Multicomponent Cathode Coatings Mitigate HF Degradation

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Solution Overview

Problem

Cathode degradation in lithium-ion batteries due to hydrofluoric acid (HF) induced reactions limits their lifetime, with existing coatings like binary oxides not effectively addressing transition metal ion dissolution and capacity fade.

Innovation Solution

Development of cathode coatings using borates, phosphates, silicates, and metal oxides such as TaBO4, NbBO4, Ca5(BO3)3F, Mn2PO4F, Li2MgSiO4, and WO3, which act as physical barriers, HF-scavengers, or HF-barriers to mitigate HF-induced degradation, utilizing a high-throughput density functional theory-based design framework.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If binary oxide coatings (Al2O3, MgO, ZnO, ZrO2, SiO2, TiO2) are applied to cathode particles, then HF-content in the electrolyte is reduced, but transition metal ion dissolution and capacity fade are not effectively suppressed

Engineering Contradiction:

ImproveHF-content in electrolyteVSAvoidtransition metal ion dissolution and capacity fade

Core Design Contradiction:

Object-affected harmful factorsVSReliability

Solution Approach 1:

The patent changes the chemical composition parameters of the coating materials from simple binary oxides to complex multicomponent compounds with specific stoichiometries (e.g., Li2MgSiO4, CaMgSi2O6, Li3NbO4, TaBO4). These compositional changes enable the coatings to simultaneously address HF reduction and transition metal ion dissolution suppression by providing both physical barrier properties and chemical reactivity control.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent employs composite coating materials that combine multiple elements (Li, Mg, Si, Ca, Nb, Ta, B, O, F) in specific ratios. These composite materials integrate the benefits of different elements: Li provides electrochemical stability, Mg and Ca enhance structural stability, Si and B provide HF-scavenging capability, while Nb and Ta offer high electrochemical stability. The composite structure enables simultaneous protection against multiple degradation mechanisms.

Inventive Principle:

Principle #40Composite materials

2Reliability

If complex coating materials are designed to suppress transition metal dissolution, then cathode protection is improved, but the complexity of reactions between cathode, coating and electrolyte prohibits generic design guidelines

Engineering Contradiction:

Improvecathode protectionVSAvoidcomplexity of reactions

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent identifies a universal set of coating materials (borates, phosphates, silicates, and specific metal oxides) that can serve multiple protective functions simultaneously: physical barrier against electrolyte contact, chemical scavenging of HF, and suppression of transition metal ion dissolution. These universal materials can be applied to different cathode types (layered, spinel, olivine) providing a generic design framework that simplifies the selection process despite the complexity of underlying reactions.

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Object-affected harmful factors

If trace water is present in LiPF6 based electrolytes, then hydrofluoric acid forms and attacks cathode particles, but alternative electrolyte compositions may introduce other degradation pathways

Engineering Contradiction:

Improvecathode particle attackVSAvoidelectrolyte composition flexibility

Core Design Contradiction:

Object-affected harmful factorsVSAdaptability or versatility

Solution Approach 1:

The patent introduces coating materials as intermediary substances between the cathode and electrolyte. These coatings act as mediators that selectively interact with HF to form stable compounds (e.g., LiF, MgF2, CaF2, TaF5, NbF5) while maintaining electrochemical stability. The intermediary coatings protect the cathode from direct HF attack without requiring fundamental changes to the electrolyte composition, thus preserving electrolyte flexibility while effectively mitigating cathode degradation.

Inventive Principle:

Principle #24Intermediary (Mediator)

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

These coatings significantly improve the performance of lithium-ion batteries by reducing HF-induced degradation, extending the battery's lifespan and maintaining electrochemical stability.

Implementation Method 1

a coating on at least a portion of the active cathode material, wherein the coating includes a borate selected from TaBO4, NbBO4, Ca5(BO3)3F, Mg3(BO3)2, CaAlBO4, and LiBO2

Methodology Applied

Scientific EffectPhysical barrier: Physical Containment

Implementation Method 2

act as physical barriers, HF-scavengers, or HF-barriers to mitigate HF-induced degradation

Methodology Applied

Scientific EffectHF-scavenging: Absorption (physical)

Implementation Method 3

act as physical barriers, HF-scavengers, or HF-barriers to mitigate HF-induced degradation

Methodology Applied

Scientific EffectHF-barrier: Diffusion Barrier

Data Source

PatentUS10374262B2Protective cathode coatings for lithium-ion batteries

Publication Date: 2019.08.06 NORTHWESTERN UNIV

AI summary

Cathode coatings for lithium ion batteries, cathodes coated with the coatings, and lithium ion batteries incorporating the coated cathodes are provided. The coatings, which are composed of binary, ternary, and higher order metal oxides and/or metalloid oxides, can reduce the hydrofluoric acid (HF)-induced degradation of the electrolyte and/or cathodes, thereby improving the performance of lithium ion batteries, relative to lithium ion batteries that employ bare cathodes.