Li₂CO₃-incorporated PVDF nanofiber network as lithium host enabling low N/P ratio lithium metal batteries

Lithium metal batteries are regarded as a solution for maximizing the energy density of Li-ion batteries. Ideally, the Li metal anode should be thin enough with a low negative to positive capacity ratio (N/P ratio ≤ 2), thus conserving the high-energy density nature of Li-metal batteries. However, reducing the lithium metal thickness limits cycling stability due to inadequate lithium reserves to counter dead lithium generation. To address this, we construct a three-dimensional (3D) polyvinylidene fluoride (PVDF) nanofiber network incorporating Li₂CO₃ as a lithium host on a copper current collector via electrospinning. Incorporating Li₂CO₃ reduces the PVDF crystallinity and promotes electrolyte wettability, enhancing Li-ion diffusion and allowing uniform Li encapsulation on the nanofiber networks. Electrochemical impedance spectroscopy also reveals that an optimized Li₂CO₃ content in the nanofiber network reduces charge transfer resistance, further enabling homogeneous lithium deposition across the nanostructure. This architecture significantly improves the electrochemical performance, delivering a stable plating and stripping cycle life up to 330 h in a half-cell configuration. In a full-cell configuration with an NMC622 cathode at an N/P ratio of 2, the optimized PVDF-Li₂CO₃ nanofiber network retains 71.6% of its initial capacity after 200 cycles, compared to the premature failure (after 60 cycles) of conventional Li-plated Cu anode. This work presents a straightforward and scalable approach to stabilizing low N/P ratio lithium metal batteries, advancing their practical application.