Nonaqueous Electrolyte Additives for Battery Cycle Stability

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Solution Overview

Problem

Lithium nonaqueous electrolyte secondary batteries face challenges in achieving a balance of high performance across durability, capacity, resistance, and output characteristics, particularly at high temperatures, with existing solutions trading off between these factors.

Innovation Solution

A nonaqueous electrolyte battery design incorporating a positive electrode and negative electrode capable of occluding and releasing metal ions, with a nonaqueous electrolyte solution containing compounds like fluorosulfonyl structures, difluorophosphates, and isocyanate compounds, and a negative electrode active material comprising metal particles alloying with Li and graphite particles.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If high-activity positive and negative electrodes are used to increase capacity, then energy density is improved, but side reactions between electrodes and electrolyte increase, reducing charge/discharge capacity

Engineering Contradiction:

ImprovecapacityVSAvoidcharge/discharge capacity

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

The patent applies preliminary action by introducing a film-forming electrolyte additive that reacts first during initial charging cycles to form a stable solid electrolyte interface (SEI) film on the electrode surface. This pre-formed protective layer prevents subsequent side reactions between the high-activity electrodes and the main electrolyte, thus preserving charge/discharge capacity while maintaining high capacity electrodes

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent uses an intermediary substance (film-forming electrolyte additive) that mediates between the high-activity electrodes and the electrolyte. This additive forms a protective interface layer that acts as an intermediary barrier, allowing lithium ion transport while preventing direct contact and harmful side reactions between the electrodes and electrolyte

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If conventional electrolyte additives are used to improve high-temperature storage characteristics, then durability is improved, but capacity and output characteristics deteriorate

Engineering Contradiction:

Improvehigh-temperature storage characteristicsVSAvoidoutput characteristics

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The patent applies parameter changes by carefully controlling the concentration of the film-forming electrolyte additive within a specific range (0.01-5% by mass). This optimized concentration ensures sufficient protective film formation for high-temperature stability while maintaining adequate ionic conductivity and avoiding excessive resistance that would harm output characteristics

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent uses a composite electrolyte system combining the film-forming additive with conventional electrolyte components (lithium salt and carbonate solvents). This composite approach integrates the protective film-forming function with the ionic conductivity function, achieving both high-temperature durability and good output characteristics through synergistic material combination

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 solution enhances the battery's balance of general performance, suppressing capacity loss and battery expansion during charge/discharge cycles, while improving high-temperature storage and cycle characteristics.

Implementation Method 1

an attempt has been made to add an isocyanate compound to a nonaqueous electrolyte solution to improve the battery in cycle characteristics

Methodology Applied

Scientific EffectFilm formation: Deposition (physical)

Implementation Method 2

the negative electrode has a negative electrode active material containing metal particles capable of alloying with Li and graphite particles

Methodology Applied

Scientific EffectAlloying: Solid Solution Strengthening

Implementation Method 3

nonaqueous electrolyte solutions obtained by dissolving an electrolyte, such as LiPF6, LiBF4, LiN(CF3SO2)2, or LiCF3(CF2)3SO3, in a mixed solvent of a high dielectric constant solvent, such as ethylene carbonate or propylene carbonate, and a low viscosity solvent, such as dimethyl carbonate, diethyl carbonate, or ethylmethyl carbonate

Methodology Applied

Scientific EffectDissolution: Solvation

Data Source

PatentUS9947965B2Nonaqueous electrolyte solution and nonaqueous electrolyte battery using same

Publication Date: 2018.04.17 MU IONIC SOLUTIONS CORP

AI summary

The object of the present invention is to provide a nonaqueous electrolyte secondary battery which has excellent balance of general performance with respect to performance including durability, capacity, resistance, and output characteristics. Provided is a nonaqueous electrolyte battery comprising a positive electrode and a negative electrode each being capable of occluding and releasing metal ions, and a nonaqueous electrolyte solution, wherein the nonaqueous electrolyte solution contains an electrolyte, a nonaqueous solvent, and at least one compound selected from the group consisting of a compound having a fluorosulfonyl structure (—SO2F), a difluorophosphate, and an isocyanate compound, and wherein the negative electrode has a negative electrode active material containing metal particles capable of alloying with Li and graphite particles.