Lithium Battery Electrolyte Additive for SEI Stability
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Solution Overview
Problem
Lithium secondary batteries face issues with cycle-life characteristics and swelling at high temperatures due to irreversible side reactions between the electrolyte and electrodes, leading to reduced capacity and potential explosion risks.
Innovation Solution
Incorporating a non-aqueous organic solvent electrolyte with a lithium salt and an additive represented by Chemical Formula 1, which includes a difluorophosphite group, to form a rigid solid electrolyte interface (SEI) film and prevent oxidation decomposition, thereby enhancing ion conductivity and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional electrolyte is used in lithium secondary battery, then basic battery operation is achieved, but cycle-life characteristics deteriorate at high temperatures due to irreversible side reactions
Solution Approach 1:
The patent introduces a difluorophosphite compound as an intermediary substance that reacts with the electrolyte to form a protective SEI film. This intermediary layer acts as a mediator between the electrolyte and electrode, preventing direct harmful interactions while allowing necessary ionic transport, thereby resolving the contradiction between maintaining battery operation and preventing side reactions.
Solution Approach 2:
The difluorophosphite compound performs preliminary action by forming a stable SEI film on the electrode surface before the harmful irreversible side reactions can occur. This preliminary protective layer prevents subsequent degradation reactions, improving cycle-life characteristics by anticipating and preventing the harmful effects.
2Stability of the object's composition
If conventional electrolyte is used in lithium secondary battery, then battery operation is maintained, but swelling occurs at high temperatures due to gas generation
Solution Approach 1:
The patent converts the potentially harmful interaction between electrolyte and electrode into a beneficial process by using the difluorophosphite compound to guide the reaction toward forming a protective SEI film instead of generating harmful gas. The same reactivity that could cause swelling is redirected to create a stabilizing protective layer.
Solution Approach 2:
The difluorophosphite compound serves as an intermediary that prevents direct harmful reactions between the electrolyte and electrode that would generate gas. By mediating the interaction, it eliminates the source of swelling while maintaining necessary electrochemical function.
3Reliability
If electrolyte without additive is used, then simpler composition is achieved, but oxidation decomposition occurs reducing battery performance
Solution Approach 1:
The patent applies parameter changes by introducing a specific chemical compound (difluorophosphite) with particular molecular characteristics into the electrolyte formulation. This parameter change in composition enables the formation of a stable SEI film that resists oxidation decomposition, improving reliability despite increased compositional complexity.
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 significantly improves cycle-life characteristics and reduces gas generation at high temperatures, preventing swelling and increasing the battery's resistance to oxidation reactions, thus enhancing the overall performance and safety of lithium secondary batteries.
Implementation Method 1
Incorporating a non-aqueous organic solvent electrolyte with a lithium salt and an additive including a compound represented by Chemical Formula 1, which includes a difluorophosphite group, to form a rigid solid electrolyte interface (SEI) film and prevent oxidation decomposition
Implementation Method 2
form a rigid solid electrolyte interface (SEI) film and prevent oxidation decomposition, thereby enhancing ion conductivity and stability
Implementation Method 3
a lithium secondary battery is manufactured by using materials capable of reversibly intercalating and deintercalating lithium ions as a positive active material and a negative active material
Implementation Method 4
filling an electrolyte between the positive electrode and the negative electrode
Implementation Method 5
the impregnation of an electrolyte may be improved so that a lithium secondary battery exhibiting improved cycle-life characteristics and storage characteristics at high temperatures may be provided
Data Source
AI summary
The present invention relates to a lithium secondary battery including a positive electrode including a positive active material layer, the positive active material layer including a positive active material and a carbonaceous nanostructure; a negative electrode including a negative active material; and an electrolyte. The electrolyte includes a non-aqueous organic solvent, a lithium salt, and an additive including a compound represented by Chemical Formula 1, wherein the amount of the carbonaceous nanostructure is about 0.5 wt % or more and less than 4 wt % based on 100 wt % of the total amount of the positive active material layer.wherein, in Chemical Formula 1, A is a substituted or unsubstituted aliphatic chain or (—C2H4—O—C2H4-)n, and n is an integer from 1 to 10.