Charging P2-Na_(2/3)Ni_(1/3)Mn_(2/3)O_(2)to 4.5 V for higher capacity is enticing.However,it leads to severe capacity fading,ascribing to the lattice oxygen evolution and the P2-O2 phase transformation.Here,the Mg Fe_...Charging P2-Na_(2/3)Ni_(1/3)Mn_(2/3)O_(2)to 4.5 V for higher capacity is enticing.However,it leads to severe capacity fading,ascribing to the lattice oxygen evolution and the P2-O2 phase transformation.Here,the Mg Fe_(2)O_(4) coating and Mg,Fe co-doping were constructed simultaneously by Mg,Fe surface treatment to suppress lattice oxygen evolution and P2-O2 phase transformation of P2-Na_(2/3)Ni_(1/3)Mn_(2/3)O_(2)at deep charging.Through ex-situ X-ray diffraction(XRD)tests,we found that the Mg,Fe bulk co-doping could reduce the repulsion between transition metals and Na+/vacancies ordering,thus inhibiting the P2-O2 phase transition and significantly reducing the irreversible volume change of the material.Meanwhile,the internal electric field formed by the dielectric polarization of Mg Fe_(2)O_(4) effectively inhibits the outward migration of oxidized O^(a-)(a<2),thereby suppressing the lattice oxygen evolution at deep charging,confirmed by in situ Raman and ex situ XPS techniques.P2-Na NM@MF-3 shows enhanced high-voltage cycling performance with capacity retentions of 84.8% and 81.3%at 0.1 and 1 C after cycles.This work sheds light on regulating the surface chemistry for Na-layered oxide materials to enhance the high-voltage performance of Na-ion batteries.展开更多
采用原位诱导法制备得到了一系列x Li M_2O_4?(1-x)Li Ni_(1/3)Co_(1/3)Mn_(1/3)O_2(M=Ni,Co,Mn;x=0,0.1,0.2,0.3,0.4,0.5)尖晶石/层状异质结构复合材料。借助X射线衍射、扫描电镜、差示扫描量热仪、恒电流间歇滴定技术和恒电流充放电...采用原位诱导法制备得到了一系列x Li M_2O_4?(1-x)Li Ni_(1/3)Co_(1/3)Mn_(1/3)O_2(M=Ni,Co,Mn;x=0,0.1,0.2,0.3,0.4,0.5)尖晶石/层状异质结构复合材料。借助X射线衍射、扫描电镜、差示扫描量热仪、恒电流间歇滴定技术和恒电流充放电测试表征手段对材料的晶体结构、微观形貌和电化学性能进行了研究。电化学性能结果表明:x=0.2材料的倍率性能和循环性能最佳,在2.7~4.3 V、1C下循环100次后,放电比容量为137 m A?h/g,容量保持率为93%;10C时的放电比容量为112 m A?h/g,相比于原始Li Ni_(1/3)Co_(1/3)Mn_(1/3)O_2材料在10C的放电比容量(95 m A?h/g)有较大提高。此外,快充慢放能力测试也证实了该材料的结构稳定,其在5C充、1C放的充放电机制下,循环100次后的放电比容量还能高达120 m A?h/g,容量保持率为87%。恒电流间歇滴定技术(GITT)的结果表明。x=0.2材料的D_(Li+)值比原始Li Ni_(1/3)Co_(1/3)Mn_(1/3)O_2材料的要高出一个数量级,说明尖晶石相的引入从根本上改善了材料的电化学性能。展开更多
通过静电纺丝法制备出一维纳米Li Ni1/3Co1/3Mn1/3O2纤维,根据扫描电子显微镜（SEM）、X射线衍射（XRD）、充放电实验,循环伏安法和交流阻抗法对纳米纤维的形貌、晶体结构和电化学性能进行研究.结果表明,纳米纤维的直径在150~300 nm之间...通过静电纺丝法制备出一维纳米Li Ni1/3Co1/3Mn1/3O2纤维,根据扫描电子显微镜（SEM）、X射线衍射（XRD）、充放电实验,循环伏安法和交流阻抗法对纳米纤维的形貌、晶体结构和电化学性能进行研究.结果表明,纳米纤维的直径在150~300 nm之间,且具有典型的α-Na Fe O2层状结构;所制备的Li Ni1/3Co1/3Mn1/3O2纳米纤维在0.5 C（85 m A/g）的倍率下循环30次容量保持率达到了94.1%;在倍率分别为0.1 C、0.2 C、0.5 C、1.0 C、2.0 C和0.2 C的充放电测试中,其比容量分别达到了157 m Ah/g、144 m Ah/g、134 m Ah/g、125 m Ah/g、115 m Ah/g和141 m Ah/g;在CV和EIS测试中,材料表现出优异的可逆性和循环稳定性.由于具有特殊的一维形貌,Li Ni1/3Co1/3Mn1/3O2纳米纤维表现出优异的电化学性能.展开更多
Layered P2–Na_(2/3)Ni_(1/3)Mn_(2/3)O_2 is a promising cathode material. It exhibits a high capacity and suitable operating voltage and undergoes a phase transition from P2 to O2 during charge/discharge.Researchers ha...Layered P2–Na_(2/3)Ni_(1/3)Mn_(2/3)O_2 is a promising cathode material. It exhibits a high capacity and suitable operating voltage and undergoes a phase transition from P2 to O2 during charge/discharge.Researchers have used Ti substitution to improve the cathode, yet the chemical principles that underpin elemental substitution and functional improvement remain unclear. To clarify these