Electrolyzed Ni(OH)₂ Precursor Sintered with LiOH/LiNiO₃ Mixed Salt for Structurally and Electrochemically Stable Cobalt-Free LiNiO₂ Cathode Materials

Abstract

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.

Electrolysis Process-Facilitated Engineering of Primary Particles of Cobalt-Free LiNiO2 for Improved Electrochemical Performance

“…The obtained cathode material is denoted as EMF-LNO. Details of the experimental and synthetic procedures are available in our previous report . Additionally, bare E-LNO was synthesized for comparison using the same method.…”

“…Moreover, the degradation of surface structure is the primary cause of the decrease in the capacity of LNO cathode materials. 19,20 Numerous strategies to synthesize LNO with excellent electrochemical performance have been proposed. Our group has previously synthesized LNO with low Li/Ni cation mixing and explained its principal decay mechanism.…”

“…The details of the electrolysis process have been reported previously. 19 This process has several advantages over the conventional coprecipitation method for modifying cathode materials, including its simplicity, speed (5 h), and the ability to be processed in a lab-sized (500 mL) beaker. Using Nb 2 O 5 oxide as an exemplar, we modified the primary particles of LNO using the electrolysis process and then investigated the atomic-microscopic structures of LNO before and after modification.…”

“…We demonstrate a novel method for engineering primary particles of LNO cathode material by introducing dopant oxides during the electrolysis-based preparation of the Ni­(OH) 2 precursor. The details of the electrolysis process have been reported previously . This process has several advantages over the conventional coprecipitation method for modifying cathode materials, including its simplicity, speed (5 h), and the ability to be processed in a lab-sized (500 mL) beaker.…”

Magnetic Li–M (M = Ni, Ni0.8Cu0.2, Cr) layered oxides nanoparticles for Li-ion batteries electrodes

“…Stoichiometric LiNiO 2 nanoparticles have been successfully obtained with the 'Pechini method' , which consists of a sol-gel synthesis in citric acid, followed by calcination [26,27]. In a recent work, the Ni hydroxide Ni(OH) 2 precursor was prepared also by an electrolysis process, and further used to synthesize a LiNiO 2 CAM [28].…”