Cracked Carbon Core Negative Electrode for High-Rate Lithium Batteries
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Solution Overview
Problem
Secondary lithium batteries face challenges with low input and output characteristics and high rate capabilities due to the porous structure of carbonaceous materials used as negative active materials, which leads to clogged pores and decreased performance.
Innovation Solution
A negative active material with a high crystallinity carbonaceous core and an amorphous carbon layer on its surface, along with metal nanoparticles, is developed. The carbonaceous core is prepared by expanding graphite using an acid and heat treating it to create a cracked surface for improved lithium ion intercalation and deintercalation, enhancing the battery's specific surface area and conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If porous carbonaceous materials are used as negative active material, then battery capacity is improved, but input and output characteristics and high rate characteristics decrease due to clogged pores
Solution Approach 1:
The negative active material is segmented into a core-shell structure where the core contains porous carbonaceous material for high capacity and the shell provides open pathways for ion transport. This segmentation allows simultaneous achievement of high capacity and good rate characteristics by separating the functions of energy storage and ion transport.
Solution Approach 2:
A composite structure is formed by combining porous carbonaceous material with conductive additives and binding agents in specific ratios and configurations. The composite design optimizes both the capacity-contributing porous structure and the conductivity-providing matrix, resolving the contradiction between capacity and rate performance.
2Quantity of substance
If porous carbonaceous materials are used as negative active material, then battery capacity is improved, but high rate characteristics decrease
Solution Approach 1:
Different regions of the negative active material are given different properties: the core region has high porosity for capacity while the surface and interconnected pathways have optimized conductivity and open structure for fast ion transport. This local quality differentiation allows the material to simultaneously achieve high capacity and fast charging/discharging rates.
3Stability of the object's composition
If crystallinity of carbonaceous material is increased, then structural stability is improved, but lithium ion intercalation and deintercalation kinetics may be reduced
Solution Approach 1:
The carbonaceous material structure is designed with controlled crystallinity in certain dimensions while maintaining amorphous or less-ordered regions in other dimensions. This dimensional differentiation allows structural stability where needed while preserving fast ion diffusion pathways in other directions, resolving the contradiction between stability and kinetics.
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 resulting lithium battery exhibits improved input and output characteristics and high rate capabilities, with increased lithium ion accessibility and reduced volumetric expansion of metal nanoparticles, leading to enhanced performance and stability.
Implementation Method 1
The carbonaceous core is prepared by expanding graphite using an acid
Implementation Method 2
heat treating it to create a cracked surface for improved lithium ion intercalation and deintercalation
Implementation Method 3
when lithium ions are intercalated and deintercalated between the positive and negative electrodes, oxidation and reduction reactions occur
Implementation Method 4
oxidation and reduction reactions occur, and thus, electrical energy is generated
Implementation Method 5
a peak with respect to a surface (002) at a Bragg angle 2θ of 26.4°±0.1° in an X-ray diffraction spectrum
Implementation Method 6
a peak with respect to a surface (002) at a Bragg angle 2θ of 26.4°±0.1° in an X-ray diffraction spectrum
Data Source
AI summary
Provided are a negative active material, a method of preparing the same, and a lithium battery including the negative active material, wherein the negative active material includes a carbonaceous material that has a peak with respect to a surface (002) at a Bragg angle 2θ of 26.4°±0.1° in an X-ray diffraction spectrum, has a full width at half maximum of the peak with respect to the surface (002) of about 0.2° to about 0.6°, has an interlayer spacing (d002) of the surface (002) measured by X-ray diffraction of about 3.36 Å to about 3.37 Å, and has a crystallite size measured from the full width at half maximum of the peak with respect to the surface (002) of about 10 nm to about 45 nm, wherein the carbonaceous material includes a core; and an amorphous carbon layer disposed on a non-cracked surface portion of the core.