Non-aqueous Electrolyte Battery Binder for Uniform SEI Formation
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Solution Overview
Problem
Non-aqueous electrolyte secondary batteries using aqueous binders for negative electrode active material layers face issues with non-uniform film (SEI) formation due to excessive electrolyte solution, leading to inadequate long-term cycle characteristics.
Innovation Solution
Optimizing the ratio of residual space to pore volume inside the battery casing and the volume of injected electrolyte solution to maintain a uniform distance between electrode layers, ensuring the electrolyte solution is adequately absorbed, thereby promoting uniform SEI formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an aqueous binder is used for forming the negative electrode active material layer, then the binding effect is improved and active material ratio is increased, but the electrolyte solution distribution becomes non-uniform due to excessive residual electrolyte
Solution Approach 1:
The invention changes the physical-chemical parameters of the binder by specifying that it must contain carboxyl groups with a specific content range (0.1-5.0 mmol/g). This parameter modification enables the binder to achieve both strong binding effect and proper electrolyte absorption, resolving the contradiction between binding effectiveness and electrolyte distribution uniformity.
2Quantity of substance
If the amount of electrolyte solution is increased to ensure adequate absorption, then the binder performance is improved, but the distance between electrode layers is widened causing non-uniform SEI formation
Solution Approach 1:
The binder acts as an intermediary substance that mediates between the electrolyte solution and the electrode structure. By incorporating carboxyl groups with specific content, the binder selectively absorbs electrolyte to an appropriate extent, preventing both deficiency and excessive absorption that would widen electrode distances and cause non-uniform SEI formation.
3Ease of manufacture
If an aqueous binder is used to reduce production cost and environmental burden, then the manufacturing cost is reduced, but the long-term cycle characteristics are insufficient due to non-uniform film formation
Solution Approach 1:
The invention modifies the chemical composition parameters of the aqueous binder by specifying carboxyl group content (0.1-5.0 mmol/g), which fundamentally changes the binder's interaction with electrolyte. This parameter optimization enables aqueous binders to achieve both cost-effectiveness and adequate long-term cycle characteristics through uniform SEI formation.
Solution Approach 2:
The invention creates a composite functional system where the aqueous binder with carboxyl groups forms a composite structure with the negative electrode active material and SEI layer. This composite material approach enables the binder to simultaneously provide binding function, controlled electrolyte absorption, and uniform SEI formation, resolving the contradiction between low cost and long-term reliability.
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
This approach enhances the long-term cycle characteristics of non-aqueous electrolyte secondary batteries by preventing non-uniform reactions and ensuring effective electrolyte distribution, leading to improved battery performance.
Implementation Method 1
due to the fact that the aqueous binder was less likely to be swollen with respect to the electrolyte solution, the amount of the electrolyte solution, which was not absorbed by the binder and was present in the residual space inside the outer casing
Data Source
Figure 1
Figure 2(A)~2(B)
AI summary
[Object] To provide a means for enabling a reaction for forming a film (SEI) on a surface of a negative electrode active material to proceed more uniformly in a case where an aqueous binder is used as a binder for a negative electrode active material layer in a non-aqueous electrolyte secondary battery. [Solving Means] Provided is a non-aqueous electrolyte secondary battery having a power generating element enclosed inside an outer casing, wherein the power generating element includes a positive electrode having a positive electrode active material layer formed on a surface of a positive electrode current collector, a negative electrode having a negative electrode active material layer containing an aqueous binder formed on a surface of a negative electrode current collector, and a separator holding an electrolyte solution, wherein the ratio value (V2/V1) of a volume V2 of a residual space inside the outer casing to a volume V1 of pores of the power generating element is 0.4 to 0.5, and the ratio value (L/V2) of a volume L of the electrolyte solution injected to the outer casing to the volume V2 of the residual space inside the outer casing is 0.6 to 0.8.