Lithium Ion Battery Output and Cycle Life via Resistivity Ratio
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Solution Overview
Problem
Lithium ion secondary batteries face a trade-off between increasing output and maintaining cycle lifetime, as reducing electrode resistance can lead to uneven ion conductivity and electrode reaction distribution, resulting in shortened battery life.
Innovation Solution
A lithium ion secondary battery design with a power generating element having a volume resistivity ratio of 0.4 to 0.9 (mΩcm) per positive electrode plate area, achieved by optimizing the composition, structure, and arrangement of electrode materials, conductive auxiliary agents, and electrolyte solution, ensuring balanced electron and ion conduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If electrode resistance is reduced to increase battery output, then power increases, but ion conductivity becomes uneven and electrode reaction distribution occurs, shortening cycle lifetime
Solution Approach 1:
The patent applies parameter changes by precisely controlling the ratio of electrode layer thickness to current collector thickness within 0.03-0.15, and adjusting the porosity of the electrode layer to 30-80%. These parameter optimizations balance electron conduction and ion conductivity, allowing high power output while preventing uneven reaction distribution and maintaining long cycle lifetime.
Solution Approach 2:
The patent implements local quality by creating optimal local conditions within the electrode structure. By controlling the electrode layer thickness and porosity distribution, the invention ensures that both electron conduction paths and ion diffusion paths are optimized locally throughout the electrode, preventing concentration polarization and uneven reaction distribution that would otherwise shorten cycle life.
2Quantity of substance
If electrode layer thickness is increased to improve capacity, then energy density increases, but resistance increases and output decreases
Solution Approach 1:
The patent resolves this contradiction through parameter changes by establishing the optimal thickness ratio between electrode layer and current collector (0.03-0.15) and controlling electrode porosity (30-80%). This allows maximizing active material quantity while maintaining low resistance, achieving both high capacity and high output performance simultaneously.
3Power
If electrode reaction is intensified to increase power output, then battery output increases, but side reactions occur and cycle lifetime shortens
Solution Approach 1:
The patent prevents side reactions while maintaining high power output through parameter optimization. By controlling electrode layer thickness ratio (0.03-0.15) and porosity (30-80%), the invention ensures uniform current and ion distribution, preventing localized overheating and concentration polarization that would otherwise trigger harmful side reactions and reduce cycle lifetime.
Solution Approach 2:
The patent applies equipotentiality by creating uniform potential distribution throughout the electrode through optimized thickness and porosity. This uniform distribution prevents localized high current density spots that would cause uneven reaction intensity and trigger side reactions, enabling sustained high power output without compromising cycle life.
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
This design enhances battery output while maintaining cycle lifetime by preventing electrode reaction distribution and side reactions, thus improving overall battery performance.
Implementation Method 1
decreasing the resistance of the electrode layer in order to improve the output of the battery results in the lower ion conductivity of the electrolyte solution
Implementation Method 2
the lower ion conductivity of the electrolyte solution relative to the electron conduction of the electrode layer
Data Source
AI summary
Provided is a lithium ion secondary battery including a power generating element that includes at least one positive electrode plate, at least one negative electrode plate, and at least one separator. A ratio B/A (mΩcm) of volume resistivity B (mΩcm3) of the power generating element to an area A (cm2) per one positive electrode plate is 0.4 or more and less than 0.9.