Silicon-Carbon Composite Pore Structure for Battery Expansion Control
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Solution Overview
Problem
The volume expansion of silicon particles during lithium-ion battery charging and discharging leads to structural instability, particle fracture, and contact with the electrolyte, deteriorating cycle and high-temperature performance.
Innovation Solution
A silicon-carbon composite material with a controlled pore structure ratio (c-a)/b between 1.5 and 5.0, combined with a phenolic resin-based porous carbon skeleton and ultramicropores, enhances structural strength and resistance to pressure, preventing particle rupture and improving energy density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If silane deposition method is used to solve silicon expansion problem, then expansion issue is addressed through reserved-hole design, but the process complexity increases and many invalid holes are formed
Solution Approach 1:
The patent employs a porous carbon skeleton structure with controlled pore size distribution to accommodate silicon expansion. The porous structure provides reserved space for volume changes while maintaining structural integrity, avoiding the complexity of silane deposition processes.
Solution Approach 2:
The patent creates a composite material system consisting of silicon particles embedded in a carbon matrix with specific pore structure. This composite approach combines the high capacity of silicon with the structural stability of carbon, solving both expansion and complexity issues.
2Reliability
If reserved-hole design is implemented in silicon-carbon composite, then silicon expansion is accommodated, but particle strength decreases and particles fracture during cold-pressing
Solution Approach 1:
The patent applies local quality by creating specific pore size distributions within the carbon matrix. Different pore sizes are strategically designed: smaller pores provide structural support while larger pores accommodate silicon expansion, optimizing both strength and expansion accommodation locally within the material structure.
Solution Approach 2:
The patent changes the pore size distribution parameters of the carbon matrix to optimize the balance between strength and expansion accommodation. By controlling the ratio of different pore sizes and their spatial distribution, the material achieves both mechanical integrity and volume expansion capacity.
3Ease of manufacture
If conventional sand-milling method is used for silicon-carbon composite, then manufacturing is simpler, but silicon expansion remains severe and cycle performance deteriorates
Solution Approach 1:
The patent applies preliminary action by pre-designing the carbon matrix with an optimized pore structure before silicon particle incorporation. This pre-established framework prevents silicon expansion issues from the outset, maintaining both manufacturing simplicity and high cycle performance without requiring complex post-processing.
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 achieves higher compressive strength, maintaining cycle and high-temperature performance by reducing invalid pores and enhancing the silicon-carbon composite's resistance to pressure, thus improving battery performance.
Implementation Method 1
a porous carbon skeleton and pores of the porous carbon skeleton contain a silicon material
Data Source
AI summary
A silicon-carbon composite material includes a porous carbon skeleton and pores of the porous carbon skeleton contain a silicon material. The porous carbon skeleton satisfies: 1.5 < (c - a)/b < 5.0, where a represents a pore diameter corresponding to a cumulative pore volume percentage accounting for 10% of a total pore volume, b represents a pore diameter corresponding to a cumulative pore volume percentage accounting for 50% of the total pore volume, and c represents a pore diameter corresponding to a cumulative pore volume percentage 99% in the total pore volume. The technical solution of this application improves the cycle performance and high-temperature performance of the secondary battery while achieving a high energy density of the secondary battery.