SiOx Negative Electrode Doping for Conductivity
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Solution Overview
Problem
Si-based negative electrode active material particles in lithium ion secondary batteries have low electron conductivity, leading to increased resistance and decreased cycle characteristics due to their reactivity with lithium ions and electrolytes, despite offering higher capacity than carbon-based materials.
Innovation Solution
Doping SiOx particles with group 13 or 15 elements, such as boron, phosphorus, or arsenic, to create a gradient of dopant concentration from the surface to the center, enhancing electron conductivity by generating holes or carriers, thereby reducing discharging and charging resistances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If Si-based negative electrode active material particles are used to achieve higher capacity, then the capacity of the lithium ion secondary battery is improved, but the resistance increases due to low electron conductivity
Solution Approach 1:
The patent applies parameter changes by doping SiOx particles with group 13 or 15 elements to alter the electrical conductivity parameter. The doping concentration is controlled within specific ranges (0.01-5 at%) to optimize electron conductivity while maintaining capacity, directly resolving the contradiction between high capacity and low resistance
Solution Approach 2:
The patent creates a composite material structure by combining SiOx with dopant elements (group 13 or 15 elements). This composite approach enhances electron conductivity through the dopant atoms while preserving the high capacity characteristics of SiOx, effectively addressing the resistance issue without sacrificing capacity
2Reliability
If carbon is coated on the surface of Si-based particles to improve electron conductivity, then resistance is reduced, but Li ions are consumed by reaction with carbon leading to decreased cycle characteristic
Solution Approach 1:
The patent extracts the harmful carbon coating step from the process and replaces it with doping. By removing the carbon coating that causes Li ion consumption, the patent eliminates the trade-off between conductivity improvement and cycle life degradation
Solution Approach 2:
The patent introduces dopant atoms as intermediaries within the SiOx crystal structure to improve conductivity. These dopants act as internal mediators that enhance electron transport without requiring external carbon coatings, thereby avoiding Li ion consumption and preserving cycle characteristics
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 doping process improves electron conductivity, specifically reducing discharging and charging resistances, leading to better output and input characteristics in lithium ion secondary batteries without compromising initial capacity or efficiency.
Implementation Method 1
doping SiOx particles with group 13 or 15 elements, such as boron, phosphorus, or arsenic, to create a gradient of dopant concentration from the surface to the center, enhancing electron conductivity by generating holes or carriers
Data Source
AI summary
A negative electrode active material particle has a composition represented by the following formula (I): SiOxDy . . . (I). In the formula (I), x satisfies 0≤x≤1.5. D is a group 13 element or a group 15 element in a periodic table. In an outermost surface of the negative electrode active material particle, y satisfies 10−11≤y≤10−1. In a center of the negative electrode active material particle, y satisfies y≤10−12.