High Rate Capability and Cycling Stability in Multi-Domain Nanocomposite LiNi1–xTi3x/4O2 Positive Electrodes

Abstract

LiNiO2 positive electrode materials for lithium-ion batteries have experienced a revival of interest due to increasing technological energy demands. Herein a specific Ti4+ substitution is targeted into LiNiO2 to access new compositions by synthesizing the LiNi1–xTi3x/4O2 solid solution with the aim of retaining Ni3+. Compositions in the range 0.025 ≤ x ≤ 0.2 form nanocomposites of compositionally homogeneous ordered R (Formula presented.) m and disordered Fm (Formula presented.) m rock salt domains as observed via X-ray and neutron diffraction, and STEM. The disordered rock salt domains stabilize the ordered structure to provide excellent structural reversibility via the formation of coherent interfaces during cycling and enable deep delithiation using a constant voltage charging step without structural degradation. The detrimental structural phase transitions associated with the poor cyclability of LiNiO2 are suppressed to yield a low strain positive electrode material with high capacity retention that offers high-rate capability even under increased cell electrode mass loadings. The composition x = 0.075 (LiNi0.925Ti0.05625O2) affords a 93% capacity retention after 100 cycles (100 mA g−1) and demonstrates high reversible capacities of 125 mAh g−1 even under rates of 3200 mA g−1. LiNi0.925Ti0.05625O2 exhibits exceptional performance at electrode mass loadings (13.6 mg cm−2) comparable to those required for commercial cell applications.