Secondary Battery Electrode with Concave Surface for Ion Diffusion
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Solution Overview
Problem
Secondary batteries used as high-output power supplies for vehicles face challenges in reducing ion diffusion resistance on the electrode active material layer, leading to increased capacity loss and complexity in manufacturing due to uneven surface structures and high costs associated with creating concave/convex structures.
Innovation Solution
An electrode for secondary batteries is designed with a concave part on the surface of the electrode active material layer, where the layer is uniformly divided into three layers with specific density relationships and porosity within a controlled range, utilizing hollow active material particles to maintain voids and reduce ion diffusion resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the surface of the electrode active material layer is made uneven by laser after coating film is dried, then the surface area is increased, but the ion diffusion resistance increases and capacity loss occurs
Solution Approach 1:
The concave part is formed on the surface of the electrode active material layer before battery assembly, during the electrode manufacturing process. This preliminary action allows the uneven surface structure to be established while maintaining uniform electrode density, avoiding subsequent laser processing that would increase ion diffusion resistance and cause capacity loss.
Solution Approach 2:
The surface of the electrode active material layer is made uneven only in specific local regions (concave parts) while maintaining uniform density throughout the layer. This localized surface modification increases surface area for charge transfer reactions without creating the harmful effects of laser processing across the entire surface.
2Area of stationary object
If a concave/convex structure is created by gradual deposition of electrode material, then the surface area is increased, but the manufacturing steps become complicated and cost increases
Solution Approach 1:
The concave part is formed during the initial coating process by controlling the slurry application and drying conditions, rather than requiring subsequent gradual deposition steps. This approach creates the desired uneven surface structure in a single manufacturing step, simplifying the overall process and reducing costs.
Solution Approach 2:
The concave part is formed by controlling parameters during the coating and drying process, such as slurry viscosity, drying rate, and coating thickness distribution. By adjusting these parameters, the uneven surface structure is achieved during normal manufacturing without requiring complex additional deposition steps.
3Quantity of substance
If the electrode active material layer is made denser to improve energy density, then the capacity increases, but the ion diffusion resistance increases
Solution Approach 1:
The electrode active material layer maintains uniform density in the thickness direction (avoiding local densification that would block ion diffusion), while the concave parts on the surface provide increased surface area. This local surface modification allows high energy density without increasing ion diffusion resistance, as the bulk density remains uniform and optimized.
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 solution effectively reduces ion diffusion resistance while maintaining energy density and improving durability, with the concave part configuration allowing for a more efficient charge transfer reaction, thus enhancing the battery's input and output characteristics.
Implementation Method 1
utilizing hollow active material particles to maintain voids and reduce ion diffusion resistance
Implementation Method 2
A concave part is formed on the surface of the electrode active material layer... an area in which a charge transfer reaction occurs is larger
Data Source
AI summary
An electrode of a secondary battery includes an electrode active material layer containing active material particles. A concave part is formed on the surface of the electrode active material layer. When the electrode active material layer is uniformly divided into three layers, an upper layer, an intermediate layer and a lower layer, in the thickness direction from the surface of the concave part to the electrode current collector, and the electrode densities (g/cm3) of the upper layer, the intermediate layer, and the lower layer are d1, d2, and d3, respectively, they have a relationship of 0.8<(d1/d3)<1.1. The porosity of the electrode active material layer is 10% or more and 50% or less. The area ratio of the concave part is 2% or more and 40% or less. The volume ratio of the concave part is 5% or more and 14% or less.