Anode-Free Lithium Secondary Battery for Uniform Lithium Deposition
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Solution Overview
Problem
Lithium secondary batteries with negative electrodes containing active materials face limitations in energy density and cycle characteristics due to the volume and mass occupied by these materials, while anode-free batteries suffer from dendritic lithium growth and capacity loss, and applying high pressure to maintain interface integrity increases mass and volume, reducing energy density.
Innovation Solution
A lithium secondary battery design featuring a negative electrode without active materials, a carbon metal composite layer with randomly oriented fibrous carbon materials, and a conductive thin film on the separator, which enhances electrical conductivity and uniform lithium deposition, suppressing dendrite growth and improving cycle characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a negative electrode containing negative-electrode active material is used, then the battery structure is stable, but the energy density and capacity are insufficient due to volume and mass occupied by the active material
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 active material coating. This eliminates the mass and volume occupied by active material while maintaining structural stability through the current collector alone, thereby significantly improving energy density and capacity.
2Reliability
If high mechanical pressure is applied to maintain interface between negative electrode and separator, then interface integrity is improved, but mass and volume increase reducing energy density
Solution Approach 1:
The invention applies a conductive thin film coating to the separator surface before assembly, which preliminarily establishes good electrical contact and promotes uniform lithium deposition. This preliminary action ensures interface integrity and prevents dendrite formation without requiring high mechanical pressure during operation, thereby avoiding the mass and volume increase that would reduce energy density.
3Quantity of substance
If anode-free lithium secondary battery is used, then energy density is improved, but dendritic lithium growth occurs causing short circuit and capacity loss
Solution Approach 1:
The invention introduces a conductive thin film as an intermediary layer on the separator surface facing the negative electrode. This intermediary promotes uniform lithium ion distribution and deposition, preventing direct dendritic growth into the electrolyte while maintaining the anode-free structure's high energy density advantages. The fibrous carbon material in the composite layer also acts as a mediator to guide uniform lithium deposition.
4Quantity of substance
If negative electrode without active material is used, then energy density increases, but dendritic lithium metal formation occurs on negative electrode surface
Solution Approach 1:
The conductive thin film serves as an intermediary between the negative electrode current collector and the electrolyte, promoting uniform lithium ion distribution and deposition. This intermediary layer prevents direct dendritic growth on the current collector surface while maintaining electrical conductivity and enabling the high energy density benefits of the anode-free structure.
Solution Approach 2:
The invention changes the surface properties of the separator by coating it with a conductive thin film, which alters the electrical and surface characteristics at the interface. This parameter change promotes uniform lithium deposition by improving electrical contact and distributing current more evenly, thereby preventing dendrite formation while maintaining high energy 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
This design achieves high energy density and excellent cycle characteristics by reducing battery volume and mass, preventing dendrite formation, and maintaining interface integrity without the need for high mechanical pressure, resulting in improved safety and productivity.
Implementation Method 1
a conductive thin film formed on a surface of the separator facing the negative electrode
Implementation Method 2
charge is performed by a direct deposition of new lithium metal on the lithium metal as the negative-electrode active material
Implementation Method 3
the carbon metal composite layer includes a plurality of fibrous carbon materials, each of which are randomly oriented
Data Source
AI summary
An object of the present invention is to provide a lithium secondary battery having a high energy density and excellent in cycle characteristics. The present invention relates to a lithium secondary battery including a positive electrode, a negative electrode not having a negative-electrode active material, a separator placed between the positive electrode and the negative electrode, a carbon metal composite layer formed on a surface of the negative electrode facing the separator, and a conductive thin film formed on a surface of the separator facing the negative electrode, in which the carbon metal composite layer includes a plurality of fibrous carbon materials, each of which are randomly oriented.