Monoclinic Titanium Dioxide Orientation for Battery Capacity
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Solution Overview
Problem
Existing lithium-ion batteries using titanium dioxide as an active material suffer from low reversible charge-discharge capacity and poor cycle life due to inadequate orientation of crystal grains, leading to reduced electrode performance.
Innovation Solution
A negative electrode active material with a monoclinic titanium dioxide crystal structure, specifically oriented towards the (001) plane, is developed, allowing for improved lithium ion diffusion and maintaining high electrode capacity and charge-discharge cycle performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If titanium dioxide with bronze type structure or bronze titanate type structure is used as active material, then the battery can operate, but the reversible charge-discharge capacity is considerably lower than the theoretical capacity of monoclinic titanium dioxide
Solution Approach 1:
The invention changes the crystal structure parameter of titanium dioxide from bronze type or bronze titanate type to monoclinic type, and further optimizes the orientation of crystal grains by controlling the diffraction peak intensity ratio and half-width. This parameter change enables the battery to achieve reversible charge-discharge capacity of 200 mAh/g or more while maintaining excellent cycle life of 80% or more after 50 cycles.
2Manufacturing precision
If titanium dioxide with highest intensity peak of (003) plane and half-width of 0.4 degree is used, then the crystal structure is well-defined, but the reversible charge-discharge capacity is lowered
Solution Approach 1:
The invention applies local quality by specifically orienting the crystal grains of monoclinic titanium dioxide so that the (001) plane is preferentially oriented towards the c-axis direction. This is achieved by controlling the intensity ratio I(001)/I(110) to be 1.0 or more and the half-width of the (001) peak to be 0.5-4.0 degrees, creating optimal local crystal orientation that enables both high capacity (200 mAh/g or more) and good cycle life.
3Reliability
If spinel type lithium titanate is used as active material, then the battery operates stably, but the capacity is limited to 170 mAh/g and cannot be greatly improved
Solution Approach 1:
The invention uses monoclinic titanium dioxide with specific crystal orientation as the active material, which can be considered as a composite of titanium dioxide with optimized crystal structure and orientation. This material achieves capacity of 200 mAh/g or more (exceeding spinel lithium titanate's 170 mAh/g) while maintaining electrode stability through the controlled crystal grain orientation with I(001)/I(110) ≥ 1.0 and half-width of 0.5-4.0 degrees.
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 oriented titanium dioxide compound achieves a high initial discharge capacity and excellent charge-discharge cycle performance, with a capacity of 240 mAh/g or more, which is 70% of the theoretical capacity, while maintaining electrode stability and energy density.
Implementation Method 1
allowing for improved lithium ion diffusion and maintaining high electrode capacity and charge-discharge cycle performance
Data Source
AI summary
According to one embodiment, a negative electrode active material includes a compound having a crystal structure of monoclinic titanium dioxide. The compound has a highest intensity peak detected by an X-ray powder diffractometry using a Cu-Kα radiation source. The highest intensity peak is a peak of a (001) plane, (002) plane, or (003) plane. A half-width (2θ) of the highest intensity peak falls within a range of 0.5 degree to 4 degrees.