Graphite Core-Shell Negative Electrode Active Material
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Solution Overview
Problem
Lithium secondary batteries face reduced charge and discharge capacities over cycles due to high diffusion resistance of lithium ions and increased electrolyte solution consumption, particularly with the use of natural graphite as the negative electrode active material.
Innovation Solution
A negative electrode active material is developed with a core of artificial graphite and hard carbon, surrounded by a shell of natural graphite, which is stacked and headed to completely cover the core, preventing exposure to the electrolyte solution and reducing diffusion resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If natural graphite is used as the negative electrode active material, then the battery structure is simple and manufacturing is easy, but the diffusion resistance of lithium ions is high and charge-discharge capacity is reduced
Solution Approach 1:
The patent uses a composite material structure consisting of natural graphite particles coated with amorphous or semicrystalline carbon. The core natural graphite provides ease of manufacture and structural stability, while the carbon coating layer reduces lithium ion diffusion resistance. This composite approach resolves the contradiction by combining materials with complementary properties.
2Reliability
If amorphous carbon is added to fill gaps in natural graphite particles, then diffusion resistance is reduced, but electrolyte solution consumption increases
Solution Approach 1:
The patent applies local quality by selectively coating only the surface of natural graphite particles with amorphous or semicrystalline carbon. This localized modification reduces lithium ion diffusion resistance at the critical interface between the active material and electrolyte, while minimizing the total amount of amorphous carbon used. The coating thickness and coverage are controlled to prevent excessive electrolyte consumption while maintaining low diffusion resistance.
3Productivity
If natural graphite particles are spheronized to improve morphology, then charge-discharge capacity is improved, but gaps appear on the surface exposing amorphous carbon to electrolyte solution
Solution Approach 1:
The patent applies preliminary action by coating the natural graphite particles with amorphous or semicrystalline carbon BEFORE the spheronization process. This pre-coating ensures that the carbon layer is already in place to fill gaps and prevent electrolyte contact before the mechanical spheronization process creates surface gaps. The coating is applied in advance to anticipate and prevent the problem of exposed amorphous carbon during subsequent processing.
Solution Approach 2:
The patent uses a thin film of amorphous or semicrystalline carbon as a flexible coating layer on the natural graphite particles. This thin film is flexible enough to accommodate the structural changes during spheronization while maintaining continuous coverage. The film structure allows the particle to be spheronized into improved morphology without exposing the underlying amorphous carbon to the electrolyte solution, thus resolving the contradiction between improved charge-discharge capacity and reduced electrolyte consumption.
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 configuration enhances initial efficiency and life characteristics by minimizing electrolyte solution consumption and lowering lithium ion diffusion resistance, resulting in higher output characteristics for the battery.
Implementation Method 1
a shell surrounding the core and including natural graphite, wherein the shell is formed to cover a surface of the core by stacking and heading the natural graphite
Implementation Method 2
charge and discharge of the lithium secondary battery is performed while a process of intercalating and deintercalating lithium ions from a positive electrode into and out of a negative electrode is repeated
Data Source
AI summary
The present invention relates to a negative electrode active material and a method of preparing the same, the negative electrode active material which includes a core including artificial graphite and hard carbon, and a shell surrounding the core and including natural graphite, wherein the shell is shell is formed to cover a surface of the core by stacking and heading the natural graphite. Since the natural graphite completely surrounds the artificial graphite and the hard carbon, the hard carbon having a low initial efficiency and high electrolyte solution consumption is not exposed to the outside, and thus, high initial efficiency and life characteristics may be obtained. Also, since the natural graphite, the artificial graphite, and the hard carbon are all used, diffusion resistance of lithium ions is lower than that of a case where the natural graphite is only used, and thus, high output characteristics may be achieved.