Transition Metal Assisting Pre-Lithiation Reduces the P/N Ratio to Balance the Energy Density and Cycle Life of Aqueous Batteries

摘要

Aqueous Li-ion batteries (ALIBs) are safe, environmentally friendly, andcost-effective, promising for electric energy storage (EES). The high voltageALIBs (HV-ALIBs) supported by water-in-salt electrolytes are ideal forlowering the energy cost ($/Wh) of EES. However, HV-ALIBs have beenbuilt with a high positive/negative capacity ratio (P/N ratio) to ensure theirlong-term cycle life due to the irreversible Li consumption in the initial cycleinduced by the solid electrolyte interface (SEI) formation and the parasiticreaction. Thus, the benefits of HV-ALIBs in cost and energy density aremitigated inevitably. Generally, the feasible approach is adding per-lithiationadditives (Pas) to compensate for the capacity loss in the initial cycle. However,using Pas in ALIBs is challenging due to the high chemical activityof water. Here, a new strategy to achieve the pre-lithiation by introducingmanganese metal as a sacrificial PA for HV-ALIBs that can provide over900 mAh g~(?1) specific capacity without any adverse impact is proposed.The P/N ratio reduces to 1.02 by the LiMn_2O_4‖TiO_2 pouch cell using thesacrificial manganese PA. This results in a high initial energy density above120 Wh kg~(?1) and outstanding cycle stability with a capacity retention of80 after 400 cycles.