Silicon-Carbon Anode Structure for High-Capacity Cycle Stability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Rechargeable lithium batteries face challenges in achieving high energy density, cycle life, and safety, particularly in the performance of the negative electrode active material.
Innovation Solution
A negative electrode active material is developed with a shell and crystalline silicon core coated with amorphous carbon, aggregated with additional amorphous carbon layers, enhancing capacity, efficiency, and lifespan.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If crystalline silicon is used as negative electrode active material to increase capacity, then energy density is improved, but volume expansion during lithium insertion causes structural degradation and reduced cycle life
Solution Approach 1:
The patent applies nested structure by placing crystalline silicon core inside amorphous silicon shell, which is further enclosed by carbon coating layer. This multi-layer nested design allows the crystalline silicon to provide high capacity while the amorphous silicon shell accommodates volume expansion and the carbon layer provides structural stability, thereby resolving the contradiction between energy density and cycle life.
Solution Approach 2:
The patent uses composite material structure combining crystalline silicon, amorphous silicon, and carbon materials. The crystalline silicon provides high lithium insertion capacity, the amorphous silicon shell buffers volume changes, and the carbon coating maintains structural integrity. This composite approach enables simultaneous achievement of high energy density and long cycle life.
2Stability of the object's composition
If amorphous silicon is used to reduce volume expansion, then structural stability is improved, but lithium insertion capacity is reduced
Solution Approach 1:
The patent places amorphous silicon as an intermediate shell layer surrounding the crystalline silicon core. This nested configuration allows the amorphous silicon to provide structural stability and buffer volume expansion, while the inner crystalline silicon core maintains high lithium insertion capacity, thus resolving the trade-off between structural stability and capacity.
Solution Approach 2:
The patent creates a composite structure where amorphous silicon and crystalline silicon work synergistically. The amorphous silicon phase provides dimensional stability and accommodates expansion, while the crystalline silicon phase provides high capacity. This composite material approach enables both structural stability and high lithium insertion capacity to be achieved simultaneously.
3Reliability
If carbon coating is applied to prevent structural degradation, then cycle life is improved, but lithium ion diffusion is hindered
Solution Approach 1:
The patent applies carbon coating selectively as a thin outer layer rather than a thick barrier. This localized carbon coating provides just enough structural protection to prevent degradation and improve cycle life, while maintaining sufficient porosity and thickness control to allow adequate lithium ion diffusion. The local quality of the carbon layer is optimized to balance protection and ion transport.
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 composite structure improves the negative electrode's capacity, efficiency, and lifespan, leading to better performance in rechargeable lithium batteries.
Implementation Method 1
each containing an active material capable of intercalation and deintercalation of lithium ions
Implementation Method 2
Electrical energy can be produced by oxidation and reduction reactions when the lithium ions are intercalated and deintercalated
Implementation Method 3
performing a third heat treatment on the third particle and a second carbon precursor at a temperature in a range of about 800° C. to about 1000° C.
Data Source
AI summary
A negative electrode active material, a rechargeable lithium battery including the same, and a preparation method of the same are provided. The negative electrode active material includes an aggregated body in which two or more composites are aggregated, the composites each including silicon (Si) and carbon (C), and a coating layer around (e.g., surrounding) the aggregated body, wherein the composites each include a core containing crystalline silicon, a first shell containing a first amorphous carbon on the core, and a second shell containing amorphous silicon on the first shell, and wherein the coating layer contains a second amorphous carbon.