Flexible Carbon Conductive Agent for Long-Life Battery Electrodes
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Solution Overview
Problem
Lithium-ion batteries face challenges due to the expansion of silicon particles in the anode during charge and discharge cycles, leading to reduced lifespan, and the dimensional changes in the cathode's crystal lattice causing increased electrode resistance and reduced lifespan.
Innovation Solution
A carbon material with a bulk modulus K less than or equal to 2 GPa and an average graphene domain size L greater than or equal to 50 nm is developed, which provides flexibility and high electrical conductivity, suitable for use as a conductive agent in both the cathode and anode of power storage devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon particles are used as anode active material, then battery capacity is improved, but particle expansion during charge/discharge reduces lifespan
Solution Approach 1:
The patent employs flexible carbon particles with specific bulk modulus (K ≤ 2 GPa) as a coating shell around silicon particles. This flexible shell accommodates the expansion and contraction of silicon during lithium insertion/extraction, preventing particle fracture and maintaining electrode integrity over multiple cycles, thus resolving the contradiction between high capacity and long lifespan
Solution Approach 2:
The patent creates a composite structure combining silicon core with flexible carbon shell, forming a core-shell composite material. This composite approach allows the silicon to provide high capacity while the carbon matrix provides mechanical flexibility and structural stability, simultaneously achieving both improved capacity and extended lifespan
2Stability of the object's composition
If rigid crystal lattice is used in cathode, then structural stability is improved, but micro-motion from dimensional change increases resistance
Solution Approach 1:
The patent introduces flexible carbon particles as a buffer matrix in the cathode structure. These particles with low bulk modulus can accommodate the micro-dimensional changes of the cathode crystal lattice during lithium insertion/extraction, absorbing micro-motion and preventing contact resistance increase, thus maintaining both structural stability and low resistance
Solution Approach 2:
The flexible carbon particles act as an intermediary material between the cathode active material and the conductive network. They mediate the mechanical stress and dimensional changes, providing a compliant interface that maintains electrical contact while accommodating lattice expansion/contraction, thereby preventing resistance increase
3Ease of manufacture
If conventional carbon materials are used, then manufacturing simplicity is maintained, but flexibility against mechanical vibration is insufficient
Solution Approach 1:
The patent specifies precise parameter ranges for carbon particles (bulk modulus K ≤ 2 GPa, specific surface area 100-2000 m²/g, pore volume 0.5-2.0 cm³/g) to achieve optimal flexibility. By controlling these physical parameters, the patent maintains compatibility with conventional manufacturing processes while achieving superior vibration resistance through carefully selected material properties
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 carbon material achieves high electrical conductivity and durability while maintaining flexibility against mechanical vibrations, resulting in a long-life power storage device.
Implementation Method 1
a carbon material superior in flexibility against compression and electrical conductivity or durability can be realized when the bulk modulus K is less than or equal to 2 GPa
Data Source
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. Provided are 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 for a power storage device and an anode for a power storage device in which the carbon material is used as a conductive agent, and a power storage device including a cathode and/or an anode including the carbon material as a conductive agent.