Cobalt-free LiNiO2 cathode materials offer a higher energy density at a lower cost than high Co-containing cathode materials. However, Ni­(OH)2 precursors for LiNiO2 cathodes are traditionally prepared by the coprecipitation method, which is expensive, complex, and time-consuming. Herein, we report a fast, facile, and inexpensive electrolysis process to prepare a Ni­(OH)2 precursor, which was mixed with LiOH/LiNO3 salts to obtain a LiNiO2 cathode material. A combination of advanced characterization techniques revealed that the LiNiO2 cathode material prepared in this way exhibited an excellent layered structure with negligible Li/Ni site mixing and surface structural distortion. Electrochemical cycling of the LiNiO2 cathode material showed an initial discharge capacity of 235.2 mA h/g and a capacity retention of 80.2% after 100 cycles (at 1 C) between 2.75 and 4.3 V. The degradation of the cycling performance of the LiNiO2 cathode material was mainly attributed to the formation of a surface solid–electrolyte interface and a ∼5 nm rock salt-like structure, while the bulk structure of the cathode after cycling was generally stable.

The particle morphology of LiNiO 2 (LNO), the final product of Co-free high-Ni layered oxide cathode materials, must be engineered to prevent the degradation of electrochemical performance caused by the H2−H3 phase transition. Introducing a small amount of dopant oxides (Nb 2 O 5 as an example) during the electrolysis synthesis of the Ni(OH) 2 precursor facilitates the engineering of the primary particles of LNO, which is quick, simple, and inexpensive. In addition to the low concentration of Nb that entered the lattice structure, a combination of advanced characterizations indicates that the obtained LNO cathode material contains a high concentration of Nb in the primary particle boundaries in the form of lithium niobium oxide. This electrolysis method facilitated LNO (EMF-LNO) engineering successfully, reducing primary particle size and increasing particle packing density. Therefore, the EMF-LNO cathode material with engineered morphology exhibited increased mechanical strength and electrical contact, blocked electrolyte penetration during cycling, and reduced the H2−H3 phase transition effects.