Fluorinated Ester Electrolyte for Silicon Composite Anode Rate Performance

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Solution Overview

Problem

Secondary batteries with silicon particles and a lithium silicate phase experience deterioration in rate performance due to volume fluctuations during high-rate charging/discharging, leading to cracks in the base particles and increased internal resistance.

Innovation Solution

Incorporating a fluorine-containing linear carboxylic acid ester in the electrolytic solution, which forms a Solid Electrolyte Interphase (SEI) film on the base particles, reducing crack formation and enhancing lithium ion conductivity, thereby maintaining battery performance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If the content of silicon particles is increased to achieve high capacity, then the battery capacity is improved, but the rate performance deteriorates due to volume fluctuations and crack formation during repeated charging/discharging

Engineering Contradiction:

Improvebattery capacityVSAvoidrate performance

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

The fluorine-containing linear carboxylic acid ester performs preliminary action by forming an SEI film on the base particles before significant volume fluctuations occur. This pre-formed protective layer prevents crack formation during subsequent high-rate charging/discharging cycles, thereby maintaining rate performance while allowing high silicon particle content for high capacity

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The fluorine-containing linear carboxylic acid ester acts as an intermediary substance between the silicon particles and the electrolytic solution. It forms an intermediate SEI film layer that mediates the interaction, protecting the silicon particles from direct contact with the electrolyte and preventing crack formation while still allowing lithium ion transport

Inventive Principle:

Principle #24Intermediary (Mediator)

2Power

If high-rate charging/discharging is performed to improve power output, then the power delivery is enhanced, but cracks occur in base particles due to drastic volume fluctuation, forming resistant layers that hamper lithium ion transfer

Engineering Contradiction:

Improvepower deliveryVSAvoidcrack formation and resistant layer

Core Design Contradiction:

PowerVSObject-affected harmful factors

Solution Approach 1:

The fluorine-containing linear carboxylic acid ester provides beforehand cushioning by forming an SEI film that acts as a cushioning layer before cracks can form. This protective film absorbs and distributes the mechanical stress from volume fluctuations during high-rate charging/discharging, preventing crack formation and the subsequent formation of resistant layers that would hamper lithium ion transfer

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

3Ease of operation

If conventional electrolytic solutions are used with silicon composite negative electrodes, then the battery can operate, but the rate performance deteriorates due to electrolyte decomposition and resistant layer formation

Engineering Contradiction:

Improvebattery operationVSAvoidrate performance

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

The invention changes the chemical composition parameter of the electrolytic solution by introducing a fluorine-containing linear carboxylic acid ester with specific molecular structure (where R1 is a hydrogen atom or methyl group and R2 is a fluorine-containing alkyl group). This parameter change in electrolyte composition leads to formation of a more stable SEI film that prevents electrolyte decomposition and resistant layer formation, thereby maintaining rate performance while allowing normal battery operation

Inventive Principle:

Principle #35Parameter changes

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 SEI film formed by the fluorine-containing linear carboxylic acid ester improves rate performance and reduces internal resistance, even during repeated high-rate charging/discharging, maintaining high capacity and cycle characteristics.

Implementation Method 1

Incorporating a fluorine-containing linear carboxylic acid ester in the electrolytic solution, which forms a Solid Electrolyte Interphase (SEI) film on the base particles

Methodology Applied

Scientific EffectSolid Electrolyte Interphase (SEI) film formation:

Implementation Method 2

The SEI film formed by the fluorine-containing linear carboxylic acid ester improves rate performance and reduces internal resistance, even during repeated high-rate charging/discharging

Methodology Applied

Scientific EffectCrack prevention through film formation:

Implementation Method 3

nonaqueous electrolyte secondary batteries, especially lithium ion secondary batteries

Methodology Applied

Scientific EffectLithium ion conduction: Conduction (electrical)

Data Source

PatentEP3806218B1Secondary battery

Publication Date: 2024.09.04 PANASONIC INTELLECTUAL PROPERTY MANAGEMENT CO LTD

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AI summary

A secondary battery includes a negative electrode containing a lithium silicate phase and silicon particles dispersed in the lithium silicate phase and an electrolytic solution containing a fluorine-containing linear carboxylic acid ester represented by R1-(CO)O-CH2-R2 (wherein R1 is an alkyl group and R2 is an alkyl group in which at least one hydrogen atom is substituted with fluorine).