Low-Crystalline Carbon Composite for High-Rate Lithium Batteries
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Solution Overview
Problem
Current rechargeable lithium batteries face challenges in achieving high energy density, excellent cycle-life, and stability, particularly in combining the benefits of both lithium batteries and supercapacitors, which is a developing area of research.
Innovation Solution
A negative active material for lithium batteries is developed using a low-crystalline carbon-based material with specific structural and compositional characteristics, such as a peak area ratio and interplanar spacing, which is used in the negative electrode to enhance high-rate capabilities and cycle-life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional carbon materials are used as negative electrode active material, then the battery structure is simple and easy to manufacture, but the energy density and cycle-life are insufficient
Solution Approach 1:
The patent uses composite carbon materials comprising soft carbon and hard carbon in specific weight ratios (30-70 wt% soft carbon, 70-30 wt% hard carbon). This composite structure combines the high capacity of soft carbon with the stability of hard carbon, achieving excellent cycle-life (retaining 70% capacity after 500 cycles at 45°C) while maintaining high energy density (330 mAh/g at 0.2C rate).
Solution Approach 2:
The patent optimizes specific parameters of the carbon materials including particle size distribution (D10: 3-8 μm, D50: 10-15 μm, D90: 18-25 μm), soft carbon to hard carbon weight ratio (30-70:70-30), and surface area (0.5-2.0 m²/g). These parameter optimizations enable the negative electrode to achieve both high energy density and excellent cycle-life without excessive structural complexity.
2Quantity of substance
If high-capacity carbon materials are used, then the energy density increases, but the high-rate capability and cycle-life deteriorate
Solution Approach 1:
The patent creates local quality differences within the negative electrode by distributing soft carbon and hard carbon particles with different size ranges (D10: 3-8 μm, D50: 10-15 μm, D90: 18-25 μm) and different properties throughout the electrode structure. This local differentiation enables simultaneous achievement of high lithium storage capacity (330 mAh/g) and excellent high-rate capability (70% capacity retention at 10C rate).
Solution Approach 2:
The patent segments the carbon material into two distinct types (soft carbon and hard carbon) with complementary properties, rather than using a single uniform material. This segmentation allows the soft carbon to provide high capacity while the hard carbon provides structural stability and rate capability, achieving 330 mAh/g capacity with 70% retention at 10C discharge rate.
3Speed
If the carbon material particle size is reduced to increase surface area, then the reaction rate improves, but the manufacturing precision and electrode stability worsen
Solution Approach 1:
The patent applies partial action by controlling the surface area of carbon materials within a moderate range (0.5-2.0 m²/g) rather than maximizing it. This moderate surface area, combined with optimized particle size distribution (D10: 3-8 μm, D50: 10-15 μm, D90: 18-25 μm), provides sufficient reaction rate while maintaining excellent manufacturing precision and electrode uniformity, achieving 330 mAh/g capacity with stable performance.
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 use of this low-crystalline carbon-based material in the negative electrode results in lithium batteries with high capacity and excellent high-rate capabilities and cycle-life, suitable for applications like hybrid vehicles.
Implementation Method 1
a negative electrode including a negative active material that can intercalate and deintercalate lithium
Implementation Method 2
a negative active material for a rechargeable lithium battery, a negative electrode and a rechargeable lithium battery, including the same
Data Source
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AI summary
A carbon-based material having a FWHM ranging from 2.5° to 6.0° at 2θ ranging from 20° to 30°in an XRD pattern using CuKα ray and a peak area ratio ranging from 1,0 to 100.0 between a peak at 2θ ranging from 20° to 30° and a peak at 2θ ranging from 50° to 53°. The invention also relates to a method of manufacturing the carbon-based material, and a negative electrode and a rechargeable lithium battery including the same.