Gradient Lithium Phosphate Particles for Battery Conductivity

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Solution Overview

Problem

Lithium iron phosphate-based batteries face issues with high electric resistance, secondary aggregation, and stability due to the high surface area of finely pulverized particles, leading to inadequate discharge capacity and long-term stability, as well as difficulties in achieving sufficient current collection and particle control.

Innovation Solution

The development of multi-component system lithium phosphate compound particles with an olivine structure, represented by LiYM11-ZM2ZPO4, where the concentration of metal element M2 is higher on the surface than in the core, and gradually decreases towards the core, enhancing electric conductivity and lithium ion movement, combined with carbon-based composite particles for improved charge/discharge properties.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Area of moving object

If lithium phosphate compound particles are finely pulverized to increase reactive surface area, then lithium ion diffusion is facilitated, but secondary aggregation occurs during electrode manufacturing

Engineering Contradiction:

Improvereactive surface areaVSAvoidparticle dispersion stability

Core Design Contradiction:

Area of moving objectVSStability of the object's composition

Solution Approach 1:

The patent applies local quality by creating a core-shell structure where the particle core maintains the lithium phosphate compound with high reactive surface area, while the surface is coated with a specific material composition that prevents aggregation. This local differentiation allows the interior to provide high reactivity while the exterior provides stability during handling and electrode manufacturing.

Inventive Principle:

Principle #3Local quality

2Reliability

If high concentration of metal element M2 is distributed throughout the particle, then electric conductivity is improved, but manufacturing precision of concentration gradient becomes difficult

Engineering Contradiction:

Improveelectric conductivityVSAvoidconcentration distribution control

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The patent employs preliminary action by first forming particles with a specific core composition, then sequentially adding metal element M2 through surface treatment or coating processes. This stepwise approach allows precise control over the concentration gradient, ensuring high M2 concentration at the surface for conductivity while maintaining manufacturing feasibility through controlled deposition rather than attempting to create the gradient in a single mixing step.

Inventive Principle:

Principle #10Preliminary action

3Reliability

If carbon is added to improve electric conductivity and current collection, then charge/discharge capacity is enhanced, but particle aggregation increases

Engineering Contradiction:

Improvecharge/discharge capacityVSAvoidparticle aggregation

Core Design Contradiction:

ReliabilityVSStability of the object's composition

Solution Approach 1:

The patent merges the functions of conductivity enhancement and aggregation prevention by integrating carbon material into the surface coating layer rather than adding it separately. The carbon is incorporated into the shell structure that already provides steric stabilization, creating a unified coating that simultaneously improves electrical conductivity and maintains particle dispersion, allowing current collection enhancement without triggering aggregation.

Inventive Principle:

Principle #5Merging (Combining)

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

This approach results in enhanced high-rate charge/discharge properties, improved electric conductivity, and increased stability of lithium secondary batteries by optimizing the distribution of metal elements and carbon within the particles, addressing the limitations of existing technologies.

Implementation Method 1

facilitate the diffusion of lithium ions, thereby shortening the distance through which electrons are enabled to flow

Methodology Applied

Scientific EffectIon diffusion: Diffusion

Implementation Method 2

employing a multi-component system lithium phosphate compound... enhancing electric conductivity and lithium ion movement

Methodology Applied

Scientific EffectElectrical conduction: Conduction (electrical)

Data Source

PatentUS9337488B2Method of manufacturing a multicomponent system lithium phosphate compound particle having an olivine structure

Publication Date: 2016.05.10 SUMITOMO METAL MINING CO LTD

AI summary

A method of manufacturing a multicomponent lithium phosphate compound particle with an olivine structure of formula LiyM11-ZM2ZPO4, M1 is Fe, Mn or Co; Y satisfies 0.9≦Y≦1.2; M2 is Mn, Co, Mg, Ti or Al; and Z satisfies 0<Z≦0.1, in which the M2 concentration is continuously lowered from a surface of the particle to a core portion of the particle. The method includes mixing a lithium M1 phosphate compound with an olivine structure of formula LiXM1PO4, M1 is Fe, Mn or Co, and X satisfies 0.9≦X≦1.2, and a precursor of a lithium M2 phosphate compound with an olivine structure of formula LiXM2PO4, M2 is Mn, Co, Mg, Ti or Al, and X satisfies 0.9≦X≦1.2, to form a mixture; and subjecting the mixture to heating in an inert atmosphere or a vacuum.