Spheroidized Graphite Negative Electrode for Battery Paste Uniformity
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Solution Overview
Problem
Lithium ion secondary batteries using scale-shaped graphite face challenges with aggregation, leading to non-uniform paste formation and weak binding between the active material layer and the metal collector, resulting in poor charge and discharge performance and cycle properties.
Innovation Solution
Spheroidizing natural graphite grains through grinding and impact processes to create graphite powder with improved rheological properties, allowing for uniform paste formation and enhanced intercalation/deintercalation reactions, thereby improving load characteristics and cycle properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If scale-shaped graphite is used as negative electrode active material, then capacity close to theoretical capacity (372 mAh/g) can be realized, but the graphite aggregates in paste formation leading to non-uniform application and weak binding to collector
Solution Approach 1:
The patent applies spheroidizing treatment to natural graphite grains to transform their scale-shaped morphology into spherical or near-spherical shapes. This curvature change prevents aggregation during paste formation while maintaining high capacity, as spherical particles pack more uniformly and distribute binder more evenly across the electrode surface.
Solution Approach 2:
The patent changes physical parameters of graphite particles through spheroidizing treatment, including shape (from scale to sphere), surface area, and surface properties. These parameter changes improve paste rheology and uniformity while preserving the high capacity characteristic of natural graphite.
2Quantity of substance
If scale-shaped graphite is used, then high capacity is achieved, but binding between active material layer and metal collector becomes weak causing peeling issues
Solution Approach 1:
Spheroidizing the graphite grains creates spherical particles that provide better mechanical interlocking with the binder and collector compared to flat scale-shaped particles. The spherical morphology allows for more uniform stress distribution and stronger adhesion, preventing peeling during battery operation.
Solution Approach 2:
The spheroidizing treatment modifies surface area and surface properties of graphite particles, which directly affects binding strength. The transformed surface characteristics enable better wetting by binder solutions and stronger mechanical bonding to the metal collector.
3Quantity of substance
If graphite is highly filled to improve volume density, then capacity increases, but void portions are reduced preventing electrolyte permeation
Solution Approach 1:
Spherical graphite particles create more uniform and controlled void spaces between particles compared to scale-shaped particles. These voids are optimally sized and distributed to allow electrolyte permeation while maintaining high volume density and capacity.
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 spheroidized graphite powder prevents aggregation, ensures uniform paste application, and enhances peeling strength, resulting in improved charge and discharge performance and cycle retention rates in lithium ion secondary batteries.
Implementation Method 1
a spheroidizing process including the step of grinding natural graphite grains and/or applying impact thereto
Implementation Method 2
a spheroidizing process including the step of grinding natural graphite grains and/or applying impact thereto
Implementation Method 3
create graphite powder with improved rheological properties, allowing for uniform paste formation
Implementation Method 4
lithium ions are intercalated and deintercalated from various surfaces
Implementation Method 5
lithium ions are intercalated from the edge in charging and are then diffused between the AB planes
Implementation Method 6
disposing the edges parallel to the electrode surface (scale-shaped graphite being disposed perpendicular to the electrode surface) as shown in FIG. 2 using the magnetic field orientation properties of the graphite
Data Source
AI summary
A powdered graphite and a nonaqueous electrolyte secondary battery are provided. A nonaqueous electrolyte secondary battery is provided which has a highly efficient charge and discharge performance and superior cycle properties. Spheroidizing treatment is appropriately performed for natural graphite having a high capacity by grinding and/or applying impact to form a negative electrode active material, and a negative electrode active layer formed therefrom is provided on a metal electrode foil. Subsequently, the metal electrode foil is applied with a magnetic field so that the spheroidized natural graphite is oriented, followed by drying and compression molding, thereby forming a negative electrode. By the use of this negative electrode, a nonaqueous electrolyte secondary battery can be formed having superior battery properties such as the cycle properties and peeling strength.