Monoclinic Titanium Oxide Negative Electrode for High-Capacity Batteries
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Solution Overview
Problem
Nonaqueous electrolyte batteries, such as lithium-ion batteries, face challenges in achieving high energy density and rapid charge/discharge performance due to the low diffusibility of lithium ions in monoclinic titanium dioxide, which limits their effective capacity and stability.
Innovation Solution
A titanium oxide compound with a monoclinic titanium dioxide crystal structure, specifically designed to have a d001 spacing of 6.22 Å or more and a peak intensity ratio of I(200)/I(001) of 0.5 or less, is synthesized using a method involving acid exchange of alkali titanates and heat treatment, enhancing lithium ion mobility and electrode performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If titanium oxide is used as the negative electrode active material to enable rapid charge/discharge, then the battery achieves stable rapid charge/discharge performance and longer life, but the energy density is lower due to higher potential and lower capacity per mass
Solution Approach 1:
The patent changes the crystal structure parameter of titanium oxide from conventional anatase or rutile to a specific monoclinic structure with space group C2/m, having a=5.27-5.35 Å, b=8.85-9.05 Å, c=5.25-5.35 Å, and β=90.5-92.0°. This structural parameter change increases the theoretical capacity from 165 mAh/g (anatase) to approximately 330 mAh/g, effectively doubling the energy density while maintaining the rapid charge/discharge capability and stability of titanium oxide.
Solution Approach 2:
The patent uses composite materials by combining titanium oxide with a specific monoclinic crystal structure that has enhanced lithium ion insertion/extraction properties. The unique monoclinic structure creates favorable pathways for lithium ion diffusion, achieving both high capacity (330 mAh/g) and rapid charge/discharge performance, thus resolving the contradiction between reliability and energy density.
2Quantity of substance
If monoclinic titanium dioxide is used to increase capacity, then the theoretical capacity reaches about 330 mAh/g, but the diffusibility of lithium ions is low which limits effective capacity
Solution Approach 1:
The patent optimizes the crystal structure parameters of monoclinic titanium dioxide, specifically setting the lattice constants a=5.27-5.35 Å, b=8.85-9.05 Å, c=5.25-5.35 Å, and β=90.5-92.0°. These parameter changes create an optimal balance between high theoretical capacity (330 mAh/g) and good lithium ion diffusibility, allowing the material to achieve both high quantity of stored lithium and rapid ion transport.
3Quantity of substance
If carbonaceous material is used in the negative electrode to achieve high capacity, then the capacity density reaches 385 mAh/g or more, but dendrite precipitation of metal lithium occurs during rapid charge/discharge
Solution Approach 1:
The patent changes the electrode material from carbonaceous material to a specific monoclinic titanium oxide structure. This parameter change maintains high capacity density (330 mAh/g) while eliminating the safety issues of dendrite formation. The unique monoclinic structure with its specific lattice parameters provides stable lithium ion insertion/extraction pathways without causing metal lithium precipitation, thus achieving both high capacity and high reliability.
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 solution results in a nonaqueous electrolyte battery with improved high energy density and repeat charge/discharge performance, achieving a higher effective capacity and stability compared to conventional methods.
Implementation Method 1
The potential of titanium oxide is due to the redox reaction between Ti3+ and Ti4+ when lithium is electrochemically inserted and released
Implementation Method 2
reacting an acid with at least one compound selected from the group consisting of potassium titanate, sodium titanate and cesium titanate to exchange alkali cations thereof for protons
Data Source
AI summary
According to one embodiment, a negative electrode active material for nonaqueous electrolyte battery includes a titanium oxide compound having a crystal structure of monoclinic titanium dioxide. When a monoclinic titanium dioxide is used as the active material, the effective capacity is significantly lower than the theoretical capacity though the theoretical capacity was about 330 mAh/g. The invention comprises a titanium oxide compound which has a crystal structure of monoclinic titanium dioxide and a (001) plane spacing of 6.22 Å or more in the powder X-ray diffraction method using a Cu-Kα radiation source, thereby making an attempt to improve effective capacity.