Lithium Melts Research Articles

New developments of hydrogen impurity online-monitoring in liquid lithium of IFMIF-DONES

On the way to future nuclear fusion power plants, the International Fusion Materials Irradiation Facility (IFMIF) – DEMO Oriented Neutron Source (DONES), is an important key element between ITER and DEMO to study before the influence of DEMO-neutron irradiation on foreseen fusion materials. The core of DONES, currently under construction near Granada, Spain, is based on a circuit containing liquid lithium at elevated temperatures acting as a functional material for the (d,n)-Li reaction in a materials test cell. In addition to this actual function of DONES, there are important aspects of maintenance in which hydrogen isotopes are generated under operating conditions and dissolved in this aggressive and very reactive alkali metal. This implies strong unfavourable effects on the applied structural materials, e.g. hydrogen embrittlement and others.To counteract these unfavourable effects, endangering the safe operation, an Impurity Control System (ICS) is an integral part of the DONES instrumentation. As part of the tasks of the European Neutron Source (ENS) to develop redundant systems for monitoring impurities, a special sub-task was defined for the development of an electrochemical H-sensor for concentrations in liquid lithium, ECHSLL. It is determined by detecting the electrical potentials of the lithium melts compared to a standard Li-based chemical reference system. This allows an inherent material property to be directly correlated (i.e. through appropriate electrochemical instrumentation) with chemical concentration values. This article presents important advancements in the applied ECHSLL technique, such as improving laboratory measurements from stagnant conditions to dynamic and realistic flow conditions of the liquid lithium material, as well as appropriate approaches to overcome the challenges in distinguishing the hydrogen isotopes by ECHSLL system (protium and deuterium among given laboratory conditions).

Evaluation of lithium as a tritium storage medium for betavoltaics

Lithium foils were demonstrated to absorb surrogate protium for tritium-powered betavoltaics. 20 μm thick lithium foils were hole-punched from a ribbon of electrodeposited lithium on copper foil. The lithium foils were loaded with hydrogen in a custom Sievert apparatus where the pressure drop showed full hydriding at a hydrogen pressure of 2 bar and at all loading temperatures above the lithium melting point at 190, 200, 225, 250, and 300. Lithium hydride formation was confirmed with Raman spectroscopy after hydrogen loading. The kinetics of experimental hydride formation was compared to the diffusion-limited Mintz–Bloch model. While the Mintz–Bloch model showed good fit with the experimental loadings, the model overpredicted the loading kinetics starting at 250 °C and at higher temperatures. The overprediction was either caused by lithium hydride outgassing due to some reduction with some residual lithium hydroxide created from brief air exposure when sealing the lithium in the reactor or a transition from diffusion-limited hydride growth to surface or metal–hydride interface-limited hydride growth.

Pre-Lithiation of Silicon-Based Anode Materials: Concepts and Realization

The capacity in lithium ion battery (LIB) relies on active lithium, i.e., lithium-ions and electrons, which separately shuttle between the electrodes during charge and discharge. Given state-of-the art active materials for anodes, loss of active lithium and capacity remains a major challenge during LIB operation, in particular in the first charge/discharge cycle due to electrolyte decomposition and formation of solid electrolyte interphase (SEI).Pre-lithiation, i.e., artificial increase in active lithium amount into the battery is a promising strategy to counteract active lithium loss. Electrochemical(1) and chemical(2,3) methods of pre-lithiation can be distinguished. While electrochemical methods are based on the use of an external power source, the driving force of the chemical reaction is a negative change in the Gibb´s free energy which in the case of pre-lithiation is provided by the use of highly reactive chemical compounds (e.g. lithium-organic complex solutions or lithium metal). The use of lithium metal allows for a wide range of technological processes, including lamination of lithium foil, gas-phase deposition, application of lithium melts or suspensions containing lithium powder. In this contribution, various concepts of pre-lithiation will be discussed from experimental and up-scaling point of view on the example of Si-based anodes.(1) Haneke, L.; Pfeiffer, F.; Bärmann, P.; Wrogemann, J.; Peschel, C.; Neumann, J.; Kux, F.; Nowak, S.; Winter, M.; Placke, T., Insights into Electrolytic Pre‐Lithiation: A Thorough Analysis Using Silicon Thin Film Anodes. Small 2022, 2206092.(2) Adhitama, E.; Bela, M. M.; Demelash, F.; Stan, M. C.; Winter, M.; Gomez‐Martin, A.; Placke, T., On the Practical Applicability of the Li Metal‐Based Thermal Evaporation Prelithiation Technique on Si Anodes for Lithium Ion Batteries. Advanced Energy Materials 2023, 13 (3), 2203256.(3) Bärmann, P.; Mohrhardt, M.; Frerichs, J. E.; Helling, M.; Kolesnikov, A.; Klabunde, S.; Nowak, S.; Hansen, M. R.; Winter, M.; Placke, T., Mechanistic Insights into the Pre‐Lithiation of Silicon/Graphite Negative Electrodes in “Dry State” and After Electrolyte Addition Using Passivated Lithium Metal Powder. Advanced Energy Materials 2021, 11 (25), 2100925.

