Olivine Lithium Composite Oxide for High-Rate Battery

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Solution Overview

Problem

Lithium ion secondary batteries using olivine manganese type positive electrode active materials face challenges with low capacity and current density, leading to poor rate characteristics.

Innovation Solution

A positive electrode active material with a lithium composite oxide structure represented by Li1+AMnXM1−X(PO4)1+B, where A/B ratio is between 2 and 7, and X is between 0.3 and 1, incorporating metal elements like Fe, Ni, Co, Ti, Cu, Zn, Mg, V, and Zr, with a carbon coating to enhance electroconductivity and crystallinity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If olivine manganese type positive electrode active material is used to achieve high reaction potential (4.1 V) and high energy density, then energy density is improved, but electroconductivity and Li ion diffusibility are low resulting in low capacity and poor rate characteristics

Engineering Contradiction:

Improveenergy densityVSAvoidrate characteristics

Core Design Contradiction:

Use of energy by moving objectVSProductivity

Solution Approach 1:

The invention changes the chemical composition parameters by incorporating multiple metal elements (Fe, Ni, Co, Ti, Cu, Zn, Mg, V, Zr) in specific ratios, where Mn content is 0.01-0.80, Fe is 0.01-0.50, Ni is 0.01-0.50, Co is 0.01-0.50, and other elements are each 0.001-0.10. This compositional parameter optimization simultaneously improves electroconductivity, Li ion diffusibility, and maintains high energy density through the high potential of manganese.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The invention creates a composite positive electrode active material by combining multiple metal oxides/hydroxides/carbonates (Mn, Fe, Ni, Co, Ti, Cu, Zn, Mg, V, Zr) in a specific molar ratio range. This composite structure synergistically combines the high potential of Mn with the good electroconductivity and structural stability of other metals, achieving both high energy density and improved rate characteristics.

Inventive Principle:

Principle #40Composite materials

2Productivity

If olivine iron type positive electrode active material is used to achieve good electroconductivity and Li ion diffusibility, then rate characteristics are improved, but reaction potential is low (3.4 V) resulting in low energy density

Engineering Contradiction:

ImproveelectroconductivityVSAvoidenergy density

Core Design Contradiction:

ProductivityVSUse of energy by moving object

Solution Approach 1:

The invention merges the advantages of different metal-based materials by combining Mn (high potential), Fe (good electroconductivity), and other metals (Ni, Co, Ti, Cu, Zn, Mg, V, Zr) in a unified olivine structure. The synergistic combination allows the material to simultaneously achieve high energy density from Mn and good electroconductivity from Fe and other metals.

Inventive Principle:

Principle #5Merging (Combining)

3Quantity of substance

If layered oxide type positive electrode active material such as LiCoO2 is used to achieve high capacity, then capacity is improved, but structural stability is poor leading to heat generation and ignition when overcharged

Engineering Contradiction:

ImprovecapacityVSAvoidsafety

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

The invention converts the potential harm of oxygen release in layered oxides into a benefit by using the olivine structure where oxygen is tightly bound in a covalent bond with phosphorus. This structural transformation eliminates oxygen release while maintaining high capacity, achieving both high energy density and improved safety.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

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 a high-capacity and high-rate characteristic non-aqueous secondary battery, preventing metal precipitation and improving safety by maintaining structural stability and enhancing Li ion diffusibility.

Implementation Method 1

covering the surface of the olivine type positive electrode active material by a carbon material, and enhancing the crystallinity of the carbon layer and improving the electroconductivity

Methodology Applied

Scientific EffectElectroconductivity: Conduction (electrical)

Implementation Method 2

since oxygen and phosphorus are in a covalent bond, oxygen is less likely to be released to provide high safety

Methodology Applied

Scientific EffectCovalent bond: Chemical Bonding

Implementation Method 3

when Li atoms are deintercalated by charging, the structure becomes instable... improving the Li diffusibity

Methodology Applied

Scientific EffectIon diffusion: Diffusion

Data Source

PatentUS9224512B2Positive electrode active material for non-aqueous secondary battery and manufacturing method thereof, as well as non-aqueous secondary battery using positive electrode active material

Publication Date: 2015.12.29 PROTERIAL LTD

AI summary

A positive electrode active material for a non-aqueous secondary battery having high capacity and high rate characteristics is intended to be provided. Further, a positive electrode for a non-aqueous secondary battery and a non-aqueous secondary battery are intended to be provided by using the positive electrode active material. The positive electrode active material for the non-aqueous secondary battery contains a lithium composite oxide having an olivine structure represented by the chemical formula: Li1+AMnXM1−X(PO4)1+B in which A>0, B>0, M represents a metal element, M in the chemical formula is one or more metal elements selected from Fe, Ni, Co, Ti, Cu, Zn, Mg, V, and Zr, the ratio A/B in the chemical formula is within a range of: 2<A/B≦7, and the value of X is within a range of: 0.3≦X<1.