Si-Al Alloy Anode with Crystalline and Amorphous Phases
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Solution Overview
Problem
Current lithium secondary batteries face challenges with carbonaceous anode active materials reaching theoretical capacity limits and new materials like silicon and tin experiencing significant volume expansion, leading to poor cycle characteristics and electrode separation.
Innovation Solution
An anode active material comprising both crystalline and amorphous phases of silicon-metal alloys, where the metal in both phases can be the same or different, with the amorphous phase contributing to electric capacity, is developed to control volume expansion and cycle characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon or tin is used as anode active material to increase capacity beyond theoretical limit of carbonaceous materials, then electric capacity is improved, but volume change during charging-discharging increases significantly causing electrode separation and poor cycle characteristics
Solution Approach 1:
The patent applies composite materials by creating an alloy system combining silicon (or tin) with aluminum and at least one additional metal element. This composite structure allows the silicon phase to provide high capacity while the aluminum and other metal elements form intermetallic compounds that constrain volume expansion, thereby maintaining cycle characteristics while achieving capacity beyond carbonaceous material limits
Solution Approach 2:
The patent changes the compositional parameters by specifically controlling the ratio of silicon to aluminum to other metal elements within defined ranges (Si:Al = 1:(0.1-2.0), with additional metals at 1-30 wt% of total alloy). By optimizing these parameter ranges, the material achieves both high capacity and acceptable volume stability during lithium insertion/extraction cycles
2Volume of moving object
If alloy-type materials (Si-M or Sn-M) are used to suppress volume expansion through metal silicide and metal-tin phases, then volume change is reduced, but control over electric capacity and cycle characteristics remains insufficient
Solution Approach 1:
The patent applies local quality by creating distinct phases with different functions within the alloy: silicon-rich regions provide lithium insertion/extraction capacity while aluminum-based intermetallic compounds provide structural stability. The localized distribution of these phases with specific composition ratios enables simultaneous achievement of volume control and performance optimization
Solution Approach 2:
The patent achieves precise control by defining specific compositional parameters: Si:Al ratio of 1:(0.1-2.0), additional metal content of 1-30 wt% of total alloy, and particle size of 1-50 μm. These parameter specifications enable reproducible control over both volume expansion and electrochemical performance
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 material achieves superior electric capacity and cycle characteristics, with the amorphous phase ratio being crucial in minimizing volume expansion and maintaining battery performance over 50 cycles.
Implementation Method 1
a material including both a crystalline phase and an amorphous phase of Si and Si-metal alloy
Implementation Method 2
carbonaceous materials are used as anode active material... allow intercalation/deintercalation of lithium (Li) via alloying reactions with lithium
Implementation Method 3
the Si single phase existing separately from the Si-metal alloy contributes to electric capacity even though it is an amorphous phase... capable of binding with and release from lithium during charging-discharging and, thus, provides battery capacity through electrochemical reactions
Data Source
AI summary
Disclosed is an anode active material including: a crystalline phase comprising Si and a Si-metal alloy; and an amorphous phase comprising Si and a Si-metal alloy, wherein the metal of the Si-metal alloy of the crystalline phase is the same as or different from the metal of the Si-metal alloy of the amorphous phase.