Si-Carbon Negative Electrode Pore Structure for Low-Swelling Batteries
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Solution Overview
Problem
Si-based materials increase secondary battery capacity but face issues with negative electrode swelling and deterioration of charge-discharge cycle characteristics, with existing technologies only partially addressing these challenges.
Innovation Solution
A negative electrode with a specific pore diameter distribution and Si-based material composition, including a carbon material and Si-based material with an average particle diameter of at least 4 μm and a content of at least 30% of the total active material, optimized through a manufacturing process involving a pore-forming material and heat treatment to achieve two peak pore diameters measured by mercury porosimetry.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If Si-based material is used to increase battery capacity, then battery capacity is improved, but negative electrode swelling occurs and charge-discharge cycle characteristics deteriorate
Solution Approach 1:
The patent applies porous materials by constructing a negative electrode mixture layer with a specific pore diameter distribution (first peak at 0.003-0.01 μm, second peak at 0.03-0.1 μm). These porous structures accommodate the volume expansion of Si-based materials during lithium insertion, preventing electrode swelling and maintaining structural integrity over charge-discharge cycles, thereby improving both capacity and cycle stability
Solution Approach 2:
The patent employs composite materials by combining Si-based materials with carbon materials in a specific ratio (Si-based material content of 20-80 mass%). This composite structure leverages the high capacity of Si-based materials while the carbon component provides structural stability and conductivity, resolving the contradiction between achieving high capacity and maintaining cycle reliability
2Quantity of substance
If Si-based material content is increased to enhance capacity, then battery capacity increases, but negative electrode swelling increases
Solution Approach 1:
The porous structure with dual peak pore diameter distribution provides void spaces that accommodate the expansion of Si-based materials during charging. The smaller pores (first peak) provide fine-scale accommodation while larger pores (second peak) provide macro-scale buffer space, effectively managing volume changes and preventing excessive electrode swelling even at high Si-based material content
Solution Approach 2:
The patent introduces pore-forming materials as intermediaries during the electrode manufacturing process. These materials create the desired pore structure and are subsequently removed, leaving behind a controlled porous network that mediates between the high-capacity Si-based material and the need to limit swelling, allowing the electrode to expand and contract without structural failure
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
This configuration enhances battery capacity, suppresses negative electrode swelling, and improves charge-discharge cycle characteristics, achieving high capacity retention and reduced swelling rates.
Implementation Method 1
a second step of heat-treating the coating film after the first step, thereby decomposing and vaporizing the pore-forming material to form a negative electrode mixture layer
Data Source
AI summary
A negative electrode for a secondary battery according to one aspect of the present disclosure is characterized by comprising a negative electrode current collector and a negative electrode mixture layer disposed on the negative electrode current collector, and is characterized in that: the negative electrode mixture layer contains a negative electrode active material including a carbon material and a Si-based material; a pore diameter distribution of the negative electrode mixture layer as measured by a mercury press-in method has two peak values R1 and R2; the peak value R1 is in the range of 0.5-1.5 μm; the peak value R2 is in the range of 2-10 μm; an average particle diameter of the Si-based material is 4 μm or more; and the contained amount of the Si-based material with respect to the total amount of the negative electrode active material is 30 mass % or more.