Lithium-Doped SiOx Anode Material With Argon Heat Treatment
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Lithium secondary batteries face challenges with low energy density due to the low theoretical capacity of graphite negative electrodes and the deteriorated life characteristics of Si-based materials caused by large volume expansion, as well as issues with initial coulombic efficiency and irreversible phase formation in SiOx materials.
Innovation Solution
Doping lithium into SiOx-based materials through a heat treatment process using a mixture of a lithium source and SiOx under specific inert atmosphere conditions to suppress the formation of nitrogen compounds and enhance initial efficiency, resulting in a high-energy density lithium secondary battery system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If SiOx material is used as negative electrode active material, then volume expansion is reduced and life characteristic is improved, but initial coulombic efficiency deteriorates due to formation of irreversible phase
Solution Approach 1:
Lithium is doped into the SiOx material beforehand through heat treatment before the battery is assembled and operated. This preliminary doping action ensures that lithium is already present in the structure to participate in reversible reactions from the first charge-discharge cycle, preventing the formation of irreversible phases and improving initial coulombic efficiency while maintaining the low volume expansion benefits of SiOx
Solution Approach 2:
The chemical composition of the SiOx material is modified by introducing lithium dopants, changing the material's parameters to optimize both initial efficiency and cycle life. The lithium content is controlled at specific ratios (Li/Si = 0.3-1.0) to achieve the desired balance between initial coulombic efficiency and structural stability during cycling
2Ease of manufacture
If nitrogen atmosphere is used during heat treatment, then atmosphere is inert and simple, but nitrogen compounds form as irreversible phase reducing efficiency
Solution Approach 1:
An argon atmosphere is used during heat treatment instead of nitrogen atmosphere. Argon is an inert gas that does not react with lithium or silicon oxide under heat treatment conditions, preventing the formation of nitrogen compounds such as Li2NH, LiNH2, LiNO3, Li3N, NSiO2, NSi2O, and Si3N4 that would otherwise form irreversible phases and reduce initial efficiency
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 improves initial charge and discharge efficiency, cycle life, and energy density by reducing the formation of irreversible phases and nitrogen compounds, leading to a more efficient and stable negative electrode material.
Implementation Method 1
performing a purge with an argon gas having a purity of 99.90% or more to create an inert atmosphere, and mixing a silicon oxide and a lithium precursor and performing heat treatment to prepare negative electrode active material particles
Implementation Method 2
performing a purge with an argon gas having a purity of 99.90% or more to create an inert atmosphere
Data Source
AI summary
Provided are a negative electrode active material which includes a negative electrode active material particles which includes a silicon oxide (SiOx, 0<x≤2); and at least one lithium silicate selected from Li2SiO3, Li2Si2O5, and Li4SiO4 in at least a part of the silicon oxide. The negative electrode active material has a content of a nitrogen element according to X-ray photoelectron spectroscopy (XPS) of 1.45 atom % or less. Also provided are a negative electrode and a lithium secondary battery including the same.