High-Voltage Nonaqueous Electrolyte Cell with Protective Covering
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Nonaqueous electrolyte secondary cells face issues with electrolyte decomposition and cobalt elution during high-voltage charging, leading to degraded preservation and cycle performance, especially at temperatures and potentials above 4.3V.
Innovation Solution
Incorporating 1,3-dioxane in the electrolyte and lithium phosphate in the positive electrode, along with a negative electrode made of noncrystalline carbon-covered graphite particles, to form protective coverings that inhibit electrolyte decomposition and enhance structural and thermal stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the positive electrode is charged to a potential higher than 4.3V to enhance cell capacity, then the use efficiency of the positive electrode active material is improved, but the electrolyte is oxidatively decomposed at the positive electrode side, compromising cell preservation performance and cycle property
Solution Approach 1:
The patent applies preliminary action by forming a protective covering on the positive electrode surface before electrolyte decomposition can occur. The covering is formed during initial charging cycles through controlled oxidation reactions, creating a stable interface that prevents subsequent electrolyte degradation during high-voltage charging operations
Solution Approach 2:
The patent introduces an intermediary substance (protective covering) that mediates between the positive electrode active material and the electrolyte. This covering acts as a barrier layer that allows ionic transport while preventing direct contact between the electrolyte and electrode, thereby preventing oxidative decomposition during high-voltage charging
2Quantity of substance
If the positive electrode is charged to a potential higher than 4.3V to enhance cell capacity, then the use efficiency of the positive electrode active material is improved, but cobalt is eluted into the electrolyte solution and precipitates on the negative electrode, degrading preservation property and cycle property
Solution Approach 1:
The protective covering serves as an intermediary barrier that prevents cobalt elution from the positive electrode into the electrolyte. By blocking the direct interface between electrode material and electrolyte, the covering prevents cobalt ions from detaching and migrating to the negative electrode during high-voltage charging cycles
Solution Approach 2:
The patent converts the potentially harmful high-voltage charging condition into a beneficial outcome by using controlled initial charging cycles to form the protective covering. This covering then enables sustained high-voltage operation without the harmful effects of cobalt elution and electrolyte decomposition
3Stability of the object's composition
If lithium cobalt oxide with different elements added is used to improve structural stability during high voltage charging, then the resistance of the positive electrode active material against high voltage charging is enhanced, but the complexity of the positive electrode active material composition increases
Solution Approach 1:
The patent applies parameter changes by modifying the chemical composition parameters of the lithium cobalt oxide, specifically by adding different elements (such as magnesium, aluminum, or titanium) in controlled amounts. These compositional parameter changes enhance the structural stability of the cathode material during high-voltage charging while maintaining a relatively simple overall material system
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 configuration significantly improves charge preservation performance, initial capacity, and cycle properties by preventing oxidative decomposition and cobalt elution, while maintaining stable performance at high temperatures and potentials.
Implementation Method 1
the nonaqueous electrolyte contains 1,3-dioxane... forming protective coverings that inhibit electrolyte decomposition
Implementation Method 2
lithium phosphate in the positive electrode... to form protective coverings that inhibit electrolyte decomposition and enhance structural and thermal stability
Implementation Method 3
negative electrode made of noncrystalline carbon-covered graphite particles... preventing oxidative decomposition and cobalt elution
Data Source
AI summary
The preservation performance of a nonaqueous electrolyte secondary cell charged to high potential is improved while the initial capacity and the cycle property of the cell are also improved. The nonaqueous electrolyte secondary cell includes: a positive electrode having lithium phosphate and a positive electrode active material containing lithium cobalt compound oxide and lithium manganese nickel compound oxide having a layer structure, the lithium cobalt compound oxide having at least zirconium and magnesium added in LiCoO2; a negative electrode having a negative electrode active material; and a nonaqueous electrolyte having a nonaqueous solvent and an electrolytic salt. The potential of the positive electrode is more than 4.3 V and 5.1 V or less based on lithium. The nonaqueous electrolyte contains vinylene carbonate as the nonaqueous solvent and, as the electrolytic salt, at least one of lithium bis(pentafluoroethane sulfonyl)imide and lithium bis(trifluoromethane sulfonyl)imide at 0.1 M or more and 0.5 M or less. The nonaqueous electrolyte contains 1,3-dioxane.