Fluorine-Coated Lithium Transition Metal Oxide Cathode

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Solution Overview

Problem

Conventional lithium secondary batteries face challenges in increasing capacity while operating at high voltages due to performance deterioration, shortened lifespan, and side reactions, which affect battery safety and efficiency.

Innovation Solution

A cathode active material comprising a lithium transition metal oxide with most fluorine on its surface and incorporating metals like Mg, Ti, Zr, Al, and Fe, along with sulfur, which allows for high voltage operation without structural collapse or electrolyte reactions, enhancing capacity and cycle life.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If charge voltage is continuously maintained in a high voltage state to increase capacity, then battery capacity increases, but side reactions occur (electrolyte pyrolysis, cathode oxidation, pyrolysis of cathode active material) causing performance deterioration and shortened lifespan

Engineering Contradiction:

Improvebattery capacityVSAvoidbattery lifespan and safety

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

A fluorine-containing coating layer is introduced as an intermediary between the cathode active material and the electrolyte. This coating layer acts as a protective barrier that prevents direct contact and harmful side reactions between the high-voltage cathode material and the electrolyte, enabling stable operation at 4.4V or higher while maintaining battery lifespan and safety

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The cathode active material is designed as a composite structure containing fluorine, sulfur, and at least one metal element (Mg, Ti, Zr, Al, or Fe) alongside the transition metal oxide. This composite composition enhances structural stability at high voltage and provides multiple protective mechanisms against degradation and side reactions

Inventive Principle:

Principle #40Composite materials

2Quantity of substance

If conventional cathode active materials are used at high voltage, then battery capacity increases, but structural stability deteriorates leading to performance degradation

Engineering Contradiction:

Improvebattery capacityVSAvoidcathode material structural stability

Core Design Contradiction:

Quantity of substanceVSStability of the object's composition

Solution Approach 1:

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

Fluorine is strategically positioned in the cathode active material structure, with most fluorine located on the surface. This localized distribution provides enhanced protection where it is most needed (at the interface with electrolyte) while maintaining the bulk electrochemical performance of the cathode material

Inventive Principle:

Principle #3Local quality

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 cathode active material enables increased battery capacity and improved cycle life by maintaining structural stability and preventing side reactions at high voltages, thus enhancing battery performance and safety.

Implementation Method 1

most of the fluorine is present on the surface of the lithium transition metal oxide

Methodology Applied

Scientific EffectSurface passivation by fluorine: Adsorption

Implementation Method 2

lithium secondary batteries having high energy density and output voltage, long cycle life and low self-discharge ratio

Methodology Applied

Scientific EffectElectrochemical reaction: Redox Reactions

Data Source

PatentEP2352190B1Positive active material with improved characteristics at high battery voltage

Publication Date: 2015.08.26 LG CHEM LTD

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AI summary

Disclosed herein is a cathode active material including a lithium transition metal oxide based on at least one transition metal selected from a group consisting of Ni, Mn and Co. The lithium transition metal oxide contains fluorine, and most of the fluorine is present on a surface of the lithium transition metal oxide, and at least one metal selected from a group consisting of Mg, Ti, Zr, Al and Fe as well as sulfur (S) are further contained in the lithium transition metal oxide.