LiNi_(0.8)Co_(0.15)Al_(0.05)O_(2)@Cr_(2)O_(5)composite electrode combines the high rate-capability characteristics of NCA with the stability of Cr_(2)O_(5),playing a synergistic role in improving the cyclic stability,...LiNi_(0.8)Co_(0.15)Al_(0.05)O_(2)@Cr_(2)O_(5)composite electrode combines the high rate-capability characteristics of NCA with the stability of Cr_(2)O_(5),playing a synergistic role in improving the cyclic stability,initial discharge capacity and the security of low cut-off voltage(2.0 V).When the mass ratio of Cr_(2)O_(5)in NCA is 45%(mass),the capacity retention rate increases from 58.5% without Cr_(2)O_(5)to 69.3% in the range of 2.0-4.3 V.The initial discharge capacity of NCA@Cr_(2)O_(5)composite material is 211.4 mA·h·g^(-1),its first coulombic efficiency is 94.2%,and the charging capacity remains approximately constant when mixed with 15%(mass)Cr_(2)O_(5).The reason for the improvement of the initial charge-discharge efficiency(ICDE)was explained.Impedance and cyclic voltammetry analysis reveal more detailed reasons of the observed improvements.Compared with NCA cathode material,the NCA@Cr_(2)O_(5)composite material can provide not only additional stable sites and channels for Li^(+)insertion/extraction to make up for the loss of active Li^(+)sites and prevent the accumulation of Li+in the circulation process,but also protect the NCA electrode from the corrosion of the electrolyte decomposition by the Cr_(2)O_(5)nanoparticles adhering to NCA interface.展开更多
Safety is important to lithium ion battery materials. The thermal stability of LiFePO_4/C-LiMn_2O_4 blended cathode materials is characterized by using TG, XRD, and SEM etc. The results show that LiFePO_4/C-LiMn_2O_4 ...Safety is important to lithium ion battery materials. The thermal stability of LiFePO_4/C-LiMn_2O_4 blended cathode materials is characterized by using TG, XRD, and SEM etc. The results show that LiFePO_4/C-LiMn_2O_4 possesses a worse thermal stability than pure spinel LiMn_2O_4 and pure olivine LiFePO_4/C. When LiFePO_4/C-LiMn_2O_4 blended cathode materials are sintered at 500°C under Ar atmosphere, the sintered cathode materials emit O_2, and appear impurity phases(Li_3PO_4, Fe_2O_3, Mn_3O_4). It is deduced that some chemical reactions take place between different materials, which leads to a worse discharge specific capacity. LiFePO_4/C-LiMn_2O_4 blended cathode materials, therefore, need to be managed and controlled strictly for the sake of thermal stability and safety.展开更多
基金financially supported by the National Natural Science Foundation of China (52064031)the Program for Innovative Research Team in the University of Ministry of Education of China (IRT_17R48)National Natural Science Foundation of China (51674129)
文摘LiNi_(0.8)Co_(0.15)Al_(0.05)O_(2)@Cr_(2)O_(5)composite electrode combines the high rate-capability characteristics of NCA with the stability of Cr_(2)O_(5),playing a synergistic role in improving the cyclic stability,initial discharge capacity and the security of low cut-off voltage(2.0 V).When the mass ratio of Cr_(2)O_(5)in NCA is 45%(mass),the capacity retention rate increases from 58.5% without Cr_(2)O_(5)to 69.3% in the range of 2.0-4.3 V.The initial discharge capacity of NCA@Cr_(2)O_(5)composite material is 211.4 mA·h·g^(-1),its first coulombic efficiency is 94.2%,and the charging capacity remains approximately constant when mixed with 15%(mass)Cr_(2)O_(5).The reason for the improvement of the initial charge-discharge efficiency(ICDE)was explained.Impedance and cyclic voltammetry analysis reveal more detailed reasons of the observed improvements.Compared with NCA cathode material,the NCA@Cr_(2)O_(5)composite material can provide not only additional stable sites and channels for Li^(+)insertion/extraction to make up for the loss of active Li^(+)sites and prevent the accumulation of Li+in the circulation process,but also protect the NCA electrode from the corrosion of the electrolyte decomposition by the Cr_(2)O_(5)nanoparticles adhering to NCA interface.
基金supported by National Natural Science Foundation of China(Grant No.51364021)Natural Science Foundation of Yunnan Province(Grant No.2014FA025)+1 种基金Innovative Research Team in University of Ministry of Education of China(Grant No.IRT1250)Academician free exploration project of Yunnan Province(Grant No.14051600)
文摘Safety is important to lithium ion battery materials. The thermal stability of LiFePO_4/C-LiMn_2O_4 blended cathode materials is characterized by using TG, XRD, and SEM etc. The results show that LiFePO_4/C-LiMn_2O_4 possesses a worse thermal stability than pure spinel LiMn_2O_4 and pure olivine LiFePO_4/C. When LiFePO_4/C-LiMn_2O_4 blended cathode materials are sintered at 500°C under Ar atmosphere, the sintered cathode materials emit O_2, and appear impurity phases(Li_3PO_4, Fe_2O_3, Mn_3O_4). It is deduced that some chemical reactions take place between different materials, which leads to a worse discharge specific capacity. LiFePO_4/C-LiMn_2O_4 blended cathode materials, therefore, need to be managed and controlled strictly for the sake of thermal stability and safety.
