Lithium Titanium Oxide Negative Active Material for Battery Safety
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Solution Overview
Problem
Rechargeable lithium batteries using graphite as negative active materials face issues with low energy density due to low theoretical density and potential capacity reduction, especially when misused or overcharged, and non-carbon-based oxide materials do not show sufficient battery performance.
Innovation Solution
A lithium titanium oxide with a specific full width at half maximum (FWHM) range in X-ray diffraction and average crystal size is used as a negative active material, prepared by heating a lithium titanium oxide precursor under an inert atmosphere, which improves the battery's high-rate charge characteristic, cycle-life, and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If graphite is used as negative active material, then discharge voltage and energy density are improved, but the battery is prone to swelling or capacity reduction when misused or overcharged
Solution Approach 1:
The patent changes the material parameter from graphite to lithium titanium oxide with specific crystal structure parameters (FWHM of 2θ at (111) plane between 0.08054° to 0.10067°). This parameter change maintains high energy density while fundamentally altering the electrochemical stability, preventing the swelling and capacity reduction issues that occur with graphite under overcharge or misuse conditions.
Solution Approach 2:
The patent uses lithium titanium oxide as a composite negative active material that combines the benefits of high energy density with superior stability. The specific crystal structure of lithium titanium oxide creates a composite-like behavior that resists the harmful effects of overcharge and misuse while maintaining excellent reversibility and cycle life.
2Reliability
If non-carbon-based oxide materials are used as negative active material, then safety and cycle life are improved, but battery performance is insufficient
Solution Approach 1:
The patent optimizes the crystal structure parameters of lithium titanium oxide by controlling the FWHM of the (111) plane diffraction peak to be between 0.08054° to 0.10067°. This specific parameter range corresponds to an average crystal size of 80-100 nm, which fundamentally improves both the safety/cycle life and the battery performance, resolving the previous trade-off between reliability and performance.
Solution Approach 2:
The patent segments the lithium titanium oxide into nanoscale particles with average crystal size of 80-100 nm. This segmentation increases the surface area to volume ratio, improving lithium ion diffusion kinetics and electrochemical activity, thereby enhancing battery performance while maintaining the inherent safety and cycle life benefits of oxide materials.
3Reliability
If graphite is used as negative active material, then reversibility and cycle life are improved, but energy density per unit volume is reduced due to low density
Solution Approach 1:
The patent employs lithium titanium oxide as a negative active material that combines the reversibility characteristics of graphite with higher density. The oxide material maintains excellent lithium ion intercalation and deintercalation reversibility while providing significantly higher energy density per unit volume, eliminating the need to choose between reversibility and volumetric energy density.
Solution Approach 2:
The patent changes the negative active material from low-density graphite to higher-density lithium titanium oxide with controlled crystal structure. The specific FWHM range of 0.08054° to 0.10067° at (111) plane ensures optimal crystal structure that maintains reversibility while achieving higher volumetric energy density.
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 lithium titanium oxide enhances the initial capacity, efficiency, and high-rate discharge characteristics of rechargeable lithium batteries, providing improved safety and long cycle-life, while maintaining high energy density.
Implementation Method 1
heating a lithium titanium oxide precursor under an inert atmosphere
Implementation Method 2
heating a lithium titanium oxide precursor under an inert atmosphere to provide a lithium titanium oxide
Implementation Method 3
as measured by X-ray diffraction (XRD) using a Cu Kα ray
Implementation Method 4
full width at half maximum (FWHM) of 2θ ranging from 0.08054° to 0.10067° at a (111) plane as measured by X-ray diffraction
Implementation Method 5
various carbon-based materials such as artificial graphite, natural graphite, and hard carbon, which can all intercalate and deintercalate lithium ions
Data Source
Figure 1
AI summary
A negative active material for a rechargeable lithium battery including lithium titanium oxide is provided. The lithium titanium oxide has a full width at half maximum (FWIIM) of 2θ ranging from about 0.08054° to about 0.10067° at a (111) plane (main peak, 2θ = 18.330°) as measured by XRD using a Cu Ka ray.