Tailored Pre-Lithiation of Carbon Anodes Using Melt Deposited Thin Lithium

The user demands for Lithium ion batteries in mobile applications and electric vehicles request steady improvement in terms of capacity and cycle life. State-of-the-art lithium ion batteries irreversibly loose about 10 % of the capacity during the first cycles due to SEI formation. Therefore, 10 % of the cathode material is not used during the rest of the cells life which results in a waste of cathode material and leads to a lowered range of battery electric vehicles. Therefore, these losses must be compensated to ensure efficient resource utilization and to further increase the capacity of the lithium ion battery.We have developed a method to compensate these capacity losses by pre-lithiation: A fast and simple approach of electrolyte-free direct contact pre-lithiation leads to targeted degrees of pre-lithiation in a range of 7-50 % for state-of-the-art graphite electrodes. The parameters pressure (0-40 MPa), temperature (20-150°C) and time (0-60 min) are used to transfer lithium from a temporary substrate to the graphite anode. This process uses 1-5 µm thin lithium films made by the Fraunhofer IWS lithium melt deposition process as a lithium source.[1] The degree of pre-lithiation can be controlled by the lithium loading of the temporary substrate. NCM full cells built with pre-lithiated graphite electrodes where electrochemically evaluated in comparison to unlithiated electrodes. They show 6.5 % capacity increase after the first cycles using the additional lithium to form the SEI during the first cycles. The parameter influence of the pre-lithiation process on the initial coulomb efficiency of cells with pre-lithiated graphite electrodes is examined in half cells showing an ICE of 99.91 % for the best parameters.This method of electrolyte-free direct contact pre-lithiation shows an efficient way to further increase the capacity of state-of-the-art LIBs with graphite electrodes by increasing the cathode material utilization. It can potentially be scaled up to a roll-to-roll process using a heated calender nip. The temporary substrates with tailored lithium loading can be processed by lithium melt deposition in an efficient way with high lithium yield and high precision.[1] K. Schönherr, B. Schumm, F. Hippauf, R. Lissy, H. Althues, C. Leyens, S. Kaskel, Chemical Engineering Journal Advances 2022, 9, 100218. Figure 1

Tailored Pre-Lithiation Using Melt-Deposited Lithium Thin Films

The user demands lithium-ion batteries in mobile applications, and electric vehicles request steady improvement in terms of capacity and cycle life. This study shows one way to compensate for capacity losses due to SEI formation during the first cycles. A fast and simple approach of electrolyte-free direct-contact pre-lithiation leads to targeted degrees of pre-lithiation for graphite electrodes. It uses tailor-made lithium thin films with 1–5 µm lithium films produced by lithium melt deposition as a lithium source. These pre-lithiated graphite electrodes show 6.5% capacity increase after the first cycles in NCM full cells. In this study, the influence of the pre-lithiation parameters—applied pressure, temperature and pressing time—on the pre-lithiation process is examined.

Li16Sr6Ge6N, Li16Sr6Ge6.5 and related lithium alkaline‐earth metal tetrelides: Alternative filling of voids by nitride or tetrelide ions

AbstractLarge black single crystals with a metallic luster of Li16Sr6Ge6N and several other representatives of the series Li16Ae6Tt6N and Li16Ae6Tt6.5 (Ae=Ca, Sr; Tt=Si, Ge, Sn, Pb) were grown from mixtures of the respective elements with addition of binary alkaline‐earth metal nitrides or lithium nitride in the case of the nitrides. For the synthesis a modified high‐temperature centrifugation‐aided filtration (HTCAF) technique using reactive lithium melts was employed. These metallic phases crystallize in an ordered defect‐variant of the Sc11Ir4 type with selective occupation of the smaller octahedral voids in the origin (000) with N and the larger rhombic dodecahedral voids in (00 ) with Tt. Charge balance assuming the presence of exclusively closed shell ions for all examples accounts for an electronic excess. Diamagnetism despite metallic properties is consistent with results from electronic structure calculations.

