A general route of fluoride coating on the cyclability regularity of high-voltage NCM cathodes

Enhancing humidity resistance of nickel-rich layered cathode materials by low water-soluble CaF2 coating

A low water-solubility but hydrophilic coating of CaF2 is demonstrated to be effective in mitigating the susceptibility of nickel-rich cathodes to moisture and even water. The ability of the cathode to resist water erosion is not inherently linked to either hydrophobicity or hydrophilicity, but lies in robust chemical bonding within the protective layer exhibiting low water solubility.

Structural tuning of copper sulfide material for sodium-ion batteries

In this work, single-crystal and twin-crystal copper sulfide materials are constructed in a regulatable and controlled manner. Twin boundaries are engineered into the copper sulphide material to significantly improve its electrochemical performance. The results demonstrate that structure tuning with twin crystals is an effective strategy for enhancing electrochemical reactions, and also sheds light on the design of electrode materials for sodium ion storage.

Effective and Low-Cost In Situ Surface Engineering Strategy to Enhance the Interface Stability of an Ultrahigh Ni-Rich NCMA Cathode

Ultrahigh Ni-rich quaternary layered oxides LiNi_1-x-y-zCo_xMn_yAl_zO₂ (1 - x - y - z ≥ 0.9) are regarded as some of the most promising cathode candidates for lithium-ion batteries (LIBs) because of their high energy density and low cost. However, poor rate capacity and cycling performance severely limit their further commercial applications. Herein, an in situ coating strategy is developed to construct a uniform LiAlO₂ layer. The NH₄HCO₃ solution is added to a NaAlO₂ solution to form a weak alkaline condition, which can reduce the hydrolysis rate of NaAlO₂, thus enabling uniform deposition of Al(OH)₃ on the surface of a Ni_0.9Co_0.07Mn_0.01Al_0.02(OH)₂ (NCMA) precursor. The LiAlO₂-coated samples show enhanced cycling stability and rate capacity. The capacity retention of NCMA increases from 70.7% to 88.3% after 100 cycles at 1 C with an optimized LiAlO₂ coating amount of 3 wt %. Moreover, the 3 wt % LiAlO₂-coated sample also delivers a better rate capacity of 162 mAh g^-1 at 5 C, while that of an uncoated sample is only 144 mAh g^-1. Such a large improvement of the electrochemical performance should be attributed to the fact that a uniform LiAlO₂ coating relieves harmful interfacial parasitic reactions and stabilizes the interface structure. Therefore, this in situ coating approach is a viable idea for the design of higher-energy-density cathode materials.

Single-Crystalline Cathodes for Advanced Li-Ion Batteries: Progress and Challenges

Single-crystalline cathodes are the most promising candidates for high-energy-density lithium-ion batteries (LIBs). Compared to their polycrystalline counterparts, single-crystalline cathodes have advantages over liquid-electrolyte-based LIBs in terms of cycle life, structural stability, thermal stability, safety, and storage but also have a potential application in solid-state LIBs. In this review, the development history and recent progress of single-crystalline cathodes are reviewed, focusing on properties, synthesis, challenges, solutions, and characterization. Synthesis of single-crystalline cathodes usually involves preparing precursors and subsequent calcination, which are summarized in the details. In the following sections, the development issues of single-crystalline cathodes, including kinetic limitations, interfacial side reactions, safety issues, reversible planar gliding and micro-cracking, and particle size distribution and agglomeration, are systematically analyzed, followed by current solutions and characterization techniques. Finally, this review is concluded with proposed research thrusts for the future development of single-crystalline cathodes.

AlF3-Al2O3 ALD Thin-Film-Coated Li1.2Mn0.54Co0.13Ni0.13O2 Particles for Lithium-Ion Batteries: Long-Term Protection

Improving the performance of existing cathode materials of lithium-ion batteries (LIBs) through surface modification has been proven to be an effective way to improve the performance of LIBs. However, it is a challenge to use a traditional method to prepare an effective coating film, which meets the requirements of uniformity, continuity, electrochemical stability, and strong mechanical properties. In this study, an ultrathin AlF₃-Al₂O₃ film was coated on the surface of Li_1.2Mn_0.54Co_0.13Ni_0.13O₂ (LRNMC) particles by atomic layer deposition (ALD) in a fluidized bed reactor. A cathode electrolyte interphase layer mainly composed of inorganic components was formed on the surface of AlF₃-Al₂O₃-coated LRNMC during the charge/discharge cycling process, which led to the enhancement of capacity and cycling stability. In addition, the coating layer significantly increased the shelf life of the cathode particles. For LRNMC particles with one cycle of Al₂O₃ ALD and one cycle of AlF₃ ALD coatings, there was no obvious degradation of electrochemical performance after being stored for more than 1 year, indicating long-term protection of ALD films for LIB cathode particles.

Interfacial Strategies for Suppression of Mn Dissolution in Rechargeable Battery Cathode Materials

It is urgent to develop high-performance cathode materials for rechargeable batteries to address the globally growing concerns of energy shortage and environmental pollution. Among many candidate materials, Mn-based materials are promising and already used in some commercial batteries. Yet, their applicable future in reversible energy storage is severely plagued by the notorious Mn dissolution behaviors associated with structural instability during long-term cycling. As such, interfacial strategies aiming to protect Mn-based electrodes against Mn dissolution are being widely developed in recent years. A variety of interface-driven designs have been reported to function efficiently in suppressing Mn dissolution, necessitating a timely summary of recent advancements in the field. In this review, various interfaces, including the prebuilt interface and the electrochemically induced interface, to suppress Mn dissolution for Mn-based cathodes are discussed in terms of their fabrication details and functional outcomes. Perspectives for the future of interfacial strategies aiming at Mn dissolution suppression are also shared.

Deciphering the effects of hexagonal and monoclinic structure distribution on the properties of Li-rich layered oxides

Uniform distribution of Li₂MnO₃ and LiMO₂ components in a Co-free Li-rich layered oxide is achieved by treating precursors with NH₃·H₂O, which expands the lattice parameter and promotes the activation of Li₂MnO₃, resulting in excellent electrochemical performance. What's more, it also contributes to the storage stability of Li-rich layered oxides.