Position-Responsive SEI Layer in Bicomponent-Bidirectional Gradient Current Collector Induces Homogenized Ion Flux for Highly Reversible Li Metal Anode

A gradient current collector (GCC) can encourage preferential Li metal deposition on the more lithiophilic/conductive bottom of 3D anodes, enhancing the reversibility of the battery. However, as the deposition proceeds, the reduction of lithophilicity/conductivity easily causes the disturbance of Li+ flux. Herein, a brand-new bicomponent-bidirectional gradient current collector (BGCC) is proposed. The BGCC constructs slow-release additives with reverse gradient distribution (SA gradient) based on GCC, allowing it to build a position-responsive solid electrolyte interface layer. Additionally, as the deposition amount increases, the slow-release additives will release more and present a stronger ability to regulate Li+ flux, ensuring the anodereversibility under large deposition amounts conditions. Consequently, asymmetric cells can exhibit high reversibility with an average coulomb efficiency (CE) of 97.8% and sustain over 200 cycles using carbonate-based electrolytes. The Li@BGCC||LiFePO4 full cells hold a capacity retention of 94.8% over 400 cycles with thin Li. Notably, even at low temperatures, the Li@BGCC anodes can exhibit a CE as high as 98.46% and excellent capacity retention of 97.8% after 100 cycles paired with NCM811 cathodes. This strategy opens up a new direction for the development of 3D current collectors. The gradient current collector (GCC) loses the effect of uniform Li metal deposition in some areas with poor lithophilicity/conductivity. To solve the problem, this work constructs a novel bicomponent-bidirectional gradient current collector by introducing a gradient-distributed slow-release additive into GCC. Due to the synergistic effect of the additive and GCC, Li metal can be uniformly deposited at any location.image