Graphite Passivation Coating for Li-Ion First-Cycle Efficiency
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Solution Overview
Problem
Existing methods for passivating graphite in lithium-ion batteries fail to achieve high first cycle efficiency, as protective coatings are not sufficiently permeable to lithium ions, leading to poor battery performance and risk of internal short-circuits.
Innovation Solution
A method involving mixing pre-passivated anode graphite with a supplement and solvent, followed by evaporation and milling to create a passivated anode graphite particle with a controlled thickness of the supplement, ensuring high first cycle efficiency and permeability to lithium ions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If protective coatings are applied to graphite surface to prevent electrolyte decomposition, then battery safety is improved, but lithium ion permeability deteriorates
Solution Approach 1:
The patent applies different properties to different parts of the coating system: the inorganic layer provides protection while the organic layer provides permeability. This local differentiation allows the coating to simultaneously prevent electrolyte decomposition and maintain lithium ion transport.
Solution Approach 2:
The patent uses a composite coating structure combining inorganic material (such as alumina, silica, or titania) with organic material (such as polyvinylidene fluoride or carboxymethyl cellulose). This composite approach leverages the protective properties of inorganic materials and the ion-permeable properties of organic materials to resolve the contradiction between safety and productivity.
2Reliability
If thick protective coatings are applied to prevent decomposition, then protection effectiveness is improved, but first cycle efficiency deteriorates
Solution Approach 1:
The patent creates a multi-layer coating where the inorganic layer provides the protective function and the organic layer provides the permeable function. This local quality differentiation ensures that protection effectiveness is maintained while first cycle efficiency is preserved through controlled thickness and material selection.
Solution Approach 2:
The organic coating layer is designed to be porous or have a gel-like structure that allows lithium ion transport. This porosity ensures that even with a protective coating present, lithium ions can efficiently penetrate the coating during the first charge cycle, maintaining high first cycle efficiency.
3Manufacturing precision
If multiple coating layers are applied to achieve high first cycle efficiency, then passivation quality is improved, but manufacturing complexity increases
Solution Approach 1:
The patent combines the application of inorganic and organic coating layers into a single integrated process step. The slurry containing both inorganic particles and organic binder is applied in one coating operation, followed by a single drying and sintering cycle, thereby achieving high passivation quality without significantly increasing manufacturing complexity.
Solution Approach 2:
The organic binder material serves multiple functions: it acts as a coating matrix, provides ion-permeable pathways, and serves as a binder for the inorganic particles. This multi-functionality reduces the need for separate materials and processes, thereby simplifying manufacturing while maintaining high passivation quality.
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 achieves a first cycle efficiency greater than 75% with the supplement comprising less than 5 wt% by mass of the pre-passivated anode graphite, enhancing battery performance and preventing internal short-circuits.
Implementation Method 1
The solvent is then evaporated from the mixture to create a passivated anode graphite particle
Data Source
AI summary
A method of making an anode material. The method begins by mixing a pre-passivated anode graphite with a supplement and a solvent to create a mixture. The solvent is then evaporated from the mixture to create a passivated anode graphite particle.