Ionic Conductivity Of Solid Electrolytes Research Articles

Enhancing interfacial stability in solid-state lithium batteries with polymer/garnet solid electrolyte and composite cathode framework

The solid-state lithium battery is considered as an ideal next-generation energy storage device owing to its high safety, high energy density and low cost. However, the poor ionic conductivity of solid electrolyte and low interfacial stability has hindered the application of solid-state lithium battery. Here, a flexible polymer/garnet solid electrolyte is prepared with poly(ethylene oxide), poly(vinylidene fluoride), Li 6.75 La 3 Zr 1.75 Ta 0.25 O 12 , lithium bis(trifluoromethanesulfonyl)imide and oxalate, which exhibits an ionic conductivity of 2.0 × 10 −4 S cm −1 at 55 °C, improved mechanical property, wide electrochemical window (4.8 V vs. Li/Li + ), enhanced thermal stabilities. Tiny acidic OX was introduced to inhibit the alkalinity reactions between Li 6.75 La 3 Zr 1.75 Ta 0.25 O 12 and poly(vinylidene fluoride). In order to improve the interfacial stability between cathode and electrolyte, an Al 2 O 3 @LiNi 0.5 Co 0.2 Mn 0.3 O 2 based composite cathode framework is also fabricated with poly(ethylene oxide) polymer and lithium salt as additives. The solid-state lithium battery assembled with polymer/garnet solid electrolyte and composite cathode framework demonstrates a high initial discharge capacity of 150.6 mAh g −1 and good capacity retention of 86.7% after 80 cycles at 0.2 C and 55 °C, which provides a promising choice for achieving the stable electrode/electrolyte interfacial contact in solid-state lithium batteries. An solid-state lithium metal battery was assembled with polymer/garnet solid electrolyte, composite cathode framework and lithium anode, exhibiting good electrochemical performance and high electrolyte/electrode interfacial stabilities.

Fast Ion Conduction and Its Origin in Li6–xPS5–xBr1+x

High ionic conductivity of solid electrolytes is key to achieving high-power all-solid-state rechargeable batteries. The superionic argyrodite family is among the most conductive Li-ion conductors....

Electrochemical stability and ionic conductivity of solid electrolytes based on Li10GeP2S12-x A x (A=O, Se. x=0, 0.2, 0.4, 0.6, 0.8, 1)

The compositions Li10GeP2S12-x A x (A = O, Se) solid electrolytes were synthesized. As x inreases, the ionic conductivity of the Li10GeP2S12-x O x samples decreases from 2.8 mS/cm to 1.09 mS/cm. Li10GeP2S11.8Se0.2 has the highest ionic conductivity, 3.43 mS/cm, and the activation energy of 0.143 eV. The electrochemical stability is Li10GeP2S11.6O0.4 > Li10GeP2S12 > Li10GeP2S11.8Se0.2, and the electrochemical window of Li10GeP2S11.6O0.4 is about 1.40 – 3.00 V. The difference in electrochemical properties of Li10GeP2S12-x A x (A = O, Se) can be used as a way to improve the interface of Li10GeP2S12-type solid batteries.

Nonflammable hybrid solid electrolyte membrane for a solid-state lithium battery compatible with conventional porous electrodes

Solid-state lithium batteries are highly promising for energy storage applications because of their high energy density and good safety characteristics. To promote the commercial progress of solid-state lithium batteries, solutions are desirable for two limitations of the technology: the low ionic conductivity of solid electrolytes and interfacial compatibility between electrolyte and electrodes. Here, we develop a hybrid solid electrolyte composed of Li7La3Zr2O12, ionic liquid, LiTFSI, and PVDF-HFP. Because its components are nonflammable, the hybrid solid electrolyte is likewise completely nonflammable. After pressing, the thickness of the hybrid solid electrolyte can be adjusted. The phase conversion of β-phase PVDF-HFP reduces the barrier of ionic conduction because of enhanced organic–inorganic interfacial ion transfer. More importantly, the ionic liquid stored in the hybrid solid electrolyte not only enhances the conductivity of the electrolyte but also solves the interfacial compatibility issue between solid electrolytes and conventional porous electrodes.

