Pre-Lithiated Negative Electrode Drying to Prevent Moisture Uptake
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Solution Overview
Problem
The existing methods for preparing negative electrodes in lithium secondary batteries face challenges such as increased irreversible capacity, resistance, and reduced safety due to moisture absorption, which degrades battery life characteristics during the pre-lithiation process.
Innovation Solution
A method involving the formation of a simple cell with a preliminary negative electrode, separator, and lithium metal, followed by immersion in an electrolyte solution, separation, washing, and sequential drying at room temperature and 30°C to 70°C in a vacuum state to effectively remove moisture and non-aqueous solvents, thereby reducing irreversible capacity and improving battery safety and life characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If a drying process is performed to remove solvent from the pre-lithiated negative electrode, then the solvent is removed, but moisture is inevitably absorbed by the negative electrode and SEI
Solution Approach 1:
The patent performs the drying process in an inert atmosphere (nitrogen or argon) to prevent moisture absorption during solvent removal. The negative electrode is dried in a glove box or vacuum dryer filled with inert gas, creating a protective environment that eliminates harmful moisture interaction while maintaining effective solvent evaporation.
Solution Approach 2:
The patent optimizes drying parameters including temperature control (room temperature to 60°C), time duration (1-24 hours), and pressure conditions (vacuum or inert atmosphere) to achieve complete solvent removal while minimizing moisture absorption. By carefully adjusting these parameters, the process removes harmful substances without introducing new problems.
2Stability of the object's composition
If moisture is present in the pre-lithiated negative electrode, then the electrode structure is maintained, but excessive HF is generated and battery life is degraded
Solution Approach 1:
The patent extracts moisture from the pre-lithiated negative electrode through multiple washing steps using dry electrolyte solution or non-aqueous solvents, followed by thorough drying processes. This removal of harmful moisture prevents subsequent HF generation and maintains battery reliability while preserving the electrode's structural integrity through controlled processing.
Solution Approach 2:
The patent performs preliminary drying and moisture removal steps before assembling the complete battery cell. By removing moisture in advance during the electrode preparation stage, the process prevents harmful chemical reactions (HF generation) that would occur during battery operation, thereby extending battery life while maintaining structural stability.
3Productivity
If high temperature drying is used to remove moisture quickly, then drying speed increases, but adhesion between negative electrode active material and current collector decreases
Solution Approach 1:
The patent optimizes the drying temperature parameter within a specific range (room temperature to 60°C) to achieve the right balance between drying efficiency and adhesion preservation. This controlled temperature parameter change allows sufficient moisture removal while preventing thermal degradation of the binder and active material adhesion to the current collector.
Solution Approach 2:
The patent employs a continuous or extended drying process at moderate temperatures rather than rapid high-temperature drying. This continuous action at optimized parameters ensures thorough moisture removal over time while maintaining the thermal conditions necessary for preserving strong adhesion between the active material and current collector.
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 eliminates irreversible capacity, reduces battery resistance, enhances safety, and maintains adhesion between negative electrode active material particles and the current collector, leading to improved battery performance and extended lifespan.
Implementation Method 1
performing second drying on the first dried preliminary negative electrode at a temperature of 30°C to 70°C in a vacuum state
Implementation Method 2
effectively remove moisture of the pre-lithiated negative electrode
Data Source
AI summary
The present invention relates to a method of preparing a negative electrode which includes the steps of: forming a simple cell by sequentially stacking a preliminary negative electrode, a separator, and a lithium metal, applying a current after the simple cell is immersed in an electrolyte solution containing a lithium salt and a solvent, separating the preliminary negative electrode from the simple cell after removing the simple cell immersed in the electrolyte solution from the electrolyte solution, washing the separated preliminary negative electrode, performing first drying on the washed preliminary negative electrode at room temperature, and performing second drying on the first dried preliminary negative electrode at a temperature of 30°C to 70°C in a vacuum state.