Highly Effective Electrolytes toward High‐Performance Aluminum/Seawater Batteries

Abstract The poor performance of metal/water batteries caused by self‐corrosion of anodes and low catalytic activity of cathodes has been a long‐standing challenge, greatly limiting their practical applications, in particular the underwater unmanned vehicle (UUV) application. We have fabricated an Al/seawater battery using simulated seawater with an appropriate pH and added with polyacrylic acid (PAA) as the electrolyte. This electrolyte simultaneously greatly retards self‐corrosion of the Al anode by in situ forming a PAA‐Al 3+ complex film on it and increases the electrocatalytic activity toward the hydrogen evolution reaction by improving the electronic structure of Pt. When utilizing the multielement‐doped Al sheet as the anode and nickel foam supported loading‐amount‐optimized Pt/C catalyst as the cathode and adopting the developed new electrolyte, the obtained Al/H 2 O battery exhibits an energy density of 2271 Wh kg −1 , which is the highest among those of all the reported batteries, and a power density of 20.87 mW cm −2 , which outperforms all the reported metal/H 2 O batteries. This work not only develops a new type of high‐performance Al/H 2 O batteries for practical applications such as UUVs, but provides scientific insight into the design of superior electrolytes, which could be further extended for improving the performances of various metal batteries.