Inducing spherical lithium deposition via simultaneously optimized electric field and ionic flux for fast-charging lithium metal batteries

Abstract

Nonuniform Li-ion gradient and electric fields in conventional host lead to uncontrollable Li top-growth behavior and Li dendrite, impeding the practical application of lithium metal anodes (LMAs). Herein, we design a 3D hierarchical flexible membrane host with gradient lithiophilic properties (GFC@PVDF) to regulate bottom-up growth of the spherical Li within host, by optimizing the electric field and Li-ion flux. The membrane networks with CNT as cores and β-PVDF as linking shells enabling fast electron transfer and low Li-ion migration energy barriers. Gradient Fe₂O₃ particles in the membrane by layer-by-layer bottom-up attenuating could induce Li-ion dredging and pumps towards the bottom for bottom-up deposition regime, reducing ion concentration gradient via lithiophilic gradient properties. Meanwhile, the Fe₂O₃ is converted into hybrid electron/ion conductor Fe/Li₂O during cycling, which acts as charge decoupling and fast transport path that enhances the bottom transport of Li-ions. Consequently, stable symmetric cells over 500 cycles with Li spherical uniform deposition are obtained under an ultrahigh current density of 50 mA cm^-2. The full cell paired with LiFePO₄ cathode exhibits remarkable cycling stability at a low N/P ratio of 1.7. This study provides new insights into dendrite-free Li metal anodes, paving the way for high-energy, fast-charging LMAs.