Stabilization of High-Energy Cathode Materials of Metal-Ion Batteries: Control Strategies and Synthesis Protocols

Abstract

Metal-ion batteries, especially lithium-ion batteries (LIBs), sodium-ion batteries (SIBs), and potassium-ion batteries (PIBs), have emerged as promising electronic devices for energy conversion and storage. To satisfy the upsurging demand for high energy density, cathode materials as the determining component in the battery system are driven to deliver higher capacities by either extracting more active metal ions (Li+, Na+, and K+) or increasing the operating voltage. However, serious side reactions of cathodes will occur, leading to severe capacity fading and safety risk. Surface coating has been confirmed as an effective strategy to stabilize cathodes and has been widely applied in the fabrication of high-energy cathodes for different metal-ion battery systems. In this review, we will summarize the recent progress in surface coating of high-energy cathodes for LIBs, SIBs, and PIBs. We will mainly discuss the available synthetic strategy for precise surface coating as a result of its importance in achieving an optimized balance between surface protection and charge transfer. Thereby, the structure–performance relationship will be built to highlight the contribution from surface control. Finally, challenges and opportunities in the future development of surface coating for high-energy cathodes of rechargeable batteries are also discussed.

Transition metal oxides as a cathode for indispensable Na-ion batteries

“…Since it consumes a lot of Na, the electronic conductivity decreased, and the electrochemical property was compromised. 195 Many researchers suggested applying coating modifications to the surface of cathode materials, such as carbon coating, 196 polymer coating, 197 and inorganic compound coating 198 to solve these issues. The cathode material can avoid reacting with the air and electrolyte by having a coating layer on its surface that can stop Na from escaping.…”

Recent Advances in Surface Coatings of Layered Cathode Materials for High‐Performance Sodium‐Ion Batteries

“…In contrast, the wet chemical method is considered to be an ideal surface coating method due to its simple synthesis method, low cost and environmental friendliness, However, it should be noted that the cathode material is usually sensitive to moisture, so organic solvents such as ethanol should be selected instead of deionized water. [82] Liu et al [83] used a wet chemical method to coat the surface of a P2À Na 2/3 [Ni 1/3 Mn 2/3 ]O 2 electrode with Al 2 O 3 and investigated the reasons for the capacity decay of the electrode. It was found that the harmful reaction between the electrode and the electrolyte under high voltage led to the peeling of the metal oxide layer and thus resulted in poor cycling stability.…”

“…Wet chemical method : Despite the outstanding performances of surface coatings using ALD technology, the precursors used as coating materials are usually costly and poisonous, which not only increases the manufacturing costs of coated electrodes but also pollutes the environment. In contrast, the wet chemical method is considered to be an ideal surface coating method due to its simple synthesis method, low cost and environmental friendliness, However, it should be noted that the cathode material is usually sensitive to moisture, so organic solvents such as ethanol should be selected instead of deionized water [82] …”

Mainstream Optimization Strategies for Cathode Materials of Sodium‐Ion Batteries

“…It consumes considerable Na + , so the electronic conductivity declined and the electrochemical property was impaired. [ 47 ] To address these problems, many researchers proposed to carry out coating modifications on the surface of cathode materials, such as carbon coating, [ 48 ] inorganic compounds coating, [ 49 ] and polymer coating. [ 50 ] The coating layer on the surface of the cathode material can prevent Na + from escaping and the cathode material from reacting with the air and electrolyte.…”