Lithium Iron Phosphate Composite Coating for Thermal Safety

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Solution Overview

Problem

Rechargeable lithium batteries face safety concerns due to potential explosions from internal short circuits and thermal runaway, particularly due to high electrical energy storage and low heat-generating safety materials like lithium iron phosphate, which compromise capacity and stability.

Innovation Solution

A rechargeable lithium battery design incorporating a positive electrode with a composite oxide of cobalt, manganese, or nickel and lithium, along with a second active material represented by Chemical Formula LiaMxFe1-xPO4, and a negative electrode with flake-shaped polyethylene particles, enhancing safety and capacity retention at high voltages.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If lithium iron phosphate is used as a safety material, then thermal safety is improved, but capacity decreases

Engineering Contradiction:

Improvethermal safetyVSAvoidcapacity

Core Design Contradiction:

ReliabilityVSQuantity of substance

Solution Approach 1:

The patent uses a composite positive active material comprising lithium iron phosphate particles and a coating layer containing lithium nickel cobalt aluminum oxide and/or lithium nickel cobalt manganese oxide. This composite structure allows the core LFP material to provide thermal safety while the coating layer contributes higher capacity and voltage, resolving the contradiction between safety and capacity.

Inventive Principle:

Principle #40Composite materials

2Productivity

If high voltage is used to increase energy density, then productivity is improved, but safety deteriorates

Engineering Contradiction:

Improveenergy densityVSAvoidsafety

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent modifies the voltage parameter by using a composite material that enables operation at higher voltages (4.0V or higher) compared to conventional LFP batteries. The coating layer of lithium nickel cobalt aluminum oxide and/or lithium nickel cobalt manganese oxide allows the battery to achieve higher energy density through increased voltage without sacrificing the inherent thermal stability of the LFP core structure.

Inventive Principle:

Principle #35Parameter changes

3Use of energy by moving object

If internal short circuit occurs, then electrical energy is released rapidly, but this causes explosion

Engineering Contradiction:

Improveelectrical energy storageVSAvoidexplosion risk

Core Design Contradiction:

Use of energy by moving objectVSObject-affected harmful factors

Solution Approach 1:

The patent applies beforehand cushioning by coating the lithium iron phosphate particles with a protective layer of lithium nickel cobalt aluminum oxide and/or lithium nickel cobalt manganese oxide before battery assembly. This pre-established protective barrier prevents direct exposure and rapid energy release in case of internal short circuits, cushioning against the harmful effects while maintaining high energy storage capacity.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

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 provides improved thermal and physical stability, maintaining high capacity and safety at high voltages, reducing the risk of explosions and enhancing energy density, while effectively shutting down electrical/chemical reactions during thermal runaway.

Implementation Method 1

a negative electrode functional layer having generally flake-shaped polyethylene particles at least partially disposed on the negative active material layer

Methodology Applied

Scientific EffectMelting: Melting

Implementation Method 2

the positive active material layer includes a first positive active material having at least one of a composite oxide of a metal selected from cobalt, manganese, nickel, and a combination thereof and lithium, and a second positive active material having a compound represented by Chemical Formula 1: LiaMxFe1-xPO4

Methodology Applied

Scientific EffectElectrochemical reaction: Redox Reactions

Data Source

PatentUS11515523B2Rechargeable lithium battery

Publication Date: 2022.11.29 SAMSUNG SDI CO LTD

AI summary

A rechargeable lithium battery includes a positive electrode having a positive current collector and a positive active material layer at least partially disposed on the positive current collector, wherein the positive active material layer includes a first positive active material having at least one of a composite oxide of a metal selected from cobalt, manganese, nickel, and a combination thereof and lithium, and a second positive active material having a compound represented by Chemical Formula 1 as defined herein, and a negative electrode having a negative current collector, a negative active material layer at least partially disposed on the negative current collector, and a negative electrode functional layer having generally flake-shaped polyethylene particles at least partially disposed on the negative active material layer.