Battery Separator Lamination Using Solvent-Mediated Binder Melting
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Solution Overview
Problem
Conventional lamination processes for battery cells face issues such as separator shrinkage at high temperatures and non-uniform adhesion between electrodes and separators, as well as pore blocking due to excessive pressure, which affect the performance and reliability of secondary batteries.
Innovation Solution
A method involving the use of a solvent with a boiling point of 90°C or higher, like dimethyl carbonate, to melt the binder polymer on the separator surface at a controlled temperature, allowing for low-temperature lamination without separator shrinkage and minimizing pressure-induced pore blocking, while using a chamber device to vaporize and condense the solvent for efficient application.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If temperature is increased to melt binder polymer and improve adhesion, then adhesion between electrode and separator is improved, but separator shrinks and adhesion becomes non-uniform
Solution Approach 1:
The invention changes the lamination temperature parameter from conventional high temperature (above polymer melting point) to low temperature (below polymer melting point, specifically 60-100°C). This parameter change allows the use of solvent to melt binder polymer instead of thermal melting, thereby achieving good adhesion without separator shrinkage
Solution Approach 2:
The invention introduces solvent as an intermediary substance to facilitate the lamination process. The solvent penetrates the separator and melts the binder polymer at low temperature, enabling adhesion without direct thermal contact that causes shrinkage. The solvent acts as a medium to transfer the melting effect selectively to the binder polymer while leaving the separator structure intact
2Strength
If pressure is increased to improve lamination bonding, then adhesion between electrode and separator is improved, but pores of separator are blocked and cell resistance increases
Solution Approach 1:
The invention replaces the mechanical pressure-based lamination system with a chemical/solvent-based system. Instead of using high pressure to force bonding, the solvent melts the binder polymer chemically, allowing bonding to occur at low pressure. This substitution eliminates pore blocking while maintaining adhesion strength
Solution Approach 2:
The invention changes the primary lamination parameter from pressure to temperature/solvent concentration. By controlling solvent application and low temperature, the process achieves bonding without relying on high pressure, thereby preventing pore blockage and maintaining low cell resistance
3Strength
If high temperature is used for lamination, then binder polymer melts and adhesion is improved, but energy consumption increases and solvent evaporation control becomes difficult
Solution Approach 1:
The invention changes the temperature parameter from high temperature (conventional lamination) to low temperature (60-100°C). This parameter change dramatically reduces energy consumption while achieving the same adhesion effect through solvent-mediated binder polymer melting
Solution Approach 2:
The solvent acts as an intermediary that enables binder polymer melting at low temperature, replacing the need for high thermal energy. The solvent's chemical interaction with the binder polymer achieves the same effect as high-temperature thermal melting but with much lower energy input
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 enables uniform adhesion between electrodes and separators at low temperatures, preventing separator shrinkage and pore blocking, thus enhancing the manufacturing process for lithium secondary batteries and allowing for mass production with reduced human exposure to hazardous solvents.
Implementation Method 1
applying a solvent for lamination to the surface of the separator to be bound with the electrode; and carrying out lamination of the electrode with the separator before the lamination solvent is dried
Implementation Method 2
A method involving the use of a solvent with a boiling point of 90°C or higher, like dimethyl carbonate, to melt the binder polymer on the separator surface at a controlled temperature
Implementation Method 3
using a chamber device to vaporize and condense the solvent for efficient application
Data Source
Figure 1a~1b
Figure 2~3
Figure 4~5
AI summary
The present disclosure provides a method for manufacturing a unit cell including the steps of: preparing an electrode and a separator individually, wherein the separator includes a porous polymer substrate and a porous coating layer disposed on at least one surface of the porous polymer substrate and including a mixture of inorganic particles with a binder polymer; applying a lamination solvent to the surface of the separator to be bound with the electrode; and carrying out lamination of the electrode with the separator before the lamination solvent is dried. The method according to the present disclosure can solve the problem of shrinking of a separator occurring in the conventional lamination process.