Silicon-Carbon Anode Structure With Central Void for Cycle Life
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Solution Overview
Problem
Lithium secondary batteries face challenges with graphite anode active materials having low specific capacity and poor cycle-life characteristics due to volume expansion during charging and discharging.
Innovation Solution
An anode active material comprising a silicon-carbon composite with a void in the central portion, including silicon nanoparticles and amorphous carbon, where the central void radius corresponds to 30% to 50% of the anode's radius, effectively absorbing volume expansion and improving cycle-life characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-based anode active material is used to increase capacity, then specific capacity is improved, but volume expansion during charging and discharging occurs causing poor cycle-life characteristics
Solution Approach 1:
The anode active material is divided into two distinct regions: a central portion containing silicon nanoparticles and a surface layer containing carbon material. This segmentation allows the silicon core to provide high capacity while the carbon shell constrains volume expansion, resolving the contradiction between capacity improvement and cycle-life deterioration.
Solution Approach 2:
The invention creates a composite structure combining silicon nanoparticles with carbon material (graphite, hard carbon, or amorphous carbon). The composite leverages the high capacity of silicon while utilizing carbon's dimensional stability to suppress volume expansion during lithium insertion/extraction, thereby improving cycle-life characteristics.
2Quantity of substance
If central portion radius is smaller than 30% of anode radius, then capacity is improved, but volume expansion is not sufficiently suppressed reducing cycle-life
Solution Approach 1:
The invention optimizes the geometric parameter of the central portion radius, specifying it should be 30% to 50% of the anode active material radius. This parameter optimization ensures sufficient carbon material surrounds the silicon core to constrain expansion while maintaining adequate silicon content for high capacity, achieving both capacity and cycle-life improvement.
3Reliability
If central portion radius is larger than 50% of anode radius, then volume expansion suppression is improved, but capacity is reduced
Solution Approach 1:
The invention sets the upper limit of the central portion radius at 50% of the anode radius to prevent excessive reduction of capacity. This parameter control ensures that while sufficient carbon material is present to suppress volume expansion, enough silicon nanoparticles remain in the central portion to maintain high specific 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 silicon-carbon composite anode active material reduces stress from volume expansion, enhancing cycle-life and high-rate characteristics by uniformly distributing silicon nanoparticles and minimizing amorphous carbon in the central portion, thereby maintaining excellent capacity and reducing electrode resistance.
Implementation Method 1
a silicon-carbon composite having a void in a central portion... capable of suppressing volume expansion during charging and discharging
Implementation Method 2
oxides including lithium and a transition metal with a structure capable of intercalating/deintercalating lithium ions
Data Source
AI summary
Provides are an anode active material for a lithium secondary battery and a lithium secondary battery comprising same, wherein the anode active material for a lithium secondary battery comprises a silicon-carbon composite having a void in the central portion, the radius of the central portion corresponds to 30% to 50% of the radius of the anode active material for a lithium secondary battery, and the silicon-carbon composite includes silicon nanoparticles and amorphous carbon.