Artificial Graphite Core with Amorphous Carbon Coating for Battery Stability
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Solution Overview
Problem
Secondary batteries face challenges in achieving high energy density while maintaining fast charging capability and cycle life, as high energy density often compromises these performance metrics.
Innovation Solution
A negative electrode active material is developed with a core of artificial graphite and a coating layer of amorphous carbon, where the surface area average particle size ratio before and after compaction under pressure satisfies a specific range, enhancing structural stability and fast active ion transport.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the energy density of a battery is increased, then the endurance of the secondary battery is improved, but the fast charging capability and cycle life deteriorate
Solution Approach 1:
The patent uses a composite material structure consisting of artificial graphite core particles coated with amorphous carbon. This composite structure combines the high capacity benefits of crystalline graphite with the fast ion transport and structural stability of amorphous carbon, resolving the contradiction between energy density and fast charging capability while maintaining cycle life
Solution Approach 2:
The patent changes the structural parameters of the negative electrode active material by controlling the particle size ratio (Dv50 of coated particles/Dv50 of core particles within 0.95-1.05) and the coating thickness (5-50 nm). These parameter optimizations enable simultaneous achievement of high energy density, fast charging capability, and extended cycle life
2Quantity of substance
If the gram capacity of the negative electrode active material is increased, then the energy density is improved, but the structural stability under pressure deteriorates
Solution Approach 1:
The amorphous carbon coating layer provides structural stability under pressure while the artificial graphite core maintains high gram capacity. The composite structure prevents particle fragmentation and maintains integrity during cyclic expansion and contraction, resolving the contradiction between capacity and stability
Solution Approach 2:
The patent applies different material properties to different parts of the active material: the interior maintains high-capacity crystalline graphite structure while the surface is covered with stress-resistant amorphous carbon. This local differentiation allows the material to simultaneously achieve high gram capacity and structural stability under pressure
Data Source
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AI summary
The present application discloses a negative electrode active material and a method for preparation thereof, a secondary battery, and an apparatus including the secondary battery. The negative electrode active material includes a core and a coating layer covering a surface of the core, the core includes artificial graphite, the coating layer includes amorphous carbon, the negative electrode active material has a surface area average particle size D(3,2) denoted as A, the negative electrode active material has a surface area average particle size D(3,2) denoted as B after powder compaction under a pressure of 20 kN, and the negative electrode active material satisfies: 72% ≤ B/A × 100% ≤ 82%.