Bimodal Cathode Material for Li-Ion Battery Energy Density

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Solution Overview

Problem

Lithium cobalt oxide (LiCoO2) cathode materials in lithium ion batteries face challenges in achieving high energy density and voltage stability simultaneously, with issues such as phase transition, cobalt elution, and surface reactivity leading to reduced battery lifetime.

Innovation Solution

A bimodal-type cathode active material is developed, comprising layered LiCoO2 large particles and manganese-based olivine structural LiCoxMnyFezPO4 small particles, with specific particle size and composition ranges, and surface treatments like aluminum oxide coating, to enhance stability and conductivity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If LiCoO2 large particles are used to achieve high energy density, then energy per volume increases, but voltage stability deteriorates due to phase transition at high voltage

Engineering Contradiction:

Improveenergy densityVSAvoidvoltage stability

Core Design Contradiction:

Use of energy by moving objectVSReliability

Solution Approach 1:

The cathode material is segmented into two distinct particle size groups: large particles (10-50 μm) for high energy density and small particles (1-5 μm) for voltage stability. This segmentation allows each particle size to fulfill its specific functional role without compromising the other.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The invention creates a composite cathode material by mixing LiCoO2 large particles with LiCoO2 small particles in a bimodal distribution. This composite structure combines the high energy density advantage of large particles with the voltage stability advantage of small particles, achieving both goals simultaneously.

Inventive Principle:

Principle #40Composite materials

2Quantity of substance

If LiCoO2 small particles are used to increase capacity, then surface reactivity increases, but stability deteriorates

Engineering Contradiction:

Improvebattery capacityVSAvoidstability

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

Different particle sizes are assigned different functional qualities: small particles provide high capacity contribution through their large surface area, while large particles provide structural stability. The system exploits local quality differences to achieve overall performance optimization.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The invention changes the particle size parameter distribution from monomodal to bimodal, creating a specific size distribution where small particles (1-5 μm) contribute to capacity while large particles (10-50 μm) maintain stability. This parameter optimization resolves the contradiction between capacity and stability.

Inventive Principle:

Principle #35Parameter changes

3Quantity of substance

If upper limit voltage is raised to increase capacity, then energy per volume increases, but lifetime characteristic deteriorates due to phase transition

Engineering Contradiction:

Improvebattery capacityVSAvoidbattery lifetime

Core Design Contradiction:

Quantity of substanceVSDuration of action of moving object

Solution Approach 1:

The bimodal particle structure acts as a cushioning mechanism against high voltage stress. Small particles absorb the mechanical and chemical stress of high voltage charging/discharging cycles, protecting the larger particles from phase transition and structural degradation, thereby extending battery lifetime.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

Solution Approach 2:

Small LiCoO2 particles serve as an intermediary that mediates the high voltage stress between the electrode and electrolyte. They experience the high voltage conditions first and protect the bulk material (large particles) from direct exposure to damaging conditions, preserving battery lifetime.

Inventive Principle:

Principle #24Intermediary (Mediator)

4Reliability

If cobalt content is increased to improve electrical conductivity, then energy density increases, but cobalt elution worsens at high voltage

Engineering Contradiction:

Improveelectrical conductivityVSAvoidcobalt elution

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The invention optimizes the particle size parameter distribution rather than changing chemical composition. By using a bimodal size distribution, it maintains the necessary cobalt content for conductivity while reducing cobalt elution through the protective effect of small particles at high voltage interfaces.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS11489150B2Lithium ion battery and cathode active material therefor

Publication Date: 2022.11.01 SAMSUNG ELECTRONICS CO LTD

AI summary

Certain embodiments of the disclosure relate to a bimodal-type cathode active material for a lithium ion battery. The cathode active material includes a mixture of layered LiCoO2 large particles and manganese-based olivine structural small particles. The manganese-based olivine structural small particles may be represented by chemical formula LiCoxMnyFezPO4 (0≤x≤1, 0<y≤1, 0≤z≤1, x+y+z=1). An average particle diameter of the large particles may be 16 to 25 μm, and an average particle diameter of the small particles may be 1 to 3 μm. The cathode active material of the disclosure can achieve high energy density and high voltage stability.