Tungsten doping for stabilization of Li[Ni0.90Co0.05Mn0.05]O2 cathode for Li-ion battery at high voltage

Abstract

0.5-mol% and 1.0-mol% W-doped Li[Ni0.90Co0.05Mn0.05]O2 cathodes are synthesized by introducing W in the [Ni0.90Co0.05Mn0.05](OH)2 precursor stage. The W doping considerably improves the cycling stability at 2.7–4.3 V (96% at 100 cycles) and even at 4.4 V (94.5% at 100 cycles) with minimal reductions in the initial capacity (235 mA h g−1 at 4.4 V) of the 1.0-mol% W-doped. The superior chemical stability of the 1.0-mol% W-doped Li[Ni0.90Co0.05Mn0.05]O2 cathode is confirmed by an accelerated thermal aging test (storing of the highly delithiated cathode in the electrolyte at 60 °C). The observed improvement in the performance of the W-doped Li[Ni0.90Co0.05Mn0.05]O2 cathode is attributed mainly to bulk structure stabilization through the reduction in the internal strain, suppressing the detrimental formation of microcracks. Moreover, the spinel-like phase on the periphery of the primary particles acts as a buffer to protect the particle interior from the electrolyte attack. The applicability of the 1.0-mol% W-doped Li[Ni0.90Co0.05Mn0.05]O2 cathode for a high-energy-density Li-ion battery for electric vehicles is partially verified as it maintains 89% of its initial capacity after 500 cycles in a full-cell cycled at a high voltage of 4.3 V (vs. graphite), compared to the value of only 60% for the pristine cathode.