LiF-Metal Fluoride Cathode Coatings for High-Voltage Cycle Life

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Solution Overview

Problem

Existing lithium-ion battery cathode active materials face challenges such as short cycle life due to chemical reactions with the electrolyte and energy density loss, particularly with non-conductive aluminum oxide and process safety concerns with aluminum fluoride coatings.

Innovation Solution

A coating comprising a mixture of lithium fluoride (LiF) and metal fluorides like AlF3, CaF2, MgF2, and LaF2, combined with metal oxides such as TiO2, MgO, La2O3, CaO, and Al2O3, is applied to cathode active materials. This coating is formed by reacting metal fluorides with lithium cobalt oxide-based bulk materials at elevated temperatures, creating a stable surface composition that enhances protection against the electrolyte.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If aluminum oxide coating is applied to cathode particles, then protection against electrolyte reaction is improved, but energy density is reduced due to non-conductive properties

Engineering Contradiction:

Improveprotection against electrolyte reactionVSAvoidenergy density

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The patent applies composite coating materials comprising aluminum fluoride and titanium oxide together on cathode particles. The aluminum fluoride provides protective functions against electrolyte reaction, while the titanium oxide component maintains or improves electrical conductivity. This composite approach allows simultaneous achievement of protection (improving reliability) and conductivity preservation (maintaining energy density), resolving the contradiction between using protective coatings and maintaining battery energy density.

Inventive Principle:

Principle #40Composite materials

2Reliability

If aluminum fluoride coating is applied to cathode particles, then protection against electrolyte reaction is improved, but process safety concerns arise

Engineering Contradiction:

Improveprotection against electrolyte reactionVSAvoidprocess safety

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent modifies the chemical composition parameters of the coating by combining aluminum fluoride with titanium oxide in specific ratios. This parameter change transforms the coating properties to achieve both protection against electrolyte reaction and improved process safety. The titanium oxide component stabilizes the coating structure and reduces harmful effects during manufacturing processes, allowing the aluminum fluoride to provide protection without compromising safety.

Inventive Principle:

Principle #35Parameter changes

3Use of energy by moving object

If cathode materials operate at high upper cut-off voltages, then energy density is improved, but surface stability deteriorates leading to shorter cycle life

Engineering Contradiction:

Improveenergy densityVSAvoidsurface stability

Core Design Contradiction:

Use of energy by moving objectVSStability of the object's composition

Solution Approach 1:

The patent uses composite coating of aluminum fluoride and titanium oxide to address the contradiction between high voltage operation and surface stability. The aluminum fluoride layer provides chemical stability and protects against electrolyte decomposition at high voltages, while the titanium oxide layer maintains electrical conductivity and structural integrity. This composite structure enables the cathode to operate at high upper cut-off voltages for improved energy density while maintaining surface stability for extended cycle life.

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 proposed coating significantly improves the electrochemical performance of lithium-ion batteries by enhancing surface protection, increasing battery capacity, and maintaining discharge energy over cycles, even at high upper cut-off voltages and temperatures.

Implementation Method 1

This coating is formed by reacting metal fluorides with lithium cobalt oxide-based bulk materials at elevated temperatures, creating a stable surface composition

Methodology Applied

Scientific EffectChemical reaction: Chemical Bonding

Implementation Method 2

This coating is formed by reacting metal fluorides with lithium cobalt oxide-based bulk materials at elevated temperatures

Methodology Applied

Scientific EffectThermal heating: Heating

Data Source

PatentUS12218352B2Lithium fluoride-containing coatings for cathode active materials in Li-ion batteries

Publication Date: 2025.02.04 APPLE INC

AI summary

The disclosure provides a plurality of particles. Each particle may include a material comprising 0.95 to 1.30 mole fraction Li, at least 0.60 and less than 1.00 mole fraction Co, up to 10,000 ppm Al, 1.90 to 2.10 mole fraction O, and up to 0.30 mole fraction M, where M is at least one element selected from B, Na, Mg, P, Ti, Ca, V, Cr, Fe, Mn, Ni, Cu, Zn, Al, Sc, Y, Ga, Zr, Ru, Mo, La, Si, Nb, Ge, In, Sn, Sb, Te, and Ce. Each particle may also include a surface composition comprising a mixture of LiF and a metal fluoride. An amount of fluorine (F) is greater than 0 and less than or equal to 5000 ppm. The metal fluoride comprises a material selected from the group consisting of AlF3, CaF2, MgF2, and LaF2. The surface composition may also include a metal oxide comprising a material selected from the group consisting of TiO2, MgO, La2O3, CaO, and Al2O3. An amount of the metal oxide is greater than 0 and less than or equal to 20000 ppm.