Silicon Anode Binder Ratio for Conductive Network Stability
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Solution Overview
Problem
Lithium secondary batteries using silicon-containing active materials face challenges with volume expansion, leading to conductive path disconnection and reduced lifespan due to inadequate binder performance, which limits the application and commercialization of high-capacity batteries.
Innovation Solution
A negative electrode composition incorporating a binder with a Young's modulus of 103 MPa or more and a strain value of 15% or more, specifically formulated to maintain the conductive network and adhesive strength, is used to address the volume expansion issues of silicon-containing active materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-containing active material is used to increase capacity, then energy density is improved, but volume expansion causes conductive path disconnection and reduced reliability
Solution Approach 1:
The patent uses a composite binder system comprising both aqueous binder (providing dispersibility) and rubber-containing binder (providing adhesiveness and elasticity). This composite binder structure allows the negative electrode to accommodate silicon's volume expansion while maintaining conductive path connectivity and adhesive strength, thus resolving the reliability issue while preserving high capacity.
2Stability of the object's composition
If aqueous binder is used to improve dispersibility, then dispersibility is improved, but adhesive strength decreases leading to conductive path breakage
Solution Approach 1:
The patent merges the advantages of aqueous binder (dispersibility) and rubber-containing binder (adhesive strength) by using them in combination. The aqueous binder ensures good dispersion of silicon particles, while the rubber-containing binder provides sufficient adhesive strength to maintain conductive path connectivity during volume expansion, thus resolving the contradiction between dispersibility and adhesive strength.
3Strength
If rubber-containing binder is used to improve adhesive strength, then adhesive strength is improved, but stiffness is insufficient leading to poor structural stability
Solution Approach 1:
The patent creates a composite binder system where rubber-containing binder provides adhesive strength and elasticity, while aqueous binder contributes to structural stability and stiffness. This composite structure allows the negative electrode to maintain both strong adhesion and structural stability during silicon's volume expansion cycles, resolving the contradiction between adhesive strength and structural stability.
4Stability of the object's composition
If binder polymer with strong stress is used to suppress volume expansion, then volume expansion is suppressed, but electrode thickness increases and performance deteriorates
Solution Approach 1:
The patent changes the key parameters of the binder system by using a combination of aqueous binder and rubber-containing binder in specific proportions. This parameter optimization allows the binder to accommodate volume expansion effectively without requiring excessive binder content, thus maintaining thin electrode structure and high energy density while controlling volume expansion.
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 improves the dispersibility and adhesive strength of silicon-containing active materials, maintaining a stable conductive network and enhancing the lifespan and performance of lithium secondary batteries by controlling volume expansion and contraction.
Implementation Method 1
a second binder having a strain value of 15% or more
Implementation Method 2
a first binder having a Young's modulus of 103 MPa or more
Data Source
AI summary
A negative electrode composition, a negative electrode for a lithium secondary battery including the same, a lithium secondary battery including a negative electrode, and a method a manufacturing the negative electrode. The negative electrode composition includes a silicon-containing active material; a negative electrode conductive material; and a negative electrode binder. The negative electrode binder includes a first binder having a Young's modulus of 1×103 MPa or more and a second binder having a strain value of 15% or more. The negative electrode binder satisfies the equation 1≤X/Y<4, where Y means parts by weight of the first binder based on 100 parts by weight of the negative electrode binder, and X means parts by weight of the second binder based on 100 parts by weight of the negative electrode binder.