SiGe Nanowire Anode Core-Shell Gradient
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Solution Overview
Problem
Conventional anode materials for lithium ion cells, such as Si and Ge, face challenges due to excessive volume expansion during lithiation/delithiation, leading to structural destruction and reduced charging/discharging capacity, while attempts to address this through complex nanostructures require complex synthesizing processes and result in lower yield and capacity.
Innovation Solution
A nanowire anode material composed of silicon and germanium, where silicon is distributed to the surface and germanium to the inner part, undergoes heat treatment in a hydrogen atmosphere to enhance structural stability and capacity retention, allowing for a simpler preparation method and improved performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If complex nanostructures are formed to maintain morphology during lithiation/delithiation, then structural stability is improved, but manufacturing complexity increases and yield rate decreases
Solution Approach 1:
The patent applies local quality by creating a core-shell nanowire structure where the inner core region and outer shell region have different compositions (different Si/Ge ratios). This allows the core to provide structural stability while the shell enhances capacity, resolving the contradiction between structural integrity and manufacturing simplicity.
2Stability of the object's composition
If internal empty spaces are formed to reduce volume expansion, then structural stability is improved, but volume capacity decreases
Solution Approach 1:
The patent changes the compositional parameters by creating a gradient structure where Si and Ge are distributed differently in the core and shell regions. This allows the material to accommodate volume expansion through compositional variation rather than requiring empty spaces, thus maintaining both structural stability and high volume capacity.
3Quantity of substance
If silicon content is increased to improve capacity, then charging/discharging capacity is improved, but volume expansion increases leading to structural destruction
Solution Approach 1:
The patent uses composite materials by combining Si and Ge in a nanowire structure with differentiated distribution. The composite structure leverages the high capacity of Si while using Ge to mitigate volume expansion, achieving both high capacity and structural integrity through material composition rather than adding buffer materials.
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 results in excellent structural stability, capacity retention, and rate capability, with the silicon distribution fine-tuning overpotential and extending the lifespan of the lithium ion cell.
Implementation Method 1
The method includes performing heat treatment with respect to the nanowire including silicon (Si) and germanium (Ge) under a hydrogen atmosphere
Implementation Method 2
distributing the silicon (Si) and the germanium (Ge) included in the nanowire to a surface of the nanowire and an inner part of the nanowire, respectively
Data Source
AI summary
The disclosure describes a nanowire for an anode material of a lithium ion cell and a method of preparing the same. The nanowire includes silicon (Si) and germanium (Ge). The nanowire has a content of the silicon (Si) higher than a content of the germanium (Ge) at a surface thereof, and has the content of germanium (Ge) higher than the content of the silicon (Si) at an inner part thereof.