Cathode supported solid lithium batteries enabling high energy density and stable cyclability

Abstract

The development of solid lithium battery accords with the pursuit of advanced battery with high energy density and reliable safety. The requirement of high energy density calls for the light as well as thin solid electrolytes with good contacts with cathodes, while the safety demands the electrochemically stable interfaces between electrolytes and Li-metal anodes. Herein, the light and stable composite electrolytes with hierarchical structures are directly integrated with the interfacially friendly cathodes via layer-by-layer tape casting. Through incorporation of Li6.4La3Zr1.4Ta0.6O12 (LLZTO) superconductors with poly(ethylene oxide) (PEO) matrix layer by layer, the total thickness of composite electrolyte is minimized below 40 μm. In terms of the electrolyte-layer constitution, the conductively oriented side (PEO with 10 wt% LLZTO) is integrated with the composite cathode that is infused with the same 10 wt% LLZTO in PEO enabling the compatible cathode/electrolyte interface. The mechanically oriented side (PEO with 40 wt% LLZTO) faces the Li-metal enabling suppression of dendrite growth. Consequently, the cathode supported LiFePO4/Li cells consisting of the designed electrolytes show the discharge capacity of 129 mAh g−1 at 0.1 C and 30°C, and the stable cycle over 150 times with the capacity retention above 80.6%. Moreover, a high discharge capacity of 118 mAh g−1 is achieved with a high cathode loading of 15.2 mg cm−2 at 0.1 C and 50°C. This work demonstrates a novel strategy to construct cathode supported solid batteries based on the light, stable and interfacially friendly solid-electrolyte layers for high energy density and stable cyclability.