Lithium Battery Electrolyte Composition for High-Voltage Interface Stability

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Solution Overview

Problem

Lithium secondary batteries face challenges in maintaining long-term performance and safety due to unstable crystalline structures, high reactivity, and interfacial instability in Ni-rich positive electrodes and silicon-graphite negative electrodes, leading to accelerated degradation and reduced lifespan, especially under high voltage conditions.

Innovation Solution

An electrolytic solution for lithium secondary batteries is developed, comprising a lithium salt, solvent, and functional additives such as perfluoro-15-crown-5-ether and fluoroethylene carbonate, which improve the stability of the Solid Electrolyte Interphase (SEI) at high voltages, reducing oxidative decomposition and interfacial reactions, and incorporating vinylene carbonate as a negative electrode film additive to enhance film formation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If Ni-rich Ni-Co-Mn oxide is used to increase positive electrode capacity, then energy density is improved, but oxidative decomposition of electrolytic solution and interfacial reaction occur causing accelerated degradation

Engineering Contradiction:

Improvepositive electrode capacityVSAvoidbattery lifespan

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

A coating layer comprising fluorinated cyclic carbonate and fluorinated chain carbonate is formed on the surface of the positive electrode, acting as an intermediary barrier between the Ni-rich positive electrode and the electrolytic solution. This coating layer prevents direct contact and interfacial reactions while allowing lithium ion transport, thereby maintaining high capacity while improving battery lifespan and stability.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Quantity of substance

If high charging voltage is applied to increase capacity, then energy density is improved, but stability under high voltage conditions deteriorates

Engineering Contradiction:

Improvepositive electrode capacityVSAvoidelectrolytic solution stability

Core Design Contradiction:

Quantity of substanceVSStability of the object's composition

Solution Approach 1:

The invention changes the chemical composition parameters of the electrolytic solution by introducing specific fluorinated cyclic carbonate and fluorinated chain carbonate components. These modified electrolytic solution components form a stable coating layer on the positive electrode surface that is specifically designed to withstand high voltage conditions, thereby enabling high capacity operation while maintaining electrolytic solution stability.

Inventive Principle:

Principle #35Parameter changes

3Quantity of substance

If silicon-graphite negative electrode is used to increase capacity, then energy density is improved, but volume expansion and interfacial instability cause reduced lifespan

Engineering Contradiction:

Improvenegative electrode capacityVSAvoidbattery lifespan

Core Design Contradiction:

Quantity of substanceVSDuration of action of moving object

Solution Approach 1:

The coating layer comprising fluorinated cyclic carbonate and fluorinated chain carbonate serves as a protective intermediary on the positive electrode surface, preventing interfacial reactions and metal elution that would otherwise accelerate degradation. This stable interface maintains consistent lithium ion flux and prevents harmful side reactions, thereby extending battery lifespan even when silicon-graphite negative electrodes with high capacity are used.

Inventive Principle:

Principle #24Intermediary (Mediator)

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 electrolytic solution significantly improves the charging and discharging performance of high-capacity positive electrodes and silicon-graphite negative electrodes, enhancing the battery's lifespan and stability under high voltage and temperature conditions, thereby increasing the battery's marketability.

Implementation Method 1

oxidative decomposition of the electrolytic solution, interfacial reaction between the positive electrode and the electrolytic solution

Methodology Applied

Scientific EffectElectrochemical reaction:

Implementation Method 2

improve SEI stability of a silicon-graphite negative electrode and SEI stability of a positive electrode

Methodology Applied

Scientific EffectSEI formation:

Implementation Method 3

when lithium ions are intercalated/deintercalated at the positive electrode and the negative electrode

Methodology Applied

Scientific EffectIntercalation:

Implementation Method 4

an electrolyte serving as a lithium ion transfer medium

Methodology Applied

Scientific EffectIonic conduction: Conduction (electrical)

Data Source

PatentUS20230291012A1Electrolytic solution for lithium secondary batteries and lithium secondary battery including the same

Publication Date: 2023.09.14 HYUNDAI MOTOR CO LTD

AI summary

Disclosed are an electrolytic solution for lithium secondary batteries capable of improving lifespan characteristics of a lithium secondary battery under a high voltage condition and a lithium secondary battery including the same. The electrolytic solution includes a lithium salt, a solvent, and a functional additive, and the functional additive includes a high-voltage additive including a first high-voltage additive, perfluoro-15-crown-5-ether, represented by [Formula 1] and a second high-voltage additive, fluoroethylene carbonate, represented by [Formula 2].