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

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.

UV-Permeable 3D Li Anodes for In Situ Fabrication of Interface-Gapless Flexible Solid-State Lithium Metal Batteries.

Flexible solid-state lithium metal batteries (SSLMBs) are highly desirable for future wearable electronics because of their high energy density and safety. However, flexible SSLMBs face serious challenges not only in regulating the Li plating/stripping behaviors but also in enabling the mechanical flexibility of the cell. Both challenges are largely associated with the interfacial gaps between the solid electrolytes and the electrodes. Here, a UV-permeable and flexible composited Li metal anode (UVp-Li), which possesses a unique light-penetrating interwoven structure similar to textiles is reported. UVp-Li allows one-step bonding of the cathode, anode, and solid electrolyte via an in situ UV-initiated polymerization method to achieve the gapless SSLMBs. The gapless structure not only effectively stabilizes the plating/stripping of Li metal during cycling, but also ensures the integrity of the cell during mechanical bending. UVp-Li symmetric cell presents a stable cycling over 1000 h at 0.5 mA cm-2. LiFePO4||UVp-Li full cells (areal capacity ranging from 0.5 to 3 mAh cm-2) show outstanding capacity retention of over 84% after 500 charge/discharge cycles at room temperature. Large pouch cells using high-loading cathodes maintain stable electrochemical performance during 1000 times of dynamic bending.