P2型层状过渡金属氧化物(P2-Na_(x)TMO_(2))因其优异的循环稳定性和倍率性能,成为钠离子电池正极材料的有力候选者。然而,其在高电压下的不可逆相变和固有低理论容量问题,阻碍了实际应用。本研究工作提出高熵策略与双相结构的协同设计...P2型层状过渡金属氧化物(P2-Na_(x)TMO_(2))因其优异的循环稳定性和倍率性能,成为钠离子电池正极材料的有力候选者。然而,其在高电压下的不可逆相变和固有低理论容量问题,阻碍了实际应用。本研究工作提出高熵策略与双相结构的协同设计来克服这些挑战。通过在P2相高熵基体中引入O3相,构建新型P2/O3双相高熵层状氧化物Na_(0.70)Ni_(0.25)Mn_(0.35)Co_(0.15)Fe_(0.05)Ti_(0.20)O_(2)(简称Na_(0.70)NMCFT)。其中,高熵设计通过构型熵稳定效应有效抑制P2相的不可逆相变,而O3相则通过协同作用弥补容量不足并提升循环稳定性。此外,双相组分之间的相互作用进一步促进P2-O3与P2-P3相变的高度可逆性。Na_(0.70)NMCFT在1C倍率下的初始放电容量为102.08 mAhg^(-1),200次循环后容量保持率达88.15%,表明具有优异的循环稳定性。更重要的是,即使在10C的高倍率下,Na_(0.70)NMCFT仍能提供85.67 mAh g^(-1)的初始放电比容量,并在1000次循环后容量保持率达70%。本工作证实双相高熵设计在提升钠离子电池正极性能中的关键作用,为开发先进钠离子电池正极材料提供了新思路。展开更多
P2-type nickel-manganese-based layered oxides are promising cathode materials for sodium-ion batteries(SIBs),but their application is limited by initial specific capacity and anion redox instability.Herein,a P2/O3 bip...P2-type nickel-manganese-based layered oxides are promising cathode materials for sodium-ion batteries(SIBs),but their application is limited by initial specific capacity and anion redox instability.Herein,a P2/O3 biphasic Na_(0.67)Ni_(0.33)Mn_(0.6)Cu_(0.05)Mg_(0.07)Ti_(0.01)O_(2)(Ni33Mn60)was prepared by adjusting the Ni/Mn ratio with as Na_(0.67)Ni_(0.23)Mn_(0.65)Cu_(0.05)Mg_(0.07)Ti_(0.01)O_(2)(Ni23Mn65)matrix and is reported to exhibit high initial discharge capacity,cyclability and rate capability.The density functional theory(DFT)calculation and experimental data prove the enhancement of the Mn^(3+)/Mn^(4+)redox process to improve the specific discharge capacity and the P2/O3biphasic structure to optimize the anion kinetics.The synthesized oxide Ni33Mn60 delivers a high initial discharge specific capacity of 140.21 mAh g^(-1),a crucial discharge capacity of 76.07 mAh g^(-1)at 10C,a preferable capacity retention rate of 78.97%after 200 cycles at 5C and cycle stability at high voltages above 4.3V.In situ X-ray diffraction(XRD)and galvanostatic intermittent titration technique(GITT)tests show that Ni33Mn60 has reversible structure evolution and fast Na^(+)diffusion kinetics due to the ion effect and unique P2/O3 biphasic structure,respectively.This work provides a new thought about adjusting matrix ratio for the preparation of P2/O3 biphasic cathode materials for advanced SIBs.展开更多
P2/O3-type Ni/Mn-based layered oxides are promising cathode materials for sodium-ion batteries(SIBs)owing to their high energy density.However,exploring effective ways to enhance the synergy between the P2 and 03 phas...P2/O3-type Ni/Mn-based layered oxides are promising cathode materials for sodium-ion batteries(SIBs)owing to their high energy density.However,exploring effective ways to enhance the synergy between the P2 and 03 phases remains a necessity.Herein,we design a P2/O3-type Na_(0.76)Ni_(0.31)Zn_(0.07)Mn_(0.50)Ti_(0.12)0_(2)(NNZMT)with high chemical/electrochemical stability by enhancing the coupling between the two phases.For the first time,a unique Na*extraction is observed from a Na-rich O3 phase by a Na-poor P2 phase and systematically investigated.This process is facilitated by Zn^(2+)/Ti^(4+)dual doping and calcination condition regulation,allowing a higher Na*content in the P2 phase with larger Na^(+)transport channels and enhancing Na transport kinetics.Because of reduced Na^(+)in the O3 phase,which increases the difficulty of H^(+)/Na^(+) exchange,the hydrostability of the O3 phase in NNZMT is considerably improved.Furthermore,Zn^(2+)/Ti^(4+)presence in NNZMT synergistically regulates oxygen redox chemistry,which effectively suppresses O_(2)/CO_(2) gas release and electrolyte decomposition,and completely inhibits phase transitions above 4.0 V.As a result,NNZMT achieves a high discharge capacity of 144.8 mA h g^(-1) with a median voltage of 3.42 V at 20 mA g^(-1) and exhibits excellent cycling performance with a capacity retention of 77.3% for 1000 cycles at 2000 mA g^(-1).This study provides an effective strategy and new insights into the design of high-performance layered-oxide cathode materials with enhanced structure/interface stability forSIBs.展开更多
