Carbon-Coated Silicon-Graphite Anode for Stable SEI and Cycle Life
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Solution Overview
Problem
The volume change and electrical contact loss of silicon-based negative electrode materials in lithium-ion batteries due to lithium intercalation and de-alloying processes lead to capacity loss and reduced cycle life, despite nano-sizing and graphite compounding efforts, with the silicon particles losing electrical contact and the SEI film being unstable.
Innovation Solution
A nano-silicon-graphite composite negative electrode material is prepared with a carbon coating and aluminum metaphosphate composite modification layer, enhancing conductivity and stabilizing the SEI film through surface modifications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If nano-silicon is composited with graphite, then capacity retention is improved, but electrical contact loss occurs due to different expansion shrinkage rates
Solution Approach 1:
The patent applies parameter changes by modifying the surface properties of nano-silicon particles through carbon coating and aluminum metaphosphate treatment. This changes the physical and chemical parameters of the particle surface, improving binding strength and electrical contact stability while accommodating volume expansion during lithium intercalation cycles
Solution Approach 2:
The patent creates a composite structure by combining nano-silicon with graphite, and further composites the surface with carbon coating and aluminum metaphosphate. This multi-layer composite approach leverages the advantages of each material: silicon for high capacity, graphite for structural stability, carbon for conductivity, and aluminum metaphosphate for surface stabilization
2Reliability
If surface modification is performed to improve cycle life, then SEI film stability is enhanced, but manufacturing complexity increases
Solution Approach 1:
The patent merges multiple surface modification functions into a unified treatment process. The carbon coating and aluminum metaphosphate modification are applied together in sequence, combining conductivity enhancement, surface stabilization, and SEI film improvement into an integrated manufacturing process that manages complexity through functional integration
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 material exhibits improved binding strength, reduced electrolyte consumption, and enhanced cycle life by stabilizing the SEI film and adapting to volume changes, achieving higher capacity retention.
Implementation Method 1
The presence of the composite modification layer not only has the effects of traditional carbon coating, such as improving the conductivity of the silicon material
Implementation Method 2
The presence of aluminum metaphosphate may help to form a stable SEI film on the surface of the material
Data Source
AI summary
A nano-silicon-graphite composite negative electrode material with carbon coating and aluminum metaphosphate composite modification layer on surface and its preparation method are disclosed, which is mainly prepared from following components by mass percentage: 4-10 wt. % of aluminum metaphosphate, 10 wt. % of asphalt cracking carbon, 15 wt. % of spherical nano-silicon powder, and 71-65 wt. % of graphite powder. A nano-silicon powder is added to deionized water for ultrasonic dispersion to obtain a uniform dispersion, then graphite powder is added to mix uniformly, and then waterborne asphalt is added. After stirring and mixing evenly, spray drying is carried out, and the dried powder is compounded with metaphosphate for mechanical fusion. Finally, the same is transferred into vacuum furnace for high-temperature carbonization to obtain the product. The composite modification layer existing on the surface can well inhibit the corrosion of the nano-silicon material by electrolytes, alleviate volume expansion, improve electrical conductivity, and increase cycle life.