0.5Li2MnO3-LiNi0.5Mn0.5O2的电化学行为及结构稳定性研究

Study on electrochemical behavior and structural stability of 0.5Li_2MnO_3-LiNi_(0.5)Mn_(0.5)O_2

对低温燃烧法合成的富锂锰基正极材料0.5Li2MnO3-LiNi0.5Mn0.5O2的充放电性能、充放电循环过程中Mn离子的价态变化、电化学阻抗变化以及正极材料的结构变化进行了系统的研究。研究结果表明,在开头的若干次充放电循环中,富锂锰基正极材料0.5Li2MnO3-LiNi0.5Mn0.5O2的放电比容量随循环次数的增加而增加,经过若干次循环后可以达到一个相当高的水平,其循环性能良好。以0.1 C在2.5～4.6 V之间充放电,放电比容量可达244 mAh/g,第50次循环,仍保有233 mAh/g。充放电过程中晶格中的Mn4+离子部分转变为Mn3+并参与电化学反应,这是造成放电比容量随循环次数增加而增加的原因,而显微结构和晶体结构保持稳定及电化学阻抗的降低是材料具有良好循环性能的原因。

The charger/discharge performance of the Li-rich Mn-based cathode material 0.5Li2MnO3-LiNi0.5Mn0.5O2 synthesized via low temperature combustion process, the valence change of Mn ions, the change of electrochemical impedance and structure of the cathode material during charge/discharge cycle process was systematically studied. The results show that the discharge capacity of the0.5Li2MnO3-LiNi0.5Mn0.5O2 increases with cycle number in the first several cycles, after a dozen cycles can reach a very high level, its cycle performance is excellent. Its 0.1 C discharge specific capacity is up to 244 mAh/g and still retains 233 mAh/g at 50th cycle when charged/discharged between 2.5-4.6 V. The Mn4＋ ions in the lattice partly transformed into Mn3＋ and participated in the following electrochemical reaction, which is the reason why discharge capacity increases with cycle number. The microstructure and crystal structure remains stable and the electrochemical impedance decrease during charge/discharge process, which is the reason why the cathode has excellent cycle performance.