Secondary Battery Electrode Coating Grooves for Drying Crack Control
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Solution Overview
Problem
Secondary battery electrodes experience cracks and wrinkles due to drying contraction, leading to decreased performance and foreign substance generation, as the coating film cannot conform to the deformation of the electrode current collector during transport and heating.
Innovation Solution
A method involving the use of a moisture powder with a pendular or funicular state, forming a coating film with a gas phase, and creating grooves in the transport direction on the coating film to improve conformability, minimizing cracks and wrinkles by allowing the film to deform with the current collector.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the coating film is made thicker to increase battery capacity, then the battery capacity increases, but drying contraction increases causing cracks and wrinkles to occur
Solution Approach 1:
The groove is formed on the coating film surface before the drying step. This preliminary action creates a structure that anticipates and accommodates the drying contraction that will occur later, preventing cracks and wrinkles from forming when the thick coating film shrinks during drying
2Productivity
If the drying temperature is increased to shorten drying time, then productivity increases, but cracks and wrinkles reaching the current collector occur
Solution Approach 1:
The groove is formed before drying, preparing the coating film structure in advance to handle the thermal stress and contraction that will occur during high-temperature drying. This allows rapid drying without causing cracks
3Adaptability or versatility
If the coating film is stretched to conform to current collector deformation, then conformability improves, but tensile stress causes cracks in weakly bonded areas
Solution Approach 1:
The groove is formed at the specific location where cracks and wrinkles most frequently occur (the central part in the width direction). This localized modification provides stress relief precisely where needed, allowing the coating film to conform to current collector deformation without causing cracks in weakly bonded areas
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
The method effectively reduces uneven distribution of cracks and wrinkles in the central part of the coating film, enhancing the quality and performance of the electrode by allowing it to conform to the current collector's deformation, thus improving battery durability and capacity.
Implementation Method 1
In such cracks and wrinkles at irregular intervals, a solvent (liquid component) between solid components such as an active material and a binder rapidly evaporates (volatilizes), and thus the solid components pull each other, and tensile stress occurs in the coating film.
Implementation Method 2
when an electrode current collector that is stretched with a certain force is transported in the transport direction, and is heated in a drying step, the current collector can extend in the transport direction and at the same time can contract in the width direction.
Data Source
AI summary
A method of producing an electrode disclosed here includes a step in which a moisture powder formed of agglomerated particles; a step in which by using the moisture powder, a coating film composed of the moisture powder is formed on an electrode current collector, with a gas phase of the coating film being remained so that the average film thickness of the coating film is 50 μm or more; a step in which the coating film on the current collector is transported, concavo-convex transfer is performed using a roll mold, and thus at least one groove extending in the transport direction is formed in a center of a surface part of the coating film, with the groove being formed to have a depth satisfying ( 9/10×t1)>t2; and a step in which the coating film formed on the current collector is dried to form an electrode active material layer.