Composite Negative Electrode Plate for Low-Impedance Battery Cycling
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Solution Overview
Problem
Existing negative electrode plates in secondary batteries face challenges in achieving high energy density and long cycle performance due to the weight and mechanical limitations of metal current collectors, which can lead to cracking and increased impedance.
Innovation Solution
A negative electrode plate design featuring a metal conductive layer and an organic support layer with a specific active material distribution, where the active material's particle sizes in different directions satisfy certain ratios, reducing weight and preventing damage to the conductive layer, thereby maintaining electrical conductivity and improving charge/discharge performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a metal current collector with relatively large thickness is used to meet electrical conductivity and current collecting performance requirements, then the electrical conductivity and mechanical strength are improved, but the weight increases which is not beneficial for increasing energy density
Solution Approach 1:
The patent uses a composite current collector structure consisting of an organic support layer and a metal conductive layer. The organic support layer provides mechanical strength and structural integrity, while the metal conductive layer (with thickness of 1-10 μm, significantly thinner than conventional metal current collectors) provides electrical conductivity. This composite approach allows the metal layer to be much thinner than traditional solid metal current collectors while maintaining both mechanical and electrical performance requirements.
Solution Approach 2:
The current collector is divided into two functional layers: the organic support layer that handles mechanical support and the metal conductive layer that handles electrical conduction. This segmentation allows each layer to be optimized independently for its specific function, enabling the metal layer to be thin enough to reduce weight while the organic layer provides the necessary mechanical strength.
2Weight of moving object
If a thin metal conductive layer is disposed on an organic support layer to reduce weight and increase energy density, then the weight is reduced, but the cycle performance deteriorates due to mechanical damage and cracking
Solution Approach 1:
The composite structure of organic support layer plus metal conductive layer provides both weight reduction and mechanical protection. The organic support layer acts as a robust substrate that prevents the thin metal conductive layer from cracking or deforming during battery cycling, thereby maintaining electrical conductivity and cycle performance despite the reduced metal layer thickness.
Solution Approach 2:
The organic support layer serves as a protective cushioning layer that prevents mechanical damage to the thin metal conductive layer before cracking can occur. This protective structure is built in advance to withstand the mechanical stresses of battery assembly and cycling, preventing premature failure of the conductive layer.
3Ease of manufacture
If the active material particle size is not controlled properly, then the manufacturing is easier, but the active material causes damage such as cracks to the metal conductive layer leading to increased impedance
Solution Approach 1:
The patent specifies controlled particle size parameters for the active material (a/b ratio between 0.8-20 and c/d ratio between 0.8-20, where a and c are dimensions parallel to the metal conductive layer and b and d are dimensions in the thickness direction). This parameter control ensures that active material particles do not exert excessive localized stress on the thin metal conductive layer during insertion/extraction cycles, preventing crack formation and maintaining electrical conductivity.
Data Source
AI summary
The present application discloses a negative electrode plate including a negative electrode active material layer including a first active material layer; wherein in a first cross section in a thickness direction of the negative electrode plate, the first active material has a size a in a direction parallel to the metal conductive layer, the first active material has a size b in the thickness direction, satisfying 0.8≤a/b≤20; in a second cross section in the thickness direction of the negative electrode plate, the first active material has a size c in the direction parallel to the metal conductive layer, the first active material has a size d in the thickness direction, satisfying 0.8≤c/d≤20; and the first cross section is parallel to a first direction, the second cross section is parallel to a second direction, and the first direction intersects the second direction.