Artificial Graphite Anodes for Low-Expansion Secondary Batteries
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Solution Overview
Problem
Secondary batteries experience volume expansion during cycling, leading to increased internal stress, reduced service life, and safety concerns, particularly in new energy vehicles where high energy density and safety performance are critical.
Innovation Solution
The use of artificial graphite with a specific volume average particle size and specific surface area, combined with a controlled compaction density, reduces directional selectivity during lithium intercalation, minimizing volume expansion and enhancing surface stability, thereby improving cycle life and safety performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional graphite materials are used in the negative electrode, then the battery can achieve basic charge/discharge function, but the battery experiences significant volume expansion during cycling, leading to increased internal stress and reduced service life
Solution Approach 1:
The patent applies parameter changes by precisely controlling the particle size distribution (Dv10≥6μm, Dv50≥12μm, Dv90≤25μm) and specific surface area (0.5-2.0 m²/g) of artificial graphite, as well as the compaction density (1.6-1.8 g/cm³) of the negative electrode plate. These parameter optimizations reduce volume expansion during cycling while maintaining good charge/discharge performance, thereby improving service life without sacrificing battery capacity
Solution Approach 2:
The patent uses composite materials by combining artificial graphite particles with specific physical and chemical properties in a controlled size distribution. The composite structure of graphite particles with optimized morphology and surface characteristics reduces internal stress during lithium intercalation and deintercalation, minimizing volume expansion and enhancing cycle stability
2Quantity of substance
If the negative electrode plate compaction density is increased to improve energy density, then more graphite can be packed into the battery, but the electrolyte infiltration is hindered and kinetic performance deteriorates
Solution Approach 1:
The patent applies local quality by creating a multi-scale particle size distribution where larger particles (Dv90≤25μm) provide high compaction density and energy density, while smaller particles fill interstitial spaces to maintain porosity for electrolyte infiltration. This local optimization of particle arrangement ensures both high graphite content and adequate electrolyte access, achieving a balance between energy density and kinetic performance
Solution Approach 2:
The patent utilizes porous materials by maintaining controlled porosity through optimized particle size distribution and compaction density (1.6-1.8 g/cm³). The porous structure formed by the particle arrangement allows sufficient electrolyte infiltration while accommodating high graphite content, thus improving both energy density and charge/discharge kinetics
3Speed
If smaller graphite particles are used to improve electrolyte contact and kinetic performance, then charge/discharge rate improves, but the specific surface area increases leading to more side reactions with electrolyte and reduced initial efficiency
Solution Approach 1:
The patent applies parameter changes by optimizing the specific surface area to be within 0.5-2.0 m²/g, which is a moderate range that balances kinetic performance and side reaction suppression. This parameter optimization ensures sufficient electrolyte contact for good charge/discharge rates while limiting the total surface area available for parasitic reactions, thereby maintaining high initial charge/discharge efficiency
4Loss of energy
If the artificial graphite particle size is increased to reduce specific surface area and side reactions, then initial efficiency improves, but the electrolyte infiltration is reduced and kinetic performance deteriorates
Solution Approach 1:
The patent applies segmentation by dividing the graphite particle population into different size segments with specific ranges (Dv10≥6μm, Dv50≥12μm, Dv90≤25μm). This segmentation creates a hierarchical structure where larger particles reduce overall specific surface area and side reactions, while smaller particles within the distribution maintain adequate electrolyte contact and kinetic performance, achieving a balance between initial efficiency and charge/discharge rate
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 approach significantly reduces cyclic expansion, enhances energy density, and improves the safety and kinetic performance of secondary batteries by optimizing the artificial graphite's properties within the negative electrode, leading to better electrolyte infiltration and reduced internal stress.
Implementation Method 1
during lithium intercalation
Data Source
Figure 1~3
Figure 4~6a
Figure 6b~6c
AI summary
The present application discloses a secondary battery, an apparatus including the secondary battery, artificial graphite and a preparation method thereof. The secondary battery includes a negative electrode plate, the negative electrode plate including a negative active material, wherein the negative active material comprises an artificial graphite having a volume average particle size Dv50 of 12µm to 22µm, and the artificial graphite satisfies: 12≤Dv50×SSA≤25, in which SSA is the specific surface area of the artificial graphite, in m2/g; the negative electrode plate has a compaction density of 1.6g/cm3 to 1.75g/cm3, and the negative electrode plate has an OI value of ≤15, wherein the OI value of the negative electrode plate represents a ratio C004/C110, in which C004 is the peak area of the diffraction peak of 004 crystal plane of the artificial graphite in the negative electrode plate and C110 is the peak area of the diffraction peak of 110 crystal plane of the artificial graphite in the negative electrode plate. The secondary battery provided by the present application can obtain lower cyclic expansion.