Root Reason for the Failure of a Practical Zn-Ni Battery: Shape Changing Caused by Uneven Current Distribution and Zn Dissolution.

In recent years, with the increasing application of lithium-ion batteries in energy storage devices, fire accidents caused by lithium-ion batteries have become more frequent and have arisen wide concern. Due to the safety of aqueous electrolyte, aqueous Zn-based batteries have attracted vast attention, among which Zn-Ni batteries stand out by virtue of their excellent rate performance and environmental friendliness. However, poor cycling life limits the application of Zn-Ni batteries. To figure out the main cause, a failure analysis of a practical Zn-Ni battery has been carried out. During the cycling of the Zn-Ni battery, the evolution of gas, the shape changing, and the aggregation of additive and binder of Zn anode can be observed. Combined with the finite element analysis, we finally reveal that the key factor of battery failure is the shape changing of the Zn anode caused by uneven current distribution and the dissolution of Zn. The shape changing of the Zn anode reduces the effective surface area of anode and increases the possibility of dead Zn, which makes the battery unable to discharge even in the presence of a large amount of Zn. These findings are helpful to deepen the understanding of the working and failure mechanisms of the Zn anode and provide effective guidance for subsequent research.