Dual-Electrolyte LFP Solid-State Cell for Stable Cathode Interfaces

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Solution Overview

Problem

Lithium iron phosphate (LFP) cathode active materials exhibit poor electrochemical compatibility with commonly-used sulfide electrolytes, leading to increased interfacial resistance and reduced cycle life in all-solid-state battery cells.

Innovation Solution

Incorporating a chloride-based solid electrolyte in the cathode active material layer and a dual-electrolyte separator with a sulfide-based sublayer adjacent to the anode and a chloride-based sublayer adjacent to the cathode, preventing direct contact between LFP and sulfide electrolytes, thereby enhancing interfacial compatibility and stability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Power

If LFP cathode active material is used with sulfide-based solid electrolyte, then the battery cell can achieve high energy density and fast charging capability, but the interfacial resistance increases and cycle life decreases due to poor electrochemical compatibility

Engineering Contradiction:

Improvefast charging capabilityVSAvoidcycle life

Core Design Contradiction:

PowerVSReliability

Solution Approach 1:

The separator is divided into two distinct sublayers: a first sublayer containing sulfide-based solid electrolyte adjacent to the anode, and a second sublayer containing chloride-based solid electrolyte adjacent to the LFP cathode. This segmentation allows each sublayer to perform its specialized function - the sulfide sublayer enables fast charging while the chloride sublayer ensures long cycle life, resolving the contradiction between power and reliability

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The chloride-based solid electrolyte in the second sublayer acts as an intermediary barrier between the LFP cathode active material and the sulfide-based solid electrolyte in the first sublayer. This intermediary prevents direct harmful contact between incompatible materials while maintaining ionic conductivity, thereby preserving cycle life without sacrificing fast charging capability

Inventive Principle:

Principle #24Intermediary (Mediator)

2Device complexity

If LFP cathode active material is used with sulfide-based solid electrolyte, then the battery cell structure is simplified, but the interfacial compatibility deteriorates leading to increased resistance

Engineering Contradiction:

Improvebattery structure complexityVSAvoidinterfacial compatibility

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

Rather than using a single uniform electrolyte layer, the invention segments the separator into two specialized sublayers with different electrolyte compositions. This segmentation resolves the contradiction by allowing the chloride sublayer to provide interfacial compatibility with LFP while the sulfide sublayer maintains structural simplicity and enables high conductivity

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The separator employs a composite structure combining two different solid electrolyte materials - sulfide-based and chloride-based - in distinct sublayers. This composite approach allows the system to simultaneously achieve the benefits of both materials: high ionic conductivity from sulfide and excellent interfacial compatibility from chloride, overcoming the limitations of using either material alone

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 dual-electrolyte design achieves stable cycling with over 400 cycles and 89% capacity retention by maintaining favorable particle-to-particle and layer-to-layer interfaces, improving the performance of all-solid-state battery cells.

Implementation Method 1

Lithium iron phosphate (LFP) cathode active materials exhibit poor electrochemical compatibility with commonly-used sulfide electrolytes

Methodology Applied

Scientific EffectElectrochemical compatibility:

Implementation Method 2

Each of the S separators includes a first sublayer including a sulfide-based solid electrolyte arranged adjacent to one of the A anode electrodes; and a second sublayer including a chloride-based solid electrolyte arranged between the first sublayer and one of the C cathode electrodes

Methodology Applied

Scientific EffectIon conduction: Conduction (electrical)

Data Source

PatentUS20250286120A1Stable LFP-based all-solid-state battery cell

Publication Date: 2025.09.11 GM GLOBAL TECHNOLOGY OPERATIONS LLC

AI summary

A battery cell includes C cathode electrodes each including a cathode active material layer arranged on a cathode current collector; A anode electrodes each including an anode active material layer arranged on an anode current collector; and S separators, where C, A and S are integers greater than one. Each of the S separators includes a first sublayer including a sulfide-based solid electrolyte arranged adjacent to one of the A anode electrodes, and a second sublayer including a chloride-based solid electrolyte arranged between the first sublayer and one of the C cathode electrodes.