High Lithium Ion Conductivity Research Articles

High lithium-ion conductivity in all-solid-state lithium batteries by Sb doping LLZO

High lithium-ion conductivity in all-solid-state lithium batteries by Sb doping LLZO

Safety-enhanced Polymer Electrolytes with High Ambient-temperature Lithium-ion Conductivity Based on ABA Triblock Copolymers

Safety-enhanced Polymer Electrolytes with High Ambient-temperature Lithium-ion Conductivity Based on ABA Triblock Copolymers

Garnet-Based Electrolytes for Advanced All-Solid-State Lithium Battery

All-solid-state lithium batteries are emerging as one of the key energy storage technologies due to their high theoretical energy density compared to conventional lithium- and sodium-ion-based batteries [1]. The present lithium batteries such as Li-S batteries suffer from Li dendrite formation and capacity decay due to polysulfide dissolution effect – a typical problem with liquid organic electrolytes [2]. Solid-state (ceramic) electrolytes are promising to prevent Li dendrite growth and polysulfide dissolution. Among the different ceramic electrolytes, garnet-type structure solid inorganic electrolytes are very promising because of their high lithium-ion conductivity and stability with elemental Li and humidity [3,4]. However, high interfacial resistance with the electrode is the major bottleneck for practical use of ceramic electrolytes [1]. In this talk, we will present strategies to solve the interfacial resistance issue in garnet-based electrolytes. Elemental doping [5], solution-based interface engineering [6], and hybrid polymer-ceramic electrolyte approach [7] will be discussed. Methods to improve lithium battery electrodes such as sulfur with minimal polysulfide shuttle effect will also be introduced [2]. References J. Samson, K. Hofstetter, S. Bag, and V Thangadurai,* “A bird's-eye view of Li-stuffed garnet-type Li7La3Zr2O12 ceramic electrolytes for advanced all-solid-state Li batteries,” Energy Environ. Sci., 12, 2957-2975 (2019).M. Abraham, S. P. Kammampata, S. Ponnurangam, and V. Thangadurai,* “Efficient Synthesis and Characterization of Robust MoS2 and S Cathode for Advanced Li-S Battery: Combined Experimental and Theoretical Studies,” ACS Appl. Mater. Interfaces 11, 35729-35737 (2019).Hofstetter, A. J. Samson, J. Dai, J. E. Gritton, L. Hu, E. D. Wachsman, and V. Thangadurai,* “Eelectrochemical stability of garnet-type Li7La2.75Ca0.25Zr1.75Nb0.25O12 with and without atomic layer deposited-Al2O3 under CO2 and humidity,” J. Electrochem. Soc., 166, A1844-A1852 (2019).Hofstetter, A. J. Samson, S. Narayanan, and V. Thangadurai,*“Present understanding of the stability of Li-stuffed garnets with moisture, carbon dioxide, and metallic lithium,” J. Power Sources, 390, 297–312 (2018).J. Samson, K. Hofstetter, E. Wachsman, and V. Thangadurai,*“Towards Mixed Ionic and Electronic Conducting Li-Stuffed Garnets,” J. Electrochem. Soc., 165, A1-A9 (2018).Zhou, A. J. Samson, K. Hofstetter, and V. Thangadurai,*Surfactant-Assisted Strategy to Tailor Li-ion Charge Transfer Interfacial Resistance for Scalable All-Solid-State Li Batteries, Sustainable Energy Fuels, 2, 2165 – 2170 (2018).Bag, C. Zhou, P.J. Kim, V.G. Pol, and V Thangadurai,* “LiF modified stable flexible PVDF-garnet hybrid electrolyte for high performance all-solid-state Li-S batteries,” Energy Storage Mater., 24, 198-207 (2020).

