Tetragonal Composite Oxide Anode for High-Capacity Li-Ion Batteries
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Solution Overview
Problem
Current lithium-ion secondary batteries face challenges in achieving high energy density and rapid charge-discharge performance while maintaining long-term reliability, particularly due to issues with lithium dendrite precipitation and low theoretical capacity of existing active materials.
Innovation Solution
A composite oxide with a tetragonal crystal structure, represented by the formula LiaTibNb2−2dMc+2dO2b+5+3c, where M is tungsten (W) or molybdenum (Mo), is used as an active material in the negative electrode, enhancing lithium insertion capacity and operating potential, thereby improving energy density and charge compensation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a carbon-based negative electrode is used, then the energy density is high, but lithium dendrites precipitate during rapid charge-discharge cycles
Solution Approach 1:
The invention changes the operating potential parameter by using a composite oxide with a specific crystal structure that operates at a higher potential than carbon-based materials, thereby preventing dendrite precipitation while maintaining high capacity through controlled lithium insertion/extraction mechanisms
Solution Approach 2:
The invention employs a composite oxide material combining multiple elements (Li, Ti, Nb, and other transition metals) in a specific crystal structure, leveraging the synergistic effects of different elements to achieve both high capacity and dendrite resistance that neither component could achieve alone
2Reliability
If Li4Ti5O12 is used in the negative electrode, then rapid charge-discharge performance and long-term reliability are improved, but the theoretical capacity is low
Solution Approach 1:
The invention creates a composite oxide that combines the stability benefits of Li4Ti5O12 with additional transition metal elements that contribute higher capacity, achieving a material that maintains the structural stability needed for rapid charge-discharge while increasing the theoretical capacity through enhanced lithium insertion capabilities
Solution Approach 2:
The invention modifies the compositional parameters by incorporating specific ratios of transition metals (Ti, Nb, and others) to adjust the crystal structure and electronic properties, thereby increasing the theoretical capacity while preserving the operational stability characteristics of the parent Li4Ti5O12 structure
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 tetragonal composite oxide structure allows for increased lithium insertion, leading to higher reversible capacity and improved energy density, along with enhanced operating potential and cycle life, addressing the limitations of carbon-based and spinel-type lithium titanium composite oxides.
Implementation Method 1
TiNb2O7 is an active material which exhibits 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
According to one embodiment, provided is an active material including a composite oxide having a tetragonal crystal structure. The composite oxide is represented by general formula LiaTibNb2−2dMc+2dO2b+5+3c. Here, M is one selected from the group consisting of W and Mo, 0≤a≤b+4+3c, 0<b<2−2d, and 0<c<2−4d.