超高镍三元正极材料LiNi_(0.9)Co_(0.05)Mn_(0.05)O_(2)的制备及改性研究

Preparation and Modification of Ultra-High Nickel Ternary Cathode Material LiNi_(0.9)Co_(0.05)Mn_(0.05)O_(2)

采用简易的共沉淀及随后的高温固相烧结法成功合成出了不同Zr掺杂量的NCM90(LiNi_(x)Co_(y)Mn_(1-x-y)O_(2),x≥0.9)单晶正极材料。研究结果表明,掺入晶体结构中具有电化学惰性的Zr同时进入锂层及过渡金属层。一方面,进入到锂层的Zr有效地拓宽了层间距,加速循环过程中锂离子的扩散;另一方面,进入过渡金属层的Zr通过与晶格氧的键合作用,形成具有较高键能的Zr-O键,有效稳定材料晶体结构。与所预期一致,改性材料展现出了较为优越的循环稳定性,其中掺杂0.5%Zr得到的LiNi_(0.9)Co_(0.05)Mn_(0.05)O_(2)-0.5%Zr(NCM90-Zr2)电化学性能最优。NCM90-Zr2在2.95~4.30 V电压范围内、1C倍率下循环200周后,容量保持率为74.1%;进一步提升截止电压至4.50V,材料释放出215.5 mAh·g^(-1)的初始放电比容量,循环100周后,仍保持初始容量的86.9%,表现出优异的高压稳定性。本研究为后续锂离子电池高电压正极材料的发展提供了一定的借鉴。

Single-crystal cathode materials NCM90(LiNi_(x)Co_(y)Mn_(1-x-y)O_(2),x≥0.9)with different Zr doping contents were successfully synthesized by a facile co-precipitation and subsequent high-temperature solid-phase sintering method.The results show that the electrochemically inert Zr incorporated into the crystal structure enters both the lithium layer and the transition metal layer.On the one hand,the Zr entering the lithium layer effectively widens the interlayer spacing and accelerates the diffusion of lithium ions during cycling;on the other hand,the Zr entering the transition metal layer forms a higher bond through the bonding with the lattice oxygen.The active Zr-O bond can effectively stabilize the crystal structure of the material.As expected,the modified materials exhibit superior cycling stability,LiNi_(0.9)Co_(0.05)Mn_(0.05)O_(2)-0.5%Zr(NCM90-Zr2)doped with 0.5%Zr has the best electrochemical performance.The capacity retention of NCM90-Zr2 is 74.1%after 200 cycles in the voltage range of 2.95-4.30 V at a rate of 1C;further increasing the cut-off voltage to 4.50 V,the material releases an initial discharge specific capacity of 215.5 mAh··g^(-1).It maintains 86.9%of the initial capacity after 100 cycles,showing excellent high-pressure stability.This study provides a certain reference for the subsequent development of high-voltage cathode materials for lithium-ion batteries.