The Na_(4)MnCr(PO_(4))_(3)material is a representative NASICON-type polyanion compound,distinguished by its open three-dimensional framework,high operating voltage,and exceptionally high theoretical energy density.How...The Na_(4)MnCr(PO_(4))_(3)material is a representative NASICON-type polyanion compound,distinguished by its open three-dimensional framework,high operating voltage,and exceptionally high theoretical energy density.However,the failure mechanism associated with phase structure distortions in Na_(4)MnCr(PO_(4))_(3)during the electrochemical reaction process remains unclear.In this study,we introduce the concept of a"current-responsive transition state"(CRTS)for the first time to elucidate the unique oxidation peaks that arise between Mn^(2+)/Mn^(3+)and Mn^(3+)/Mn^(4+)at elevated potential states in Na_(4)MnCr(PO_(4))_(3)materials.The formation of Mn(PO_(3))_(3)during the electrochemical process is accompanied by an overresponse of CRTS and severe lattice distortion,which impedes the diffusion kinetics and leads to a significant reduction in the reversible platform capacity of Mn^(2+)/Mn^(3+).The introduction of a trace amount of V can effectively inhibit the formation of Mn(PO_(3))_(3),while optimizing the CRTS phenomenon,thereby enhancing the reversible platform capacity of Mn.Optimizing CRTS enables Na_(4)MnCr(PO_(4))_(3)to exhibit excellent rate performance(97.5 mAh g^(-1)at 1 C)and cycling stability(81.4%capacity retention after 500 cycles at 5 C).Furthermore,the NMCV_(50)P||HC full cell exhibits remarkable electrochemical performance,achieving a capacity of 73.5 mAh g^(-1)at 100 mA g^(-1)and demonstrating an impressive capacity retention of 94.7%after 200 cycles.This research offers valuable insights for the optimization of Mn-based polyanion materials.展开更多
基金National Natural Science Foundation of China(5247433152574355)Gusu Leading Talents of Innovation and Entrepreneurship(ZXL2023196)。
文摘The Na_(4)MnCr(PO_(4))_(3)material is a representative NASICON-type polyanion compound,distinguished by its open three-dimensional framework,high operating voltage,and exceptionally high theoretical energy density.However,the failure mechanism associated with phase structure distortions in Na_(4)MnCr(PO_(4))_(3)during the electrochemical reaction process remains unclear.In this study,we introduce the concept of a"current-responsive transition state"(CRTS)for the first time to elucidate the unique oxidation peaks that arise between Mn^(2+)/Mn^(3+)and Mn^(3+)/Mn^(4+)at elevated potential states in Na_(4)MnCr(PO_(4))_(3)materials.The formation of Mn(PO_(3))_(3)during the electrochemical process is accompanied by an overresponse of CRTS and severe lattice distortion,which impedes the diffusion kinetics and leads to a significant reduction in the reversible platform capacity of Mn^(2+)/Mn^(3+).The introduction of a trace amount of V can effectively inhibit the formation of Mn(PO_(3))_(3),while optimizing the CRTS phenomenon,thereby enhancing the reversible platform capacity of Mn.Optimizing CRTS enables Na_(4)MnCr(PO_(4))_(3)to exhibit excellent rate performance(97.5 mAh g^(-1)at 1 C)and cycling stability(81.4%capacity retention after 500 cycles at 5 C).Furthermore,the NMCV_(50)P||HC full cell exhibits remarkable electrochemical performance,achieving a capacity of 73.5 mAh g^(-1)at 100 mA g^(-1)and demonstrating an impressive capacity retention of 94.7%after 200 cycles.This research offers valuable insights for the optimization of Mn-based polyanion materials.
