A Three in One Strategy to Achieve Zirconium Doping, Boron Doping, and Interfacial Coating for Stable
Ze Feng1, Ranjusha Rajagopalan1, Shan Zhang1
1Hunan Provincial Key Laboratory of Chemical Power Sources Hunan Provincial Key Laboratory of Efficient and Clean Utilization of Manganese Resources College of Chemistry and Chemical Engineering Central South University Changsha 410083 P. R. China.
Abstract:
LiNi0.8Co0.1Mn0.1O2 cathodes suffer from severe bulk structural and interfacial degradation during battery operation. To address these issues, a three in one strategy using ZrB2 as the dopant is proposed for constructing a stable Ni-rich cathode. In this strategy, Zr and B are doped into the bulk of LiNi0.8Co0.1Mn0.1O2, respectively, which is beneficial to stabilize the crystal structure and mitigate the microcracks. Meanwhile, during the high-temperature calcination, some of the remaining Zr at the surface combined with the surface lithium source to form lithium zirconium coatings, which physically protect the surface and suppress the interfacial phase transition upon cycling. Thus, the 0.2 mol% ZrB2-LiNi0.8Co0.1Mn0.1O2 cathode delivers a discharge capacity of 183.1 mAh g-1 after 100 cycles at 50 °C (1C, 3.0-4.3 V), with an outstanding capacity retention of 88.1%. The cycling stability improvement is more obvious when the cut-off voltage increased to 4.4 V. Density functional theory confirms that the superior structural stability and excellent thermal stability are attributed to the higher exchange energy of Li/Ni exchange and the higher formation energy of oxygen vacancies by ZrB2 doping. The present work offers a three in one strategy to simultaneously stabilize the crystal structure and surface for the Ni-rich cathode via a facile preparation process.
