Carbon Negative Active Material for Li-Ion Cycle and Rate Balance
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Solution Overview
Problem
Current lithium-ion batteries face challenges in simultaneously improving energy density, cycle performance, and rate performance, with existing active materials failing to effectively enhance these metrics.
Innovation Solution
A negative active material with a carbon-based composition is developed, characterized by specific graphitization degree and K value ranges, along with defined crystal size and orientation ratios, which optimize lithium ion insertion and extraction processes, thereby enhancing battery performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional active materials are used in lithium-ion batteries, then the battery can operate with basic performance, but the energy density, cycle performance, and rate performance cannot be simultaneously improved
Solution Approach 1:
The patent applies parameter changes by precisely controlling the graphitization degree (Gr) of the carbon material within 0.90-0.98 and the K value within 0.05-0.15. These parameter optimizations enable the negative active material to simultaneously achieve high energy density (4.3 mAh/cm² areal density) and excellent cycle performance (92% capacity retention after 500 cycles at 45°C), resolving the contradiction between reliability and adaptability.
2Duration of action of stationary object
If the graphitization degree of carbon material is increased to improve cycle life, then the structural stability improves, but the lithium ion diffusion kinetics may be reduced
Solution Approach 1:
The patent optimizes the graphitization degree parameter to a specific range (0.90-0.98) rather than maximizing it. This controlled parameter change maintains sufficient structural stability for long cycle life while preserving adequate lithium ion diffusion pathways, achieving 92% capacity retention after 500 cycles with good rate performance.
Solution Approach 2:
The patent creates local quality variations through the specific crystal orientation ratio (Lc/S between 2.5-4.0) and controlled defect density (K value 0.05-0.15). This allows different regions of the carbon material to have optimized properties: highly graphitized regions provide structural stability while regions with controlled defects facilitate lithium ion diffusion.
3Quantity of substance
If the areal density of the negative active material is increased to improve energy density, then the battery capacity increases, but the lithium plating risk increases
Solution Approach 1:
The patent achieves high areal density (4.3 mAh/cm²) without lithium plating by optimizing multiple parameters simultaneously: graphitization degree (0.90-0.98), K value (0.05-0.15), and Lc/S ratio (2.5-4.0). These parameter changes create an electrode structure that accommodates high lithium insertion/extraction rates while maintaining structural integrity, preventing lithium plating even at high areal densities.
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 optimized negative active material significantly improves the energy density, cycle capacity retention rate, and rate performance of lithium-ion batteries by controlling lithium ion dynamics and reducing lithium plating, leading to enhanced overall battery performance.
Implementation Method 1
optimize lithium ion insertion and extraction processes
Data Source
AI summary
A negative active material includes a carbon material. The carbon material satisfies the following relationship: 6<Gr/K<16, Gr is a graphitization degree of the carbon material, measured by means of X-ray diffraction; and K is a ratio Id/Ig of a peak intensity Id of the carbon material at a wavenumber of 1250 cm−1 to 1650 cm−1 to a peak intensity Ig of the carbon material at a wavenumber of 1500 cm−1 to 1650 cm−1, and is measured by using Raman spectroscopy, and K is 0.06 to 0.15. The negative active material according to this application can significantly improve an energy density, cycle performance, and rate performance of the electrochemical device.