The oxygen evolution behavior in overcharged LiNil/3COl/3Mnl/3Oz-based electrode was investigated by differ- ential scanning calorimetry and thermal gravimetric （DSC/TG）. Meantime, its thermal kinetic parameters wer...The oxygen evolution behavior in overcharged LiNil/3COl/3Mnl/3Oz-based electrode was investigated by differ- ential scanning calorimetry and thermal gravimetric （DSC/TG）. Meantime, its thermal kinetic parameters were calculated by Kissinger＇s and Ozawa＇s method. As observed by DSC/TG, two exothermic peaks at 239 and 313℃ in washed cathode （4.6 V）, were attributed to two steps of oxygen evolution. More importantly, the temperature of its oxygen release processes decreased obviously compared with that charged to 2.8 V. Activation energy （E） for the first and second oxygen evolution, both of which were assumed closely to be the first order reaction, between 200 and 350℃ in Lio.2o4NilnCol/3Mnl/3O2-based electrode were calculated as 113.63 and 158.13 kJ.mo1-1, respectively and the corresponding Arrhenius pre-exponential factors （A） of 1.05 × 10^11 and 6.46× 10^13 s-1 were also obtained. The different energy barrier of such two steps of oxygen evolution should probably be ascribed to the different bond energy of M--O （M=Mn, Co, Ni）.展开更多
Using oxalic acid and stoichiometrically mixed solution of NiCl2, CoCl2, and MnCl2 as starting materials, the triple oxalate precursor of nickel, cobalt, and manganese was synthesized by liquid-phase co-precipitation ...Using oxalic acid and stoichiometrically mixed solution of NiCl2, CoCl2, and MnCl2 as starting materials, the triple oxalate precursor of nickel, cobalt, and manganese was synthesized by liquid-phase co-precipitation method. And then the LiNi1/3Co1/3Mn1/3O2 cathode materials for Li-ion battery were prepared from the precursor and LiOH·H2O by solid-state reaction. The precursor and LiNi1/3Co1/3Mn1/3O2 were characterized by chemical analysis, XRD, EDX, SEM and TG-DTA. The results show that the composition of precursor is Ni1/3Co1/3Mn1/3C2O4·2H2O. The product LiNi1/3Co1/3Mn1/3O2, in which nickel, cobalt and manganese are uniformly distributed, is well crystallized with a-NaFeO2 layered structure. Sintering temperature has a remarkable influence on the electrochemical performance of obtained samples. LiNi1/3Co1/3Mn1/3O2 synthesized at 900 ℃ has the best electrochemical properties. At 0.1C rate, its first specific discharge capacity is 159.7 mA·h/g in the voltage range of 2.75-4.30 V and 196.9 mA·h/g in the voltage range of 2.75-4.50 V; at 2C rate, its specific discharge capacity is 121.8 mA·h/g and still 119.7 mA·h/g after 40 cycles. The capacity retention ratio is 98.27%.展开更多
LiNi1/3Co1/3Mn1/3O2 and Ce-doped LiNi1/3Co1/3Mn1/3O2 cathode materials were synthesized by a co-precipitation method and solid phase synthesis and characterized using X-ray diffraction(XRD) and scanning electron micro...LiNi1/3Co1/3Mn1/3O2 and Ce-doped LiNi1/3Co1/3Mn1/3O2 cathode materials were synthesized by a co-precipitation method and solid phase synthesis and characterized using X-ray diffraction(XRD) and scanning electron microscopy(SEM).The results indicated that the resultant cathode materials with different Ce content all had a good layer structure and high crystallinity.Electrochemical performance testing of the cathode materials showed that the discharge capacity increased with increasing Ce content while the initial reversible capacity attenuation decreased with Ce doping.When the Ce content of the cathode materials is x=0.2,and the current charge and discharge rate is a constant 0.2 C,the discharge capacity maintained 91% of its initial capacity after cycling 50 times.展开更多
基金Project supported by the National Natural Science Foundation of China （No. 50542004） and Graduate Degree Thesis Innovation Foundation of Central South University （No. 1960-71131100017）.
文摘The oxygen evolution behavior in overcharged LiNil/3COl/3Mnl/3Oz-based electrode was investigated by differ- ential scanning calorimetry and thermal gravimetric （DSC/TG）. Meantime, its thermal kinetic parameters were calculated by Kissinger＇s and Ozawa＇s method. As observed by DSC/TG, two exothermic peaks at 239 and 313℃ in washed cathode （4.6 V）, were attributed to two steps of oxygen evolution. More importantly, the temperature of its oxygen release processes decreased obviously compared with that charged to 2.8 V. Activation energy （E） for the first and second oxygen evolution, both of which were assumed closely to be the first order reaction, between 200 and 350℃ in Lio.2o4NilnCol/3Mnl/3O2-based electrode were calculated as 113.63 and 158.13 kJ.mo1-1, respectively and the corresponding Arrhenius pre-exponential factors （A） of 1.05 × 10^11 and 6.46× 10^13 s-1 were also obtained. The different energy barrier of such two steps of oxygen evolution should probably be ascribed to the different bond energy of M--O （M=Mn, Co, Ni）.
文摘Using oxalic acid and stoichiometrically mixed solution of NiCl2, CoCl2, and MnCl2 as starting materials, the triple oxalate precursor of nickel, cobalt, and manganese was synthesized by liquid-phase co-precipitation method. And then the LiNi1/3Co1/3Mn1/3O2 cathode materials for Li-ion battery were prepared from the precursor and LiOH·H2O by solid-state reaction. The precursor and LiNi1/3Co1/3Mn1/3O2 were characterized by chemical analysis, XRD, EDX, SEM and TG-DTA. The results show that the composition of precursor is Ni1/3Co1/3Mn1/3C2O4·2H2O. The product LiNi1/3Co1/3Mn1/3O2, in which nickel, cobalt and manganese are uniformly distributed, is well crystallized with a-NaFeO2 layered structure. Sintering temperature has a remarkable influence on the electrochemical performance of obtained samples. LiNi1/3Co1/3Mn1/3O2 synthesized at 900 ℃ has the best electrochemical properties. At 0.1C rate, its first specific discharge capacity is 159.7 mA·h/g in the voltage range of 2.75-4.30 V and 196.9 mA·h/g in the voltage range of 2.75-4.50 V; at 2C rate, its specific discharge capacity is 121.8 mA·h/g and still 119.7 mA·h/g after 40 cycles. The capacity retention ratio is 98.27%.
文摘LiNi1/3Co1/3Mn1/3O2 and Ce-doped LiNi1/3Co1/3Mn1/3O2 cathode materials were synthesized by a co-precipitation method and solid phase synthesis and characterized using X-ray diffraction(XRD) and scanning electron microscopy(SEM).The results indicated that the resultant cathode materials with different Ce content all had a good layer structure and high crystallinity.Electrochemical performance testing of the cathode materials showed that the discharge capacity increased with increasing Ce content while the initial reversible capacity attenuation decreased with Ce doping.When the Ce content of the cathode materials is x=0.2,and the current charge and discharge rate is a constant 0.2 C,the discharge capacity maintained 91% of its initial capacity after cycling 50 times.
