Hard Carbon Anode Pore Structure for Stable High-Capacity Batteries
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Solution Overview
Problem
Current graphite-based negative electrode active materials for lithium-ion and sodium-ion batteries have reached capacity limits, and existing hard carbon materials exhibit low actual specific capacity, high irreversible capacity, and lack a stable charge-discharge plateau, hindering the enhancement of energy density and cycle performance in secondary batteries.
Innovation Solution
A hard carbon material with controlled micropores and ultramicropores, specific oxygen and optional nitrogen or sulfur content, and tailored electrical conductivity, enhancing ion adsorption and intercalation-deintercalation processes, is used as the negative electrode active material, with a preparation method involving controlled calcination and gas treatment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If graphite is used as negative electrode active material, then the battery can achieve stable cycle performance, but the capacity development has reached the theoretical limit of 372 mAh/g, making it difficult to further improve energy density
Solution Approach 1:
The invention changes the material parameters by transitioning from graphite to hard carbon materials with different pore structures. By controlling pore volume (0.01-0.2 cm³/g) and pore size distribution (micropores <2 nm and ultramicropores <0.7 nm), the specific capacity is enhanced while maintaining cycle stability, thus resolving the capacity limit of graphite
Solution Approach 2:
The invention introduces a porous structure with specific micropore and ultramicropore characteristics into the hard carbon material. This porous architecture provides additional ion storage sites and facilitates ion transport, enabling higher specific capacity while maintaining structural stability for good cycle performance
2Quantity of substance
If existing hard carbon materials are used as negative electrode active material, then the theoretical specific capacity is high, but the actual specific capacity is low with high irreversible capacity and lack of stable charge-discharge plateau
Solution Approach 1:
The invention introduces a controlled porous structure with micropores and ultramicropores that provides stable ion insertion/extraction pathways. This porous architecture ensures uniform stress distribution during cycling, creating stable charge-discharge plateaus and reducing irreversible capacity loss
Solution Approach 2:
The invention optimizes physical parameters including pore volume (0.01-0.2 cm³/g), pore size distribution, and oxygen content (2-7 mass%) to achieve both high actual specific capacity and stable charge-discharge behavior. These parameter adjustments transform the material from theoretical potential to practical performance
3Quantity of substance
If the pore volume of ultramicropores is increased to enhance specific capacity, then the ion adsorption capability improves, but the structural stability may be compromised
Solution Approach 1:
The invention optimizes the pore volume of ultramicropores within a specific range (0.01-0.2 cm³/g) rather than maximizing it indefinitely. This controlled parameter adjustment ensures sufficient ion adsorption sites for high capacity while preventing excessive porosity that would compromise structural integrity
Solution Approach 2:
The invention creates different pore size regions (micropores and ultramicropores) with distinct functions within the same material. Ultramicropores provide ion storage for high capacity, while the overall pore structure and carbon matrix maintain structural stability, achieving local optimization of different regions
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 stable low-potential plateau, high specific capacity, and improved reversible capacity, increasing the energy density and cycle performance of secondary batteries, particularly lithium-ion and sodium-ion batteries.
Implementation Method 1
A hard carbon material containing a carbon element and an oxygen element, wherein a mass percentage of the oxygen element in the hard carbon material ranges from 2% to 7%, the hard carbon material facilitates adsorption of active metal ions in the micropores and the intercalation-deintercalation within the ultramicropores
Implementation Method 2
the hard carbon material facilitates adsorption of active metal ions in the micropores and the intercalation-deintercalation within the ultramicropores
Implementation Method 3
a mass of the oxygen element in the carbonyl group and the carboxyl group accounts for 60% to 99% of a total mass of the oxygen element in the hard carbon material, the presence of the oxygen element in the hard carbon material in the above forms, with its percentage controlled within the above range, further facilitates redox reactions of active metal ions
Data Source
AI summary
A hard carbon material contains micropores and ultramicropores, a pore diameter of the micropores is less than 2 nm, a pore diameter of the ultramicropores is less than 0.7 nm, a pore volume of the micropores accounts for 95% to 100% of a total pore volume, a pore volume of the ultramicropores ranges from 0.01 cm3/g to 0.2 cm3/g, and the pore volume of the ultramicropores accounts for 80% to 99% of the total pore volume. The negative electrode active material provided in this application exhibits a stable low-potential plateau, high specific capacity, and high reversible capacity, and applying the negative electrode active material of this application to secondary batteries enhances the energy density of secondary batteries while improving their cycle performance.