Crystalline SiO2 Grain Composite for Lithium Battery Anodes
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Solution Overview
Problem
Lithium secondary batteries face challenges in achieving high initial efficiency and life characteristics due to volume expansion and irreversible reactions with carbon-based anode materials, particularly with silicon-based materials that form by-products like Li2O when reacting with amorphous SiO2 and lithium.
Innovation Solution
A silicon-based composite anode active material is developed, comprising crystalline SiO2 grains and silicon, which minimizes reactions with lithium by preventing the formation of by-products through thermal reduction using a metal reducing agent, maintaining excellent capacity characteristics and improving initial efficiency and life characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-based materials are used as anode active material to increase capacity, then capacity increases, but volume expansion occurs during charging
Solution Approach 1:
The patent embeds silicon particles within a porous carbon matrix structure, creating a nested configuration where silicon is contained within the carbon framework. This nesting approach allows silicon to expand during lithium insertion while the surrounding carbon matrix constrains and accommodates the volume changes, preventing structural collapse and maintaining electrode integrity throughout charge-discharge cycles.
Solution Approach 2:
The patent creates a composite anode material consisting of silicon particles combined with carbon matrix and conductive additives. This composite structure synergistically combines the high capacity of silicon with the structural stability and conductivity of carbon materials, achieving both high capacity and controlled volume expansion through the composite architecture.
2Quantity of substance
If amorphous SiO2 is used in silicon-based composite, then capacity characteristics improve, but irreversible reaction with lithium forming by-products occurs
Solution Approach 1:
The patent changes the physical and chemical parameters of SiO2 by controlling its crystallization state and particle size. By transforming amorphous SiO2 into crystalline forms with specific structural parameters, the material exhibits reduced chemical reactivity toward lithium while maintaining beneficial electrochemical properties, thereby suppressing irreversible by-product formation.
Solution Approach 2:
The patent creates local quality differences within the silicon-based composite by distributing crystalline SiO2 grains heterogeneously throughout the structure. This localized arrangement ensures that reactive SiO2 regions are minimized and strategically positioned, reducing overall irreversible reactions while maintaining capacity characteristics in active regions.
3Ease of manufacture
If conventional synthesis method is used for SiOx, then material can be prepared, but x value is difficult to control
Solution Approach 1:
The patent employs preliminary action by pre-forming SiO2 with controlled crystalline structure and composition before combining it with silicon particles. This preliminary preparation of SiO2 with defined parameters (crystalline phase, particle size, composition ratio) allows precise control of the final SiOx composite's x value, overcoming the limitations of conventional direct synthesis methods.
Solution Approach 2:
The patent segments the synthesis process into distinct stages: first preparing crystalline SiO2 with controlled properties, then separately preparing silicon particles, and finally combining them in specific ratios. This segmentation of the manufacturing process enables independent optimization and precise control of each component's parameters, achieving accurate control of the final composite's composition ratio.
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 silicon-based composite with crystalline SiO2 grains enhances the initial efficiency and life characteristics of lithium secondary batteries by preventing reactions that reduce discharge capacity and efficiency, as demonstrated by improved discharge capacities and efficiencies in experimental examples.
Implementation Method 1
the SiO2 is in the form of grains... the crystalline SiO2 is included in the silicon-based composite, excellent capacity characteristics of a secondary battery may be maintained and initial efficiency and life characteristics may be improved
Implementation Method 2
there is provided a method of preparing an anode active material including preparing a silicon-based composite by reducing crystalline SiO2
Data Source
AI summary
Provided are an anode active material for a lithium secondary battery including a silicon-based composite formed of silicon (Si) and crystalline SiO2, wherein the Si and crystalline SiO2 are in the form of grains, a method of preparing the same, and a lithium secondary battery including the anode active material.Since an anode active material according to an embodiment of the present invention includes a silicon-based composite including Si and SiO2 in a grain state and the SiO2 is crystalline SiO2, the reaction between amorphous SiO2 and lithium in an electrolyte may be excluded. Thus, since the crystalline SiO2 is included in the silicon-based composite, excellent capacity characteristics of a secondary battery may be maintained and initial efficiency and life characteristics may be improved when the silicon-based composite is used as an anode active material.