Solid-state lithium batteries have attracted significant attention recently due to their superior safety and energy density. Nevertheless, the large interfacial resistance has limited the development of SSLBs. To tackle this problem, a general strategy is to add liquid electrolytes (LE) at the interface to form a solid-liquid hybrid electrolyte. However, the effects and interfacial properties of LE in the solid-liquid hybrid electrolyte have not been well-understood. In this work, we quantitatively add LE at the interface to eliminate the large interfacial resistance and study its interfacial properties. As little as 2 µL of LE at the interface enables a hybrid LiFePO₄/LATP/Li battery to deliver a specific capacity of 125 mA h g⁻¹ at 1 C and 98 mA h g⁻¹ at 4 C. Excess LE has no further contribution to the electrochemical performance. Furthermore, the rigid SSE could suppress the formation of lithium dendrites, especially in the case with a high cathode loading (9.1 mg/cm²), suggesting the feasibility of high energy density SSLBs using Li metal anodes. The interfacial analysis reveals that an interfacial solid-liquid electrolyte interphase (SLEI) was formed at the interface, preventing the reduction of LATP by Li metal, thus ensuring the long-term durability of LATP in LE.

固态锂电池由于其优越的安全性和能量密度，最近引起了广泛的关注。但是，较大的界面阻力限制了SSLB的发展。为了解决该问题，一般的策略是在界面处添加液体电解质（LE）以形成固液混合电解质。然而，对LE在固液混合电解质中的作用和界面性质还没有被很好地理解。在这项工作中，我们定量地在界面处添加LE以消除较大的界面阻力，并研究其界面特性。接口处仅2 µL的LE使混合的LiFePO ₄ / LATP / Li电池在1 C时可提供125 mA h g ^-1和98 mA h g ^-1的比容量在4 C下。过量的LE对电化学性能没有进一步的贡献。此外，刚性SSE可以抑制锂树枝状晶体的形成，特别是在阴极负载较高（9.1 mg / cm ²）的情况下，这表明使用Li金属阳极的高能量密度SSLB的可行性。界面分析表明，在界面处形成了界面固液电解质界面（SLEI），防止了Li金属还原LATP，从而确保了LATP在LE中的长期耐久性。