Due to the ubiquitous presence of lithium‐ion batteries in portable applications, and their implementation in the transportation and large‐scale energy sectors, the future cost and availability of lithium is currently under debate. Lithium demand is expected to grow in the near future, up to 900 ktons per year in 2025. Lithium utilization would depend on a strong increase in production. However, the currently most extended lithium extraction method, the lime‐soda evaporation process, requires a period of time in the range of 1–2 years and depends on weather conditions. The actual global production of lithium by this technology will soon be far exceeded by market demand. Alternative production methods have recently attracted great attention. Among them, electrochemical lithium recovery, based on electrochemical ion‐pumping technology, offers higher capacity production, it does not require the use of chemicals for the regeneration of the materials, reduces the consumption of water and the production of chemical wastes, and allows the production rate to be controlled, attending to the market demand. Here, this technology is analyzed with a special focus on the methodology, materials employed, and reactor designs. The state‐of‐the‐art is reevaluated from a critical perspective and the viability of the different proposed methodologies analyzed.

Reversible mixed-ion intercalation in nonselective host structures has promising applications in desalination, mixed-ion batteries, wastewater treatment, and lithium recovery through electrochemical ion pumping. One class of host compound that possesses many of the requirements needed for such applications (cost effectiveness, fast ion kinetics, and stability in an aqueous medium) includes the Prussian blue derivatives. Herein, the fundamental process of intercalation of multiple cations is studied at the thermodynamic level by means of galvanostatic cycling. Nickel hexacyanoferrate is focused upon because of its stability and low potential for electrochemical process relative to other hexacyanoferrates. Various cations can be intercalated; large cations (K and NH ) are intercalated at higher potentials than those of smaller cations (Na ). When mixtures of cations are present in solution, the potential profile is not qualitatively altered with respect to single-salt solutions, but the potential of (de-)intercalation is shifted; a simple thermodynamic model is introducted that is able to predict the potential and distribution at which intercalation takes place.

Model systems for electrochemical impedance spectroscopy (EIS) studies of solid-state electrolytes based on ceramic lithium ion conductor Li 7 La 3 Zr 2 O 12 (LLZO) and polymer electrolyte P(EO) 20 -LiClO 4 are investigated for the first time. The aim of the present study is to identify and quantify the lithium ion transition resistance of the ceramic/polymer interface. Symmetrical model systems consisting of LLZO pellets with sheets of P(EO) 20 -LiClO 4 are manufactured and investigated in detail. In such symmetric model systems we observed an additional ion-transfer process, which we attributed to the interface processes (i.e. distributed Li + transition across the interface). Based on the EIS measurement data obtained above the polymer electrolyte's melting temperature, at 70 • C the interface resistance of the lithium ion transition is estimated to be ∼9 k cm 2 and the capacitance of the process is in the order of 0.1 μF/cm 2 . According to our investigations, it is possible to predict interface resistivity of lithium ion transport for different polymer/ceramic composite electrolytes for solid state lithium battery applications.

Lithium demand is expected to strongly grow in the near future, as a consequence of the envisaged increase of battery production for stationary energy storage and electromobility. The current technologies are not suited for meeting this demand. With the aim of spreading the available sources of lithium, in this work we investigated the limitations of the "electrochemical ion pumping" in terms of energy losses (overvoltages) and captured lithium for lithium sources with concentrations down to 1 mM. In order to do so, we used a flow-through electrochemical cell and we took into account also the energy consumption for the pumping process. We observed that in presence of large amount of sodium ions there is a detrimental effect on the performances of the system, likely connected to a surface adsorption process, as recently reported in literature. Our study points out which parameters of the materials must be tailored (porosity, surface) for improving the performances of the technique.

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Due to the predicted increase of the lithium demand, its production will soon become outpaced by the market need. The current lithium-extraction techniques, which are based on the soda-lime evaporation process, are not only too slow to meet this increasing demand, but they also produce a large amount of chemical wastes. An alternative electrochemical technique, called "ion pumping", has been recently proposed. In this work, we are exploring the effect of the current density and the mass loading on the performance of a flow-through electrodes cell, which recovers lithium by means of electrochemical ion pumping from a 1 mM LiCl and a 100 mM NaCl solution. We observed that, by increasing the mass loading of the lithium-capturing electrode, a larger amount of lithium could be captured per unit mass. The same result was obtained when the applied current density was decreased. It is striking that, by choosing the right cell parameters, an almost complete capturing of lithium from the source solution has been reached.

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Anodizing of sputtering-deposited magnesium and Mg-0.75at.%Cu and Mg-1.23at.%W alloys has been carried out in a fluoride/glycerol electrolyte. The aims of the study were to investigate the enrichment of alloying elements in the alloy immediately beneath the anodic film and the migration of alloying element species in the film. The specimens were examined by electron microscopy and ion beam analysis. An enrichment of copper is revealed in the Mg-Cu alloy that increases with the anodizing time up to ∼6×10 15 Cu atoms cm −2 . Copper species are then incorporated into the anodic film and migrate outwards. In contrast, no enrichment of tungsten occurs in the Mg-W alloy, and tungsten species are immobile in the film. Anodizing treatments have long been used for the protection of magnesium alloys against corrosion and wear and interest still remains in improving and extending the range of available technologies. [1][2][3][4][5][6] Nevertheless, fundamental knowledge of anodizing of magnesium, 7 for instance relating to the migration rates and transport numbers of film species, is comparatively limited, in part due to the difficulty of forming films of uniform composition and thickness, and also to their reactivity to water. The formation of barrier-type anodic films has been extensively investigated on the valve metals, especially for aluminum, niobium, tantalum, titanium and zirconium.8 These studies have shown that oxide films of uniform thickness are formed under a high electric field that depends upon the film composition and the rate of film growth. [8][9][10] The films on aluminum, tantalum and niobium are usually amorphous, 8 and their formation involves migration of metal ions and oxygen ions, with significant contributions of both types, e.g. the transport numbers of Al 3+ , Nb 5+ and Ta 5+ are ∼0.40, 0.24 and 0.24 respectively. 8 Further, an outer region of the oxide films often contains a low concentration of species derived from the anions of the electrolyte.11 In contrast, the films on zirconium are usually nanocrystalline and form mainly by migration of O 2− ions, 12,13 while films on titanium undergo a transition from amorphous oxide to a mixture of amorphous and crystalline oxide.14 Barrier-type films can also be formed on magnesium, although such films have received much less attention and, consequently, less is known of the details of their composition, structure and growth mechanism. Films formed in aqueous electrolytes are often reported to consist of MgF 2 , MgO and/or Mg(OH) 2 . 5,7,[15][16][17] Barrier-type films can also be formed using non-aqueous electrolytes and the formation of uniform films in such electrolytes provides the opportunity for systematic studies of the anodizing behavior. 18,19 From previous work, anodizing of magnesium alloys can result in the enrichment of alloying elements beneath the anodic film. Such enrichments have been reported for copper, tungsten and zinc beneath oxide/hydroxide films formed on model alloys in an aqueous electrolyte 20,21 and of zinc beneath fluoride-...