LiF involved interphase layer enabling thousand cycles of LAGP-based solid-state Li metal batteries with 80% capacity retention

The interface compatibility lies in the heart of present investigations on solid-state batteries, now facing significant challenges in practical use. The non-coherent interface structure with the underlying complex electrochemical processes evolves dynamically to pregnant the unfriend seeds to degrade the battery performance. Therefore, interface engineering (or control) in solid-state batteries gives birth to a new theme as ‘the interface is equal to the battery’. In this context, a facile but robust technique is proposed here by smoothing the Li1.5Al0.5Ge1.5P3O12 (LAGP) ceramic pellet with a mirror-like surface, which is found operational in running a solid battery in unprecedentedly a thousand cycles with capacity retention of 80% at 0.5C, 50 °C. Such an unconventional operation is, as a matter of fact, largely decreasing the physically interface contact but proved powerful in guiding the Li-ion homogeneous deposition. Moreover, the self-generated LiF involved interphase layer works efficiently to dynamically balance structural and electrochemical stabilities, where the LiF is introduced by the in-situ polymerization of tiny liquid electrolytes. Hence, the profound results draw the incompatible interface issues forth to the component adjustment of interphases, namely in search for rational descriptions to connect the solid-state electrolyte and electrodes, which probably holds the key to unlocking the high energy density solid-state batteries.