In Situ Transmission Electron Microscopy Analysis of Microstructure Evolution of the Li6PS5cl Solid Electrolyte in Charge/Discharge Process

All solid state lithium battery has been attracting attention for its high energy density and safety compared to current lithium ion battery. Here, sulfide-based solid electrolytes (SEs) such as Li6PS5Cl have extremely high lithium ion conductivity, which make them promising candidate for the application. However, their stability against lithium metal anode is under debate. And how does the SE reacts with the Li metal in contact and its effect on the performance is not well understood.In this work, we conducted in situ transmission electron microscopy (TEM) experiments to directly observe the structural changes of Li6PS5Cl (LPSCl) solid electrolyte in contact with lithium metal under bias to clarify its stability against lithium. After contacting them under -1 V of biasing on LPSCl with respect to the lithium metal, the surface of the LPSCl shrunk. Electron diffraction pattern analysis revealed that the initial crystalline structure was lost and LPSCl was amorphized upon contact with lithium. The reaction propagated ~1.5 mm after 4 minutes of biasing, and the structural change was irreversible. In addition, lithium transport through the SE/SE boundary was observed to study the degradation due to the Li concentration gradient at the grain boundaries caused by the slower Li diffusion across the boundaries. When a bias potential was applied across the SE/SE interface between two LPSCl particles, a change in the contrast at the interface was observed. After the two particles were detached, the particle slowly recovered the original contrast. The result indicates there was a shift of Li ions within the particle away from the SE/SE interface due to the driving force from the applied bias. To investigate the structural evolution in the grain boundaries under charge/discharge process, alternating bias potential was applied between the LPSCl particles. The change in the electron diffraction pattern during the alternating bias experiment showed emerging peaks for Li2S, which implies the repeating shift of Li ions within the LPSCl altered the electrolyte structure that may degrade the performance of the SE.Observations in this work revealed that the degradations of the SE may take place at the grain boundaries in addition to the electrochemical interface with lithium metal. The structural change at the grain boundaries may cause reduced ionic conductivity and/or increased electrical conductance which may lead to lithium precipitation inside the SEs that can cause catastrophic failure of the battery due to shorting. Figure caption : In situ TEM observation of lithium shift at SE/SE interface in Li6PS5Cl solid electrolyte under alternating bias potential between -3 and +3 V. Figure 1

Rapid Laser Reactive Sintering of Li7La3Zr2O12-Based Solid State Battery Electrolytes

Solid-state lithium-ion batteries (SSLIBs) have gained significant interest in recent years due to their wide range of applications, including mobile devices, electric vehicles, and grid storage. Garnet-type Li7La3Zr2O12 (LLZO) solid-state electrolyte (SSE) continues to be a significant player in the fabrication of ASSLIBs with excellent ionic conductivity on the order of 10-3 S⸱cm-1 with the integration of dopants and sintering aids to assist conductivity and structural evolution during the sintering procedure. Traditional sintering techniques, such as solid-state sintering (SSS), have been proven to yield desirable crystal structures. However, the low ionic conductivity resulted from inferior microstructure, and lithium loss is a significant challenge. Recently, a relatively novel sintering process called rapid laser reactive sintering (RLRS) has shown great potential for achieving fully dense solid oxide electrolytes with less surface element loss, resulted in high ionic conductivity. Here, we applied the same RLRS method to fabricate LLZO dense electrolyte with different amounts of aluminum dopants. We hope the rapid high-temperature sintering can densify the electrolyte and avoid the lithium loss for achieving high lithium-ion conductivity. In this work, we optimized multiple combinations of laser parameters (speed, power, and defocus distance), initial precursor composition, and controlled atmospheres to discover the optimal conditions for reaching the efficacious crystal structure, microstructure, and ionic conductivity.

