Ammonium Phosphate Cathode Coating Against Metal Elution

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Solution Overview

Problem

Conventional secondary batteries experience a significant decrease in discharge capacity retention ratio due to side reactions between the lithium composite oxide cathode active material and the non-aqueous solvent in the electrolyte, leading to deteriorated cycle characteristics.

Innovation Solution

A cathode active material comprising lithium composite oxide particles coated with an ammonium phosphate compound, which prevents the transition metals from being reduced and eluted into the non-aqueous electrolyte, thereby suppressing oxidative decomposition of the solvent and maintaining discharge capacity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a conventional cathode active material is used, then the battery can operate, but the discharge capacity retention ratio significantly decreases along with repetition of charge/discharge cycle

Engineering Contradiction:

Improvedischarge capacity retention ratioVSAvoidcycle life

Core Design Contradiction:

ReliabilityVSDuration of action of moving object

Solution Approach 1:

A coating layer containing ammonium phosphate compound is introduced as an intermediary between the lithium composite oxide particles and the non-aqueous electrolyte. This coating layer prevents direct contact and chemical reaction between the cathode active material and electrolyte, thereby suppressing side reactions and maintaining discharge capacity retention ratio over repeated charge/discharge cycles

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The cathode active material is constructed as a composite structure with lithium composite oxide particles coated by ammonium phosphate compound. This composite material combines the high capacity characteristics of lithium composite oxide with the protective and stabilizing properties of ammonium phosphate coating, achieving both high initial capacity and excellent cycle stability

Inventive Principle:

Principle #40Composite materials

2Reliability

If the lithium composite oxide is coated to suppress side reactions, then the cycle characteristic improves, but the complexity of the cathode active material increases

Engineering Contradiction:

Improvecycle characteristicVSAvoidcathode active material structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The coating layer composition is precisely controlled with ammonium phosphate compound content at 1-10 wt% and thickness of 1-100 nm. By optimizing these parameters, the coating provides effective protection against side reactions while maintaining good ion conductivity and avoiding excessive complexity in the cathode active material structure

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

The coating layer effectively suppresses the decrease in discharge capacity retention ratio, enhancing the cycle characteristic of secondary batteries by preventing metal elution and solvent decomposition.

Implementation Method 1

suppressing oxidative decomposition of the solvent and maintaining discharge capacity

Methodology Applied

Scientific EffectOxidative decomposition: Oxidation

Data Source

PatentUS11791464B2Cathode active material and secondary battery using same

Publication Date: 2023.10.17 PANASONIC INTELLECTUAL PROPERTY MANAGEMENT CO LTD

AI summary

Provided is a cathode active material comprising particles each containing a lithium composite oxide; and a coating layer containing an ammonium phosphate compound and coating each of the particles.