Negative Electrode Density Control via Tap Density Regression
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Solution Overview
Problem
It is challenging to control the properties of negative electrodes in lithium-ion secondary batteries, leading to increased internal resistance, which affects the stability and performance of the batteries.
Innovation Solution
A method is developed to accurately control the density of the negative electrode active material layer by determining the tap density and selecting materials that yield a regression line with a slope of 0.5 or smaller and a coefficient of determination of 0.99 or larger, allowing for the production of lithium-ion secondary batteries with suppressed internal resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a negative electrode is formed by applying and drying a paste or slurry negative electrode material on top of a current collector, then the negative electrode can be manufactured with conventional processes, but the density of the negative electrode active material layer cannot be controlled with high accuracy, leading to increased internal resistance
Solution Approach 1:
The invention changes the parameter of tap density (from uncontrolled to controlled at 0.6-0.95 g/cm³) to achieve precise control of negative electrode active material layer density. By specifying the tap density as a key parameter during material preparation, the invention enables accurate density control without requiring complex manufacturing processes, thereby reducing internal resistance and improving battery reliability
Solution Approach 2:
The invention replaces complex mechanical control methods (such as precise pressure control during application) with a material property-based approach (tap density specification). Instead of controlling density through mechanical process parameters, the invention uses the inherent tap density property of the negative electrode active material as the control parameter, simplifying the manufacturing process while achieving high precision density control
2Reliability
If the density of the negative electrode active material layer is not accurately controlled, then the manufacturing process remains simple, but the internal resistance increases and battery properties become unstable
Solution Approach 1:
The invention introduces tap density (0.6-0.95 g/cm³) as a critical control parameter for negative electrode active material layer density. By establishing this parameter range and controlling it during material preparation, the invention achieves high manufacturing precision in density control, which directly improves battery property stability and reduces internal resistance
Solution Approach 2:
The invention implements a feedback mechanism where the tap density of the negative electrode active material is measured and controlled to ensure the resulting layer density falls within the target range. This feedback loop allows for adjustment of material properties to achieve consistent density control, thereby stabilizing battery properties and reducing internal resistance variation
Data Source
AI summary
A method for producing a lithium-ion secondary battery comprising positive and negative electrodes and a non-aqueous electrolyte solution is provided. The method comprises (A) with several different negative electrode active materials, determining density Xn (g/cm3) at several different number of taps applied, n, respectively; (B) determining density Y (g/cm3) of a negative electrode active material layer constituted with a mixture comprising each negative electrode active material; (C) based on a regression line, Y=aXn+b, determining the number of taps applied, n′, that gives a≦0.5 and a determination coefficient R2≧0.99; (D) based on a plot of Y=aXn′+b, determining a passing range of Xn′ where negative electrode active material layer density Y is in a prescribed range; (E) selecting a negative electrode active material having Xn′in the passing range, and fabricating a negative electrode with this material.