State Key Lab of Physical Chemistry of Solid Surfaces, College of Chemistry and Chemical Engineering, Collaborative Innovation Center of Chemistry for Energy Materials, State-Province Joint Engineering Laboratory of Power Source Technology for New Energy Vehicle, Xiamen University , Xiamen, 361005 Fujian, China.
College of Energy, Xiamen University , Xiamen, 361102 Fujian, China.
ACS Appl Mater Interfaces. 2016 Aug 10;8(31):20147-56. doi: 10.1021/acsami.6b06976. Epub 2016 Jul 28.
The layer-structured LiNi0.5Co0.2Mn0.3O2 (L523) with high specific capacity and the spinel LiMn2O4 (LMO) with excellent thermostability complement each other in a blended cathode for better heat stability and electrochemical performance. The delithiated LMO starts to react with electrolyte at 160-200 °C to cause structural instability, and the delithiated L523 generates massive heat when its temperature is raised above 275 °C with the electrolyte present, but we found that the blended cathode shows a remarkable improvement in thermal stability since the reaction at 160-200 °C between LMO and the electrolyte disappears, and the total heat generated from the reaction between L523 and the electrolyte is drastically reduced. The reaction between LMO and the electrolyte at 160-200 °C causes structural instability of LMO as a self-accelerating attack from HF. With L523 present, this reaction is eliminated because the H(+) from HF and Li(+) in L523 undergo exchange reaction to prevent further generation of HF. The presence of LMO, however, reduces the total heat generated by L523 reacting with the electrolyte at high temperature. This thermal synergy between LMO and L523 not only improves the thermal safety of the blended cathode but also preserves their structures for better electrochemical performance.
层状 LiNi0.5Co0.2Mn0.3O2（L523）具有高比容量，尖晶石 LiMn2O4（LMO）具有优异的热稳定性，将两者共混作为正极可以提高热稳定性和电化学性能。脱锂的 LMO 在 160-200°C 与电解液开始反应，导致结构不稳定；而当存在电解液时，脱锂的 L523 温度升高到 275°C 以上会产生大量热量，但我们发现共混正极的热稳定性有显著提高，因为 LMO 与电解液在 160-200°C 之间的反应消失了，而且 L523 与电解液之间反应产生的总热量大大减少。LMO 与电解液在 160-200°C 之间的反应导致 LMO 结构不稳定，这是 HF 自加速攻击的结果。由于 L523 的存在，这种反应被消除了，因为 HF 中的 H(+)和 L523 中的 Li(+)进行了交换反应，防止了 HF 的进一步生成。然而，LMO 的存在减少了 L523 在高温下与电解液反应产生的总热量。LMO 和 L523 之间的这种热协同作用不仅提高了共混正极的热安全性，而且还保持了它们的结构，以实现更好的电化学性能。