(Invited) Enabling Reversible Plating and Stripping of Lithium Metal in Lithium Metal Batteries

Lithium metal batteries with lithium metal anodes have the potential to almost double the energy density of today's lithium-ion batteries. However, non-uniform lithium plating and stripping causes poor cycling stability, low Coulombic efficiency, potential safety issues, and has hindered the commercialization of lithium metal batteries at scale. We discuss several promising strategies to achieve stable lithium plating and stripping.We report a nanocomposite coating for the protection of lithium metal anodes, which consists of nano-sized LiF particles embedded into a PEO polymer matrix [1]. The composite offers a large LiF/PEO interface area throughout the coating, promoting exceptionally high lithium-ion conductivity of 0.97 mS cm–1 and high lithium-ion transference number of 0.77 at room temperature in contact with a carbonate-based liquid electrolyte. Both properties are key to realize uniform lithium plating and stripping and prevent lithium dendrite formation. Lithium metal electrodes coated with this protective coating enable stable lithium plating and stripping at 1 mA cm–2 for over 1000 h at room temperature. A full cell with the coated lithium metal anode and a NMC622 cathode with an areal capacity of 1 mAh cm–2 shows much improved specific capacity and cycling stability at high current density. The cell exhibits a high initial capacity of 135 mAh g–1 and 83% capacity retention after 500 cycles at 1 mA cm–2. Even at a high current density of 3 mA cm–2, the full cell shows an initial capacity of 125 mAh g–1 and 74% capacity retention after 300 cycles.We will also discuss challenges and opportunities to stabilize plating and stripping of lithium metal in all-solid-state batteries [2-4].[1] C. Fu and C. Battaglia, ACS Appl. Mater. Interf. 2020, 12, 41620[2] M. Bay, M. Wang, R. Grissa, M. V. F. Heinz, J. Sakamoto, and C. Battaglia, Adv. Energy Mater. 2019, 1902899[3] R. Grissa, S. Payandeh, M. Heinz, and C. Battaglia, ACS Appl. Mater. Interf. 2021, 13, 14700[4] F. Pagani, C. Fu, and C. Battaglia, in preparation

Superionic Fluorinated Halide Solid Electrolytes for Highly Stable Li‐Metal in All‐Solid‐State Li Batteries

AbstractThe halide solid‐state electrolytes (SSEs) have received significant attention due to their high ionic conductivity and desirable compatibility with cathode materials. However, the reduction potential of the halide is still >0.6 V (versus Li/Li+). Reduction stability is still one of the challenges that need to be addressed. The fluorides have a wide electrochemical stability window due to the large electronegativity of F–. In contrast, Li3YBr6 (LYB) bromides have a narrower electrochemical window, although they have high lithium ion conductivity (>10–3 S cm–1). Herein, a fluorine doping strategy is employed. The interfacial stability between fluoride‐doped bromides and lithium metal is researched by cycling of lithium symmetric cells. Li plating/stripping can maintain over 1000 h at 0.75 mA cm–2. Interfacial protection mechanisms investigated by X‐ray photoelectron spectroscopy. A fluoride‐rich interfacial layer is formed in situ during the cycle, which achieves inhibition of the reduction. The Li metal treated fluorine doping of LYB exhibits significant potential in full cells. In fact, the induction of a stable in situ interfacial layer by fluorine doping can effectively improve the interfacial stability of bromides to lithium metal. Fluorine‐doped modification offers a new attempt to realize lithium metal applications in all‐solid‐state lithium batteries.

PEO Infiltration of Porous Garnet-Type Lithium-Conducting Solid Electrolyte Thin Films

Composite electrolytes containing lithium ion conducting polymer matrix and ceramic filler are promising solid-state electrolytes for all solid-state lithium ion batteries due to their wide electrochemical stability window, high lithium ion conductivity and low electrode/electrolyte interfacial resistance. In this study, we report on the polymer infiltration of porous thin films of aluminum-doped cubic garnet fabricated via a combination of nebulized spray pyrolysis and spin coating with subsequent post annealing at 1173 K. This method offers a simple and easy route for the fabrication of a three-dimensional porous garnet network with a thickness in the range of 50 to 100 µm, which could be used as the ceramic backbone providing a continuous pathway for lithium ion transport in composite electrolytes. The porous microstructure of the fabricated thin films is confirmed via scanning electron microscopy. Ionic conductivity of the pristine films is determined via electrochemical impedance spectroscopy. We show that annealing times have a significant impact on the ionic conductivity of the films. The subsequent polymer infiltration of the porous garnet films shows a maximum ionic conductivity of 5.3 × 10−7 S cm−1 at 298 K, which is six orders of magnitude higher than the pristine porous garnet film.

