The Jahn-Teller effect and the dissolution of Mn are significant factors contributing to the capacity degradation of spinel LiMn_(2)O_(4) cathode materials during charging and discharging.In this study,Mo^(6+)-doped p...The Jahn-Teller effect and the dissolution of Mn are significant factors contributing to the capacity degradation of spinel LiMn_(2)O_(4) cathode materials during charging and discharging.In this study,Mo^(6+)-doped polycrystalline octahedral Li_(1.05)Mn_(2-x)Mo_(x)O_(4)(x=0,0.005,0.01,0.015)cathode materials were prepared by simple solid-phase sintering,and their crystal structures,microscopic morphologies,and elemental compositions were characterized and analyzed.The results showed that the doping of Mo^(6+)promoted the growth of(111)crystalline facets and increased the ratio of Mn^(3+)/Mn^(4+).The electrochemical performance of the materials was also tested,revealing that the doping of Mo^(6+)significantly improved the initial charge/discharge specific capacity and cycling stability.The modified sample(LMO-0.01Mo)retained a reversible capacity of 114.83 mA h/g with a capacity retention of 97.29%after 300 cycles.Additionally,the doping of Mo^(6+)formed a thinner,smoother SEI film and effectively inhibited the dissolution of Mn.Using density-functional theory(DFT)calculations to analyze the doping mechanism,it was found that doping shortens the Mn-O bond length inside the lattice and increases the Li-O bond length.This implies that the Li^(+)diffusion channel is widened,thereby increasing the Li^(+)diffusion rate.Additionally,the modification reduces the energy band gap,resulting in higher electronic conductivity.展开更多
文摘The Jahn-Teller effect and the dissolution of Mn are significant factors contributing to the capacity degradation of spinel LiMn_(2)O_(4) cathode materials during charging and discharging.In this study,Mo^(6+)-doped polycrystalline octahedral Li_(1.05)Mn_(2-x)Mo_(x)O_(4)(x=0,0.005,0.01,0.015)cathode materials were prepared by simple solid-phase sintering,and their crystal structures,microscopic morphologies,and elemental compositions were characterized and analyzed.The results showed that the doping of Mo^(6+)promoted the growth of(111)crystalline facets and increased the ratio of Mn^(3+)/Mn^(4+).The electrochemical performance of the materials was also tested,revealing that the doping of Mo^(6+)significantly improved the initial charge/discharge specific capacity and cycling stability.The modified sample(LMO-0.01Mo)retained a reversible capacity of 114.83 mA h/g with a capacity retention of 97.29%after 300 cycles.Additionally,the doping of Mo^(6+)formed a thinner,smoother SEI film and effectively inhibited the dissolution of Mn.Using density-functional theory(DFT)calculations to analyze the doping mechanism,it was found that doping shortens the Mn-O bond length inside the lattice and increases the Li-O bond length.This implies that the Li^(+)diffusion channel is widened,thereby increasing the Li^(+)diffusion rate.Additionally,the modification reduces the energy band gap,resulting in higher electronic conductivity.