Li1+xAlxTi2−x (PO4)3, NASICON-type solid electrolyte fabrication with different methods

The research on solid electrolytes in lithium ion batteries has gained a significant attention recently. NASICON structured Li1+xAlxTi2−x(PO4)3 (LATP) material is interesting as a promising solid electrolyte for Li-ion batteries, because this type of electrolyte is more stable in the air than other types of solid electrolytes. The paper demonstrates the findings on synthesis of LATP material with two different sol-gel and a molten flux fabrication methods. The ionic conductivity of this type of solid electrolyte is found to be greatly affected by preparation methods. Characterization methods such as X-ray diffraction and scanning electron microscopy assisted in identifying the influence of different phases and grain sizes on ionic conductivity of solid electrolytes manufactured by different methods. Impedance spectroscopy of LATP by three synthesizing methods have demonstrated the ionic conductivity in the range of 10−4 – 10−6 S cm−1 at room temperature.

Enhancing ionic conductivity of solid electrolyte by lithium substitution in halogenated Li-Argyrodite

The demand for batteries with high safety and high energy density produces considerable efforts toward the development of all-solid-batteries and solid state electrolytes. Halogen-substituted lithium argyrodites, Li6PS5X (X = Cl, Br), represent a class of promising and suitable sulfide-based solid electrolytes with high conductivity and good processability. To further extend the scope and better understand the structure-property relationship, we systematically explore the effect of partial substitution of Li+ by other cations in Li6PS5X (X = Cl, Br). The X-ray diffraction (XRD) analysis shows the possibility of successful substitution at Li+ position by various cations. Among them, substitution with a small amount of Al3+ in Li6PS5Br is confirmed by Rietveld refinements. The ionic conductivity is improved by almost three times to 2.4 × 10−3 S cm−1. This improvement is attributed to the shortened distances of inter-cage jumps. In addition, the substituted sample shows better electrochemical performance in all-solid-state batteries. This work demonstrates the feasibility of performance improvement by manipulating the position of Li+ in the structure of lithium argyrodites, which provides a versatile approach toward designing better performing solid electrolytes.

Solid-state lithium metal batteries enabled with high loading composite cathode materials and ceramic-based composite electrolytes

The solid-state lithium batteries (SSLBs) are wide studied owing to its high safety and low cost. However, the poor ionic conductivity of solid electrolyte and low capacity of cathode limit its commercial application. In this paper, nanosized cubic phase Li6.75La3Zr1.75Ta0.25O12 powders is prepared via a simple solution combustion method and used to develop a ceramic-based composite solid electrolyte, which presents high ionic conductivity (1.05 × 10−4 S cm−1 at 25 °C), high lithium ion transference number tLi+ (0.74), wide electrochemical window (4.8 V vs. Li/Li+), excellent heat resistance and electrolyte-electrode interfacial stability. In addition, a high loading (~10.5 mg cm−2) LiNi0.5Co0.2Mn0.3O2 composite cathode with succinonitrile and lithium bis(trifluoromethanesulfonyl)imide as additives is used to fabricate SSLBs, which exhibits a high initial discharge capacity of 146.9 mA h g−1 and good capacity retention of 86.89% after 150 cycles at 0.1 C under 25 °C. The superior performance indicates that solid-state lithium battery assembled with composite solid electrolyte and high loading composite cathode provides a promising choice for the practical development of high-energy-density lithium batteries.