Glass-ceramics based on Li1.5Al0.5Ge1.5(PO4)3 for advanced all-solid-state batteries

Glass-ceramic electrolytes of the Li1.5Al0.5Ge1.5(PO4)3-xB2O3 series (0≤x≤0.15 wt%) were obtained by glass crystallization under the same conditions of heat treatment. The influence of B2O3 addition on the phase composition and unit cell parameters of lithium-aluminium-germanium-phosphate glass-ceramics was investigated by XRD. The obtained solid electrolytes have the NASICON-type structure with space group R-3c. Glass-ceramics is single-phase at 0≤x≤0.15. Transport properties of glass-ceramics electrolytes were investigated by impedance spectroscopy. The conductivity of Li1.5Al0.5Ge1.5(PO4)3 was found to be lower compared to the B2O3-added solid electrolytes. Namely, the composition with 0.05 wt% has the highest lithium-ion conductivity, which is 5.5·10−4 S/cm at 25 °C. Also the thermal compatibility of Li1.5Al0.5Ge1.5(PO4)3 solid electrolyte with Li4T5O12 anode material and the influence of Li3BO3 addition on their compatibility were investigated by DSC method.

Enhanced Electrochemical Stability and Moisture Reactivity of Al2S3 Doped Argyrodite Solid Electrolyte

All-solid-state lithium-ion batteries are considered a promising next-generation lithium-ion batteries for their safety and high energy density. Among solid electrolytes, sulfide-based solid electrolytes have received attention from academia for their good contact properties such as mechanical deformability and high ionic conductivity. Specifically, argyrodite, which has Li6PS5X (X = Cl, Br, I) structure, shows a high lithium ionic conductivity (>10−3 S cm−1) at room temperature. However, sulfide-based solid electrolytes are chemically unstable in reaction to lithium metal and moisture because of the high reactivity of sulfur. Also, sulfide-based solid electrolytes react with active materials on the interface in composite cathodes. Moreover, this insufficient electrochemical stability of sulfide-based solid electrolytes can deteriorate the cell performance such as discharge capacity in prolonged cycles. We investigated the effects of partial substitution of Al2S3 for P2S5 to form the Al-S bonding instead of the P-S bonding in the PS4 3− main unit of the Li6PS5X structure. The Al-S bonding is electrochemically more stable than the P-S bonding due to a larger electronegativity difference between the two atoms. We show that the Al2S3 substitution in an argyrodite structure used for the composite cathode significantly improves the electrochemical stability.

Compositional Dependence of Li-Ion Conductivity in Garnet-Rich Composite Electrolytes for All-Solid-State Lithium-Ion Batteries-Toward Understanding the Drawbacks of Ceramic-Rich Composites.

Composite electrolytes comprising a polymer plus Li salt matrix and embedded fillers have the potential of realizing high lithium-ion conductivity, good mechanical properties, wide electrochemical operational window, and stability against metallic lithium, all of which are essential for the development of high-energy-density all-solid-state lithium-ion batteries. In this study, a solvent-free approach has been used to prepare composite electrolytes with tetragonal and cubic phase garnets synthesized via nebulized spray pyrolysis with polyethylene oxide (PEO) being the polymer component. Electrochemical impedance spectroscopy (EIS) is used to examine a series of composites with different garnets and weight fractions. The results show that with the increase in the ceramic weight fraction in the composites, ionic conductivity is reduced and alternative Li-ion transport pathways become accessible for composites as compared to the filler-free electrolytes. An attempt is made to understand the ion transport mechanism within the composites. The role of the chemical and morphological properties of the ceramic filler in polymer-rich and ceramic-rich composite electrolytes is explained by studying the blends of nonconducting ceramics with the Li-conducting polymer, indicating that the intrinsic conductivity of the ceramic filler significantly contributes to the overall conductive process in the ceramic-rich systems. Further, the stability of the garnet/PEO interface is studied via X-ray photoelectron spectroscopy, and its impact on the lithium-ion transport is studied using EIS.

