锂离子电池正极材料Li_2FeSiO_4的改性

Modification of Li_2FeSiO_4 cathode for lithium-ion batteries

采用高温固相反应法在氩气气氛下合成锂离子电池正极材料Li2FeSiO4、Li2FeSiO4/C和Li2Fe0.9Mn0.1SiO4/C,并采用X线衍射、扫描电镜和电化学方法研究材料的结构与性能。研究结果表明:改性后的Li2FeSiO4/C和Li2Fe0.9Mn0.1SiO4/C材料与Li2FeSiO4具有相同的晶体结构,锰离子掺杂和表面碳包覆有效地提高了材料的比容量和循环性能。以C/16倍率充放电,Li2FeSiO4/C的首次放电容量为112 mA.h/g,与Li2FeSiO4相比增加了34.9%,充放电循环30次后容量衰减为14%;而复合掺杂得到的Li2Fe0.9Mn0.1SiO4/C材料首次放电容量达122 mA.h/g,充放电循环30次后容量衰减仅为9%。

Lithium iron orthosilicate cathode materials Li2FeSiO4,Li2FeSiO4/C and Li2Fe0.9Mn0.1SiO4/C were synthesized by solid-state reaction in an argon atmosphere,and the samples were characterized by X-ray diffraction（XRD）,scanning electron micrograph（SEM） and electrochemical measurements.The results show that Li2FeSiO4,Li2FeSiO4/C and Li2Fe0.9Mn0.1SiO4/C are of the similar crystal structure.The capacity and cycling performances of 1ithium iron orthosilicate cathodes are improved by manganese doping and carbon coating.The Li2FeSiO4/C has an initial discharge capacity of 112 mA·h/g at C/16 current rate,which is 34.9% higher than that of Li2FeSiO4,and the capacity decays 14% after 30 cycles.However,Li2Fe0.9Mn0.1SiO4/C delivers an initial discharge capacity of 122 mA·h/g and the capacity only decays 9% after 30 cycles.