Spherical Graphite with Carbon Coating for Battery Capacity
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Solution Overview
Problem
Lithium ion rechargeable batteries face challenges in achieving high capacity, low capacity loss, and excellent charge/discharge repeatability due to limitations in negative electrode materials, particularly with vein and flake natural graphite, which has poor orientation and cycle characteristics when used in high-density electrodes.
Innovation Solution
Graphite particles are produced by rendering vein and flake natural graphite spherical and coating them with a mixture of pitch and carbon black, followed by heat treatment, resulting in particles with fine protrusions that enhance electrical conductivity and stability, suitable for use as negative electrode materials in lithium ion batteries.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If vein and flake natural graphite is used as negative electrode material to achieve high capacity, then the discharge capacity is improved, but the cycle characteristics and charge/discharge repeatability deteriorate due to poor particle orientation
Solution Approach 1:
The patent applies spheroidality by transforming vein and flake natural graphite into spherical particles through mechanical treatment. This spherical shape improves particle orientation and distribution in the electrode, enhancing both cycle characteristics and charge/discharge repeatability while maintaining high discharge capacity. The spherical morphology allows for better packing density and more uniform current distribution throughout the electrode.
2Reliability
If graphite particles are spheroidized to improve charge/discharge repeatability, then the cycle characteristics are improved, but the electrical conductivity may deteriorate due to reduced contact points between particles
Solution Approach 1:
The patent applies composite materials by coating spherical graphite particles with conductive carbon materials such as acetylene black or furnace black. This composite structure maintains the spherical shape for good cycle characteristics while the conductive carbon coating restores and enhances electrical conductivity by providing additional conductive pathways between particles and improving electron transport at particle interfaces.
3Quantity of substance
If high-density electrode is constructed to increase battery capacity, then the energy density is improved, but the capacity loss increases due to poor particle orientation and reduced electrolyte access
Solution Approach 1:
The patent applies spheroidality by using spherical graphite particles that provide consistent orientation and spacing throughout the high-density electrode structure. This spherical morphology ensures uniform electrolyte distribution and access to all active material particles, preventing capacity loss even at high electrode densities. The spherical shape also facilitates better mechanical stability during charge/discharge cycling.
Solution Approach 2:
The patent applies composite materials by incorporating conductive carbon coatings on spherical graphite particles, which maintains electrical conductivity and facilitates electron transport in high-density electrodes. This composite structure ensures that even when particles are closely packed, the conductive network remains intact, reducing polarization and capacity loss during high-rate operation.
4Quantity of substance
If conventional graphite coating methods are used to improve surface properties, then the discharge capacity is improved, but the manufacturing complexity and cost increase due to multiple processing steps
Solution Approach 1:
The patent applies merging by combining the spheroidization process and carbon coating into a single integrated thermal treatment step. The spherical graphite particles are mixed with conductive carbon materials and subjected to thermal treatment at 900-1500°C, which simultaneously spheroidizes the particles and deposits the carbon coating. This merged process eliminates separate mechanical grinding and coating steps, reducing manufacturing complexity while achieving both improved discharge capacity and electrical conductivity.
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 treated graphite particles demonstrate improved discharge capacity, reduced capacity loss, and excellent rapid charge/discharge and power characteristics, making them suitable for high-energy density applications in batteries for portable devices and electric vehicles.
Implementation Method 1
heating the agglomerates in a range of 900 to 1400° C. in an inert atmosphere
Implementation Method 2
followed by heat treatment, resulting in particles with fine protrusions
Data Source
AI summary
A negative electrode active material for a lithium ion secondary battery, made up of substantially spherical graphite particles (A), having fine protrusions on the surfaces thereof and obtained by impregnating and coating substantially spherical graphite particles with a mixture of pitch and carbon black, followed by baking in a range of 900 to 1500° C. In accordance with Raman spectroscopic analysis of the particles (A) using argon laser Raman scattering light, there exists a G-band composite peak comprising peaks in the vicinity of 1600 cm−1, and 1580 cm−1, respectively, and at least one peak in the vicinity of D-band at 1380 cm−1, an interlayer distance of the lattice plane d002, obtained by wide-range X-ray diffraction, being in the range of 0.335 to 0.337 nm.