Li-Ion Battery Negative Electrode Coating for SEI Suppression
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Solution Overview
Problem
Nonaqueous electrolyte secondary batteries, such as lithium-ion batteries, face issues with irreversible reactions at the negative electrode surface due to the formation of a solid electrolyte interface (SEI), leading to increased internal resistance and reduced battery capacity.
Innovation Solution
A negative electrode with a lithium-ion permeable film is applied to the surface of the active material layer and current collector, which selectively coats the starting points of electrolyte decomposition, reducing SEI formation and maintaining battery capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the surface of carbon material is coated with lithium compound (LiXSiyOz) to suppress SEI production, then the effect of suppressing SEI occurrence is improved, but the internal resistance of negative electrode active material layer increases due to the substantially no electron conductivity of lithium compound
Solution Approach 1:
The patent applies local quality by creating a dual-layer coating structure where the lithium compound layer is positioned specifically at the interface between carbon material and electrolyte to suppress SEI formation, while a conductive material layer is applied over it to restore electron conductivity. Each layer performs its specific function locally without interfering with the other's primary role.
Solution Approach 2:
The patent uses composite materials by combining lithium compound (for SEI suppression) with conductive material (for electron transport) in a layered structure. This composite approach allows the negative electrode to simultaneously achieve both SEI suppression and adequate electron conductivity, resolving the contradiction between these two properties.
2Reliability
If more lithium compound is used to coat the carbon material surface, then the SEI suppression effect is enhanced, but the internal resistance increases further due to the insulating nature of lithium compound
Solution Approach 1:
The patent applies parameter changes by adjusting the thickness and composition ratios of the two layers. The lithium compound layer thickness is optimized to provide sufficient SEI suppression, while the conductive material layer thickness is adjusted to ensure adequate electron conductivity. This parameter optimization allows the system to achieve the desired balance between SEI suppression and electrical 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
This approach effectively decreases SEI production and suppresses the increase in internal resistance, thereby enhancing the battery's performance and capacity retention.
Implementation Method 1
a first film which has lithium ion permeability and which coats at least a portion of the surface of the negative electrode active material layer
Data Source
AI summary
A method for producing a negative electrode for a nonaqueous electrolyte secondary battery, and a nonaqueous electrolyte secondary battery obtained therewith are disclosed. The negative electrode includes a negative electrode current collector, a negative electrode active material layer provided on the surface of the negative electrode current collector, and a first film which has lithium ion permeability and which coats at least a portion of the surface of the negative electrode active material layer and partially coats the surface of the negative electrode current collector. The first film preferably contains a first lithium compound containing an element M1, an element A1, and lithium. Herein, M1 is at least one selected from the group consisting of P, Si, B, V, Nb, W, Ti, Zr, Al, Ba, La, and Ta; and A1 is at least one selected from the group consisting of F, S, O, N, and Br.