Multiwalled carbon nanotubes (MWNTs) were used as the conductive additive in the electrode materials. The electrochemical properties of supercapacitors based on LiNi0.8Co0.2O2 / MWNTs composite and LiNi0.8Co0.2O2/acet...Multiwalled carbon nanotubes (MWNTs) were used as the conductive additive in the electrode materials. The electrochemical properties of supercapacitors based on LiNi0.8Co0.2O2 / MWNTs composite and LiNi0.8Co0.2O2/acetylene black composite and MWNTs in 1.0 mol·L-1 LiClO4 / EC+DEC [V(EC)∶V(DEC)=1∶1] electrolyte were investigated by means of constant charge/discharge current tests, respectively. The experimental results show that the LiNi0.8Co0.2O2 / MWNTs composite has better performance than that of others, and the maximum specific capacitance of the supercapacitor can reach 271.6 F·g-1, while the energy density is up to 339.5 Wh·kg-1. Furthermore, it is remarkable that the performance of MWNTs is better than that of acetylene black as the conductive additive.展开更多
LiCoO2 gradient coated LiNi0.96Co0.04O2 material and iso-structure LiNi0.8Co0.2O2 material (the same molar ratio 8/2 of Ni/Co in the two materials) as cathode for lithium-ion batteries were synthesized with a co-preci...LiCoO2 gradient coated LiNi0.96Co0.04O2 material and iso-structure LiNi0.8Co0.2O2 material (the same molar ratio 8/2 of Ni/Co in the two materials) as cathode for lithium-ion batteries were synthesized with a co-precipitation method. Microstructure of iso-structure LiNi0.8Co0.2O2 were about the same as that of LiNiO2, and the structure of the coated material was much more similar to that of LiCoO2 based on the X-ray diffraction patterns. The cycling voltammetry and galvanostatic cycle tests show that the properties of the coated material were improved significantly. The first specific charge and discharge capacity for the coated material was 249.20 mAh·g-1 and 207.90 mAh·g-1 respectively, and the specific discharge capacity for the 100th cycle was still 186.02 mAh·g-1 with an irreversible loss of only 21.1 mAh·g-1. This showed that the new material had a good lithium intercalation-deintrercalation performance. Meanwhile, the mechanism of the sintering reaction was proposed. During the sintering reaction of the precursor with LiOH, the Li+-ion permeated into the body of precursors because the shape of the precursor particles was not changed basically based on scanning electronic microscopy. So, the layer microstructure of the precursor is important for the layer microstructure of lithium nickel cobalt oxides electrode material.展开更多
The gradient composite LiNi0.8Co0.2O2 was synthesized using spherical Ni(OH)2 particle coated by a sol-gel containing cobalt and lithium. The precursor was examined by DSC-TG. The gradient composite was characterized ...The gradient composite LiNi0.8Co0.2O2 was synthesized using spherical Ni(OH)2 particle coated by a sol-gel containing cobalt and lithium. The precursor was examined by DSC-TG. The gradient composite was characterized by SEM, EDS, XPS, XRD and ICP-AES. The XPS, EDS and ICP-AES results show that content of cobalt in the surface is higher than in the center of the spherical particle of the gradient composite. The first discharge specific capacity of the gradient composite sintered at 700 ℃ is 187.3 mAh·g-1.展开更多
The microwave coprecipitation method was used to synthesize α-Ni0.8Co0.2(OH)2 precursor for preparing LiNi0.8Co0.2O2 cathode material.The precursor α-Ni0.8Co0.2(OH)2 was mixed with LiOH·H2O and then calcined in...The microwave coprecipitation method was used to synthesize α-Ni0.8Co0.2(OH)2 precursor for preparing LiNi0.8Co0.2O2 cathode material.The precursor α-Ni0.8Co0.2(OH)2 was mixed with LiOH·H2O and then calcined in O2 for 10 h at different temperatures(700℃,800℃,900℃).XRD,SEM analyses and electrochemical tests were used to study the physical and electrochemical performance of the cathode material.With increasing calcination temperature,the characteristic peaks of the cathode materials became stronger and sharper,corresponding to a perfect crystalization.The results of electrochemical tests indicate that the sample LiNi0.8Co0.2O2 (900℃)showed excellent electrochemical properties,with an initial discharge capacity of 189.1 mA·h·g-1 and an initial discharge efficiency of 92.5%.After 30 cycles,the discharge capacity was still 148 mA·h·g-1,showing good cyclic stability.展开更多