Layered transition metal oxides have emerged as promising cathode materials for sodium ion batteries.However,irreversible phase transitions cause structural distortion and cation rearrangement,leading to sluggish Na+d...Layered transition metal oxides have emerged as promising cathode materials for sodium ion batteries.However,irreversible phase transitions cause structural distortion and cation rearrangement,leading to sluggish Na+dynamics and rapid capacity decay.In this study,we propose a medium-entropy cathode by simultaneously introducing Fe,Mg,and Li dopants into a typical P2-type Na_(0.75)Ni_(0.25)Mn_(0.75)O_(2)cathode.The modified Na_(0.75)Ni_(0.2125)Mn_(0.6375)Fe_(0.05)Mg_(0.05)Li_(0.05)O_(2)cathode predominantly exhibits a main P2 phase(93.5%)with a minor O3 phase(6.5%).Through spectroscopy techniques and electrochemical investigations,we elucidate the redox mechanisms of Ni^(2+/3+/4+),Mn^(3+/4+),Fe^(3+/4+),and O_(2)-/O_(2)^(n-)during charging/discharging.The medium-entropy doping mitigates the detrimental P2-O_(2)phase transition at high-voltage,replacing it with a moderate and reversible structural evolution(P2-OP4),thereby enhancing structural stability.Consequently,the modified cathode exhibits a remarkable rate capacity of 108.4 mAh·g^(-1)at 10C,with a capacity retention of 99.0%after 200 cycles at 1C,82.5%after 500 cycles at 5C,and 76.7%after 600 cycles at 10C.Furthermore,it also demonstrates superior electrochemical performance at high cutoff voltage of 4.5 V and extreme temperature(55 and 0℃).This work offers solutions to critical challenges in sodium ion batteries cathode materials.展开更多
The effect of Na-excess content in the precursor on the structural and electrochemical performances of sodium nickel manganese oxide(NNMO)prepared by sol-gel and electrospinning methods is investigated in this paper.X...The effect of Na-excess content in the precursor on the structural and electrochemical performances of sodium nickel manganese oxide(NNMO)prepared by sol-gel and electrospinning methods is investigated in this paper.X-ray diffraction results of the prepared NNMO without adding Na-excess content indicate sodium loss,while the mixed phase of P2/O′3-type layered NNMO presented after adding Na-excess content.Compared with the sol-gel method,the secondary phase of NiO is more suppressed by using the electrospinning method,which is further confirmed by field emission scanning electron microscope images.N_(2) adsorption-desorption isotherms show no remarkably difference in specific surface areas between different preparation methods and Na-excess contents.The analysis of X-ray absorption near edge structure indicates that the oxidation states of Ni and Mn are+2 and+4,respectively.For the electrochemical properties,superior electrochemical performance is observed in the NNMO electrode with a low Na-excess content of 5wt%.The highest specific capacitance is 36.07 F·g^(-1)at0.1 A·g^(-1)in the NNMO electrode prepared by using the sol-gel method.By contrast,the NNMO electrode prepared using the electrospinning method with decreased Na-excess content shows excellent cycling stability of 100%after charge-discharge measurements for 300 cycles.Therefore,controlling the Na excess in the precursor together with the preparation method is important for improving the electrochemical performance of Na-based electrode materials in supercapacitors.展开更多
文章采用一步固相烧结法成功合成了锂/铌共掺杂的P2-Na_(0.67)Fe_(0.5)Mn_(0.5)O_(2)钠离子电池层状氧化物正极材料。结果表明,锂掺杂促进了P2/O3双相结构的形成,同时将P2-OP4相变转化为温和的固溶反应;铌掺杂形成了较强的Nb-O键,提高...文章采用一步固相烧结法成功合成了锂/铌共掺杂的P2-Na_(0.67)Fe_(0.5)Mn_(0.5)O_(2)钠离子电池层状氧化物正极材料。结果表明,锂掺杂促进了P2/O3双相结构的形成,同时将P2-OP4相变转化为温和的固溶反应;铌掺杂形成了较强的Nb-O键,提高过渡金属层的结构稳定性,且铌掺杂诱导材料表面生成NaNbO3表面包覆层,有效阻碍过渡金属溶解和表面副反应。所制备的锂/铌共掺杂P2-Na_(0.67)Fe_(0.5)Mn_(0.5)O_(2)在2.0~4.0 V范围内以0.5C(1C=174 mA g^(-1))循环100圈后容量保持率为85%,远高于原材料的46%。展开更多