Aliovalent substitution in phosphide‐based materials – Crystal structures of Na10AlTaP6 and Na3GaP2 featuring edge‐sharing EP4 tetrahedra (E=Al/Ta and Ga)

AbstractRecently, ternary lithium phosphides have been studied intensively owing to their high lithium ion conductivities. Much less is known about the corresponding sodium‐containing compounds, and during investigations aiming for sodium phosphidotrielates, two new compounds have been obtained. The sodium phosphidoaluminumtantalate Na10AlTaP6, at first obtained as a by‐product from the reaction with the container material, crystallizes in the monoclinic space group P21/n (no. 14) with lattice parameters of a=8.0790(3) Å, b=7.3489(2) Å, c=13.2054(4) Å, and β=90.773(2)°. The crystal structure contains dimers of edge‐sharing [(Al0.5Ta0.5)P4] tetrahedra with a mixed Al/Ta site. DFT calculations support the presence of this type of arrangement instead of homonuclear Al2P6 or Ta2P6 dimers. The 31P and 23Na MAS NMR as well as the Raman spectra confirm the structure model. The assignment of the chemical shifts is confirmed applying the DFT‐PBE method on the basis of the ordered structural model with mixed AlTaP6 dimers. The sodium phosphidogallate Na3GaP2 crystallizes in the orthorhombic space group Ibam (no. 72) with lattice parameters of a=13.081(3) Å, b=6.728(1) Å, and c=6.211(1) Å and is isotypic to Na3AlP2. Na3GaP2 exhibits linear chains of edge‐sharing 1∞[GaP4/2] tetrahedra. For both compounds band structure calculations predict indirect band gaps of 2.9 eV.

Lithium-Rich Anti-perovskite Li2OHBr-Based Polymer Electrolytes Enabling an Improved Interfacial Stability with a Three-Dimensional-Structured Lithium Metal Anode in All-Solid-State Batteries.

All-solid-state lithium-metal batteries, with their high energy density and high-level safety, are promising next-generation energy storage devices. Their current performance is however compromised by lithium dendrite formation. Although using 3D-structured metal-based electrode materials as hosts to store lithium metal has the potential to suppress the lithium dendrite growth by providing a high surface area with lithiophilic sites, their rigid and ragged interface with solid-state electrolytes is detrimental to the battery performance. Herein, we show that Li2OHBr-containing poly(ethylene oxide) (PEO) polymer electrolytes can be used as a flexible solid-state electrolyte to mitigate the interfacial issues of 3D-structured metal-based electrodes and suppress the lithium dendrite formation. The presence of Li2OHBr in a PEO matrix can simultaneously improve the mechanical strength and lithium ion conductivity of the polymer electrolyte. It is confirmed that Li2OHBr does not only induce the PEO transformation of a crystalline phase to an amorphous phase but also serves as an anti-perovskite superionic conductor providing additional lithium ion transport pathways and hence improves the lithium ion conductivity. The good interfacial contact and high lithium ion conductivity provide sufficient lithium deposition sites and uniform lithium ion flux to regulate the lithium deposition without the formation of lithium dendrites. Consequently, the Li2OHBr-containing PEO polymer electrolyte in a lithium-metal battery with a 3D-structured lithium/copper mesh composite anode is able to improve the cycle stability and rate performance. The results of this study provide the experimental proof of the beneficial effects of the Li2OHBr-containing PEO polymer electrolyte on the 3D-structured lithium metal anode.

