Olivine Cathode Composition with Cr Doping for Energy Density

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Solution Overview

Problem

Olivine structured phosphate cathode materials for rechargeable lithium batteries face challenges with low electrical conductivity and insufficient energy density, limiting their commercialization despite potential safety and cost advantages.

Innovation Solution

Non-stoichiometric LiFe1-x-zMnxCrx(PO4)c cathode materials with specific molar ratios and Cr doping improve energy density and electrochemical performance by optimizing the composition and phosphate stoichiometry, enhancing Mn content without decreasing energy density.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If Mn content is increased to improve energy density, then average voltage increases, but discharge capacity decreases

Engineering Contradiction:

Improveaverage voltageVSAvoiddischarge capacity

Core Design Contradiction:

Use of energy by moving objectVSQuantity of substance

Solution Approach 1:

The patent applies parameter changes by precisely controlling the Mn content within the range 0.6 ≤ x ≤ 0.95 in LiFe1-x-zMnxCrz(PO4)c and the phosphate stoichiometry 0.97 ≤ c ≤ 1.03 to optimize the balance between average voltage and discharge capacity, achieving maximum energy density

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent uses composite materials by combining multiple transition metals (Fe, Mn, Cr) in a doped olivine structure LiFe1-x-zMnxCrz(PO4)c, creating a composite cathode material that integrates the advantages of each metal: Fe for structural stability, Mn for high voltage, and Cr for conductivity enhancement

Inventive Principle:

Principle #40Composite materials

2Reliability

If Cr doping is increased to improve electrical conductivity, then electrochemical performance improves, but structural stability may deteriorate

Engineering Contradiction:

Improveelectrochemical performanceVSAvoidstructural stability

Core Design Contradiction:

ReliabilityVSStability of the object's composition

Solution Approach 1:

The patent applies parameter changes by limiting the Cr doping level to 0 ≤ z ≤ 0.05 and optimizing the phosphate stoichiometry 0.97 ≤ c ≤ 1.03, which enhances electrical conductivity through Cr doping while maintaining structural stability through controlled doping levels and non-stoichiometric phosphate composition

Inventive Principle:

Principle #35Parameter changes

3Use of energy by moving object

If non-stoichiometric composition is used to improve energy density, then manufacturing precision requirements increase, but electrochemical performance improves

Engineering Contradiction:

Improveenergy densityVSAvoidcomposition control

Core Design Contradiction:

Use of energy by moving objectVSManufacturing precision

Solution Approach 1:

The patent applies parameter changes by defining specific ranges for composition parameters (0.6 ≤ x ≤ 0.95 for Mn content, 0 ≤ z ≤ 0.05 for Cr doping, 0.97 ≤ c ≤ 1.03 for phosphate stoichiometry) that optimize energy density while providing clear manufacturing specifications for controlling composition precision

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent applies local quality by introducing non-stoichiometric phosphate content (c ≠ 1.0) specifically at the crystal structure level to enhance electrochemical performance and energy density, while maintaining overall compositional control through defined parameter ranges

Inventive Principle:

Principle #3Local quality

Data Source

PatentEP3180812B1Olivine composition with improved cell performance

Publication Date: 2019.02.27 UMICORE(BE)

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AI summary

An olivine cathode material having the formula LiaFe1-x-y-zMnxD(y+z)(PO4)c,wherein a, c, x, y and z represent molar amounts, wherein D = Mg and/or Cr, wherein y represent the amount of Mg and z represents the amount of Cr, wherein 1.04<a<1.15; wherein 0.97<(2*c/(a+1))<1.07; wherein 0.6<x<1-y-z; wherein 0<y+z<0.1. These material show improved cathode properties in lithium based rechargeable batteries.