Niobium-Titanium Composite Anode Material for Fast-Charging Li-Ion Batteries
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Solution Overview
Problem
Existing lithium-ion secondary batteries with carbon-based negative electrodes suffer from dendrite formation and internal short-circuits during quick charge and discharge, while titanium oxide negative electrodes offer stability but at the cost of low energy density and high electrode potential.
Innovation Solution
The use of a composite active material comprising a first niobium titanium composite oxide with a monoclinic crystal structure and a second niobium titanium composite oxide with a rutile-type crystal structure, which are mixed and heat-treated to control the Nb occupancy in the 4i site, enhancing lithium ion mobility and electronic conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a carbon-based negative electrode is used, then the capacity for unit weight is high, but dendrites deposit during quick charge and discharge causing safety issues
Solution Approach 1:
The patent uses a composite oxide material containing both titanium and niobium elements in specific ratios (Ti:Nb = 1:0.5 to 1:2) to combine the high capacity characteristics of carbon-based materials with the safety and stability of titanium oxide-based materials, eliminating dendrite formation while maintaining practical capacity
2Reliability
If titanium oxide is used as the negative electrode, then stability and quick charge discharge performance are improved, but energy density decreases due to higher potential and lower capacity
Solution Approach 1:
The patent changes the chemical composition parameters by incorporating niobium elements alongside titanium oxide, creating a composite oxide with optimized Ti:Nb ratios that adjust the electrode potential and capacity parameters to achieve both stability and high energy density
3Stability of the object's composition
If the crystal structure contains few sites for occluding lithium, then lithium is readily stabilized, but the substantial capacity decreases
Solution Approach 1:
The patent creates local variations in the crystal structure by forming a composite oxide with specific Ti:Nb ratios, where different regions of the material provide different functions - some regions stabilize lithium while others provide capacity, achieving both goals simultaneously through spatial differentiation of properties
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
This approach achieves excellent repetitive quick charge-and-discharge performance, high energy density, and high-temperature durability, addressing the limitations of both carbon-based and titanium oxide electrodes.
Implementation Method 1
The potential of titanium oxide is attributable to the oxidation-reduction reaction between Ti 3+ and Li +
Implementation Method 2
a first monoclinic niobium-titanium composite oxide and a second rutile-type niobium titanium composite oxide, which are mixed and heat-treated to control the Nb occupancy in the 4i site
Data Source
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AI summary
According to one approach, an active material is provided. The active material includes a first niobium titanium composite oxide expressed by a general formula (I), and a second niobium titanium composite oxide expressed by a general formula (II) and having a rutile-type crystal structure. The first niobium titanium composite oxide belongs to a crystal structure of a space group C2/m, and has a difference Δp between a maximum value and a minimum value of Nb occupancy in a 4i site, the difference Δp being 0.50 ≤ Δp ≤ 0.80, KaNb2-bMb+1-cTicO7 ... (I) Ti1-yNbyOz ... (II) .