Vanadium-Graded LiFePO4 Cathode Material for Higher Power Output

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Solution Overview

Problem

Lithium iron phosphate-based cathode active materials for secondary batteries have relatively low ionic conductivity and insufficient power properties, limiting their application in high-power devices such as electric vehicles.

Innovation Solution

A cathode active material for lithium secondary batteries is developed, featuring lithium iron phosphate-based particles with a surface portion and a central portion both containing vanadium, where the surface portion has a higher vanadium concentration than the central portion, and optionally includes titanium, to enhance lithium ion conductivity and prevent resistance increases.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If lithium iron phosphate-based cathode active material is used, then high operational voltage and energy density are achieved, but ionic conductivity and power properties are insufficient

Engineering Contradiction:

Improveenergy densityVSAvoidionic conductivity

Core Design Contradiction:

Use of energy by moving objectVSReliability

Solution Approach 1:

The patent applies local quality by creating a non-uniform vanadium distribution within the lithium iron phosphate particle. The surface portion contains a higher concentration of vanadium (first weight amount) compared to the central portion (second weight amount). This localized doping strategy enhances ionic conductivity specifically at the particle surface where lithium ion insertion/extraction occurs most actively, while maintaining the bulk structural integrity and high energy density characteristics of the lithium iron phosphate material.

Inventive Principle:

Principle #3Local quality

2Use of energy by moving object

If lithium iron phosphate-based cathode active material is used, then high operational voltage is achieved, but power properties are insufficient

Engineering Contradiction:

Improveoperational voltageVSAvoidpower output

Core Design Contradiction:

Use of energy by moving objectVSPower

Solution Approach 1:

The patent enhances power output by locally concentrating vanadium in the surface portion of the lithium iron phosphate particles. This surface-enriched vanadium distribution reduces surface resistance and improves electron conductivity at the critical interfaces where electrochemical reactions occur, thereby enhancing power delivery capabilities while preserving the high operational voltage characteristic of lithium iron phosphate.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent modifies the chemical composition parameters of the lithium iron phosphate material by introducing vanadium at specific concentrations in specific regions. The surface portion contains a higher vanadium concentration (first weight amount) compared to the central portion (second weight amount), with the vanadium content controlled within specific ranges (0.001≤d≤0.85 in the formula Li a Fe b M c V d P e O 4). This parameter optimization enhances electrical conductivity and power properties while maintaining structural stability.

Inventive Principle:

Principle #35Parameter changes

3Reliability

If vanadium is added to improve conductivity, then ionic conductivity increases, but surface resistance may increase if distribution is uniform

Engineering Contradiction:

Improveionic conductivityVSAvoidsurface resistance

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent resolves this contradiction by implementing non-uniform vanadium distribution. The surface portion contains a higher concentration of vanadium (first weight amount greater than second weight amount in central portion), which specifically addresses surface resistance issues. This localized high-concentration vanadium doping at the particle surface enhances ionic conductivity where it is most needed for lithium ion insertion/extraction, while the lower concentration in the central portion prevents excessive resistance. The concentration gradient section transitions smoothly between these regions.

Inventive Principle:

Principle #3Local quality

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 improves the electrical properties and power output of lithium secondary batteries by increasing lithium ion diffusion rates and reducing surface resistance, particularly at low temperatures, thereby enhancing their performance in high-power devices like electric vehicles.

Implementation Method 1

increasing lithium ion diffusion rates

Methodology Applied

Scientific EffectDiffusion: Diffusion

Implementation Method 2

reducing surface resistance

Methodology Applied

Scientific EffectElectrical Resistance: Electrical Resistance

Data Source

PatentEP4379854A1Cathode active material for lithium secondary battery and lithium secondary battery including the same

Publication Date: 2024.06.05 SK ON CO LTD

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AI summary

Cathode active materials for lithium secondary batteries and lithium secondary batteries including the cathode active materials are disclosed. In an embodiment, a cathode active material includes a lithium iron phosphate-based particle including a surface portion and a central portion, both of which includes vanadium (V). A total weight of the vanadium contained in the lithium iron phosphate-based particle includes a first weight amount of vanadium contained in the surface portion of the lithium iron phosphate-based particle and a second weight amount of vanadium contained in the central portion of the lithium iron phosphate-based particle, and the first weight amount is greater than the second weight amount.