Electrolyte Solvent Composition for High-Temperature Li-Ion Cycle Life
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing power storage elements, particularly lithium-ion secondary batteries, face challenges in maintaining high cycle characteristics, especially at elevated temperatures, due to instability in the positive electrode material structure when nickel replaces a significant portion of cobalt.
Innovation Solution
A power storage element comprising a specific composition of electrolyte solvents and a metal oxide active material in the positive electrode, including ethyl methyl carbonate, ethylene carbonate, dimethyl carbonate, and dimethyl carbonate, with controlled ratios and the inclusion of lithium hexafluorophosphate, along with additives like vinylene carbonate and propane sultone, to enhance electrolyte stability and conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If nickel replaces a significant portion of cobalt in the positive electrode active material to increase capacity, then the battery capacity increases, but the structure stability deteriorates and cycle characteristics worsen
Solution Approach 1:
The patent optimizes the nickel-to-cobalt ratio parameter in the positive electrode active material to a specific range (Ni:Co = 3:2 to 7:3) to balance capacity and structure stability. Additionally, the electrolyte composition parameters are precisely controlled with specific solvent ratios (cyclic carbonate 10-40 vol%, chain carbonate 60-90 vol%) and additive concentrations to stabilize the electrode structure during cycling.
Solution Approach 2:
The patent uses composite positive electrode active material containing multiple metal elements (nickel, cobalt, and other elements) to achieve both high capacity and structure stability. The composite electrolyte system combines multiple carbonate solvents and functional additives to provide both capacity support and structure protection functions simultaneously.
2Quantity of substance
If nickel replaces cobalt to improve capacity, then the battery capacity increases, but cycle characteristics at high temperature worsen
Solution Approach 1:
The patent introduces specific electrolyte additives as intermediaries that form protective films on the electrode surface. These additives act as mediators between the high-nickel positive electrode and the electrolyte, preventing direct harmful interactions and stabilizing the electrode structure during high-temperature cycling.
Solution Approach 2:
The patent precisely controls the composition parameters of the electrolyte, including the ratio of cyclic to chain carbonates (10-40 vol% to 60-90 vol%) and the concentration of functional additives, to optimize both capacity and cycle characteristics at elevated temperatures.
3Quantity of substance
If the amount of nickel replacing cobalt increases to achieve high capacity, then the battery capacity increases, but temperature characteristics deteriorate
Solution Approach 1:
The electrolyte composition acts as an intermediary system that buffers the thermal effects on the high-nickel electrode. The specific combination of cyclic and chain carbonates with controlled ratios provides thermal stability and maintains proper electrolyte function at elevated temperatures, preventing degradation of temperature characteristics.
Solution Approach 2:
The patent optimizes the electrolyte composition parameters, particularly the ratio of cyclic carbonate to chain carbonate (10-40 vol% to 60-90 vol%), to achieve optimal temperature characteristics while maintaining high capacity. This parameter optimization ensures stable electrolyte properties across a wide temperature range.
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 proposed solution improves cycle characteristics by maintaining capacity retention rates under high-temperature conditions, enhancing the stability and conductivity of the electrolyte, thereby extending the battery's lifespan and performance.
Implementation Method 1
an electrolyte solution, wherein... the electrolyte solution is in contact with the first active material layer and the second active material layer
Data Source
AI summary
A power storage element includes a positive electrode, a negative electrode, a separator, and an electrolyte solution. A content Vemc of ethyl methyl carbonate in the electrolyte solution is 26.5 to 45.0 vol %. A content Vec of ethylene carbonate in the electrolyte solution is 9.0 to 33.5 vol %. A content Vdmc of dimethyl carbonate in the electrolyte solution is 29.5 to 41.0 vol %. A content Vdec of diethyl carbonate in the electrolyte solution is 0.0 to 0.2 vol %. A content Vpc of propylene carbonate in the electrolyte solution is 0.0 to 10.5 vol %. A content Vfec of fluoroethylene carbonate in the electrolyte solution is 0.0 vol % or more. A sum of the Vemc, the Vec, the Vdmc, the Vdec, the Vpc, and the Vfec is 97.0 to 100 vol %.