Li3PO4-Coated Li-NMC Cathodes for Water-Stable Aqueous Processing

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Solution Overview

Problem

Existing methods for coating lithium nickel manganese cobalt (Li-NMC) cathode active materials with Li3PO4 result in uneven and water-unstable coatings, limiting the use of water-based electrode fabrication and increasing health and environmental hazards due to the need for organic solvents.

Innovation Solution

A method involving mixing a lithium intercalation cathode active material with a phosphate source and a C2-C6 carboxylic acid, followed by calcination at 300-800°C, to form a uniform and water-stable Li3PO4 coating directly from residual lithium on the material's surface, reducing residual lithium and enhancing coating stability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If Li-NMC is coated with Li3PO4 using known methods, then electrical and ionic conductivity properties are improved, but the coating becomes uneven and inhomogeneous

Engineering Contradiction:

Improveelectrical and ionic conductivityVSAvoidcoating uniformity

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The patent uses a slurry comprising water, binder, and conductive additive as an intermediary medium to deliver Li3PO4 coating material uniformly onto the Li-NMC surface. This slurry system ensures homogeneous distribution of coating precursors, which then convert to uniform Li3PO4 coating upon heating, resolving the contradiction between achieving good conductivity and maintaining coating uniformity

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent controls the heating temperature range (specifically maintaining below 100°C during slurry application and then controlled heating to convert coating precursors) to ensure uniform coating formation without premature decomposition or uneven crystallization, thereby achieving both good conductivity and uniform coating morphology

Inventive Principle:

Principle #35Parameter changes

2Reliability

If Li3PO4 coating is applied to Li-NMC, then conductivity is improved, but water stability deteriorates

Engineering Contradiction:

Improveelectrical and ionic conductivityVSAvoidwater stability

Core Design Contradiction:

ReliabilityVSStability of the object's composition

Solution Approach 1:

The patent employs a water-based slurry as an intermediary delivery system that allows uniform application of coating precursors without direct contact between Li3PO4 and water during processing. The coating is formed in situ upon controlled heating, preventing water-induced degradation while maintaining the desired conductivity enhancement

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent applies coating precursors uniformly onto the Li-NMC surface before any water exposure occurs during subsequent battery assembly or operation. This preliminary coating application ensures that the Li3PO4 layer is already in place to protect the Li-NMC from water, thereby achieving both conductivity improvement and water stability

Inventive Principle:

Principle #10Preliminary action

3Object-affected harmful factors

If water-based electrode fabrication is used, then health and environmental hazards are reduced, but coating stability deteriorates due to poor water stability of Li3PO4

Engineering Contradiction:

Improvehealth and environmental hazardsVSAvoidcoating stability in water

Core Design Contradiction:

Object-affected harmful factorsVSStability of the object's composition

Solution Approach 1:

The patent uses a water-based slurry comprising binder and conductive additive as an intermediary vehicle to deliver coating precursors uniformly onto Li-NMC. The slurry matrix protects the coating precursors from direct water interaction during mixing and application, enabling stable aqueous processing while maintaining coating integrity through controlled heating that converts precursors to stable Li3PO4

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent carefully controls the temperature parameters during and after slurry application, maintaining temperatures below 100°C during wet processing and then applying controlled heating to convert coating precursors to stable Li3PO4. This parameter control enables water-based fabrication while achieving coating stability, as the Li3PO4 forms after water exposure rather than during it

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 approach results in a water-stable cathode active material with improved electrochemical performance, reduced internal resistance, higher charge and discharge rates, and prolonged battery lifetime, while allowing for environmentally friendly aqueous electrode fabrication.

Implementation Method 1

mixing a lithium intercalation cathode active material; a phosphate source; a C2-C6 carboxylic acid... calcining the mixture at 300-800°C

Methodology Applied

Scientific EffectChemical reaction: Chemical Bonding

Implementation Method 2

calcining the mixture at 300-800°C

Methodology Applied

Scientific EffectHeating: Heating

Data Source

PatentEP4456171A1Coated cathode active material and process for making the same

Publication Date: 2024.10.30 NORTHVOLT AB

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AI summary

The disclosure provides a coated lithium intercalation cathode active material that is water-stable, and a method of forming said coated cathode active material. In particular, the coated cathode active material comprises an Li3PO4 coating. The coated cathode active material of the disclosure is suitable for use in aqueous electrode fabrication method.