Positive Electrode Rolling Control for Battery Integrity
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Solution Overview
Problem
The challenge is to produce a high-capacity lithium secondary battery with improved high-temperature life and storage characteristics without damaging the active material or current collector during the rolling process, which often results in electrode disconnection and capacity deterioration due to excessive packing density and rolling pressure.
Innovation Solution
A method involving the application of a composition for forming a positive electrode on a current collector, followed by controlled rolling to maintain less than 1% elongation of the current collector, achieving a porosity of 25% or less, using a mixture of large and small-diameter particles, and employing nickel, titanium, or stainless steel as the current collector, while ensuring the active material is a lithium transition metal oxide with specific formulations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If excessive rolling is performed to increase packing density, then the capacity of the battery is improved, but the electrode disconnection and crack formation increase, deteriorating high-temperature life characteristics
Solution Approach 1:
The patent changes the rolling pressure parameter to a specific range (3-5 kgf) and limits the number of rolling passes (2 times or less) to optimize the balance between packing density and electrode integrity. This parameter optimization prevents excessive compression that would cause electrode disconnection while achieving sufficient packing density for high capacity.
Solution Approach 2:
The patent applies partial rolling action (2 times or less at controlled pressure) rather than excessive rolling. This partial action is sufficient to achieve the required packing density for high capacity while avoiding the harmful effects of over-rolling such as electrode disconnection and crack formation.
2Quantity of substance
If rolling pressure is increased to achieve high packing density, then the energy density is improved, but the active material and current collector are damaged
Solution Approach 1:
The patent optimizes the rolling pressure parameter to a specific range (3-5 kgf) that is sufficient to achieve high packing density and energy density while remaining below the threshold that would damage the active material or current collector. This precise parameter control resolves the contradiction between density improvement and material integrity.
3Quantity of substance
If the porosity of the positive electrode mixture layer is reduced to increase capacity, then the high-temperature storage characteristics are improved, but the electrode structure becomes more fragile
Solution Approach 1:
The patent reduces porosity to 25% or less through controlled rolling to increase capacity and improve high-temperature storage characteristics. The rolling parameters are carefully selected to achieve this porosity reduction without applying excessive force that would fragment the active material or damage the electrode structure.
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 enhances the packing density of the positive electrode, prevents electrode disconnection, and improves high-temperature life and storage characteristics, maintaining high energy density and capacity retention.
Implementation Method 1
rolling the positive electrode mixture layer such that the elongation of the positive electrode current collector is less than 1%
Data Source
AI summary
The present disclosure relates to a method for producing a positive electrode for a secondary battery, the method including applying a composition for forming a positive electrode on a positive electrode current collector to form a positive electrode mixture layer, and rolling the positive electrode mixture layer such that the elongation of the positive electrode current collector is less than 1%, to produce a positive electrode.