A thin and flexible solid electrolyte templated by controllable porous nanocomposites toward extremely high performance all-solid-state lithium-ion batteries

Composite solid-state electrolytes (CSEs) with high ionic conductivity and low interfacial resistance have been pursued for next‐generation high energy density all solid-state lithium-ion batteries (ASSLIBs). Herein, we report a novel strategy of developing thin, flexible, and conductive CSEs by using lignin nanoparticles (LNPs) to regulate pore characteristics of cellulose nanofibril (CNF) film template. The CNF-LNP film was first prepared, then LNPs were removed, thanks to the excellent LNP solubility in γ-Valerolactone (GVL), resulting in the formation of uniform and porous cellulose nanofibril (CNF) film, which is then utilized for preparing Li7La3Zr2O12 (LLZO) membrane, with a superior morphological architecture (pore size, uniformity). Poly (ethylene oxide) (PEO) is then infiltrated into the membrane, producing thin, flexible, and conductive CSEs. Due to the controllable interconnected architecture of LLZO membrane from the LNP regulated CNF film template and its good compatibility with PEO, the as-prepared CSEs exhibit a high lithium ionic conductivity of 1.83 × 10−4 S cm−1 at ambient temperature. The continuous and uniform lithium transfer pathways, with excellent electrolyte/electrode interface contact contribute to long-term cycling stability of symmetric lithium batteries. Hence, the assembled ASSLIBs from the as-prepared CSEs show high discharge specific capacities of 157 and 159.5 mAh g−1 with LiFePO4 and LiNi0.5Mn0.3Co0.2O2 respectively, with attractive cycling stabilities and capacity retention at ambient temperature.

Freeform Lithium Superionic Conductor

The key challenge in all-solid-state batteries (ASSBs) is establishing perfect physical contact between rigid components for facile interfacial charge transfer, especially between the solid electrolyte and cathode. Here, we introduce a new class of shapeable inorganic-based solid electrolytes with a liquid-like sublattice that can form intimate contact with the rigid cathode. The electrolyte exhibits extraordinary clay-like mechanical properties (storage and loss moduli < 1 MPa) at room temperature, high lithium ion conductivity (3.4 mS cm-1), and a glass transition below -50 ℃. The unique mechanical features provide liquid-like penetration into the porous cathode and ionic conduction paths for all cathode particles, delivering a high energy density. We propose a design principle that the complex anion formation including Ga, F and a different halogen can induce the clay-like features. Our findings provide new opportunities in the search for solid electrolytes and suggest a new approach for resolving the issues caused by the solid electrolyte–cathode interface in ASSBs.

