Issues and challenges facing aqueous sodium-ion batteries toward practical applications

Aqueous sodium-ion batteries (ASIBs) have attracted widespread attention in the energy storage and conversion fields due to their benefits in high safety, low cost, and environmental friendliness. However, compared with the sodium-ion batteries born in the same period, the commercialization of ASIB has been significantly delayed. Although great efforts have been made on the electrode/electrode design and interface regulation, the performance of ASIBs is far from the practical requirements. This review first comprehensively compared ASIBs and lead acid batteries in terms of battery structure, performance, sustainable manufacturing, circular economy, and environmental impact. Then, the issues and challenges relevant to the unfavorable behaviors of ASIBs are discussed in detail, such as low energy density caused by narrow electrochemical stability window of water, limited choice of electrode materials, unstable electrode/electrolyte interface, immature battery manufacturing technology, and so forth. We hope that this review provides pertinent insight into the research focus and rational design of applicable ASIBs.