Asymmetrical interface modification between electrodes and garnet-type electrolyte enabling all-solid-state lithium batteries

Garnet-based all-solid-state lithium batteries are expected to achieve high energy density and safety. However, the distinctly different chemical and electrochemical environment between the electrodes and garnet-type Li6·4La3Zr1·6Ta0·4O12 (LLZTO) electrolyte results in high interfacial impedance that greatly hinders the electrochemical performance. Herein, we propose an asymmetrical interface modification strategy by respectively introducing an ultrathin in-situ polymerized interlayer on the cathode side and a lithiophilic liquid metal coating layer on the Li metal anode side. As a result, the interfacial impedance on both side is significantly reduced to 214 Ω cm2 on the cathode side and 7.45 Ω cm2 on the Li metal anode side due to the intimate contact and enhanced wettability between Li metal and GSSE together with improved conformability on the cathode side and Li ion conductance within the cathode. Therefore, the interface modified LiFePO4||LLZTO||Li all-solid-state battery exhibits excellent cycling performance over 150 cycles with capacity retention of 96.7% and small voltage polarization of 55 mV at 0.1C and 60 °C. This work provides a convenient strategy to alleviate the interfacial issues in all-solid-state batteries. •Asymmetrical modification layers are introduced between electrolyte and electrodes.•Low impedance of 213.9 Ω cm2 is achieved with in-situ polymerized interlayer.•Impedance of 7.45 Ω cm2 on anode side is realized with liquid metal coating layer.•LFP.||SPE@LLZTO@LM||Li battery has capacity retention of 96.7% after 150 cycles.•The battery also shows a small voltage polarization of 55 mV at 0.1C and 60 °C.