Lithium-Ion Conductivity of Mixed-Anion Chloride Solid Electrolyte

Lithium-ion batteries are required to have high energy density, high cycle characteristics, and safety to be used for electric vehicles. Current lithium-ion batteries use a flammable organic electrolyte as electrolyte suffers from safety issues. All-solid-state batteries using non-flammable solid electrolytes are attracting attention because they can improve safety and energy density. The practical use of all-solid-state batteries requires solid electrolytes having higher conductivity, atmospheric stability, electrochemical stability, and moldability than conventional liquid electrolytes. However, no material that combines everything has been found at present.Solid electrolytes are divided into two main types: oxide-based and sulfide-based materials. As oxide-based solid electrolytes, garnet-type Li7La3Zr2O12, which shows the room-temperature ionic conductivity is 5.1 × 10-4 S / cm, has been developed [1]. Generally, oxide-based materials have high atmospheric stability and are stable to oxide-based cathode materials, but the ionic conductivity is lower than sulfide-based materials, and a high-temperature process is required for synthesis. As sulfide-based solid electrolytes, crystalline Li10GeP2S12, which shows the room-temperature ionic conductivity is 1.2 × 10-2 S / cm, has been developed [2]. Sulfide-based materials have a relatively higher ionic conductivity than oxide-based materials. Moreover, sulfide-based materials have high moldability and can be synthesized at a lower temperature than oxide-based materials. However, sulfide-based materials have the disadvantages of low atmospheric stability, are at risk of reacting with water to generate H2S, and have low stability to oxide-based cathode materials.High ionic conductivity solid electrolytes have been discovered mainly in oxide-based and sulfide-based materials. In addition, recently, it has been reported that lithium conductive solid electrolytes of halide-based materials have high ionic conductivity, and the material-searching region is expanding. Halide-based materials are considered to have high ionic conductivity due to the properties of halogen anions. Since the monovalent halogen anion has a weaker interaction with lithium ions than the divalent sulfur and oxygen anions, high-speed transport of lithium ions can be expected. In addition, the ionic radius of the halogen anion is relatively large, and the halogen anion has high polarizability. Li3YCl6, Li3YBr6 and Li3InCl6, which show the room-temperature ionic conductivity is 10-3 S / cm have been reported as lithium halide solid electrolyte materials [3], [4].Most of these lithium halide solid electrolyte materials are single-anion compounds, and little research has been conducted on mixed-anion compounds as lithium-ion conductors. In this study, we focused on the chloride-based solid electrolyte Li3InCl6, which is reported to have high lithium-ion conductivity comparable to oxide and sulfide-based materials and is expected to have higher chemical stability than sulfide-based materials. The characteristics of the solid electrolyte when Li3InCl6 was doped with a group 16 element were investigated. A composite anion compound in which oxygen, sulfur, and selenium, which have higher polarizabilities than chlorine, were dissolved was synthesized, and the conductivity characteristics were analyzed by electrochemical measurement. Li3InCl6, Li3InCl5.4O0.3, Li3In0.9Cl5.4O0.15, Li3In0.82Cl5.4O0.03, Li3InCl5.4S0.3, Li3InCl5.4S0.6 and Li3InCl5.4Se0.6 samples were synthesized by mechanochemical method and solid-phase reaction in an argon atmosphere. The crystal structure of the synthesized samples was characterized by X-ray diffraction (XRD), and the ionic conductivity was measured by AC impedance measurements. Comparing the XRD patterns of the Li3InCl6 sample and each sample, a peak of impurities was confirmed for the oxygen solid solution sample, and a decrease in crystallinity was confirmed for the sulfur and selenium solid solution samples. The conductivity of each sample decreased in the order of Li3InCl6> Li3In0.82Cl5.4O0.03 > Li3In0.9Cl5.4O0.15 > Li3InCl5.4O0.3 > Li3InCl5.4S0.3 > Li3InCl5.4Se0.6 > Li3InCl5.4S0.6. In conclusion, addition of mixed anion to the chloride-based solid electrolytes causes negative effects for the lithium-ion conduction. From these results, it is considered that if a divalent anion is dissolved in a crystal constituting a sublattice by the monovalent anion, an increase in Coulomb interaction has a greater effect on lithium-ion conductivity than an action due to polarizability, decreasing conductivity.[1] R. Murugan, V. Thangadurai, W. Weppner, Angew. Chem 46, 7778(2007)[2] N. Kamaya, K. Homma, Y. Yamakawa, M. Hirayama, R. Kanno, M. Yonemura, T. Kamiyama, Y. Kato, S. Hama, K. Kawamoto, A. Mitsui, Nature Materials 10, 686(2011)[3] T. Asano, A. Sakai, S. Ouchi, M. Sakaida, A. Miyazaki, S. Hasegawa, Adv. Mater. 30, 1803075(2018)[4] X. L, J. Liang, J. Luo, M. N. Banis, C. Wang, W. Li, S. Deng, C. Yu, F. Zhao, Y. Hu, T. Sham, L. Zhang, S. Zhao, S. Lu, H. Huang, R. Li, K. R. Adair, X. Sun, Energy Environ. Sci. 12, 2665(2019)

Study of solid polyurethane electrolytes synthesized from HDI and PEO of different molecular weight

