Graphite Orientation in Lithium-Ion Negative Electrodes
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Solution Overview
Problem
In lithium-ion secondary cells, the random arrangement of graphite layers relative to the current collector leads to electrolyte component loss during discharge, increasing internal resistance due to shrinkage and electrolyte flow along the winding axis direction.
Innovation Solution
Aligning at least 50 mass % of the graphite material's (002) plane perpendicular to the current collector surface and parallel to its longitudinal direction using a magnetic field during the manufacturing process, preventing electrolyte loss and reducing internal resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If graphite layers are arranged perpendicular to the current collector surface, then electrolyte component loss is prevented and internal resistance is suppressed, but manufacturing complexity increases due to the need for magnetic field application
Solution Approach 1:
A magnetic field is introduced as an intermediary during the coating process to control the orientation of graphite particles. The magnetic field acts as a mediator that aligns the graphite (002) planes perpendicular to the current collector surface without requiring mechanical intervention or post-processing steps, thus resolving the contradiction between improved reliability and manufacturing complexity
Solution Approach 2:
The invention changes the physical state and orientation parameters of graphite particles during the coating process by applying a magnetic field. This parameter change enables the graphite layers to be arranged perpendicular to the current collector surface, preventing electrolyte loss and suppressing internal resistance increase while maintaining a relatively simple manufacturing process
2Ease of manufacture
If graphite layers are arranged randomly on the current collector, then manufacturing is simpler, but electrolyte component flows along the winding axis during discharge causing increased internal resistance
Solution Approach 1:
The magnetic field serves as an intermediary during the coating process to control graphite particle orientation. It enables alignment perpendicular to the current collector surface without complicating the manufacturing process, thus resolving the contradiction between ease of manufacture and electrolyte retention
Solution Approach 2:
The magnetic field is applied during the coating process to preliminarily establish the correct orientation of graphite particles before the electrode is wound and used. This preliminary action ensures that electrolyte component flow is prevented from the outset, maintaining both manufacturing simplicity and electrolyte retention
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 alignment effectively prevents electrolyte loss and suppresses the increase in internal resistance, enhancing the performance of lithium-ion secondary cells, particularly suitable for use as power supplies in vehicles.
Implementation Method 1
applying a magnetic field to a composition... arranging layers of graphite so as to be perpendicular to a current collector by applying a magnetic field to a composition
Data Source
AI summary
The cell has a wound electrode assembly 50 including a positive electrode 64 and a negative electrode 84 that are wound with a separator 90 interposed therebetween, and a liquid electrolyte, wherein the negative electrode includes an elongated negative electrode current collector 82, and a negative electrode mixture layer 88 that is formed on the negative electrode current collector and contains at least a graphite material 85. The graphite material in the negative electrode mixture layer is arranged such that the (002) plane 85A of at least 50 mass % of the graphite material is perpendicular to the surface of the negative electrode current collector and parallel to the longitudinal direction of the elongated negative electrode current collector.