Polyacrylonitrile and Polypropylene Carbonate Blended Solid Polymer Electrolytes for Application Toward Solid State Lithium Ion Batteries

Lithium ion batteries are promising as energy storage devices because of their high energy density; however, current technology for lithium ion batteries is not safe for large scale applications and general use. Traditional lithium ion batteries use an organic liquid electrolyte to transport lithium ions between electrodes. Organic solvents used in lithium ion batteries, such as diethyl carbonate, are highly flammable and volatile. Safety issues arise when the battery heats from charging, discharging, or from dendrite formation in the cell. When this occurs, the battery can potentially ignite and pose a safety hazard. In this work, the research focus is developing blended solid polymer electrolytes for solid state lithium ion batteries. Polypropylene carbonate (PPC), an amorphous polymer, and polyacrylonitrile (PAN), a semi-crystalline polymer, have been shown to be individually effective for solid state lithium ion batteries. In this work, we fabricate novel PAN and PPC blended solid polymer electrolytes complexed with lithium bis(trifluoromethanesulfonyl)imide (LiTFSI). Furthermore, LiTFSI acts as both a source of lithium ions and as a plasticizer for the polymers, thus increasing the amorphous character of the polymer blend. Lithium ion conductivity is higher in amorphous electrolytes than in semi-crystalline solid polymer electrolytes. Solution casting, a commonly used technique for electrolyte fabrication, is used to control the thickness of the electrolyte film by varying the amount of solution added to the casting plate. During solution casting, the PPC and PAN undergo phase separation, this increases the number of micro-pores in the electrolyte. It has been shown that micro-pores improve the ionic conductivity of solid electrolytes. Upon evaporative drying of the solid polymer electrolytes, several tests are performed to characterize the electrolyte material as test well as battery performance.

(Invited) Thiophosphate Based Solid Electrolytes and Cathodes Interfaces

Stable high ion-conducting solid electrolytes are enablers for all solid state batteries. Among many class of materials, Lithium thiophosphate family of solid electrolytes have been investigated for their (a) superionic ion-conductivity (>10-4 S/cm), (b) mechanical softness and higher interfacial wettablity, (c) relatively simple synthesis and processing routes and (d) lower cost and earth abundance. Despite such advantages thiophosphates are known to have a narrow electrochemical stability window with a thermodynamical stability window between 1.7-2.6V (with respect to Li+/Li). Under such scenario, interfacial stability between Lithium thiophosphate/Li-metal and cathodes are primarily dictated by kinetic control by formation of a reaction passivation layer. Interfacial charge transfer depends on the detailed composition of the passivation reaction at the interface. The talk will highlight on the electrochemical performance characterization of the solid electrolyte, Li3PS4 and lithium-ion cathode such as LiFePO4. Detailed interfacial characterization between Li3PS4 and cathode interphases probed by XPS, NMR and electrochemical impedance spectroscopy (EIS) will be presented. In addition, synthesis and characterization of high capacity polysulfidophosphate cathodes based on catenation of sulfur to thiophosphate electrolytes, Li3(PS4)Sn where n = 5,8,6,3,2 will be discussed.

Surface-Engineered Boron Nitride Electrolytes for High Performance Solid-State Supercapacitors

