Li-rich rocksalt cathodes with inhibited cation migration

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Solution Overview

Problem

Lithium-rich cathode materials for rechargeable lithium-ion batteries face limitations due to voltage hysteresis and continuous voltage fade, which are associated with transition metal migration, hindering their energy efficiency and practical implementation in electric vehicles and consumer electronics.

Innovation Solution

Introducing partial cation disorder in lithium-rich cathode materials through mechanical milling, specifically in compositions like Li1.2Cr0.4Mn0.4O2, to inhibit collective transition metal migration, thereby reducing voltage hysteresis and increasing capacity and energy density.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If lithium-rich cathode materials are used to achieve high energy density, then capacity increases, but voltage hysteresis and voltage fade occur due to transition metal migration

Engineering Contradiction:

ImprovecapacityVSAvoidvoltage stability

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

The patent applies parameter changes by modifying the local chemical environment and oxidation states of transition metals through controlled oxygen redox reactions. This changes the electronic structure and bonding characteristics, thereby suppressing transition metal migration while maintaining high capacity. The material composition and electronic state are adjusted to resolve the contradiction between high capacity and voltage stability.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent employs composite material strategies by creating a complex cathode structure with multiple transition metal elements (Cr, Mn, Ni, Co) in specific ratios and configurations. This multi-element composite approach allows synergistic effects where different metals contribute to capacity while collectively suppressing migration through altered electronic interactions and structural stability.

Inventive Principle:

Principle #40Composite materials

2Use of energy by moving object

If transition metal content is increased to improve redox capacity, then energy density increases, but transition metal migration into Li layers increases causing hysteresis

Engineering Contradiction:

Improveenergy densityVSAvoidtransition metal migration

Core Design Contradiction:

Use of energy by moving objectVSObject-generated harmful factors

Solution Approach 1:

The patent converts the potentially harmful transition metal migration into a beneficial effect by utilizing controlled oxygen redox reactions that stabilize the transition metals in their proper layers. The oxygen evolution and incorporation processes create strong bonding that anchors transition metals, transforming what would be migration-driven hysteresis into a mechanism for enhanced capacity through reversible oxygen redox.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The patent applies local quality by creating distinct regions with different transition metal compositions and oxidation states. Specific transition metal sites are engineered with different local environments (coordination geometry, neighboring atoms, oxygen content) that tailor the redox activity and migration resistance of individual metal centers, allowing high energy density while suppressing overall migration.

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 cation-disordered materials exhibit significantly reduced voltage hysteresis, achieving high reversible capacity and energy density, with lithium transport occurring through a percolation network of Li-rich tetrahedral environments, enhancing the electrochemical performance and cycling stability of lithium-ion batteries.

Implementation Method 1

Introducing partial cation disorder in lithium-rich cathode materials through mechanical milling

Methodology Applied

Scientific EffectMechanical milling:

Implementation Method 2

lithium transport occurring through a percolation network of Li-rich tetrahedral environments

Methodology Applied

Scientific EffectIon diffusion: Diffusion

Implementation Method 3

electrochemical performance and cycling stability of lithium-ion batteries

Methodology Applied

Scientific EffectElectrochemical reaction:

Data Source

PatentUS20240258515A1High-energy li-rich rocksalt cathodes with inhibited cation migration

Publication Date: 2024.08.01 RGT UNIV OF CALIFORNIA

AI summary

A lithium rich partially cation disordered transition metal oxide cathode material is provided that exhibits reduced voltage hysteresis, reduced or inhibited transition metal migration and increased capacity and energy storage compared with layered oxides. The lithium rich cathode material is based on Li1+xCr1−x-yMyO2 where M is a transition metal with limited redox activity, such as Mn4+, Ti4+, Zr4+, Sn4+, Nb5+, Ta5+, and W6+, and where 0<x<0.33 and 0<y<0.67. Cation disordering is induced in the material that alters both the structure and the electrochemistry and effectively mitigate voltage hysteresis and increase the reversibility of the Cr3+/Cr6+ redox couple and the energy capacity. Lithium transport in the cation-disordered structure occurs through a percolation network of Li-rich tetrahedral environments.