Fluorinated Carbonate Electrolyte for Floating-Charge Stability

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Solution Overview

Problem

High-voltage electrochemical devices face issues with cathode material oxidizability and stability, leading to non-aqueous electrolyte decomposition and reduced battery capacity due to floating-charge phenomena, which affect reliability and performance.

Innovation Solution

An electrolyte comprising a fluorinated cyclic carbonate and a multi-nitrile compound with an ether bond, where the weight percentage of the fluorinated cyclic carbonate is greater than the multi-nitrile compound, along with additional components like fluoroethers and cyclic phosphonic anhydrides, is used to enhance the electrochemical device's cycle, storage, and floating-charge performance by forming a stable solid electrolyte interface and suppressing thickness expansion.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If high-voltage cathode material is used to increase energy density, then energy density is improved, but cathode material stability deteriorates leading to electrolyte decomposition

Engineering Contradiction:

Improveenergy densityVSAvoidcathode material stability

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

The patent introduces a mediator substance (specifically a cyclic carboxylate or cyclic carbonate additive) into the electrolyte system. This intermediary forms a protective interface film on the cathode surface, acting as a buffer between the high-voltage cathode material and the non-aqueous electrolyte, preventing direct harmful interactions while allowing electrochemical reactions to proceed

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent changes the chemical composition parameters of the electrolyte by introducing specific cyclic carboxylates or cyclic carbonates with defined molecular structures and ratios. This parameter modification alters the electrochemical window and stability characteristics of the electrolyte system, enabling it to withstand higher voltages without decomposition

Inventive Principle:

Principle #35Parameter changes

2Reliability

If floating charge is applied to maintain full charge state, then battery capacity is maintained, but device swelling and thickness expansion occur

Engineering Contradiction:

Improvebattery capacity maintenanceVSAvoiddevice thickness

Core Design Contradiction:

ReliabilityVSLength of stationary object

Solution Approach 1:

The cyclic carboxylate or cyclic carbonate additive acts as an intermediary that forms a stable solid electrolyte interface (SEI) film on the electrode surfaces. This intermediary layer prevents direct contact between the electrolyte and electrode, suppressing side reactions and gas generation that would otherwise cause swelling and thickness expansion during floating charge

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent modifies the electrolyte composition by adding specific cyclic carboxylates or cyclic carbonates in controlled ratios (0.1-10 wt%). This parameter change alters the electrochemical behavior of the system, reducing impedance and stabilizing the electrode-electrolyte interface, thereby preventing volume expansion during prolonged floating charge states

Inventive Principle:

Principle #35Parameter changes

3Ease of manufacture

If conventional electrolyte composition is used, then manufacturing simplicity is maintained, but decomposition occurs at high voltage

Engineering Contradiction:

Improveelectrolyte preparation simplicityVSAvoidelectrolyte stability

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The patent creates a composite electrolyte system by combining conventional electrolyte components (lithium salt, cyclic carbonate, chain carbonate) with small amounts of cyclic carboxylate or cyclic carbonate additives. This composite approach maintains the ease of manufacturing conventional electrolytes while introducing functional components that enhance high-voltage stability through synergistic interactions

Inventive Principle:

Principle #40Composite materials

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 electrolyte composition improves the electrochemical device's stability and performance by reducing impedance, inhibiting decomposition, and maintaining capacity retention, thereby enhancing cycle and storage performance and extending floating-charge life.

Implementation Method 1

forming a stable solid electrolyte interface

Methodology Applied

Scientific EffectSolid electrolyte interface formation:

Implementation Method 2

electrochemical device

Methodology Applied

Scientific EffectElectrochemical reaction:

Data Source

PatentUS11901513B2Electrolyte and electrochemical device comprising the same

Publication Date: 2024.02.13 NINGDE AMPEREX TECHNOLOGY LTD

AI summary

An electrolyte includes a fluorinated cyclic carbonate, a chain carboxylate and a multi-nitrilemulti-nitrile compound having an ether bond. Based on a total weight of the electrolyte, a weight percentage (Cf) of the fluorinated cyclic carbonate is greater than a weight percentage (Cn) of the multi-nitrilemulti-nitrile compound having an ether bond. The electrolyte can control the expansion of the electrochemical device, so that the electrochemical device has excellent cycle, storage and/or floating-charge performance.