Braided Fiber Current Collectors for High‐Energy‐Density Fiber Lithium‐Ion Batteries

Fiber lithium‐ion batteries represent a promising power strategy for the rising wearable electronics. However, most fiber current collectors are solid with vastly increased weights of inactive materials and sluggish charge transport, thus resulting in low energy densities which have hindered the development of fiber lithium‐ion batteries in the past decade. Here, a braided fiber current collector with multiple channels was prepared by multi‐axial winding method to not only increase the mass fraction of active materials, but also to promote ion transport along fiber electrodes. In comparison to typical solid copper wires, the braided fiber current collector hosted 139 % graphite with only 1/3 mass. The fiber graphite anode with braided current collector delivered high specific capacity of 170 mAh g−1 based on the overall electrode weight, which was 2 times higher than that of its counterpart solid copper wire. The resulting fiber battery showed high energy density of 62 Wh kg−1. A multi‐channel fiber current collector with both high electrical conductivity and loading content of active materials has been designed to produce fiber lithium‐ion batteries with high energy densities.