Mitigating Overcharge in Ampere-Hour-Level Anode-Free Pouch Cells by Improving Pressure Uniformity

Anode-free batteries have gained significant attention due to their high energy density and low cost. Stack pressure is a key factor determining Li deposition morphology and, hence, Coulombic efficiency and cycle life in anode-free batteries. However, how the pressure uniformity affects the Li deposition process is poorly understood. Here we develop an ampere-hour-level anode-free pouch cell with a high energy density of 415 Wh/kg by directly integrating a LiCoO2 cathode and a Cu foil anode. We find that a nearly 3 times higher Li deposition density can be enabled by a high pressure, while overcharge occurs if the pressure is not uniform. Using an additional soft layer to disperse the pressure, the Li deposition has been further densified and the overcharge phenomenon can be lessened. Therefore, the anode-free pouch cell (2.22 Ah) can deliver a capacity retention rate of 70% after 100 cycles. We expect our observation can be transferred to practical Li metal batteries as well.