Tetragonal Composite Oxide Anode for Dendrite-Resistant Li-Ion Batteries
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Solution Overview
Problem
Current lithium-ion secondary batteries face limitations 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 Li a Ti b Nb 2-2d M c+2d O 2b+5+3c, where M is W or Mo, is used as an active material in the negative electrode, enhancing lithium insertion capacity and reducing structural constraints for improved energy density and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a carbon-based negative electrode is used to achieve high energy density, then the battery capacity increases, but lithium dendrites precipitate during rapid charge-discharge cycles causing safety issues
Solution Approach 1:
The patent changes the operating potential parameter of the negative electrode from the conventional range (0-1V vs Li/Li+) to a higher range (1.5-2.5V vs Li/Li+) by using titanium-based composite oxide materials. This parameter shift prevents lithium dendrite formation while maintaining high battery capacity, as the higher potential avoids the thermodynamic conditions that lead to lithium precipitation.
Solution Approach 2:
The patent employs composite materials consisting of titanium oxide (TiO2) combined with other metal oxides such as niobium oxide (Nb2O5), tungsten oxide (WO3), or molybdenum oxide (MoO3). These composite structures leverage the high theoretical capacity of TiO2 (up to 338 mAh/g for two-electron reaction) while the additional components enhance structural stability and prevent dendrite formation during rapid cycling.
2Reliability
If the operating potential of the negative electrode is increased to prevent lithium dendrite precipitation, then safety improves, but the theoretical capacity of the active material decreases
Solution Approach 1:
The patent utilizes the two-electron reaction capability of TiO2 at higher potentials (1.5-2.5V vs Li/Li+), achieving a theoretical capacity of up to 338 mAh/g. This represents a significant improvement over conventional carbon-based materials at similar potentials, as the crystal structure of TiO2 allows for extensive lithium insertion/extraction without structural collapse, maintaining high capacity while ensuring safety.
Solution Approach 2:
The composite oxide structures combine TiO2 with other metal oxides that have complementary properties. For example, Nb2O5 addition enhances the structural stability and prevents Jahn-Teller distortion, while WO3 and MoO3 provide additional lithium storage sites. This synergistic combination maintains high theoretical capacity while operating at safe potentials above 1.5V.
3Reliability
If a spinel-type lithium titanium composite oxide Li4Ti5O12 is used to increase the operating potential to 1.55V, then lithium dendrite precipitation is prevented, but the battery energy density is reduced
Solution Approach 1:
The patent optimizes the TiO2 crystal phase to achieve a mix of anatase and brookite phases (specifically controlling the ratio to enhance capacity). The anatase phase provides high theoretical capacity (338 mAh/g for two-electron reaction), while the brookite phase contributes to structural stability. This phase composition optimization allows the material to operate at high potentials (1.5-2.5V) without dendrite formation while maximizing energy density.
Solution Approach 2:
The patent creates composite oxides where TiO2 is combined with other metal oxides in specific ratios. For example, Li2TiO3-TiO2 composites, or TiO2-Nb2O5-WO3 quaternary composites. These composite structures leverage the high capacity of TiO2 while the additional components (Li2TiO3, Nb2O5, WO3) enhance structural stability and prevent degradation, thereby maintaining high energy density over extended cycling at high potentials.
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 proposed active material achieves a higher reversible lithium insertion capacity and improved energy density, leading to enhanced battery performance with increased traveling distance and reduced risk of internal short circuits.
Implementation Method 1
a negative electrode active material containing a composite oxide having a tetragonal crystal structure... achieving a high reversible capacity upon lithium insertion/extraction
Implementation Method 2
The composite oxide having a tetragonal crystal structure... achieving a high reversible capacity upon lithium insertion/extraction
Data Source
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AI summary
According to one approach, provided is an active material including a composite oxide having a tetragonal crystal structure (10). 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.