Titanium-Niobium-Tungsten Oxide Anode for High-Capacity Li-Ion Batteries
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Solution Overview
Problem
Current lithium-ion secondary batteries face limitations in energy density and rapid charge-discharge performance, particularly with carbon-based negative electrodes prone to lithium dendrite formation and low theoretical capacity, which hinders their application in electric vehicles requiring increased traveling distance and rapid charging capabilities.
Innovation Solution
The development of a titanium-niobium-tungsten composite oxide with a monoclinic and orthorhombic crystal structure, represented by the formula LiaTibNb2WcO2b+3c+5+δ, which allows for higher lithium insertion capacity and improved operating potential, enhancing both energy density and cycle stability by adjusting the composition ratio and incorporating additive elements like vanadium and phosphorus.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a carbon-based negative electrode is used, then the energy density is improved, but lithium dendrites may be precipitated causing safety issues and reduced reliability
Solution Approach 1:
The invention changes the operating potential parameter of the negative electrode from the conventional range (0-0.2V vs Li/Li+) to a higher range (0.3-1.8V vs Li/Li+). This parameter change prevents lithium dendrite formation while maintaining high capacity, resolving the contradiction between energy density and safety/reliability
Solution Approach 2:
The invention uses composite oxide materials (such as lithium titanium composite oxide Li4Ti5O12) that combine the benefits of high operating potential with high theoretical capacity. These composite materials enable both safety (by preventing dendrites) and high energy density simultaneously
2Reliability
If Li4Ti5O12 is used in the negative electrode, then rapid charge-discharge performance and long-term reliability are improved, but the energy density decreases due to low theoretical capacity
Solution Approach 1:
The invention optimizes the composition and crystal structure parameters of lithium titanium composite oxide to achieve both high operating potential (1.55V) and high theoretical capacity (175mAh/g). By controlling the monoclinic and orthorhombic phase ratios and incorporating additive elements, the material achieves improved energy density while maintaining rapid charge-discharge performance and long-term reliability
3Quantity of substance
If tetragonal niobium titanium composite oxide is used, then the volume energy density is improved, but the operating potential is limited near 1V
Solution Approach 1:
The invention changes the crystal structure parameter from tetragonal to a combination of monoclinic and orthorhombic structures. This structural change enables the material to achieve both high operating potential (1.55V vs Li/Li+) and high theoretical capacity, resolving the contradiction between volume energy density and operating potential
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 composite oxide achieves a higher capacity per mass, improving energy density and cycle stability, enabling batteries with enhanced performance for electric vehicles by allowing greater lithium insertion and reducing the risk of dendrite formation, thus supporting increased traveling distances and rapid charging.
Implementation Method 1
The tetragonal niobium titanium composite oxide is an active material exhibiting a high capacity while having an operating potential near 1 V (vs. Li/Li+) based on the oxidation-reduction potential of lithium
Data Source
AI summary
An active material includes a composite oxide represented by the general formula LiaTibNb2WcO2b+3c+5+δ and satisfying 0≤a≤b+3c+4, 0<b<2, 0<c<2, 1.9b+2.85c+4.75≤δ≤2.1b+3.15c+5.25. A crystal structure of the composite oxide is at least one of a monoclinic structure and an orthorhombic structure.