Layered Positive Electrode Sheet for Fast Charging at Low Temperature
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Solution Overview
Problem
Existing secondary batteries exhibit poor low-temperature rate capability, fast-charging performance, and cycle life, particularly due to limitations in lithium ion conduction and material stability.
Innovation Solution
A positive electrode plate design incorporating a first and second positive electrode active material, where the second active material has a higher lithium ion diffusion coefficient and compaction density, enhancing lithium ion conduction and stability, and is combined with a specific mass ratio and cladding layer to improve low-temperature power and fast-charging performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single positive electrode active material is used, then the battery structure is simple, but the low-temperature rate capability and fast-charging performance are poor
Solution Approach 1:
The positive electrode film layer is segmented into two distinct layers: a first positive electrode film layer containing first positive electrode active material (e.g., lithium iron phosphate) and a second positive electrode film layer containing second positive electrode active material (e.g., lithium nickel cobalt manganese oxide). This segmentation allows each layer to contribute different functional properties, with the first layer providing stability and the second layer providing high lithium ion diffusion coefficient, thereby improving low-temperature rate capability and fast-charging performance without requiring complete redesign of the battery structure
Solution Approach 2:
The patent employs composite materials by combining two different positive electrode active materials in a layered configuration. The first positive electrode active material (such as lithium iron phosphate) offers high stability and safety, while the second positive electrode active material (such as lithium nickel cobalt manganese oxide) provides high lithium ion diffusion coefficient. This composite structure synergistically improves both low-temperature rate capability and fast-charging performance while maintaining structural integrity
2Productivity
If materials with high lithium ion diffusion coefficient are used, then the fast-charging performance is enhanced, but the material stability decreases
Solution Approach 1:
Different regions of the positive electrode film layer are assigned different material compositions tailored to specific functional requirements. The second positive electrode film layer (closer to the electrolyte) contains material with high lithium ion diffusion coefficient for fast charging, while the first positive electrode film layer (closer to the current collector) contains highly stable material for structural support and safety. This local differentiation resolves the contradiction between fast-charging performance and material stability
Solution Approach 2:
The patent uses composite materials with complementary properties: the first positive electrode active material (e.g., lithium iron phosphate) provides high stability and structural integrity, while the second positive electrode active material (e.g., lithium nickel cobalt manganese oxide) provides high lithium ion diffusion coefficient. The layered composite structure allows both materials to function simultaneously, achieving both fast-charging performance and material stability
3Quantity of substance
If the positive electrode film layer is made thicker to increase capacity, then the energy density improves, but the lithium ion conduction rate decreases
Solution Approach 1:
The positive electrode film layer is divided into two thinner sub-layers instead of one thick layer. The first positive electrode film layer and the second positive electrode film layer each have reduced thickness compared to a single equivalent thick layer, which shortens the lithium ion diffusion path. This segmentation maintains or increases total capacity while improving lithium ion conduction rate and fast-charging performance
Solution Approach 2:
The patent introduces a vertical dimension to the electrode structure by creating a layered configuration with the first positive electrode film layer adjacent to the current collector and the second positive electrode film layer adjacent to the electrolyte. This dimensional arrangement optimizes lithium ion transport pathways, allowing ions to access different material regions more efficiently and maintaining high conduction rates even with increased overall capacity
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 improves low-temperature power and rate capability, extends battery endurance, and enhances fast-charging performance and cycle life by optimizing lithium ion conduction and material stability.
Implementation Method 1
the second positive electrode active material has a higher lithium ion diffusion coefficient
Implementation Method 2
a positive electrode plate, a battery, and an electric device... improves the low-temperature power and the low-temperature rate capability
Data Source
AI summary
A positive electrode sheet, a battery, and an electric device. The positive electrode sheet of the present application comprises a positive electrode current collector and a positive electrode film layer provided on at least one surface of the positive electrode current collector, wherein the positive electrode film layer comprises a first positive electrode film layer provided on the surface of the positive electrode current collector and a second positive electrode film layer provided on the surface of the first positive electrode film layer. The first positive electrode film layer comprises a first positive electrode active material, and the second positive electrode film layer comprises a second positive electrode active material; and the first positive electrode active material comprises compound LiaAbMn1-cBcP1-dRdO4-nDn, and the second positive electrode active material comprises compound LixNiyCozMkMepOrEm.