Graphene-Metallized Current Collector for Crack-Resistant Li-Ion Electrodes
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Solution Overview
Problem
Existing composite current collectors in lithium-ion secondary batteries suffer from conductive layer detachment due to inconsistent elongation rates of layers, leading to microcracks and moisture-induced degradation, which affects cycle life.
Innovation Solution
A composite positive electrode current collector with a graphene metallization layer composed of highly reduced graphene oxide between the protective and conductive layers, enhancing interlayer bonding and mechanical strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a composite current collector is cold-pressed to make the electrode plate, then the electrode plate is under pressure and layers extend, but inconsistent elongation rates of layers result in microcracks in the conductive layer and protective layer
Solution Approach 1:
The patent introduces a buffer layer between the protective layer and conductive layer. This buffer layer acts as an intermediary that absorbs differential stress during cold-pressing, preventing direct stress transmission that would cause microcracks. The buffer layer's intermediate position allows it to accommodate elongation differences between the protective and conductive layers without compromising the integrity of either layer.
Solution Approach 2:
The patent employs a multi-layer composite structure consisting of the protective layer, buffer layer, and conductive layer. This composite design allows each layer to be optimized for its specific function while working together to resolve the contradiction. The buffer layer in the composite structure provides mechanical compliance that prevents crack formation during pressing operations.
2Reliability
If microcracks exist in the protective layer, then contact area between electrolytic solution and protective layer increases, but this leads to destruction of the protective layer by corrosive substances
Solution Approach 1:
The buffer layer serves as a preemptive protective barrier that prevents microcrack formation in the protective layer before corrosive substances can exploit these defects. By cushioning the mechanical stress during electrode plate fabrication, the buffer layer ensures the protective layer remains intact, thereby preventing subsequent chemical degradation from moisture and corrosive substances in the electrolytic solution.
Solution Approach 2:
The buffer layer acts as an intermediary barrier between the conductive layer and the protective layer, absorbing mechanical stress that would otherwise transmit to the protective layer and create microcracks. This intermediate protection prevents direct exposure of the protective layer to damaging stresses, maintaining its integrity against corrosive substances.
3Manufacturing precision
If humidity in manufacturing environment exceeds standard, then oxide of protective layer absorbs moisture, but this affects deposition of conductive layer and bonding force between layers
Solution Approach 1:
The buffer layer serves as an intermediary that isolates the conductive layer deposition process from moisture absorbed by the protective layer's oxide. This intermediate barrier prevents moisture interference during conductive layer deposition, ensuring proper adhesion and bonding between layers even when manufacturing environment humidity exceeds standards.
Solution Approach 2:
The buffer layer self-regulates moisture content between layers during manufacturing. By absorbing or blocking moisture migration from the protective layer to the conductive layer interface, the buffer layer automatically compensates for high environmental humidity without requiring additional manufacturing controls, ensuring consistent bonding quality.
Data Source
AI summary
A composite positive electrode current collector may include a protective layer, a graphene metallization layer and a conductive layer arranged in sequence on a surface of an insulation layer. The protective layer may include a metal oxide, and the graphene metallization layer may contain highly reduced graphene oxide having an oxygen-containing organic group.