Silicon-Silicon Oxide Negative Electrode Conductivity
Solution Overview
Problem
Lithium ion secondary batteries using a mixture of silicon and silicon oxide as negative electrode active material face challenges in maintaining high electric conductivity at high current densities, leading to decreased discharge capacity, especially in applications requiring high-rate power sources like hybrid and electric vehicles.
Innovation Solution
A negative electrode with a negative electrode active material layer containing silicon and silicon oxide, where the film thickness to particle size distribution ratio (D99/D50) is between 1.2 to 2.0 and the density is between 1.2 to 1.6 g/cm3, is developed to enhance electric conductivity and prevent damage during manufacturing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a mixture of silicon and silicon oxide is used as negative electrode active material, then cycle characteristics are improved, but electric conductivity deteriorates
Solution Approach 1:
The patent applies parameter changes by precisely controlling the film thickness to particle size ratio (D99/D50) to be within 1.2 to 2.0 and the density to be within 1.2 to 1.6 g/cm³. This optimization of physical parameters enables the silicon-silicon oxide mixture to maintain both good cycle characteristics and sufficient electric conductivity, resolving the contradiction between reliability and manufacturing precision.
2Power
If current density during discharging is increased, then power output is improved, but discharge capacity decreases significantly
Solution Approach 1:
The patent resolves this contradiction by optimizing the film thickness to particle size ratio (D99/D50) to between 1.2 and 2.0 and controlling density between 1.2 to 1.6 g/cm³. These parameter changes enable the negative electrode to maintain good electric conductivity, allowing high discharge capacity to be preserved even at high current densities, thus achieving both high power output and high discharge capacity.
3Quantity of substance
If film thickness is increased to improve capacity, then battery capacity is improved, but electric conductivity deteriorates
Solution Approach 1:
The patent resolves this contradiction by optimizing the film thickness to particle size ratio (D99/D50) to be within 1.2 to 2.0 and controlling the density to be within 1.2 to 1.6 g/cm³. This allows the film thickness to be increased for higher capacity while maintaining good electric conductivity through the optimized ratio and density parameters.
4Ease of manufacture
If particle size is increased to reduce manufacturing complexity, then manufacturing ease is improved, but film density control becomes difficult
Solution Approach 1:
The patent resolves this contradiction by specifying that the particle size distribution D99 should be in the range of 7 to 27 μm and the film thickness to particle size ratio (D99/D50) should be between 1.2 and 2.0. These parameter specifications make particle size control more manageable while ensuring the film density remains within the optimal range of 1.2 to 1.6 g/cm³.
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 enables high discharge capacity at high rates, effectively addressing the conductivity issues and maintaining performance in high-rate applications.
Implementation Method 1
the stress caused by expansion and shrinkage of silicon during charging and discharging is relaxed by silicon oxide
Implementation Method 2
a current collector that reversibly intercalates and deintercalates lithium ions
Data Source
AI summary
A negative electrode includes a negative electrode active material layer containing a negative electrode active material mainly containing silicon and silicon oxide. In the negative electrode, the ratio of the film thickness of the negative electrode active material layer to the particle size distribution D99 is in the range of 1.2 to 2.0, the value of the D99 is in the range of 7 to 27 μm, and the negative electrode active material layer has a density ranging from 1.2 to 1.6 g/cm3.