Secondary Battery Cathode Plate Primer Layer Design
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Solution Overview
Problem
Conventional secondary batteries with high safety performance cathode materials face a trade-off between safety enhancement and energy density, where high safety performance cathode materials significantly reduce energy density and increase internal resistance, especially in large-capacity electric vehicle batteries.
Innovation Solution
A cathode plate design featuring a primer layer with a specific surface area 1.2 times that of the ternary active material layer, comprising phosphate, silicate, or spinel cathode active materials, conductive agents, and binders, which reduces interface contact resistance and improves thermal stability by forming a heat insulation layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high content of cathode material having high safety performance is used, then safety performance is improved remarkably, but energy density is reduced significantly and internal resistance increases remarkably
Solution Approach 1:
The cathode plate is segmented into two distinct layers: a primer layer containing cathode material with high safety performance (such as LiFePO4) and a ternary active material layer containing cathode material with high capacity (such as NCM). This segmentation allows each layer to fulfill its specific function - the primer layer provides safety and thermal stability while the ternary layer provides high capacity, thereby resolving the contradiction between safety performance and energy density without requiring the entire cathode to use low-capacity safe materials
Solution Approach 2:
Different regions of the cathode plate are assigned different material compositions and properties. The primer layer uses materials with high thermal stability and safety performance, while the ternary active material layer uses materials with high specific capacity. This local differentiation allows the battery to achieve both high safety performance (from the primer layer) and high energy density (from the ternary layer), eliminating the need to compromise overall energy density for safety
2Reliability
If high content of cathode material having high safety performance is used, then safety performance is improved remarkably, but internal resistance in low state of charge increases remarkably
Solution Approach 1:
The cathode plate is divided into a primer layer and a ternary active material layer, where the ternary layer provides excellent electrical conductivity and low internal resistance characteristics. This segmentation ensures that the high-capacity ternary materials contribute to reducing internal resistance while the primer layer maintains safety performance, thus resolving the contradiction between safety and power characteristics
Solution Approach 2:
The cathode plate employs a composite structure combining two types of cathode materials: safe materials (like LiFePO4) in the primer layer and high-capacity ternary materials (like NCM) in the active material layer. This composite approach leverages the complementary strengths of different materials - the safety and thermal stability of the primer layer combined with the low internal resistance and high conductivity of the ternary layer, achieving both safety performance and low internal resistance simultaneously
3Reliability
If a primer layer with higher specific surface area cathode active material is used, then interface contact resistance is reduced and cycle performance is improved, but manufacturing complexity increases
Solution Approach 1:
The patent specifies particular parameter ranges for the primer layer materials, including cathode active material with specific surface area of 0.5-50m²/g, conductive agent content of 5-30%, and binder content of 20-70%. By optimizing these parameters within defined ranges, the invention achieves good interface contact and cycle performance while maintaining manufacturability, as the parameter ranges are practical for conventional battery manufacturing processes
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 cathode plate design enhances safety performance, reduces internal resistance, and improves cycle performance by increasing contact area and thermal stability, enabling the secondary battery to pass critical safety tests like nailing and overcharge tests.
Implementation Method 1
improving thermal stability by forming a heat insulation layer
Implementation Method 2
increasing the contact area between the primer layer and the ternary active material layer, thereby reducing the interface contact resistance
Data Source
Figure 1
AI summary
The present application provides a secondary battery and a cathode plate thereof. The cathode plate of the secondary battery includes a cathode current collector; a primer layer including a cathode active material, a conductive agent and a binder disposed on the cathode current collector; and a ternary active material layer including a ternary cathode active material disposed on the primer layer; wherein a specific surface area of the cathode active material in the primer layer is no less than 1.2 times of a specific surface area of the ternary cathode active material in the ternary active material layer.