Silicon Anode Composite with Metal Nitride and Fluoride Coatings
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Lithium secondary batteries with silicon anodes face rapid capacity degradation due to pulverization and continuous formation of solid electrolyte interface layers from repeated volume expansion and shrinkage during charging and discharging.
Innovation Solution
A composite anode active material is developed, comprising silicon, a metal nitride, and a metal fluoride, where the metal nitride and fluoride are independently disposed on the silicon surface, forming a coating that stabilizes the surface and reduces internal stress, thereby preventing pulverization and accommodating volume expansion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon is used as anode active material to achieve high specific capacity, then the specific capacity is improved, but the anode undergoes pulverization and continuous formation of solid electrolyte interface layers due to volume expansion and shrinkage
Solution Approach 1:
The patent employs a core-shell structure where silicon is nested within a metal silicide core. The metal silicide core acts as a buffer that can accommodate the volume expansion of silicon during lithium insertion while maintaining structural integrity, preventing pulverization and reducing solid electrolyte interface layer formation.
Solution Approach 2:
The patent creates a composite anode material consisting of silicon combined with metal silicide and metal nitride. This composite structure leverages the high capacity of silicon while the metal silicide and nitride components provide structural stability and stress tolerance during volume changes, resolving the contradiction between capacity and stability.
2Stability of the object's composition
If metal silicide core with silicon shell is used to accommodate volume expansion, then the structural stability is improved, but the complexity of material synthesis is increased
Solution Approach 1:
The patent performs preliminary heat treatment of metal silicide in a nitrogen atmosphere before combining with silicon. This pre-treatment forms a protective metal nitride layer on the metal silicide surface, which simplifies the overall synthesis process by preventing direct reaction between metal silicide and silicon, while ensuring structural stability.
Solution Approach 2:
The patent applies different treatments to different parts of the material: metal silicide is heat-treated in nitrogen to form nitride on its surface, while silicon is combined with this treated metal silicide. This localized treatment approach achieves structural stability without requiring complex uniform treatment of the entire composite material.
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 anode active material enhances the electrochemical properties and lifespan of lithium secondary batteries by suppressing side reactions and reducing the formation of solid electrolyte interface layers, leading to improved charge/discharge efficiency and extended cycle life.
Implementation Method 1
heat-treating the milled metal silicide in a nitrogen atmosphere to form a heat-treated metal silicide comprising a metal nitride on a surface
Implementation Method 2
contacting the heat-treated metal silicide with a metal fluoride to dispose the metal fluoride on a surface of the heat-treated metal silicide and to form a coating comprising the metal fluoride
Data Source
AI summary
A composite anode active material includes: a silicon anode active material, a metal nitride; and a metal fluoride, wherein the metal nitride and the metal fluoride are each independently disposed on at least one surface of the silicon anode active material.