科研之友
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摘要
The valence and coordination structure of transition metals in electrode materials play a crucial role in the electrochemical energy storage process. However, it is still challenging to modulate the chemical environment of transition metals in multi-metal-based electrode materials because of the presence of charge exchange between the different metal ions. Here, a bimetallic-based electrode material, Co0.03Ni0.97LDH, with low electrochemical activity is transformed into a highly active one through a simple and efficient electrochemical activation process with the assistance of carbon quantum dots (CQDs). It reveals that CQDs can provide a fast charge transfer channel for the unique valence regulation between Co and Ni, resulting in the generation of high concentrations of Co3+ and Ni2+, which is beneficial for upgrading the energy density of the electrode material and mitigating the Jahn-Teller distortion during the conversion of Ni2+/Ni3+. Moreover, the distinctive 5-coordination structures of Co can effectively stabilize the active sites of both Ni2+ and Co3+. The activated CQD-modified Co0.03Ni0.97LDH composites (A-CQD/Co0.03Ni0.97LDH) deliver a high specific capacity of 2408 F g(-1) at 1 A g(-1) and maintain a high capacity retention of 90% after 2000 cycles at 10 A g(-1). The assembled asymmetric supercapacitor and the aqueous Ni-Zn battery show a high energy storage density of 0.25 mW h cm(-2) at a power density of 2.25 mW cm(-2) and 1.44 mW h cm(-2) at 0.72 mW cm(-2), respectively. The impressive results provide a feasible strategy for the rational design of multi-metal-based electrode materials.
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单位北京航空航天大学; 南昌航空大学
