Expanded Graphite Anode for High-Capacity Lithium-Ion Batteries
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional carbon anode materials for lithium-ion batteries face limitations in achieving high reversible capacity and long cycle life due to low electrical conductivity and high irreversible capacity, with existing treatments like mild oxidation only partially addressing these issues, resulting in specific capacities often below the theoretical maximum of 372 mAh/g.
Innovation Solution
A process involving chemical or electrochemical treatment of laminar graphite materials to expand the interplanar spacing to at least 0.400 nm, creating ideal locations for lithium ion accommodation, using materials like graphite oxide or fluoride, and incorporating an amorphous carbon phase or conductive binder to enhance electrical conductivity and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional carbon anode materials are used, then the battery structure is simple and easy to manufacture, but the specific capacity is limited below the theoretical maximum of 372 mAh/g
Solution Approach 1:
The patent applies parameter changes by systematically varying the intercalation ratio (x in LixC6) through controlled chemical treatment conditions, achieving optimal capacity enhancement. By adjusting treatment parameters such as oxidant concentration, treatment time, and temperature, the invention transforms conventional graphite into high-capacity anode material with x exceeding 1, thereby achieving specific capacities greater than 500 mAh/g while maintaining manufacturability
Solution Approach 2:
The patent employs composite materials by creating intercalation compounds that combine graphite with various agents (oxidants, fluorine, etc.) to form LixC6 with enhanced properties. This composite approach allows the carbon anode to simultaneously achieve high specific capacity, improved conductivity, and reduced irreversible capacity loss by integrating multiple functional components within the graphite structure
2Quantity of substance
If amorphous carbon phase is increased to enhance capacity, then specific capacity increases, but electrical conductivity decreases
Solution Approach 1:
The patent applies local quality by creating a heterogeneous structure where graphitic crystallites with high conductivity are dispersed within an amorphous carbon matrix. This local differentiation allows regions of high capacity (amorphous phase) to coexist with regions of high conductivity (graphitic domains), resolving the contradiction between capacity enhancement and electrical conductivity maintenance
Solution Approach 2:
The patent uses composite materials by combining graphitic carbon and amorphous carbon in a controlled ratio within the anode structure. This composite approach enables the material to simultaneously exhibit the high capacity characteristics of amorphous carbon and the high conductivity properties of graphitic carbon, achieving both improved specific capacity and maintained electrical performance
3Reliability
If mild oxidation treatment is applied, then surface properties are improved, but the interplanar spacing expansion is insufficient
Solution Approach 1:
The patent applies parameter changes by intensifying the oxidation treatment parameters beyond conventional mild oxidation. By using stronger oxidants, longer treatment times, or combined treatment approaches, the invention achieves sufficient interplanar spacing expansion (d002 ≥ 0.400 nm) while maintaining improved surface properties, thereby resolving the contradiction between surface quality and structural transformation
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 treated carbonaceous materials exhibit specific capacities greater than 500 mAh/g, with improved cycling behavior and reduced capacity fade, significantly exceeding theoretical limits and demonstrating enhanced performance in lithium-ion batteries.
Implementation Method 1
chemically or electrochemically treating a laminar graphite material to form a graphite crystal structure having an interplanar spacing d002 of at least 0.400 nm
Implementation Method 2
chemically or electrochemically treating a laminar graphite material to form a graphite crystal structure having an interplanar spacing d002 of at least 0.400 nm
Implementation Method 3
graphite that can be intercalated with lithium and the resulting graphite intercalation compound may be expressed as LixC6
Implementation Method 4
incorporating an amorphous carbon phase or conductive binder to enhance electrical conductivity and stability
Implementation Method 5
protective surface-electrolyte interface layer (SEI), which results from the reaction between lithium and the electrolyte during the first several cycles of charge-discharge
Data Source
AI summary
This invention provides a process for producing a lithium secondary battery. The process comprises: (a) providing a positive electrode; (b) providing a negative electrode comprising a carbonaceous material capable of absorbing and desorbing lithium ions, wherein the carbonaceous material is obtained by chemically or electrochemically treating a laminar graphite material to form a graphite crystal structure having an interplanar spacing d002 of at least 0.400 nm as determined from a (002) reflection peak in powder X-ray diffraction; and (c) providing a non-aqueous electrolyte disposed between the negative electrode and the positive electrode to form the battery structure. This larger interplanar spacing (greater than 0.400 nm, preferably no less than 0.55 nm) implies a larger interstitial space between two graphene planes to accommodate a greater amount of lithium. The resulting battery exhibits an exceptionally high specific capacity, an excellent reversible capacity, and a long cycle life.