Copolymer-Coated Silicon Anode Material for Stable SEI and Li-Ion Transport
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Solution Overview
Problem
The volume expansion of silicon-based negative electrodes during lithiation leads to rapid rupture of the SEI film and severe side reactions with the electrolyte, limiting the widespread application of silicon-based negative electrodes due to reduced Initial Coulombic Efficiency and safety concerns.
Innovation Solution
A film-coated silicon-based negative electrode active material is developed, featuring a copolymer with 1,3-dioxolane groups and sulfonyl fluoride groups that forms a structurally stable coating, alleviating volume expansion and enhancing lithium ion transport and safety through synergistic effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-based material is used as negative electrode active material, then theoretical specific capacity is improved (4200 mAh/g), but volume expansion during lithiation causes SEI film rupture and reduced Initial Coulombic Efficiency
Solution Approach 1:
A copolymer coating layer is pre-formed on the silicon-based material surface before battery operation. This preliminary coating prevents direct contact between the silicon surface and electrolyte during initial lithiation, avoiding uncontrolled SEI formation and lithium loss, thereby improving Initial Coulombic Efficiency while preserving the high capacity benefit
Solution Approach 2:
The copolymer coating layer acts as a flexible protective film that can accommodate the volume expansion of silicon during lithiation. The film maintains structural integrity without rupturing, continuously protecting the silicon surface from electrolyte contact and preventing ongoing lithium loss, thus maintaining high Initial Coulombic Efficiency
2Quantity of substance
If silicon-based material undergoes volume expansion during lithiation, then lithium ion intercalation is enhanced, but SEI film rupture occurs leading to active lithium loss
Solution Approach 1:
The copolymer coating forms a flexible protective film that accommodates silicon volume expansion during lithiation. The film remains intact and continuous, preventing electrolyte contact with the silicon surface and thereby preventing uncontrolled SEI formation and active lithium loss, while still allowing lithium ion intercalation to proceed
3Strength
If copolymer with 1,3-dioxolane groups and sulfonyl fluoride groups is used for coating, then flexibility and flame retardancy are improved, but manufacturing complexity increases
Solution Approach 1:
The copolymer combines 1,3-dioxolane groups (providing flexibility through ring structure) and sulfonyl fluoride groups (providing flame retardancy through synergistic effect) into a single integrated coating material. This composite approach delivers multiple performance benefits simultaneously while maintaining a relatively simple single-step coating process
Solution Approach 2:
The copolymer's molecular structure is specifically designed with adjustable ratios of 1,3-dioxolane and sulfonyl fluoride groups. By optimizing these compositional parameters, the coating achieves optimal balance between flexibility, flame retardancy, and ease of application, reducing the practical manufacturing complexity despite the sophisticated molecular design
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 film-coated silicon-based material improves cycling and rate performance by mitigating volume expansion, maintaining structural stability, and enhancing safety through improved flexibility and flame retardancy.
Implementation Method 1
The huge volume expansion (up to 400%) of silicon-based negative electrodes during lithiation
Implementation Method 2
the sulfonyl fluoride groups contained in the copolymer are able to form hydrogen bonds with the hydroxyl groups on the surfaces of the silicone-based materials
Implementation Method 3
The 1,3-dioxolane groups and sulfonyl fluoride groups may function synergistically, enabling the copolymer to have a good affinity for the electrolyte. The use of the copolymer as a coating layer provides a good transport channel for lithium ions, facilitates the transport of lithium ions
Implementation Method 4
The fluorine atom in the sulfonyl fluoride groups plays a synergistic flame retardant effect with the sulfuryl groups, which slows down the combustion reaction and improves the safety performance of the battery
Data Source
AI summary
Provided in the present disclosure is a film-coated silicon-based negative electrode active material, including a silicon-based material and a film coated on surfaces of the silicon-based material, in which the film includes a copolymer, and a structure of the copolymer contains 1,3-dioxolane groups and sulfonyl fluoride groups.