Lithium-Lanthanum Alloy Anode for Stable Lithium-Sulfur Cycling

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Solution Overview

Problem

Lithium-sulfur batteries face instability due to lithium dendrite formation and cathode active material loss, leading to reduced capacity and cycle lifetime, despite previous attempts to form protective layers that harden or expand during charging/discharging.

Innovation Solution

A lithium-lanthanum alloy is used as the negative electrode, with a lanthanum content of less than 15 wt% or 1 mol%, to stabilize plating/dissolution and improve battery efficiency, combined with a sulfur-based positive electrode and a specific electrolyte composition.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a solid electrolyte interface layer is formed on lithium metal to suppress direct reaction with electrolyte, then stability of negative electrode is improved, but the layer hardens or expands during charging/discharging causing structural collapse and lithium dendrite formation

Engineering Contradiction:

Improvestability of negative electrodeVSAvoidstructural stability of solid electrolyte interface layer

Core Design Contradiction:

ReliabilityVSStability of the object's composition

Solution Approach 1:

The patent changes the chemical composition parameters of the negative electrode from pure lithium metal to a lithium alloy containing aluminum (5-20 wt%) and/or beryllium (5-20 wt%). This compositional parameter change fundamentally alters the electrochemical behavior, enabling stable plating/stripping without forming a hardening protective layer, thus resolving the contradiction between initial stability and long-term structural stability.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent uses composite negative electrode materials combining lithium with aluminum and/or beryllium alloys. This composite approach creates a material that inherently maintains structural stability during cycling without requiring a separate protective interface layer, eliminating the structural collapse and dendrite formation issues that plague pure lithium metal electrodes with protective coatings.

Inventive Principle:

Principle #40Composite materials

2Quantity of substance

If lithium metal is used as negative electrode active material to achieve high theoretical specific capacity of 3,860 mAh/g, then battery capacity and energy density are improved, but lithium dendrite formation causes internal short circuit and dead lithium reducing cycle lifetime

Engineering Contradiction:

Improvebattery capacityVSAvoidcycle lifetime

Core Design Contradiction:

Quantity of substanceVSDuration of action of stationary object

Solution Approach 1:

The patent modifies the negative electrode material composition from pure lithium to lithium alloys with aluminum and/or beryllium. This parameter change maintains the high lithium content necessary for high capacity while the alloying elements fundamentally change the deposition behavior during cycling, preventing dendrite formation and enabling long cycle life while preserving the high theoretical specific capacity advantage.

Inventive Principle:

Principle #35Parameter changes

3Use of energy by moving object

If cathode active material sulfur is used in lithium-sulfur battery to achieve low atomic weight and high energy density, then energy density is improved, but cathode active material dissolves as lithium polysulfide and moves to anode causing capacity loss

Engineering Contradiction:

Improveenergy densityVSAvoidcathode active material loss

Core Design Contradiction:

Use of energy by moving objectVSLoss of substance

Solution Approach 1:

The patent introduces aluminum and/or beryllium as intermediary elements in the negative electrode that fundamentally alter the electrochemical interface. These intermediaries change the deposition mechanism of lithium ions, creating a stable plating/stripping process that prevents polysulfide shuttling and anode passivation, thereby retaining the high energy density benefit while eliminating the active material loss problem.

Inventive Principle:

Principle #24Intermediary (Mediator)

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 lithium-lanthanum alloy enhances the uniform electrochemical plating/elution of lithium, suppressing polysulfide decomposition and improving coulombic efficiency and cycle characteristics, thereby extending battery life and maintaining high energy density.

Implementation Method 1

the electrochemical reaction of the battery continuously occurs on the surface of lithium metal

Methodology Applied

Scientific EffectElectrochemical reaction: Redox Reactions

Implementation Method 2

stabilize plating/dissolution and improve battery efficiency

Methodology Applied

Scientific EffectPlating/dissolution: Electrodeposition

Implementation Method 3

suppressing polysulfide decomposition and improving coulombic efficiency

Methodology Applied

Scientific EffectSuppression of decomposition: Redox Reactions

Data Source

PatentUS20240072238A1Negative Electrode Including Lithium-Lanthanum Alloy and Lithium Ion Secondary Battery Including the Same

Publication Date: 2024.02.29 LG ENERGY SOLUTION LTD

AI summary

A negative electrode includes a lithium-lanthanum alloy. The negative electrode can be applied to a negative electrode for a lithium-sulfur battery. The lithium-sulfur battery including the alloy negative electrode has improved life characteristics and improved electrochemical efficiency.