Negative Electrode Sheet Binder Particle Sizing for Silicon Expansion
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Solution Overview
Problem
Lithium-ion batteries face challenges with silicon-based materials due to severe volume expansion during cycling, leading to poor cycle and rate performance, which limits their application in high-energy density and power requirements.
Innovation Solution
A negative electrode sheet with a silicon-based material and a binder having an average-volume particle diameter of 0.1-0.8 µm is used, enhancing binding force and suppressing volume expansion, while maintaining stability and minimizing binder use.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If silicon-based material is used as negative electrode active material, then energy density is improved, but volume expansion occurs during cycling leading to poor cycle performance
Solution Approach 1:
The patent changes the particle size parameter of the binder to a specific range (0.1-0.8 μm average volume particle diameter) to optimize its ability to fill pores and bind silicon particles. This parameter change enables the binder to effectively suppress volume expansion of silicon-based material during cycling while maintaining high energy density, thus resolving the contradiction between energy density improvement and cycle performance deterioration
Solution Approach 2:
The patent introduces a binder with specific particle size characteristics as an intermediary substance between silicon-based active material particles. This intermediary binder fills the large pore regions and provides binding force to suppress volume expansion, mediating between the high energy density requirement of silicon material and the cycle performance requirement, thereby resolving the contradiction
2Reliability
If binder amount is increased to suppress volume expansion, then cycle performance is improved, but energy density decreases due to excessive binder use
Solution Approach 1:
The patent optimizes the particle size parameter of the binder (0.1-0.8 μm average volume diameter) to maximize its efficiency in suppressing volume expansion. This parameter optimization allows achieving good cycle performance with minimized binder content, thereby preventing energy density decrease while maintaining cycle performance improvement
3Power
If porosity is large due to irregular particle shape, then power performance is improved, but binding force is insufficient leading to severe volume expansion
Solution Approach 1:
The patent applies local quality by using a binder with specific particle size (0.1-0.8 μm) that is optimized to fill the large pore regions created by irregularly shaped silicon particles. This localized filling provides enhanced binding force precisely where needed (in the pore regions) without requiring uniform increase in binder content throughout, thus maintaining power performance while improving binding force to suppress volume expansion
Solution Approach 2:
The binder acts as an intermediary that fills the large pore regions created by irregular particle shapes. It provides the necessary binding force in these specific regions to suppress volume expansion, while maintaining the overall porosity structure that enables good power performance, thus mediating between binding force requirement and power performance
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 improves the battery's energy density, power, and cycle performance by stabilizing the silicon-based material, ensuring high binding force and reduced expansion, thus achieving better rate and cycle performance.
Implementation Method 1
A binder whose average-volume particle diameter Dv50 is 0.1-0.8 μm is added to the negative electrode film layer, to not only increase active binding sites, but also effectively fill and bind a large pore region of the electrode sheet
Data Source
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AI summary
Disclosed are a negative electrode sheet, a battery cell, a battery, and an electric device. The negative electrode sheet includes a negative electrode current collector and a negative electrode film layer provided on at least one side of the negative electrode current collector. The negative electrode film layer includes a negative electrode active material and a binder, and the negative electrode active material includes a silicon-based material. An average-volume particle diameter Dv50 of the binder is 0.1-0.8 µm. The battery has relatively high energy density, power, and relatively good cycle performance.