Composite Oxide-Sulfide Solid Electrolyte for Lithium Sulfur Batteries

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Solution Overview

Problem

Current lithium sulfur batteries face limitations due to polysulfide shuttle phenomenon in liquid electrolytes, leading to decreased columbic efficiency and electrode degradation, as well as safety concerns with metallic lithium anodes, while solid electrolytes struggle with poor ionic conductivity and stability when used in batteries.

Innovation Solution

A solid electrolyte for lithium sulfur batteries is created by embedding lithium ion conducting oxide particles, such as Li7La3Zr2O12 (LLZO), within a lithium ion conducting sulfide composition, specifically β-Li3PS4 (LPS), forming a core-shell structure to enhance ionic conductivity and compatibility with metallic lithium anodes.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If solid electrolytes are used to prevent polysulfide migration and dendrite penetration, then battery safety and stability are improved, but ionic conductivity decreases significantly

Engineering Contradiction:

Improvebattery safetyVSAvoidionic conductivity

Core Design Contradiction:

ReliabilityVSQuantity of substance

Solution Approach 1:

The patent employs a composite solid electrolyte system combining oxide particles (LLZO, LTO, or LATO) dispersed in a sulfide electrolyte matrix (LPS). This composite structure integrates the high safety and stability of oxides with the high ionic conductivity of sulfides, achieving both improved reliability and maintained ionic conductivity. The oxide particles act as stable nuclei that prevent polysulfide migration while the sulfide matrix provides efficient lithium ion transport pathways.

Inventive Principle:

Principle #40Composite materials

2Quantity of substance

If high ionic conductivity solid electrolytes are used, then battery performance is improved, but compatibility with metallic lithium anodes deteriorates

Engineering Contradiction:

Improveionic conductivityVSAvoidelectrochemical stability

Core Design Contradiction:

Quantity of substanceVSStability of the object's composition

Solution Approach 1:

The patent applies local quality by distributing oxide particles with different compositions (LLZO, LTO, or LATO) throughout the sulfide electrolyte matrix. These oxide particles create localized regions of high electrochemical stability that interface with the metallic lithium anode, protecting the bulk sulfide electrolyte from degradation while maintaining overall high ionic conductivity through the sulfide matrix.

Inventive Principle:

Principle #3Local quality

3Quantity of substance

If conventional liquid electrolytes are used, then ionic conductivity is maintained, but polysulfide migration and electrode degradation occur

Engineering Contradiction:

Improveionic conductivityVSAvoidpolysulfide shuttle phenomenon

Core Design Contradiction:

Quantity of substanceVSObject-generated harmful factors

Solution Approach 1:

The solid composite electrolyte acts as an intermediary medium between the lithium anode and sulfur cathode. The oxide particles within the composite structure serve as physical barriers that block polysulfide migration, while the sulfide matrix provides continuous pathways for lithium ion transport. This intermediary structure eliminates the polysulfide shuttle phenomenon while maintaining efficient ionic conductivity.

Inventive Principle:

Principle #24Intermediary (Mediator)

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 composite electrolyte achieves improved ionic conductivity, electrochemical stability, and reduced interfacial resistance, enabling efficient lithium-ion transport and extended cyclability, thus overcoming the limitations of both liquid and solid electrolytes in lithium sulfur batteries.

Implementation Method 1

The conductivity of the lithium ion conducting oxide composition is at least 1.0×10−8 S/cm. The conductivity of the lithium ion conducting sulfide composition is at least 1.0×10−8 S/cm.

Methodology Applied

Scientific EffectIonic conduction: Conduction (electrical)

Implementation Method 2

The composite electrolyte has lower interfacial resistance with the electrodes than either of the parent electrolytes alone.

Methodology Applied

Scientific EffectInterfacial charge transfer: Electrochemiluminescence

Data Source

PatentUS9548512B2High conducting oxide—sulfide composite lithium superionic conductor

Publication Date: 2017.01.17 UT BATTELLE LLC

AI summary

A solid electrolyte for a lithium-sulfur battery includes particles of a lithium ion conducting oxide composition embedded within a lithium ion conducting sulfide composition. The lithium ion conducting oxide composition can be Li7La3Zr2O12 (LLZO). The lithium ion conducting sulfide composition can be β-Li3PS4 (LPS). A lithium ion battery and a method of making a solid electrolyte for a lithium ion battery are also disclosed.