Expanded Natural Graphite Negative Electrode Pre-Lithiation
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Solution Overview
Problem
Existing methods for preparing negative electrodes using expanded natural graphite suffer from low initial efficiency and poor life characteristics due to high irreversible capacity and lithium ion diffusion resistance caused by large spacing between crystal lattice planes.
Innovation Solution
A method involving impregnating a negative electrode structure with a pre-lithiation solution and electrochemically charging it to 10% to 20% of its charge capacity to compensate for irreversible capacity and improve lithium ion diffusion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If expanded natural graphite is used as negative electrode active material to increase spacing between crystal lattice planes, then output characteristics are improved, but initial efficiency decreases and life characteristics deteriorate due to increased irreversible capacity
Solution Approach 1:
The patent applies preliminary action by pre-lithiating the expanded natural graphite negative electrode before actual battery operation. This is achieved by contacting the negative electrode with a lithium-containing solution or performing electrochemical charging in advance, which compensates for the irreversible capacity loss that would otherwise occur during the first charge-discharge cycle. This preliminary lithiation ensures that lithium ions are already present in the graphite structure, eliminating the initial efficiency loss and improving life characteristics while maintaining the excellent output characteristics provided by the expanded crystal lattice spacing.
2Speed
If expanded natural graphite with large spacing between crystal lattice planes is used, then lithium ion diffusion is facilitated, but irreversible capacity increases leading to poor life characteristics
Solution Approach 1:
The patent applies preliminary action by performing pre-lithiation treatment on the expanded natural graphite before battery assembly or initial operation. This involves contacting the graphite with lithium-containing solutions or conducting electrochemical charging in advance, which pre-compensates for the irreversible capacity that would be lost during the first operational cycle. By doing this preliminary action, the large spacing between crystal lattice planes continues to facilitate rapid lithium ion diffusion, while the pre-added lithium compensates for the irreversible loss, thereby improving life characteristics.
3Quantity of substance
If expanded natural graphite is used to maximize output characteristics, then capacity is increased, but initial efficiency becomes very low due to high irreversible capacity
Solution Approach 1:
The patent applies preliminary action by implementing pre-lithiation of the expanded natural graphite negative electrode before the battery enters normal operation. This is accomplished by exposing the graphite to lithium-containing solutions or performing electrochemical charging in advance, which adds lithium ions to the structure beforehand. This preliminary action compensates for the irreversible capacity that would otherwise be lost during the first charge-discharge cycle, thereby significantly improving initial efficiency while maintaining the high capacity provided by the expanded graphite structure.
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 method enhances initial efficiency and life characteristics of expanded natural graphite-based electrodes by reducing irreversible capacity and lithium ion diffusion resistance, resulting in improved output characteristics.
Implementation Method 1
impregnating the negative electrode structure with a pre-lithiation solution to form an impregnated negative electrode structure
Implementation Method 2
pre-lithiating the impregnated negative electrode structure by electrochemically charging the impregnated negative electrode structure
Data Source
AI summary
A method of preparing a negative electrode which includes preparing a negative electrode structure including expanded natural graphite, impregnating the negative electrode structure with a pre-lithiation solution to form an impregnated negative electrode structure, and pre-lithiating the impregnated negative electrode structure by electrochemically charging the impregnated negative electrode structure to 10% to 20% of charge capacity of the negative electrode structure.