镁掺杂协同氧化铝包覆优化锂离子电池高镍正极材料

Optimization of high nickel cathode materials for lithium ion batteries by magnesium doped heterogeneous aluminum oxide coating

锂离子电池高镍Li Ni_(x)Co_(y)Mn_(1-x-y)O_(2)(NCM,x≥0.6)正极材料因具有较高的能量密度和低成本等优势在电池领域备受关注,然而随着镍含量的升高,材料锂镍混排严重且热稳定性下降,导致高镍三元材料的循环稳定性和安全性恶化。本研究针对高镍三元材料阳离子无序排列严重和循环稳定性差的问题,通过共沉淀法在前驱体合成过程中将Mg掺杂进入晶体,得到Li Ni_(0.8)Co_(0.1)Mn_(0.09)Mg_(0.01)O_(2)(Mg1.0)活性材料,进一步利用液相法在材料表面包覆Al_(2)O_(3),成功制备Al_(2)O_(3)涂覆的Li Ni_(0.8)Co_(0.1)Mn_(0.09)Mg_(0.01)O_(2)复合材料(Mg1.0@Al)。X射线衍射(XRD)结果表明,Mg掺杂能够有效扩大材料层间距,抑制阳离子混排;扫描电子显微镜(SEM)结合透射电子显微镜(TEM)结果表明,改性未对NCM811材料整体形貌造成影响,同时能够明显地观察到通过液相法在材料表面包覆的Al_(2)O_(3)涂层。电化学测试结果表明,镁铝协同改性可以稳定NCM811材料结构,减少阴极的界面极化,遏制材料与电解液发生副反应,使得材料表现出优越的电化学性能。Mg1.0@Al在1 C循环100次后表现出稳定的放电电压(ΔV=5.2 m V)、较低的电荷转移阻抗(R_(ct)=51.66Ω)和卓越的锂离子扩散系数(D_(Li)=4.05×10^(-14)cm^(2)/s)。同时,Mg1.0@Al材料在2.8~4.3V电压范围下,展现出卓越的循环性能和倍率性能:1 C下循环100次和400次后仍有188.58 m Ah/g和147.47 m Ah/g的放电比容量,容量保持率分别为95.18%和74.54%;5 C大倍率电流下,放电比容量高达146.3 m Ah/g。

LiNi_(x)Co_(y)Mn_(1-x-y)O_(2)(NCM,x≥0.6)cathode materials have piqued much interest in Lithiumion battery because of their high energy density and low-cost.However,the lithium-nickel cations mixed arrangement became serious,and thermal stability decreases as nickel content increases,resulting in deterioration of cycling stability and safety concerns.This paper successfully doped the Mg into NCM using co-precipitation method,followed by Al_(2)O_(3)coating.The as-prepared LiNi_(0.8)Co_(0.1)Mn_(0.09)Mg_(0.01)O_(2)@Al_(2)O_(3)(Mg1.0@Al)X-ray diffraction,scanning electron microscopy,and transmission electron microscopy results show that Mg doping can effectively expand the spacing in the crystalline as well as buffer cation mixing.Meanwhile,the Al_(2)O_(3)coating protects the crystals from the cathode-electrolyte side reaction.The electrochemical measurements revealed that the synergistic effects of Mg doping and Al_(2)O_(3)coating can help to stabilize the crystal structure and reduce interfacial polarization.The Mg1.0@Al demonstrated stable discharge voltage(ΔV=5.2 mV),low charge transfer impedance(R_(ct)=51.66Ω)and excellent lithium-ion diffusion coefficient(D_(Li)=4.05×10^(-14)cm^(2)/s)after 100 cycles at 1 C.At the voltage range of 2.8—4.3 V,the discharge specific capacity of Mg1.0@Al cathode remains 188.58 mAh/g after 100 cycles and 147.47 mAh/g after 400 cycles,with capacity retention rates of 95.18%and 74.54%,respectively.When changed at 5 C,the discharge specific capacity increased to 146.3 mAh/g.