Oriented Olivine Positive Electrode for Lithium-Ion Battery

Solution Overview

Problem

Lithium-containing composite oxide particles with an olivine structure in lithium secondary batteries face difficulties in orienting their crystal axes vertically to the positive electrode current collector, hindering lithium ion occlusion and release, which limits battery capacity and output.

Innovation Solution

Incorporating graphene oxide or multilayer graphene oxide with lithium-containing composite oxide particles, specifically using rectangular parallelepiped particles and applying pressure to orient the b-axes vertically, while also serving as a conductive agent and binder, reducing the need for additional conductive agents and binders.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If lithium-containing composite oxide particles with olivine structure are used as positive electrode active material, then safety is improved, but lithium ion occlusion and release is hindered due to lack of oriented b-axis alignment

Engineering Contradiction:

ImprovesafetyVSAvoidlithium ion occlusion and release

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The invention changes the shape parameter of lithium-containing composite oxide particles from spherical to rectangular parallelepiped, where the b-axis length is shorter than a-axis and c-axis lengths. This geometric parameter change enables the particles to naturally orient with b-axes perpendicular to the current collector surface during electrode manufacturing, thereby opening the one-dimensional lithium-ion path along the b-axis and improving lithium ion occlusion and release while maintaining the safety benefits of the olivine structure

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The invention introduces asymmetric particle geometry by making the b-axis length shorter than the a-axis and c-axis lengths in the rectangular parallelepiped structure. This asymmetry creates a preferred orientation direction during compression, causing the shortest axis (b-axis) to align perpendicular to the current collector surface, thus enabling effective lithium ion transport paths while maintaining structural safety

Inventive Principle:

Principle #4Asymmetry

2Reliability

If conventional spherical lithium-containing composite oxide particles are used with carbon particles and PVdF binder, then electron path and attachment are ensured, but crystal axis orientation cannot be controlled

Engineering Contradiction:

Improveelectron path and attachmentVSAvoidcrystal axis orientation

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The invention changes the shape parameter of lithium-containing composite oxide particles from spherical to rectangular parallelepiped with specific axis length relationships (b-axis shorter than a-axis and c-axis). This geometric parameter change enables the particles to naturally orient with b-axes perpendicular to the current collector surface during electrode manufacturing, thereby opening the one-dimensional lithium-ion path along the b-axis and improving lithium ion occlusion and release while maintaining the safety benefits of the olivine structure

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The invention introduces asymmetric particle geometry by making the b-axis length shorter than the a-axis and c-axis lengths in the rectangular parallelepiped structure. This asymmetry creates a preferred orientation direction during compression, causing the shortest axis (b-axis) to align perpendicular to the current collector surface, thus enabling effective lithium ion transport paths while maintaining structural safety

Inventive Principle:

Principle #4Asymmetry

3Force

If pressure is applied to positive electrode active material layer during manufacturing, then particle alignment may occur, but spherical particles do not change crystal axis direction

Engineering Contradiction:

Improvepressure applicationVSAvoidcrystal axis orientation

Core Design Contradiction:

ForceVSManufacturing precision

Solution Approach 1:

The invention changes the shape parameter of lithium-containing composite oxide particles from spherical to rectangular parallelepiped with specific axis length relationships (b-axis shorter than a-axis and c-axis lengths). This geometric parameter change enables the particles to naturally orient with b-axes perpendicular to the current collector surface during compression, thereby opening the one-dimensional lithium-ion path along the b-axis and improving lithium ion occlusion and release while maintaining the safety benefits of the olivine structure

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The invention introduces asymmetric particle geometry by making the b-axis length shorter than the a-axis and c-axis lengths in the rectangular parallelepiped structure. This asymmetry creates a preferred orientation direction during compression, causing the shortest axis (b-axis) to align perpendicular to the current collector surface, thus enabling effective lithium ion transport paths while maintaining structural safety

Inventive Principle:

Principle #4Asymmetry

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 enhances lithium ion occlusion and release, increasing battery capacity and output by effectively orienting the b-axes of lithium-containing composite oxide single crystals, as demonstrated by improved X-ray diffraction peak intensity ratios and charge/discharge characteristics.

Implementation Method 1

graphene oxide or multilayer graphene oxide which serves as a conductive agent and a binder

Methodology Applied

Scientific EffectElectrical conduction: Conduction (electrical)

Implementation Method 2

graphene oxide or multilayer graphene oxide which serves as a conductive agent and a binder

Methodology Applied

Scientific EffectAdhesion: Adhesive

Implementation Method 3

applying pressure to orient the b-axes vertically

Methodology Applied

Scientific EffectMechanical compression: Compression

Implementation Method 4

improved X-ray diffraction peak intensity ratios

Methodology Applied

Scientific EffectX-ray diffraction: X-Ray

Implementation Method 5

improved X-ray diffraction peak intensity ratios

Methodology Applied

Scientific EffectDiffraction: Diffraction

Implementation Method 6

there is a one-dimensional lithium-ion path along the b-axis direction of the crystal lattice of lithium iron phosphate

Methodology Applied

Scientific EffectIon diffusion: Diffusion

Implementation Method 7

occlusion and release are less likely to occur therein

Methodology Applied

Scientific EffectOcclusion and release: Absorption (physical)

Data Source

PatentUS9935313B2Positive electrode for lithium secondary battery, manufacturing method thereof, and lithium secondary battery

Publication Date: 2018.04.03 SEMICON ENERGY LAB CO LTD

AI summary

Occlusion and release of lithium ion are likely to one-dimensionally occur in the b-axis direction of a crystal in a lithium-containing composite oxide having an olivine structure. Thus, a positive electrode in which the b-axes of lithium-containing composite oxide single crystals are oriented vertically to a surface of a positive electrode current collector is provided. The lithium-containing composite oxide particles are mixed with graphene oxide and then pressure is applied thereto, whereby the rectangular parallelepiped or substantially rectangular parallelepiped particles are likely to slip. In addition, in the case where the rectangular parallelepiped or substantially rectangular parallelepiped particles whose length in the b-axis direction is shorter than those in the a-axis direction and the c-axis direction are used, when pressure is applied in one direction, the b-axes can be oriented in the one direction.