In the modern era of smart wearable electronics and compact transportation systems, there is an urge for the development of solid, lightweight, flexible and efficient energy storage devices. For realizing high performance energy devices, novel electrolyte materials with high energy density at enhanced power are demanding. The recent developments in the field of two-dimensional (2D) materials, including graphene, 2D hexagonal boron nitride (2D-hBN) and transition metal dichalcogenides, have exhibited promise for a wide range of applications. In particular, 2D-hBN, also known as “white graphene” is an isomorph of graphene with similar layered structure in a hexagonal lattice, which is uniquely featured by its exotic opto-electrical properties together with mechanical robustness, thermal stability, and chemical inertness. Due to its remarkable electrochemical properties, it is considered as a promising candidate that can be integrated with other 2D materials, for the next generation electrochemical energy storage and conversion applications including fuel cells, batteries and supercapacitors Moreover, h-BN possess electrically insulating behavior at wide range of humidity and temperatures, which makes it more versatile to be manipulated and used as an electrolyte membrane in electrochemical energy systems. In order to realise hBN nanosheets (BNNS) potential as an ion-conductive solid electrolyte in advanced energy devices, scalable production techniques involving simple and efficient green synthesis routes are crucially required. Liquid phase exfoliation and ball milling are versatile techniques for the production of large-scale, defect-free, few-layered 2D materials. Further, steps of chemical functionalization are involved to produce surface-engineered BNNS solid-state electrolyte membranes with high ionic conductivity and durability, for electrochemical energy storage technologies. In this project, the solvent-assisted exfoliation method has been employed to produce few-layered BNNS. In this method a polar solvent with similar surface energy to that of BNNS (e.g. organic solvents such as DMF, or acids) is used to cleave BNNS through ultrasonication energy to produce few-layered, stable dispersions of BNNS. Then, high surface area of BNNS was engineered with ion-conductive groups enabling the transfer of ions (e.g., H+). The augmentation of BNNSs significantly improved their ion-conductivity and electrochemical stability properties through covalent and non-covalent bonding with the hexagonal BN network. As a result, significant enhancement in both of in-plane and through-plane ion-conductivity was observed at different operating conditions (e.g., 0.34 S/cm at 25 °C and 50% relative humidity). The surface-engineered BNNS materials acted as high-performance solid electrolyte membranes in solid-state supercapacitors. In addition to electrochemical measurements, microscopic, spectroscopic and structural characterization tests were applied to investigate the chemical and surface structures, surface functionalization mechanism, the ion-conductivity mechanism, and physical properties of the developed BNNS.

Long-Term Stable Lithium Metal Anode in Highly Concentrated Sulfolane-Based Electrolytes with Ultrafine Porous Polyimide Separator.

Highly concentrated solutions composed of lithium bis(fluorosulfonyl)imide (LiFSI) and sulfolane (SL) are promising liquid electrolytes for lithium metal batteries because of their high anodic stability, low flammability, and high compatibility with lithium metal anodes. However, it is still challenging to obtain the stable lithium metal anodes in the concentrated electrolytes due to their poor wettability to the conventional polyolefin separators. Here, we report that the highly concentrated 1:2.5 LiFSI/SL electrolyte coupled with a three-dimensionally ordered macroporous polyimide (3DOM PI) separator enables the stable lithium plating/stripping cycling with an average Coulombic efficiency of ca. 98% for over 400 cycles at 1.0 mA cm-2. The 3DOM PI separator shows good electrolyte wettability and large electrolyte uptake due to its high porosity and polar constituent of the imide structure, allowing superior cycling performance in the highly concentrated solution, compared with the polyolefin separators. Electrochemical and spectroscopic analyses reveal that the superior cycling stability in the concentrated electrolyte is attributed to the formation of highly stable and Li+ ion conductive solid electrolyte interphase (SEI) layer derived from FSI- anions, which reduces the side reactions of SL with lithium metal, prevents the growth of lithium dendrites, and suppresses the increase in cell impedance over long-term cycling. Our findings demonstrate that polar and porous separators could effectively improve the affinity to the concentrated electrolytes and allow the formation of the anion-derived SEI layer by increasing the salt concentration of the electrolytes, achieving the long-term stable lithium metal anode.

The Se2 (GAS) fugacity in systems with noble metals: chrisstanleyite Ag2Pd3Se4-naumannite Ag2Se-β-PdSe2 and luberoite Pt5Se4-sudovikovite PtSe2

