Phosphorus Additive Electrolyte for Stable SEI Film
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Solution Overview
Problem
Lithium secondary batteries face limitations in initial capacity and power due to the reactivity of lithium ions with organic electrolytes, leading to reduced capacity and stability issues, particularly at low temperatures.
Innovation Solution
A non-aqueous electrolyte comprising an organic solvent, a lithium salt, and a phosphorus compound with specific structural features, such as an acryloyloxy group, is used to form a stable solid electrolyte interface (SEI) on the electrode, enhancing the battery's initial capacity, power characteristics, and lifetime performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If organic electrolytes are used in lithium secondary batteries to achieve higher operating voltage and energy density, then energy density is improved, but fire and explosion risks increase due to the reactivity of lithium ions with the organic electrolyte
Solution Approach 1:
The patent introduces a solid electrolyte interface (SEI) film as an intermediary layer between the lithium ions and the organic electrolyte. This film acts as a protective barrier that prevents direct contact and harmful reactions while allowing ionic conduction, thus maintaining high energy density while reducing fire and explosion risks.
Solution Approach 2:
The patent creates an inert protective environment by forming a stable SEI film on the electrode surface. This film provides an inert barrier that prevents the organic electrolyte from reacting with lithium ions, effectively creating a chemically inert interface that eliminates fire and explosion hazards while preserving the high energy density benefits of organic electrolytes.
2Reliability
If lithium ions react with organic electrolyte to form SEI film during initial charge, then stable charge and discharge is achieved, but initial capacity is reduced due to consumption of lithium ions
Solution Approach 1:
The patent performs preliminary action by intentionally forming a stable SEI film during an initial charge cycle before the battery enters normal operation. This preliminary film formation consumes a controlled amount of lithium ions to create a protective layer, after which the battery achieves stable charge and discharge cycles with minimal further capacity loss.
Solution Approach 2:
The patent optimizes the composition and concentration of the organic electrolyte to control the SEI film formation process. By adjusting electrolyte parameters such as additive concentration and solvent ratio, the patent minimizes the amount of lithium ions consumed during initial film formation while ensuring sufficient film stability for reliable operation.
3Quantity of substance
If carbon material is used as negative electrode active material to enable lithium ion intercalation, then capacity density is improved, but capacity is reduced over time due to desorption from electron transfer pathway and gas generation from solvent decomposition
Solution Approach 1:
The patent uses the SEI film as an intermediary protective layer between the carbon material and the organic electrolyte. This film prevents direct decomposition reactions between the electrolyte and carbon surface, eliminating gas generation and preventing carbon material desorption from the electron transfer pathway, thus maintaining high capacity density over extended battery lifetime.
Solution Approach 2:
The patent converts the initially harmful reaction between lithium ions and organic electrolyte into a beneficial protective mechanism. The controlled formation of SEI film during initial charge transforms what would be a capacity-reducing side reaction into a protective layer that prevents further harmful decomposition reactions, thereby extending battery lifetime while preserving capacity 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 use of this electrolyte improves initial capacity and power characteristics at both room and low temperatures, reducing internal resistance and maintaining stable charge and discharge performance, making it suitable for portable devices and electric vehicles.
Implementation Method 1
the lithium ions react with an electrolyte and carbon constituting the negative electrode active material on a surface of the negative electrode active material to form compounds such as Li2CO3, Li2O, or LiOH. These compounds form a kind of stable film (solid electrolyte interface, SEI) on the surface of the negative electrode active material.
Implementation Method 2
The film formed on the surface of the negative electrode active material may only pass the lithium ions by acting as an ion tunnel
Implementation Method 3
since the film may prevent the contact between the negative electrode active material and the electrolyte, the decomposition of the electrolyte may not occur
Data Source
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AI summary
Provided are a non-aqueous electrolyte, which includes an organic solvent, a lithium salt, and a phosphorus compound including an acryloyloxy group, and a lithium secondary battery including the non-aqueous electrolyte. Since the non-aqueous electrolyte includes the phosphorus compound to form a stable solid electrolyte interface (SEI) on an electrode during charge and discharge of the battery, initial capacity and power characteristics at room temperature and low temperature as well as lifetime characteristics of the battery may be improved.