ZrO2/Zr4+ surface coating/doping of LiNi0.5Mn1.5O4-δ for lithium ion battery positive electrodes

Abstract

High energy and power density lithium ion batteries are extensively being studied for their potential applications in portable electronics and hybrid/full electric vehicles as well as for their ability to store solar, wind and other renewable energies with high efficiency [1]. LiNi 0.5 Mn 1.5 O 4-δ (LNMO) is a high voltage lithium ion battery cathode material with potential for high power applications requiring good rate capability, such as hybrid/full electric vehicles [2]. The cyclic stability of LNMO remains an issue since all cathode materials containing Mn are challenged with a capacity fade problem due to Mn leaching into commercial electrolytes, during cycling or storage [1, 3]. One of the mechanisms causing Mn leaching is by hydrofluoric acid corrosion. HF forms by hydrolysis of LiPF 6 salt in electrolyte in presence of traces of water [3]. One way to prevent the Mn loss is to modify the surface of the cathode particles by coating or doping the surface with a chemically stable material. Zr 4+ /ZrO 2 is a good canditate to be used as a surface modification material since Zr-O has a high bond-dissociation energy (766.1±10.6 kJ/mol [4]). Zr-O presence at the surface can make the particle more stable against leaching compared to Mn-O (362±25 kJ/mol) or Ni-O (366±30 kJ/mol) presence at the surface. Purpose of this study is therefore to coat or dope the LNMO particle surfaces with ZrO 2 shell or Zr 4+ cation, respectively, to obtain batteries having better cycle life and rate performance than the LNMO without any surface modification.