Amorphous Carbon Negative Electrode for Battery Safety
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Solution Overview
Problem
Lithium secondary batteries face safety issues due to rapid exothermic reactions and internal short circuits, particularly when subjected to overcharge or high temperatures, which can lead to explosions, and existing negative electrode materials have limitations in capacity and reversibility.
Innovation Solution
An amorphous carbonaceous material with a doping element is used as the negative electrode active material, exhibiting multiple peaks of derivative weight change and controlled exothermic peak output in thermogravimetric analysis and differential scanning calorimetry, dispersing heat generation and preventing internal short circuits and explosions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If lithium metal is used as negative electrode material to increase capacity, then energy density is improved, but reversibility deteriorates and dendrite formation causes safety issues
Solution Approach 1:
An amorphous carbon layer is introduced as an intermediary between the lithium metal negative electrode and the electrolyte. This carbon layer prevents direct contact between lithium and electrolyte, eliminating dendrite formation and improving reversibility while maintaining high capacity. The carbon acts as a protective mediator that enables safe operation at high temperatures and during overcharge conditions.
Solution Approach 2:
The invention changes the physical and chemical parameters of the negative electrode by using amorphous carbon with specific properties (disordered structure, controlled conductivity) instead of crystalline carbon or pure lithium. This parameter change allows the system to achieve both high energy density and improved safety/reversibility characteristics.
2Reliability
If graphite material is used as negative electrode active material to ensure safety, then reversibility is improved, but capacity is limited
Solution Approach 1:
The invention creates a composite negative electrode structure combining amorphous carbon with conductive additives and binding agents in specific ratios. This composite material achieves capacity exceeding the theoretical limit of graphite (372 mAh/g) by utilizing the disordered carbon structure's ability to accommodate more lithium ions while maintaining electrical conductivity and structural integrity.
Solution Approach 2:
The invention changes the crystalline structure of carbon from ordered graphite to amorphous form, fundamentally altering the capacity parameters. The amorphous structure provides additional insertion sites for lithium ions and enables higher capacity while maintaining the safety and reversibility advantages of carbon-based materials.
3Use of energy by moving object
If carbonaceous materials are used as negative electrode active material to increase capacity beyond graphite limit, then energy density is improved, but heat generation increases causing safety issues
Solution Approach 1:
The invention applies local quality control by creating a heterogeneous negative electrode composition with different carbonaceous materials distributed in specific proportions. The amorphous carbon component provides high capacity while conductive additives maintain electrical pathways and binding agents provide structural stability, locally managing heat generation throughout the electrode structure.
Solution Approach 2:
The invention converts the potentially harmful exothermic reaction characteristic of carbonaceous materials into a beneficial feature by carefully selecting and proportioning materials that exhibit controlled heat release. The specific composition transforms what could be a safety hazard into a controlled thermal profile that enhances capacity while maintaining safety margins.
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 solution effectively prevents internal short circuits and explosions by managing heat generation within the battery, ensuring safety and maintaining a high energy density, while also improving cycle characteristics and reducing the need for excessive lithium, thus enhancing the battery's lifespan and performance.
Implementation Method 1
the present invention provides a negative electrode active material for an electrode mixture, which ensures excellent safety for electrochemical cells such as secondary batteries... and exhibits at least two peaks of derivative weight change at temperatures between 450° C. and 950° C. in thermogravimetric analysis, and a maximum exothermic peak output of 20 mW to 60 mW as measured by differential scanning calorimetry
Data Source
AI summary
The present invention relates to a negative electrode active material for an electrode mixture, and to an electrochemical cell comprising the negative electrode active material, wherein the negative electrode active material comprises an amorphous carbonaceous material and a doping element, and exhibits, in the temperature range of 450° C. to 950° C., at least two peaks of derivative weight change calculated by thermogravimetric analysis, and exhibits a maximum heat peak output of 20 mW to 60 mW as measured by differential scanning calorimetry.