The role of solid solutions in iron phosphate-based electrodes for selective electrochemical lithium extraction

Self-Oxidated Hybrid Conductive Network Enables Efficient Electrochemical Lithium Extraction Under High-Altitude Environment

The electrochemical deintercalation method has been considered as an effective way to address the demand for lithium resources due to its environmental friendliness, high selectivity, and high efficiency. However, the performance of electrochemical lithium extraction is closely dependent on the electrode material and needs to be compatible under plateau environments with high-altitude and low-temperature. Herein, an in situ self-oxidation method is conducted to construct a hybrid conductive network on the surface of LiFePO4 (LFP-HN). The introduction of a hybrid conductive network enhanced the interfacial electron/lithium-ion transfer. In addition, structural stability is strengthened through suppressing the intercalation of impurity cations. Consequently, the LFP-HN delivered extremely high lithium extraction capacity (27.42 mg g-1), low energy consumption (4.91 Wh mol-1), and superior purity (91.05%) in Baqiancuo real brine (4788 m, -10 °C). What's more, LFP-HN-based large-scale prototypes are constructed and operated at Baqiancuo, which is calculated to extract 25 kg Lithium Carbonate Equivalent per cycle (4.55 h, 100 pairs of plates). Based on the excellent performance, the modification strategy developed in this work can be a promising solution for industrial lithium extraction under high-altitude environment.

Eliminating the effect of pH: Dual-matrix modulation adsorbent enables efficient lithium extraction from concentrated seawater

Lithium ion sieve adsorbents frequently extract liquid lithium resources due to their adsorption effect and cost advantages. However, the adsorption effect is significantly influenced by the ambient pH. The pH effects on the adsorption process can be categorized into two main areas: the competition adsorption of impurity ions and the difference in surface zeta potential. A dual-matrix modulation adsorbent was prepared, comprising a carrier matrix modified with zwitterionic quaternary ammonium bases and an adsorption matrix modified with carboxylation. The zwitterionic quaternary ammonium base groups were employed to mitigate the competitive adsorption of impurity ions by acid-base neutralization. Furthermore, the negative charge of carboxyl groups was employed to diminish the discrepancy in surface zeta potential. The adsorption effect of the ion sieve adsorbent under natural conditions appeared to be significantly enhanced by the dual-matrix modulation, with the saturated adsorption capacity (28 mg/g) and adsorption selectivity (α(Li+/Mg2+)=24.23) being 6.3 and 7.8 times higher than that of the manganese-based adsorbent (HMO) under the same conditions, respectively. Moreover, the adsorption effect was found to be consistent with HMO under alkaline conditions. The results demonstrate that by optimizing the adsorption conditions of the adsorbent, the detrimental impact of pH on the adsorption process of lithium ion sieves can be eliminated.

Enhanced Lithium Extraction from Brines: Prelithiation Effect of FePO4 with Size and Morphology Control

Extracting lithium resources from seawater and brine can promote the development of the new energy materials industry. The electrochemical method is green and efficient. Iron phosphate (FePO4) crystal, with its 1D ion channel, holds significant potential as a primary lithium extraction electrode material. Li+ encounters a substantial concentration disadvantage in brines, and the co-intercalation of Na+ diminishes Li+ selectivity. To address this issue, this work enhances the energy barrier for Na+ insertion through prelithiation strategies applied to the 1D channels of FePO4 crystal, thereby improving Li+ selectivity, and further investigating the prelithiation effect with particle size and morphology control. The results indicate that the Li(4C-40%)FePO4// Activated carbon(AC) system enhances selectivity of lithium. The Li(4C-40%)FePO4 with size diameter of 2500 nm demonstrates an energy consumption of 0.79 Wh mol-1 and a purity of 97.94% for lithium extraction at a unit lithium extraction of 5.93 mmol g-1 in simulated brine. Li(4C-40%)FePO4-nanoplates demonstrate the most optimal lithium extraction performance among the three morphologies due to their lamellar structure's short ion diffusion path in the [010] channel, favoring Li+ diffusion. The diffusion energy barriers of Li+ and Na+ are calculated using Density Functional Theory (DFT) before and after prelithiation, showing good agreement with experimental results.

