Graphite Negative Electrode Surface Area for Stable Battery SEI
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Solution Overview
Problem
Carbon-based negative electrode materials in lithium manganese iron phosphate secondary batteries suffer from high-temperature cycling performance and storage performance deterioration due to continuous side reactions on the negative electrode surface, damaging the SEI film.
Innovation Solution
A negative electrode plate with a graphite negative electrode active material having a controlled BET specific surface area, specifically 0.5 m2/g ≤ A ≤ 1.3 m2/g, is used to reduce the effective surface area for reactions, thereby stabilizing the SEI film and improving cycling and storage performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If carbon-based negative electrode materials are used in lithium manganese iron phosphate secondary batteries, then the battery can achieve good kinetic performance and charging capability, but the high-temperature cycling performance and storage performance significantly deteriorate due to continuous side reactions on the negative electrode surface
Solution Approach 1:
The patent applies parameter changes by precisely controlling the BET specific surface area of graphite negative electrode active material within the range of 0.5-1.3 m2/g. This parameter optimization reduces the effective surface area for side reactions while maintaining adequate lithium ion insertion/extraction sites, thereby improving high-temperature cycling performance and storage performance without significantly compromising charging capability
Solution Approach 2:
The patent implements local quality by creating a heterogeneous negative electrode structure with different graphite particle sizes and surface areas. By having a distribution of particle dimensions, smaller particles provide high surface area for kinetic performance while larger particles reduce overall reactive surface area, creating local variations that balance charging capability with cycling stability
2Reliability
If the specific surface area of graphite negative electrode material is reduced to decrease side reactions, then the stability of SEI film improves, but the kinetic performance and charging capability may be affected
Solution Approach 1:
The patent optimizes the BET specific surface area parameter to a specific range (0.5-1.3 m2/g) that balances two competing requirements: low enough to reduce side reactions and stabilize SEI film, but high enough to maintain adequate kinetic performance for charging capability
Solution Approach 2:
The patent applies partial action by not minimizing the surface area to the extreme, but rather selecting an optimal intermediate value within the 0.5-1.3 m2/g range that provides sufficient surface area for acceptable kinetic performance while adequately reducing side reactions to stabilize the SEI film
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 controlled BET specific surface area of the graphite negative electrode material enhances the stability of the SEI film, leading to improved cycling and storage performance of the battery without affecting charging capability.
Implementation Method 1
a BET specific surface area of the first graphite negative electrode active material is denoted as A, and a BET specific surface area of the negative electrode active material in the negative electrode film layer is denoted as B, where A≤B
Data Source
AI summary
A negative electrode plate, a secondary battery, and an electric apparatus. The negative electrode plate includes a current collector and a negative electrode film layer disposed on at least one side of the current collector, where the negative electrode film layer includes one or more active material layers, a negative electrode active material in the negative electrode film layer includes a first graphite negative electrode active material, a BET specific surface area of the first graphite negative electrode active material is denoted as A, and a BET specific surface area of the negative electrode active material in the negative electrode film layer is denoted as B, where A≤B, or a BET specific surface area of a material forming the negative electrode film layer is denoted as B′, where A<B′.