Study on electrochemical properties of sandwich-structured solid electrolyte for an all-solid-state Li battery

In this study, a novel sandwich-structured solid electrolyte (SSE) comprising Li0.37Sr0.44Zr0.25Ta0.75O3 (LSZT) perovskite-type electrolyte and a composite solid polymer electrolyte (CSPE) was investigated. The thin CSPE interlayer effectively reduces interfacial resistance between LSZT and electrodes while preventing‌ Li-induced reduction of LSZT. The SSE demonstrates an ionic conductivity of 8.76 × 10−5 S·cm−1 at 30 oC, increasing to 1.13 × 10−3 S·cm−1 at 100 oC, with an activation energy of 0.36 eV. In addition, SSE is stable for Li metal and achieves electrochemical stability up to 4.60 V (vs. Li+/Li). SSE shows outstanding electrode/electrolyte interfacial compatibility, and significant suppression of the growth of Li dendrite. Ascribing to these merits, Li| SSE| Li symmetric cell maintained stable operation for 500 h at a current density of 0.3 mA·cm−2 without short circuit, confirming robust interfacial compatibility between SSE and Li electrode. The all-solid-state LiFePO4| Li battery with SSE has an initial reversible discharge capacity of 109.8 mAh·g−1, and a reversible capacity of 118.1 mAh·g−1 after 50 cycles at a charge/discharge rate of 0.1 C (30 oC), demonstrating good cycling performance.