The reactions of 6Ag(cr) + 3PdSe2(cr) = 2Ag2Se(cr) + Ag2Pd3Se4(cr) and 12Ag(cr) + 5PtSe2(cr) = 6Ag2Se(cr) + Pt5Se4(cr) were studied with the EMF method in a completely solid-state galvanic cell with an Ag ion-conducting solid electrolyte with overall gas space (Ar under atmospheric pressure). The EMF vs T dependencies were obtained in the temperature ranges of Т = 425-648 K and 501-713 K, respectively. Then, they were recalculated for gaseous Se fugacity in dependence on the temperature for non-variant equilibriums of Ag2Pd3Se4 (chrisstanleyite)-β-PdSe2 (the phase, which transforms into verbeekite under low temperatures)-Ag2Se (naumannite) and Pt5Se4 (luberoite)-PtSe2 (sudovikovite): logfSe2(gas)(Ag2Pd3Se4/Ag2Se/PdSe2) = 7.71 ± 0.05 - 8.524 ± 0.026(1000/T), logfSe2(gas)(Pt5Se4/PtSe2) = 7.135 ± 0.027 - 12.274 ± 0.016(1000/T).

Reconfigurable solid-state electrolytes for high performance flexible supercapacitor

To realize high performance and a flexible supercapacitor, it is necessary to address the fundamental issues including low ionic conductivity of solid electrolytes and high interfacial resistance of electrode/electrolyte pairs. Here we present unique solid-state electrolytes by integrating highly engineered nano-porous polyvinyl alcohol (PVA) with super-flat vertically aligned single-walled carbon nanotubes (VA-SWNTs). Highly engineered PVA nano-porous films are fabricated by a generic freeze-thaw process followed by water-miscible solvent treatment in order to create highly controlled nano/microscale pores inside of PVA. Such highly porous PVA films act as both reconfigurable electrolyte template and separator where H3PO4 aqueous solution or ionic liquids can be selectively inserted for a variety of power requirements in flexible electronic applications. Our developed pore formation process is suitable for directly integrating high performance VA-SWNTs electrode as it allows the effective permeation of the polymer electrolyte into nanoscale inter-tube space enabling the easy access and faster transport of ions for higher power capability. This unique entity of reconfigurable electrolyte and nanostructured electrode demonstrates high power and energy densities and remarkable stability after 10,000 charge/discharge cycles.

Dendrite-Free Epitaxial Growth of Lithium for Efficient Charging of Li–O2 Batteries with Improved Cycle Life

Realization of rechargeable Li-metal batteries with high energy density is hindered by uneven Li deposition leading to dendrite formation during repeated cycles. Uncontrolled dendrite growth induces internal short-circuits which limit the cell lifetime and generate ohmic heat leading to catastrophic failure when a volatile electrolyte is used. Several strategies have been conceived by the researchers to suppress dendritic growth and delay the premature death of the cell. These efforts include using electrolyte additives to form a porous ion-conducting solid electrolyte interphase (SEI) layer on metal preventing further reaction,1 implementing solid electrolytes with optimum mechanical properties,2 designing a Li matrix,3 reducing local space charge on the Li surface,4 and so on. Although considerable improvements have been achieved from these earlier studies, microscopically smooth Li surface covered with thin and uniform SEI layers is yet to be realized. Alternatively, here we show an unprecedented dendrite-free epitaxial electrodeposition of Li in the presence of LiBr–LiNO3/glyme ether electrolyte under O2 atmosphere. Stripping and plating of Li metal was investigated by using a symmetrical Li│Li cell and it has been found that in 1 M LiNO3+0.05 M LiBr/tetraglyme electrolyte the plating of Li metal shows dendrite-free epitaxial growth up to a thickness of >20 μm which is clearly observed by the scanning electron microscopic (SEM) images and electron backscatter diffraction (EBSD) signal in Figure 1. The epitaxial growth of Li metal seems to be benefited from the synergistic effect of the anions Br− and NO3 − forming a thin and homogeneous Li2O–rich solid electrolyte interphase (SEI) layer which is formed during the very first discharge (stripping) process, where the corrosive nature of Br− removes the original thick passivation layer on Li surface which is then again oxidized (passivated) by the NO3 − to prevent further reactions with the electrolyte. Because of this, the SEI layer remains thin and facilitates the electropolishing effect and gets ready for the epitaxial electroplating of Li in the following charge process. Similar epitaxial growths of Li have been observed for both symmetrical Li│Li cell and Li–O2 full cell resulting in a much improved performance with longer cycle life.5,6 However, in contrast, LiNO3 alone or other lithium salts, such as Lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), Lithium trifluoromethanesulfonate (LiTf), do not exhibit any epitaxial Li deposition. This demonstrates the bi-functional activity of the dual anion electrolyte LiNO3–LiBr towards dendrite-free epitaxial growth of Li. The role of deposition rate, effect of electrolyte solvent and a detailed mechanism of epitaxial growth will be discussed in the presentation.

