Silicon-Anode Battery Electrolyte Ratio for SEI Stability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Lithium-ion batteries face degradation in cycle performance and storage performance due to the volume expansion of silicon in the negative electrode, which damages the SEI film and exposes fresh interfaces, leading to electrolyte consumption and active lithium loss.
Innovation Solution
Incorporating a silicon-containing substance in the negative electrode active material with a specific ratio of fluorinated cyclic carbonate in the electrolyte solution, within the range of 0.1W1≤W2≤0.7W1, to form a protective film on the silicon surface, and using a balanced concentration of LiPF6 and fluorine-containing sulfonimide lithium to reduce HF generation, thereby suppressing interface rupture.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon content in the negative electrode is increased to improve energy density, then gram capacity of the negative electrode is improved, but volume expansion damages the SEI film and consumes electrolyte and active lithium
Solution Approach 1:
The patent optimizes the content ratio of fluorinated cyclic carbonate to silicon-containing substance, specifying that the mass percentage W2 of fluorinated cyclic carbonate should satisfy 0.1W1≤W2≤0.7W1 where W1 is the mass percentage of silicon-containing substance. This parameter optimization ensures sufficient film formation to protect silicon volume expansion while preventing excess additive consumption and oxidation
Solution Approach 2:
The fluorinated cyclic carbonate acts as an intermediary substance that forms a protective film between the silicon-containing substance and the electrolyte solution. This film mediates the interaction by preventing direct contact and harmful reactions while allowing the silicon to expand and contract during charging and discharging cycles
2Reliability
If fluorinated cyclic carbonate content is increased to improve film formation on silicon surface, then interface rupture is suppressed, but excess additive undergoes oxidation and gas production
Solution Approach 1:
The patent precisely controls the concentration parameter of fluorinated cyclic carbonate in the electrolyte solution, requiring that its mass percentage W2 satisfies 0.1W1≤W2≤0.7W1. This optimized parameter range ensures the additive forms sufficient protective film to suppress interface rupture during silicon volume expansion, while preventing excess additive from undergoing oxidation and gas production
3Reliability
If LiPF6 concentration is increased to improve ionic conductivity, then battery performance is improved, but HF generation increases and damages negative electrode interface
Solution Approach 1:
The fluorinated cyclic carbonate acts as a protective intermediary that forms a stable film on the silicon-containing substance surface. This film prevents HF generated from LiPF6 from directly attacking and damaging the negative electrode interface, thus mediating between the need for high ionic conductivity and the need to prevent interface damage
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 solution effectively forms a protective film on the silicon surface, reducing interface rupture and prolonging the cycle and storage life of the battery by enhancing the stability of the metallic lithium negative electrode.
Implementation Method 1
the fluorinated cyclic carbonate can effectively form a film on the surface of the silicon-containing substance
Implementation Method 2
After being intercalated with lithium, silicon has a volume increased to 300% of the original volume
Implementation Method 3
an electrolyte solution continues to undergo a reduction reaction on the interface
Data Source
AI summary
A secondary battery and an electrical device are disclosed, which relate to the field of batteries. The secondary battery includes a negative electrode active material and an electrolyte solution. A mass percentage of a silicon-containing substance in the negative electrode active material is W1%, the electrolyte solution includes fluorinated cyclic carbonate, a mass percentage of the fluorinated cyclic carbonate in the electrolyte solution is W2%, and 0.1W1≤W2≤0.7W1.