SiOx Anode Coating Structure for Volume Change and Conductivity
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Solution Overview
Problem
Existing secondary batteries with silicon-based negative electrode active materials face challenges in effectively controlling volume change during charge and discharge, leading to reduced battery lifetime, increased resistance, and decreased capacity retention.
Innovation Solution
A negative electrode active material is developed, comprising a core of SiOx (0≤x<2) with an intermediate layer of silicon nitride, silicon oxynitride, or a mixture thereof, and a carbon coating layer containing nitrogen-doped carbon, which improves conductivity and controls volume change.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a SiO2 layer or carbon coating layer is formed on the silicon-based particle surface, then volume control during charge and discharge is improved, but resistance increases and capacity retention decreases
Solution Approach 1:
The patent applies composite materials by creating a multi-layered coating structure on silicon-based particles consisting of a SiO2 layer, a polymer composite layer, and a conductive carbon coating layer. This composite structure addresses the contradiction by combining materials with different properties: the SiO2 layer provides volume control, the polymer composite enhances stability, and the conductive carbon layer maintains electrical conductivity and capacity retention.
Solution Approach 2:
The patent implements the nested doll principle by forming multiple coating layers in a nested configuration on the silicon-based particle surface. The SiO2 layer is formed first, followed by the polymer composite layer, and finally the conductive carbon coating layer. Each layer is nested within the outer layers, creating a hierarchical structure that simultaneously achieves volume control while maintaining conductivity and capacity retention.
2Stability of the object's composition
If a polymer composite is added on the carbon coating layer to control volume change, then volume stability is improved, but conductivity decreases and resistance increases
Solution Approach 1:
The patent uses the nested doll principle by placing the conductive carbon coating layer on the outermost surface, enclosing the polymer composite layer which in turn encloses the SiO2 layer. This nested configuration ensures that the conductive carbon layer is in direct contact with the electrolyte, maintaining electrical conductivity while the inner polymer composite layer provides volume stability.
Solution Approach 2:
The patent applies composite materials by creating a multi-functional coating system where each layer contributes a specific property. The polymer composite layer provides volume stability, while the outer conductive carbon coating layer restores and maintains electrical conductivity, thus resolving the contradiction between volume stability and conductivity.
3Stability of the object's composition
If excessive coating is applied on the silicon-based particle, then volume control is improved, but lithium ion absorption becomes difficult and capacity is reduced
Solution Approach 1:
The patent applies the local quality principle by optimizing the thickness and composition of each coating layer to achieve appropriate properties at different locations. The SiO2 layer thickness is controlled to provide volume control without excessive bulk, the polymer composite layer is applied in moderate amounts for stability, and the conductive carbon coating layer is formed with sufficient thickness to ensure conductivity but not so thick as to block lithium ion diffusion. This localized optimization of each layer's properties resolves the contradiction between volume control and capacity.
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 solution enhances the capacity retention of the battery, reduces resistance, and effectively manages volume change during charging and discharging, while also delaying temperature increases due to potential short circuits, thus preventing exothermic reactions.
Implementation Method 1
a carbon coating layer comprising nitrogen-doped carbon
Implementation Method 2
comprises an intermediate layer comprising silicon nitride, silicon oxynitride, or a mixture thereof and a carbon coating layer comprising nitrogen-doped carbon, conductivity of the negative electrode active material may be improved and a volume change of a core in the negative electrode active material may be effectively controlled
Data Source
AI summary
A negative electrode active material which includes a secondary particle including first primary particles, wherein the first primary particle includes a core including SiOx, wherein 0≤x<2, an intermediate layer which covers at least a portion of a surface of the core and includes silicon nitride, silicon oxynitride, or a mixture thereof, and a carbon coating layer which covers at least a portion of the intermediate layer and includes nitrogen-doped carbon, and a negative electrode and a lithium secondary battery which include the same.