Lithium Manganese Positive Electrode Material Stabilization

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Solution Overview

Problem

Lithium manganese composite oxide secondary batteries face challenges in achieving high energy density and stability due to Mn substitution with Fe, leading to capacity drops and increased costs, particularly when the composition ratio of Fe approaches 1, destabilizing the crystal structure and reducing discharge energy.

Innovation Solution

The use of a positive electrode active material represented by the formula Lia(FexNiyMn2-x-y)O4 or Lia(FexNiyMn2-x-y-zAz)O4, where 0.2<x≦1.2, 0<y<0.5, and 0≦a≦1.2, with specific ratios of Fe, Ni, and optional elements like Li, B, Na, Mg, Al, K, and Ca, to stabilize the crystal structure and enhance discharge energy while reducing costs.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If a part of Mn is substituted with Fe to reduce cost and improve safety, then resource availability and cost are improved, but capacity retention rate deteriorates and crystal structure destabilizes

Engineering Contradiction:

Improveresource availabilityVSAvoidcapacity retention rate

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

The patent uses a composite substitution approach where Fe is combined with Ni and other elements (Al, Mg, Ca, Ti, Co, Cr) to create a multi-element doped lithium manganese oxide. This composite material strategy allows Fe to provide cost benefits while the other elements compensate for the capacity retention issues caused by Fe substitution, thereby resolving the contradiction between resource availability and reliability

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent applies local quality by optimizing the specific composition ratios of different substitution elements at different positions in the spinel structure. By carefully controlling the distribution and concentration of Fe, Ni, and other elements, the patent maintains stable crystal structure in critical regions while allowing Fe substitution in regions where it benefits cost, thus balancing resource availability with capacity retention

Inventive Principle:

Principle #3Local quality

2Quantity of substance

If the composition ratio of Fe approaches 1 to maximize cost reduction, then cost is reduced, but crystal structure destabilizes and discharge energy decreases

Engineering Contradiction:

ImprovecostVSAvoidcrystal structure stability

Core Design Contradiction:

Quantity of substanceVSStability of the object's composition

Solution Approach 1:

The patent optimizes the composition parameters by precisely controlling the substitution ratios of Fe, Ni, and other elements. Instead of using pure Fe substitution, the patent adjusts the parameters to achieve an optimal balance where Fe content is maximized for cost reasons while Ni and other elements are added in specific amounts to maintain crystal structure stability, thus resolving the contradiction between cost reduction and structural stability

Inventive Principle:

Principle #35Parameter changes

3Reliability

If a lithium manganese composite oxide is used to ensure safety and reduce cost, then safety and cost are improved, but energy density is limited due to 4 V-level action potential

Engineering Contradiction:

ImprovesafetyVSAvoidenergy density

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The patent changes the electrochemical potential parameter by optimizing the multi-element substitution composition. The specific ratios of Fe, Ni, and other elements modify the electronic structure and redox potentials of the material, enabling it to achieve higher discharge potentials and improved energy density while maintaining the safety advantages of lithium manganese oxide, thus resolving the contradiction between safety and energy density

Inventive Principle:

Principle #35Parameter changes

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 composition stabilizes the crystal structure, reduces costs, and increases discharge energy, while suppressing capacity drops with cycles, thereby improving the overall performance and longevity of the secondary battery.

Implementation Method 1

a positive electrode active material for a secondary battery... for a lithium secondary battery

Methodology Applied

Scientific EffectElectrochemical reaction:

Implementation Method 2

a lithium diffusion route... Li insertion

Methodology Applied

Scientific EffectIon diffusion: Diffusion

Data Source

PatentUS9299475B2Positive electrode active material for secondary battery and secondary battery using the same

Publication Date: 2016.03.29 NEC CORP

AI summary

A positive electrode active material for a lithium ion secondary battery having high discharge energy and capable of suppressing capacity drop with cycles and a secondary battery using the same are provided at lower cost. A positive electrode active material for a secondary battery according to a first aspect of the exemplary embodiment is represented by the following formula (I): Lia(FexNiyMn2-x-y)O4 (I) where 0.2<x≦1.2, 0<y<0.5 and 0≦a≦1.2. Furthermore, a positive electrode active material for a secondary battery according to a second aspect of the exemplary embodiment is represented by the following formula (II): Lia(FexNiyMn2-x-y-zAz)O4 (II) where 0.2≦x≦1.2, 0<y<0.5, 0≦a≦1.2 and 0<z≦0.3; A is at least one selected from the group consisting of Li, B, Na, Mg, Al, K and Ca.