Positive Electrode Active Material with Concentration-Graded Covering Layers

Solution Overview

Problem

Current lithium ion secondary batteries face issues with capacity deterioration, reduced lifespan, and thermal stability due to insufficient filling ability and cycle characteristics of transition metal oxides, particularly with the concentration distribution of Ni and Mn in the covering layers.

Innovation Solution

A positive electrode active material with a composite particle structure, where Ni and Mn have a concentration distribution centered from the surface, with specific mole fraction ranges and ratios within the covering layer, enhancing the cycle and high-temperature preservation characteristics.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a small amount of LiMn1/3Co1/3Ni1/3O2 is mixed with a positive electrode active material and the surface is covered to improve cycle characteristics, then filling ability and cycle characteristic improve, but high-temperature preservation characteristic remains insufficient

Engineering Contradiction:

Improvecycle characteristicVSAvoidhigh-temperature preservation characteristic

Core Design Contradiction:

ReliabilityVSTemperature

Solution Approach 1:

The patent applies local quality by creating a multi-layer covering structure with different compositions at different depths. The first covering layer (Li-rich layer) and second covering layer (Li-poor layer) have distinct chemical compositions optimized for their respective functions: the Li-rich layer provides thermal stability at high temperature, while the Li-poor layer maintains electrochemical activity for cycling performance. This spatial differentiation of material properties resolves the contradiction between cycle characteristic and high-temperature preservation.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent uses composite materials by combining multiple oxide layers with different compositions on the particle surface. The composite structure includes the base positive electrode active material (LiCoO2 or LiNi0.8Co0.1Mn0.1O2) covered by a first oxide layer (Li2SiO3, Li2GeO3, or Li4SiO4) and a second oxide layer (LiMn1/3Co1/3Ni1/3O2 or LiNi0.8Co0.1Mn0.1O2). This composite material system simultaneously achieves improved cycle characteristics and high-temperature preservation.

Inventive Principle:

Principle #40Composite materials

2Quantity of substance

If charging voltage is increased to obtain higher energy density, then energy density increases, but capacity deterioration occurs and battery lifespan is reduced

Engineering Contradiction:

Improveenergy densityVSAvoidbattery lifespan

Core Design Contradiction:

Quantity of substanceVSDuration of action of stationary object

Solution Approach 1:

The patent applies beforehand cushioning by pre-forming protective covering layers on the positive electrode active material particles before battery assembly. These covering layers (particularly the Li-rich first oxide layer and Li-poor second oxide layer) act as protective barriers that cushion the material against degradation during high-voltage charging operations. The covering layers prevent direct exposure of the active material to harsh electrochemical conditions, thereby extending battery lifespan while enabling higher energy density operation.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

3Reliability

If surface covering is performed to improve cycle characteristic, then cycle characteristic improves, but thermal stability improvement is insufficient

Engineering Contradiction:

Improvecycle characteristicVSAvoidthermal stability

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent applies local quality by creating a multi-layer covering structure with different compositions at different depths. The first covering layer (Li-rich layer) and second covering layer (Li-poor layer) have distinct chemical compositions optimized for their respective functions: the Li-rich layer provides thermal stability at high temperature, while the Li-poor layer maintains electrochemical activity for cycling performance. This spatial differentiation of material properties resolves the contradiction between cycle characteristic and high-temperature preservation.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent uses composite materials by combining multiple oxide layers with different compositions on the particle surface. The composite structure includes the base positive electrode active material (LiCoO2 or LiNi0.8Co0.1Mn0.1O2) covered by a first oxide layer (Li2SiO3, Li2GeO3, or Li4SiO4) and a second oxide layer (LiMn1/3Co1/3Ni1/3O2 or LiNi0.8Co0.1Mn0.1O2). This composite material system simultaneously achieves improved cycle characteristics and high-temperature preservation.

Inventive Principle:

Principle #40Composite materials

Data Source

PatentUS10629904B2Positive electrode active material, positive electrode, battery, battery pack, electronic device, electric vehicle, power storage device, and power system

Publication Date: 2020.04.21 MURATA MFG CO LTD

AI summary

A positive electrode active material includes: a composite particle that includes a particle containing a lithium transition metal composite oxide of Li and Co and a layer that is provided on a surface of the particle and includes an oxide of Li, Ni and Mn. Ni and Mn have a concentration distribution centered on the center from a surface of the composite particle, in a depth range in which a ratio d (%) satisfies 0.04%≤d≤0.20%, a mole fraction rn of Ni and a mole fraction rm of Mn are within ranges of 0.05≤rn and 0.05≤rm, respectively, and a ratio rn2/rn1 and a ratio rm2/rm1 are within ranges of 0.85≤rn2/rn1≤1.0 and 0.85≤rm2/rm1≤1.0, respectively.