Layered Positive Electrode With Melamine Thermal Shutdown

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Solution Overview

Problem

Rechargeable lithium batteries face challenges in achieving high voltage while minimizing energy density reduction and ensuring safety and reliability, particularly in high-voltage applications such as electric vehicles.

Innovation Solution

A positive electrode for rechargeable lithium batteries is designed with a first active material layer containing a melamine-based compound and a second active material layer, where the first active material includes compounds like lithium iron phosphate, and the melamine-based compound acts as a safety functional layer to block lithium ion and electron flow during thermal exposure or impact, thereby preventing overheating and explosion.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Power

If high-voltage active materials are used to increase battery voltage, then power and energy density are improved, but thermal safety and reliability deteriorate due to increased risk of overheating and explosion

Engineering Contradiction:

Improvebattery voltageVSAvoidthermal safety

Core Design Contradiction:

PowerVSReliability

Solution Approach 1:

The positive electrode is segmented into multiple layers: a first active material layer containing lithium iron phosphate and a melamine-based compound, and a second active material layer containing a second active material. This segmentation allows different materials to serve different functions, with the first layer providing thermal safety through the melamine-based compound while the second layer contributes to high voltage and capacity.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The melamine-based compound acts as an intermediary substance in the first active material layer. It serves as a safety functional component that blocks lithium ion and electron flow during thermal exposure or impact, preventing overheating and explosion while allowing normal battery operation when not exposed to adverse conditions.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Power

If high-voltage active materials are used to increase battery voltage, then power is improved, but energy density reduction increases

Engineering Contradiction:

Improvebattery voltageVSAvoidenergy density reduction

Core Design Contradiction:

PowerVSLoss of energy

Solution Approach 1:

The positive electrode uses composite materials comprising a first active material layer with lithium iron phosphate and a melamine-based compound, combined with a second active material layer containing a second active material. This composite structure achieves high voltage through the second active material while the first active material layer with lithium iron phosphate helps maintain energy density and provides thermal safety.

Inventive Principle:

Principle #40Composite materials

3Reliability

If safety functional layers are added to block current flow during thermal exposure, then thermal safety is improved, but device complexity increases

Engineering Contradiction:

Improvethermal safetyVSAvoidelectrode structure complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The safety functional capability is merged into the first active material layer by combining lithium iron phosphate with a melamine-based compound in the same layer. This integration allows the first layer to serve both as an active material layer and as a safety layer, blocking lithium ion and electron flow during thermal exposure or impact without requiring a separate safety layer structure.

Inventive Principle:

Principle #5Merging (Combining)

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 realizes high voltage, minimizes energy density reduction, and enhances safety and reliability of the battery by effectively blocking current flow during adverse conditions while maintaining normal battery performance.

Implementation Method 1

the melamine-based compound acts as a safety functional layer to block lithium ion and electron flow during thermal exposure or impact

Methodology Applied

Scientific EffectIon blocking:

Implementation Method 2

the melamine-based compound acts as a safety functional layer to block lithium ion and electron flow during thermal exposure or impact

Methodology Applied

Scientific EffectElectron flow blocking:

Data Source

PatentUS20230335714A1Positive electrode for rechargeable lithium battery and rechargeable lithium battery comprising the same

Publication Date: 2023.10.19 SAMSUNG SDI CO LTD

AI summary

The present invention relates to a positive electrode for a rechargeable lithium battery, and a rechargeable lithium battery including the same. The positive electrode for the rechargeable lithium battery includes a current collector; a first active material layer disposed on the current collector and including a first active material and a melamine-based compound; and a second active material layer disposed on the first active material layer and including a second active material, wherein the first active material and the second active material are different from each other, and the first active material includes at least one of the compounds represented by Chemical Formulas 1 to 4.(The definitions of Chemical Formulas 1 to 4 are the same as described in the specification.)