Flexible Carbon Conductive Agent for Compression-Resistant Electrodes
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Solution Overview
Problem
Existing lithium-ion batteries face issues with reduced lifespan due to mechanical stresses from external factors like vehicle vibrations, which increase electrode resistance, and internal factors such as silicon anode expansion and cathode lattice changes, leading to decreased durability and conductivity.
Innovation Solution
A carbon material with a bulk modulus of less than or equal to 2 GPa, an average graphene domain size of greater than or equal to 50 nm, and specific structural parameters enhances flexibility and electrical conductivity, suitable for use as a conductive agent in both anode and cathode to improve power storage devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional carbon materials with high rigidity are used to ensure structural stability, then electrode integrity is maintained, but flexibility against compression from mechanical stresses is insufficient
Solution Approach 1:
The patent changes the bulk modulus parameter of carbon materials from conventional high-rigidity values (>2 GPa) to a specific low-rigidity range (0.1-2 GPa). This parameter change enables the carbon material to simultaneously provide structural integrity and flexibility against compression from mechanical stresses, resolving the contradiction between electrode integrity and compressibility.
Solution Approach 2:
The patent employs composite carbon materials with specific structural characteristics (graphene domain size ≥50 nm, layered structure with 1-6 stacking layers) that combine the strength benefits of rigid carbon structures with the flexibility of softer, more compressible phases. This composite approach allows the material to maintain electrode integrity while adapting to mechanical stresses.
2Stability of the object's composition
If rigid crystal lattice structures are used in cathode to maintain structural stability, then electrode framework integrity is preserved, but micro-motion from dimensional changes increases resistance
Solution Approach 1:
The patent applies bulk modulus parameter changes to cathode materials, selecting carbon materials with 0.1-2 GPa bulk modulus that can accommodate dimensional changes during lithium-ion insertion/removal. This reduces micro-motion within the crystal lattice, maintaining stability while preventing resistance increase and extending charge/discharge lifespan.
3Quantity of substance
If silicon particles are used as anode active material to increase capacity, then energy density is improved, but expansion during charge/discharge reduces lifespan
Solution Approach 1:
The patent introduces low-rigidity carbon material (bulk modulus 0.1-2 GPa) as an intermediary between silicon particles and the electrode structure. This intermediary carbon phase absorbs the expansion stress of silicon during lithiation, preventing particle fracture and maintaining electrical conductivity, thus preserving both high capacity and long lifespan.
Solution Approach 2:
The patent changes the rigidity parameter of the carbon matrix surrounding silicon particles from conventional high-rigidity values to low-rigidity values (0.1-2 GPa bulk modulus). This parameter change allows the carbon matrix to flexibly accommodate silicon expansion, maintaining structural integrity and electrical conductivity throughout charge/discharge cycles.
4Strength
If high bulk modulus carbon materials are used to ensure mechanical strength, then structural stability is maintained, but electrical conductivity and flexibility against compression are reduced
Solution Approach 1:
The patent inverts the conventional approach by selecting carbon materials with low bulk modulus (0.1-2 GPa) rather than high bulk modulus. This parameter change reveals that softer, more flexible carbon structures with specific graphene domain sizes (≥50 nm) actually provide superior electrical conductivity and mechanical strength when properly structured, resolving the contradiction between rigidity and conductivity.
Data Source
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AI summary
An object is to provide a carbon material that can achieve high electrical conductivity or durability together with flexibility against compression and to provide a power storage device containing the carbon material inside an electrode. The present invention provides a carbon material having a bulk modulus K that is less than or equal to 2 GPa and an average graphene domain size L that is greater than or equal to 50 nm, a cathode (212) for a power storage device and an anode (214) for a power storage device in which the carbon material is used as a conductive agent, and a power storage device (200) including a cathode and/or an anode including the carbon material as a conductive agent.