Bipolar Textile Composite Electrodes Enabling Flexible Tandem Solid‐State Lithium Metal Batteries

Abstract A majority of flexible and wearable electronics require high operational voltage that is conventionally achieved by serial connection of battery unit cells using external wires. However, this inevitably decreases the energy density of the battery module and may cause additional safety hazards. Herein, a bipolar textile composite electrode (BTCE) that enables internal tandem‐stacking configuration to yield high‐voltage (6 to 12 V class) solid‐state lithium metal batteries (SSLMBs) is reported. BTCE is comprised of a nickel‐coated poly(ethylene terephthalate) fabric (NiPET) core layer, a cathode coated on one side of the NiPET, and a Li metal anode coated on the other side of the NiPET. Stacking BTCEs with solid‐state electrolytes alternatively leads to the extension of output voltage and decreased usage of inert package materials, which in turn significantly boosts the energy density of the battery. More importantly, the BTCE‐based SSLMB possesses remarkable capacity retention per cycle of over 99.98% over cycling. The composite structure of BTCE also enables outstanding flexibility; the battery keeps stable charge/discharge characteristics over thousands of bending and folding. BTCE shows great promise for future safe, high‐energy‐density, and flexible SSLMBs for a wide range of flexible and wearable electronics.