Ultrahigh Ni-Rich (90%) Layered Oxide-Based Cathode Active Materials: The Advantages of Tungsten (W) Incorporation in the Precursor Cathode Active Material

Abstract

Minor amounts of tungsten (W) are well known to improve Ni-rich layered oxide-based cathode active materials (CAMs) for Li ion batteries. Herein, W impacts are validated and compared for varied concentrations and incorporation routes in aqueous media for LiNi_0.90Co_0.06Mn_0.04O₂ (NCM90-6-4), either via modification of a precursor Ni_xCo_yMn_z(OH)₂ (pCAM) within a sol–gel reaction or directly during synthesis, i.e., either via an W-based educt or during co-precipitation in a continuously operated Couette–Taylor reactor. In particular, the sol–gel modification is shown to be beneficial and reveals >500 cycles for ≈80% state-of-health NCM90-6-4||graphite cells. It can be related to homogeneously W-modified surface as well as smaller and elongated primary particles, whereas the latter are suggested to better compensate anisotropic lattice stress and decrease amount of microcracks, consequently minimizing further rise in surface area and the accompanied failure cascades (e.g., phase changes, metal dissolution, and crosstalk). Moreover, the different incorporation routes are shown to reveal different outcomes and demonstrate the complexity and sensitivity of W incorporation.