cycled lithium-lithium symmetric cells. Three-dimensional tomograms reveal the formation of large globular lithium structures in the vicinity of the LLTO aggregates. Encasing the SEO-LLTO between layers of SEO to form a "sandwich" electrolyte, we prevent direct contact of LLTO with lithium metal, which allows for the passage of seven-fold higher current densities without signatures of lithium deposition around LLTO. We posit that eliminating particle clustering and direct contact of LLTO and lithium metal through dry processing techniques is crucial to enabling composite electrolytes.
固态聚合物电解质和钙钛矿型陶瓷电解质在推进固态锂金属电池发展方面均展现出了潜力。尽管聚合物电解质与锂金属之间具有良好的界面稳定性，但由于其离子电导率低和机械强度差，仍面临一些问题。另一方面，高导电性且机械性能强劲的陶瓷，除非施加过大压力，否则在充放电循环过程中无法与会膨胀和收缩的氧化还原活性颗粒保持物理接触。为克服每种材料的缺点，可以形成聚合物 - 陶瓷复合材料；然而，如果使用高于其熔点温度的均聚物，耗尽相互作用总会导致陶瓷颗粒聚集。在本研究中，我们将LiLaTiO（LLTO）纳米颗粒掺入嵌段共聚物聚苯乙烯 - 聚（环氧乙烷）（SEO）中，以开发一种聚合物复合电解质（SEO - LLTO）。在聚环氧乙烷（PEO）中相同纳米颗粒的透射电子显微镜图像显示颗粒高度聚集，而在SEO - LLTO电解质富含PEO的片层中，有相当一部分纳米颗粒是分散的。我们使用同步加速器硬X射线显微断层扫描技术来研究循环锂 - 锂对称电池中SEO - LLTO的电池失效和界面稳定性。三维断层扫描图像揭示了在LLTO聚集体附近形成了大的球状锂结构。将SEO - LLTO夹在SEO层之间形成“三明治”电解质，我们防止了LLTO与锂金属直接接触，这使得电流密度能够提高七倍，且在LLTO周围没有锂沉积的迹象。我们认为，通过干法加工技术消除颗粒团聚以及LLTO与锂金属的直接接触对于实现复合电解质至关重要。
