High-Performance Aqueous Sodium-Ion Batteries with Hydrogel Electrolyte and Alloxazine/CMK-3 Anode

Aqueous rechargeable sodium-ion batteries (AR-SIBs) are promising candidates for large-scale energy storage applications due to their high safety, low cost, and environmental friendliness. However, appropriate anode materials with high capacity for ARSIBs are limited, and their cycling stability is generally unsatisfactory. Here we report high-performance ARSIBs with polyacrylamide hydrogel as electrolyte and alloxazine (ALO) encapsulated in CMK-3 as anode. The hydrogel with solid content of 60% could effectively mitigate the dissolution issue of sodiated ALO because its cross-linked structure is helpful to reserve H2O. The ALO/CMK-3 anode based on a two-electron transfer reaction could deliver a high capacity of 160 mA h g(-1). The introduction of CMK-3 could improve the electrical conductivity of ALO and further reduce the dissolution of sodiated ALO because of its high conductivity and nanochannel structure. The full ARSIBs exhibit an energy density of 50 W h kg(-1) (based on the total mass of active electrode materials) with good capacity retention of 90% after 100 cycles at 2 C and high rate capability of 146 mA h g(-1) at 10 C (1 C = 250 mA g(-1)). This work paves the way to construct high-performance ARSIBs with high-capacity organic anode and hydrogel electrolyte.