Graphite Negative Electrode Coating for Low-Gas Secondary Batteries
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Solution Overview
Problem
Existing secondary batteries using natural graphite face issues with low electrode adhesion, excessive gas generation, and degraded high-temperature storage and life characteristics due to side reactions and volume expansion, while artificial graphite offers improved adhesion but high cost and limited capacity.
Innovation Solution
A negative electrode comprising carbon-based active material particles with a specific surface area of 1.4 to 2.3 m2/g and carbon nanotubes with an average length of 1 to 12 μm are used, along with an amorphous carbon-based material coating on natural graphite to enhance adhesion, reduce side reactions, and maintain a conductive network.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If natural graphite is used as negative electrode active material, then electrode adhesion and battery capacity are improved, but side reactions with electrolyte occur excessively causing gas generation and volume expansion
Solution Approach 1:
The patent applies local quality by coating only the surface of natural graphite particles with amorphous carbon, rather than changing the entire structure. This surface coating specifically addresses the harmful side reactions and gas generation issues while preserving the bulk natural graphite's excellent adhesion and capacity properties. The coating layer acts as a localized protective barrier where it is most needed.
Solution Approach 2:
The patent creates a composite material structure by combining natural graphite particles with an amorphous carbon coating layer. This composite approach allows the inner natural graphite to provide adhesion and capacity while the outer amorphous carbon layer suppresses side reactions and gas generation. The composite structure synergistically combines the advantages of both materials.
2Quantity of substance
If natural graphite is used as negative electrode active material, then battery capacity is increased, but volume expansion occurs excessively during charge and discharge
Solution Approach 1:
The amorphous carbon coating is applied locally on the surface of natural graphite particles to specifically address volume expansion issues during charge-discharge cycles. The coating layer accommodates and suppresses the expansion forces while allowing lithium intercalation, thereby maintaining high capacity without excessive volume increase.
Solution Approach 2:
The amorphous carbon coating acts as a pre-applied protective layer that cushions against volume expansion before it occurs during battery operation. This beforehand cushioning prevents the natural graphite from expanding excessively during lithium insertion, maintaining structural integrity and capacity.
3Duration of action of stationary object
If amorphous carbon coating layer is disposed on natural graphite, then life characteristics and high-temperature storage characteristics are improved, but charge/discharge capacity cannot be maintained at high level
Solution Approach 1:
The patent optimizes the coating thickness and composition locally on the graphite surface to balance protection and capacity. The amorphous carbon layer is applied in controlled amounts specifically where needed for protection, rather than thick coatings that would block lithium transport. This localized approach maintains capacity while improving longevity.
Solution Approach 2:
The patent adjusts key parameters including the thickness of the amorphous carbon coating, the heating temperature for coating formation, and the ratio of amorphous carbon to natural graphite. By optimizing these parameters, the coating provides sufficient protection for improved life characteristics while remaining thin enough to allow high charge/discharge capacity.
4Reliability
If artificial graphite is used as negative electrode active material, then electrode adhesion and high-temperature storage characteristics are improved, but cost increases and battery capacity is reduced
Solution Approach 1:
Instead of completely replacing natural graphite with artificial graphite, the patent applies a localized amorphous carbon coating on natural graphite particles. This provides the high-temperature storage characteristics of artificial graphite while retaining the high capacity of natural graphite, avoiding the cost and capacity penalties of full artificial graphite substitution.
Solution Approach 2:
The patent creates a composite negative electrode using natural graphite as the base material with an amorphous carbon coating. This composite structure achieves the high-temperature stability of artificial graphite while maintaining the high capacity characteristics of natural graphite, providing a cost-effective solution with superior performance.
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 solution improves electrode adhesion, reduces volume expansion, and enhances life and high-temperature storage characteristics of the battery by minimizing side reactions and maintaining a stable conductive network.
Implementation Method 1
the conductive agent includes carbon nanotubes having an average length of 1 μm to 12 μm... an excellent conductive network between the carbon-based active material particles and the carbon nanotubes may be maintained
Implementation Method 2
The negative electrode includes a negative electrode active material in which lithium ions released from the positive electrode are intercalated and deintercalated
Data Source
AI summary
Disclosed is a negative electrode including a negative electrode active material layer, wherein the negative electrode active material layer includes a negative electrode active material and a conductive agent. The negative electrode active material includes carbon-based active material particles including natural graphite and an amorphous carbon-based material. The carbon-based active material particles have a specific surface area of 1.4 m2/g to 2.3 m2/g, and the conductive agent includes carbon nanotubes having an average length of 1 μm to 12 μm. A secondary battery including the negative electrode is also disclosed.