Mitigating self-discharge of carbon-based electrochemical capacitors by modifying their electric-double layer to maximize energy efficiency

Abstract Self-discharge is a significant issue in electric double layer energy storage, which leads to a rapid voltage drop and low energy efficiency. Here, we attempt to solve this problem by changing the structure of the electric double layer into a de-solvated state, by constructing a nano-scale and ion-conductive solid electrolyte layer on the surface of a carbon electrode. The ion concentration gradient and potential field that drive the self-discharge are greatly restricted inside this electric double layer. Based on this understanding, a high-efficiency graphene-based lithium ion capacitor was built up, in which the self-discharge rate is reduced by 50% and the energy efficiency is doubled. The capacitor also has a high energy density, high power output and long life, and shows promise for practical applications.

Synthesis and characterization of divalent ion conductors with NASICON-type structures

ABSTRACTDivalent ion-conducting solid electrolytes with NASICON-type three-dimensional network structures (MxHf1−x)4/(4−2x)Nb(PO4)3 (M = Ni, Mg, Ca, Sr) were successfully developed by introducing M2+ cations into HfNb(PO4)3 solids. The presence of high-valence cations such as Hf4+, Nb5+, and P5+ in the structures effectively reduced the electrostatic interaction between the conducting M2+ cations and the surrounding oxide anions, enabling the M2+ cations to migrate smoothly in the rigid crystal lattice. The relationship between the cation conductivity in NASICON-type solids and the ionic radius of the migrating divalent cation species was also clarified by taking into account the relative sizes of the conduction pathways in the structures.

The Se2 (Gas) Fugacity in Systems with Noble Metals: Chrisstanleyite Ag2Pd3Se4 – Naumannite Ag2Se–β-PdSe2 and Luberoite Pt5Se4–Sudovikovite PtSe2

The reactions of 6Ag(cr) + 3PdSe2(cr) = 2Ag2Se(cr) + Ag2Pd3Se4(cr) and 12Ag(cr) + 5PtSe2(cr) = 6Ag2Se(cr) + Pt5Se4(cr) were studied with the EMF method in a completely solid-state galvanic cell with an Ag ion-conducting solid electrolyte with overall gas space (argon under atmospheric pressure). The EMF vs. temperature dependencies were obtained in the temperature ranges of Т = 425–648 K and 501–713 K, respectively. Then, they were recalculated for gaseous Se fugacity in dependence on the temperature for nonvariant equilibriums of Ag2Pd3Se4 (chrisstanleyite)–β-PdSe2 (the phase, which transforms into verbeekite under low temperatures)–Ag2Se (naumannite) and Pt5Se4 (luberoite)–PtSe2 (sudovikovite): logf Se2(gas) (Ag2Pd3Se4/Ag2Se/PdSe2) = 7.710 ± 0.050 – 8.524 ± 0.026(1000/T), logfSe2(gas) (Pt5Se4/PtSe2) = 7.135 ± 0.027 – 12.274 ± 0.016(1000/T).

