Nanostructural effects on the cycle life and Li+ diffusion coefficient of nickel oxide anodes

•We investigate nickel oxide anode nanostructural effects on performance.•Current pulse relaxation technique was used to calculate diffusion coefficients.•Diffusivity was deconvoluted through two phases during charging.•Li2O + Ni phase diffusion was strongly dependent on electrode geometry.•Controlled, nanosized NiO crystallites preferred for optimal performance.

The nanostructure of nickel oxide was controlled using two different synthesis methods and its influence on cyclability, charge/discharge capacity and mass transport of Li+ ions at the Li-ion battery anode was examined. Effective diffusion coefficients were calculated using the current pulse relaxation technique and a new model was derived and applied to deconvolute the mass transport of Li+ through the NiO and Li2O + Ni phases. The NiO phase diffusion coefficients were found to be independent of the material geometry; however, the diffusion coefficient of Li+ in the Li2O + Ni phase was strongly dependent on the electrode geometry. Results suggest that controlled nanosized crystallites of NiO are preferred as they result in smaller average grain boundary sizes for the Li2O + Ni phase formed during cell charging. This has several benefits including better accessibility of the Li2O + Ni phase during discharge, yielding improved cycle life, a decreased Li+ path length leading to lower tortuosity and a larger grain boundary area allowing more in-plane Li+ transport.