摘要
改善尖晶石锰酸锂的大倍率性能是目前锂离子电池的重点研究方向之一。本研究用高温固相法合成掺K^(+)的尖晶石锰酸锂,研究K^(+)提高锰酸锂倍率性能的微观机制。结果表明,尽管随着电流密度增大,电极的放电比容量下降,但掺K^(+)提高材料的大倍率性能效果显著,如最佳掺K^(+)量(物质的量分数)1.0%时,在10C (1C=150 mA·g^(-1))下比容量提高了一倍,远高于0.5C下的1.9%。原因在于掺K^(+)后,首先,锰酸锂的晶胞体积扩大,Li–O键变长,Li、Mn阳离子混排程度降低,载流子(Mn^(3+))量增多;其次,电极极化和电荷迁移阻抗降低,提高了材料的充放电可逆性、导电性及锂离子扩散能力;再者,[Mn_(2)]O_(4)骨架更稳定,减小了电化学过程中内应力变化,抑制了晶体结构变化和颗粒破碎;最后,钾离子掺杂使制备过程中材料团聚,从而减小电解液与电极的接触面积,减轻电解液的侵蚀,抑制锰的溶解。
Improving the high rate performance of lithium manganese spinel is one of the key research directions of Li-ion battery.In this study,spinel Li_(1.1–x)K_(x)Mn_(2)O_(4) (0≤x≤0.03) was synthesized by a high-temperature solid-state method.The results indicate that K^(+) doping significantly improved the high rate performance of the cathode,while the discharge specific capacity of the electrode decreased with the current density increasing.With the optimum doping amount of 1.0%(molar fraction) K^(+),the discharge specific capacity of the cathode increased by 102.8%at 10C (1C=150 mA·g^(-1)),much higher than that (1.9%) at 0.5C.It can be attributed to the following points:K^(+)doping can firstly expand the cell volume and the Li-O bond length,lower the cation mixing of Li/Mn,and increase the content of carriers (Mn^(3+)) of the material.Secondly,K^(+) doping can reduce the electrode polarization and charges transfer resistance,which develops the charge-discharge reversibility,electrical conductivity as well as the diffusion capability of the Li ions for the cathode.Thirdly,K^(+)doping can stabilize the framework of[Mn_(2)]O_(4),degrade the change of internal stress during the electrochemical process,which inhibits the modification of the crystal structure and particle fragmentation.In addition,the existence of K^(+)promotes the agglomeration of the material during the preparation process,which reduces the contact area between the electrolyte and cathode in cell,thereby alleviating the erosion of the electrolyte,as well as the Mn dissolution of the cathode.
作者
王洋
范广新
刘培
尹金佩
刘宝忠
朱林剑
罗成果
WANG Yang;FAN Guangxin;LIU Pei;YIN Jinpei;LIU Baozhong;ZHU Linjian;LUO Chengguo(School of Materials Science and Engineering,Henan Polytechnic University,Jiaozuo 454000,China;College of Chemistry and Chemical Engineering,Henan Polytechnic University,Jiaozuo 454000,China;Jiaozuo Banlv Nano Materials Engineering Co.,Ltd,Jiaozuo 454000,China)
出处
《无机材料学报》
SCIE
EI
CAS
CSCD
北大核心
2022年第9期1023-1029,I0010,I0011,共9页
Journal of Inorganic Materials
基金
国家自然科学基金(52071135,51871090,U1804135,51671080)
河南省科技创新人才计划(194200510019)
河南省教育委员会重点项目(19A150025)。
关键词
锂离子电池
正极材料
钾离子掺杂
微观机制
倍率性能
lithium-ion battery
cathode material
K^(+)doping
microscopic mechanism
rate performance
