Lithium-Metal Battery Electrolyte and Layer Density for Stable Cycling

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Solution Overview

Problem

Lithium-metal secondary batteries face issues with uneven lithium deposition, poor charge-discharge efficiency, and short cycle characteristics due to expansion and contraction of electrodes, as well as oxidative decomposition of electrolytes, leading to reduced lithium ion concentration and decomposition of the electrolytic solution.

Innovation Solution

A lithium-metal secondary battery with a highly reduction-resistant or oxidation-resistant electrolytic solution and a lithium metal layer of controlled relative density (40-85% or 70-95%) is used, promoting lithium ion diffusion and maintaining concentration, thereby improving charge-discharge cycle characteristics by adjusting the deposition morphology and suppressing electrolyte decomposition.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Stability of the object's composition

If a space is provided to prevent pressure from being applied to a lithium deposited site, then expansion and contraction due to charge and discharge can be eased, but lithium deposition becomes uneven and the contact area with electrolytic solution is increased

Engineering Contradiction:

Improveelectrode expansion and contractionVSAvoidlithium deposition uniformity

Core Design Contradiction:

Stability of the object's compositionVSReliability

Solution Approach 1:

The invention changes the physical parameter of the lithium metal layer by controlling its relative density within the range of 40-85%. This parameter change allows the lithium metal layer to maintain adequate contact with the electrolyte while accommodating expansion and contraction during charge-discharge cycles, thereby improving deposition uniformity and preventing electrolyte decomposition.

Inventive Principle:

Principle #35Parameter changes

2Stability of the object's composition

If a highly concentrated electrolytic solution is used, then oxidation-reduction stability can be improved, but carbonic acid esters easily react with lithium metal and the amount of electrolytic solution decomposed is increased

Engineering Contradiction:

Improveoxidation-reduction stabilityVSAvoidelectrolyte decomposition

Core Design Contradiction:

Stability of the object's compositionVSLoss of substance

Solution Approach 1:

The invention changes the concentration parameter of the electrolyte to a highly concentrated range (2-6 mol/L), which improves oxidation-reduction stability. Simultaneously, it controls the lithium metal layer density to reduce harmful reactions between carbonic acid esters and lithium metal, thereby suppressing electrolyte decomposition.

Inventive Principle:

Principle #35Parameter changes

3Object-affected harmful factors

If ether-based solvents are used with high electrolyte concentration, then oxidative decomposition reactions can be suppressed, but lithium ions near positive electrode rapidly decrease in discharge reactions

Engineering Contradiction:

Improveoxidative decompositionVSAvoidlithium ion concentration

Core Design Contradiction:

Object-affected harmful factorsVSQuantity of substance

Solution Approach 1:

The invention optimizes the electrolyte concentration parameter to 2-6 mol/L and controls the lithium metal layer relative density to 40-85%. This combination maintains adequate lithium ion concentration near the positive electrode during discharge while suppressing oxidative decomposition of the ether-based solvent.

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 controlled lithium metal layer density enhances charge-discharge efficiency and cycle life by maintaining lithium ion concentration and reducing electrolyte decomposition, contributing to improved energy efficiency and extended battery life.

Implementation Method 1

lithium deposition becomes uneven, and the contact area with an electrolytic solution is increased. In particular, carbonic acid esters easily react with lithium metal, and thus the amount of the electrolytic solution decomposed is increased

Methodology Applied

Scientific EffectLithium deposition dissolution: Electrolysis

Implementation Method 2

a highly reduction-resistant electrolytic solution (e.g., electrolytic solution 16 described below), including 2 to 6 mol of electrolyte per L of solvent and also having a lithium deposition dissolution efficiency of 98.5% or more

Methodology Applied

Scientific EffectIonic conduction: Conduction (electrical)

Data Source

PatentUS20230317934A1Lithium-metal secondary battery and method for manufacturing the same

Publication Date: 2023.10.05 HONDA MOTOR CO LTD

AI summary

A lithium-metal secondary battery, which includes a highly reduction-resistant electrolytic solution, including 2 to 6 mol of electrolyte per L of solvent and also having a lithium deposition dissolution efficiency of 98.5% or more, which lithium deposition dissolution efficiency is the proportion of the amount of redissolution of lithium to the amount thereof deposited on the copper surface, wherein the relative density of a lithium metal layer in a negative electrode is 40 to 85%. In addition, a lithium-metal secondary battery, which includes a highly oxidation-resistant electrolytic solution, including 2 to 6 mol of electrolyte per L of solvent and also having a voltage of 5.5 V or more when the current density is 0.4 mA/cm2 using lithium as a counter electrode and platinum as a working electrode, wherein the relative density of a lithium metal layer in a negative electrode is 70 to 95%.