Lithium Phosphate Infused NMC Cathode Materials

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Solution Overview

Problem

Nickel-rich NMC cathode materials face challenges such as Li/Ni cation mixing, structural degradation due to lattice transformation and strain, and safety concerns from thermal reactions with organic carbonate electrolytes, leading to cracking and reduced electrochemical performance.

Innovation Solution

Lithium phosphate is infused into nickel-rich LiNixMnyCozO2 (NMC) cathode materials to suppress cracking by buffering internal strain and preventing electrolyte penetration, enhancing structural integrity and cycle stability through a unique protection mechanism.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If nickel-rich NMC cathode materials are used to achieve high discharge capacity and energy density, then the discharge capacity and energy density are improved, but structural degradation and cracking occur due to lattice transformation and strain

Engineering Contradiction:

Improvedischarge capacityVSAvoidstructural stability

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

Lithium phosphate is infused into the NMC cathode material before battery operation to pre-establish a protective mechanism that buffers internal strain and prevents cracking during subsequent cycling, thereby maintaining structural stability while enabling high discharge capacity

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

Lithium phosphate acts as an intermediary substance that mediates between the NMC cathode material and the harmful effects of lattice transformation and strain, providing a protective effect that prevents cracking and structural degradation while allowing the high-capacity NMC material to function

Inventive Principle:

Principle #24Intermediary (Mediator)

2Productivity

If nickel-rich NMC cathode materials are used to achieve high energy density, then the energy density is improved, but thermal reactions with organic carbonate electrolytes occur leading to safety concerns

Engineering Contradiction:

Improveenergy densityVSAvoidthermal stability

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

Lithium phosphate serves as an intermediary protective layer between the nickel-rich NMC cathode material and the organic carbonate electrolyte, preventing direct thermal reactions while allowing the high-energy-density material to operate safely

Inventive Principle:

Principle #24Intermediary (Mediator)

3Reliability

If conventional lithium phosphate coating is applied to protect NMC cathode materials, then some protection is provided, but the coating does not effectively prevent electrolyte penetration and cracking

Engineering Contradiction:

Improveprotection effectivenessVSAvoidcoating structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The invention replaces the conventional physical coating approach with a chemical infusion approach, where lithium phosphate is infused into the NMC cathode material to create a distributed protective mechanism throughout the material structure, effectively preventing electrolyte penetration and cracking

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 lithium phosphate-infused NMC cathode materials exhibit superior cycle stability, retaining at least 90% capacity after 150 cycles with reduced particle cracking and improved thermal stability, while maintaining high discharge capacity.

Implementation Method 1

The disclosed lithium phosphate infused secondary particles significantly buffer the strain that is generated during deep delithiation

Methodology Applied

Scientific EffectStrain buffering:

Implementation Method 2

reduce or prevent electrolyte penetration by blocking the intergranular percolation pathways in the particles

Methodology Applied

Scientific EffectPercolation blocking:

Implementation Method 3

the secondary particles have lithium phosphate diffused within the secondary particles

Methodology Applied

Scientific EffectDiffusion: Diffusion

Data Source

PatentUS10734641B2High capacity and stable cathode materials

Publication Date: 2020.08.04 BATTELLE MEMORIAL INST

AI summary

High energy density cathode materials, such as LiNixMnyCozO2 (NMC) cathode materials, with improved discharge capacity (hence energy density) and enhanced cycle life are described. A solid electrolyte, such as lithium phosphate infused inside of secondary particles of the cathode material demonstrates significantly enhanced structural integrity without significant or without any observable particle cracking occurring during charge/discharge processes, showing high capacity retention of more than 90% after 200 cycles at room temperature. In certain embodiments the disclosed cathode materials (and cathodes made therefrom) are formed using nickel-rich NMC and/or are used in a battery system with a non-aqueous dual-Li salt electrolytes.