Lithium Metal Anode Covering Layer for Cycle Endurance
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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 caused by the high lithium-ion conductivity of protective layers, leading to insufficient impregnation and peeling issues.
Innovation Solution
A lithium metal negative electrode battery configuration with a covering layer having a low lithium-ion conductivity (1.0×10−13 to 2.0×10−9 S/cm) is used, which reduces lithium ion permeation, enhancing the bonding between the lithium metal layer and the covering layer, and includes a binder with a volume fraction of 0.2 or more, along with specific components like lithium phosphate with adjusted crystallinity, to improve peel strength and cycle endurance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a protective layer with high lithium-ion conductivity (such as lithium phosphate) is formed on the negative electrode base material, then uniform lithium metal deposition is achieved, but the lithium metal layer becomes insufficiently impregnated with electrolyte solution and peeling occurs at the interface
Solution Approach 1:
The patent changes the lithium-ion conductivity parameter of the covering layer from high (conventional lithium phosphate with conductivity around 1.0×10^-7 S/cm) to low (1.0×10^-13 to 2.0×10^-9 S/cm). This parameter change allows the covering layer to maintain uniform deposition function while preventing excessive lithium ion permeation that causes peeling. The low conductivity ensures sufficient electrolyte impregnation and strong bonding between layers.
Solution Approach 2:
The patent uses composite materials for the covering layer, specifically combining lithium phosphate with other compounds (such as lithium borate, lithium silicate, or organic-inorganic hybrid materials) to achieve the target low lithium-ion conductivity range. This composite approach maintains the protective function while controlling ion transport to prevent peeling.
2Productivity
If the lithium-ion conductivity of the covering layer is high, then lithium ions can easily reach the negative electrode base material for deposition, but capacity degradation occurs due to insufficient impregnation and peeling
Solution Approach 1:
The patent optimizes the lithium-ion conductivity parameter to a specific low range (1.0×10^-13 to 2.0×10^-9 S/cm) that balances deposition efficiency with structural stability. This parameter optimization ensures adequate lithium ion transport for deposition while preventing the peeling and impregnation issues that cause capacity degradation and reduce cycle endurance.
3Device complexity
If conventional lithium phosphate with high conductivity is used as the protective layer, then the structure is simple, but the three-layer structure forms with poor contact between layers leading to rapid capacity degradation
Solution Approach 1:
The patent modifies the conductivity parameter of the lithium phosphate-based covering layer from high to low (1.0×10^-13 to 2.0×10^-9 S/cm), which fundamentally changes the interaction between the covering layer and lithium metal layer. This parameter change prevents the formation of the problematic three-layer structure with poor contact, ensuring good interfacial contact and high cycle endurance while maintaining structural simplicity.
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 low lithium-ion conductivity covering layer reduces lithium ion permeation, enhancing the bonding between the lithium metal layer and the covering layer, thereby improving cycle endurance and reducing capacity degradation.
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
Implementation Method 3
During discharging, Li metal dissolves into the electrolyte solution
Data Source
AI summary
A lithium metal negative electrode secondary battery comprises a positive electrode, a separator, a negative electrode, and an electrolyte solution. The electrolyte solution includes Li ions. The separator is interposed between the positive electrode and the negative electrode. The negative electrode includes a negative electrode base material and a covering layer. The covering layer covers at least part of a surface of the negative electrode base material. The covering layer includes a Li-ion conductor. The Li-ion conductor has a Li-ion conductivity from 1.0×10−13 to 2.0×10−9 S/cm.