Lithium Metal Negative Electrode with Embedded Li-Ion Conductor
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Solution Overview
Problem
Lithium metal negative electrode secondary batteries face challenges in cycle endurance due to non-uniform lithium metal deposition and capacity degradation, particularly caused by the protective layer formed on the surface of the negative electrode, which inhibits contact between the lithium metal layer and the electrolyte solution, leading to impaired peel strength and rapid capacity degradation.
Innovation Solution
A lithium metal negative electrode secondary battery configuration is introduced, featuring a negative electrode with a lithium metal layer and a lithium-ion conductor with a conductivity of 2.0×10^-9 S/cm or less, where the lithium-ion conductor is trapped within the lithium metal layer, enhancing mobility of lithium ions and reducing side reactions, and the presence ratio of the lithium-ion conductor is maintained between 0.1 and 0.5 to improve cycle endurance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a protective layer including lithium phosphate is formed on the surface of the negative electrode base material, then uniform deposition of lithium metal is achieved, but contact between the lithium metal layer and the electrolyte solution is inhibited, leading to capacity degradation
Solution Approach 1:
The patent applies local quality by creating a non-uniform distribution of lithium phosphate particles within the lithium metal layer. The particles are concentrated near the interface with the negative electrode base material, while the outer regions maintain direct contact with the electrolyte solution. This localized arrangement allows the protective function at the interface while preserving electrolyte access at the surface.
Solution Approach 2:
The patent inverts the conventional approach by not placing the protective layer as a separate surface coating, but rather embedding lithium phosphate particles within the bulk of the lithium metal layer. This inversion allows the protective function to be distributed throughout the layer rather than concentrated at the surface, resolving the contradiction between protection and electrolyte contact.
2Quantity of substance
If the lithium metal layer becomes thicker during charging, then more lithium is stored, but the protective layer is pushed up, forming a three-layer structure that inhibits lithium-ion transport
Solution Approach 1:
The patent applies preliminary action by pre-distributing lithium phosphate particles throughout the lithium metal layer before charging begins. This preliminary distribution ensures that as the layer thickens during charging, the protective particles are already in position to prevent side reactions, while the electrolyte can still access lithium ions through the porous structure.
Solution Approach 2:
The patent utilizes a porous structure for the lithium metal layer, allowing electrolyte penetration throughout the layer thickness. The porous architecture maintains lithium-ion transport pathways even as the layer thickens, preventing the formation of a dense three-layer structure that would block ion transport.
3Object-generated harmful factors
If lithium ions are not sufficiently supplied to the interface between the negative electrode base material and the lithium metal layer, then side reactions are facilitated, but peel strength between the layers is impaired
Solution Approach 1:
The patent uses lithium phosphate particles as intermediary substances embedded within the lithium metal layer. These particles act as mediators that reduce side reactions between lithium metal and the electrolyte solution, while their distributed arrangement prevents excessive peeling by maintaining adhesion throughout the layer rather than at a single interface.
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 configuration improves cycle endurance by maintaining lithium-ion mobility and reducing capacity degradation, while ensuring that lithium-ion conductivity is not excessively inhibited, thereby enhancing the battery's performance and longevity.
Implementation Method 1
The lithium-ion conductor has a lithium-ion conductivity from 1.0×10^-13 to 2.0×10^-9 S/cm
Implementation Method 2
During charging, Li metal becomes deposited from the electrolyte solution. Li ions move through the protective layer to reach the surface of the negative electrode base material. At the surface of the negative electrode base material, Li ions receive electrons and thereby Li metal becomes deposited.
Implementation Method 3
During discharging, Li metal dissolves into the electrolyte solution
Data Source
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AI summary
A lithium metal negative electrode secondary battery (100) comprises a positive electrode (10), a separator (30), a negative electrode (20), and an electrolyte solution. The electrolyte solution includes Li ions. The separator (30) is interposed between the positive electrode (10) and the negative electrode (20). The negative electrode (20) includes a negative electrode base material (21) and a Li metal layer (22). The Li metal layer (22) includes a continuous phase (22a) and a dispersed phase (22b). The continuous phase (22a) includes Li metal. The dispersed phase (22b) includes a Li-ion conductor. The Li-ion conductor has a Li-ion conductivity from 1.0×10-13 to 2.0x 10-9 S/cm.