Lithium-Ion Battery Electrolyte Moisture Control for Cycle Stability
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Solution Overview
Problem
Lithium-ion secondary batteries face challenges in achieving high capacity, excellent charge and discharge cycle performance, rapid charging, and long-life operation, especially at high temperatures and high voltages, with issues related to capacity reduction and metal elution, such as cobalt, during charging and discharging.
Innovation Solution
A secondary battery design with a positive electrode active material containing lithium, a transition metal like cobalt, and an additive element, such as magnesium or fluorine, in a layered rock-salt crystal structure, optimized to minimize moisture in the electrolyte and maintain a stable crystal structure, which suppresses metal elution and enhances cycle performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If high voltage charging is performed to increase energy density, then battery capacity is improved, but metal elution (especially cobalt) occurs and cycle performance deteriorates
Solution Approach 1:
A coating layer comprising at least one of a metal oxide, metal hydroxide, metal carbonate, or metal oxyhydroxide is formed on the positive electrode active material surface. This coating layer acts as an intermediary barrier that suppresses metal elution during high voltage charging while maintaining battery capacity and cycle performance
2Speed
If rapid charging is implemented to improve charging speed, then charging time is reduced, but heat generation increases and safety deteriorates
Solution Approach 1:
The coating layer on the positive electrode active material surface serves as a protective intermediary that facilitates rapid charging while suppressing excessive heat generation through controlled ion transport and reduced resistance
Solution Approach 2:
The coating layer modifies the surface properties of the positive electrode active material, changing parameters such as surface conductivity and ion diffusion characteristics to enable rapid charging with controlled heat generation
3Quantity of substance
If high temperature operation is permitted to improve performance, then energy density is increased, but capacity reduction accelerates and reliability decreases
Solution Approach 1:
The coating layer acts as a thermal and chemical intermediary that protects the positive electrode active material from high temperature degradation, suppressing capacity reduction while maintaining energy density
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 results in a lithium-ion secondary battery with improved capacity, cycle stability, and safety, capable of rapid charging and operation at high temperatures, with reduced capacity loss and enhanced energy density due to the stable crystal structure and controlled electrolyte moisture levels.
Implementation Method 1
maintain a stable crystal structure, which suppresses metal elution
Implementation Method 2
minimize moisture in the electrolyte
Data Source
AI summary
A lithium-ion secondary battery with high capacity and excellent charge and discharge cycle performance is provided. A secondary battery with high capacity is provided. A secondary battery with excellent charge and discharge characteristics is provided. A secondary battery in which a reduction in capacity is inhibited even when a state being charged with a high voltage is held for a long time is provided. A secondary battery includes a positive electrode, a negative electrode, and an electrolyte, and the amount of moisture in the electrolyte is less than 1000 ppm.