Lithium Primary Battery Negative Electrode Coating for Low-Temperature Discharge

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Solution Overview

Problem

Lithium primary batteries face challenges in maintaining high performance, particularly in low-temperature environments and after high-temperature storage, due to voltage drops and increased polarization caused by coating films on the negative electrode surface, which are not effectively addressed by existing solutions.

Innovation Solution

A laminated structure comprising a lithium carboxylate layer and a carbon layer on the negative electrode surface, where the lithium carboxylate layer suppresses the formation of insulating coatings like lithium fluoride, and the carbon layer stabilizes the electrolyte interface, reducing polarization and impedance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a coating film is formed on the negative electrode surface during production, then the negative electrode is protected, but the coating film acts as a resistance component increasing polarization and causing voltage drop during discharge

Engineering Contradiction:

Improvenegative electrode protectionVSAvoidpolarization and voltage drop

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The invention changes the chemical composition parameters of the coating film by controlling the ratio of lithium carbonate to lithium fluoride. By adjusting these compositional parameters, the film's resistance properties are optimized to reduce polarization while maintaining protective functions.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The coating film is designed as a composite material containing both lithium carbonate and lithium fluoride in specific ratios. This composite structure combines the protective properties of lithium carbonate with the stability of lithium fluoride, achieving both protection and reduced resistance.

Inventive Principle:

Principle #40Composite materials

2Stability of the object's composition

If lithium fluoride forms on the negative electrode surface through reaction with fluorine from electrolyte or graphite fluoride, then the electrode is stabilized, but lithium fluoride being an insulator significantly increases negative electrode polarization during discharge

Engineering Contradiction:

Improveelectrode stabilityVSAvoidnegative electrode polarization

Core Design Contradiction:

Stability of the object's compositionVSObject-affected harmful factors

Solution Approach 1:

The invention changes the concentration parameter of lithium fluoride in the coating film by controlling the lithium carbonate to lithium fluoride ratio. By reducing the lithium fluoride content through this parameter change, the insulating effect is minimized while maintaining the stability provided by lithium fluoride.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

Lithium carbonate acts as an intermediary substance that moderates the formation and impact of lithium fluoride. The lithium carbonate layer controls the interface between the negative electrode and electrolyte, reducing the direct harmful effects of lithium fluoride formation while maintaining electrode stability.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Power

If the battery is discharged at large current, then higher power output is achieved, but the voltage drop in the initial discharge stage becomes more evident due to increased polarization

Engineering Contradiction:

Improvepower outputVSAvoidvoltage drop in initial discharge stage

Core Design Contradiction:

PowerVSObject-affected harmful factors

Solution Approach 1:

The invention changes the electrical resistance parameter of the coating film by optimizing the lithium carbonate to lithium fluoride ratio. This parameter change reduces the film's resistance to ion transport, allowing higher current discharge with minimal voltage drop while maintaining the required power output.

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

This configuration enhances large-current discharge characteristics in low temperatures and maintains stable performance even after high-temperature storage, with minimal voltage drop and impedance increase, thereby improving the overall battery performance and longevity.

Implementation Method 1

a lithium carboxylate layer which is formed on a surface of the lithium or lithium alloy... the lithium carboxylate layer suppresses the formation of insulating coatings like lithium fluoride

Methodology Applied

Scientific EffectChemical reaction suppression:

Implementation Method 2

the carbon layer stabilizes the electrolyte interface, reducing polarization and impedance

Methodology Applied

Scientific EffectInterface stabilization:

Implementation Method 3

Methodology Applied

Scientific EffectPolarization reduction:

Data Source

PatentUS8236451B2Negative electrode for lithium primary battery and lithium primary battery

Publication Date: 2012.08.07 PANASONIC HOLDINGS CORP

AI summary

A lithium primary battery includes a positive electrode, a negative electrode, a separator, a positive electrode case, a negative electrode case, a gasket, and a non-aqueous electrolyte. The negative electrode includes: lithium or a lithium alloy; a lithium carboxylate layer formed on a surface of the lithium or lithium alloy; and a carbon layer formed on a surface of the lithium carboxylate layer. This configuration allows the lithium primary battery to have suppressed negative electrode polarization during discharge and improved large-current discharge characteristics in a low temperature environment and after high temperature storage.