Nanofluid wetting of Cu enables thin lithium negative electrodes for high-energy and long-cycling lithium metal batteries

Exploiting thin Li foils ≤ 20 μm is required for high-energy-density and long-cycling-lifespan battery, but is severely hindered by the poor processability of Li, as well as its inhomogeneous plating behaviors and resulting low Coulombic efficiency. Herein, an approach balancing Li supply and consumption is fulfilled by designing thin molten-salt-derived, nanocomposite Li@LiX metal negative electrodes. Benefitting from the formation of nanofluid due to the spontaneous reaction of inorganic nanoparticles in molten Li, the bonding states at both Li surface and Li|Cu interface are effectively regulated, displaying an enhanced wetting behaviour of Li on Cu. This approach enables the fabrication of an 800-nm-thick Li-based negative electrode foil as well as the formation of an inorganic-rich interphase upon cycling, which suppresses Li consumption by reducing corrosion susceptibility. As a result, practical pouch cells composed of 10-μm-thick Li@lithium bis(fluorosulfonyl)imide (LiFSI) and LiFePO 4 offer stable cycling over 250 cycles, while those composed of 20-μm-thick Li@LiFSI and LiNi 0.92 Co 0.03 Mn 0.05 O 2 with an areal capacity of 4.6 mAh cm −2 achieve 100 cycles, yielding specific energy of 498 Wh kg −1 and energy density of 1,142 Wh L −1 , indicating that this design strategy is applicable to lithium metal batteries.