Monocrystalline Cathode Particles With Lithium-Gradient Shell Structure

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Solution Overview

Problem

Current polycrystalline cathode materials in lithium secondary batteries suffer from rapid capacity decay due to anisotropic volume changes, grain-boundary fractures, and surface impurities, leading to increased impedance and performance degradation, while monocrystalline materials face challenges in electrochemical performance and packing density.

Innovation Solution

A continuous hydrothermal process is used to produce monocrystalline particles with a lithium-deficient shell and excess lithium core, eliminating internal voids and grain boundaries, and a subsequent water contact removes residual lithium, enabling high-density packing and improved cyclability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If polycrystalline cathode materials are used, then manufacturing process is simpler, but structural integrity deteriorates during cycling due to grain-boundary fractures

Engineering Contradiction:

Improvemanufacturing process simplicityVSAvoidstructural integrity during cycling

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The patent changes the crystallographic parameters by controlling hydrothermal synthesis conditions (temperature, pressure, time, pH) to grow monocrystalline particles with specific orientations and morphologies, eliminating grain boundaries while maintaining manufacturability through a continuous hydrothermal process

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent creates a composite structure with a monocrystalline active material core and a protective surface layer formed by controlled lithium deficiency, combining the structural integrity of monocrystals with surface protection against degradation

Inventive Principle:

Principle #40Composite materials

2Reliability

If monocrystalline particles are produced by conventional heat treatment, then grain boundaries are eliminated, but production time and energy consumption increase

Engineering Contradiction:

Improvegrain boundary eliminationVSAvoidproduction time

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The patent replaces the thermal field (conventional heat treatment) with a hydrothermal field (aqueous environment at elevated temperature and pressure), enabling monocrystalline growth through solution-mediated transport and precipitation rather than solid-state diffusion, significantly reducing processing time

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent utilizes phase transitions of water (liquid to supercritical fluid and back) to control the hydrothermal synthesis process, enabling rapid heating and cooling cycles that promote monocrystalline growth without extended high-temperature treatment

Inventive Principle:

Principle #36Phase transitions

3Stability of the object's composition

If lithium concentration is uniform throughout the particle, then material composition is simpler, but surface impurities increase due to residual lithium reaction

Engineering Contradiction:

Improvelithium concentration uniformityVSAvoidsurface impurities

Core Design Contradiction:

Stability of the object's compositionVSObject-generated harmful factors

Solution Approach 1:

The patent creates a non-uniform lithium concentration distribution with a lithium-deficient surface layer and lithium-rich core, where the surface layer specifically addresses impurity formation while the core maintains overall stoichiometry, giving different regions different compositional qualities

Inventive Principle:

Principle #3Local quality

4Ease of manufacture

If internal voids are present in polycrystalline particles, then particle formation is easier, but packing density decreases

Engineering Contradiction:

Improveparticle formation easeVSAvoidpacking density

Core Design Contradiction:

Ease of manufactureVSVolume of stationary object

Solution Approach 1:

The patent changes the formation mechanism from agglomeration of primary particles (which creates voids) to direct hydrothermal growth of dense monocrystalline particles, altering the physical parameters of particle formation to eliminate internal void space and achieve higher packing density

Inventive Principle:

Principle #35Parameter changes

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 method produces monocrystalline particles that maintain structural integrity during cycling, reducing impedance and enhancing volumetric capacity and charge capability, with improved packing density and reduced lithium impurities.

Implementation Method 1

A continuous hydrothermal process is used to produce monocrystalline particles with a lithium-deficient shell and excess lithium core

Methodology Applied

Scientific EffectHydrothermal synthesis: Supercritical Fluid

Data Source

PatentUS12448703B2Continuous hydrothermal manufacturing method for concentration-gradient monocrystalline battery material

Publication Date: 2025.10.21 UCHICAGO ARGONNE LLC

AI summary

The invention provides a battery material comprising-monocrystalline particles not having internal void fractions, wherein each of the monocrystalline particles is without internal grain boundaries such that anisotropic volume change issues of polycrystalline particles don't occur when the particles are charged and discharged during cycling. Also provided is the monocrystalline particles with less-lithium on the particle surface. Also provided is a method for preparing monocrystalline battery material, wherein the battery material may be incorporated into a secondary battery.