Manganese dioxide(MnO2)is considered as a potential cathode material for aqueous magnesium-ion batteries.However,the charge/discharge mechanism of MnO2 in aqueous electrolyte is still unclear.In present study,highly porous δ-MnO2 is investigated,which delivers a high capacity of 252.1 mAh g-1 at 0.05 A g-1 and excellent rate capability,i.e.,109.7 mAh g-1 at 1 A g-1,but a low-capacity retention of 54.4％after 800 cycles at 1 A g-1.The two-step discharging process,namely a consequent H+and Mg2+insertion reaction,is verified,by comparing the electrochemical performance of δ-MnO2 in 1 M MgCl2 and 1 M MnCl2 aqueous electrolyte and analyzing detailedly the Mg content and the bonding state of Mn at different charge/discharge state.Furthermore,partial irreversibility of Mg2+ion insertion/extrac-tion is observed,which may be one of the major reasons leading to capacity decay.

College of Materials Science and Engineering,Sichuan University,Chengdu 610065,Sichuan,China;Institute of New Energy and Low-Carbon Technology,Sichuan University,Chengdu 610207,Sichuan,China;Engineering Research Center of Alternative Energy Materials and Devices,Ministry of Education,Chengdu 610065,Sichuan,China

[1]Zhenzhen Liu;Xiang Li;Jian He;Qian Wang;Ding Zhu;Yigang Yan;Yungui Chen-.Is proton a charge carrier forS-MnO2 cathode in aqueous rechargeable magnesium-ion batteries?)[J].能源化学,2022(05):572-579

forS,Mg2+insertion,Mg2+ion

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