Polymer-Coated Anode Structure for Binder-Stable Thick Electrodes
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Solution Overview
Problem
Conventional dry process-based electrode coating technologies face limitations in increasing electrode thickness and stability due to electrochemical decomposition reactions caused by binders like PTFE, which are unstable and react with lithium during charging and discharging processes in secondary batteries.
Innovation Solution
Incorporating a polymer coating layer between the core anode material and the binder, specifically using polymers like PVDF, PTrFE, PCFE, or PCTFE, to block electron transport paths and reduce electrochemical decomposition reactions, thereby enhancing the stability and efficiency of the anode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a binder like PTFE is used in dry process-based electrode coating, then electrode thickness can be increased, but electrochemical decomposition reactions occur at about 0.5 V (vs. Li/Li+) due to instability of the binder
Solution Approach 1:
A coating layer comprising a polymer (such as PVDF, PTrFE, PCFE, or PCTFE) is introduced as an intermediary between the core part (anode material) and the binder. This coating layer blocks electron transport paths from the core part to the binder, preventing electrochemical decomposition reactions of the binder while maintaining electrical conductivity of the electrode. The polymer coating acts as a protective mediator that isolates the unstable binder from direct electrochemical exposure.
Solution Approach 2:
The anode is structured as a composite material system consisting of three components: core part (anode material), coating layer (polymer), and binder. This composite structure combines the high capacity of materials like silicon or germanium with the stability provided by the polymer coating and binder system, achieving both thick electrode construction and electrochemical stability.
2Reliability
If binder decomposition is suppressed by using stable binders, then initial Coulombic efficiency improves, but the binder must be chemically stable which limits material choices
Solution Approach 1:
The polymer coating layer serves as a mediator that protects the binder from electrochemical decomposition. This allows the use of binders that would otherwise be too unstable for direct contact with the electrolyte, expanding the range of usable binder materials while maintaining high initial Coulombic efficiency through the protective coating.
3Ease of manufacture
If conventional wet process-based electrode coating is used, then electrode coating is straightforward, but electrode thickness increase is limited and solvent recovery is required
Solution Approach 1:
The patent replaces the wet process (liquid-based coating requiring solvent evaporation and recovery) with a dry process approach. The coating layer is applied in a dry state and then activated, eliminating the need for solvent recovery systems while enabling thicker electrode construction. This substitution of the coating mechanism removes the thickness limitation inherent in wet processing.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach increases the initial Coulombic efficiency of the secondary battery to greater than 83% and improves cycle characteristics by suppressing binder decomposition and reducing lithium ion resistance, leading to enhanced charge capacity and battery performance.
Implementation Method 1
blocking electron transport paths from core part to the binder by including a coating layer including a polymer between the core part and the binder
Implementation Method 2
The polymer may have electronic conductivity of equal to or less than about 10^-6 S/cm... The coating layer satisfies Relation 1 below: (Coating Layer Content)/(Binder Content) ≤ 0.1
Data Source
AI summary
Disclosed are an anode including a core part and a binder and a secondary battery including the same. Particularly, a coating layer including a polymer is provided between the core part and the binder and thus blocks electron transport paths from the core part to the binder. Thereby, decomposition of the binder is suppressed, and thus, the charge capacity and the initial Coulombic efficiency of the secondary battery are increased.