Lithium Battery Protective Layer for Ion Elution
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Solution Overview
Problem
Rechargeable lithium batteries face a rapid decrease in capacity and cycle-life due to the elution of transition element ions from the positive active material into the electrolyte at high temperatures, limiting the use of transition elements like manganese.
Innovation Solution
A positive electrode protective layer composed of a polymer compound linked to a borate-based anion and an ionic liquid is applied to the positive electrode and separator, preventing the elution of transition element ions by forming a polymer network that traps these ions, thereby enhancing battery performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If transition elements are used in positive active material to increase energy density, then battery capacity is improved, but transition element ions elute into electrolyte at high temperatures causing rapid capacity decrease and reduced cycle-life
Solution Approach 1:
A protective layer comprising a polymer compound and ionic liquid is introduced as an intermediary between the positive active material and the electrolyte. This protective layer prevents direct contact between transition element ions and the electrolyte, thereby eliminating the elution problem while preserving the high capacity benefits of transition elements like manganese.
Solution Approach 2:
A thin protective layer is formed on the surface of the positive electrode using a polymer compound and ionic liquid mixture. This thin film acts as a barrier that prevents ion elution while maintaining electrode functionality and allowing lithium ion transport.
2Use of energy by moving object
If transition elements like manganese are used in positive active material, then energy density is improved, but elution into electrolyte at high temperatures causes rapid capacity decrease
Solution Approach 1:
The protective layer serves as a mediator that physically separates the positive active material containing transition elements from the electrolyte. This prevents the harmful elution of transition element ions while allowing the beneficial electrochemical reactions to proceed.
Solution Approach 2:
A flexible protective film composed of polymer compound and ionic liquid is applied to the positive electrode surface. This film effectively contains transition element ions within the electrode structure, preventing their release into the electrolyte even at elevated temperatures.
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 protective layer effectively suppresses the elution of transition element ions, extending the battery's cycle-life and allowing for the broader application of transition elements such as manganese, thus improving the battery's overall performance.
Implementation Method 1
forming a polymer network that traps these ions
Implementation Method 2
suppresses the elution of transition element ions
Data Source
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AI summary
The present invention refers to a rechargeable lithium battery including a positive electrode, a negative electrode and a separator between the positive and negative electrodes. A positive electrode protective layer is formed on a surface of the positive electrode and/or on a surface of the separator. The positive electrode protective layer comprises or consists of a polymer compound and an ionic liquid including a borate-based anion. A method of manufacturing the same and a positive electrode protective layer composition useful for the manufacturing method is also provided.