Silicon Anode Layer and Electrolyte for Stable Fast-Charge Cycling
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Solution Overview
Problem
Secondary batteries using silicon-based particles face significant increases in resistivity due to volume changes during high-temperature intermittent cycles and fast-charge cycles, leading to disconnection in the conductive network and reduced cycling performance.
Innovation Solution
A secondary battery design with controlled thickness and particle size of the negative electrode mixture layer, combined with a specific electrolyte containing dinitrile and trinitrile compounds, forms a solid electrolyte interface film that adsorbs carbon nanotubes, maintaining a stable conductive network despite volume changes.
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 cycling performance deteriorates due to significant shrinkage and expansion during metal ion intercalation and deintercalation
Solution Approach 1:
The negative electrode mixture layer is divided into multiple layers along the thickness direction, with each layer containing silicon-based particles of different particle sizes. This segmentation allows smaller particles to fill voids between larger particles, optimizing space utilization and energy density while reducing overall volume change impact on the conductive network.
Solution Approach 2:
Different regions of the negative electrode mixture layer have different particle size distributions. The layer is designed with a gradient structure where particle sizes vary through the thickness, creating local variations in mechanical properties and ion transport characteristics that accommodate silicon expansion and contraction while maintaining overall structural integrity and conductive network stability.
2Quantity of substance
If the negative electrode mixture layer thickness is increased to accommodate more silicon-based particles, then the energy density is improved, but the resistance increase rate during high-temperature intermittent cycles and fast-charge cycles increases due to conductive network disconnection
Solution Approach 1:
The thick negative electrode mixture layer is segmented into multiple sub-layers with different particle size compositions. This segmentation creates multiple internal conductive pathways through the thickness direction, ensuring that if one pathway is disrupted by silicon volume changes, alternative pathways remain open to maintain electrical conductivity and reduce resistance increase.
Solution Approach 2:
The negative electrode mixture layer is designed as a composite structure combining silicon-based particles of different sizes with carbon materials and conductive agents. This composite structure creates a robust three-dimensional conductive network that can accommodate silicon expansion and contraction while maintaining electrical connectivity, thereby reducing the resistance increase rate during high-temperature intermittent cycles and fast-charge cycles.
3Quantity of substance
If silicon-based particles undergo volume expansion and shrinkage during cycling, then the energy storage capacity is improved, but the carbon nanotubes disconnect from the conductive network path, causing resistivity increase
Solution Approach 1:
The negative electrode is segmented into multiple layers with different particle size distributions, creating a gradient structure that accommodates silicon volume changes. This segmentation ensures that carbon nanotubes in different layers experience different mechanical stresses, preventing simultaneous disconnection across the entire conductive network and maintaining stable electrical conductivity during cycling.
Solution Approach 2:
The particle size parameter is varied through the thickness of the negative electrode mixture layer, creating a gradient structure. This parameter change allows the conductive network to adapt to silicon volume changes at different locations, with smaller particles in certain regions providing better mechanical coupling and maintaining carbon nanotube connectivity despite local expansion and contraction.
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 with reduced high-temperature intermittent cycle resistance increase rate and fast-charge cycle resistance increase rate, 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
When the dinitrile compound and trinitrile compound containing the cyano groups participate in the generation of a solid electrolyte interface film (SEI film) on the surfaces of the silicon-based particles
Data Source
AI summary
A secondary battery includes a negative electrode, a positive electrode, and an electrolyte, where 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.