Improving the initial Coulombic efficiency of hard carbon-based anode for rechargeable batteries with high energy density

Recently, hard carbons have been extensively studied as anode materials for high-energy rechargeable batteries owing to their low costs, potential high capacities and talented rate capability. Nevertheless, they suffer a low initial Coulombic efficiency (ICE) problem which prohibits their broad practical application. Here we develop a facile prelithiation scheme for hard carbon/graphene (HCG) anodes based on a spontaneous electrochemical reaction with lithium metal foils. The ICE can reach a desirable level by easily tuning the prelithiation time. Importantly, the accurate amount of lithium preloaded into HCG is determined by an atomic adsorption spectrum method. Besides, a similar presodiation process is employed to demonstrate the versatility of this strategy. The surface characterization of prelithiated and presodiated HCG confirms that generated solid electrolyte interface layers have almost identical compositions as those formed during the conventional electrochemical charge-discharge cycles. Moreover, the prelithiated HCG paring with a commercial high-capacity cathode, LiNi0.5Co0.2Mn0.3O2 (NMC), enables the full-cell a comparable galvanostatic capacity and rate capability to NMC half-cell (vs. Li) and a superior cycling performance. These encouraging results indicate an accessible solution to solve problems related to low ICEs of hard carbons.