A facile cathode design with a LiNi0.6Co0.2Mn0.2O2 core and an AlF3-activated Li1.2Ni0.2Mn0.6O2 shell for Li-ion batteries

A review on nickel-rich nickel-cobalt-manganese ternary cathode materials LiNi0.6Co0.2Mn0.2O2 for lithium-ion batteries: performance enhancement by modification

The new energy era has put forward higher requirements for lithium-ion batteries, and the cathode material plays a major role in the determination of electrochemical performance. Due to the advantages of low cost, environmental friendliness, and reversible capacity, high-nickel ternary materials are considered to be one of ideal candidates for power batteries now and in the future. At present, the main design idea of ternary materials is to fully consider the structural stability and safety performance of batteries while maintaining high energy density. Ternary materials currently face problems such as low lithium-ion diffusion rate and irreversible collapse of the structure, although the battery performance can be improved utilizing coating, ion doping, etc., the actual demand requires a more effective modification method based on the intrinsic properties of the material. Based on the summary of the current research status of the ternary material LiNi0.6Co0.2Mn0.2O2 (NCM622), a comparative study of the modification paths of the material was conducted from the level of molecular action mechanism. Finally, the major problems of ternary cathode materials and the future development direction are pointed out to stimulate more innovative insights and facilitate their practical applications.

Review of the Scalable Core-Shell Synthesis Methods: The Improvements of Li-Ion Battery Electrochemistry and Cycling Stability

The demand for lithium-ion batteries has significantly increased due to the increasing adoption of electric vehicles (EVs). However, these batteries have a limited lifespan, which needs to be improved for the long-term use needs of EVs expected to be in service for 20 years or more. In addition, the capacity of lithium-ion batteries is often insufficient for long-range travel, posing challenges for EV drivers. One approach that has gained attention is using core-shell structured cathode and anode materials. That approach can provide several benefits, such as extending the battery lifespan and improving capacity performance. This paper reviews various challenges and solutions by the core-shell strategy adopted for both cathodes and anodes. The highlight is scalable synthesis techniques, including solid phase reactions like the mechanofusion process, ball-milling, and spray-drying process, which are essential for pilot plant production. Due to continuous operation with a high production rate, compatibility with inexpensive precursors, energy and cost savings, and an environmentally friendly approach that can be carried out at atmospheric pressure and ambient temperatures. Future developments in this field may focus on optimizing core-shell materials and synthesis techniques for improved Li-ion battery performance and stability.

Enhanced Electrochemical Performance and Safety of LiNi0.88Co0.1Al0.02O2 by a Negative Thermal Expansion Material of Orthorhombic Al2(WO4)3

LiNi0.88Co0.1Al0.02O2 (NCA) is attractive for high-energy batteries, but phase transition and side reactions leave large volume change and thermal runaway. In order to address the drawbacks, orthorhombic Al2(WO4)3, a cheap anisotropic negative thermal expansion material, was synthesized and adopted to modify NCA, and its effects on the electrochemical performance and safety of NCA were investigated using multifarious techniques. Al2(WO4)3 can greatly improve the rate performance, cyclability at different temperatures, thermal stability, and interface behavior and intensify charge transfer as well as decline the deformation and side reactions of NCA. The discharge capacity of the NCA modified with 5 wt % Al2(WO4)3 reaches 170.0 mA h/g at 5.0 C and 25 °C. After 100 cycles, the values of this electrode at 1.0 C and 25 °C and at 3.0 C and 60 °C are 164.2 and 148.7 mA h/g, respectively, much higher than those of the pure NCA under the same conditions. Moreover, Al2(WO4)3 declines the byproducts and cation mixing and decreases the released heat, strain, and charge-transfer resistance after cycles of NCA about 37.1, 33.0, and 32.8%, respectively. The improvement mechanism is discussed. It opens an effective avenue for the applications of energy materials by simultaneously adjusting heat, structure, interface, and deformation.

NiCo2S4 Bi-metal Sulfide Coating on LiNi0.6Co0.2Mn0.2O2 Cathode for High-Performance All-Solid-State Lithium Batteries

NiCo₂S₄ nanoparticles (NPs) were dry coated on LiNi_0.6Co_0.2Mn_0.2O₂ (NCM622) cathode using a resonant acoustic coating technique to produce all-solid-state lithium batteries. The NiCo₂S₄ coating improved the electrochemical properties of the NCM622 cathode. In addition, NiCo₂S₄ eliminated the space-charge layer and the cathode showed an excellent affinity with the interface with a sulfide-based solid electrolyte as an inert material. X-ray diffraction patterns of NCM622 coated with NiCo₂S₄ showed the same peak separations and lattice parameters as those of bare NCM622. Field-emission scanning electron microscopy and electron dispersive spectroscopy mapping analyses showed that 0.3 wt% NiCo₂S₄-coated NCM622 had an evenly modified surface with NiCo₂S₄ NPs. X-ray photoelectron spectroscopy (XPS) revealed that the surface of 0.3 wt% NiCo₂S₄-coated NCM622 had two different S 2p peaks, a Co-S peak, and Ni and Co peaks, compared to those of bare NCM622. Electrochemical studies with electrochemical impedance spectroscopy and galvanostatic charge-discharge cycle performances showed that NiCo₂S₄-coated NCM622 retained a higher specific capacity over multiple cycles than bare NCM622. Especially, 0.3 wt% NiCo₂S₄-coated NCM622 exhibited a capacity retention of 60.6% at a current density of 15 mA/g for 20 cycles, compared to only 37.3% for bare NCM622. Finally, interfacial XPS and transmission electron microscopy-electron energy loss spectroscopy analyses confirmed the stable state of 0.3 wt% NiCo₂S₄-coated NCM622 with minimal side reactions.

Nickel-Rich Layered Cathode Materials for Lithium-Ion Batteries

Nickel-rich layered transition metal oxides are considered as promising cathode candidates to construct next-generation lithium-ion batteries to satisfy the demands of electrical vehicles, because of the high energy density, low cost, and environment friendliness. However, some problems related to rate capability, structure stability, and safety still hamper their commercial application. In this Review, beginning with the relationships between the physicochemical properties and electrochemical performance, the underlying mechanisms of the capacity/voltage fade and the unstable structure of Ni-rich cathodes are deeply analyzed. Furthermore, the recent research progress of Ni-rich oxide cathode materials through element doping, surface modification, and structure tuning are summarized. Finally, this review concludes by discussing new insights to expand the field of Ni-rich oxides and promote practical applications.