摘要
P2型层状材料Na_(0.66)Ni_(0.33)Ti_(0.67)O_2具有两对氧化还原峰,分别对应具有高电压的为Ni~(2+)/Ni~(4+)(约3.6V)和具有低电压的为Ti~(4+)/Ti~(3+)(约0.6V)~([1]),这种材料可同时作为正负极用于钠离子电池,具有电池制备集成简单、电位窗口稳定等优点。该材料作为正极时性能较差,本研究通过在Na_(0.66)Ni_(0.33)Ti_(0.67)O_2中Ti的格位处引入Li原子,成功地合成出新的纯相O3型层状化合物NaNi_(0.33)Li_(0.11)Ti_(0.56)O_2,有效地提高了其正极材料的性能。将合成的材料分别用作正负极,组装成了一种对称型钠离子全电池,具有3.0V的电压差和80 mA h g~(-1)充放电可逆容量(基于负极活性物质),循环性能优于通常报道基于于Na_(0.66)Ni_(0.33)Ti_(0.67)O_2的全电池性能。
P2-type layer Na_(0.66)Ni_(0.33)Ti_(0.67)O_2 is a promising active host as both anode and cathode material for symmetric sodium ion cell due to the electrochemical window between high-voltage redox couple Ni~(2+)/Ni~(4+)(about 3.6V) and the low-voltage redox couple Ti~(4+)/Ti~(3+)(about 0.6V). In this work, a new compound of O3-type NaNi_(0.33)Li_(0.11)Ti_(0.56)O_2 was proposed and synthesized by introducing Li atom into Ti sites in P2-type Na_(0.66)Ni_(0.33)Ti_(0.67)O_2. A symmetric sodium-ion cell based on the O3-type NaNi_(0.33)Li_(0.11)Ti_(0.56)O_2 was assembled and investigated. The cell exhibits a high voltage of 3.0 V and a reversible charge/discharge capacity of 80 mA h g~(-1). The electrochemical performance of the as proposed cell is superior to that of the symmetric cell based on P2-type Na_(0.66)Ni_(0.33)Ti_(0.67)O_2.
引文
[1]Shanmugam,R.;Lai,W.ECS Electrochemistry Letters 2014,3(4):A23-A25.