A Molten‐Salt Method to Synthesize Ultrahigh‐Nickel Single‐Crystalline LiNi_0.92Co_0.06Mn_0.02O₂ with Superior Electrochemical Performance as Cathode Material for Lithium‐Ion Batteries

Abstract

Ni‐rich layered oxides have been intensively considered as promising cathode materials for next‐generation Li‐ion batteries. Nevertheless, the performance degradation caused by intergranular cracks and electrode/electrolyte interface parasitic reactions restricts their further application. Compared with secondary particles, single‐crystal (SC) materials have better mechanical integrity and cycling stability. However, the preparation of ultrahigh‐nickel layered SC cathode still remains a serious challenge. Herein, a novel LiOH‐LiNO3‐H3BO3 molten‐salt method is proposed to synthesize SC LiNi0.92Co0.06Mn0.02O2 with considerable crystallinity and uniformity. The critical impacts of calcination temperature and boric acid on the microstructure and electrochemical property of Ni‐rich layered oxides are systematically investigated. The results show that the crystal growth is promoted and the stability of crystal structure is improved by this synthesis method. In particular, the optimal electrode demonstrates a superior initial discharge capacity of 214.8 mAh g–1 with a high capacity retention of 86.3% over 300 cycles as tested by pouch‐type full cells at 45 ºC. This work not only prepares an ultrahigh‐nickel layered CS cathode with superior electrochemical performances, but also provides a feasible method for the synthesis of other CS layered cathode materials.

Dual-functional boron-modification on a cobalt-free single-crystal layered cathode for high-voltage lithium-ion batteries

“…46 The unstable lattice O further aggravates the Li/Ni mixing and the contraction of the transition metal slab and Li slab, endangering the layered structure. 47,48 Due to the strong interaction between boron and oxygen (bond enthalpy: 809 kJ mol −1 ), 49 boron in 2#B-LNM can effectively anchor the lattice O, thereby maintaining the coordination number of Ni–O bonds.…”

Cobalt/aluminum co-substitution in a LiNi0.9Mn0.1O2layered cathode for improving kinetics

“…Interestingly, by matching the GITT calculation results and cyclic voltammetry (CV) curves, it is found that each phase transition corresponds to a decrease in D Li + , especially in the H2 ↔ H3 phase transition position around 4.2 V. This sharp decline means that the H2 ↔ H3 phase transition is a highly kinetically controlled process, corresponding to the concurrent Li + diffusion and structural rearrangement. 23 Obviously, the CA-NM shows a smoother transition at around 4.2 V compared with the NM, meaning stable kinetic performance. Based on the previous research, 5 it is not only related to the lower Li + /Ni 2+ disorder degree in the initial state, but is also attributed to the fact that Al 3+ preferentially transfers from octahedral interstice sites to the Li layer to hinder the Ni 2+ migration path in a deep charge state.…”

Single-Crystal Growth of P2-Type Layered Oxides with Increased Exposure of {010} Planes for High-Performance Sodium-Ion Batteries

“…High-temperature and prolonged heating can promote the growth of single-crystal particles to a certain extent, but they cannot easily regulate the orientation of crystal planes and lead to an increase in the degree of particle agglomeration, sodium volatilization, and energy consumption. , The molten salt method is a better choice than the abovementioned method for regulating the size and orientation of single-crystal particles. Although numerous studies have reported the preparation of single-crystal layered oxide cathode materials for LIBs using the molten salt method, − only a few studies have been conducted with regard to such materials for SIBs. NaOH and Na 2 SO 4 have been proven to be applicable as molten salts for promoting the growth of Na-based layered oxide single-crystal particles. , Notably, these two molten salts can also encourage the preferential growth of {001} planes (containing planes such as the (002) and (004) planes) while promoting an increase in the size of the single-crystal particles.…”