Electrochemical hydrogen detection in DONES loop materials

• Design of an electrochemical sensor adequate to RAMI conditions of IFMIF-DONES. • Determination of hydrogen in liquid lithium. • Online electrochemical muliplex monitoring. • Modular design for different extended approaches (impurities, electrochemical procedures, sizes). The radiation-induced degradation of materials in fusion systems is planned to be investigated in IFMIF-DONES ( International Fusion Materials Irradiation Facility - DEMO Oriented NEutron Source ), where fast neutrons are produced by a reaction of deuteron-beams with a liquid lithium target. A by-product as critical impurity is hydrogen, which might affect the reliable and safe operation of the IFMIF-DONES loops. Therefore, an important issue is the measurement and control of the hydrogen impurity concentrations in liquid lithium. Initially, a practically applicable direct measurement of hydrogen concentrations in lithium facilities did not exist. However, one promising approach to manage this issue is based on the electrochemistry of the DONES materials The developed Electro-Chemical Hydrogen Sensor for Liquid Lithium (ECHSLL) allows the measurement of the electromotive Force (EMF) between a reference materials system and the loop lithium melt, and thus the monitoring of the hydrogen impurity concentrations. This article will show backgrounds of non-metallic impurities in liquid metal materials and the specific material stabilities within DONES. Liquid lithium is a very reactive material. Therefore critical issuesareviable materials compatibilities, the interactions with hydrogen and the transport behaviour of H-ions in electrolytes at the applied temperatures. Further issues are also the syntheses of the electrochemical materials, as hydrogen conducting electrolytes, reference electrode systems and the different procedures (heat treatments and conditioning steps). The tests showed the functionality of the developed H-sensor. Beyond that, the used material combinations exhibited reliable behaviour in melts under harsh conditions. Hence, the most critical aspect (stability of the sensor materials in the Li-melt) has been resolved by using niobium sensor heads. The observed experimental EMF potentials are in good accordance compared with calculated models, also in long-time experiments.

An oxygen vacancy-rich ZnO layer on garnet electrolyte enables dendrite-free solid state lithium metal batteries

An oxygen vacancy-rich ZnO (Ov-ZnO) layer is deposited on garnet electrolyte, which not only remove the surfafical Li 2 CO 3 , but also in-situ forms an Li + -conductive Li x ZnO interphase. Li symmetric cells with this Ov-ZnO-coated garnet exhibit an ultralow cell resistance and a record-high critical current density of 1.4 mA cm −2 ever reported without lithium dendrite at room temperature. • A layer of ZnO with oxygen vacancies is coated on the surface of garnet electrolyte. • A low interfacial resistance of 55 Ω cm 2 is achieved without melting lithium. • The reaction mechanism of the interphase on garnet is investigated in detail. • The strategy can be extended to other metal oxides with oxygen vacancies. The huge interfacial resistance caused by Li 2 CO 3 on garnet (LLZO) electrolyte and the lithium-dendrite growth through garnet greatly hinder the development of solid-state batteries (SSBs). Here, both the problems are simultaneously addressed through a general strategy of engineering garnet pellet with a layer of ZnO with oxygen vacancies (O V -ZnO). The O V -ZnO not only protects LLZO from being exposed to wet air, but also reacts spontaneously with lithium-metal to in-situ form an ionic conducting Li x ZnO interphase. The as-formed interphase improves the Li/LLZO contact, reduces the huge interface resistance caused by Li 2 CO 3 , suppresses the lithium-dendrite growth, and promotes the lithium transport between LLZO and Li-metal. As a result, an Li/Li symmetric cell with O V -ZnO coated LLZO pellet shows a low area specific resistance of 55 Ω cm 2 , a stable plating/stripping process for 200 h at a current density of 0.1 mA cm −2 , and a record-high critical current density of 1.4 mA cm −2 ever reported at room temperature. Moreover, this approach of coating metal oxide with oxygen vacancies on garnet electrolytes has been extended to other metal oxides, such as copper oxide (O V -CuO), titanium dioxide (O V -TiO 2 ) and indium oxide (O V -In 2 O 3 ).