principles, we used in situ Raman spectroscopy to monitor chemical changes in P2–Na2/3 Ni1/3 Mn1/3 Ti1/3 O2 and P2–Na_(2/3)Ni_(1/3)Mn_(2/3)O_2 during charge/discharge. Based on the change in the A_(1g) and E_g peaks during charge/discharge, we concluded that Ti substitution compressed the transition metal layer and expanded the planar oxygen layer in the unit cell. Titanium stabilized the P2 phase structure, which improved the cycling stability of P2–NaNMT. Our results provide clear theoretical support for future research on modifying electrodes by elemental substitution.展开更多
Layered cathode material LiCo1/3Ni1/3Mn1/3O2 was synthesized by Pechini process, and investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM) and galvanostatic charge/discharge cycling. The sampl...Layered cathode material LiCo1/3Ni1/3Mn1/3O2 was synthesized by Pechini process, and investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM) and galvanostatic charge/discharge cycling. The sample is well-crystallized and has a phase-pure a-NaFeO2 structure. The particle sizes are uniform, and distributed in the range of 20-200 nm. The initial discharge capacity of the Li/LiCo1/3Ni1/3Mn1/3O2 cell was about 149 mAh·g-1 when it was cycled at a voltage range of 4.5-2.3 V with a specific current of 0.25 mA. The result is better in comparison with solid-state solution method. The synthetic procedure was discussed. Three major reactions: chelation, esterification, and polymerization successively occurred.展开更多
基金supported by the Special Project for the Central Government to Guide Local Technological Development (GUIKE ZY20198008)the Guangxi Technology Base and talent Subject (GUIKE AD20238012,AD20297086)+5 种基金the Natural Science Foundation of Guangxi Province (2021GXNSFDA075012)the National Natural Science Foundation of China (51902108,52104298,22169004)the National Natural Science Foundation of China (U20A20249)the Regional Innovation and Development Joint Fundthe Guangxi Innovation Driven Development Subject (GUIKE AA19182020,19254004)the Special Fund for Guangxi Distinguished Expert。
文摘Charging P2-Na_(2/3)Ni_(1/3)Mn_(2/3)O_(2)to 4.5 V for higher capacity is enticing.However,it leads to severe capacity fading,ascribing to the lattice oxygen evolution and the P2-O2 phase transformation.Here,the Mg Fe_(2)O_(4) coating and Mg,Fe co-doping were constructed simultaneously by Mg,Fe surface treatment to suppress lattice oxygen evolution and P2-O2 phase transformation of P2-Na_(2/3)Ni_(1/3)Mn_(2/3)O_(2)at deep charging.Through ex-situ X-ray diffraction(XRD)tests,we found that the Mg,Fe bulk co-doping could reduce the repulsion between transition metals and Na+/vacancies ordering,thus inhibiting the P2-O2 phase transition and significantly reducing the irreversible volume change of the material.Meanwhile,the internal electric field formed by the dielectric polarization of Mg Fe_(2)O_(4) effectively inhibits the outward migration of oxidized O^(a-)(a<2),thereby suppressing the lattice oxygen evolution at deep charging,confirmed by in situ Raman and ex situ XPS techniques.P2-Na NM@MF-3 shows enhanced high-voltage cycling performance with capacity retentions of 84.8% and 81.3%at 0.1 and 1 C after cycles.This work sheds light on regulating the surface chemistry for Na-layered oxide materials to enhance the high-voltage performance of Na-ion batteries.
