Negative Electrode Oxetane Additive Coating for Battery Cycle Life
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Solution Overview
Problem
In lithium ion secondary batteries, the use of coating-forming additives in the electrolyte solution leads to decomposition products that increase viscosity and reduce ion conductivity, causing battery characteristics to deteriorate, and the additives can clump or separate during slurry production, making uniform electrode preparation impossible, which affects cycle lifetime and capacitance.
Innovation Solution
A negative electrode with a coating-forming additive, specifically oxetane compounds, is used within a specific concentration range (0.001% to 5.0% by mass based on the negative electrode active material), which forms a polymer coating on the surface, preventing additive elution and maintaining electrolyte conductivity, and is dispersed in the slurry to prevent clumping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a coating-forming additive is added to the electrolyte solution, then a protective coating is formed on the negative electrode surface improving battery characteristics, but the additive decomposes on the positive electrode increasing electrolyte viscosity and reducing ion conductivity
Solution Approach 1:
The invention divides the additive application into two separate locations: the coating-forming additive is incorporated into the negative electrode slurry rather than the electrolyte solution, while the positive electrode receives a different protective coating formed from compounds in the electrolyte solution. This segmentation prevents the coating-forming additive from contacting and decomposing on the positive electrode, eliminating the harmful viscosity increase and ion conductivity reduction.
Solution Approach 2:
The invention introduces a mediator approach by using different coating-forming compounds for the positive and negative electrodes. The positive electrode uses compounds like cyclic carbonates or chain carbonates from the electrolyte solution, while the negative electrode uses the coating-forming additive in the slurry, preventing direct harmful interactions while still achieving protective coating formation on both electrodes.
2Reliability
If a coating-forming additive is added to the electrolyte solution, then a protective coating is formed on the negative electrode, but remaining additive continues to react during charging/discharging increasing internal resistance
Solution Approach 1:
The invention applies preliminary action by incorporating the coating-forming additive into the negative electrode slurry before electrode assembly, ensuring the protective coating is formed during initial electrode fabrication rather than during battery operation. This preliminary coating formation eliminates the need for continuous additive consumption during charging/discharging cycles, preventing internal resistance increase from repeated coating growth.
3Reliability
If a coating-forming additive is added to the electrolyte solution, then a protective coating is formed on the negative electrode, but the additive has poor storage stability due to high reactivity
Solution Approach 1:
The invention extracts the coating-forming additive from the electrolyte solution and incorporates it directly into the negative electrode slurry. This extraction removes the highly reactive additive from the electrolyte environment where it would decompose during storage, while still allowing it to form the necessary protective coating on the negative electrode surface during battery operation.
4Reliability
If a large amount of coating-forming additive is added to the slurry, then sufficient coating is formed on the negative electrode, but the additive clumps or separates during slurry production making uniform electrode preparation impossible
Solution Approach 1:
The invention applies parameter changes by optimizing the concentration of the coating-forming additive in the negative electrode slurry to a specific range (0.01-5% by mass). This parameter optimization ensures sufficient coating formation on the negative electrode while maintaining slurry homogeneity during production, preventing clumping and separation that would occur at higher concentrations.
5Reliability
If a large amount of coating-forming additive is added to the slurry, then sufficient coating is formed on the negative electrode, but the additive attaches to the binder reducing binding effect and deteriorating adhesion properties
Solution Approach 1:
The invention optimizes the concentration parameter of the coating-forming additive in the slurry to 0.01-5% by mass, which provides sufficient coating formation on the negative electrode without excessive additive available to attach to the binder. This parameter control ensures the binder maintains its binding function and adhesion properties are not deteriorated.
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 cycle characteristics of lithium ion secondary batteries by maintaining electrolyte conductivity and preventing additive elution, thereby reducing internal resistance and improving battery performance.
Implementation Method 1
additives are added to the electrolyte solution to form a film called protective coating (or coating, SEI) derived from the additives on the surface of the negative electrodes utilizing an electrochemical reaction in a charge/discharge process
Implementation Method 2
the additive is a compound having a specific structure (oxetane compound), which can form a polymer coating on the surface of a negative electrode
Data Source
AI summary
The present invention relates to a negative electrode for a lithium ion secondary battery comprising an oxetane compound represented by a predetermined formula in an amount within a range of 0.001% by mass or more and 5.0% by mass or less based on the amount of a negative electrode active material, and a lithium ion secondary battery using the same.