Liquid lithium metal processing into ultrathin metal anodes for solid state batteries

Lithium metal anodes are among the most promising candidates for further increasing the energy density of lithium ion batteries and all-solid-state batteries. A reduction of the anode thickness by using ultrathin lithium metal films is a crucial requirement to achieve a significant overall reduction of thickness on cell level. However, besides anode stabilization, realizing scalable technologies for an efficient production of thin lithium metal anodes is one of the most challenging obstacles for the success of various next-generation battery chemistries. In this publication we introduce a disruptive lithium melt deposition process for thin lithium metal coating on thin copper current collector foils. The wetting of molten lithium on the substrate can only be achieved through a lithiophilic interlayer. As a result fast and homogeneous lithium spreading on the substrate is enabled allowing roll-to-roll coating with liquid-deposition technologies as demonstrated in this contribution with a speed of several meters per minute and reaching 100 mm width. With this new process the anode thickness can be tuned in a wide range (1–30 µm). Evaluation in a prototype solid battery system shows high electrochemical lithium utilization and no detrimental effects compared to commercially available lithium reference foils.

Development of an on-line sensor for hydrogen isotopes monitoring in flowing lithium at DONES

• One challenging aspect on the development of DONES is the purity of the lithium. • An online sensor based on the PAV technique is proposed for H-isotopes monitoring. • The design consists of a capillary tube made of a Pd/Ag membrane spirally rolled. • An experimental facility is designed to demonstrate the feasibility of the monitor. • Theoretical simulations have been carried out using the EcosimPro platform. DONES (Demo Oriented Neutron Source) consists of an irradiation facility based in the nuclear stripping reactions that occur when one energetic deuteron beam impinges on a liquid lithium target flowing along an open channel. Since impurities enhance the erosion/corrosion effect, one of the challenging aspects on the development of the neutron source is the purity of the lithium. One group of impurities to be controlled are hydrogen isotopes in which the control of tritium as part of the produced impurities is mandatory due to its radiological risk. R&D activities are being performed for the development of different kinds of hydrogen sensors since there is no availability of commercial online monitors that could work under the lithium environment. As an extrapolation from other fusion applications, an online sensor based on the permeation against vacuum technique is proposed in this paper. The sensor design consists of a capillary tube made of a Pd/Ag membrane whose inner volume is subjected to vacuum promoting the H-isotopes permeation from the liquid. The vacuum line is connected to a mass spectrometer for the isotope detection. In addition, an experimental facility has been designed to experimentally demonstrate the feasibility of this monitor. It is made of a two-vessels system for lithium melting and H-isotopes detection. Furthermore, theoretical simulations have been carried out using the EcosimPro platform. Results show the expected behaviour of the sensor working under static conditions in the facility.

Lithiophilic surface treatment of metal- and metallic compound-based frameworks by gas nitriding for lithium metal batteries

Metal-based frameworks are developed for lithium metal batteries due to their effective suppression of the lithium dendritic growth. However, the use of appealing metals such as copper (Cu), the best current collector in batteries, are still limited owing to lithiophobicity. Here, we report a facile lithiophilic surface treatment of metal- and metallic compound-based scaffolds via gas nitriding. Due to nitride anion (N3−) from ammonia (NH3) gas that can bond to almost all elements and form lithiophilic binary nitrides, the gas nitriding on a pristine Cu foam and a Cu(OH)2 nanorods grown Cu foam results in a formation of lithiophilic Cu3N film on the surface without a noticeable structural change. After lithium melt infusion, symmetric cells assembled with two types of lithium hosts show stable structural stability and a smooth Li plating/stripping behavior without a dendritic growth of lithium. Particularly, a full cell test demonstrates that lithiated Cu3N nanorods grown Cu foam exhibits enhanced electrochemical performances including capacity, rate capability, and cycle performance compared to a bare Li foil. Our findings demonstrate the gas nitriding is a powerful tool for lithiophilic surface treatment of metals and metallic compounds with various dimensions and sizes from micro to nanoscale.

Dynamics of Liquid Lithium Atoms: Time Scales and Dynamic Correlation Functions

Based on the configuration data on molecular dynamics simulation of the lithium melt near the melting point, the memory functions of the relaxation process of the density fluctuations are calculated. It is established that for the range of wave numbers corresponding to microscopic spatial scales, the memory functions of the first four orders are characterized by oscillating behavior. This feature indicates that the model memory functions in the case of phenomenological description of the dynamics of the density fluctuations can not have the form of monotonically decreasing functions. The frequency characteristics of the dynamic structure factor for a wide range of wave numbers are calculated. The convergence of the relaxation parameters Δ4(k) and Δ5(k) for the range of wave numbers from the hydrodynamic regime (k → 0) to the values of k is higher than the boundary of the first pseudo-Brillouin zone (for k ≈ 0.87km) are detected. The characteristic time scales of the process of structural relaxation of the density fluctuations are determined.

