Electrolyte with Fluorine Ions for Silicon Anode Cycle Life
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Solution Overview
Problem
Current battery technologies using carbonaceous materials as anode active materials face limitations in achieving high energy density and long cycle life due to lithium dendrite formation, capacity constraints, and material instability, particularly when using lithium alloys that expand and shrink during charge and discharge.
Innovation Solution
An electrolytic solution containing 4-fluoro-1,3-dioxolane-2-one with a fluorine ion content ranging from 14 weight ppm to 1290 weight ppm is used, which improves chemical stability and enhances battery characteristics such as cycle life, especially when paired with anode active materials like tin and silicon, and complex oxides containing lithium and nickel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If lithium alloys are used as anode active materials to achieve higher capacity, then anode capacity is improved, but cycle characteristics are deteriorated due to expansion and shrinkage during charge and discharge
Solution Approach 1:
The patent introduces an intermediary substance (electrolyte solution containing specific additives like fluoroethylene carbonate and vinylene carbonate) that mediates between the lithium alloy anode and the electrolyte. This intermediary forms a stable solid electrolyte interface (SEI) layer that prevents direct contact between the reactive lithium alloy and the electrolyte, thereby reducing expansion-shrinkage stress and improving cycle characteristics while maintaining high capacity
Solution Approach 2:
The patent changes the chemical composition parameters of the electrolyte solution by introducing specific additives (fluoroethylene carbonate at 5-20 wt% and vinylene carbonate at 2-10 wt%) to modify the properties of the SEI layer formed on the lithium alloy anode. This parameter change in electrolyte composition leads to a more stable SEI layer that accommodates volume changes during charge-discharge cycles, thus improving cycle characteristics
2Stability of the object's composition
If substitution is made with elements not involved in expansion and shrinkage to inhibit pulverization, then structural stability is improved, but capacity is reduced
Solution Approach 1:
The patent uses composite materials by combining lithium alloy particles (providing high capacity) with carbonaceous materials (providing structural stability). The carbon matrix acts as a buffer that accommodates expansion-shrinkage stress while maintaining electrical conductivity and structural integrity, thus achieving both high capacity and structural stability simultaneously
3Reliability
If graphite material or carbonaceous material is used for anode to achieve long cycle life, then cycle life is improved, but energy density is limited due to upper limit of intercalation capacity
Solution Approach 1:
The patent merges two different anode materials (lithium alloy and carbonaceous material) into a composite structure. The lithium alloy provides high capacity while the carbonaceous material provides long cycle life and structural stability. This combination allows the battery to achieve both high energy density and long cycle life by leveraging the complementary advantages of each material
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 electrolytic solution effectively inhibits decomposition reactions, reduces internal resistance, and improves capacity retention and cycle characteristics, particularly when used with anode materials containing tin or silicon, and further enhances performance when the cathode contains lithium-nickel complex oxides.
Implementation Method 1
the fluorine ion content in the electrolytic solution is in the range from 14 weight ppm to 1290 weight ppm, thereby chemical stability can be improved
Implementation Method 2
an electrolytic solution containing 4-fluoro-1,3-dioxolane-2-one, in which fluorine ion content is in the range from 14 weight ppm to 1290 weight ppm
Data Source
AI summary
A battery capable of improving battery characteristics such as cycle characteristics is provided. An electrolytic solution is impregnated in a separator. The electrolytic solution contains 4-fluoro-1,3-dioxolane-2-one. Fluorine ion content in the electrolytic solution is preferably from 10 weight ppm to 3200 weight ppm. Thereby, chemical stability of the electrolytic solution is improved, and cycle characteristics are improved. The present invention is effective for the case using an anode active material containing Sn or Si as an element for an anode.