Composite Graphite Particles for Battery Electrodes
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Solution Overview
Problem
Nonaqueous secondary batteries face challenges with high charge/discharge irreversible capacity and poor high-load characteristics due to poor electrolyte infiltration and lithium ion migration issues caused by densification of the active-material layer in existing graphite-based electrodes.
Innovation Solution
The use of composite graphite particles comprising spherical graphite and a graphitized binder, with specific structural and surface properties, such as exposed surfaces, imperfect laminate structures, and controlled porosity, to enhance electrolyte infiltration and lithium ion migration, resulting in a negative electrode with improved charge/discharge characteristics.
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 charge/discharge irreversible capacity increases and high-load characteristics deteriorate
Solution Approach 1:
The patent utilizes graphite particles with a specific porous structure that maintains internal void spaces even when the active-material layer is densified. These pores allow electrolyte penetration and lithium ion migration while maintaining high capacity, resolving the contradiction between density and ion transport.
Solution Approach 2:
The invention applies different structural characteristics to different regions of the graphite particles - the outer shell provides structural integrity for densification while the inner porous structure maintains electrolyte access and ion migration pathways, allowing local optimization of both capacity and ion transport properties.
2Quantity of substance
If the active-material layer is densified to increase capacity, then the battery capacity increases, but the high-load characteristics decrease
Solution Approach 1:
The porous structure within the graphite particles maintains electrolyte infiltration channels even under densified conditions, ensuring smooth lithium ion migration during high-rate charge/discharge operations, thus preserving high-load characteristics while achieving high capacity.
Solution Approach 2:
The patent employs spherical graphite particles with controlled surface morphology that reduce stress concentration and improve electrolyte distribution during densification, enabling better high-rate performance compared to flaky or irregular-shaped particles.
3Ease of manufacture
If flaky or scale-like natural graphite is used, then the material is readily available, but the densification of the active-material layer is insufficient and charge/discharge irreversible capacity remains high
Solution Approach 1:
The patent transforms flaky or scale-like natural graphite into spherical particles with controlled surface morphology and internal porous structure. This spherical transformation improves packing density and creates optimal pathways for electrolyte infiltration and ion migration, reducing irreversible capacity while maintaining ease of manufacture from natural graphite feedstock.
Solution Approach 2:
The invention changes key parameters of the natural graphite including particle shape (from flaky to spherical), surface area, and internal pore structure through controlled processing. These parameter changes enable better densification and lower irreversible capacity while still using abundant natural graphite as the starting material.
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 composite graphite particles achieve a low charge/discharge irreversible capacity and excellent high-load characteristics by ensuring efficient electrolyte infiltration and smooth lithium ion migration, even when the active-material layer is densified, thereby enhancing the performance of nonaqueous secondary batteries.
Implementation Method 1
smooth lithium ion migration
Implementation Method 2
electrolytic-solution infiltration
Data Source
AI summary
A subject is to provide a nonaqueous secondary battery which is sufficiently low in charge/discharge irreversible capacity in initial cycling even when an active-material layer comprising a negative-electrode material and formed on a current collector is densified for capacity increase where the subject is accomplished with composite graphite particles for a nonaqueous secondary battery which comprise a composite of spherical graphite particles and a binder graphite and which satisfy at least one of (a) to (g) conditions as presently claimed and a negative electrode produced using the carbonaceous negative-electrode material according to the invention is excellent in electrolytic-solution infiltration and provides a nonaqueous secondary battery having excellent charge/discharge high-load characteristics.