Layered Positive Electrode Plate for Capacity and Thermal Runaway
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Solution Overview
Problem
Existing lithium-ion secondary batteries face challenges in achieving high capacity while minimizing the probability of thermal runaway, particularly during nail penetration and thermal stress tests.
Innovation Solution
A positive electrode plate design with a conductive coating, a first active material layer, and a second active material layer, where the first active material is fire-resistant and the second active material has high energy density, arranged in specific layers to optimize Li+ transport and reduce impedance, and a conductive coating enhances lithium intercalation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a single active material layer with high energy density is used, then battery capacity is improved, but the probability of thermal runaway increases
Solution Approach 1:
The positive electrode plate is divided into two distinct active material layers: a first active material layer containing fire-resistant material (such as lithium iron phosphate) and a second active material layer containing high energy density material (such as layered ternary material). This segmentation allows each layer to fulfill its specific function - the first layer provides thermal safety while the second layer delivers high capacity, thereby resolving the contradiction between safety and capacity
Solution Approach 2:
The patent employs a composite structure combining two different active materials with complementary properties. The fire-resistant material in the first layer acts as a thermal barrier, while the high energy density material in the second layer provides superior capacity. Together, they form a composite electrode system that achieves both safety and high performance
2Reliability
If a fire-resistant active material is used, then thermal safety is improved, but energy density decreases
Solution Approach 1:
The electrode is segmented into two functional layers where the first layer uses fire-resistant material optimized for thermal safety and the second layer uses high energy density material optimized for capacity. This functional segmentation allows each material to be selected and optimized for its primary purpose without compromising the other
Solution Approach 2:
Different regions of the positive electrode are assigned different material properties: the first active material layer (closer to the separator) has fire-resistant properties for thermal safety, while the second active material layer (outer layer) has high energy density properties for capacity. This local differentiation of material quality resolves the contradiction by allowing each region to excel at its specific function
3Speed
If the Li+ transport path is shortened, then power performance is improved, but the electrode structure becomes more complex
Solution Approach 1:
The positive electrode is segmented into two layers with the fire-resistant material layer positioned adjacent to the separator and the high energy density material layer on the outer side. This segmentation creates direct Li+ transport pathways from the second layer through the first layer to the separator, shortening the diffusion distance and improving power performance
Solution Approach 2:
The patent introduces a new dimensional arrangement by stacking two active material layers in the thickness direction of the electrode. This layered configuration in the z-dimension (through-thickness direction) enables shorter Li+ transport paths compared to traditional single-layer designs, improving power performance while maintaining a manageable structural complexity
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
The design reduces the probability of thermal runaway and improves battery capacity by utilizing the unique properties of each material layer, while also facilitating miniaturization and enhancing lithium ion transport.
Implementation Method 1
enhance lithium intercalation and deintercalation activity of the positive electrode
Implementation Method 2
block a direct contact between the upper layer or the positive electrode and the current collector
Data Source
AI summary
A positive electrode plate includes a current collector, a conductive coating, a first active material layer and a second active material layer, where the conductive coating is formed on a surface of the current collector, the first active material layer is formed on a surface of the conductive coating, and the second active material layer is formed on a surface of the first active material layer; the first active material layer includes a first active material; the second active material layer includes a second active material; the first active material does not catch fire in a nail penetration test; and the second active material has a gram capacity greater than or equal to 165 mAh/g.