A Membrane‐Free Rechargeable Seawater Battery Unlocked by Lattice Engineering

Abstract

Seawater batteries that directly utilize natural seawater as electrolytes are ideal sustainable aqueous devices with high safety, exceedingly low cost, and environmental friendliness. However, the present seawater batteries are either primary batteries or rechargeable half‐seawater/half‐nonaqueous batteries because of the lack of suitable anode working in seawater. Here, we demonstrate a unique lattice engineering to unlock the electrochemically inert anatase TiO2 anode to be highly active for the reversible uptake of multiple cations (Na+, Mg2+, and Ca2+) in aqueous electrolytes. Density functional theory calculations and in‐situ Raman further reveal the origin of the unprecedented charge storage behaviors, which can be attributed to the significant reduction of the cations diffusion barrier within the lattice, i.e., from 1.5 eV to 0.4 eV. As a result, the capacities of anatase TiO2 with 2.4% lattice expansion are ca. 100 times higher than the routine one in natural seawater, and ca. 200 times higher in aqueous Na+ electrolyte. The finding should significantly advance aqueous seawater energy storage devices closer to practical applications.This article is protected by copyright. All rights reserved

Competitive Tradeoff between Zn Deposition and Hydrogen Evolution Reaction on Zn-Metal Anode

“…Aqueous zinc batteries have great potential due to the high specific capacity (820 mAh g –1 , 5855 mAh cm –3 ), low redox potential (−0.76 V vs the standard hydrogen electrode), − low cost, and inherent safety of aqueous electrolytes. However, due to its thermodynamic instability, the Zn-metal anode faces a series of problems caused by solvent water, such as the hydrogen evolution reaction (HER), corrosion, and zinc dendrites. − More seriously, these problems are not isolated but interact with each other, exacerbating the rapid degradation of electrochemical performance. − The core of the HER-related issue lies in the competition between two electrochemical reactions: the reduction of water (resulting in the HER) and the deposition of Zn ion (Zn 2+ /Zn).…”