Non-aqueous Electrolyte Coating for Battery Stability
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Solution Overview
Problem
Nonaqueous electrolyte secondary batteries face challenges in increasing capacity while maintaining uniform electrolyte distribution and stability, especially with materials that alloy with lithium, leading to nonuniform charge/discharge reactions and degradation due to low-viscosity solvents with narrow potential windows.
Innovation Solution
Incorporating benzotrifluoride and a diisocyanate compound into the electrolyte solution to form a denser coating on the negative-electrode active material, enhancing electrochemical stability and suppressing side reactions, even with low-viscosity solvents, thereby improving charge-discharge cycle characteristics and high-temperature storage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a large amount of active material is packed into the battery to increase packing density, then the battery capacity increases, but the electrolyte solution becomes difficult to infiltrate into the entire region of the inside of the battery, causing nonuniform charge/discharge reactions and local deterioration
Solution Approach 1:
The patent changes the chemical composition parameters of the electrolyte solution by introducing a specific cyclic carboxylate component and adjusting the ratio of cyclic carbonate to chain carbonate within 5:95 to 45:55 by volume. This parameter optimization enables the electrolyte to effectively infiltrate high-density electrode structures while maintaining uniform charge/discharge reactions throughout the battery interior.
2Quantity of substance
If materials capable of alloying with lithium (such as silicon) are used as the negative-electrode active material, then the battery capacity increases, but the volume of the negative-electrode active material is significantly increased by a charge reaction, causing the electrolyte solution to be squeezed out of the electrode assembly
Solution Approach 1:
The patent optimizes the electrolyte composition by incorporating cyclic carboxylate and adjusting cyclic-to-chain carbonate ratios, enabling the electrolyte to accommodate volume changes of alloying materials during charge/discharge cycles while preventing electrolyte expulsion and maintaining stable distribution throughout the electrode assembly.
Solution Approach 2:
The cyclic carboxylate component acts as an intermediary substance that mediates between the alloying negative-electrode active material and the electrolyte solution, forming stable interfaces that prevent electrolyte expulsion during volume expansion of the alloying material while maintaining electrochemical stability.
3Force
If low-viscosity chain carbonates, carboxylic acid esters, or ketones are used to reduce the viscosity of the electrolyte solution, then the electrolyte solution can infiltrate the electrode assembly more effectively, but these materials have relatively narrow potential windows and high reactivity, causing electrochemical instability and side reactions with the active material
Solution Approach 1:
The patent creates a composite electrolyte system combining cyclic carbonate, chain carbonate, and cyclic carboxylate components. This composite formulation achieves low viscosity for effective infiltration while the cyclic carboxylate provides electrochemical stability and suppresses side reactions, overcoming the limitations of individual low-viscosity components.
Solution Approach 2:
The cyclic carboxylate serves as an intermediary component that stabilizes the electrolyte system, reducing the reactivity of low-viscosity chain carbonate and carboxylic acid ester components with the active material, thereby preventing decomposition and side reactions while maintaining low viscosity.
4Force
If low-viscosity solvents with narrow potential windows are used, then the viscosity of the electrolyte solution is reduced, but the nonaqueous electrolyte solution becomes electrochemically unstable and easily causes side reactions with the active material, particularly with materials capable of alloying with lithium
Solution Approach 1:
The cyclic carboxylate component acts as a protective intermediary between the low-viscosity electrolyte solution and the alloying active material, forming stable surface films that prevent direct contact and side reactions while allowing ionic transport, thereby eliminating the harmful effects of high reactivity.
Solution Approach 2:
The patent formulates a composite electrolyte where cyclic carboxylate combines with low-viscosity chain carbonate and cyclic carbonate to create a synergistic system that achieves both low viscosity for good infiltration and high electrochemical stability through the protective effect of cyclic carboxylate.
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 use of benzotrifluoride and diisocyanate compounds in the electrolyte solution significantly increases electrochemical stability, reduces degradation, and enhances storage characteristics in high-temperature environments, even with low-viscosity solvents, leading to improved battery performance and cycle life.
Implementation Method 1
the diisocyanate compound contained in the nonaqueous electrolyte solution reacts with and binds to hydroxyl groups existing on the surface of the negative-electrode active material and a coating formed by the reaction
Implementation Method 2
benzotrifluoride contained in the nonaqueous electrolyte solution interacts with the diisocyanate compound to form a denser coating
Implementation Method 3
it is important to retain a state in which the electrolyte solution uniformly diffuses in the inside of the battery
Implementation Method 4
the electrolyte solution squeezed out of the electrode assembly needs to be infiltrated into the inside of the electrode assembly again
Data Source
AI summary
Provided is a nonaqueous electrolyte secondary battery which, even in the case of using a low-viscosity solvent having a narrow potential window, can increase the electrochemical stability of the nonaqueous electrolyte solution and suppress side reactions of the nonaqueous electrolyte solution during charge and discharge to reduce the degradation of the battery characteristics and has an excellent storage characteristic in high-temperature environments and a nonaqueous electrolyte solution for the nonaqueous electrolyte secondary battery. The nonaqueous electrolyte secondary battery includes: a positive electrode containing a positive-electrode active material; a negative electrode containing a negative-electrode active material; and a nonaqueous electrolyte solution containing a solute dissolved in a nonaqueous solvent, wherein the nonaqueous electrolyte solution further contains benzotrifluoride and a diisocyanate compound and the content of benzotrifluoride is 5% by volume or more in the nonaqueous electrolyte solution except the solute.