Nonaqueous Electrolyte Battery Separator Protection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Nonaqueous electrolyte secondary batteries face challenges in increasing charging voltage without deteriorating the separator, leading to limited capacity and discharge rate characteristics, especially at high temperatures.
Innovation Solution
Incorporating an inorganic particle layer between the positive electrode and the separator, combined with a nonaqueous solvent containing a chain fluorinated carboxylate ester, such as methyl 3,3,3-trifluoropropionate, to prevent separator oxidation and enhance high-temperature charging storage characteristics without compromising discharge rate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the charging voltage is increased to increase battery capacity, then the battery capacity is improved, but the separator material deteriorates and oxidizes
Solution Approach 1:
An inorganic particle layer is introduced as an intermediary between the positive electrode and the separator. This layer acts as a protective barrier that prevents direct contact and oxidation between the high-voltage positive electrode and the separator, enabling charging voltages above 4.2V without separator deterioration.
Solution Approach 2:
The battery structure is enhanced by combining multiple materials: the original separator, inorganic particles (such as alumina, silica, or titania), and a specifically formulated nonaqueous electrolyte containing chain fluorinated carboxylate ester. This composite structure provides both high-voltage stability and separator protection.
2Reliability
If an inorganic particle layer is disposed between the positive electrode and the separator to prevent separator oxidation, then the separator stability is improved, but the discharge rate characteristics deteriorate
Solution Approach 1:
The properties of the nonaqueous electrolyte are changed by incorporating chain fluorinated carboxylate ester (15-30% by volume), which modifies the electrolyte's interaction with the inorganic particle layer. This parameter change reduces electrolyte resistance and improves ion transport through the particle layer, thereby enhancing discharge rate characteristics while maintaining separator stability.
3Quantity of substance
If the charging voltage is increased beyond 4.2V, then the battery capacity is improved, but gas generation occurs due to separator oxidization
Solution Approach 1:
The inorganic particle layer serves as a protective intermediary that prevents oxidation of the separator by the high-voltage positive electrode. By blocking this oxidation reaction, the layer eliminates the source of gas generation, enabling safe operation at charging voltages above 4.2V without harmful gas evolution.
4Quantity of substance
If the thickness of the separator is reduced to increase battery density, then the battery energy density is improved, but the separator becomes more susceptible to oxidation and deterioration
Solution Approach 1:
A composite protective system is created combining the thin separator with an inorganic particle layer and fluorinated carboxylate ester-containing electrolyte. This composite structure allows the separator to be made thinner for higher density while the inorganic particles and specialized electrolyte provide enhanced oxidation resistance, compensating for the reduced separator thickness.
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 improves discharge rate characteristics and high-temperature charging storage capacity, allowing for higher charge termination voltages without structural deterioration or gas generation, thus enhancing the battery's reliability and performance.
Implementation Method 1
the nonaqueous solvent contains a chain fluorinated carboxylate ester represented by Formula (1) in an amount of 15% by volume or more based on the total amount of the nonaqueous solvent
Implementation Method 2
a battery voltage of higher than 4.2 V at the completion of the charging oxidizes the separator made of polyethylene to degrade the separator
Implementation Method 3
an inorganic particle layer is disposed between the positive electrode and the separator
Implementation Method 4
a nonaqueous electrolyte of a nonaqueous solvent containing a lithium salt
Data Source
AI summary
In a nonaqueous electrolyte secondary battery including a positive electrode containing a positive electrode active material, a negative electrode containing a negative electrode active material, a nonaqueous electrolyte containing a lithium salt in a nonaqueous solvent, and a separator disposed between the positive electrode and the negative electrode, an inorganic particle layer is disposed between the positive electrode and the separator, and the nonaqueous solvent contains a chain fluorinated carboxylate ester represented by the formula CH3-XFX—CH2—COO—CH3 (where, x is an integer of 1 to 3) in an amount of 15% by volume or more based on the total amount of the nonaqueous solvent.