Negative Electrode Heat Resistant Layer Drying for Bonding Strength
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Solution Overview
Problem
The existing manufacturing methods for belt-shaped negative electrodes in lithium-ion secondary batteries increase battery resistance and decrease performance due to the addition of binders for securing bonding strength between the electrode and the separator.
Innovation Solution
A manufacturing method involving the application of a heat-resistant layer with a binder to the active material layer on a copper foil, where the layer is dried in two stages: initially at a high temperature to promote binder migration to the surface and subsequently at a lower temperature to ensure thorough drying without excessive binder usage, thereby securing bonding strength without increasing battery resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a binder is added to the heat resistant layer to secure bonding strength between the negative electrode and separator, then bonding strength is improved, but battery resistance increases and battery performance decreases
Solution Approach 1:
The patent changes the drying temperature parameter in two stages: first at a high temperature (100°C to 200°C) to promote binder migration to the surface layer, then at a lower temperature to complete drying. This parameter change enables the binder to concentrate at the surface where it is needed for bonding, rather than being dispersed throughout the bulk material, thus achieving sufficient bonding strength with less overall binder content and minimizing battery resistance
Solution Approach 2:
The patent creates local quality by concentrating the binder in the surface layer of the heat resistant layer through high-temperature drying. This ensures that the binder is positioned exactly where it is needed - at the interface between the negative electrode and separator for bonding - rather than being uniformly distributed throughout the entire heat resistant layer, reducing the total binder quantity required
2Strength
If a high drying temperature is used to promote binder migration to the surface layer, then bonding strength is improved, but the copper foil may burn
Solution Approach 1:
The patent segments the drying process into two distinct stages with different temperature conditions. The first stage uses high temperature (100°C to 200°C) to promote binder migration to the surface layer. The second stage uses a lower temperature to complete the drying process. This segmentation allows the high temperature to be applied only briefly for the specific purpose of binder migration, after which the temperature is reduced to prevent copper foil burning, thus achieving bonding strength improvement without causing harmful effects
Solution Approach 2:
The high-temperature drying step is performed as a preliminary action before the main drying process. This preliminary high-temperature treatment promotes binder migration to the surface layer, preparing the binder for its bonding function. After this preliminary action is complete, the temperature is reduced for the remaining drying process, preventing copper foil burning while having already achieved the desired binder distribution
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 bonding strength between the negative electrode and the separator, reducing the need for additional adhesives and minimizing battery performance degradation, while preventing copper foil burning during the drying process.
Implementation Method 1
in the first step performed at an early stage of the drying, the active material film and the heat resistant layer are dried at the first temperature that is a high temperature. Accordingly, migration of the heat resistant layer is promoted, so that the binder gathers in the surface layer of the heat resistant layer
Implementation Method 2
The drying of the active material film and the heat resistant layer includes a first step and a second step performed subsequently to the first step. A drying temperature to be used in the first step is set to a first temperature. A drying temperature to be used in the second step is set to a second temperature lower than the first temperature
Data Source
AI summary
A manufacturing method of a negative electrode includes: forming, on a belt-shaped copper foil, an active material film formed such that powder including a negative-electrode active material is moisturized and granulated into granulated bodies and the granulated bodies are formed into a film shape; applying a pasty heat resistant layer on the active material film; and drying the active material film and the heat resistant layer. In the applying, an HRL paste including a binder is applied as the heat resistant layer. The drying includes a first drying step, and second and third drying steps subsequent to the first drying step. A preset temperature of a first furnace used in the first drying step is a first temperature, and preset temperatures of a second furnace used in the second drying step and a third furnace used in the third drying step are a second temperature lower than the first temperature.