High-Entropy Silicon Anode Composite for Volume-Stable Li-Ion Batteries
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Solution Overview
Problem
Alloy materials used in lithium-ion batteries experience significant volume changes during lithium ion intercalation and deintercalation, leading to performance issues.
Innovation Solution
A composite negative electrode active material is developed, comprising a silicide phase and a silicon phase, where the silicide phase contains an intermetallic compound of silicon and multiple metal elements, satisfying a high entropy condition to enhance mechanical strength and mitigate volume changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If alloy materials are used as negative electrode active material to achieve high theoretical capacity density, then energy density is improved, but volume change during lithium ion intercalation and deintercalation increases
Solution Approach 1:
The patent employs a composite material consisting of a silicide phase containing an intermetallic compound of silicon and multiple metal elements (N≥5) satisfying the high entropy condition, combined with a silicon phase. This composite structure allows the material to achieve high theoretical capacity density through lithium alloying while the high entropy silicide phase mitigates volume changes during lithium ion intercalation and deintercalation, thus resolving the contradiction between energy density and volume stability
2Quantity of substance
If alloy material with high silicon content is used to increase capacity, then discharge capacity is improved, but mechanical strength decreases due to large volume change
Solution Approach 1:
The composite material combines a silicon phase (providing high discharge capacity through lithium alloying) with a silicide phase containing an intermetallic compound of silicon and N≥5 metal elements satisfying the high entropy condition. The high entropy silicide phase forms a mechanically strong framework that constrains the silicon phase, preventing excessive volume expansion and maintaining mechanical strength even at high silicon content (60-90 atom % Si), thus achieving both high discharge capacity and mechanical strength
Solution Approach 2:
The patent utilizes the high entropy condition (parameter related to compositional complexity with N≥5 metal elements) to fundamentally change the material properties of the silicide phase. This parameter change results in enhanced mechanical strength and reduced volume change, allowing the composite material to maintain structural integrity while achieving high discharge capacity through high silicon content
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 material exhibits a reduced volume change during lithium ion cycling, improving the stability and performance of lithium-ion batteries.
Implementation Method 1
the silicide phase contains an intermetallic compound of a silicon element and a metal element Me other than the silicon element, the metal element Me includes N kinds or more constituent elements Mi, where i=1 to N, and 5≤N
Data Source
AI summary
Disclosed is a negative electrode active material for a secondary battery containing: a composite material that has a silicide phase and a silicon phase, wherein the silicide phase contains an intermetallic compound of a silicon element and a metal element Me other than the silicon element, the metal element Me includes N kinds or more constituent elements Mi, where i=1 to N, and 5≤N, and a condition represented by the following expression is satisfied: 1.5<−ΣCi·lnCi, where Ci represents a mole fraction of each of the N kinds or more constituent elements Mi.