Bonding character and ionic conduction in solid electrolytes

Abstract The properties of the materials are intimately related to the nature of the chemical bond. Research to explain the peculiarities of superionic materials by focusing on the bonding character of the materials is presented. In particular, a brief review of some fundamental aspects of superionic conductors is given based on the talk presented at “Solid State Chemistry 2018, Pardubice” in addition to some new results related to the subject. Specifically, the topics on bond fluctuation model of ionic conductors, the role of medium range structure in the ionic conductivity, bonding aspects of non-Arrhenius ionic conductivity and elastic properties of ionic conductors are discussed. Key concepts that are gained from these studies is stressed, such as the importance of the coexistence of different types of bonding, and the role of medium range structure in glasses for efficient ionic transport in solids. These concepts could help the development of new materials.

(Invited) In-Situ X-Ray Imaging Analysis of Diffusion Phenomena in All-Solid-State Battery Using Ag-Ion

All-solid-state rechargeable battery is one of the candidates of post-lithium-ion batteries. In recent years, the intrinsic charge-discharge performance of active materials and the ionic conductivity of solid electrolytes have dramatically improved; however, the dynamic behavior of carrier ion in the composite electrode has not been understood for the performance of battery pack. If the transport number in the solid electrolyte is almost one, it is considered that salt concentration distribution does not occur in principle. Due to this advantage, the thicker electrodes can be realized for all-solid-state rechargeable battery. However, as far as the authors know, the direct observation of carrier ions during operation of all-solid state rechargeable batteries has not been reported. This is because it is difficult to observe the behavior of lithium ions which are general carrier ions but are light elements. Therefore, in this research, as a model of all-solid-state rechargeable batteries, we used silver ion conductor which shows much high ionic conductivity. The dynamic behavior of silver ion in solid electrolyte and electrode during battery operation was investigated by high energy X-ray imaging method with synchrotron radiation. Ag6I4WO4 was used as the solid electrolyte, and in the case of the electrolyte observation, silver used as both electrodes. The pressed cell component was sliced with the thickness of 300 mm. In the case of the electrode observation, TiTe2 was used as the working electrode and silver was used as the counter electrode. X-ray transmission imaging measurements were performed in SPring-8. Compared with the reference samples of Ag6+xI4WO4 (x = 0, 0.06, 0.17, 0.31), it was shown that noticeable ion concentration distribution similar to that of the battery using the organic electrolytic solution as the electrolyte during charge / discharge does not occur. On the other hand, dendrite growth in the solid electrolyte due to silver deposition and reaction distribution in the electrode were observed. In this presentation, we will provide the direct observation of silver ion diffusion in composite electrode.

Synergistic Effect of Cycling Strategies and Electrolyte for Effective Plating/Stripping of Anode Free Li Metal Batteries.

Anode-free batteries (AFBs) are impressive and recent phenomena in the era of energy storage devices due to their high energy density and relative ease of production. However, dendrite formation during plating and stripping and low coulombic efficiency (CE) are the main challenges that impede practical implementation of these batteries. Here we report an extremely stable dual-salt electrolyte, 2M LiFSI+1M LiTFSI (2FSI+1TFSI)) in DME-DOL (1:1, v/v), system in comparison to the single salt 3M LiTFSI (3TFSI) in DME-DOL (1:1, v/v), to effectively stabilize AFB composed of LiFePO4 (LFP) cathode and bare Cu-foil anode for the first time. The electrolyte stabilized anode-free cell with the configuration Cu||LFP via reductive decomposition of its anions and enabled the cell to be cycled with CE of 98.9% for more than 60 cycles, which by far exceeds all the few reports in this field using other kinds of electrolytes. This results from formation of stable, ion conductive inorganic components rich Solid Electrolyte Interface (SEI) layer on the surface of in-situ formed Li-metal that prevent its direct contact with the electrolytes and hence intercepts undesirable parasitic reaction between Li and the electrolyte. Thus aforesaid SEI formed from reductive decomposition components of the dual-salt mitigates formation of dead lithium and dissolution of the in-situ formed Li surface during repeated cycling and prolongs cycle life of the battery.