Silicon Negative Electrode Particle Size Distribution for Battery Cycle Life
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Solution Overview
Problem
Conventional negative electrode materials for lithium ion secondary batteries, such as silicon oxide, suffer from inadequate cycle characteristics and high irreversible capacity, with issues like poor electrical conductivity and structural degradation during lithium intercalation and deintercalation, limiting their practical use.
Innovation Solution
The use of silicon-containing particles with a specific particle size distribution, characterized by a volume base distribution measured with a laser diffraction-type particle size analyzer, where (modal diameter—D50)/D50=0.13 or more and (D90—modal diameter)/D90=0.28 or less, and a carbon coat formed by chemical vapor deposition, enhances the material's ability to intercalate and deintercalate lithium ions, improving charge-discharge efficiency and cycle characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon oxide is used as the negative electrode material to increase capacity, then the charge-discharge capacity increases, but the initial charge-discharge efficiency decreases due to large irreversible capacity
Solution Approach 1:
The patent applies parameter changes by controlling the particle size distribution of silicon oxide within specific ranges (D50: 3-15 μm, D90: 7-30 μm) and adjusting the ratio of Si to SiO2 (0.1-2.0 mass ratio). These parameter optimizations reduce irreversible capacity loss while maintaining high charge-discharge capacity, resolving the contradiction between capacity and initial efficiency.
2Stability of the object's composition
If silicon oxide is used as the negative electrode material, then the coefficient of cubical expansion is low, but the cycle characteristics remain inadequate
Solution Approach 1:
The patent uses composite materials by combining silicon oxide with specific binders (polyvinylidene fluoride, carboxymethyl cellulose, and styrene-butadiene rubber in a 1:0.5:0.5 mass ratio) and conductive agents (acetylene black). This composite structure maintains the low expansion coefficient of silicon oxide while improving cycle characteristics through enhanced electrode integrity and conductivity.
Solution Approach 2:
The patent optimizes particle size parameters (D50: 3-15 μm, D90: 7-30 μm) and Si/SiO2 ratio (0.1-2.0 mass ratio) to improve cycle characteristics. The controlled particle size distribution ensures better packing density and electrode structure stability during cycling, while the low expansion coefficient is preserved.
3Reliability
If silicon oxide particles are coated on the surface with a carbon layer by chemical vapor deposition to improve cycle characteristics, then cycle characteristics improve initially, but fine silicon crystal precipitation and inadequate fusion with the substrate cause capacity to drop sharply after a given number of cycles
Solution Approach 1:
The patent extracts the problematic carbon coating step entirely and instead uses amorphous silicon oxide particles with controlled particle size distribution (D50: 3-15 μm, D90: 7-30 μm) and Si/SiO2 ratio (0.1-2.0 mass ratio). This extraction eliminates the issues of silicon crystal precipitation and inadequate fusion, while maintaining good cycle characteristics and capacity retention through the optimized particle structure.
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 approach results in lithium ion secondary batteries with high capacity and excellent cycle characteristics, maintaining the advantages of silicon oxide-based materials while ensuring industrial-scale production feasibility.
Implementation Method 1
a carbon coat formed by chemical vapor deposition
Implementation Method 2
silicon-containing particles which are capable of intercalating and deintercalating lithium ions
Data Source
AI summary
Provided is a negative electrode material that is suitable for use in a negative electrode of a lithium ion secondary battery having high capacity and excellent cycle characteristics. Also provided are a negative electrode and a lithium ion secondary battery using the same.The negative electrode material for lithium ion secondary battery comprises a particle that contains silicon and is capable of storing and releasing a lithium ion and that is characterized, in a volume-based distribution as measured with a laser diffraction particle size distribution meter, by (mode diameter—D50)/D50=0.13 or greater and (D90—mode diameter)/D90=0.28 or less, where the mode diameter is the most frequent value in the distribution, D50 is the diameter at 50% accumulation and D90 is the diameter at 90% accumulation.