Investigation of W-doped in high-nickel LiNiCoMnO cathode materials for high-performance lithium-ion batteries.

WO as tungsten dopant is introduced into lithium nickel cobalt manganese (LiNiCoMnO, NCM) layered oxide powders to synthesize W-doped NCM cathode materials during the lithiation process of the hydroxide precursor. Introducing W into the lattice can lead to the diversities of the crystal structure, surface morphology, and electrochemical performance. The crystal structure confirmed by X-ray diffraction indicates that the W-doped oxide powders present a typical R-3m layered structure with larger interplanar distance and cell volume. Also, scanning electron microscope images reveal that the primary particles shrink forming a tighter surface under the effect of W, while the specific changes gradually aggravate with increase in the content of W added. The excellent electrochemical stability of W-doped samples is observed, as the stable host structure is reinforced by the strong W-O bond. The stable structure does not only inhibit the anisotropic volume change caused by repetitive H2 ⇔ H3 phase transitions, but also sustains the integrated structure to impede the formation of microcracks and the appearance of more side reactions. This research provides an effective route on investigating the potential association between electrochemical performance and structure change for W-doped strategy.