Innovative Anode Design to Enhance Both Volumetric and Gravimetric Energy Densities of LiCoO2||Graphite Pouch Cells

A gradient structured graphite (Gr) anode with an N/P < 1 is proposed. Through adding a small amount of silver (Ag) nanoparticles into the bottom layer, the designed anode can adjust the concentration polarization of Li-ion in the direction of anode thickness and control the excess Li-ion to uniformly deposit, finally achieving higher energy density without sacrificing safety.

Abstract

The ratio of the anode (negative electrode) and cathode (positive electrode) areal capacities (N/P ratio), is an important parameter for Lithium-ion batteries. Considering the manufacturing tolerance and battery safety, almost all of the batteries keep the N/P ratio > 1. Deviating from this ratio can lead to lithium precipitation on the anode surface, which poses significant risks. Here, by using a gradient structured graphite (Gr) anode, a new design concept is proposed that the N/P ratio could be less than 1, which can effectively achieve higher energy density without sacrificing the battery safety. This is achieved by incorporating a small quantity of silver (Ag) nanoparticles into the bottom layer of the anode (Gr-Ag_x), which effectively modulates the concentration polarization of lithium ions along the thickness of the electrode. Moreover, the volumetric energy density of 4 Ah LiCoO₂||Gr-Ag_0.5 (N/P = 0.8) pouch cell increases by 14.5% compared with LiCoO₂||Gr (N/P = 1.1). Furthermore, the universal applicability and efficacy of the N/P < 1 design paradigm in LiFePO₄||Gr cells are validated.