Nickel-Based Cathode Material with Boron Coating and Radial Structure

Solution Overview

Problem

Rechargeable lithium batteries face issues with long-term cycle-life deterioration, increased resistance, and unsatisfactory capacity characteristics due to structure collapses and cracks in existing nickel-based positive active materials.

Innovation Solution

A positive active material for lithium batteries is developed, comprising a mixture of two nickel-based materials with different particle sizes, where the first material has radially arranged primary particles with larger secondary particles and the second material is coated with a boron compound, enhancing cycle-life and energy density.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If conventional nickel-based positive active materials are used to achieve high capacity, then energy density is improved, but structure collapses and cracks occur after repeated charges and discharges leading to poor cycle-life

Engineering Contradiction:

Improveenergy densityVSAvoidcycle-life

Core Design Contradiction:

Use of energy by moving objectVSReliability

Solution Approach 1:

The positive active material is divided into two distinct types (first and second nickel-based positive active materials) with different particle size characteristics. This segmentation allows each type to fulfill different functional roles: the first type provides high capacity while the second type with smaller particles and boron coating provides structural stability, thereby resolving the contradiction between energy density and cycle-life.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The invention creates a composite positive active material by mixing first and second nickel-based positive active materials in specific proportions (70:30 to 90:10 by weight). This composite structure combines the high capacity characteristics of the first material with the enhanced stability of the second material that has smaller secondary particles and boron compound coating, simultaneously achieving high energy density and improved cycle-life.

Inventive Principle:

Principle #40Composite materials

2Use of energy by moving object

If nickel-based positive active materials are used to increase capacity, then energy density is improved, but resistance increases after repeated charges and discharges

Engineering Contradiction:

ImprovecapacityVSAvoidresistance

Core Design Contradiction:

Use of energy by moving objectVSReliability

Solution Approach 1:

The second nickel-based positive active material is specifically coated with boron compounds on its surface. This local quality enhancement at the surface level provides resistance to structural degradation and reduces resistance increase during cycling, while the bulk material maintains its high capacity characteristics. The boron coating acts as a protective layer that prevents harmful interactions at the electrode-electrolyte interface.

Inventive Principle:

Principle #3Local quality

3Volume of stationary object

If larger secondary particles are used to increase energy density, then volume efficiency is improved, but structure collapses occur after repeated charges and discharges

Engineering Contradiction:

Improveenergy densityVSAvoidstructural stability

Core Design Contradiction:

Volume of stationary objectVSStability of the object's composition

Solution Approach 1:

The positive active material is divided into two distinct types (first and second nickel-based positive active materials) with different particle size characteristics. This segmentation allows each type to fulfill different functional roles: the first type provides high capacity while the second type with smaller particles and boron coating provides structural stability, thereby resolving the contradiction between energy density and cycle-life.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The invention creates a composite positive active material by mixing first and second nickel-based positive active materials in specific proportions (70:30 to 90:10 by weight). This composite structure combines the high capacity characteristics of the first material with the enhanced stability of the second material that has smaller secondary particles and boron compound coating, simultaneously achieving high energy density and improved cycle-life.

Inventive Principle:

Principle #40Composite materials

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 solution provides improved cycle-life characteristics and high energy density while maintaining initial discharge capacity, by minimizing cracks and surface resistance through the radially arranged structure and boron coating, which stabilizes the material and reduces volume changes during charging and discharging.

Implementation Method 1

the second positive active material is coated with a boron compound... which stabilizes the material and reduces volume changes during charging and discharging

Methodology Applied

Scientific EffectVolume change stabilization:

Implementation Method 2

at least one part of the primary particles has a radially arranged structure... minimizing cracks and surface resistance through the radially arranged structure

Methodology Applied

Scientific EffectRadial arrangement structure:

Data Source

PatentUS20220293913A1Positive active material for rechargeable lithium battery, preparing method thereof and rechargeable lithium battery including the same

Publication Date: 2022.09.15 SAMSUNG SDI CO LTD

AI summary

A positive active material for a rechargeable lithium battery includes a first positive active material including a secondary particle formed by aggregation of a plurality of primary particles, wherein at least a portion of the primary particles have a radially arranged structure, and a second positive active material including a secondary particle formed by aggregation of a plurality of primary particles, wherein the first positive active material and the second positive active material are both (e.g., simultaneously) nickel-based positive active materials, a particle diameter of the secondary particle of the first positive active material is larger than a particle diameter of the secondary particles\ of the second positive active material, and the second positive active material is coated with a boron compound.