Rational Design of Electrolyte Additives Enabling Long-Life Aqueous Zn-Ni Batteries with High Current Density and...

Zinc-nickel batteries (ZNBs) are promising green energy storage devices. However, ZNBs employing traditional strong alkaline aqueous electrolytes are plagued by dendrite formation, corrosion, shape change, and electrolyte dehydration, which severely hinder their wider application. To overcome such obstacles, introducing sodium polyacrylate (PANa) and trimethyloctadecylammonium chloride (STAC) as electrolyte additives is proposed. The PANa-based electrolyte can maintain sufficient moisture in a high-concentration KOH environment and a high ionic conductivity. Additionally, the zincophilic STAC cation adsorbs on the protrusions, inhibits shape changes, promotes lateral growth, and forms a noticeably smooth and dense Zn anode. Therefore, the ZNBs assembled with PANa and STAC additives in the electrolyte have an impressive cycle life of 1168 h at a current density of 66.7 mA cm^-2 (the discharge rate of 2C) and can maintain a cycle life exceeding 527 h at a high current density of 100.1 mA cm^-2 (the discharge rate of 3C). The symmetric cells demonstrate remarkable performance, enduring a stable lifespan surpassing 310 h under a discharge current density of 33.4 mA cm^-2, coupled with a notable areal capacity of 33.4 mAh cm^-2. The ZNB still retains a stable voltage of 1.78 V and has a capacity retention rate of 83.7% after being fully charged and left for 240 h. The proposed electrolyte modification strategy has a large-scale impact on ZNBs targeted for commercialization and has great replication potential.