High-performance aqueous Na–Zn hybrid ion battery boosted by “water-in-gel” electrolyte

Aqueous hybrid Na–Zn ion batteries (ASZIBs) are promising for large-scale energy storage due to their low cost and potential for high output voltage. However, most ASZIBs show limited discharge voltage (–1) due to inefficient usage of the dual ions. In this study, a novel large-electrochemical-window “water-in-gel” electrolyte based CuHCF-CNT/Zn Na–Zn hybrid battery is proposed, which achieves a high extraction voltage of Na ion (2.1 V vs Zn/Zn2+), together with a large discharge specific capacity (260 mAh g–1) thanks to the Zn-ion insertion, delivering a superior energy density of 440 Wh kg–1. The hybrid battery also shows a high capacity retention of 96.8% after 450 cycles. Moreover, an ultrahigh discharge capacity of 1250 mAh g–1 is achieved when further coupled with the Zn-O2 reaction, delivering the promising application of ion intercalation and metal–air hybrid battery

High-energy SWCNT cathode for aqueous Al-ion battery boosted by multi-ion intercalation chemistry

The aqueous Al-ion battery has achieved great progress in recent years. It now shows comparable performance to that of even non-aqueous Al-ion batteries. However, it also shows relatively low energy output and there is limited general understanding of the mechanism behind this restriction to its practical application. Thus, the development of a high-performance cathode material is in great demand. Herein, a high-capacity single-walled carbon nanotube (SWCNT) is developed as a cathode for the water-in-salt electrolyte-based aqueous Al-ion battery, which provides an ultra-high specific capacity of 790 mAh g–1 (based on the mass of SWCNT) at a high current density of 5 A g–1 even after 1000 cycles. Moreover, the SWCNT/Al battery shows a complicated multi-ion intercalation mechanism, where AlCl4–, Cl–, Al3+, and H+ can function at the same time, improving the battery output. Beyond recently revealed H+ and metal ion co-intercalation, the Cl-assisted intercalation of Al3+ ions mechanism is also studied by experimental characterization and modeling for the first time, which significantly boosts the Al3+ storage capacity. This multi-ion intercalation mechanism combines the high-voltage anion deintercalation and the high-capacity cation intercalation, and thus, benefits the development and application of high-energy Al-ion batteries in the future