Negative Electrode Film Layer Layout to Reduce Lithium Precipitation
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Solution Overview
Problem
Lithium precipitation on electrode plates in secondary batteries leads to reduced service life and safety performance.
Innovation Solution
A secondary battery design featuring a negative electrode plate with a negative electrode film layer comprising two regions: a first region with a lower powder OI value and a second region with a higher powder OI value, arranged in the direction of the tab extension, to enhance active ion intercalation and reduce dendrite formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a uniform negative electrode film layer is used, then the manufacturing process is simple, but lithium precipitation and dendrite formation occur leading to reduced safety and service life
Solution Approach 1:
The negative electrode film layer is segmented into two distinct regions: a first region with lower powder OI value and a second region with higher powder OI value. This segmentation allows different areas to perform different functions - the first region provides high capacity while the second region prevents lithium precipitation and dendrite formation at the tab connection area, thereby resolving the contradiction between simplicity and safety.
Solution Approach 2:
Different regions of the negative electrode film layer are assigned different local qualities through varying the powder OI value. The first region has lower OI value for high capacity, while the second region has higher OI value for preventing lithium precipitation. This local differentiation addresses the safety issue without requiring complete redesign of the entire electrode structure.
2Reliability
If the powder OI value is increased to reduce lithium precipitation, then safety improves, but active ion diffusion may be hindered reducing battery performance
Solution Approach 1:
The patent applies local quality by assigning different powder OI values to different regions. The first region maintains lower OI value to ensure good active ion diffusion and high capacity, while the second region uses higher OI value specifically where lithium precipitation is most likely to occur (at the tab connection area). This spatial differentiation resolves the contradiction between safety and productivity.
Solution Approach 2:
By segmenting the electrode film into regions with different OI values, the patent allows each segment to optimize for its specific function - the first segment optimizes for ion diffusion and capacity, while the second segment optimizes for preventing precipitation. This segmentation strategy simultaneously achieves both safety and productivity goals.
3Quantity of substance
If the negative electrode plate thickness is increased to improve capacity, then energy density increases, but lithium precipitation at thickness transition areas worsens
Solution Approach 1:
The patent addresses the thickness transition issue by applying local quality - the second region with higher powder OI value is specifically positioned at areas where thickness changes occur (such as near the tab connection). This local modification prevents lithium precipitation at these critical transition zones while allowing the overall electrode to maintain high capacity through the first region with lower OI value.
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 design reduces lithium precipitation, enhances safety performance, and increases the service life of the battery by improving active ion diffusion and reducing the risk of short circuits.
Implementation Method 1
the bulk orientation degree of the active material particles at the upper edge of the negative electrode plate can be increased, which can facilitate the intercalation of active ions
Implementation Method 2
the dendrites that result from the reduction and precipitation of the active ions on the negative electrode surface can be reduced
Data Source
AI summary
A secondary battery includes an electrode assembly including a main body and a tab extending from the main body, wherein the main body includes a negative electrode plate including a negative current collector, and a negative electrode film layer arranged on at least one surface of the negative current collector, wherein the negative electrode film layer includes a first region and a second region arranged to at least one side of the first region, in the direction that the tab extends, wherein the first region includes a first negative electrode active material and the second region includes a second negative electrode active material, and wherein the first negative electrode active material has a powder OI value denoted as OIa, and the second negative electrode active material has a powder OI value denoted as OIb, wherein the negative electrode film layer satisfies OIa<OIb.