Mn-rich layered oxides are appealing cathodes for potassium ion batteries(PIBs)in view of their comprehensive virtues such as low cost,high energy density and mature craftsmanship.However,the insufficient covalency be...Mn-rich layered oxides are appealing cathodes for potassium ion batteries(PIBs)in view of their comprehensive virtues such as low cost,high energy density and mature craftsmanship.However,the insufficient covalency between transition metal(TM)and O usually induces irreversible structural evolution and cation migration during repeated insertion and extraction of K^(+),resulting in capacity loss,voltage fading and sluggish kinetics.Herein,an anion substitution strategy is proposed for a stable operation of layered oxide cathode by adjusting the valence electron layer structure between TM and O.The resultant strong TM−O skeleton can inhibit the occurrence of side effects derive from Ni^(4+)during the deep depotassium process,so as to achieve a gentle structural transition.Consequently,stable cycling performance of K_(0.39)Mn_(0.77)Ni_(0.23_O_(1.9)F_(0.1)(KMNOF)cathode is achieved with 77%capacity retention over 350 cycles at 100mA/g,yielding high discharge capacity 93.5 mAh/g at 20mA/g and significantly improved rate capability of 50.1 mAh/g at 500 mA/g,whereas irreversible structural evolution and rapid capacity fade with KMNO cathode.Finally,in situ/ex situ characterizations and theoretical computations sheds light on the charge transfer and structure evolution mechanisms of KMNOF.展开更多
Using the first-principles calculations based on density functional theory(DFT),the structure stability,electronic and some optical properties of C and N doped cubic ZrO2(c-ZrO2) in 24-atom systems were investigated.I...Using the first-principles calculations based on density functional theory(DFT),the structure stability,electronic and some optical properties of C and N doped cubic ZrO2(c-ZrO2) in 24-atom systems were investigated.It is found from the formation energies calculations that N ions are easier to be doped into c-ZrO2 than C ions.The electronic structure results show that Zr8O15C and Zr8O15N systems are semiconductors with the band gap of 2.3 eV and 2.8 eV,respectively,which are lower than that of the pure ZrO2(3.349 eV).And optical properties results depict that anion doping,especially C adding,can enhance the static dielectric function,visible and ultraviolet light absorption and reflecting ability of c-ZrO2 crystal.展开更多
基金financially supported by the National Natural Science Foundation of China(No.51902090)Henan Key Research Project Plan for Higher Education Institutions(No.24A150019)the Doctoral Start-Up Foundation(No.QD2022017).
文摘Mn-rich layered oxides are appealing cathodes for potassium ion batteries(PIBs)in view of their comprehensive virtues such as low cost,high energy density and mature craftsmanship.However,the insufficient covalency between transition metal(TM)and O usually induces irreversible structural evolution and cation migration during repeated insertion and extraction of K^(+),resulting in capacity loss,voltage fading and sluggish kinetics.Herein,an anion substitution strategy is proposed for a stable operation of layered oxide cathode by adjusting the valence electron layer structure between TM and O.The resultant strong TM−O skeleton can inhibit the occurrence of side effects derive from Ni^(4+)during the deep depotassium process,so as to achieve a gentle structural transition.Consequently,stable cycling performance of K_(0.39)Mn_(0.77)Ni_(0.23_O_(1.9)F_(0.1)(KMNOF)cathode is achieved with 77%capacity retention over 350 cycles at 100mA/g,yielding high discharge capacity 93.5 mAh/g at 20mA/g and significantly improved rate capability of 50.1 mAh/g at 500 mA/g,whereas irreversible structural evolution and rapid capacity fade with KMNO cathode.Finally,in situ/ex situ characterizations and theoretical computations sheds light on the charge transfer and structure evolution mechanisms of KMNOF.
基金Project(61172047) supported by the National Natural Science Foundation of China
文摘Using the first-principles calculations based on density functional theory(DFT),the structure stability,electronic and some optical properties of C and N doped cubic ZrO2(c-ZrO2) in 24-atom systems were investigated.It is found from the formation energies calculations that N ions are easier to be doped into c-ZrO2 than C ions.The electronic structure results show that Zr8O15C and Zr8O15N systems are semiconductors with the band gap of 2.3 eV and 2.8 eV,respectively,which are lower than that of the pure ZrO2(3.349 eV).And optical properties results depict that anion doping,especially C adding,can enhance the static dielectric function,visible and ultraviolet light absorption and reflecting ability of c-ZrO2 crystal.
