M-SiOx Silicon Anode Composition for Volume Change and Conductivity
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Solution Overview
Problem
Lithium secondary batteries with silicon-based particles face limitations in lifespan and initial efficiency due to excessive volume changes during charging and discharging, which are not adequately controlled by existing coatings and composite materials, leading to reduced capacity retention and increased resistance.
Innovation Solution
A negative electrode active material comprising silicon-based particles with a specific range of crystalline and amorphous phases, including metals like Li, Mg, Ca, or Ti, is developed, where the amorphous phase content is controlled between 20 wt% to 70 wt%, and a carbon coating layer is applied to minimize internal structural changes and enhance conductivity.
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 change is controlled, but conductivity decreases and resistance increases
Solution Approach 1:
The invention changes the chemical composition parameter by introducing metal elements (Li, Mg, Ca, or Ti) into the silicon oxide structure, forming M-SiOx compounds. This compositional modification maintains volume stability while preserving electrical conductivity, resolving the contradiction between volume control and conductivity maintenance
Solution Approach 2:
The invention creates a composite material structure where metal elements are integrated within the silicon oxide matrix (M-SiOx). This composite approach combines the volume-stabilizing property of silicon oxide with the conductivity-enhancing property of metal elements, achieving both volume control and maintained conductivity simultaneously
2Stability of the object's composition
If polymer composite is added on the carbon coating layer, then volume change control is enhanced, but capacity retention decreases and resistance increases
Solution Approach 1:
The invention extracts and eliminates the polymer composite layer from the multi-layer coating structure. By removing this layer, the patent avoids the capacity retention loss and resistance increase caused by polymer decomposition, while still achieving volume control through the M-SiOx core structure
Solution Approach 2:
The invention changes the coating composition by eliminating organic polymer components and relying instead on the inorganic M-SiOx structure for volume control. This parameter change from organic to inorganic composition prevents capacity loss while maintaining volume stability
3Stability of the object's composition
If excessive coating is applied on silicon-based particle, then volume change is controlled, but lithium ion absorption is hindered and capacity is reduced
Solution Approach 1:
The invention employs a thin film approach with the M-SiOx coating layer, which provides sufficient volume control functionality while maintaining thinness that allows lithium ion penetration. The flexible and permeable nature of this thin coating enables ion absorption without excessive barrier effects
Solution Approach 2:
The invention optimizes the coating thickness and composition parameters of M-SiOx to achieve a balance where the coating is thin enough to allow lithium ion diffusion but thick enough to provide volume control. The metal content parameter is adjusted to enhance both protection and ion conductivity
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 effectively minimizes initial irreversible reactions, improves initial efficiency, and extends the lifespan of lithium secondary batteries by controlling volume changes and maintaining high conductivity, resulting in enhanced discharge capacity and capacity retention.
Implementation Method 1
The negative electrode includes a negative electrode active material in which lithium ions exiting the positive electrode are intercalated and deintercalated
Implementation Method 2
silicon-based particles having a large discharge capacity may be used. However, silicon-based particles, such as SiOx (0≤x<2), undergo a volume expansion of about 300% during the charge and discharge cycles
Implementation Method 3
In order to address this limitation, a SiO2 layer or a carbon coating layer was typically formed on a surface of the silicon-based particle
Data Source
AI summary
A negative electrode active material for a lithium secondary battery, which includes a silicon-based particle represented by M-SiOx, wherein M is Li, Mg, Ca, Al, or Ti, and 0≤x<2, wherein the M-SiOx includes an amorphous phase at 20 wt% to 70 wt% based upon a total weight of the M-SiOx, thereby exhibiting excellent initial efficiency and lifespan characteristics, and a preparation method thereof.