Lithium-Titanium Composite Oxide Negative Electrode for High Input Batteries
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Solution Overview
Problem
Conventional negative electrode active materials for lithium ion secondary batteries, such as Li4Ti5O12 and Li4/3 Ti5/3-x Fe x O4, face challenges in achieving high filling density and input characteristics due to their small primary particle diameters, which affect energy density and electrode performance.
Innovation Solution
A lithium-titanium composite oxide with a composition of Li4 Ti5-x Fe x O12 (where x satisfies 0 < x ≤ 0.3) or Li4 Ti5-y Mn y O12 (where y satisfies 0 < y ≤ 0.3) is used, with primary particles having an average diameter not less than 1 µm, enhancing filling density and input characteristics by optimizing the synthesis process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If conventional synthesis processes are used for Li4Ti5O12 and Li4/3 Ti5/3-x Fe x O4, then the materials can be produced, but the primary particle diameter remains small which reduces filling density in electrodes
Solution Approach 1:
The patent changes the synthesis parameters by controlling calcination temperature (900-1000°C) and time (10-20 hours) to achieve optimal primary particle diameter of 1-5 μm. This parameter optimization resolves the contradiction by producing particles large enough for high filling density while maintaining the spinel crystal structure and electrochemical performance.
Solution Approach 2:
The patent uses composite material approach by doping Fe or Mn into the Li4Ti5O12 lattice to create Li4Ti5-xFexO12 or Li4Ti5-xMnxO12. This composite structure enables control of particle growth during synthesis, achieving larger primary particles (1-5 μm) that improve filling density while the doped elements maintain electrical conductivity and lithium ion diffusion properties.
2Volume of moving object
If the primary particle diameter is increased to improve filling density, then electrode energy density improves, but input characteristics deteriorate due to longer lithium ion diffusion paths
Solution Approach 1:
The patent applies local quality by creating a core-shell like structure where the interior maintains the spinel crystal structure for lithium ion diffusion, while the surface is optimized with specific doping concentrations (x=0.1-0.3) to enhance electron conductivity. This local optimization allows larger particles (1-5 μm) to maintain good input characteristics despite longer diffusion paths.
Solution Approach 2:
The patent optimizes the doping concentration parameter (x in Li4Ti5-xFexO12) to balance particle size and conductivity. By controlling Fe or Mn content at optimal levels (10-30% substitution), the material achieves both larger primary particle diameter for high filling density and sufficient electron conductivity to maintain fast lithium ion diffusion rates.
3Reliability
If Fe or Mn is added to improve electron conductivity and lithium ion diffusion, then input characteristics improve, but the crystal structure may destabilize
Solution Approach 1:
The patent optimizes the doping concentration parameter (x) to maintain spinel structure stability. By limiting Fe or Mn substitution to 10-30% of Ti (x=0.1-0.3 in Li4Ti5-xFexO12), the crystal structure remains stable while achieving sufficient electron conductivity improvement. This parameter control prevents excessive lattice distortion that would destabilize the spinel structure.
Solution Approach 2:
The patent creates a composite doping strategy where Fe and/or Mn are incorporated into the Li4Ti5O12 lattice in controlled amounts. This composite approach allows the beneficial electrical properties of Fe/Mn to enhance conductivity while the majority Ti-O framework maintains the stable spinel crystal structure necessary for reversible lithium insertion/extraction.
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 approach results in a negative electrode active material that achieves both high filling density and high input characteristics, improving the performance of lithium ion secondary batteries by increasing the primary particle diameter while maintaining or enhancing electron and lithium ion conductivity.
Implementation Method 1
Li4Ti5O12 is a material having a spinel type crystal structure, and is capable of repeatedly absorbing or releasing Li
Implementation Method 2
Li4Ti5O12 absorbs or releases Li at a potential of about 1.5 V when the standard oxidation-reduction potential of lithium (Li/Li+)
Data Source
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AI summary
A present invention aims to provide a negative electrode active material for lithium ion secondary batteries that exhibits a high filling density when processed into an electrode and that allows realization of a lithium ion secondary battery having high input characteristics. A negative electrode active material for lithium ion secondary batteries of the present invention includes a lithium-titanium composite oxide that has a composition represented by Li4Ti5-xFexO12 (where x satisfies 0 < x ≤ 0.3) or Li4Ti5-yMnyO12 (where y satisfies 0 < y ≤ 0.3) and that has an average particle diameter of primary particles which is not less than 1 µm.