An Ecofriendly and Cost-Effective Method for Producing LiOH from Li₂SO₄ Using Indigenously Engineered Bipolar...

Area of Science:

• Electrochemistry
• Materials Science
• Chemical Engineering

Background:

• Lithium hydroxide (LiOH) is crucial for lithium-ion battery production.
• Conventional LiOH production from lithium sulfate (Li2SO4) involves complex steps.
• There is a need for more efficient and sustainable LiOH synthesis methods.

Purpose of the Study:

• To develop a convenient and efficient method for LiOH production from Li2SO4 using bipolar membrane electrodialysis (BMED).
• To optimize the BMED process by preparing and characterizing a novel bipolar membrane (BPM) with a sulfonated molybdenum sulfide (S-MoS2) interfacial layer.
• To evaluate the performance of the BMED process in terms of LiOH yield, purity, lithium recovery, and energy consumption.

Main Methods:

• Fabrication of a bipolar membrane (BPM) using solution casting, incorporating a sulfonated molybdenum sulfide (S-MoS2) interfacial layer, sulfonated poly(ether sulfone) for the cation exchange layer (CEL), and quaternized poly(phenylene oxide) for the anion exchange layer (AEL).
• Characterization of the BPM and S-MoS2 catalyst using techniques such as NMR, FE-SEM, UTM, and XRD.
• Evaluation of BMED operational parameters, including applied potentials and 'Acid mode' operation with dilute H2SO4 in the acid compartment.
• Analysis of current-voltage curves (CVCs) and measurement of sulfate flux.

Main Results:

• The prepared BPM effectively facilitated the electrodialysis of Li2SO4 to produce LiOH.
• The BMED process achieved a LiOH concentration of 0.62 M from a 0.4 M Li2SO4 feed solution.
• Operating in 'Acid mode' significantly reduced sulfate ion migration, lowering sulfate flux and increasing product purity.
• The process demonstrated over 90% lithium recovery with an energy consumption of 1.77 kWh kg-1, yielding high-purity, battery-grade LiOH.

Conclusions:

• The bipolar membrane electrodialysis (BMED) process offers a highly effective and convenient route for producing lithium hydroxide (LiOH) from lithium sulfate (Li2SO4).
• The novel BPM with an S-MoS2 interfacial layer enhances water splitting and process efficiency.
• This BMED approach provides a sustainable alternative to conventional methods, reducing chemical usage and separation steps for battery-grade LiOH production.