Predicting the performance of lithium adsorption and recovery from unconventional water sources with machine learning

Selective lithium (Li) recovery from unconventional water sources (UWS) (e.g., shale gas waters, geothermal brines, and rejected seawater desalination brines) using inorganic lithium-ion sieve (LIS) materials can address Li supply shortages and distribution issues. However, the development of high-performance LIS materials and the optimization of recovery-related operating parameters are hampered by the variety of production methods, intricate procedures, and experimental expenses. Machine learning (ML) techniques offer potential solutions for enhancing LIS material development. We collected literature data on Li adsorption, categorizing 16 parameters into adsorbent parameters, operating parameters, and solution components. Three tree-based algorithms-Random Forest (RF), Gradient Boosting Decision Trees (GBDT), and Extreme Gradient Boosting (XGBoost)-were used to evaluate the impact of these parameters on lithium adsorption. The grouped random splitting method limited data leakage and mitigated overfitting. XGBoost demonstrated the best performance, with an R² of 0.98 and a root-mean-squared error (RMSE) of 1.72. The SHAP values highlighted that operating parameters were the most influential, followed by adsorbent parameters and coexisting ion concentrations. Therefore, focusing on optimizing operating parameters or making targeted improvements on LIS based on operating conditions will enhance LIS performances in UWS. These insights are crucial for optimizing Li adsorption processes and designing effective inorganic LIS materials.

A Bioinspired Membrane with Ultrahigh Li+/Na+ and Li+/K+ Separations Enables Direct Lithium Extraction from Brine

Membranes with precise Li+/Na+ and Li+/K+ separations are imperative for lithium extraction from brine to address the lithium supply shortage. However, achieving this goal remains a daunting challenge due to the similar valence, chemical properties, and subtle atomic-scale distinctions among these monovalent cations. Herein, inspired by the strict size-sieving effect of biological ion channels, a membrane is presented based on nonporous crystalline materials featuring structurally rigid, dimensionally confined, and long-range ordered ion channels that exclusively permeate naked Li+ but block Na+ and K+. This naked-Li+-sieving behavior not only enables unprecedented Li+/Na+ and Li+/K+ selectivities up to 2707.4 and 5109.8, respectively, even surpassing the state-of-the-art membranes by at least two orders of magnitude, but also demonstrates impressive Li+/Mg2+ and Li+/Ca2+ separation capabilities. Moreover, this bioinspired membrane has to be utilized for creating a one-step lithium extraction strategy from natural brines rich in Na+, K+, and Mg2+ without utilizing chemicals or creating solid waste, and it simultaneously produces hydrogen. This research has proposed a new type of ion-sieving membrane and also provides an envisioning of the design paradigm and development of advanced membranes, ion separation, and lithium extraction.

Identifying critical features of iron phosphate particle for lithium preference

One-dimensional (1D) olivine iron phosphate (FePO4) is widely proposed for electrochemical lithium (Li) extraction from dilute water sources, however, significant variations in Li selectivity were observed for particles with different physical attributes. Understanding how particle features influence Li and sodium (Na) co-intercalation is crucial for system design and enhancing Li selectivity. Here, we investigate a series of FePO4 particles with various features and revealed the importance of harnessing kinetic and chemo-mechanical barrier difference between lithiation and sodiation to promote selectivity. The thermodynamic preference of FePO4 provides baseline of selectivity while the particle features are critical to induce different kinetic pathways and barriers, resulting in different Li to Na selectivity from 6.2 × 102 to 2.3 × 104. Importantly, we categorize the FePO4 particles into two groups based on their distinctly paired phase evolutions upon lithiation and sodiation, and generate quantitative correlation maps among Li preference, morphological features, and electrochemical properties. By selecting FePO4 particles with specific features, we demonstrate fast (636 mA/g) Li extraction from a high Li source (1: 100 Li to Na) with (96.6 ± 0.2)% purity, and high selectivity (2.3 × 104) from a low Li source (1: 1000 Li to Na) with (95.8 ± 0.3)% purity in a single step.

