Lithium Salt Coated Positive Electrode for Battery Corrosion

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Solution Overview

Problem

The existing methods for producing positive electrodes for nonaqueous secondary batteries using lithium-metal complex oxides result in corrosion of the current collector due to the elution of Li ions, leading to decreased capacity and output characteristics, as the use of water in the production process creates strong alkali conditions that further exacerbate the corrosion.

Innovation Solution

A coated positive electrode active material with a lithium salt coating of 20 to 50 nm thickness is applied to the lithium-metal complex oxide, preventing Li ion elution and corrosion of the current collector, while allowing for appropriate desorption and insertion of ions during battery use, thereby maintaining battery capacity and output characteristics.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If water is used in the production process of positive electrode, then the positive paste becomes strong alkali due to LiOH generation, but this causes corrosion of the positive current collector and elution of Li ions from the active material

Engineering Contradiction:

Improveease of manufactureVSAvoidreliability

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The surface of the positive electrode active material is preliminarily coated with lithium carbonate before the positive paste is prepared. This preliminary coating action prevents Li ion elution during subsequent water-based paste preparation, allowing easy manufacture without compromising reliability

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

Lithium carbonate coating serves as an intermediary layer between the positive electrode active material and the aqueous environment. This intermediary prevents direct contact between water and the active material, blocking the harmful chemical reactions while allowing the manufacturing process to proceed

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If Li ions are eluted from the positive electrode active material to maintain chemical equilibrium during corrosion, then the current collector continues to corrode, but this also causes decrease in capacity and collapse of crystal structure of the active material

Engineering Contradiction:

ImprovereliabilityVSAvoidcapacity

Core Design Contradiction:

ReliabilityVSQuantity of substance

Solution Approach 1:

The lithium carbonate coating, which might seem to add complexity, actually converts the harmful elution process into a beneficial protective mechanism. It allows controlled Li ion release to maintain equilibrium while preventing uncontrolled elution that would damage the active material structure and reduce capacity

Inventive Principle:

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

3Reliability

If the positive current collector corrodes due to strong alkali conditions, then the current collecting property greatly lowers, but this also causes decrease in battery output characteristics

Engineering Contradiction:

ImprovereliabilityVSAvoidoutput characteristics

Core Design Contradiction:

ReliabilityVSPower

Solution Approach 1:

The lithium carbonate coating provides preliminary anti-action against the corrosive alkali environment by preventing Li ion elution. This preliminary protection maintains the structural integrity of the current collector, ensuring both reliability and power output characteristics are preserved

Inventive Principle:

Principle #9Preliminary anti-action

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 coated positive electrode active material effectively prevents corrosion of the current collector and maintains the structural integrity and capacity of the battery, ensuring superior current collecting properties and output characteristics by controlling Li ion elution and pH levels during production and use.

Implementation Method 1

the surface of a positive electrode active material made of lithium-metal complex oxide is coated with a coating of lithium salt having an average thickness of 20 to 50 nm... preventing Li ion elution and corrosion of the current collector

Methodology Applied

Scientific EffectIon elution prevention:

Implementation Method 2

allowing for appropriate desorption and insertion of ions during battery use, thereby maintaining battery capacity and output characteristics

Methodology Applied

Scientific EffectIon desorption and insertion: Desorption

Implementation Method 3

mixing the positive electrode active material made of lithium-metal complex oxide and others with water produces LiOH, so that the positive paste becomes strong alkali

Methodology Applied

Scientific EffectChemical reaction producing LiOH:

Data Source

PatentEP2209152B1Coated positive electrode active material, positive electrode for nonaqueous secondary battery, nonaqueous secondary battery, and their production methods

Publication Date: 2022.09.14 SUMITOMO METAL MINING CO LTD

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AI summary

Disclosed is a nonaqueous secondary battery (100) comprising a positive electrode (155) having a positive current collector (151) made of a metal, and a positive electrode active material (153) composed of a lithium-metal complex oxide. The surface of the positive electrode active material (153) is coated with a lithium salt (158) having an average thickness of 20-50 nm.