Fabrication and characterization of Li-coated nickel mesh for anode of lithium-metal batteries

Lithium metal is one of the most promising anode materials for lithium rechargeable batteries owing to its high capacity. However, its practical use is not yet realized owing to safety issues. In this study, we fabricated a Li-coated Ni-mesh and tested it in a Li/Li symmetric and Li/Cu cell. The Ni-mesh is oxidized to make it lithiophilic prior to coating with lithium in a lithium melt. The Li-coated Ni-mesh electrode exhibits a significantly better cycling stability and lower interfacial resistance than those of a pristine lithium-foil electrode. We believe that the good cycling stability is attributed to the suppressed dendritic growth of lithium and fast electron transport along the Ni-mesh. The suppressed dendritic growth of lithium is closely related with the three-dimensional structure of the Li-coated Ni-mesh electrode which i) lower the current density owing to its large surface area, ii) and prevent electron localization at lithium dendrites and iii) the Li2O phase on Ni-mesh which raises transference number of Li+ (tLi+).

Visualization of the secondary phase in LiFePO4 ingots with advanced mapping techniques

AbstractLiFePO4 has been widely used as a cathode material in lithium ion batteries. However, some impurity phases existing in LiFePO4 have a significant influence on its electrochemical performance. Therefore, detection of the impurity phases is necessary for the manufacturer in order to improve the quality of LiFePO4. In particular, visualization of the impurity and secondary phase distributions immersed in the bulk LiFePO4 crystal can help to understand the origin of the impurity and secondary phases, providing clear guidance towards the synthesis of high purity LiFePO4. The results show that with the combination of Raman and EDS, we are capable of identifying the low melting lithium phosphate phase in LFP ingot. Through micro XRF mapping, more detailed information about the LFP materials after carbon coating are observed. The secondary phases are easily defined due to the high sensitivity of this technology.

Polarization and adsorption effects on the wettability of a gold electrode by lithium, sodium, potassium, and cesium chloride melts

To establish the patterns of the wettability of solid surfaces by ionic melts, the wetting energy of a gold electrode by lithium, sodium, potassium, and cesium chloride melts was studied as a function of the electrical potential applied to the electrode. It was established that when the potential was shifted in the positive direction relative to the zero-charge potential of gold in the corresponding melt, the shape of the curve that defined the dependence of the wetting energy on the electrical potential varied according to the salt composition: for lithium and sodium chlorides, the wetting energy increased monotonically, while in potassium and cesium chloride melts there was a maxima. This phenomenon was explained from the standpoint of the mutual polarization of gold and chlorine ions in the place of their direct contact. At a certain electric field strength in the double electric layer and at a certain binding energy of the melt particles, the resultant mutual ion polarization led to the formation of ordered layers of ionic associations (presumably AuCln(n − 1)-) on the anode surface, which shielded the electrode charge.

Lithium alkaline earth tetrelides of the type Li2 AeTt (Ae=Ca, Ba, Tt=Si, Ge, Sn, Pb): synthesis, crystal structures and physical properties

Abstract Single crystals of the compounds Li2 AeTt (Ae=Ca, Ba, Tt=Si, Ge, Sn, Pb) were grown in reactive lithium melts in sealed tantalum ampoules from an equimolar ratio of the alkaline earth metal and the respective group 4 element. All compounds, with the exception of Li2CaSn and Li2CaPb, are isotypic and crystallize in an orthorhombic unit cell (space group Pmmn, no. 59). The crystal structure can be characterized as superimposed corrugated networks of Li2 Tt connected by calcium or barium atoms within the third dimension. Li2CaSn and Li2CaPb crystallize in the cubic space group Fm3̅m (no. 225) in a Heusler-type (MnCu2Al) structure. According to magnetic susceptibility and electric resistivity measurements, the compounds Li2BaGe, Li2BaSn, and Li2BaPb represent diamagnetic activated semiconductors.

