Dual-layer hybrid solid electrolyte for improved interfacial stability in solid-state lithium batteries

Hybrid solid electrolytes (HSEs), which combine the advantages of polymers and ceramics, offer great potential for use in high-performance solid-state lithium batteries (SSLBs) owing to their high ionic conductivities and excellent interfacial compatibilities. However, single-layer electrolytes often suffer from performance degradation caused by interfacial incompatibility with electrodes. In this work, we design a dual-layer structured electrolyte that simultaneously satisfies the distinct interfacial requirements of both the cathode and lithium metal anode, thereby significantly enhancing the electrochemical performance. Li₁.₃Al₀.₃Ti₁.₇(PO₄)₃ (LATP) was doped with 0.075 mol of Zr to improve Li⁺ diffusion kinetics, and the resulting LAZTP dual HSE exhibited a high ionic conductivity of 5.0 × 10^-4 S cm^-1, as well as improved mechanical properties with a tensile strength of 6.32 MPa and Young's modulus of 30.9 MPa-both superior to those of the single-layer electrolyte. The dual-layer architecture also enabled stable Li plating/stripping behavior for 500 h at 0.2 mA cm^-2. When applied to LiFePO₄ (LFP)/LAZTP dual HSE/Li SSLBs, the dual-layer electrolyte delivered a discharge capacity of 155.7 mAh g^-1 at 0.5C, an excellent capacity retention of 92.6% after 200 cycles, and an average Coulombic efficiency of 99.4%.