Electrode Assembly Width Control to Limit Battery Overhang Plating
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Solution Overview
Problem
Conventional electrode assembly designs in secondary batteries are prone to lithium plating in the overhang region due to process fluctuations, affecting the reliability of the battery.
Innovation Solution
Design the negative electrode plate with a width greater than the positive electrode plate, correlating the width difference with the extension ratio to ensure the upper limit of the width difference does not exceed 4.5−M1×a, where M1 is the positive electrode plate width, and the extension ratio a is between 0.2% and 1.7%, to mitigate lithium plating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the negative electrode plate is designed with a larger width to extend beyond the positive electrode plate, then the energy density of the battery is improved, but lithium plating occurs in the overhang region during cyclic charging and discharging
Solution Approach 1:
The patent applies parameter changes by establishing a quantitative relationship between the width difference (M2-M1) and the extension ratio (a) through the formula M2-M1≤4.5-M1×a. This transforms the design from a qualitative concept of overhang to a precisely controlled parameter relationship, where the width difference is dynamically adjusted based on the extension ratio to prevent lithium plating while maximizing energy density.
Solution Approach 2:
The patent implements feedback control by using the extension ratio (a) as a measured parameter that influences the width difference design. The extension ratio, which reflects the actual behavior of the negative electrode plate during cycling, provides feedback information that determines the appropriate width difference, creating a closed-loop design approach that adapts to the electrode's mechanical response.
2Quantity of substance
If the width difference between negative and positive electrode plates is increased to maximize energy density, then more active material can be utilized, but the probability of overhang defects increases due to process fluctuations
Solution Approach 1:
The patent transforms the fixed width difference design into a dynamic parameter relationship M2-M1≤4.5-M1×a, where the allowable width difference varies with the extension ratio. This parameter coupling allows the design to adapt to manufacturing variations, providing a buffer against process fluctuations while maintaining maximum energy density.
Solution Approach 2:
The patent applies beforehand cushioning by incorporating the extension ratio effect into the width difference design from the outset. The formula M2-M1≤4.5-M1×a预先 accounts for the electrode plate's expansion during cycling, creating a design margin that cushions against process variations and prevents overhang defects before they occur.
3Reliability
If the width difference is precisely controlled to prevent lithium plating, then reliability is improved, but the design complexity increases due to the need to calculate and control the relationship between width difference and extension ratio
Solution Approach 1:
The patent manages design complexity by establishing a clear mathematical relationship M2-M1≤4.5-M1×a between two measurable parameters (width difference and extension ratio). This transforms a complex multi-variable optimization problem into a straightforward parameter calculation, where the extension ratio serves as a known input that directly determines the appropriate width difference.
Solution Approach 2:
The patent applies self-service by using the extension ratio, which is an inherent property of the negative electrode plate material and structure, to automatically determine the appropriate width difference. The design leverages the electrode's own mechanical characteristics rather than requiring external complex control systems, allowing the structure to self-regulate the width difference based on its extension behavior.
Data Source
AI summary
The width of the negative electrode plate is designed to be greater than the width of the positive electrode plate and the width difference between the negative electrode plate and the positive electrode plate is correlated with the extension ratio of the negative electrode plate, such that the upper limit value of the width difference between the negative electrode plate and the positive electrode plate does not exceed (4.5−M1×a). The product of the extension ratio a and the width of the positive electrode plate as a subtractive term reduces the upper limit value of the width difference. The electrode assembly during cyclic charging and discharging will not experience excessive width of the portion of the negative electrode plate extending beyond the positive electrode plate due to extension of the negative electrode plate. This can alleviate lithium plating within the overhang region.