LixNi0.5Co0.5O2的态密度计算及电化学性能研究

>为获得综合性能更好的锂离子二次电池正极材料, 分析了Co掺杂对Li_xNiO₂电化学性能的影响. 采用密度泛函DFT理论对Li_xNiO₂和Li_xNi_0.5Co_0.5O₂的平均放电电压和态密度进行了计算. 同时, 用共沉淀法制备了Li_xNiO₂和Li_xNi_0.5Co_0.5O₂锂离子二次电池正极材料, 并对其进行了XRD结构分析和恒流充放电测试. 实验和计算结果表明: 随锂离子嵌入正极(电池放电), 电池的电压逐渐降低, 材料的态密度峰向低能量方向移动; 与Li_xNiO₂相比, Li_xNi_0.5Co_0.5O₂的电压平台相对较高(当0.25≤x≤0.5), 而且在Li^＋嵌/脱时, Li_xNi_0.5Co_0.5O₂的结构变化相对较小; Co离子的掺入, 减小了NiO₆八面体的畸变度, 使材料的电化学稳定性得以提高. 在钴掺杂镍酸锂体系中, NiO₆和CoO₆具有相互的稳定作用.

Calculation on Density of States and Electrochemical Performance of LixNi0.5Co0.5O2

In order to improve the overall performance of the Li-ion secondary battery and analyze the effect of Co-dopping on the electrochemical performance of Li_xNiO₂ cathode, the average potential and density of states of Li_xNiO₂ and Li_xNi_0.5Co_0.5O₂ cathode materials for lithium battery were calculated under the framework of density functional theory. Meanwhile, the LiNiO₂ and LiNi_0.5Co_0.5O₂ materials were synthesized with coprecipitation method. The microstructure and electrochemical performance of the materials were characterized by XRD and galvanotatic cycling. The results of both of the tests and calculation showed that the potential was descended gradually and the density of states of the materials moved to the direction of low energy when Li ions intercalated the cathode materials (discharge). The average potential of Li_xNi_0.5Co_0.5O₂ was higher than that of Li_xNiO₂ (when 0.25≤x≤0.5), and when the Li ion intercalated/deintercalated the cathode, the change of the structure of LiNi_0.5Co_0.5O₂ was smaller than that of Li_xNiO₂. The distortion of the NiO₆ octahedral in Li_xNiO₂ was descended and the stability of microstructure of Li_xNiO₂ was heightened when Co was doped into Li_xNiO₂. CoO₆ and NiO₆ were mutually stabilized in Li_xNi_0.5Co_0.5O₂ material.