Chemical Compatibility of Li1.3Al0.3Ti1.7(PO4)3 Solid-State Electrolyte Co-Sintered with Li4Ti5O12 Anode for Multilayer Ceramic Lithium Batteries

Multilayer ceramic lithium batteries (MLCBs) are regarded as a new type of oxide-based all-solid-state microbattery for integrated circuits and various wearable devices. The chemical compatibility between the solid electrolyte and electrode active materials during the high-temperature co-sintering process is crucial for determining the structural stability and cycling performance of MLCBs. This study focuses on the typical MLCB composite electrodes composed of the NASICON-type Li_1.3Al_0.3Ti_1.7(PO₄)₃ (LATP) solid electrolyte and the spinel-type Li₄Ti₅O₁₂ (LTO) anode material. The thermal behavior, phase structure, morphological evolution, and elemental chemical states of these composite electrodes were systematically investigated over a co-sintering temperature range of 400-900 °C. The results indicate that the reactivity between LATP and LTO during co-sintering is primarily driven by the diffusion of Li from the LTO anode, leading to the formation of TiO₂, Li₃PO₄, and LiTiOPO₄. Furthermore, the co-sintered LATP-LTO multilayer composites reveal that the generation of Li₃PO₄ at the LATP/LTO interface facilitates their co-sintering integration at 800-900 °C, which is essential for the successful fabrication of MLCBs. These findings provide direct evidence and valuable references for the structural and performance optimization of MLCBs in the future.