Metal‐Free Polymer‐Based Current Collector for High Energy Density Lithium‐Metal Batteries

The energy density of lithium‐metal batteries (LMBs) relies substantially on the thickness of the lithium‐metal anode. However, a bare, thin lithium foil electrode is vulnerable to fragmentation due to the inhomogeneity of the lithium stripping/plating process, disrupting the electron conduction pathway along the electrode. Accordingly, the current collector is an integral part to prevent the resulting loss of electronic conductivity. However, the common use of a heavy and lithiophobic Cu current collector results in a great anode mass increase and unsatisfactory lithium plating behavior, limiting both the achievable specific energy and the cycle life of LMBs. Herein, a metal‐free polymer‐based current collector is reported that allows for a substantial mass reduction, while simultaneously extending the cycle life of the lithium‐metal anode. The specific mass of the ultra‐light, 10 µm thick polymer‐based current collector is only 1.03 mg cm−2, which is ≈11% of a 10 µm thick copper foil (8.96 mg cm−2). As a result, LMB cells employing this novel current collector provide a specific energy of 448 Wh kg−1, which is almost 18% higher than that of LMBs using the copper current collector (378 Wh kg−1), and a greatly enhanced cycle life owing to a more homogeneous lithium deposition. Metal‐free polyethylene/carbon black composite current collectors provide a cost‐efficient and low‐mass alternative to classic metal foil current collectors for lithium‐metal electrodes, enabling more homogeneous lithium deposition, superior cycle life, and an energy density increase by >18%.