Alkali-Treated Carbon Anodes for Stable SEI and Higher Coulombic Efficiency
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Solution Overview
Problem
Existing negative electrode active materials in secondary batteries face challenges in achieving high initial coulombic efficiency and long cycling performance, leading to reduced energy density and limited application range, particularly in electric vehicles and energy storage, despite current methods like selecting single particle types and surface coating with amorphous carbon causing energy loss.
Innovation Solution
A carbon-based negative electrode active material with an alkali metal element, such as sodium or potassium, is treated to form an organic substance layer resembling an SEI film, enhancing the quality of the SEI film and improving electrochemical stability, thereby reducing active lithium ion loss and side reactions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the particle surface is coated with amorphous carbon to improve cycling performance, then cycling performance is improved, but energy density is reduced
Solution Approach 1:
The patent applies local quality by introducing alkali metal elements specifically at the particle surface region rather than uniformly throughout the material. This localized modification creates an organic substance layer only where needed for SEI film quality improvement, preserving the bulk material's high carbon content and energy density while achieving the desired surface properties for enhanced cycling performance.
Solution Approach 2:
The patent changes the chemical composition parameter at the particle surface by introducing alkali metal elements (sodium and/or potassium). This parameter change transforms the surface properties to form a stable organic substance layer that improves SEI film quality, thereby enhancing cycling performance without requiring amorphous carbon coating that would reduce energy density.
2Reliability
If conventional surface coating methods are used to improve initial coulombic efficiency, then initial coulombic efficiency is improved, but energy density is reduced
Solution Approach 1:
The patent applies local quality by introducing alkali metal elements specifically at the particle surface region rather than uniformly throughout the material. This localized modification creates an organic substance layer only where needed for SEI film quality improvement, preserving the bulk material's high carbon content and energy density while achieving the desired surface properties for enhanced cycling performance.
Solution Approach 2:
The patent changes the chemical composition parameter at the particle surface by introducing alkali metal elements (sodium and/or potassium). This parameter change transforms the surface properties to form a stable organic substance layer that improves SEI film quality, thereby enhancing cycling performance without requiring amorphous carbon coating that would reduce energy density.
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 results in improved initial coulombic efficiency and cycling performance of secondary batteries, with specific parameters like mass loss ratio, exothermic peak temperature, and atomic percentage of alkali metals optimizing the SEI film formation and stability.
Implementation Method 1
the organic substance on the particle surface can inhibit the formation of film on the negative electrode active material, which reduces the loss of active lithium ions and improves the initial coulombic efficiency
Implementation Method 2
element sodium and/or element potassium on the particle surface can improve the electrochemical stability of the organic substance, so as to avoid side reactions or even decomposition of the organic substance
Implementation Method 3
under thermogravimetric test, in a temperature range of 25° C. to 800° C., a mass loss ratio of the carbon-based material is denoted as S, where S≥0.5%, and an exothermic peak value of the carbon-based material is denoted as T, where 300° C.≤T≤500° C.
Data Source
AI summary
A negative electrode active material includes a carbon-based material, where particle surface of the carbon-based material includes an alkali metal element, and the alkali metal element includes element sodium and/or element potassium. The surface of carbon-based material such as a graphite material is treated to obtain an organic substance layer similar to an SEI film on the particle surface, which can effectively improve the quality of the SEI film, thereby improving the initial coulombic efficiency and cycling performance of the secondary battery.