Silicon-Composite Anode Powder for Lithium-Ion Batteries
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Solution Overview
Problem
Lithium-ion batteries face performance limitations due to the large volume expansion of silicon-based anode materials during charging, leading to mechanical degradation and the formation of a thick Solid-Electrolyte Interface (SEI) that reduces cycle performance and increases electrical resistance.
Innovation Solution
A composite powder for the anode is developed, where silicon-based domains are embedded in a carbon matrix, with a controlled size distribution and minimal free silicon content, reducing SEI formation and allowing for higher current usage, and relaxing stringent water content requirements in the electrolyte.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-based materials are used as anode active material to achieve high energy density, then theoretical capacity increases to 4200 mAh/g, but large volume expansion of 300% occurs during lithiation leading to mechanical degradation
Solution Approach 1:
The silicon anode material is divided into submicron or nano-sized domains with average size smaller than 500 nm and preferably smaller than 150 nm. This segmentation reduces the overall volume expansion stress and prevents mechanical degradation while maintaining high theoretical capacity.
Solution Approach 2:
Silicon domains are used as composite particles mixed with a matrix material, usually a carbon-based material. This composite structure accommodates the volume change of silicon during lithiation and provides mechanical stability, resolving the contradiction between high capacity and mechanical reliability.
2Reliability
If silicon domains are reduced to submicron or nano-sized to accommodate volume change, then mechanical degradation is reduced, but the complexity of particle size control and composite fabrication increases
Solution Approach 1:
The invention specifies precise parameter ranges for silicon domain size (d50 < 500 nm, preferably d50 < 150 nm) and free silicon content (< 5 wt%, preferably < 2 wt%). By controlling these parameters, the invention achieves improved cycle life while providing clear fabrication guidelines that manage the complexity of particle size control.
3Object-generated harmful factors
If a coating material is applied to active particles to avoid reactions with electrolyte, then SEI formation is reduced, but the manufacturing process complexity and cost increase
Solution Approach 1:
The invention uses a carbon-based matrix material that inherently provides coating functionality. By integrating the coating function into the composite structure itself rather than adding a separate coating step, the invention reduces SEI formation while minimizing process complexity.
Solution Approach 2:
The carbon-based matrix material provides a uniform coating across all silicon domains. This homogeneous structure effectively prevents electrolyte contact with silicon surfaces, reducing SEI formation without requiring complex multi-step coating processes.
4Reliability
If free silicon content is reduced to minimize SEI formation, then cycle performance improves, but the difficulty of achieving uniform distribution and precise control increases
Solution Approach 1:
The invention specifies precise parameter ranges for free silicon content (< 5 wt%, preferably < 2 wt%) and provides clear measurement methods using alkaline solution treatment. This enables manufacturers to achieve improved cycle performance while controlling the precision requirements through well-defined parameters and measurement protocols.
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 composite powder enhances cycle performance, reduces mechanical stress, and lowers the cost of battery production by minimizing the need for expensive processing and raw materials, while maintaining high energy density and power performance.
Implementation Method 1
by alloying or insertion, in the anode's active material
Implementation Method 2
by alloying or insertion, in the anode's active material
Implementation Method 3
An SEI is a complex reaction product of the electrolyte and lithium
Data Source
AI summary
Composite powder for use in an anode of a lithium ion battery, whereby the particles of the composite powder comprise silicon-based domains in a matrix, whereby the individual silicon-based domains are either free silicon-based domains that are not or not completely embedded in the matrix or are fully embedded silicon-based domains that are completely surrounded by the matrix, whereby the percentage of free silicon-based domains is lower than or equal to 4 weight % of the total amount of Si in metallic or oxidized state in the composite powder.