Nitrile Electrolyte Composition for Stable Lithium Metal SEI

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Solution Overview

Problem

Lithium metal secondary batteries face issues with high reactivity leading to solid electrolyte interphase (SEI) layer instability, lithium dendrite growth, and safety risks due to the formation of a mechanically weak and chemically unstable SEI layer, which reduces battery lifespan and poses safety hazards.

Innovation Solution

An electrolytic solution with a nitrile solvent containing a compound represented by formula (1) is used, where L is selected from C(R1R2), O, Si(R3R4), B(R5), P(R6R7R8), or N(R9), and R1-R9 are independently selected to reduce reactivity, enhancing redox stability and solubility, and includes a film-forming additive to create a dense SEI film.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If lithium metal is used as the negative electrode to achieve high energy density, then the energy density is improved, but the reactivity increases leading to SEI layer instability and safety risks

Engineering Contradiction:

Improveenergy densityVSAvoidSEI layer stability

Core Design Contradiction:

Use of energy by moving objectVSReliability

Solution Approach 1:

The patent introduces a fluorinated cyclic carbonate compound as an intermediary substance between lithium metal and the conventional electrolyte. This compound preferentially reacts with lithium metal to form a stable SEI layer that acts as a protective barrier, preventing direct contact between lithium metal and the conventional electrolyte, thus reducing reactivity while maintaining high energy density

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent modifies the chemical composition parameters of the electrolyte by incorporating fluorinated cyclic carbonate compounds with specific molecular structures (containing F, C, O atoms in cyclic carbonate groups). This parameter change alters the electrochemical properties of the electrolyte system, enabling formation of stable SEI layers with different stability characteristics compared to conventional electrolytes

Inventive Principle:

Principle #35Parameter changes

2Quantity of substance

If conventional electrolytes are used to maintain good solubility, then the solubility is improved, but the redox stability decreases leading to corrosion on positive electrode metal

Engineering Contradiction:

ImprovesolubilityVSAvoidredox stability

Core Design Contradiction:

Quantity of substanceVSStability of the object's composition

Solution Approach 1:

The patent creates a composite electrolyte system combining fluorinated cyclic carbonate compounds with conventional carbonate solvents (EC, PC, DMC, DEC). This composite approach leverages the high solubility of conventional carbonates while the fluorinated cyclic carbonate component provides redox stability through formation of protective SEI layers, achieving both solubility and stability requirements

Inventive Principle:

Principle #40Composite materials

3Reliability

If the SEI layer is formed to protect lithium metal, then the protection is improved, but the mechanical strength and chemical stability of the SEI layer are reduced

Engineering Contradiction:

ImproveprotectionVSAvoidSEI layer mechanical strength

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The patent changes the chemical composition parameters of the SEI layer by introducing fluorinated cyclic carbonate compounds. The fluorination and cyclic carbonate structure lead to formation of SEI layers with different physical-chemical properties, specifically improving chemical stability through strong Li-F bonds while maintaining adequate mechanical strength for protection

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 solution reduces corrosion on the positive electrode metal, improves cycle performance, and enhances the stability and longevity of lithium metal secondary batteries.

Implementation Method 1

the compound represented by formula (1) with the specific structure described above not only exhibits good solubility for electrolyte salts

Methodology Applied

Scientific EffectSolvation: Solvation

Implementation Method 2

the lithium metal negative electrode in lithium-metal secondary batteries exhibits high reactivity and readily reacts with the electrolyte. This leads to the formation of a solid electrolyte interphase (SEI) layer

Methodology Applied

Scientific EffectElectrochemical reaction: Electrolysis

Data Source

PatentUS20260018672A1Electrolyte, secondary battery, and electric device

Publication Date: 2026.01.15 CONTEMPORARY AMPEREX TECHNOLOGY CO LTD

AI summary

An electrolyte, a secondary battery, and an electric device. The electrolyte comprises a component, a nitrile solvent. The nitrile solvent comprises a compound represented by formula (1): wherein: L is selected from any one of C(R1R2), O, Si(R3R4), B(R5), P(R6R7R8), and N(R9); R1-R9 are each independently selected from at least one of H, halogen, substituted or unsubstituted alkyl having 1-3 carbon atoms, alkoxy having 1-3 carbon atoms, amino, and cyano, and R1 and R2 are not cyanos and H; R11 is an alkane chain containing 1-4 carbon atoms; R12-R14 are each independently selected from at least one of H, halogen, substituted or unsubstituted alkyl having 1-3 carbon atoms, alkoxy having 1-3 carbon atoms, amino, and cyano; and when L is C(R1R2), R12-R14 are not cyanos.