A comparative property investigation of lithium phosphate glass melted in microwave and conventional heating

The present study addresses the application of microwave (MW) energy for melting lithium phosphate glass. A comparative analysis of the properties is presented with glasses melted in conventional resistance heating adopting standard methods of characterization. The density of the glass was found less in MW heating. The glass transition temperature was recorded as 3–10\({^{\circ }}\hbox {C}\) lower in MW prepared glass than in conventional glass. Micro-hardness is found to be improved in case of MW heating. Maximum forward power was recorded less than 2 kW with an average power \(\sim \)1 kW during melting of 40 g glass in MW furnace. MW forward and reflected power measured during melting in the MW cavity was elaborated. Total melting time was within 2 h 30 min in MW heating, whereas it was 6–7 h in resistive heating. Total power consumed was \(\sim \)5 kWh in MW heating and \(\sim \)14 kWh in resistance heating.

Experimental and theoretical investigation of the surface properties of lead–lithium melts

Experimental data on the density and surface tension of lead–lithium melts, obtained using the large drop method, are presented as functions of temperature. These data are used in a computational experiment to construct both two- and three-dimensional drop profiles. It is shown that this approach allows us to estimate the effect errors in physical parameters have in determining a system’s configuration.

Role of quantum ion dynamics in the melting of lithium

The role of quantum ion dynamics in the low melting temperatures of Li is investigated from first principles theory. Free energies of solid and liquid phases are obtained at the classical and quantum ion levels. The results are used to determine the Li melting curve in the 40--60 and 110--150 GPa pressure ranges and are in excellent agreement with experimental data around 50 GPa. They predict the resumption of a positive melting slope at higher pressure. Quantum corrections to individual energy terms are far more significant than their net effect on the melting temperatures near 50 GPa, even though lithium behaves as a quantum solid at this pressure. The scales of these corrections increase with compression. A case is made for the possibility for anomalous melting at much higher pressures, where quantum ion dynamics are expected to play a prominent role.

Lithium Ion Conduction in Single Lithium Perfluorosulfonylamides

A liquid electrolyte of lithium ion battery (LIB) is usually composed of a lithium salt and a solvent, such as an organic solvent or a room temperature ionic liquid (RTIL), which is usually necessary to dissolve the lithium salts. Therefore, the electrolytes must contain characteristics of both of the lithium salt and solvent. For example, an organic electrolyte usually has high vapor pressure and flammability derived by the organic solvent. The solvent or the other additive materials are absolutely necessary for practical use but also complicate properties of the electrolytes. We reported that a lithium (fluorosulfonyl)(trifluoromethylsulfonyl)amide (Li[(FSO2)(CF3SO2)N]), which is denoted as Li[fTfN], formed a molten salt above 100 ºC.[1] The Li[fTfN] melt is extremely simple construction as the electrolytes for the lithium secondary battery, only Li+ and fTfN–. Therefore, it is free from the effect of the solvents and its concentration of Li+ is extremely high (about 7.0 mol·dm–3) among liquid electrolytes. Charge-discharge in the single Li[fTfN] was successful with conventional electrodes for LIB, such as LiCoO2, LiFePO4[1] and graphite.[2] The Li[fTfN] has many interesting characteristics compared with the conventional electrolytes of LIB, such as much high viscosity and superionic conductivity.[1] In this study, we focused on no concentration gradient in the Li[fTfN] when applying current. In the conventional liquid electrolytes, the concentration gradient of lithium salt is generated in the electrolytes when current is applied in order to maintain electroneutrality in the electrolytes. However, the concentration gradient of lithium salt is not generated in the single Li[fTfN] melt because this melt is a lithium salt itself. In chronoamperometry of the Li[fTfN] using the two-electrode lithium metal symmetrical sell, there is little difference between an initial current, which caused by Li+ and fTfN−, and a steady current, which caused by only Li+.[1] This indicates that the only Li+ migrate by difference of voltages and fTfN– does not diffuse by concentration gradient. Its conduction behavior is similar to a solid electrolyte. Therefore, it is expect that Li+ is not drained near electrode if large current is applied in high rate charge-discharge. To the best of our knowledge, there is a few kind of single lithium salt which melts below melting point of lithium metal (180 ºC), such as the Li[fTfN] and bis(fluorosulfonyl)amide salt (Li[f2N]). These melts have possibility of electrolyte possessing high rate performance due to the no concentration gradient. In this presentation, the conduction behavior of Li+ in these low-melting single lithium melts. Acknowledgement This work was supported by the Advanced Low Carbon Technology Research and Development Program Specially Promoted Research for Innovative Next Generation Batteries (ALCA-SPRING) of Japan Science and Technology Agency (JST). [1] K. Kubota, H. Matsumoto, J. Phys. Chem. C, 117, 18829 (2013). [2] K. Kubota, H. Matsumoto, ECS Trans., 62, 231 (2014).