Graphite Electrode Alignment via Magnetic Field and Freeze Sublimation
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Solution Overview
Problem
Existing methods for forming aligned graphite electrodes for lithium-ion batteries face challenges such as reduced alignment degree due to residual iron oxide, inefficient charge/discharge, and the need for low-boiling-point solvents, which limit the use of conventional binders and increase temperature, affecting ion transport and battery performance.
Innovation Solution
A method involving coating a graphite composition with a binder and solvent on a substrate, applying a magnetic field for alignment, freezing, and subliming the solvent to fix the alignment, using solvents like water or N-methyl pyrrolidone, and omitting iron oxide to enhance graphite alignment and battery performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If iron oxide nanoparticles are assembled with graphite to control graphite with a magnetic field, then graphite alignment is achieved, but residual iron oxide remains on graphite requiring additional removal processes that lower charge/discharge efficiency
Solution Approach 1:
The patent removes iron oxide nanoparticles from the system entirely, using only graphite particles that are directly alignable by magnetic fields. This eliminates the need for acid-treating processes while maintaining effective graphite alignment, thereby preserving charge/discharge efficiency.
Solution Approach 2:
The patent introduces a magnetic field as an intermediary to directly align graphite particles without requiring iron oxide as a magnetic mediator. This direct alignment approach eliminates residual iron oxide while achieving the desired graphite orientation.
2Loss of time
If drying process is performed immediately after aligning graphite with magnetic field, then solvent removal is achieved, but alignment degree decreases when magnetic field is removed
Solution Approach 1:
The patent applies magnetic field alignment before the drying process begins, ensuring graphite particles are pre-aligned while the slurry is still in a state that maintains alignment. The alignment is then preserved through the drying process, eliminating the need for post-drying realignment.
Solution Approach 2:
The patent controls the magnetic field strength and applies it during the entire drying process, maintaining optimal alignment conditions throughout solvent removal. This parameter control ensures alignment degree is preserved despite the changing physical state during drying.
3Productivity
If drying process is performed simultaneously with aligning process, then process time is reduced, but magnetic field is lowered by temperature increase reducing alignment degree
Solution Approach 1:
The patent dynamically adjusts the magnetic field strength in response to temperature changes during simultaneous drying and aligning. As temperature increases and may reduce magnetic field effectiveness, the system compensates by adjusting field strength to maintain optimal alignment conditions throughout the process.
4Temperature
If solvent with low sublimation point like ethanol is used for simultaneous magnetic field application and drying, then drying is facilitated, but conventional binders and solvents cannot be used
Solution Approach 1:
The patent changes the sublimation temperature parameter by selecting solvents with appropriate sublimation points that allow simultaneous drying and aligning at temperatures compatible with conventional binders. This enables the use of standard binder materials while maintaining process efficiency.
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
This method effectively increases the alignment degree of graphite, prevents alignment loss during solvent removal, allows use of conventional binders, and improves battery performance by maintaining magnetism and avoiding iron oxide-related performance decreases.
Implementation Method 1
applying a magnetic field to the graphite composition coated on the substrate to align the graphite particle
Implementation Method 2
subliming the frozen solvent of the graphite composition to remove the frozen solvent
Data Source
AI summary
A disclosed method for forming aligned structure of graphite includes coating a graphite composition including a graphite particle, a binder and a solvent on a substrate, applying a magnetic field to the graphite composition coated on the substrate to align the graphite particle, freezing the graphite composition including the aligned graphite particle, and subliming the frozen solvent of the graphite composition to remove the frozen solvent.