Solvent-free method, Nano LLZO CSEs, Interfacial modulation, Cycling performance, Safety characteristics, Renewable energy sources, TJ807-830, Ecology, QH540-549.5

Solid-state batteries (SSBs) with high safety are promising for the energy fields, but the development has long been limited by machinability and interfacial problems. Hence, self-supporting, flexible Nano LLZO CSEs are prepared with a solvent-free method at 25 °C. The 99.8 wt% contents of Nano LLZO particles enable the Nano LLZO CSEs to maintain good thermal stability while exhibiting a wide electrochemical window of 5.0 V and a high Li+ transfer number of 0.8. The mean modulus reaches 4376 MPa. Benefiting from the interfacial modulation, the Li|Li symmetric batteries based on the Nano LLZO CSEs show benign stability with lithium at the current densities of 0.1 mA cm−2, 0.2 mA cm−2, and 0.5 mA cm−2. In addition, the Li|LiFePO4 (LFP) SSBs achieve favorable cycling performance: the specific capacity reaches 128.1 mAh g−1 at 0.5 C rate, with a capacity retention of about 80% after 600 cycles. In the further tests of the LiNi0.8Co0.1Mn0.1O2 (NCM811) cathodes with higher energy density, the Nano LLZO CSEs also demonstrate good compatibility: the specific capacities of NCM811-based SSBs reach 177.9 mAh g−1 at 0.5 C rate, while the capacity retention is over 96% after 150 cycles. Furthermore, the Li|LFP soft-pack SSBs verify the safety characteristics and the potential for application, which have a desirable prospect.