文摘采用原位诱导法制备得到了一系列x Li M_2O_4?(1-x)Li Ni_(1/3)Co_(1/3)Mn_(1/3)O_2(M=Ni,Co,Mn;x=0,0.1,0.2,0.3,0.4,0.5)尖晶石/层状异质结构复合材料。借助X射线衍射、扫描电镜、差示扫描量热仪、恒电流间歇滴定技术和恒电流充放电测试表征手段对材料的晶体结构、微观形貌和电化学性能进行了研究。电化学性能结果表明:x=0.2材料的倍率性能和循环性能最佳,在2.7~4.3 V、1C下循环100次后,放电比容量为137 m A?h/g,容量保持率为93%;10C时的放电比容量为112 m A?h/g,相比于原始Li Ni_(1/3)Co_(1/3)Mn_(1/3)O_2材料在10C的放电比容量(95 m A?h/g)有较大提高。此外,快充慢放能力测试也证实了该材料的结构稳定,其在5C充、1C放的充放电机制下,循环100次后的放电比容量还能高达120 m A?h/g,容量保持率为87%。恒电流间歇滴定技术(GITT)的结果表明。x=0.2材料的D_(Li+)值比原始Li Ni_(1/3)Co_(1/3)Mn_(1/3)O_2材料的要高出一个数量级,说明尖晶石相的引入从根本上改善了材料的电化学性能。
文摘通过静电纺丝法制备出一维纳米Li Ni1/3Co1/3Mn1/3O2纤维,根据扫描电子显微镜（SEM）、X射线衍射（XRD）、充放电实验,循环伏安法和交流阻抗法对纳米纤维的形貌、晶体结构和电化学性能进行研究.结果表明,纳米纤维的直径在150~300 nm之间,且具有典型的α-Na Fe O2层状结构;所制备的Li Ni1/3Co1/3Mn1/3O2纳米纤维在0.5 C（85 m A/g）的倍率下循环30次容量保持率达到了94.1%;在倍率分别为0.1 C、0.2 C、0.5 C、1.0 C、2.0 C和0.2 C的充放电测试中,其比容量分别达到了157 m Ah/g、144 m Ah/g、134 m Ah/g、125 m Ah/g、115 m Ah/g和141 m Ah/g;在CV和EIS测试中,材料表现出优异的可逆性和循环稳定性.由于具有特殊的一维形貌,Li Ni1/3Co1/3Mn1/3O2纳米纤维表现出优异的电化学性能.
基金supported by the NSFC (21905239, 21925404, and 21775127)the Natural Science Foundation of Shanxi Province of China (201901D211265)the Scientific and Technological Innovation Programs of Higher Education Institutions in Shanxi (2019L0609)。
文摘Layered P2–Na_(2/3)Ni_(1/3)Mn_(2/3)O_2 is a promising cathode material. It exhibits a high capacity and suitable operating voltage and undergoes a phase transition from P2 to O2 during charge/discharge.Researchers have used Ti substitution to improve the cathode, yet the chemical principles that underpin elemental substitution and functional improvement remain unclear. To clarify these principles, we used in situ Raman spectroscopy to monitor chemical changes in P2–Na2/3 Ni1/3 Mn1/3 Ti1/3 O2 and P2–Na_(2/3)Ni_(1/3)Mn_(2/3)O_2 during charge/discharge. Based on the change in the A_(1g) and E_g peaks during charge/discharge, we concluded that Ti substitution compressed the transition metal layer and expanded the planar oxygen layer in the unit cell. Titanium stabilized the P2 phase structure, which improved the cycling stability of P2–NaNMT. Our results provide clear theoretical support for future research on modifying electrodes by elemental substitution.
基金the financial supports from the Natural Science Foundation of Hunan Province,China(No.2020JJ5102)the Scientific Research Fund of Hunan Provincial Education Department,China(No.19A111).
文摘Layered cathode material LiCo1/3Ni1/3Mn1/3O2 was synthesized by Pechini process, and investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM) and galvanostatic charge/discharge cycling. The sample is well-crystallized and has a phase-pure a-NaFeO2 structure. The particle sizes are uniform, and distributed in the range of 20-200 nm. The initial discharge capacity of the Li/LiCo1/3Ni1/3Mn1/3O2 cell was about 149 mAh·g-1 when it was cycled at a voltage range of 4.5-2.3 V with a specific current of 0.25 mA. The result is better in comparison with solid-state solution method. The synthetic procedure was discussed. Three major reactions: chelation, esterification, and polymerization successively occurred.
基金supported by the National Natural Science Foundation of China(Nos.51874196,51674164)the Program for Professor of Special Appointment at the Shanghai Institutions of Higher Learning,China(No.TP2020032)+2 种基金the Iron and Steel Joint Research Fund of the National Natural Science Foundation of China and China Baowu Steel Group Corp.Ltd.(No.U1860203)the Independent Research and Development Project of State Key Laboratory of Advanced Special Steel,Shanghai Key Laboratory of Advanced Ferrometallurgy,Shanghai University,China(No.SKLASS 2021-Z03)the Science and Technology Commission of Shanghai Municipality,China(Nos.21DZ1208900,19DZ2270200,20511107700)。