Microenvironment-Modulating Adsorption Enables Highly Efficient Lithium Extraction under Natural pH Conditions

Ion-sieve adsorbents are effective materials in practical applications for extracting liquid lithium. However, it is greatly suppressed in adsorption capacity and selectivity (Li/Mg) under natural near-neutral conditions of seawater or salt lakes, due to the interference of in situ released H+ and Mg2+ impurity. This paper proposes an adsorbent with a microenvironment-modulating function as a solution. The introduction of quaternary ammonium groups into the carrier accelerates the migration of H+, while preventing the diffusion of Mg2+ by electrostatic repulsion. Besides, it can also prestore OH-, effectively consuming the generated hydrogen ions in situ. Based on the rational design, the alkali consumption of the microenvironment-modulating strategy is dramatically reduced to 1/144 of the traditional alkali-adding method. Additionally, adsorption performance is significantly promoted under natural pH conditions, with a maximum 33 times higher separation factor (selectivity) and 4 times higher adsorption capacity than commercial ion-sieve adsorbents. This development indicates the feasibility of using microenvironment modulation for effective lithium extraction and inspires the development of next-generation high-performance adsorbents.

Understanding the Electrochemical Extraction of Lithium from Ultradilute Solutions

The electrochemical extraction of lithium (Li) from aqueous sources using electrochemical means is a promising direct Li extraction technology. However, to this date, most electrochemical Li extraction studies are confined to Li-rich brine, neglecting the practical and existing Li-lean resources, with their overall extraction behaviors currently not fully understood. More still, the effect of elevated sodium (Na) concentrations typically found in most Li-lean water sources on Li extraction is unclear. Hence, in this work, we first understand the electrochemical Li extraction behaviors from ultradilute solutions using spinel lithium manganese oxide as the model electrode. We discovered that Li extraction depends highly on the Li concentration and cell operation current density. Then, we switched our focus on low Li to Na ratio solutions, revealing that Na can dominate the electrostatic screening layer, reducing Li ion concentration. Based on these understandings, we rationally employed pulsed electrochemical operation to restructure the electrode surface and distribute the surface-adsorbed species, which efficiently achieves a high Li selectivity even in extremely low initial Li/Na concentrations of up to 1:20,000.

Direct Lithium Extraction Using Intercalation Materials

Worldwide lithium demand has surged in recent years due to increased production of Li-ion batteries for electric vehicles and stationary storage. Li supply and production will need to increase such that the transition towards increased electrification in the energy sector does not become cost prohibitive. Many countries have taken policy steps such as listing Li as a critical mineral. Current commercial Li mining is mostly from dedicated mine sources, including ores, clays, and brines. The conventional ways to extract Li+ from those resources are through chemical processing and includes steps of calcination, leaching, precipitation, and purification. The environmental and economic sustainability of conventional Li processing has recently received increased scrutiny. Routes such as direct Li+ extraction may provide advantages relative to conventional Li+ extraction technologies, and one possible route to direct Li+ extraction includes leveraging intercalation materials. Intercalation material processing has recently demonstrated high selectivity towards Li+ as opposed to other cations. Reviews and reports of direct Li+ extraction with intercalation materials are limited, even as this technology has started to show promise in smaller-scale demonstrations. This paper will review selective Li+ extraction via intercalation materials, including both electrochemical and chemical methods to drive Li+ in and out, and efforts to characterize the Li+ insertion/deinsertion processes.

