Nonaqueous Electrolyte Battery Coating Uniformity
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Nonaqueous electrolyte secondary batteries, such as lithium-ion batteries, face capacity retention rate issues due to non-uniform coating formation on the negative electrode active material, leading to decreased cycling characteristics.
Innovation Solution
A method involving a two-step electrolyte injection process, where a nonaqueous electrolyte with an additive is first injected and charged to form a coating on the negative electrode active material, followed by a second injection of electrolyte without the additive, ensuring uniform coating distribution and maintaining capacity retention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a nonaqueous electrolyte containing an additive is injected and charged to form a coating on the negative electrode active material, then the coating amount increases, but the coating distribution becomes non-uniform (with large amounts at end portions and small amounts at central portion)
Solution Approach 1:
The patent divides the coating formation process into multiple sequential charging steps. In each step, the battery is charged to a specific voltage range where the additive decomposes and forms coating. By segmenting the charging process and controlling voltage ranges, the patent achieves more uniform coating distribution across the electrode surface compared to single-step charging.
Solution Approach 2:
The patent performs preliminary coating formation by charging the battery to specific voltage ranges before final charging. This preliminary action allows the additive to decompose and form initial coating layers that prevent excessive coating accumulation during subsequent charging, thereby improving overall coating uniformity.
2Reliability
If the coating amount on the negative electrode active material is increased to protect the surface, then the capacity retention rate decreases due to charge carrier immobilization in the SEI layer
Solution Approach 1:
The patent changes the charging voltage parameters during coating formation, using multiple voltage ranges (e.g., first charging to a first voltage range, then to a second voltage range). This parameter variation allows controlled decomposition of the additive at different stages, forming adequate protective coating while minimizing excessive coating that would immobilize charge carriers and reduce capacity.
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 results in a lithium-ion secondary battery with improved capacity retention rate by minimizing coating non-uniformity across the negative electrode active material, enhancing the battery's performance and longevity.
Implementation Method 1
an additive that decomposes at or above a predetermined charging voltage and forms a coating on the surface of the negative electrode active material
Implementation Method 2
nonaqueous electrolyte secondary batteries such as lithium ion secondary batteries
Data Source
AI summary
The present invention provides a method for producing a nonaqueous electrolyte secondary battery in which the drop in capacity retention rate is controlled by forming a coating in a more favorable state on the surface of the negative electrode active material. This production method comprises a step S10 of preparing a battery assembly in which an electrode assembly is housed within a battery case, the electrode assembly including a positive electrode produced by forming a positive electrode active material layer containing at least a positive electrode active material, and a negative electrode produced by forming a negative electrode active material layer containing at least a negative electrode active material; a first injection step S20 of injecting a nonaqueous electrolyte containing a specified additive into the battery case; a precharging step S30 of forming the additive-derived coating on the surface of the negative electrode active material; a second injection step S40 of injecting a nonaqueous electrolyte not containing an additive into the battery case; and a charge and discharge step S50 of charging and discharging the battery assembly to a predetermined charging and discharge voltage.