Expanded graphite with boron-doping for cathode materials of high-capacity and stable aluminum ion batteries

Recently, aluminum ion batteries (AIBs) have attracted more attention due to the reliable, cost-effective, and air-stable Al metal anode. Among various cathode materials of AIBs, graphite was paid more attention owing to its high-voltage plateau and stable properties in storing chloroaluminate anions (AlCl₄ ^-). However, its low capacity limits the real application and can not satisfy the requirements of modern society. To solve the above issue, herein, boron (B)-doping expanded graphite (B-EG) was prepared by thermal treatment of expanded graphite and boric acid together in a reduction atmosphere. Based on the structural and electrochemical characterization, the results show that B-doping amplifies the interlayer space of expanded graphite (EG), introduces more mesoporous structures, and induces electron deficiency, which is beneficial to accelerating the transfer and adsorption of active ions. The results indicate that the B-EG electrode exhibits excellent rate capability and a high specific capacity of 84.9 mA h g^-1 at 500 mA g^-1. Compared with the EG electrode, B-EG shows better cycle stability with the specific capacity of 87.7 mA h g^-1 after 300 cycles, which could be attributed to lower pulverization and higher pseudo-capacitance contribution of B-EG after the introduction of B species.