Artificial Graphite Anode Coating for Fast Charging and Low Polarization
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Solution Overview
Problem
Electric vehicles experience longer charging times compared to conventional oil-fueled vehicles, leading to range anxiety and limited market adoption. Existing methods to improve battery kinetics focus on reducing the thickness or compacted density of the negative-electrode film layer, which only enhances charging performance in low State of Charge (SOC) states and decreases energy density.
Innovation Solution
A negative-electrode active material is developed, comprising a core of artificial graphite coated with amorphous carbon. The material has a specific particle size distribution, with a volume-based median particle size (Dv50) between 8 μm and 15 μm and a volume-based particle size distribution (Dv99) of 24 μm or less, enhancing active ion diffusion and reducing polarization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the thickness or compacted density of the negative-electrode film layer is reduced to improve battery kinetics, then charging performance in low SOC states is enhanced, but energy density decreases
Solution Approach 1:
The patent applies local quality by creating a core-shell structure where the artificial graphite core and amorphous carbon coating have different properties optimized for their specific functions. The core provides high capacity while the coating enhances ion diffusion, allowing the electrode to achieve good kinetics without reducing overall thickness or density.
Solution Approach 2:
The patent uses composite materials by combining artificial graphite with amorphous carbon in a core-shell configuration. This composite structure leverages the high capacity of graphite and the fast ion diffusion of amorphous carbon, achieving improved charging performance across all SOC states while maintaining high energy density.
2Ease of manufacture
If conventional graphite materials are used in the negative electrode, then the battery structure is simple and easy to manufacture, but active ion diffusion rate is insufficient leading to poor fast-charging capability
Solution Approach 1:
The patent applies parameter changes by modifying the surface properties of graphite particles through amorphous carbon coating. This changes the diffusion parameters at the particle level, enabling fast ion transport while keeping the bulk graphite structure intact and easy to manufacture.
Solution Approach 2:
The patent combines conventional artificial graphite with amorphous carbon coating to create a composite material that maintains the ease of manufacturing graphite while adding the fast diffusion characteristics of amorphous carbon at the surface level.
3Quantity of substance
If the negative electrode is designed for high capacity, then energy density is improved, but polarization increases during fast charging
Solution Approach 1:
The patent applies local quality by addressing the polarization problem at the particle surface level through amorphous carbon coating. This localized modification reduces concentration polarization at the electrode-electrolyte interface while maintaining the high capacity bulk graphite structure.
Solution Approach 2:
The amorphous carbon coating creates a porous-like structure at the particle surface that facilitates electrolyte penetration and ion diffusion, reducing concentration polarization while maintaining high capacity.
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 proposed negative-electrode active material significantly improves the fast-charging capability and cycling performance of secondary batteries by maintaining high active ion diffusion rates even in high lithium intercalation states, thus reducing ohmic and concentration polarization.
Implementation Method 1
active ions can have a relatively high diffusion rate in the negative-electrode plate
Implementation Method 2
repeated intercalation and deintercalation of active ions between a positive electrode and a negative electrode
Data Source
AI summary
This application discloses a negative-electrode active material and a preparation method thereof, a secondary battery, and a battery module, a battery pack, and an apparatus that include such secondary battery. The negative-electrode active material includes a core and a coating layer covering at least part of a surface of the core, where the core includes artificial graphite, the coating layer includes amorphous carbon, a volume-based particle size distribution of the negative-electrode active material satisfies Dv99≤24 μm, a volume-based median particle size Dv50 of the negative-electrode active material satisfies 8 μm≤Dv50≤15 μm, Dv99 is a particle size corresponding to a cumulative volume distribution percentage of the negative-electrode active material reaching 99%, and Dv50 is a particle size corresponding to a cumulative volume distribution percentage of the negative-electrode active material reaching 50%.