Amorphous Carbon Negative Electrode for High Capacity Li-Ion Batteries
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Solution Overview
Problem
Lithium ion secondary batteries face capacity reduction issues due to the use of electrical conducting materials in the negative electrode, which compromise the active material ratio and lead to adverse effects on battery performance.
Innovation Solution
Employing an amorphous carbon material with specific particle size distribution and no electrical conducting material in the negative electrode, ensuring high active material ratio and maintaining electrical conductivity without the need for additional conductive components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If electrical conducting material is added to the negative electrode to ensure electrical conductivity, then electrical conductivity is improved, but the ratio of active material decreases leading to lower negative electrode capacity
Solution Approach 1:
The amorphous carbon material serves dual functions: as the active material for lithium ion insertion/extraction and as the electrical conducting material. By making the active material itself conductive through its amorphous structure, the need for separate conducting additives is eliminated, thus maintaining 100% active material ratio while ensuring adequate electrical conductivity.
Solution Approach 2:
The amorphous carbon material performs multiple functions simultaneously: it acts as the electrode active material, the electrical conducting material, and the structural matrix. This multi-functionality resolves the contradiction by eliminating the need for separate conducting material components that would otherwise dilute the active material content.
2Reliability
If vapor-grown carbon fibers are used as combined active material and electrical conducting material, then charge/discharge cycle performance is improved, but high mixing ratio (5-30%) is required which risks electrolyte breakdown due to graphite reactivity
Solution Approach 1:
The invention changes the structural parameter of the carbon material from crystalline/graphitic to amorphous. This parameter change fundamentally alters the chemical reactivity profile, eliminating the strong reactivity between graphite and electrolyte that causes breakdown, while simultaneously providing adequate electrical conductivity at much lower concentrations (0.1-10 wt%).
Solution Approach 2:
The amorphous carbon material provides sufficient electrical conductivity at low concentrations (0.1-10 wt%), avoiding the need for high concentrations of reactive graphite materials. This reduces the risk of electrolyte breakdown while maintaining cycle performance.
3Power
If fine carbon particles are used to improve electrical conductivity, then electrical conductivity is enhanced, but the particle size distribution may lead to increased reactivity with electrolyte and reduced stability
Solution Approach 1:
The invention changes the structural parameter from crystalline to amorphous carbon, which fundamentally reduces electrolyte reactivity. The amorphous structure provides sufficient conductivity without requiring fine particle sizes that would increase surface area and reactivity. The particle size is controlled at 7-20 μm with specific distribution to balance conductivity and stability.
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
This approach enhances the battery's capacity and reliability by maintaining a high active material ratio, reducing reactivity with the electrolyte, and preventing solvent breakdown, thereby extending the battery's service life and improving cycle performance.
Implementation Method 1
a negative electrode uses an amorphous carbon material as a negative electrode active material... wherein said amorphous carbon material has (A) the average particle diameter (median size) of 7 μm to 20 μm inclusive as measured by a laser diffraction scattering method
Implementation Method 2
the average particle diameter (median size) of 7 μm to 20 μm inclusive as measured by a laser diffraction scattering method
Data Source
AI summary
The invention provides a lithium ion secondary battery comprising a positive electrode, a negative electrode and an electrolysis solution containing an aprotic solvent having an electrolyte dissolved in it, wherein the negative electrodes uses an amorphous carbon material as a negative electrode active material. The amorphous carbon material has (A) an average particle diameter (median size) of 7 μm to 20 μm inclusive as measured by a laser diffraction scattering method and (B) a particle size distribution as measured by a laser diffraction scattering method, in which distribution the ratio of particles of less than 3 μm in diameter is 1% by mass to 10% mass inclusive, and is free of an electrical conducting material.