Dual-Layer Negative Electrode Structure for Battery Electrolyte Permeability
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Solution Overview
Problem
Non-aqueous electrolyte secondary batteries with increased packing density of negative electrode mixture layers experience reduced capacity due to decreased permeability of the electrolyte, as solely improving wettability does not sufficiently address the issue of electrolyte penetration.
Innovation Solution
A non-aqueous electrolyte secondary battery design featuring a negative electrode with a dual-layer structure, where the second layer has higher porosity and a lower content of highly dielectric material compared to the first layer, enhancing electrolyte permeability and maintaining battery capacity during charging and discharging cycles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the packing density of the negative electrode mixture layer is increased to increase battery capacity, then the energy density is improved, but the permeability of the non-aqueous electrolyte to the negative electrode mixture layer is degraded, resulting in reduced battery capacity with repetition of charging and discharging
Solution Approach 1:
The negative electrode mixture layer is divided into two distinct layers: a first negative electrode mixture layer with higher highly dielectric material content and lower porosity for high capacity, and a second negative electrode mixture layer with lower highly dielectric material content and higher porosity for electrolyte permeability. This segmentation allows each layer to fulfill different functional requirements simultaneously.
Solution Approach 2:
Different regions of the negative electrode mixture layer are assigned different properties: the first layer (closer to current collector) has higher highly dielectric material content (1-10 mass%) for capacity, while the second layer (outer layer) has lower highly dielectric material content (0.1-5 mass%) and higher porosity for electrolyte access. This local differentiation resolves the contradiction between capacity and permeability.
2Reliability
If the content of highly dielectric material in the negative electrode mixture layer is increased to improve wettability, then the surface wettability is improved, but the porosity between graphite particles is reduced, limiting deep electrolyte penetration
Solution Approach 1:
The highly dielectric material content is varied locally across the electrode structure. The first layer contains 1-10 mass% highly dielectric material to ensure good wettability and electrical contact, while the second layer contains 0.1-5 mass% to maintain higher porosity for deep electrolyte penetration. This gradient structure resolves the contradiction between surface wettability and internal permeability.
Solution Approach 2:
The electrode mixture layer is segmented into two layers with different highly dielectric material concentrations. The first layer provides the wettability function, while the second layer provides the permeability function, allowing both requirements to be satisfied without compromise.
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 design improves the charge/discharge cycle characteristics of the battery by maintaining capacity through increased electrolyte permeability and adjusted porosity, reducing capacity reduction over repeated cycles.
Implementation Method 1
a porosity between the graphite particles in the second negative electrode mixture layer is higher than a porosity between the graphite particles in the first negative electrode mixture layer
Implementation Method 2
the negative electrode layer includes graphite particles and a highly dielectric material having a higher dielectric constant than the graphite particles
Data Source
AI summary
A non-aqueous electrolyte secondary battery provided with a positive electrode, a negative electrode, and a non-aqueous electrolyte. The negative electrode includes a negative electrode current collector and a negative electrode mixture layer formed on the surface of the negative electrode current collector. The negative electrode mixture layer includes a first negative electrode mixture layer opposite to the negative electrode current collector, and a second negative electrode mixture layer laminated on the surface of the first negative electrode mixture layer. The negative electrode mixture layer includes graphite particles and a highly dielectric material having a higher dielectric constant than the graphite particles. The porosity between the graphite particles in the second negative electrode mixture layer is greater than in the first negative electrode mixture layer. The content proportion of the highly dielectric material in the first negative electrode mixture layer is greater than in the second negative electrode mixture layer.