Silicon Anode Secondary Battery Electrolyte for Cycle Resistance Control
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Solution Overview
Problem
Secondary batteries using silicon-based particles face significant challenges with high-temperature intermittent cycle and fast-charge cycle resistance increase due to volume changes causing disconnection in the conductive network path, leading to reduced cycling performance.
Innovation Solution
A secondary battery design incorporating carbon nanotubes and a specific electrolyte composition with dinitrile and trinitrile compounds, optimized thickness and particle size ratios, and controlled electrolyte mass percentages to stabilize the conductive network and reduce resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-based particles are used to increase energy density, then the energy density of the secondary battery is significantly improved, but the high-temperature intermittent cycle resistance increase rate and fast-charge cycle resistance increase rate worsen due to volume expansion and shrinkage causing disconnection in the conductive network path
Solution Approach 1:
The negative electrode mixture layer is segmented into multiple layers with different thicknesses. The first negative electrode mixture layer has a thickness of 3.7≤10T/D2≤24.9 μm and contains silicon-based particles and carbon nanotubes, while the second negative electrode mixture layer has a thickness of 0.1≤10T/D2≤3.6 μm and contains only carbon nanotubes. This segmentation allows the thicker first layer to provide high energy density while the thinner second layer maintains conductive network connectivity during volume changes.
Solution Approach 2:
Different regions of the negative electrode mixture layer have different compositions and thicknesses to fulfill different functions. The first layer (thicker) is optimized for energy density with silicon-based particles, while the second layer (thinner) is optimized for conductivity maintenance with only carbon nanotubes. This local quality differentiation resolves the contradiction between energy density and cycling performance.
Solution Approach 3:
The negative electrode uses a composite structure combining silicon-based particles (for high capacity) with carbon nanotubes (for conductivity and structural stability). The dual-layer composite design allows the silicon-based particles to expand and shrink while the carbon nanotube network in both layers maintains electrical connectivity, preventing disconnection during cycling.
2Quantity of substance
If the negative electrode mixture layer thickness is increased to improve energy density, then the energy density improves, but the conductive network path becomes more prone to disconnection during silicon particle expansion, increasing resistance
Solution Approach 1:
The negative electrode mixture layer is divided into two segments: a first layer with thickness 3.7≤10T/D2≤24.9 μm containing silicon-based particles and carbon nanotubes, and a second layer with thickness 0.1≤10T/D2≤3.6 μm containing only carbon nanotubes. This segmentation allows the thicker first layer to provide high energy density while the thinner second layer acts as a protective conductive buffer that prevents complete network disconnection during expansion.
Solution Approach 2:
The second negative electrode mixture layer containing only carbon nanotubes is applied in advance as a protective layer. This preliminary conductive network structure is designed to accommodate and buffer the volume expansion of silicon-based particles before it can disrupt the main conductive pathways, preventing resistance increase.
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 design achieves high energy density while significantly reducing high-temperature intermittent cycle and fast-charge cycle resistance increase rates, enhancing the battery's cycling performance.
Implementation Method 1
the generated solid electrolyte interface film has a special adsorption capability of adsorbing the carbon nanotubes
Implementation Method 2
leading to a disconnection in a conductive network path in the negative electrode mixture layer and an increase in resistivity
Implementation Method 3
the silicon material undergoes significant shrinkage and expansion with the intercalation and deintercalation of metal ions
Data Source
AI summary
A secondary battery includes a negative electrode, a positive electrode, and an electrolyte, wherein the negative electrode includes a negative electrode current collector and a negative electrode mixture layer disposed on at least one surface of the negative electrode current collector. A thickness of the negative electrode mixture layer is T μm, the negative electrode mixture layer contains carbon nanotubes and silicon-based particles, an average particle size of the silicon-based particles is D μm, and 3.7 ≤10T/D2≤24.9. The electrolyte includes a dinitrile compound and a trinitrile compound.