Lithium Secondary Battery Activation for Stable SEI Formation
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Solution Overview
Problem
Existing lithium secondary battery production methods face issues with non-uniform and unstable formation of the solid electrolyte interface (SEI) film, leading to gas generation and capacity degradation due to reactions between the electrolyte solvent and electrodes during the activation process.
Innovation Solution
A method involving the injection of a first electrolyte with an additive for SEI film formation, followed by pre-aging, primary charging with stepwise and pulse charging/discharging, degassing, and then injecting a second electrolyte without the additive, to stabilize and uniformly form the SEI film.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If initial charging is performed to form SEI film, then the SEI film is formed on the negative electrode, but gas is generated by reaction between electrolyte solvent and electrode
Solution Approach 1:
The patent applies preliminary action by injecting a first electrolyte containing an SEI film-forming additive before the main electrolyte, and performing pre-aging and stepwise primary charging to form a stable SEI film in advance. This preliminary SEI film formation prevents subsequent gas generation reactions between the electrolyte solvent and electrode during normal operation
Solution Approach 2:
The patent converts the harmful gas-generating reaction into a beneficial process by controlling the initial charging to form a protective SEI film. The same reaction that generates gas is harnessed to create a stable interface layer that prevents further unwanted reactions. The additive in the first electrolyte directs the reaction to form a stable SEI film rather than continuous gas generation
2Device complexity
If conventional electrolyte injection and charging methods are used, then the production process is simple, but the SEI film is not uniformly or stably formed
Solution Approach 1:
The patent segments the electrolyte injection process into two distinct stages: first injecting a small amount of electrolyte containing an SEI film-forming additive, then injecting the main electrolyte. It also segments the charging process into pre-aging and stepwise primary charging phases. This segmentation allows each stage to perform its specific function optimally, resulting in stable and uniform SEI film formation
Solution Approach 2:
The patent applies parameter changes by controlling the charging current to gradually increase during primary charging, and by adjusting the composition of the electrolyte (adding SEI film-forming additive in the first electrolyte). These parameter changes optimize the SEI film formation process, ensuring uniform and stable film formation while maintaining a manageable production process
3Reliability
If SEI film is formed during initial charging, then lithium ion reaction with carbon negative electrode is prevented, but gas generation repeats during aging process
Solution Approach 1:
The patent performs preliminary action by forming a stable SEI film during pre-aging and primary charging before the battery enters the aging process. The SEI film-forming additive in the first electrolyte ensures that a robust protective layer is established in advance, which remains stable during the aging process and prevents repeated gas generation reactions
Solution Approach 2:
The patent introduces an SEI film-forming additive as an intermediary substance that mediates the interaction between the electrolyte and the electrode. This additive facilitates the formation of a stable SEI film that acts as a protective intermediary layer, preventing direct harmful reactions between the electrolyte solvent and the electrode during aging
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 minimizes gas generation and enhances the stability of the SEI film, reducing resistance and improving the performance of the final battery cell.
Implementation Method 1
an additive for forming a solid electrolyte interface (SEI) film is injected into a battery cell
Implementation Method 2
charging and discharging proceed by repeating a process of intercalating and deintercalating lithium ions from a lithium metal oxide of the positive electrode to a carbon-based negative electrode
Implementation Method 3
the SEI film acts as an ion tunnel to allow only lithium ions to pass through
Data Source
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AI summary
A method of producing a lithium secondary battery according to the present invention allows a SEI film to be more easily formed by a stepwise charging process of gradually increasing the magnitude of a charging current or a stepwise charging & pulse charging and discharging in primary charging after injection of a first electrolyte and also allows the formed SEI film to be stabilized, and thus gas generated during an activation process can be further reduced, and the resistance of a final battery cell produced by the method can be reduced.