Positive Electrode Edge Coating for Overhang Lithium Plating
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Solution Overview
Problem
Lithium plating in the overhang-specific region of lithium-ion batteries is a significant challenge due to kinetic weak spots, leading to reduced charging speeds and potential energy density losses, especially under extreme conditions like low temperatures.
Innovation Solution
A secondary battery design with a positive active material layer thickness of 30-200 μm, an inert layer with 0.1-6.0% silicon by mass in a 15 μm×15 μm region, and a specific inert layer width and thickness to reduce lithium ion deintercalation speed, alleviating plating issues while maintaining energy density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the charging speed is increased to meet fast-charge requirements, then the charging rate improves, but lithium plating occurs in the overhang-specific region
Solution Approach 1:
The patent applies different treatments to different regions of the positive electrode plate. The overhang-specific region (where the negative electrode extends beyond the positive electrode) is treated with an inert layer or modified positive active material layer, while other regions maintain their original structure. This local differentiation addresses the specific lithium plating problem in the overhang region without compromising the overall charging performance of the battery.
Solution Approach 2:
The patent introduces an inert layer or modified positive active material layer as an intermediary between the electrolyte and the positive active material in the overhang-specific region. This intermediary layer moderates the lithium ion deintercalation rate, preventing excessive lithium flux that leads to plating, while still allowing sufficient ion transport to maintain charging speed in other regions.
2Quantity of substance
If the positive active material layer thickness is increased to improve energy density, then the energy density improves, but the lithium ion deintercalation kinetics worsen
Solution Approach 1:
The patent modifies only the overhang-specific region of the positive electrode plate by applying an inert layer or using modified positive active material. This localized modification addresses the lithium plating issue without requiring reduction of the overall positive active material layer thickness, thereby preserving the high energy density while solving the kinetic problem in the critical overhang region.
3Object-affected harmful factors
If an inert layer is added to reduce lithium ion deintercalation speed and prevent plating, then lithium plating is alleviated, but the energy density decreases
Solution Approach 1:
The inert layer is applied only to the overhang-specific region of the positive electrode plate, not to the entire electrode. This localized application minimizes the total amount of inert material in the battery, thereby reducing the impact on energy density while still providing effective protection against lithium plating in the critical overhang region where the problem occurs.
Solution Approach 2:
The patent applies the inert layer partially rather than completely across the positive electrode plate. By limiting the inert layer to only the overhang-specific region, the solution provides sufficient protection against lithium plating where needed while avoiding excessive use of inert material that would unnecessarily reduce the overall energy density of the battery.
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 solution effectively reduces lithium plating in the overhang-specific region, enhancing charging speed and energy density by controlling the inert layer's properties and thickness, ensuring stable performance even under extreme conditions.
Implementation Method 1
reduces the speed of deintercalating lithium ions from a region covered by the inert layer
Data Source
AI summary
A positive electrode plate includes a positive current collector and a positive active material layer. A thickness of the positive active material layer is D μm, 30≤D≤200. A negative electrode plate includes a negative current collector and a negative active material layer. In a width direction of the positive electrode plate, the negative active material layer includes two opposite first edges, and the positive active material layer includes two opposite second edges. The two second edges are located between the two first edges. An inert layer is provided on a surface of the positive active material layer. The inert layer coincides with at least a part of the second edges. A mass percent of silicon in a region of 15 μm×15 μm on the inert layer is B %, 0.1≤B≤6.0, and 0.15≤BD/100≤12.00.