石榴石型Li6.4La3Zr1.4Ta0.6O12对Si/C负极表面固体电解质中间相的调控机制研究

硅(Si)负极在充放电过程中巨大的体积变化会导致固态电解质中间相(SEI)破裂和硅颗粒粉化, 进而造成容量快速衰减。本研究报道了一种利用Li_6.4La₃Zr_1.4Ta_0.6O₁₂(LLZTO)固体电解质调节Si/C负极表面SEI成分的策略。将LLZTO层均匀地涂覆在商用化聚丙烯(PP)隔膜表面, 不仅提高了电解液对隔膜的润湿性, 均匀化锂离子通量, 并且增大了SEI中无机组分的比例, 从而增强Si/C负极的界面稳定性。得益于上述优势, 使用LLZTO修饰的PP隔膜所组装的锂离子电池表现出更为优异的循环稳定性和倍率性能。Li-Si/C半电池的可逆容量为876 mAh·g^-1, 在0.3C (1C=1.5 A·g^-1)的倍率下, 200次循环的容量保持率为81%; 而LFP-Si/C全电池的比容量为125 mAh·g^-1, 在0.3C (1C=170 mA·g^-1)的倍率下循环100次后容量保持率为91.8%。该工作中LLZTO固体电解质调节了Si/C负极表面SEI成分, 为开发高性能硅基锂离子电池提供了新思路。

Mechanism Study on Garnet-type Li6.4La3Zr1.4Ta0.6O12 Regulating the Solid Electrolyte Interphases of Si/C Anodes

The large volume change of silicon anode leads to rupture of the solid electrolyte interface (SEI) and the pulverization of Si electrode during charge-discharge process, which results in uncontrolled capacity loss. In this work, a strategy to regulate the SEI composition of Si/C anodes utilizing Li_6.4La₃Zr_1.4Ta_0.6O₁₂ (LLZTO) solid electrolyte was proposed. LLZTO layer is uniformly coated on the surface of polypropylene (PP) separator, which not only improves wettability of the electrolyte to the separator, thereby homogenizing the lithium-ion flux, but also increases the proportion of inorganic components in SEI and enhances the interfacial stability of Si/C anodes. As a result, Li batteries using the LLZTO coated PP separator exhibit better cycling stability and rate capability. Li-Si/C half cell exhibits a reversible capacity of 876 mAh·g^-1 with 81% capacity retention for more than 200 cycles at 0.3C (1C= 1.5 A·g^-1), and Si/C-LiFePO₄ (LFP) full cell delivers a capacity of 125 mAh·g^-1 with 91.8% capacity retention after 100 cycles at 0.3C (1C=170 mA·g^-1). This work reveals the mechanism of LLZTO solid electrolytes in regulating the SEI of Si/C anodes and sparks new ideas for developing high-performance silicon-based lithium batteries.