A dual-protection strategy using CMK-3 coated selenium and modified separators for high-energy Al-Se batteries

The aluminum-selenium (Al-Se) battery is a very promising rechargeable battery system due to its high theoretical specific capacity of 1357 mA h g(-1) and high average discharge voltage of similar to 1.52 V versus Al/Al3+. However, Al-Se batteries suffer poor reversibility, since the intermediate product Se2Cl2 dissolved in the acidic electrolyte causes significant capacity fading. To overcome this critical issue, a dual-protection design with composites of selenium nanoparticles encapsulated in mesoporous carbon (CMK-3) and separators modified by CMK-3 are developed. Because of the great physical blocking of the intermediate product dissolved in the electrolyte, the as-assembled Al-Se batteries can deliver an ultrahigh capacity of similar to 1295 mA h g(-1) (approximate the theoretical specific capacity) in the first two cycles, and retain a capacity of 651 mA h g(-1) (retention rate of 50.3%) over 400 cycles at a current density of 1000 mA g(-1). The rational design of the Al-Se batteries with dual protection from the CMK-3 coated Se positive electrode and modified separators is effective in promoting the electrochemical performance of the batteries.

Automated summary

The Al-Se battery system shows great promise with a high theoretical specific capacity and average discharge voltage, but suffers from poor reversibility due to Se2Cl2 dissolution leading to capacity fading. By incorporating selenium nanoparticles in mesoporous carbon and modified separators, the Al-Se batteries demonstrate high capacity in initial cycles and good retention over 400 cycles at a high current density.