Carbon Anode Material for Fast-Charging Li-Ion Cycle Stability
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Solution Overview
Problem
Lithium-ion secondary batteries for EVs and HEVs face challenges in achieving high energy density and maintaining input-output characteristics and cycle characteristics, as increasing current density leads to lithium deposition and SEI film growth, which impairs lithium ion mobility and deteriorates cycle characteristics.
Innovation Solution
An anode material with specific carbon characteristics, including a particle size distribution, specific surface area, and circularity, is developed to balance particle size and surface area, preventing lithium deposition and maintaining efficient lithium ion mobility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the current density is increased to shorten charging time, then the charging speed is improved, but lithium deposition occurs at the anode and input characteristics and cycle characteristics deteriorate
Solution Approach 1:
The invention applies local quality by creating a non-uniform particle size distribution within specific ranges (D10: 3-7 μm, D30: 8-15 μm, D50: 16-25 μm, D70: 26-40 μm, D90: 41-60 μm) and controlling particle shape (circularity 0.93-0.97). This localized optimization of particle characteristics at different size segments prevents lithium deposition while maintaining high charging speeds, resolving the contradiction between charging speed and cycle characteristics.
Solution Approach 2:
The invention changes physical parameters of the carbon material, specifically controlling particle size distribution (D90/D10 ratio: 2.0-4.0), specific surface area (0.8-2.5 m²/g), and circularity (0.93-0.97). These parameter changes optimize lithium ion insertion/extraction kinetics while preventing lithium deposition, thereby improving both charging speed and cycle characteristics simultaneously.
2Quantity of substance
If the thickness of anode is increased to increase energy density, then the capacity is improved, but SEI film grows and blocks gaps in the anode, impairing lithium ion mobility and deteriorating cycle characteristics
Solution Approach 1:
The invention applies local quality by using a broad particle size distribution with five distinct size segments (D10-D90 ranges). This creates varying local structures within the anode: smaller particles (D10-D30) provide high surface area for lithium insertion, while larger particles (D70-D90) maintain structural integrity and prevent SEI film blockage. This localized structural differentiation allows increased anode thickness while maintaining lithium ion mobility and cycle characteristics.
Solution Approach 2:
The invention uses a composite structure of carbon particles with different size segments and controlled circularity. This composite approach combines the advantages of small particles (high surface area, fast lithium insertion) with large particles (structural stability, reduced SEI film blockage), enabling high energy density while maintaining excellent cycle characteristics.
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 anode material enhances input-output characteristics and cycle stability by preventing lithium deposition and maintaining efficient lithium ion mobility, thus improving the battery's energy density and charging speed.
Implementation Method 1
The graphite has a structure in which hexagonal planes of carbon atoms are regularly stacked, and when it is used as an anode material of a lithium-ion secondary battery, an insertion or elimination reaction of a lithium-ion proceeds at the edge of a hexagonal plane to perform charge or discharge
Implementation Method 2
Amorphous carbon has irregularly stacked hexagonal planes, or does not have hexagonal planes. Therefore, in an anode material using amorphous carbon, an insertion or elimination reaction of lithium-ions proceeds on the entire surface of the anode material
Data Source
AI summary
An anode material for a lithium-ion secondary battery, includes a carbon material satisfying the following (1) and (2):(1) D90/D10 of a particle size on a volume basis is larger than 2.0 and less than 4.3;(2) N/S, which is a value obtained by dividing a number N of particles with an equivalent circle diameter of 5 μm or less based on a number standard in a total number of measured particles of 10,000, by a specific surface area S determined by nitrogen adsorption measurement at 77 K, is 750 (particles·g/cm2) or more.