Ni2+替代对LiFePO4正极材料电化学性能的影响

利用炭热还原法合成了橄榄石型LiFe1-xNixPO4/C (x=0.0，0.1，0.3，0.5) 正极材料，并系统研究了Ni2+替代对材料电化学性能的影响。充放电循环、循环伏安和交流阻抗测试，结果表明Ni2+替代部分Fe2+可以显著改善LiFePO4材料的电化学性能。在0.2 C (1 C=170.0 mA·g-1)电流密度下，LiFe0.9Ni0.1PO4/C的放电比容量达到160 mAh·g-1。LiFe1-xNixPO4/C电化学性能的改善归因于材料电导率的提高和电荷传输电阻的降低。利用第一性原理对LiFe1-xNixPO4/C的电子结构进行了研究，结果表明Ni2+的铁位替代能够提高体系的电子电导性。LiFe0.875Ni0.125PO4的结构最稳定，带隙最小，导电性能最好

Effect of Ni2+ Substitution on the Electrochemical Performance of LiFePO4

LiFe1-xNixPO4/C (x=0.0, 0.1, 0.3, 0.5) cathode materials were synthesized by a carbothermal reduction technique and the effect of Ni2+ substitution on the electrochemical performances were systematically investigated. The results reveal that the cycle performance and electrochemical reversibility of LiFePO4 are remarkably improved with the substitution of Fe2+ ions by Ni2+ ions and LiFe0.9Ni0.1PO4/C demonstrates good electrochemical performances with discharge capacity of 160 mAh·g-1 at a discharge rate of 0.2 C (1 C=170.0 mA·g-1). The improvement of the reversible capacity and the high C-rate performance of LiFePO4 could be attributed to the enhancement of the electronic conductivity and the decrease of the charge transfer resistance. The first-principle calculations were employed to investigate the electronic structures of the LiFe1-xNixPO4/C composites. The Lattice parameters, total energies, density of states have were also studies in details. The results show that the electronic conductivity of the Ni2+-doped materials can be improved to certain extent. LiFe0.875Ni0.125PO4 has the most stable structure, the smallest band gap and the best conductivity