Graphite Spherical Aggregates for High Density Li-Ion Batteries
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Lithium-ion secondary batteries require a negative electrode material with high energy density and long lifetime, but existing materials face issues with electrode plate density and electrolytic solution flow path resistance due to particle deformation and orientation alignment during pressing.
Innovation Solution
A negative electrode material comprising graphite particle spherical aggregates with specific morphological characteristics, including high circularity, controlled particle size distribution, and crystallite size, which allows for increased density and maintained non-parallel orientation of graphite particles, enhancing electrolytic solution permeability and cycle characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If natural graphite with high crystallinity is used to improve capacity characteristics, then capacity per weight is improved, but internal fracture occurs due to biased expansion and contraction in the c-axis direction, deteriorating lifetime characteristics
Solution Approach 1:
The patent uses artificial graphite as a composite material that combines multiple components (graphite particles, binder, conductive agent) to achieve both high capacity and long lifetime. The artificial graphite structure allows controlled expansion and contraction that prevents internal fracture while maintaining high lithium ion capacity.
Solution Approach 2:
The patent changes the crystallinity parameter of graphite from high (natural graphite) to controlled levels (artificial graphite) to balance capacity and lifetime characteristics. By adjusting the degree of graphitization and particle structure, the material achieves reduced c-axis expansion while maintaining high capacity.
2Quantity of substance
If graphite particles are pressed to increase electrode plate density, then energy density is improved, but particle deformation and orientation alignment occur, blocking electrolytic solution flow paths and increasing resistance
Solution Approach 1:
The patent applies local quality by creating regions of different particle orientations and densities within the electrode. The pressing process is optimized to achieve high density in certain areas while maintaining flow path openness in others, resulting from the specific particle morphology and size distribution of the artificial graphite.
Solution Approach 2:
The patent utilizes spherical or near-spherical graphite particle morphology to reduce orientation alignment during pressing. The curved surfaces of spherical particles allow them to pack densely while maintaining random orientations, preventing the formation of aligned structures that would block electrolytic solution flow paths.
3Quantity of substance
If pressing pressure is applied to achieve high electrode density, then energy density is improved, but excessive crushing of particles occurs, deforming particles and aligning orientation planes, thereby blocking electrolytic solution flow paths
Solution Approach 1:
The patent applies preliminary action by pre-treating the graphite particles with specific size distribution and spherical morphology before electrode formation. This preliminary preparation allows the particles to withstand pressing forces without excessive crushing, as the spherical shape and size distribution are optimized in advance to resist deformation during the pressing process.
Data Source
AI summary
A negative electrode material for a lithium-ion secondary battery is disclosed which contains a mass of graphite particle spherical aggregates in which a plurality of flat graphite particles are aggregated. The mass of the graphite particle spherical aggregates has an average circularity, D90/D10, and a crystallite size Lc (004) within a predetermined range, and the proportion of the graphite particle spherical aggregates in which the largest flat graphite particle observed on the outermost surface has a circle equivalent diameter of 2 μm to 12 μm in graphite particle spherical aggregates having a circle equivalent diameter of 10 μm or more when observed by SEM is 80% or more.