Study on Enhancement of Corrosion Resistance of Lithium Ion Battery by Using Graphene Film

【introduction】

Current collectors are an important part of rechargeable lithium-ion batteries (LIBs) and are a bridge between internal and external circuits. Despite the ever-changing positive and negative electrode materials, Al foil and Cu foil are the most popular positive and negative current collectors in LIBs due to their high conductivity, proper electrochemical stability and low cost. However, Al foil is susceptible to local electrochemical anodic corrosion during long-term cycling, resulting in increased resistance, short circuit, and parasitic side reactions. To solve this problem, the researchers used graphene films as conductive coatings and interface barriers to improve the electrochemical corrosion resistance of aluminum foils. Multi-layer graphene film is directly grown on aluminum foil for commercial current collector by plasma chemical vapor deposition, and multi-layer graphene film closely adhered to aluminum foil has ion/molecular impermeability, which can effectively prevent anode pole The Al3+ produced by the reaction is complexed with an anion, a solvent molecule or the like in the electrolyte. Therefore, the graphene-coated aluminum foil can significantly improve its electrochemical corrosion resistance.

[Introduction]

Recently, Professor Peng Hailin and Academician Liu Zhongfan (co-communication author) of the School of Chemistry and Molecular Engineering of Peking University have enhanced the corrosion resistance of LiPF6 and LiTFSI electrolytes by coating aluminum foil with low-temperature graphene film. In addition, the LiMn2O4 Battery exhibits superior electrochemical performance using a graphene-coated aluminum foil as a current collector (LMO/GA) compared to the initial aluminum foil (LMO/PA). The long-term discharge capacity retention rate of LMO/GA can still reach the initial 91% after 950h, which is significantly higher than 75% of LMO/PA battery, and the self-discharge rate is lower. The research results were published on Adv. Mater. under the title "Graphene-Armored Aluminum Foil with Enhanced Anticorrosion Performance as Current Collectors for Lithium-Ion Battery".

[Graphic introduction]

Figure 1. Schematic diagram of electrochemical corrosion resistance of graphene coated aluminum foil current collector

Figure 2. Synthesis and characterization of graphene-coated aluminum foil by PECVD

(a) a physical photograph of the synthesized GA;

(b) the Raman spectrum of GA;

(c) XPS of C1s in GA;

(d) a cross-sectional transmission electron micrograph of the GA;

(e) the elemental distribution map of GA;

(f) Low-power transmission electron micrograph of the multilayer graphene produced; high-power transmission electron micrograph of the multilayer graphene, with a scale of 5 nm.

Figure 3. GA improves electrochemical corrosion resistance

(a) CV curve of GA in LPF6 electrolyte;

(b) CV curve of PA in LPF6 electrolyte;

(c) Scanning electron micrograph of GA after CV test;

(d) Scanning electron micrograph of GA after PA test, the scale of the illustration is 2 μm.

Figure 4. GA current collector improves battery electrochemical performance

(a) Long-term low-rate cycling performance of LMO/PA and LMO/GA batteries, solid and circle are Ccha and Cdis, respectively;

(b) Self-discharge curves for LMO/PA and LMO/GA batteries;

(c) Magnification/power performance of LMO/PA and LMO/GA batteries;

(d) Charge and discharge curves for LMO/PA and LMO/GA batteries, with solid lines and circles being LMO/PA and LMO/GA batteries, respectively;

(e) Electrochemical impedance analysis of LMO/PA and LMO/GA batteries.

【summary】

Researchers have made full use of graphene films that are impermeable to ion molecules, and directly grow multi-layer graphene films on the surface of aluminum foil under low temperature conditions, which can improve the corrosion resistance of current collectors in LiPF6 and imide-based electrolytes. At the same time, researchers have shown that LiMn2O4 cells with graphene coated aluminum foil as a current collector have superior electrochemical performance, including better long-term cycle and rate performance, and improved self-discharge performance. This also laid the foundation for the design of future 5V high-voltage lithium-ion batteries .