Composite Cathode Material Balancing Voltage, Density, and Battery Life
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Solution Overview
Problem
Existing rechargeable lithium batteries face challenges in achieving high energy density, high operating voltage, and high charge-discharge efficiency while maintaining a long lifespan.
Innovation Solution
A positive electrode active material comprising a mixture of first and second particles, where the first particle is an olivine-based lithium compound (Li a1 Mn x1 Fe y1 B z1 PO 4-b1 ) with a smaller average diameter and the second particle is a lithium nickel-based composite oxide (Li a2 Ni x2 Co y2 Mn z2 O 2-b2 ) with a larger diameter, in a specific ratio, is used to enhance the performance of the battery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a single positive electrode active material is used, then the battery structure is simple, but the energy density and operating voltage cannot be simultaneously optimized
Solution Approach 1:
The patent combines two different positive electrode active materials (olivine-based lithium compound and lithium nickel-based composite oxide) into a single electrode structure. This merging allows the battery to achieve both high energy density from the lithium nickel-based material and high operating voltage from the olivine-based material, while maintaining a relatively simple overall battery structure.
Solution Approach 2:
The patent uses a composite material system consisting of two distinct positive electrode active materials with different chemical compositions and structures. The olivine-based lithium compound (Li a1 Mn x1 Fe y1 B z1 PO 4-b1) and lithium nickel-based composite oxide (Li a2 Ni x2 Co y2 Mn z2 O 2-b2) work together in the same electrode to provide complementary performance characteristics that neither material could achieve alone.
2Power
If high operating voltage materials are used, then the voltage increases, but the lifespan and charge-discharge efficiency deteriorate
Solution Approach 1:
The patent applies local quality by assigning different functional roles to different materials within the same electrode. The olivine-based lithium compound specifically provides high operating voltage and structural stability for lifespan, while the lithium nickel-based composite oxide contributes high capacity. This localized functional distribution allows the electrode as a whole to achieve both high voltage and long lifespan simultaneously.
3Productivity
If fine particles are used, then the charge-discharge efficiency increases, but the mixture density decreases
Solution Approach 1:
The patent optimizes the particle size parameters of both active materials within specific ranges (0.5-5 μm for olivine-based, 1-10 μm for lithium nickel-based). These parameter changes balance the competing requirements: keeping particles fine enough to ensure good charge-discharge efficiency while maintaining sufficient particle density to achieve high mixture density (2.4-3.0 g/cc) in the electrode.
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 combination of these particles results in a rechargeable lithium battery with improved energy density, operating voltage, charge-discharge efficiency, and extended lifespan, while also providing high mixture density and economical benefits.
Implementation Method 1
Electrical energy is produced by oxidation and reduction reactions when the lithium ions are intercalated and deintercalated into/from the positive electrode and the negative electrode
Data Source
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AI summary
Examples of the disclosure include a positive electrode active material for a rechargeable lithium battery, a positive electrode including the positive electrode active material, and a rechargeable lithium battery including the positive electrode active material. Examples of the disclosure include a positive electrode active material including a first particle containing a compound having a first average particle diameter, and a second particle containing a compound having a second average particle diameter larger than the first average particle diameter.