用水热法制备LiFe_0.95M_0.05PO_4(M=Mg,Ni,Co),研究了掺杂对材料电化学性能的影响.结果表明,液相Fe位掺杂合成的LiFe_0.95M_0.05PO_4具有纯相橄榄石结构、结晶良好、粒径均匀;Fe位掺杂可增强材料的可逆性和导电性,提高其1C倍率下的电化学容量和循环稳定性;LiFe_0.95Mg_0.05PO_4,LiFe_0.95Mg_0.05PO_4和LiFe_0.95Mg_0.05PO_4三种材料的1C倍率首次放电比容量分别为133.1 mAh·g~(-1),128.4 mAh·g~(-1)和135.2 mAh·g~(-1);三种掺杂离子中Co~(2+)掺杂的效果最好,0.1C和1C倍率放电循环30次后的容量衰减率仅为5.7%和9.5%.
LiFe_0.95M_0.05PO_4 (M=Mg, Ni, Co) were synthesized by hydrothermal process with Fe-site doping in liquid phase. The samples of LiFe_0.95M_0.05PO_4 were characterized by XRD, FTIR and SEM methods. The effect of Fe-site doping on electrochemical properties of the samples was investigated. The results show that the electrochemical capacity and cyclic stability of LiFe_0.95M_0.05PO_4 at 1C are enhanced. Under 1C rate, the first discharge capacity of LiFe_0.95M_0.05PO_4, LiFe_0.95M_0.05PO_4 and LiFe_(0.95)M_(0.05)PO_4 exhibit 133.1 mAh·g~(-1),128.4 mAh·g~(-1) and 135.2 mAh·g~(-1),respectively. In three doping ions,the result of Co~(2+) doping is the best. The capacity fading rates of LiFe_0.95M_0.05PO_4 are 5.7% at 0.1C and 9.5% at 1C after 30 cycles. Such a significant improvement of electrochemical performance at 1C rate should be related to the enhancement of the reversibility and conductivity of LiFePO_4 doped by bivalent cation in Fe-site.
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