Secondary Battery Electrode Drying for Moisture and Adhesion Balance
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Solution Overview
Problem
Conventional methods for preparing secondary battery electrodes face challenges in balancing moisture removal and binder crystallinity, leading to reduced electrode strength and productivity.
Innovation Solution
A method involving a drying process with a partial range of temperatures above the binder's melting point (170°C) and a total drying time of 5 seconds or less, specifically through a three-step drying process from 130°C to 210°C, is employed to reduce moisture while minimizing crystallinity loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If drying is performed at a temperature above the melting point of the binder resin (170°C), then moisture removal efficiency is improved, but crystallinity of the binder resin decreases leading to reduced electrode strength
Solution Approach 1:
The drying process is divided into multiple stages with different temperature ranges. The first drying stage operates at a lower temperature (below the melting point of the binder resin) to preserve crystallinity, while the second drying stage operates at a higher temperature (above the melting point) to efficiently remove moisture. This segmentation allows both moisture removal efficiency and electrode strength to be optimized.
Solution Approach 2:
The first drying stage is performed preliminarily before the second drying stage. By conducting initial moisture removal at a lower temperature that preserves binder resin crystallinity, the electrode structure is stabilized before subsequent high-temperature processing. This preliminary action prevents excessive crystallinity loss while still achieving significant moisture reduction.
2Strength
If drying is performed at a temperature of 170°C or less to preserve binder crystallinity, then electrode strength is maintained, but drying time increases reducing productivity
Solution Approach 1:
The drying process is divided into two sequential stages: a first drying stage at lower temperature (below binder melting point) to maintain crystallinity, and a second drying stage at higher temperature (above binder melting point) to rapidly remove remaining moisture. This segmentation allows the process to achieve both electrode strength preservation and high productivity.
Solution Approach 2:
The drying temperature parameter is dynamically changed during the process. The process transitions from a lower temperature range (preserving crystallinity) to a higher temperature range (enhancing moisture removal). This parameter change allows the system to optimize both electrode strength and drying efficiency at different stages.
3Quantity of substance
If long drying time is used to reduce residual moisture at low temperature, then moisture removal is achieved, but productivity is reduced
Solution Approach 1:
The drying process is segmented into two stages with different temperature and time characteristics. The first stage operates at lower temperature for a moderate duration to remove bulk moisture while preserving crystallinity. The second stage operates at higher temperature for a shorter duration to rapidly eliminate residual moisture. This segmentation achieves thorough moisture removal without requiring excessively long total drying time, thereby maintaining high productivity.
Solution Approach 2:
The drying process maintains continuous useful action by transitioning smoothly between temperature stages. Rather than interrupting the drying process or using excessive time at low temperature, the system continuously removes moisture by adapting the temperature parameter, ensuring efficient moisture removal throughout the entire drying period.
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 effectively reduces moisture in the electrode, enhancing adhesion between the electrode active material layer and the current collector, resulting in improved durability and productivity of lithium secondary batteries.
Implementation Method 1
drying the rolled electrode, wherein the drying is performed such that at least a partial range of drying temperature is 170° C. to 210° C.
Implementation Method 2
the drying is performed such that at least a partial range of drying temperature is above a melting point (170° C.) of a binder
Implementation Method 3
since crystallinity is decreased as the polyvinylidene fluoride (PVDF)-based binder resin melts
Implementation Method 4
at least a partial range of drying temperature is above a melting point (170° C.) of a binder
Data Source
AI summary
A method of preparing an electrode for a secondary battery, which effectively reduces a residual amount of moisture in the electrode and may significantly improve electrode adhesion at the same time, is disclosed. The method of preparing an electrode for a secondary battery includes steps of: preparing an electrode in which an electrode active material layer is formed; rolling the electrode; and drying the rolled electrode. The drying is performed such that a temperature that is from 170° C. to 210° C. is reached during the drying of the rolled electrode. For example, a temperature that is above a melting point (170° C.) of a polyvinylidene fluoride (PVDF)-based binder resin may be reached the during drying of the rolled electrode.