Spherical Natural Graphite Packing for Low-Swelling Li-Ion Anodes
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Solution Overview
Problem
Lithium-ion secondary batteries face issues with battery swelling due to the destruction and deformation of active material layers during densification, leading to increased irreversible charge/discharge capacity, decreased high-current charging/discharging characteristics, and deteriorated cycle characteristics.
Innovation Solution
A carbon material composed of natural graphite with specific particle size distributions and tap density, where the volume-average particle size (d50) and the ratio of d90 to d10 satisfy certain formulas, is used to produce a spherical carbon material that reduces battery swelling by allowing small particles to fill gaps between larger ones, creating a dense and conductive path.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the active material layer is densified to increase capacity, then the battery capacity increases, but the material undergoes destruction and deformation leading to increased irreversible charge/discharge capacity
Solution Approach 1:
The patent applies spheroidization treatment to convert flake-like graphite particles into spherical particles. This curvature change reduces stress concentration during lithiation/delithiation cycles, preventing particle destruction and deformation. The spherical shape allows more uniform volume expansion and contraction, maintaining structural integrity while achieving high capacity through densification.
Solution Approach 2:
The patent changes the particle size distribution parameters by controlling the ratio d90/d10 to be 1.6 or more. This parameter change creates a specific size distribution where small particles fill gaps between larger particles, achieving high tap density (0.45 g/cm³ or more) while maintaining particle integrity and reducing irreversible capacity loss.
2Quantity of substance
If the active material layer is densified to increase capacity, then the battery capacity increases, but the large current charge/discharge characteristics decrease
Solution Approach 1:
Spherical particles provide more uniform current distribution across the particle surface compared to flake-like particles. This uniformity reduces local current density hotspots, enabling efficient lithium ion transport even at high current densities, thus maintaining good large current charge/discharge characteristics while achieving high capacity.
Solution Approach 2:
By controlling the particle size distribution (d90/d10 ≥ 1.6) and tap density (≥ 0.45 g/cm³), the patent creates an optimized structure where small particles fill interstitial spaces, providing additional lithium ion insertion sites and maintaining short diffusion paths, which supports high-rate charge/discharge performance.
3Quantity of substance
If the active material layer is densified to increase capacity, then the battery capacity increases, but the cycle characteristics deteriorate
Solution Approach 1:
The spherical particle morphology reduces mechanical stress concentration during repeated expansion and contraction cycles. This uniform stress distribution prevents particle cracking and structural degradation, maintaining excellent cycle characteristics over extended battery operation while achieving high initial capacity through densification.
4Ease of manufacture
If flake-like graphite particles are used, then the material is readily available, but battery swelling occurs
Solution Approach 1:
The patent transforms readily available flake-like graphite into spherical particles through spheroidization treatment. This shape transformation eliminates the layering and anisotropic expansion issues inherent in flake structures, preventing battery swelling while maintaining the ease of manufacture advantage by using natural graphite as the starting material.
5Volume of stationary object
If the particle size distribution is optimized to increase density, then the tap density increases, but the manufacturing complexity increases
Solution Approach 1:
The patent defines a specific particle size distribution criterion (d90/d10 ≥ 1.6) that naturally achieves high tap density (≥ 0.45 g/cm³) through simple spherical particle formation. This parameter-based approach simplifies quality control and manufacturing processes compared to complex multi-step classification methods, as the spheroidization process itself produces the desired size distribution.
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 use of this carbon material suppresses battery swelling, maintaining high current density charge/discharge characteristics and extending the battery's life by ensuring a dense and efficient electrode structure.
Implementation Method 1
small particles fit into the interparticle gaps relatively large particles, making it possible to granulate dense particles
Data Source
AI summary
A carbon material comprising natural graphite, wherein the carbon material satisfies the following formulas (1) and (2),y≥0.23x+3.1 (1)z≥0.43 (2)wherein x is d50 (μm) of the carbon material, y is d90/d10 of the carbon material, and z is the tap density (g/cm3).