LATP Separator Interface for Thermally Stable Lithium Secondary Batteries

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Solution Overview

Problem

Lithium secondary batteries face challenges with poor thermal stability and coulomb efficiency due to the irreversible phase formation of silicon-based materials, leading to explosive reactions during thermal runaway.

Innovation Solution

A lithium secondary battery design incorporating a positive electrode, negative electrode, and separator structure with an oxide-based solid electrolyte layer containing lithium aluminum titanium phosphate (LATP), where an inorganic layer with a reduced LATP product and SEI material is formed at the interface, enhancing thermal safety and coulomb efficiency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If Si-based material is used as negative electrode active material to increase energy density, then capacity is improved, but thermal stability deteriorates due to explosive reaction during thermal runaway

Engineering Contradiction:

ImprovecapacityVSAvoidthermal stability

Core Design Contradiction:

Quantity of substanceVSObject-affected harmful factors

Solution Approach 1:

An oxide-based solid electrolyte layer is introduced as an intermediary between the Si-based negative electrode and the electrolyte. This solid electrolyte layer acts as a physical and chemical barrier that prevents direct contact and explosive reactions between the Si-based material and electrolyte during thermal runaway, while still allowing Li ion transport to maintain high capacity.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The negative electrode is designed as a composite structure combining Si-based active material with carbon-based material. This composite approach maintains the high capacity advantage of Si-based materials while the carbon component provides thermal stability and structural integrity during thermal events.

Inventive Principle:

Principle #40Composite materials

2Productivity

If pre-lithiation process is applied to compensate irreversible reactions, then coulomb efficiency is improved, but thermal safety deteriorates due to poor thermal stability of SEI

Engineering Contradiction:

Improvecoulomb efficiencyVSAvoidthermal safety

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The oxide-based solid electrolyte layer serves as an intermediary that replaces the conventional liquid electrolyte interface. It enables the formation of a stable SEI layer during pre-lithiation while preventing the poor thermal stability issues associated with conventional liquid electrolyte-based SEI, as the solid electrolyte itself provides thermal stability.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Ease of manufacture

If conventional liquid electrolyte is used, then manufacturing simplicity is maintained, but thermal safety deteriorates due to explosive reaction during thermal runaway

Engineering Contradiction:

Improvemanufacturing simplicityVSAvoidthermal safety

Core Design Contradiction:

Ease of manufactureVSObject-affected harmful factors

Solution Approach 1:

The liquid electrolyte is extracted from the immediate interface between the negative electrode and electrolyte bulk, replaced by a solid electrolyte layer. This extraction eliminates the flammable liquid component from the critical reaction zone while maintaining overall battery manufacturability through established solid electrolyte deposition techniques.

Inventive Principle:

Principle #2Taking out (Extraction)

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 design improves thermal safety and coulomb efficiency by forming a high F-content inorganic layer, reducing resistance and stabilizing the SEI, thereby enhancing the battery's output characteristics.

Implementation Method 1

an inorganic layer containing a reduced product of the LATP and an SEI material is formed at an interface between the oxide-based solid electrolyte layer and the negative electrode active material layer

Methodology Applied

Scientific EffectReduction: Reduction

Implementation Method 2

Methodology Applied

Scientific EffectSEI formation:

Data Source

PatentEP4672474A1Lithium secondary battery with excellent thermal stability, and manufacturing method therefor

Publication Date: 2025.12.31 LG ENERGY SOLUTION LTD

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AI summary

According to an embodiment of the present disclosure, there is provided a lithium secondary battery comprising: a positive electrode which includes a positive electrode current collector, and a positive electrode active material layer formed on one side or both sides of the positive electrode current collector, a negative electrode which includes a negative electrode current collector, and a negative electrode active material layer formed on one side or both sides of the negative electrode current collector, and a separator which includes a substrate, and an oxide-based solid electrolyte layer formed on one side or both sides of the substrate and including lithium aluminum titanium phosphate(LATP), wherein the negative electrode active material layer and the oxide-based solid electrolyte layer face each other, wherein an inorganic layer containing a reduced product of the LATP and an SEI material is formed at an interface between the oxide-based solid electrolyte layer and the negative electrode active material layer, and wherein the atom content of F in the inorganic layer is included at 7 to 15 atomic percent(%) based on all atoms present in the inorganic layer.