TiP2O7 -coated LiNi0.8Co0.15Al0.05O2 cathode materials with improved thermal stability and superior cycle life

• 作者: Guan Wu Yingke Zhou
• 来源期刊: 能源化学
• 年，卷（期）: 2019,（1）
• 页码范围: 151-159
• 页数: 9页
• 语种: 英文

摘要

The co-precipitation derived LiNi0.8Co0.15Al0.05O2 cathode material was modified by a coating layer of TiP2O7 through an ethanol-based process. The TiP2O7 -coated LiNi0.8Co0.15Al0.05O2 is characterized by X-ray diffraction analysis, scanning electron microscopy and transmission electron microscopy to investi-gate 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 TiP2O7 coating layer is effectively suppressing the structural degradation and ameliorating the surface status of LiNi0.8Co0.15Al0.05O2 particles, and the intrinsic rhombohedral layered structure of TiP2O7 -coated LiNi0.8Co0.15Al0.05O2 was well maintained during the long-term cycling pro-cess, while the surface structure of pristine LiNi0.8Co0.15Al0.05O2 was degraded from rhombohedral R3m layered structure to cubic rock-salt structure. The charged state Ni4 ions will easily transform into Ni2 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 LiNi0.8Co0.15Al0.05O2 particles will finally accelerate capacity fading. The thermal stability and cyclic per-formances of the LiNi0.8Co0.15Al0.05O2 electrode were remarkably improved by TiP2O7 coating, the total amount of heat release corresponding to the intensity of thermal runaway were 1075.5 and 964.6 J/g for pristine LiNi0.8Co0.15Al0.05O2 and TiP2O7 -coated LiNi0.8Co0.15Al0.05O2 respectively, the pouch shaped full cells that employed TiP2O7 -coated LiNi0.8Co0.15Al0.05O2 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%.