文摘P2型层状过渡金属氧化物(P2-Na_(x)TMO_(2))因其优异的循环稳定性和倍率性能,成为钠离子电池正极材料的有力候选者。然而,其在高电压下的不可逆相变和固有低理论容量问题,阻碍了实际应用。本研究工作提出高熵策略与双相结构的协同设计来克服这些挑战。通过在P2相高熵基体中引入O3相,构建新型P2/O3双相高熵层状氧化物Na_(0.70)Ni_(0.25)Mn_(0.35)Co_(0.15)Fe_(0.05)Ti_(0.20)O_(2)(简称Na_(0.70)NMCFT)。其中,高熵设计通过构型熵稳定效应有效抑制P2相的不可逆相变,而O3相则通过协同作用弥补容量不足并提升循环稳定性。此外,双相组分之间的相互作用进一步促进P2-O3与P2-P3相变的高度可逆性。Na_(0.70)NMCFT在1C倍率下的初始放电容量为102.08 mAhg^(-1),200次循环后容量保持率达88.15%,表明具有优异的循环稳定性。更重要的是,即使在10C的高倍率下,Na_(0.70)NMCFT仍能提供85.67 mAh g^(-1)的初始放电比容量,并在1000次循环后容量保持率达70%。本工作证实双相高熵设计在提升钠离子电池正极性能中的关键作用,为开发先进钠离子电池正极材料提供了新思路。
基金financially supported by the Natural Science Foundation of Jiangsu Province(No.BK20201049)China Postdoctoral Science Foundation(No,2022M711724)+2 种基金the Swedish Energy Agency(Nos.P2022-00055 and P2023-00603)STandUP for EnergyMAX IV Laboratory for time on Balder beamline(No.20240704)
文摘P2-type nickel-manganese-based layered oxides are promising cathode materials for sodium-ion batteries(SIBs),but their application is limited by initial specific capacity and anion redox instability.Herein,a P2/O3 biphasic Na_(0.67)Ni_(0.33)Mn_(0.6)Cu_(0.05)Mg_(0.07)Ti_(0.01)O_(2)(Ni33Mn60)was prepared by adjusting the Ni/Mn ratio with as Na_(0.67)Ni_(0.23)Mn_(0.65)Cu_(0.05)Mg_(0.07)Ti_(0.01)O_(2)(Ni23Mn65)matrix and is reported to exhibit high initial discharge capacity,cyclability and rate capability.The density functional theory(DFT)calculation and experimental data prove the enhancement of the Mn^(3+)/Mn^(4+)redox process to improve the specific discharge capacity and the P2/O3biphasic structure to optimize the anion kinetics.The synthesized oxide Ni33Mn60 delivers a high initial discharge specific capacity of 140.21 mAh g^(-1),a crucial discharge capacity of 76.07 mAh g^(-1)at 10C,a preferable capacity retention rate of 78.97%after 200 cycles at 5C and cycle stability at high voltages above 4.3V.In situ X-ray diffraction(XRD)and galvanostatic intermittent titration technique(GITT)tests show that Ni33Mn60 has reversible structure evolution and fast Na^(+)diffusion kinetics due to the ion effect and unique P2/O3 biphasic structure,respectively.This work provides a new thought about adjusting matrix ratio for the preparation of P2/O3 biphasic cathode materials for advanced SIBs.
基金supported by the National Natural Science Foundation of China (22169002)the Chongzuo Key Research and Development Program of China (20220603)the Counterpart Aid Project for Discipline Construction from Guangxi University(2023M02)
文摘P2/O3-type Ni/Mn-based layered oxides are promising cathode materials for sodium-ion batteries(SIBs)owing to their high energy density.However,exploring effective ways to enhance the synergy between the P2 and 03 phases remains a necessity.Herein,we design a P2/O3-type Na_(0.76)Ni_(0.31)Zn_(0.07)Mn_(0.50)Ti_(0.12)0_(2)(NNZMT)with high chemical/electrochemical stability by enhancing the coupling between the two phases.For the first time,a unique Na*extraction is observed from a Na-rich O3 phase by a Na-poor P2 phase and systematically investigated.This process is facilitated by Zn^(2+)/Ti^(4+)dual doping and calcination condition regulation,allowing a higher Na*content in the P2 phase with larger Na^(+)transport channels and enhancing Na transport kinetics.Because of reduced Na^(+)in the O3 phase,which increases the difficulty of H^(+)/Na^(+) exchange,the hydrostability of the O3 phase in NNZMT is considerably improved.Furthermore,Zn^(2+)/Ti^(4+)presence in NNZMT synergistically regulates oxygen redox chemistry,which effectively suppresses O_(2)/CO_(2) gas release and electrolyte decomposition,and completely inhibits phase transitions above 4.0 V.As a result,NNZMT achieves a high discharge capacity of 144.8 mA h g^(-1) with a median voltage of 3.42 V at 20 mA g^(-1) and exhibits excellent cycling performance with a capacity retention of 77.3% for 1000 cycles at 2000 mA g^(-1).This study provides an effective strategy and new insights into the design of high-performance layered-oxide cathode materials with enhanced structure/interface stability forSIBs.
