Silicon-Based Anode Active Material for Lithium Secondary Batteries
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Solution Overview
Problem
Silicon-based anode active materials for lithium secondary batteries face challenges with volume expansion and initial charge/discharge efficiency due to irreversible phase formation during cycling, limiting their commercial application.
Innovation Solution
A silicon-based anode active material comprising a silicon phase, an SiOx (0<x<2) phase, and a silicon dioxide phase, prepared by dissolving alkaline hydroxide in a polar solvent, mixing with SiOx, evaporating the solvent, and heat-treating the mixture to form crystalline silicon and silicon dioxide, which improves initial charge/discharge efficiency and reduces volume expansion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-based anode active material is used to achieve high capacity, then the battery capacity increases significantly, but the volume expansion during lithium ion intercalation causes decreased battery capacity over cycles and safety concerns
Solution Approach 1:
The silicon-based anode active material is divided into multiple small particles rather than using large chunks. This segmentation reduces the overall volume expansion stress on individual particles and prevents catastrophic structural failure during lithium ion intercalation, thereby maintaining capacity retention over multiple cycles while preserving high capacity
Solution Approach 2:
Silicon particles are embedded within a porous carbon matrix structure. The carbon matrix acts as a container that accommodates the volume expansion of silicon during lithium ion insertion, while the porous structure provides buffer space. This nesting approach allows silicon to maintain its high capacity advantage while the carbon framework ensures structural stability and capacity retention over cycles
2Quantity of substance
If silicon-based anode active material is used to achieve high capacity, then the theoretical capacity reaches 4190 mAh/g, but irreversible phase formation during initial charge/discharge cycling deteriorates initial charge/discharge efficiency
Solution Approach 1:
The silicon-based particles are pre-coated with a carbon layer before battery assembly. This preliminary carbon coating prevents direct contact between the silicon surface and electrolyte during initial cycling, reducing irreversible phase formation and improving initial charge/discharge efficiency while preserving the high theoretical capacity of silicon
Solution Approach 2:
A carbon coating layer is introduced as an intermediary between the silicon-based active material and the electrolyte. This carbon layer mediates the initial charge/discharge reactions, preventing direct irreversible phase formation on silicon surfaces while still allowing lithium ion transport, thereby improving initial efficiency without sacrificing theoretical 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 approach enhances the initial coulombic efficiency and discharge capacity of lithium secondary batteries, making silicon-based anode active materials more viable for large-scale energy storage applications by stabilizing the silicon phase and reducing irreversible reactions.
Implementation Method 1
when it is intercalated by lithium ions
Implementation Method 2
evaporating the solvent
Implementation Method 3
heat-treating the mixture to form crystalline silicon and silicon dioxide
Data Source
AI summary
Disclosed herein is a silicon-based anode active material, comprising a silicon phase, a SiOx (0<x<2) phase and a carbon dioxide phase. Also disclosed is a secondary battery, which comprises a cathode comprising a cathode active material, an anode active material comprising an anode active material, and a separator, wherein the anode active material comprises a silicon phase, an SiOx (0<x<2) phase and a silicon dioxide phase.