Electrode Assembly With Segmented Lithium Layer for Capacity Retention
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Solution Overview
Problem
Lithium-ion batteries face capacity fading due to active lithium loss caused by side reactions, leading to reduced energy density and high costs, especially when using lithium titanate as a negative electrode, which results in low discharge voltage and high costs per kilowatt hour.
Innovation Solution
An electrode assembly with a negative electrode plate featuring a lithium metal layer in a discontinuous pattern of spaced distribution on the surface of the negative electrode active substance layer, reducing contact with air and enhancing lithium utilization, intercalation efficiency, and SEI film stability, thereby prolonging cycle and storage life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If lithium is applied on the surface of the negative electrode plate to form a lithium metal layer, then capacity loss caused by side reactions is compensated, but lithium reacts with air resulting in low utilization rate and increased impedance
Solution Approach 1:
The lithium metal layer is divided into multiple strip-shaped lithium-rich regions that are spaced apart in the length direction of the negative electrode plate. This segmentation reduces the total contact area between lithium and air, minimizing oxidation reactions and improving lithium utilization rate while still providing sufficient lithium replenishment to compensate for capacity loss from side reactions.
Solution Approach 2:
Instead of uniformly covering the entire negative electrode plate surface with lithium, the invention applies lithium locally in specific strip-shaped regions. This localized approach concentrates lithium replenishment where most needed while reducing overall lithium exposure to air, thereby improving both capacity retention and lithium utilization efficiency.
2Reliability
If lithium is applied on the surface of the negative electrode plate, then active lithium loss is compensated, but reaction products accumulate on the surface increasing impedance
Solution Approach 1:
By segmenting the lithium metal layer into spaced strip-shaped regions, the invention reduces the total surface area where lithium can react with air. This minimizes the accumulation of reaction products such as lithium oxide and lithium carbonate on the electrode surface, thereby preventing impedance increase while still providing adequate lithium replenishment for capacity retention.
3Reliability
If lithium metal layer is provided on negative electrode, then lithium replenishment is achieved, but contact area with air increases reducing efficiency
Solution Approach 1:
The lithium metal layer is segmented into multiple strip-shaped regions spaced apart along the length direction of the negative electrode plate. This segmentation strategy reduces the total lithium surface area exposed to air, minimizing oxidation losses and improving lithium replenishment efficiency while maintaining sufficient lithium content to extend cycle life through active lithium replenishment.
Solution Approach 2:
Lithium is applied locally in strip-shaped regions rather than uniformly across the entire electrode surface. This localized application provides targeted lithium replenishment to areas where it is most needed for maintaining cycle life, while reducing overall lithium exposure to air to improve replenishment efficiency.
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 solution increases lithium replenishment efficiency, reduces direct current impedance, and significantly prolongs the cycle and storage life of lithium-ion batteries while maintaining energy density, by minimizing lithium oxidation and enhancing SEI film stability.
Implementation Method 1
after the electrode assembly is installed into the battery casing and the electrolyte is injected, at least a part of lithium in a lithium metal layer on a surface of a negative electrode active substance layer is pre-intercalated under an action of the electrolyte
Implementation Method 2
after lithium is applied on the surface of the negative electrode plate, a part of lithium will react with air, resulting in a low utilization rate of lithium in the lithium metal layer
Data Source
AI summary
An electrode assembly and a lithium-ion battery are described. The electrode assembly includes a positive electrode plate, a separator, and a negative electrode plate, where the negative electrode plate includes a negative electrode current collector and a negative electrode active substance layer, the negative electrode plate further includes a lithium metal layer, the lithium metal layer is formed by a plurality of regular or irregular strip-shaped lithium-rich regions, and the plurality of lithium-rich regions present a discontinuous pattern of spaced distribution in a length direction of the negative electrode plate. The electrode assembly further satisfies that: negative electrode capacity per unit area/positive electrode capacity per unit area=1.2 to 2.1 and negative electrode capacity per unit area/(positive electrode capacity per unit area+capacity of the lithium metal layer on the surface of the negative electrode active substance layer per unit area× 80%)≥ 1.10.