Improved Electrochemical Li Extraction From Seawater And Other Dilute Li Sources Using Mixed Li An Na Layered Oxides

SUMMARY

• Use of Li in electric vehicle batteries, portable electronic devices, and stationary energy storage applications has expanded significantly in recent years, and this growth is expected to continue to increase.  The primary commercial technology used to recover Li is its extraction from concentrated brine water (83% of the market).  This technology utilizes solar energy in arid climates to evaporate water taking up to 12-18 months to complete, followed by a multi-step chemical treatment process and precipitation of Li₂CO₃. This time consuming/multi-step process has limited its commercial application.  Other Li extraction methods have been investigated (e.g., use of seawater, flow back water, geothermal reservoir waters) to address these inefficiencies.  Currently, use of seawater as a Li source is not economical due to seawater’s low Li concentrations (0.177 ppm).
• Development of an economical and environmentally friendly technique to extract Li from seawater could provide an abundant and sustainable source of this material for future applications.  Electrochemical extraction of Li from brines using Li-ion intercalation electrodes (e.g., olivine LiFePO₄, spinel l-MnO₂, layered LiNi_1/3Co_1/3Mn_1/3O₂(NMC)) have demonstrated acceptable Li selectivity/recovery rates, but the process does not tailor the materials composition/properties for use in an aqueous environment.
• Inventors at University of Chicago have demonstrated that use of a new material from the layered cobalt oxide family can deliver high selective Li extraction through material structural design.  A core-shell structured (NaLi)_1-xCoO₂ material was synthesized using a core Li-phase (Li_0.94 CoO₂), a shell Na-phase (Na_0.51CoO₂), and a transition intermediate phase through Na ion-exchange of the parent Li_1-xCoO₂ material. The developed electrochemical extraction process works by extracting (electrochemical intercalation) Li from a dilute Li solution and recovering (electrochemical deintercalation) Li in a fresh solution.   The core Li-phase limits layer expansion and prevents Na intercalation/promotes high Li selectivity, and the shell Na-phase/intermediate phase maintains electrode stability from further Na-ion exchange.
• Test results indicated that the (NaLi)_1-xCoO₂ electrode can extract Li selectively over a range of Li and Na solutions (e.g., Li:Na mol ratios between 1:100-1:20,000). In the lowest Li concentration solution (Li:Na ratio of 1:20,000) a recovery solution was realized with a Li:Na mol ratio of  ~ 7.6:1 in a single electrochemical extraction equivalent to a high Li selectivity of 1.5 x 10⁵.  These tests achieved the highest selectivity for Li reported to date, and indicated that the layered cobalt oxide material could be used to selectively extract Li from seawater.  As reported in the literature, the majority of previously evaluated materials were only capable of selectively extracting Li from highly concentrated Li brines.

FIGURE

ADVANTAGES

ADVANTAGES

• Use of (NaLi)_1-xCoO₂ allows for Li recovery from dilute Li solutions (e.g., seawater)
• The novel core-shell material composed of Li cobalt oxide selectively absorbs Li over Na ions which is required for economical Li extraction from seawater
• High Li extraction efficiency and product reusability over at least 20 operational cycles

APPLICATIONS

• Seawater Extraction of Li
• Li Batteries
• Li Electronic Devices

December 13, 2021

Proof of concept

Patent Pending

Licensing,Co-development

Chong Liu

• Process characterized/evaluated through laboratory tests