Annealed SiO2 Protective Layer on LiMn2O4 for Enhanced Li-Ion Extraction from Brine

In this study, we present a novel approach for selective Li-ion extraction from brine using an LiMn2O4 ion sieve coated with a dense silica layer, denoted as LMO@SiO2. The SiO2 layer is controllably coated onto the LMO surface, forming passivation layers and ion permeation filters. This design effectively minimizes the acidic corrosion of the LMO and enhances the Li+ adsorption capacity. Additionally, the SiO2 layer undergoes calcination at various temperatures (ranging from 300 to 700 °C) to achieve different compactness levels of the coating layer, providing further protection to the LMO crystal structures. As a result of these improvements, the optimized LMO@SiO2 adsorbent demonstrates an exceptional Li+ adsorption capacity of 18.5 mg/g for brine, and even after seven adsorption-elution cycles, it maintains a capacity of 15.3 mg/g. This outstanding performance makes our material a promising candidate for efficient Li+ extraction from brine or other low-concentration Li+ solutions in future applications.

Fluorine-Rich Supramolecular Nano-Container Crosslinked Hydrogel for Lithium Extraction with Super-High Capacity and Extreme Selectivity

Extraction and recovery of lithium from reserves play a critical role in the sustainable development of energy due to the explosive growth of the lithium-battery market. However, the low efficiency of extraction and recovery seriously threatens the sustainability of lithium supply. In this contribution, we fabricate a novel mechanically robust fluorine-rich hydrogel, showing highly efficient Li+ extraction from Li-containing solutions. The hydrogel was facilely fabricated by simple one-pot polymerization of supramolecular nanosheets of fluorinated monomers, acrylic acid and a small amount of chemical crosslinkers. The hydrogel exhibits a remarkable lithium adsorption capacity (Qm Li+ =122.3 mg g-1 ) and can be reused. Moreover, it can exclusively extract lithium ions from multiple co-existing metal ions. Notably, the separation of Li+ /Na+ in actual wastewater is achieved with a surprising separation factor of 153.72. The detailed characterizations as well as calculation showed that the specific coordination of Li-F plays a central role for both of the striking recovery capability and selectivity for Li+ . Furthermore, an artificial device was constructed, displaying high efficiency of extracting lithium in various complex actual lithium-containing wastewater. This work provides a new and promising avenue for the efficient extraction and recovery of lithium resource from complex lithium-containing solutions.

Engineering Multi-field-coupled Synergistic Ion Transport System Based on the Heterogeneous Nanofluidic Membrane for High-Efficient Lithium Extraction

The global carbon neutrality strategy brings a wave of rechargeable lithium-ion batteries technique development and induces an ever-growing consumption and demand for lithium (Li). Among all the Li exploitation, extracting Li from spent LIBs would be a strategic and perspective approach, especially with the low energy consumption and eco-friendly membrane separation method. However, current membrane separation systems mainly focus on monotonous membrane design and structure optimization, and rarely further consider the coordination of inherent structure and applied external field, resulting in limited ion transport. Here, we propose a heterogeneous nanofluidic membrane as a platform for coupling multi-external fields (i.e., light-induced heat, electrical, and concentration gradient fields) to construct the multi-field-coupled synergistic ion transport system (MSITS) for Li-ion extraction from spent LIBs. The Li flux of the MSITS reaches 367.4 mmol m-2 h-1, even higher than the sum flux of those applied individual fields, reflecting synergistic enhancement for ion transport of the multi-field-coupled effect. Benefiting from the adaptation of membrane structure and multi-external fields, the proposed system exhibits ultrahigh selectivity with a Li+/Co2+ factor of 216,412, outperforming previous reports. MSITS based on nanofluidic membrane proves to be a promising ion transport strategy, as it could accelerate ion transmembrane transport and alleviate the ion concentration polarization effect. This work demonstrated a collaborative system equipped with an optimized membrane for high-efficient Li extraction, providing an expanded strategy to investigate the other membrane-based applications of their common similarities in core concepts.