Silicon-Oxygen Composite Anode Particle Sizing for Cycle Stability
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Solution Overview
Problem
Current lithium-ion batteries with graphite-based anodes have limited energy density and cycle performance due to high expansion rates of silicon-based materials during charging, leading to poor initial Coulombic efficiency and cycle degradation.
Innovation Solution
A silicon-oxygen composite material with a controlled particle size of 3.0 µm to 8.2 µm, comprising a lithium-containing compound and non-metallic silicon-containing material, dispersed with nano-silicon and silicon oxide, and a carbon layer to improve cycle stability and initial Coulombic efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-based anode material is used to increase theoretical capacity, then capacity increases, but expansion rate reaches 300% which affects cycle performance
Solution Approach 1:
The patent embeds silicon particles inside a carbon matrix structure, creating a nested configuration where silicon is contained within carbon. This nesting approach allows silicon to expand and contract during lithium insertion/extraction without compromising the overall structural integrity, thereby maintaining cycle performance while utilizing silicon's high capacity
Solution Approach 2:
The patent creates a composite material system combining silicon, carbon, and oxygen-containing compounds. The composite structure leverages silicon's high capacity, carbon's structural stability and conductivity, and oxygen-containing compounds' ability to form stable SEI films, achieving both high capacity and good cycle performance
2Reliability
If silicon-oxygen material is used to improve cycle performance, then cycle performance improves, but initial Coulombic efficiency decreases due to SEI film formation consuming 20%-50% lithium
Solution Approach 1:
The patent modifies the chemical composition parameters of the oxygen-containing compound, specifically using compounds with controlled lithium content (such as Li2SiO3, Li4SiO4, or Li6Si2O7) to optimize the balance between SEI formation and available lithium for capacity, thereby improving initial Coulombic efficiency while maintaining cycle performance
Solution Approach 2:
The patent creates local regions with different compositions: silicon-rich areas for high capacity, carbon-rich areas for structural stability, and lithium-containing compound regions for controlled SEI formation. This local quality differentiation allows different parts of the composite to perform specialized functions, optimizing both cycle performance and initial efficiency
3Loss of energy
If pre-lithiation is applied to improve initial Coulombic efficiency, then initial efficiency improves, but cycle degradation occurs
Solution Approach 1:
The patent incorporates lithium-containing compounds (such as Li2SiO3, Li4SiO4, or Li6Si2O7) into the composite structure in advance, before battery assembly. These pre-incorporated lithium sources serve as internal lithium reservoirs that can compensate for SEI formation losses during initial cycles without requiring external pre-lithiation treatment, thereby avoiding the cycle degradation associated with conventional pre-lithiation methods
Data Source
AI summary
Providing a silicon-oxygen composite material, an anode material preparation method thereof. The silicon-oxygen composite material has a size D10 of in a range of 3.0 µm to 8.2 µm. In the present disclosure, by controlling the particle size D10 of the silicon-oxygen composite material to between 3.0 µm and 8.2 µm, on the one hand, the uniformity of pre-lithiation can be improved, the nano-silicon cannot be exposed on a surface of the particles, anddesired improvement of initial Coulombic efficiency and good cycle stability can be obtained; on the other hand, the silicon-oxygen composite material has a suitable electron and ion conduction channels, and internal resistance of the particles is small, which improves the rate performance and cycle performance of the material.