Hard Carbon Micropore Structure for High-Capacity Battery Anodes
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Solution Overview
Problem
Current negative active materials in electrochemical devices, such as graphite, have limitations in increasing energy density due to their high irreversible capacity and average delithiation potential, which restricts the performance of lithium-ion and sodium-ion batteries.
Innovation Solution
A hard carbon material with a specific pore structure, including micropores, is developed, which has a controlled metal and non-metal element content, optimized pore volume, and scattering characteristics, enabling enhanced lithium storage capacity and reversible capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If graphite is used as negative active material, then electrical conductivity and stability are improved, but energy density is limited due to theoretical capacity ceiling of 372 mAh/g
Solution Approach 1:
The patent employs hard carbon material with a developed pore structure containing micropores (0.003-0.2 μm) as the negative active material. The porous structure provides additional lithium storage sites beyond the conventional graphite intercalation sites, enabling the material to achieve a theoretical capacity exceeding 372 mAh/g while maintaining structural stability and electrical conductivity.
2Quantity of substance
If hard carbon material with micropores is used, then lithium storage capacity is improved, but irreversible capacity is reduced
Solution Approach 1:
The patent optimizes specific parameters of the hard carbon material including pore volume (0.003-0.2 cm³/g), micropore size distribution (0.003-0.2 μm), and heteroatom content (N: 0.1-5 wt%, O: 0.1-5 wt%). These parameter optimizations ensure that the micropores provide reversible lithium storage while minimizing irreversible capacity loss during the first charge-discharge cycles.
3Quantity of substance
If pore volume is increased to enhance lithium storage, then energy density is improved, but manufacturing precision becomes more difficult to control
Solution Approach 1:
The patent employs a precursor material (such as phenolic resin, lignin, or other carbonizable organic compounds) that inherently possesses a pore structure before carbonization. The precursor's molecular structure and processing conditions are pre-designed to generate the desired micropore distribution (0.003-0.2 μm) and pore volume (0.003-0.2 cm³/g) after carbonization, thereby simplifying the control of pore structure parameters during manufacturing.
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 hard carbon material achieves a high energy density, high first-cycle Coulombic efficiency, and good cycle performance by storing lithium ions in its micropores, thereby improving the electrochemical device's performance.
Implementation Method 1
a pore volume of the micropores of the hard carbon material measured by a nitrogen adsorption method is V2
Data Source
AI summary
A hard carbon material has a pore structure. A scattering vector of the pore structure in a small-angle X-ray scattering spectrum is N1 nm−1, and 0.1≤N1≤7. The hard carbon material exhibits a scattering intensity convex peak. A full-width-at-half-maximum of the convex peak is L1 nm−1, and 0.1≤L1≤3.5. A pore volume of micropores of the hard carbon material measured by a nitrogen adsorption method is V2 cc/g, and 0<V2≤0.01. The pore structure of the hard carbon material of this application includes micropores. During lithium storage, lithium ions can be stored in the micropores, thereby providing a reversible capacity. In addition, when used as a negative active material of an electrochemical device, the hard carbon material of this application endows the electrochemical device with a high energy density, a high first-cycle Coulombic efficiency, and good cycle performance.