Graphitizable Carbon Positive Electrode Overcharge Protection

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Solution Overview

Problem

Conventional safety mechanisms in lithium-ion batteries, such as safety valves and separator shutdowns, can fail to prevent overheating and explosions during overcharging, and there is a need for additional safety measures to enhance protection against overcharge-related hazards.

Innovation Solution

A positive electrode for non-aqueous electrolyte secondary batteries is designed with a carbonaceous coating film and a conductive auxiliary agent, where at least one of these components is graphitizable carbon, allowing for high resistance when the battery is overcharged, thereby reducing charge current and heat generation, and preventing boiling of the electrolyte solution.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional safety mechanisms (safety valve and separator shutdown) are used, then the battery structure includes protection against overcharge, but the electrolyte solution boils and safety valve opens causing potential damage to peripheral devices

Engineering Contradiction:

Improveovercharge protectionVSAvoidelectrolyte solution boiling and spraying

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent applies preliminary anti-action by incorporating graphitizable carbon into the positive electrode active material layer before overcharging occurs. This carbon component preemptively increases in resistance during overcharge conditions, counteracting the harmful effect of excessive current flow and preventing electrolyte boiling and safety valve activation.

Inventive Principle:

Principle #9Preliminary anti-action

2Reliability

If separator shutdown mechanism is used to block conductive ion paths at high temperature, then reaction progression is prevented, but separator material selection is limited and shrinkage may occur causing short circuit between electrodes

Engineering Contradiction:

Improvereaction stopping functionVSAvoidseparator material selection

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The patent introduces graphitizable carbon as an intermediary element within the positive electrode active material layer. This intermediary component provides overcharge protection through resistance increase, serving as a mediator that protects the battery without requiring restrictive separator materials or their associated limitations.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Reliability

If graphitizable carbon is used in the positive electrode active material layer, then resistance increases during overcharge reducing charge current and heat generation, but the electrode structure becomes more complex

Engineering Contradiction:

Improveovercharge safetyVSAvoidelectrode structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent merges the protective function with the active material itself by incorporating graphitizable carbon directly into the positive electrode active material layer. This combination integrates safety functionality into the existing electrode structure rather than adding separate protective components, thereby minimizing structural complexity.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The graphitizable carbon serves multiple functions: it acts as part of the active material participating in charge/discharge cycles while simultaneously providing overcharge protection through resistance increase. This multi-functionality eliminates the need for separate protective structures, reducing overall device complexity.

Inventive Principle:

Principle #6Universality (Multi-functionality)

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 use of graphitizable carbon in the positive electrode active material layer enhances safety by reducing exothermic heat and internal pressure, preventing battery explosions and improving heat resistance, thus ensuring safer operation during overcharge conditions.

Implementation Method 1

at least one of the carbonaceous coating film and the conductive auxiliary agent is graphitizable carbon

Methodology Applied

Scientific EffectElectrical Resistance: Electrical Resistance

Implementation Method 2

reducing exothermic heat and internal pressure, preventing battery explosions

Methodology Applied

Scientific EffectJoule Heating: Joule Heating

Data Source

PatentUS11652202B2Positive electrode for non-aqueous electrolyte secondary battery, and non-aqueous electrolyte secondary battery

Publication Date: 2023.05.16 ELIIY POWER

AI summary

The present invention provides a positive electrode for non-aqueous electrolyte secondary battery, having a novel overcharge protective function. The positive electrode for non-aqueous electrolyte secondary battery according to the present invention includes a positive electrode active material layer including a plurality of positive electrode active material particles, wherein the positive electrode active material layer comprises: a carbonaceous coating film formed on a surface of each of the positive electrode active material particles; and 0% by weight or more and 20% by weight or less of a conductive auxiliary agent disposed between the plurality of positive electrode active material particles, and at least one of the carbonaceous coating film and the conductive auxiliary agent is graphitizable carbon.