Developing TiO2/polyacrylonitrile nanofibrous functional layer for the negative electrode of “zero-excess” lithium-metal batteries

The concept of the "zero-excess" lithium-metal batteries (ZELMBs), or the so-called anode-free lithium batteries, utilizing the copper foil current collector as the negative electrode, is designed to improve the energy density for the next generation lithium-metal batteries (LMBs). Because of the low electrolyte affinity of copper substrates, however, lithium dendrites are easily formed during the charge-discharge cycling process, leading to continuous electrolyte consumption and accelerated capacity loss, an inevitable challenge for this cell configuration. Herein, we design a lithiophilic nanofibrous membrane consisting of polyacrylonitrile (PAN) and titanium dioxide (TiO2) via an electrospinning process on the copper foil to deposit lithium uniformly. As a result, the capacity retention (51.8 %) and discharge capacity (77.32 mAh g−1) on such a modified copper foil are significantly improved in comparison with its untreated counterpart (40.3 % retention rate, 52.73 mAh g−1 discharge capacity) in the 0.5C-charge-1C-discharge program for 100 cycles in the ZELMB cells. Rather than the approach using the two-electrode configurations (i.e., Li||Cu, LFP||Li), we directly decouple the potential variations of both electrodes in LFP||Cu to gain the understanding of their charge-discharge mechanisms in the three-electrode Swagelok system. Lastly, this work not only constructs an effectively modified electrode, allowing the high current density operation of ZELMBs but also demonstrates a broad scope for studying the charge storage mechanism.