Secondary Battery Assembly Heating for Electrode-Separator Adhesion
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Solution Overview
Problem
Existing methods for manufacturing secondary batteries, such as lithium ion batteries, face challenges in achieving sufficient adhesive strength between the electrodes and the separator, which can lead to irregular charging and discharging reactions and reduced high-rate characteristics due to compromised air permeability when pressurizing the electrodes and separator.
Innovation Solution
A manufacturing method involving a high temperature treatment step under a restraining pressure of at least 0.35 MPa and a temperature of at least 80°C, where the peel strength relationship between the separator and the negative electrode active material layer, the negative electrode current collector, and the negative electrode active material layer is optimized to ensure strong adhesion without excessive air permeability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If press pressure is strengthened to enhance adhesive strength between electrode and separator, then adhesive strength is improved, but air permeability of separator is increased which hinders ion transfer and reduces high rate characteristics
Solution Approach 1:
The invention changes the temperature parameter to 80°C or higher during the pressing process. This temperature change enables the adhesive layer to activate and provide sufficient adhesion at lower press pressures (0.01-0.5 MPa), thereby avoiding the need for high press pressure that would damage separator air permeability and ion transfer characteristics.
2Productivity
If press pressure is reduced to maintain separator air permeability, then ion transfer is improved, but adhesive strength between electrode and separator becomes insufficient
Solution Approach 1:
The invention introduces temperature as a controlling parameter, setting it to 80°C or higher. This temperature parameter enables the adhesive layer to become active and provide sufficient bonding strength even when press pressure is kept low (0.01-0.5 MPa), thus preserving separator air permeability and ion transfer capabilities while achieving adequate adhesion.
Solution Approach 2:
The invention applies local quality by having the adhesive layer specifically positioned at the interface between the electrode and separator. This localized adhesive layer provides targeted bonding strength exactly where needed, allowing the rest of the separator to maintain its original air permeability and ion transfer properties without being compromised by high press pressure.
3Strength
If heating and pressing is applied to improve adhesion, then adhesive strength increases, but irregularity in charging and discharging reaction occurs due to local distance increase between electrodes
Solution Approach 1:
The invention optimizes the temperature parameter to 80°C or higher, which activates the adhesive layer to provide uniform and sufficient adhesion across the entire electrode-separator interface. This uniform adhesion prevents local distance increases between electrodes, ensuring regular and reliable charging and discharging reactions without the need for excessive press pressure.
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 method enhances the adhesive strength between the electrodes and the separator, maintaining favorable battery performance, including high-rate characteristics and input/output characteristics, while preventing peeling and ensuring smooth ion transfer.
Implementation Method 1
the battery assembly is bound with the adhesive included in the adhesion layer of the separator swollen
Implementation Method 2
the adhesive included in the adhesion layer of the separator swollen
Data Source
AI summary
A method for manufacturing a secondary battery herein disclosed includes: an assembly preparing step of accommodating an electrode body and an electrolyte into a battery case, and preparing a battery assembly; and a high temperature treatment step of restraining the battery assembly under a restraining pressure of at least 0.35 MPa or more, and retaining the battery assembly so that the temperature of the battery assembly may become at least 80° C. or more. Herein, the high temperature treatment step is carried out so as to satisfy a formula (1): A≥B>C; where A (N/m) represents a peel strength at an interface between a separator and a negative electrode active material layer, B (N/m) represents a peel strength at an interface between the negative electrode active material layer and a negative electrode current collector, and C (N/m) represents a peel strength in the negative electrode active material layer.