Anode-Free Lithium Secondary Battery SEI Chemistry for Cycle Stability
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Solution Overview
Problem
Conventional lithium secondary batteries face challenges in achieving sufficient energy density and cycle characteristics, with anode-free batteries prone to dendritic lithium metal growth leading to short circuits and capacity degradation, and batteries with active materials being limited by volume and mass occupation.
Innovation Solution
A lithium secondary battery design featuring a negative electrode without active materials, utilizing an electrolyte solution with specific fluorine-substituted hydrocarbon compounds to form a solid electrolyte interfacial layer, which suppresses dendritic lithium growth and enhances cycle characteristics, achieving high energy density and improved safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a negative electrode active material is used, then the battery structure is stable, but the energy density is limited due to volume and mass occupation
Solution Approach 1:
The invention extracts and removes the negative electrode active material from the battery structure, using only a negative electrode current collector without traditional active materials like graphite or lithium metal. This extraction eliminates the volume and mass occupation of active materials while maintaining structural stability through the current collector alone, thereby significantly improving energy density.
2Quantity of substance
If no negative electrode active material is used, then energy density is improved, but dendritic lithium growth occurs leading to short circuits and capacity degradation
Solution Approach 1:
The invention introduces an intermediary substance - a fluorinated cyclic carbonate compound - that mediates between the negative electrode current collector and the electrolyte. This compound forms a stable solid electrolyte interphase (SEI) layer that acts as a protective intermediary, preventing direct contact between lithium ions and the current collector, thereby suppressing dendritic lithium growth while allowing ionic conduction, thus improving both reliability and cycle characteristic.
Solution Approach 2:
The invention changes the chemical composition parameters of the electrolyte by incorporating a fluorinated cyclic carbonate compound with specific molecular structure (containing CF3 groups). This parameter change in electrolyte composition leads to the formation of a stable SEI layer with different physical and chemical properties, including higher ionic conductivity and better stability, which prevents dendrite formation and improves cycle life.
3Reliability
If conventional electrolytes are used, then the battery operates normally, but insufficient SEI layer formation leads to poor cycle characteristic
Solution Approach 1:
The invention changes the chemical composition parameters of the electrolyte by incorporating a fluorinated cyclic carbonate compound with specific molecular structure (containing CF3 groups). This parameter change in electrolyte composition leads to the formation of a stable SEI layer with different physical and chemical properties, including higher ionic conductivity and better stability, which prevents dendrite formation and improves cycle life.
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 battery achieves high energy density exceeding 350 Wh/kg and excellent cycle characteristics due to the formation of a uniform solid electrolyte interfacial layer, reducing internal resistance and promoting efficient lithium precipitation and elution, thus extending battery life and safety.
Implementation Method 1
utilizing an electrolyte solution with specific fluorine-substituted hydrocarbon compounds to form a solid electrolyte interfacial layer, which suppresses dendritic lithium growth
Implementation Method 2
charge is performed by a direct precipitation of a new lithium metal on the lithium metal as the negative electrode active material
Implementation Method 3
charge/discharge is performed by the electrolysis and elution of the resulting precipitated lithium metal
Data Source
AI summary
The purpose of the present invention is to provide a lithium secondary battery having a high energy density and an excellent cycle characteristic. The present invention relates to a lithium secondary battery having a positive electrode, a separator, a negative electrode not having a negative electrode active material, and an electrolyte solution, in which the electrolyte solution contains, as a solvent, at least any one of compounds represented by Formulae (1) to (4).