Active interphase in phosphate composite cathode enables stable operation of high capacity all-solid-state Li-metal batteries
In the composite cathode of solid-state Li-metal batteries (SSLMBs), the high interfacial resistance and unstable interphase between the cathode active material and solid electrolyte are two of the main reasons for the low energy density in current SSLMBs. Matching the physical/(electro)chemical properties of the cathode active material and solid electrolyte is vital to obtaining a stable interface/interphase.
Here, we constructed a phosphate-based composite cathode consisting of LiFePO4 (LFP) active material and Li1.3Al0.3Ti1.7(PO4)3 (LATP) solid electrolyte by co-firing technique. With the effort to optimize the synthesizing and sintering process of LATP, highly-conductive LATP is obtained at a low sintering temperature. Consequently, the phosphate-based LFP/LATP interface in composite cathode is stabilized by forming an ion-conductive and redox-active Li3-xFe2-x-yTixAly(PO4)3 (LFTAP) interphase, which significantly improves the energy density of SSLMBs. Benefiting from the densified structure and the formed redox-active LFTAP interphase, the mixed ion- and electron-conductive LFP/LATP composite cathode facilitates the stable operation of bulk-type SSLMBs in different voltage ranges with almost no capacity degradation upon cycling. Particularly, both LFTAP interphase and LATP electrolyte can be activated with that the cell cycled between 4.1 V and 2.2 V achieves a high reversible capacity of 2.8 mAh cm-2.
Small, 2022, 18, 2200266
Published: 27 April 2022