Fluorinated Ester Electrolyte for Silicon-Lithium Silicate Batteries

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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.

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 causing cracks in base particles

Engineering Contradiction:

Improvebattery capacityVSAvoidrate performance

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

A coating layer is formed on the surface of the silicon particles before battery assembly. This coating layer acts as a preliminary protective structure that prevents cracks from propagating into the base particles during volume fluctuations caused by lithium insertion and extraction, thereby maintaining rate performance while allowing high silicon content for high capacity

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The silicon particles are constructed as composite structures with a core silicon material and a surrounding coating layer. This composite structure combines the high capacity advantage of silicon with the protective function of the coating material, enabling the battery to maintain both high capacity and good rate performance through repeated charging/discharging cycles

Inventive Principle:

Principle #40Composite materials

2Power

If high-rate charging/discharging is performed to improve power output, then the power delivery is improved, but cracks occur in base particles due to volume fluctuations, increasing internal resistance

Engineering Contradiction:

Improvepower deliveryVSAvoidinternal resistance

Core Design Contradiction:

PowerVSObject-affected harmful factors

Solution Approach 1:

The coating layer is applied to silicon particles before battery assembly to provide preliminary protection against crack formation. This protective structure prevents the harmful effect of internal resistance increase during high-rate charging/discharging operations, enabling improved power delivery without the penalty of increased internal resistance

Inventive Principle:

Principle #10Preliminary action

3Use of energy by moving object

If repeated charging/discharging is performed to utilize battery capacity, then the energy utilization is improved, but the rate performance deteriorates due to crack formation and increased internal resistance

Engineering Contradiction:

Improveenergy utilizationVSAvoidrate performance

Core Design Contradiction:

Use of energy by moving objectVSReliability

Solution Approach 1:

The coating layer is formed on silicon particles before battery assembly to provide preliminary protection against crack formation during repeated charging/discharging cycles. This protective structure maintains rate performance while allowing full utilization of battery capacity over extended cycling

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The coating layer acts as a cushioning layer that absorbs and distributes the mechanical stress from volume fluctuations before they can propagate into the base silicon particles. This beforehand cushioning prevents crack formation and maintains rate performance during repeated energy utilization cycles

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

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 the rate performance of the secondary battery by reducing transfer resistance and preventing the deterioration of capacity during repeated charging/discharging.

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:

Data Source

PatentUS11894521B2Secondary battery

Publication Date: 2024.02.06 PANASONIC INTELLECTUAL PROPERTY MANAGEMENT CO LTD

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).