以硝酸盐为原料,采用共沉淀法制备出Li Ni0.8Co0.15Al0.05O2正极材料,研究了反应温度对材料的结构以及电化学性能的影响。结果表明:烧结温度对晶体结构的完整性以及晶粒尺寸有很大的影响,温度过低时,无法形成完整的层状结构,阳离子混排...以硝酸盐为原料,采用共沉淀法制备出Li Ni0.8Co0.15Al0.05O2正极材料,研究了反应温度对材料的结构以及电化学性能的影响。结果表明:烧结温度对晶体结构的完整性以及晶粒尺寸有很大的影响,温度过低时,无法形成完整的层状结构,阳离子混排严重;温度太高,晶体生长过快,晶粒尺寸粗大,晶格常数变小,不利于充放电循环时锂离子的脱嵌,造成容量的损失。在500℃预烧结、800℃烧结时获得的材料具有最好结构性能以及电化学性能,0.1 C首次放电比容量为186.8 m Ah/g,5 C下仍能保持107.4 m Ah/g,具有优异的循环性能以及倍率性能。展开更多
The co-precipitation derived LiNi_(0.8)Co_(0.15)Al_(0.05)O_2 cathode material was modified by a coating layer of TiP_2O_7 through an ethanol-based process. The TiP_2O_7-coated LiNi_(0.8)Co_(0.15)Al_(0.05)O_2 is charac...The co-precipitation derived LiNi_(0.8)Co_(0.15)Al_(0.05)O_2 cathode material was modified by a coating layer of TiP_2O_7 through an ethanol-based process. The TiP_2O_7-coated LiNi_(0.8)Co_(0.15)Al_(0.05)O_2 is characterized by Xray diffraction analysis, scanning electron microscopy and transmission electron microscopy to investigate the microstructure and morphology. The differential scanning calorimetry was employed to confirm the improved thermal stability. The electrochemical properties were evaluated by the constant-current charge/discharge tests. The TiP_2O_7 coating layer is effectively suppressing the structural degradation and ameliorating the surface status of LiNi_(0.8)Co_(0.15)Al_(0.05)O_2 particles, and the intrinsic rhombohedral layered structure of TiP_2O_7-coated LiNi_(0.8)Co_(0.15)Al_(0.05)O_2 was well maintained during the long-term cycling process, while the surface structure of pristine LiNi_(0.8)Co_(0.15)Al_(0.05)O_2 was degraded from rhombohedral R3 m layered structure to cubic rock-salt structure. The charged state Ni^(4+) ions will easily transform into Ni^(2+) when the electrolytes oxidized at the interface of cathode/electrolytes and formed the cubic rock-salt NiO type structure, and the cubic rock-salt structure without electrochemical activity on the surface of LiNi_(0.8)Co_(0.15)Al_(0.05)O_2 particles will finally accelerate capacity fading. The thermal stability and cyclic performances of the LiNi_(0.8)Co_(0.15)Al_(0.05)O_2 electrode were remarkably improved by TiP_2O_7 coating, the total amount of heat release corresponding to the intensity of thermal runaway were 1075.5 and 964.6 J/g for pristine LiNi_(0.8)Co_(0.15)Al_(0.05)O_2 and TiP_2O_7-coated LiNi_(0.8)Co_(0.15)Al_(0.05)O_2 respectively, the pouch shaped full cells that employed TiP 2 O7-coated LiNi_(0.8)Co_(0.15)Al_(0.05)O_2 as cathode were able to perform more than 2200 cycles at 25 ℃ and more than 1000 cycles at 45 ℃ before the capacity retention fading to 80%.展开更多
文摘以硝酸盐为原料,采用共沉淀法制备出Li Ni0.8Co0.15Al0.05O2正极材料,研究了反应温度对材料的结构以及电化学性能的影响。结果表明:烧结温度对晶体结构的完整性以及晶粒尺寸有很大的影响,温度过低时,无法形成完整的层状结构,阳离子混排严重;温度太高,晶体生长过快,晶粒尺寸粗大,晶格常数变小,不利于充放电循环时锂离子的脱嵌,造成容量的损失。在500℃预烧结、800℃烧结时获得的材料具有最好结构性能以及电化学性能,0.1 C首次放电比容量为186.8 m Ah/g,5 C下仍能保持107.4 m Ah/g,具有优异的循环性能以及倍率性能。
基金supported by the National Natural Science Foundation of China (No. 51372178)the Natural Science Foundation for Distinguished Young Scholars of Hubei Province of China (No. 2013CFA021)
文摘The co-precipitation derived LiNi_(0.8)Co_(0.15)Al_(0.05)O_2 cathode material was modified by a coating layer of TiP_2O_7 through an ethanol-based process. The TiP_2O_7-coated LiNi_(0.8)Co_(0.15)Al_(0.05)O_2 is characterized by Xray diffraction analysis, scanning electron microscopy and transmission electron microscopy to investigate the microstructure and morphology. The differential scanning calorimetry was employed to confirm the improved thermal stability. The electrochemical properties were evaluated by the constant-current charge/discharge tests. The TiP_2O_7 coating layer is effectively suppressing the structural degradation and ameliorating the surface status of LiNi_(0.8)Co_(0.15)Al_(0.05)O_2 particles, and the intrinsic rhombohedral layered structure of TiP_2O_7-coated LiNi_(0.8)Co_(0.15)Al_(0.05)O_2 was well maintained during the long-term cycling process, while the surface structure of pristine LiNi_(0.8)Co_(0.15)Al_(0.05)O_2 was degraded from rhombohedral R3 m layered structure to cubic rock-salt structure. The charged state Ni^(4+) ions will easily transform into Ni^(2+) when the electrolytes oxidized at the interface of cathode/electrolytes and formed the cubic rock-salt NiO type structure, and the cubic rock-salt structure without electrochemical activity on the surface of LiNi_(0.8)Co_(0.15)Al_(0.05)O_2 particles will finally accelerate capacity fading. The thermal stability and cyclic performances of the LiNi_(0.8)Co_(0.15)Al_(0.05)O_2 electrode were remarkably improved by TiP_2O_7 coating, the total amount of heat release corresponding to the intensity of thermal runaway were 1075.5 and 964.6 J/g for pristine LiNi_(0.8)Co_(0.15)Al_(0.05)O_2 and TiP_2O_7-coated LiNi_(0.8)Co_(0.15)Al_(0.05)O_2 respectively, the pouch shaped full cells that employed TiP 2 O7-coated LiNi_(0.8)Co_(0.15)Al_(0.05)O_2 as cathode were able to perform more than 2200 cycles at 25 ℃ and more than 1000 cycles at 45 ℃ before the capacity retention fading to 80%.
