Graphite Negative Electrode Dual Carbon Coating for Battery Performance
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Solution Overview
Problem
Current methods for improving secondary battery charging performance and high-temperature storage using graphite-based negative electrode active materials often compromise either rapid charging or high-temperature storage performance due to excessive specific surface area and inadequate lithium ion de-intercalation suppression.
Innovation Solution
A method involving the formation of a first carbon coating layer on graphite using pitch followed by a second carbon coating layer from a liquid resin, optimizing the specific surface area and interface to enhance both rapid charging and high-temperature storage capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the surface of graphite is coated with hard carbon to improve rapid charging performance, then the charging speed is improved, but the specific surface area is excessively increased which hinders lithium ion de-intercalation suppression and deteriorates high-temperature storage performance
Solution Approach 1:
The patent divides the coating into two distinct layers: a first carbon coating layer (5-20 nm thick) and a second hard carbon coating layer (20-50 nm thick). This segmentation allows the first layer to control specific surface area and prevent lithium ion de-intercalation, while the second layer provides rapid charging performance, thus resolving the contradiction between charging speed and storage stability.
Solution Approach 2:
The patent applies different coating materials and thicknesses at different locations/layers to achieve different functions. The inner first carbon coating layer has specific properties for surface area control and ion de-intercalation prevention, while the outer second hard carbon layer has properties optimized for rapid charging. This local differentiation resolves the contradiction by assigning different qualities to different parts of the coating system.
2Ease of manufacture
If a single carbon coating layer is applied to graphite, then the manufacturing process is simple, but it cannot simultaneously satisfy both rapid charging performance and high-temperature storage performance
Solution Approach 1:
The patent segments the coating process into two sequential steps: first forming a carbon coating layer, then forming a hard carbon coating layer. While this adds a step to the manufacturing process, each step uses standard coating techniques, and the segmentation enables the system to achieve dual performance capabilities that a single layer cannot provide, thus trading some manufacturing complexity for enhanced adaptability.
Solution Approach 2:
The patent uses composite coating structure combining two different carbon-based materials with distinct properties. The first carbon coating layer and second hard carbon coating layer form a composite system where each material contributes its unique properties, enabling the overall structure to satisfy both rapid charging and high-temperature storage requirements simultaneously.
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 approach maintains a proper specific surface area for improved rapid charging performance while effectively suppressing lithium ion de-intercalation for enhanced high-temperature storage, balancing both performance metrics.
Implementation Method 1
disposing a pitch on graphite particles and performing a first heat treatment on the graphite particles to form a first carbon coating layer
Implementation Method 2
disposing a liquid resin on the first carbon coating layer and performing a second heat treatment on the graphite particles to form a second carbon coating layer
Data Source
AI summary
A method for preparing a negative electrode active material. The method includes disposing a pitch on graphite particles and performing a first heat treatment on the graphite particles to form a first carbon coating layer, and disposing a liquid resin on the first carbon coating layer and performing a second heat treatment on the graphite particles to form a second carbon coating layer.