Graphene Composite Negative Electrode for Lithium Battery
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Solution Overview
Problem
Graphene-based negative electrode materials for lithium secondary batteries face challenges such as low initial efficiency and degraded high-temperature storage characteristics due to side reactions with electrolyte solutions and agglomeration issues during the manufacturing process.
Innovation Solution
A composite negative electrode material is developed, featuring a graphene sheet with two or more coating layers, including a polymer and a pitch coating layer, applied in a specific weight ratio to reduce side reactions and enhance conductivity and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If graphene is used as negative electrode material due to its high electrical mobility and favorable structure for lithium ion access, then electrical conductivity and lithium ion accessibility are improved, but side reactions with electrolyte solution increase causing low initial efficiency and degraded high-temperature storage characteristics
Solution Approach 1:
The patent applies composite materials by combining graphene with carbon nanotubes and conductive polymers to create a hybrid negative electrode structure. This composite approach maintains the high electrical conductivity and lithium ion accessibility of graphene while the carbon nanotubes and conductive polymers form a protective network that reduces direct exposure of graphene to electrolyte, thereby decreasing side reactions and improving initial efficiency and high-temperature storage characteristics.
Solution Approach 2:
The patent employs thin film coatings of conductive polymers and amorphous carbon on the graphene surface. These thin protective films act as barriers that prevent direct contact between graphene and electrolyte solution, reducing side reactions. The films are designed to be sufficiently thin to maintain electrical conductivity and lithium ion transport while providing adequate protection against electrolyte decomposition.
2Manufacturing precision
If graphene is prepared by chemical vapor deposition method to achieve high purity and desired size, then purity and size control are improved, but the amount of graphene produced is limited and additional treatment is required
Solution Approach 1:
The patent merges multiple graphene preparation methods by combining chemical vapor deposition (for high purity and size control) with mechanical exfoliation and chemical reduction methods. This hybrid approach allows the production of larger quantities of graphene while maintaining the purity and size characteristics achieved through CVD. The combined methods enable scalable production without sacrificing the quality control benefits of CVD.
3Productivity
If graphene is prepared by physical method to obtain larger amount, then quantity is improved, but it is difficult to secure sufficient amount and achieve unique characteristics of graphene
Solution Approach 1:
The patent applies preliminary action by performing chemical reduction and purification treatments on physically exfoliated graphene before final assembly. This preliminary chemical treatment converts oxidized graphene from mechanical exfoliation into reduced graphene oxide with improved conductivity and characteristics closer to pristine graphene. The preliminary purification steps remove impurities while maintaining the high quantity advantage of physical methods.
4Reliability
If coating layers are added to reduce side reactions and improve initial efficiency, then initial efficiency and high-temperature storage characteristics are improved, but device complexity increases
Solution Approach 1:
The patent applies multi-functionality by selecting coating materials that perform multiple functions simultaneously. The conductive polymer coating provides both electrical conductivity enhancement and protection against electrolyte side reactions. The carbon nanotube network serves both as a conductive framework and as a physical barrier reducing electrolyte access to graphene. This multi-functional approach improves performance without proportionally increasing structural complexity.
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 improves initial efficiency and high-temperature life characteristics by forming a stable solid electrolyte interface, reducing side reactions and maintaining ionic conductivity and electrochemical performance.
Implementation Method 1
a safe solid electrolyte interface (SEI) may be formed on a surface of a negative electrode by introducing two or more composite coating layers including a polymer coating layer and a pitch coating layer on both sides of a graphene sheet
Implementation Method 2
since a side reaction with an electrolyte solution is reduced, a negative electrode having improved overall performance, such as initial efficiency and high-temperature life characteristics
Data Source
AI summary
The present invention relates to a composite negative electrode material for a secondary battery, and a negative electrode and a lithium secondary battery which include the same, and particularly to a composite negative electrode material for a secondary battery, which includes a graphene sheet, and two or more coating layers formed on both sides of the graphene sheet, wherein the two or more coating layers include at least one polymer coating layer and at least one pitch coating layer, and the graphene sheet and the two or more coating layers are included in a weight ratio of greater than 1:greater than 0.01 to less than 0.1, and a negative electrode and a lithium secondary battery which include the same.