Anode-Free Lithium Secondary Battery with Fluorinated Electrolyte
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Solution Overview
Problem
Lithium secondary batteries face challenges in achieving high energy density and cycle characteristics due to the volume occupied by negative electrode active materials and the formation of dendritic lithium metal, which can lead to short circuits and capacity degradation.
Innovation Solution
A lithium secondary battery design featuring a negative electrode without active materials, utilizing a fluorine solvent in the electrolytic solution to form a solid electrolyte interphase layer, which suppresses dendritic lithium growth and enhances cycle characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a negative electrode active material (such as carbon material or lithium metal) is used, then the battery can store lithium ions, but the volume and mass occupied by the active material reduce the energy density
Solution Approach 1:
The patent removes the negative electrode active material (carbon material or lithium metal) from the battery structure, extracting the component that occupies volume and mass without contributing to energy storage capacity. The negative electrode is reduced to only a current collector, eliminating the trade-off between active material volume and energy density.
2Quantity of substance
If lithium metal is used as negative electrode active material, then high energy density is achieved, but dendritic lithium metal forms during charge-discharge cycles causing short circuits and capacity degradation
Solution Approach 1:
The patent extracts lithium metal from the negative electrode structure, eliminating it as a stored component. Instead, lithium ions are temporarily deposited during charging but are not retained in metallic form. This removes the source of dendrite formation while preserving the ability to utilize lithium ions for charge storage, thereby improving cycle characteristics without sacrificing energy density.
Solution Approach 2:
The patent introduces a separator as an intermediary component between the positive and negative electrodes. This separator prevents direct contact between lithium ions and the negative electrode current collector, mediating the charge-discharge process to avoid dendrite formation while still allowing ionic transport. The separator acts as a physical barrier that eliminates the reliability issues associated with lithium metal deposition.
3Reliability
If physical pressure is applied to keep the negative electrode-separator interface under high pressure, then uneven growth is suppressed, but the weight and volume of the battery increase
Solution Approach 1:
The patent removes the need for mechanical pressure application mechanisms by extracting the negative electrode active material. Without lithium metal or carbon material in the negative electrode, there is no uneven growth to suppress, eliminating the requirement for heavy pressure application systems and their associated weight and volume.
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 and excellent cycle characteristics by reducing the volume and mass of negative electrode active materials and preventing dendritic lithium growth, leading to improved safety and productivity.
Implementation Method 1
utilizing a fluorine solvent in the electrolytic solution to form a solid electrolyte interphase layer, which suppresses dendritic lithium growth
Implementation Method 2
lithium secondary batteries that charge and discharge by transferring lithium ions between a positive electrode and a negative electrode
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 provides a lithium secondary battery including: a positive electrode; a separator; a negative electrode that is free of a negative electrode active material; and an electrolytic solution, in which the electrolytic solution contains a fluorine solvent represented by Chemical Formulae (1) to (4).(In the formulae, each of R10 and R20 independently represents any of a C1 to C8 alkyl group, a cycloalkyl group, an aryl group, a C1 to C8 alkyl group that is fully or partially fluorinated, a cycloalkyl group that is fully or partially fluorinated, or an aryl group that is fully or partially fluorinated.)