Organic Electrolytic Solution for Lithium Battery SEI Stability

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Solution Overview

Problem

Conventional lithium batteries experience swelling and reduced performance due to the decomposition of organic solvents, leading to unstable solid electrolyte interfaces (SEI) and increased internal pressure, which affects battery reliability and safety.

Innovation Solution

An organic electrolytic solution comprising a lithium salt, a high dielectric constant solvent, a low boiling point solvent, and a specific compound that reacts with the anode surface to form a stable SEI film, preventing decomposition and swelling by enhancing adhesion and density of the SEI film.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a conventional organic electrolytic solution is used, then the battery can operate with good initial performance, but the battery swells and performance degrades over time due to SEI decomposition

Engineering Contradiction:

Improvebattery reliabilityVSAvoidSEI film stability

Core Design Contradiction:

ReliabilityVSStability of the object's composition

Solution Approach 1:

The patent modifies the chemical composition parameters of the electrolytic solution by introducing a cyclic carboxylate compound with specific structural parameters (formula 1 where n=1-4). This changes the SEI formation mechanism and composition, creating a more stable interface that resists decomposition during battery operation and storage.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent creates a composite SEI film structure by combining the conventional electrolyte components (lithium salt, carbonate solvents) with the cyclic carboxylate additive. This composite approach results in a multi-layered or heterogeneous SEI structure that provides both initial performance and long-term stability.

Inventive Principle:

Principle #40Composite materials

2Temperature

If the battery is stored at high temperatures, then thermal energy increases, but the passivation layer breaks down and gas generation increases

Engineering Contradiction:

Improvestorage temperatureVSAvoidgas generation

Core Design Contradiction:

TemperatureVSObject-generated harmful factors

Solution Approach 1:

The cyclic carboxylate compound performs preliminary protective action by forming a robust SEI film during initial charging cycles. This pre-formed protective layer acts as a barrier that prevents further electrolyte decomposition and gas generation even when the battery is subsequently exposed to high storage temperatures.

Inventive Principle:

Principle #9Preliminary anti-action

Solution Approach 2:

The patent uses a small amount of cyclic carboxylate additive (0.1-5 wt%) that sacrificially decomposes during initial cycles to form the stable SEI layer. This small consumable amount of additive protects the bulk electrolyte from decomposition throughout the battery's operational life.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

3Stress or pressure

If internal pressure increases due to gas generation, then battery deformation occurs, but mounting becomes difficult

Engineering Contradiction:

Improveinternal pressureVSAvoidmounting ease

Core Design Contradiction:

Stress or pressureVSEase of manufacture

Solution Approach 1:

The patent converts the potentially harmful gas generation process into a beneficial outcome by controlling it to occur primarily during initial SEI formation rather than during storage. The controlled decomposition of the cyclic carboxylate additive during charging creates the desired SEI film while minimizing harmful gas accumulation that would cause swelling and mounting difficulties.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

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 ensures stable charge/discharge cycles, maintains battery thickness, and improves reliability by suppressing electrolyte decomposition and swelling, resulting in enhanced battery performance and safety.

Implementation Method 1

a compound which reacts with an anode surface to form a stable solid electrolyte interface (SEI) film

Methodology Applied

Scientific EffectSEI film formation:

Implementation Method 2

the SEI film acts as an ion tunnel through which only lithium ions pass and solvates lithium ions

Methodology Applied

Scientific EffectIon transport:

Implementation Method 3

solvates lithium ions to prevent cointercalation of an organic solvent, which moves with the lithium ions, into a carbon anode

Methodology Applied

Scientific EffectSolvation: Solvation

Data Source

PatentUS7494745B2Organic electrolytic solution and lithium battery employing the same

Publication Date: 2009.02.24 SAMSUNG SDI CO LTD

AI summary

An organic electrolytic solution and a lithium battery employing the same are provided. The organic electrolytic solution includes: a lithium salt; an organic solvent containing a high dielectric constant solvent and a low boiling point solvent; and a carbonate or oxalate derivative having at least one substituted or unsubstituted cyano group. The organic electrolytic solution and the lithium battery employing the same have improved reductive decomposition stability, thereby decreasing an irreversible capacity after a first cycle and improving the charge/discharge efficiency and lifespan of the battery. The lithium battery has non-varying chemical properties at room temperature and a uniform thickness after standard charging, and thus has high reliability.