Carbon Negative Electrode Surface Chemistry for Stable SEI Films
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Solution Overview
Problem
Existing methods to improve cycling performance of secondary batteries, such as reducing particle size and applying amorphous carbon on the active substance, lead to a loss of energy density and efficiency, and the SEI film quality is not adequately addressed.
Innovation Solution
A carbon-based negative electrode active material with controlled amounts of sodium and oxygen on its surface, within specific atomic percentages, to enhance the quality of the SEI film, thereby improving cycling performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the particle size of active substance is reduced to improve cycling performance, then cycling performance is improved, but energy density is reduced
Solution Approach 1:
The patent applies local quality by creating a differentiated structure where the surface of carbon particles contains specific elements (sodium and oxygen) with controlled atomic percentages, while the interior maintains high carbon content. This localized compositional variation allows small particles to form stable SEI films on their surfaces without sacrificing the energy density that would result from excessive particle size reduction.
Solution Approach 2:
The patent employs composite materials by combining carbon-based active substance with sodium and oxygen elements on its surface, creating a composite structure that forms a stable SEI film. This composite approach allows the material to benefit from both the high capacity of carbon and the film-stabilizing properties of sodium and oxygen, resolving the contradiction between cycling performance and energy density.
2Reliability
If amorphous carbon is applied on the surface of active substance to improve cycling performance, then cycling performance is improved, but energy density and efficiency are reduced
Solution Approach 1:
The patent applies parameter changes by precisely controlling the atomic percentages of sodium (0.1-5.0 at%) and oxygen (0.1-10.0 at%) on the carbon particle surface, along with their ratio (0.5-5.0). This quantitative control creates an optimal SEI film composition that improves cycling performance without the excessive carbon coating that would reduce energy density.
Solution Approach 2:
The patent uses partial action by applying only the necessary amount of sodium and oxygen elements on the carbon surface to form a functional SEI film, rather than applying excessive amorphous carbon coating. This partial approach achieves the required protection and stability while minimizing the loss of energy density.
3Reliability
If element oxygen is increased to improve SEI film formation, then SEI film formation is improved, but side reactions increase which affects storage and cycling performance
Solution Approach 1:
The patent controls oxygen atomic percentage within 0.1-10.0 at% to optimize SEI film formation while minimizing side reactions. This controlled oxygen content ensures sufficient film formation without excessive oxidation that would harm storage and cycling performance.
4Reliability
If both element sodium and element oxygen are controlled within specific ranges, then SEI film quality and thermal stability are improved, but manufacturing precision requirements increase
Solution Approach 1:
The patent establishes specific parameter ranges (sodium: 0.1-5.0 at%, oxygen: 0.1-10.0 at%, ratio: 0.5-5.0) that define the optimal SEI film composition. These quantified parameters provide clear manufacturing targets and acceptance criteria, making it easier to control the process despite the increased precision requirements.
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 controlled amounts of sodium and oxygen on the carbon-based material improve the thermal stability and reduce side reactions, leading to enhanced cycling performance and storage performance of the secondary battery.
Implementation Method 1
the element sodium and the element oxygen are constituent elements of an SEI film and affect thermal stability of the SEI film on the surfaces of particles
Implementation Method 2
Element oxygen is an essential constituent of the SEI film
Data Source
AI summary
A negative electrode active material. The negative electrode active material includes a carbon-based material, where a surface of the carbon-based material includes element sodium and element oxygen. An atomic percentage of the element sodium is X, and an atomic percentage of the element oxygen is Y, where Y/X≥3.0. X and Y are obtained through testing using an X-ray energy dispersive spectrometer. In this application, amounts of element sodium and element oxygen on the surface of the carbon-based material are controlled to be within given ranges, so that quality of SEI films can be effectively improved, thereby allowing a secondary battery to have excellent cycling performance.