压电材料K_(0.5)Na_(0.5)NbO_(3)表面修饰高镍正极材料LiNi_(0.83)Co_(0.12)Mn_(0.05)O_(2)的电化学性能研究

Study on Electrochemical Performance of Surface-modified Nickel-rich Cathode Material LiNi_(0.83)Co_(0.12)Mn_(0.05)O_(2) by Piezoelectric Material K_(0.5)Na_(0.5)NbO_(3)

采用原位包覆法制备压电材料K_(0.5)Na_(0.5)NbO_(3)(KNN)表面修饰高镍正极材料LiNi_(0.83)Co_(0.12)Mn_(0.05)O_(2),并对其进行电化学性能研究。XRD图谱表明,KNN表面修饰样品并未改变高镍正极材料的层状结构。通过XRD结构精修也证实了KNN的存在且本体材料的晶体结构未受影响。EDS面扫描结果表明,KNN已成功地包覆在高镍正极材料的表面。电化学性能测试结果表明,在2.8~4.3 V电压范围内,0.1 C倍率下改性样品KNN@NCM83的初始放电比容量升高;循环100圈后,改性样品仍保持157.8 mA·h/g的放电比容量,容量保持率为82.3%,而原始样品NCM83仅保持133.6 mA·h/g的放电比容量,容量保持率为75.2%。与原始样品相比,KNN@NCM83表现出了更优异的倍率性能,在5 C和10 C倍率下的放电比容量分别为155.6、148.6 mA·h/g,表明KNN能有效提高高镍正极材料的Li^(+)传输效率,进而提高样品的倍率性能。EIS测试结果表明,在充放电循环后KNN@NCM83电极表面生成的固体电解质界面膜(CEI膜)薄而稳定且电荷迁移阻抗较小,充分说明改性样品的结构稳定,可逆性良好。

The piezoelectric material K_(0.5)Na_(0.5)NbO_(3)(KNN)surface-modified nickel-rich cathode material LiNi_(0.83)Co_(0.12)Mn_(0.05)O_(2)was prepared by in-situ coating,and the electrochemical performance of the as-prepared material was also studied.The XRD pattern shows that the sample modified with KNN does not change the layered structure of the nickel-rich cathode material.The XRD refinement results also confirm the existence of KNN by which the crystal structure of the bulk material is not affected.Meanwhile,the EDS Mapping analysis demonstrates that KNN has successfully coated the surface of the nickel-rich ca-thode material.Based on the measured electrochemical performance,in the voltage range of 2.8~4.3 V,the initial discharge specific capacity of the modified sample KNN@NCM83 increases at 0.1 C rate.More-over,after 100 cycles,the modified sample still maintains a discharge specific capacity of 157.8 mA·h/g with a capacity retention rate of 82.3%,while the pristine sample NCM83 only maintains a discharge specific capacity of 133.6 mA·h/g with a capacity retention rate of 75.2%.Compared with the pristine sample,KNN@NCM83 presents a better rate performance and particularly,its specific discharge capacity reaches 155.6 mA·h/g and 148.6 mA·h/g respectively at 5 C and 10 C.This indicates that KNN could effectively improve the Li^(+)transmission efficiency of the nickel-rich cathode material,which could improve the rate performance of the sample in turn.The EIS test results show that the solid electrolyte interface film(CEI film)generated on the surface of KNN@NCM83 electrode after cycling is thin and stable with low charge transfer resistance,which fully demonstrates that the modified sample has a stable structure and good reversibility.