基金supported by the National Natural Science Foundation of China(No.21805018)by Sichuan Science and Technology Program(Nos.2022ZHCG0018,2023NSFSC0117 and 2023ZHCG0060)Yibin Science and Technology Program(No.2022JB005)and China Postdoctoral Science Foundation(No.2022M722704).
文摘Layered transition metal oxides have emerged as promising cathode materials for sodium ion batteries.However,irreversible phase transitions cause structural distortion and cation rearrangement,leading to sluggish Na+dynamics and rapid capacity decay.In this study,we propose a medium-entropy cathode by simultaneously introducing Fe,Mg,and Li dopants into a typical P2-type Na_(0.75)Ni_(0.25)Mn_(0.75)O_(2)cathode.The modified Na_(0.75)Ni_(0.2125)Mn_(0.6375)Fe_(0.05)Mg_(0.05)Li_(0.05)O_(2)cathode predominantly exhibits a main P2 phase(93.5%)with a minor O3 phase(6.5%).Through spectroscopy techniques and electrochemical investigations,we elucidate the redox mechanisms of Ni^(2+/3+/4+),Mn^(3+/4+),Fe^(3+/4+),and O_(2)-/O_(2)^(n-)during charging/discharging.The medium-entropy doping mitigates the detrimental P2-O_(2)phase transition at high-voltage,replacing it with a moderate and reversible structural evolution(P2-OP4),thereby enhancing structural stability.Consequently,the modified cathode exhibits a remarkable rate capacity of 108.4 mAh·g^(-1)at 10C,with a capacity retention of 99.0%after 200 cycles at 1C,82.5%after 500 cycles at 5C,and 76.7%after 600 cycles at 10C.Furthermore,it also demonstrates superior electrochemical performance at high cutoff voltage of 4.5 V and extreme temperature(55 and 0℃).This work offers solutions to critical challenges in sodium ion batteries cathode materials.
基金financially supported by (i) Suranaree University of Technology,(ii) Thailand Science Research and Innovation,and (iii) National Science,Research and Innovation Fund(project codes 90464 and 160363)。
文摘The effect of Na-excess content in the precursor on the structural and electrochemical performances of sodium nickel manganese oxide(NNMO)prepared by sol-gel and electrospinning methods is investigated in this paper.X-ray diffraction results of the prepared NNMO without adding Na-excess content indicate sodium loss,while the mixed phase of P2/O′3-type layered NNMO presented after adding Na-excess content.Compared with the sol-gel method,the secondary phase of NiO is more suppressed by using the electrospinning method,which is further confirmed by field emission scanning electron microscope images.N_(2) adsorption-desorption isotherms show no remarkably difference in specific surface areas between different preparation methods and Na-excess contents.The analysis of X-ray absorption near edge structure indicates that the oxidation states of Ni and Mn are+2 and+4,respectively.For the electrochemical properties,superior electrochemical performance is observed in the NNMO electrode with a low Na-excess content of 5wt%.The highest specific capacitance is 36.07 F·g^(-1)at0.1 A·g^(-1)in the NNMO electrode prepared by using the sol-gel method.By contrast,the NNMO electrode prepared using the electrospinning method with decreased Na-excess content shows excellent cycling stability of 100%after charge-discharge measurements for 300 cycles.Therefore,controlling the Na excess in the precursor together with the preparation method is important for improving the electrochemical performance of Na-based electrode materials in supercapacitors.
文摘文章采用一步固相烧结法成功合成了锂/铌共掺杂的P2-Na_(0.67)Fe_(0.5)Mn_(0.5)O_(2)钠离子电池层状氧化物正极材料。结果表明,锂掺杂促进了P2/O3双相结构的形成,同时将P2-OP4相变转化为温和的固溶反应;铌掺杂形成了较强的Nb-O键,提高过渡金属层的结构稳定性,且铌掺杂诱导材料表面生成NaNbO3表面包覆层,有效阻碍过渡金属溶解和表面副反应。所制备的锂/铌共掺杂P2-Na_(0.67)Fe_(0.5)Mn_(0.5)O_(2)在2.0~4.0 V范围内以0.5C(1C=174 mA g^(-1))循环100圈后容量保持率为85%,远高于原材料的46%。