文摘Multiwalled carbon nanotubes (MWNTs) were used as the conductive additive in the electrode materials. The electrochemical properties of supercapacitors based on LiNi0.8Co0.2O2 / MWNTs composite and LiNi0.8Co0.2O2/acetylene black composite and MWNTs in 1.0 mol·L-1 LiClO4 / EC+DEC [V(EC)∶V(DEC)=1∶1] electrolyte were investigated by means of constant charge/discharge current tests, respectively. The experimental results show that the LiNi0.8Co0.2O2 / MWNTs composite has better performance than that of others, and the maximum specific capacitance of the supercapacitor can reach 271.6 F·g-1, while the energy density is up to 339.5 Wh·kg-1. Furthermore, it is remarkable that the performance of MWNTs is better than that of acetylene black as the conductive additive.
文摘LiCoO2 gradient coated LiNi0.96Co0.04O2 material and iso-structure LiNi0.8Co0.2O2 material (the same molar ratio 8/2 of Ni/Co in the two materials) as cathode for lithium-ion batteries were synthesized with a co-precipitation method. Microstructure of iso-structure LiNi0.8Co0.2O2 were about the same as that of LiNiO2, and the structure of the coated material was much more similar to that of LiCoO2 based on the X-ray diffraction patterns. The cycling voltammetry and galvanostatic cycle tests show that the properties of the coated material were improved significantly. The first specific charge and discharge capacity for the coated material was 249.20 mAh·g-1 and 207.90 mAh·g-1 respectively, and the specific discharge capacity for the 100th cycle was still 186.02 mAh·g-1 with an irreversible loss of only 21.1 mAh·g-1. This showed that the new material had a good lithium intercalation-deintrercalation performance. Meanwhile, the mechanism of the sintering reaction was proposed. During the sintering reaction of the precursor with LiOH, the Li+-ion permeated into the body of precursors because the shape of the precursor particles was not changed basically based on scanning electronic microscopy. So, the layer microstructure of the precursor is important for the layer microstructure of lithium nickel cobalt oxides electrode material.
文摘The gradient composite LiNi0.8Co0.2O2 was synthesized using spherical Ni(OH)2 particle coated by a sol-gel containing cobalt and lithium. The precursor was examined by DSC-TG. The gradient composite was characterized by SEM, EDS, XPS, XRD and ICP-AES. The XPS, EDS and ICP-AES results show that content of cobalt in the surface is higher than in the center of the spherical particle of the gradient composite. The first discharge specific capacity of the gradient composite sintered at 700 ℃ is 187.3 mAh·g-1.
文摘The microwave coprecipitation method was used to synthesize α-Ni0.8Co0.2(OH)2 precursor for preparing LiNi0.8Co0.2O2 cathode material.The precursor α-Ni0.8Co0.2(OH)2 was mixed with LiOH·H2O and then calcined in O2 for 10 h at different temperatures(700℃,800℃,900℃).XRD,SEM analyses and electrochemical tests were used to study the physical and electrochemical performance of the cathode material.With increasing calcination temperature,the characteristic peaks of the cathode materials became stronger and sharper,corresponding to a perfect crystalization.The results of electrochemical tests indicate that the sample LiNi0.8Co0.2O2 (900℃)showed excellent electrochemical properties,with an initial discharge capacity of 189.1 mA·h·g-1 and an initial discharge efficiency of 92.5%.After 30 cycles,the discharge capacity was still 148 mA·h·g-1,showing good cyclic stability.
