Negative Electrode Coating Structure for Stronger Li-Ion Adhesion
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Solution Overview
Problem
Lithium-ion batteries face issues with the adhesion of negative electrode active material layers to current collectors, leading to peeling and reduced battery performance, and the insufficient strength of copper foils causes breakage during cycling, affecting energy density and safety.
Innovation Solution
A first coating with inorganic particles of Mohs hardness 2 to 7 is applied between the current collector and the negative electrode active material layer, forming an adhesion unit with enhanced strength and cohesion, which increases the adhesion between the current collector and the active material layer, reducing the binder content and enhancing energy density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a conductive coating including a conductive agent and a binder is provided on the current collector, then adhesion between the current collector and active material layer is improved, but the adhesion strength still cannot meet current needs and the active material layer peels off
Solution Approach 1:
The patent applies a multi-layer composite coating structure consisting of a first coating layer (containing inorganic particles and binder) and a second coating layer (conductive coating with conductive agent and binder). This composite structure combines the adhesion enhancement from the first layer with the electrical conductivity from the second layer, achieving both strong adhesion and sufficient conductivity that neither single layer could provide alone.
2Strength
If the strength of the negative electrode current collector is increased to prevent breakage during cold pressing, then processing reliability is improved, but the copper foil may still cause swelling during cycling that squeezes the positive electrode plate
Solution Approach 1:
The patent applies different functional coatings to different aspects of the current collector system. The first coating layer with inorganic particles provides localized reinforcement and dimensional stability to prevent swelling during cycling, while the second conductive coating layer ensures electrical conductivity. This local differentiation allows the current collector to maintain strength without excessive swelling that would harm the positive electrode plate.
3Strength
If the adhesion between current collector and active material layer is increased, then peeling resistance is improved, but the binder content in the active material layer must be reduced to increase energy density
Solution Approach 1:
The first coating layer acts as an intermediary between the current collector and the second conductive coating layer/active material layer. The inorganic particles and binder in this intermediate layer provide strong adhesion and mechanical reinforcement, allowing the second layer to use less binder while maintaining overall adhesion strength. This intermediary structure decouples the adhesion function from the binder content in the active material layer.
Data Source
AI summary
An electrochemical apparatus includes a negative electrode. The negative electrode includes a current collector, a first coating, and a second coating, the second coating is provided on at least one surface of the current collector, and the first coating is provided between the current collector and the second coating and contains inorganic particles with a Mohs hardness of 2 to 7.