Overcoming the trade-off between ion conduction and stability using thin composite solid electrolyte for high performance all-solid-state lithium battery

Inorganic superionic conductors hold great promise for all-solid-state lithium batteries because of their superior ionic conductivity. However, their application as electrolytes is limited by the trade-off between ion conduction and stability. Here, a thin composite solid electrolyte, vermiculite-Li0.33La0.557TiO3/poly(ethylene oxide) (Vr-LLTO/PEO), is prepared by in-situ co-sintering an interconnected Vr-LLTO framework and then impregnating PEO. Within this electrolyte, the continuous LLTO on Vr nanosheet surface acts as efficient pathways for vertical Li+ transfer with reduced grain boundary resistance. Together with the thin thickness (35 μm), Vr-LLTO/PEO electrolyte attains the ionic conductivity as high as 1.04 × 10−4 S cm−1 at 25 °C, over three times that of LLTO pellet and surpassing that of most reported ceramic electrolytes. Furthermore, the disordered stacked Vr nanosheets in framework are covalently linked by LLTO, together with the flexible PEO matrix, achieving highly enhanced structural stability with compressive strength of 319 MPa. In this manner, the trade-off between ion conduction and stability is overcome, which allows the assembled LiFePO4/Li cell achieving satisfactory cycling performances: an initial discharge capacity of 150.3 mAh g − 1 at 1 C and capacity decay of only 0.08% per cycle after 200 cycles. This study may inspire insights into the subtle design of conductive and stable electrolytes for high-performance devices.