The development of solid polymer electrolyte (SPE) is important for the fabrication of safe and high performance lithium ion battery of the next generation. A series of polyurethanes (PUs) based SPEs synthesized from hexamethylene diisocyanate (HDI) and poly(ethylene glycol)s (PEGs) of varying molecular weight (MW = 300 ~ 1500 corresponding to PU03 ~ PU15) via one-step approach are investigated for the conductivity of lithium ion and other electrochemical properties. These synthetic PUs exhibit semi-crystalline structures when the MW of PEG is higher than 300, and turn into amorphous after the addition of LiClO4. The ionic conductivity decreases with the increasing concentration of LiClO4. The highest lithium ion conductivity was found to be 3.42 × 10−5 S/cm for PU15 with 10 wt% LiClO4 at 50 °C. However, its lithium ion transference number is low by 0.15. All of the PU-based SPEs containing 10 wt% LiClO4 are electrochemically stable up to 4.2 ~ 4.5 V versus Li+/Li, and show very good cycling stability in charge/discharge experiments. In the assembled battery with LiFePO4 as the cathode, PU15 displays higher performances than PU03, indicating good correlation to the molecular weight of PEG.

Lithiophilic 3D VN@N-rGO as a Multifunctional Interlayer for Dendrite-Free and Ultrastable Lithium-Metal Batteries

It is still a big challenge to effectively suppress dendrite growth, which increases the safety and life of lithium-metal-based high energy/power density batteries. To address such issues, herein we design and fabricate a lithiophilic VN@N-rGO as a multifunctional layer on commercial polypropylene (PP) separator, which is constructed by a thin N-rGO nanosheet-wrapped VN nanosphere with a uniform pore distribution, relatively high lithium ionic conductivity, excellent electrolyte wettability, additional lithium-ion diffusion pathways, high mechanical strength, and reliable thermal stability, which are beneficial to regulate the interfacial lithium ionic flux, resulting in the formation of a stable and homogeneous current density distribution on Li-metal electrodes and hard modified separators that can resist dendrites piercing. Consequently, the growth of Li dendrite is effectively suppressed, and the cycle stability of lithium-metal batteries is significantly improved. In addition, even at a high current density of 10 mA cm-2 and cutoff areal capacity of 5 mAh cm-2, the Li|Li symmetric batteries with VN@N-rGO/PP separators still work very well even over 2500 h, exhibiting ultrahigh cycling stability. This work presents rational design ideas and a facile fabrication strategy of a lithiophilic 3D porous multifunctional interlayer for dendrite-free and ultrastable lithium-metal-based batteries.

All-Solid-State Lithium-Ion Batteries with Oxide/Sulfide Composite Electrolytes.

Li6.3La3Zr1.65W0.35O12 (LLZO)-Li6PS5Cl (LPSC) composite electrolytes and all-solid-state cells containing LLZO-LPSC were fabricated by cold pressing at room temperature. The LPSC:LLZO ratio was varied, and the microstructure, ionic conductivity, and electrochemical performance of the corresponding composite electrolytes were investigated; the ionic conductivity of the composite electrolytes was three or four orders of magnitude higher than that of LLZO. The high conductivity of the composite electrolytes was attributed to the enhanced relative density and the rule of mixture for soft LPSC particles with high lithium-ion conductivity (~10−4 S·cm−1). The specific capacities of all-solid-state cells (ASSCs) consisting of a LiNi0.8Co0.1Mn0.1O2 (NCM811) cathode and the composite electrolytes of LLZO:LPSC = 7:3 and 6:4 were 163 and 167 mAh·g−1, respectively, at 0.1 C and room temperature. Moreover, the charge–discharge curves of the ASSCs with the composite electrolytes revealed that a good interfacial contact was successfully formed between the NCM811 cathode and the LLZO-LPSC composite electrolyte.

Mechanochemical synthesis of Li2OHI with enhanced lithium ionic conductivity

Lithium hydroxide halides, as a family of lithium-ion conductive materials, have a promising potential on the application of solid state electrolytes. In this work, we have synthesized orthohombic Li2OHI through a facile mechanochemical method. The obtained sample exhibits a higher lithium-ion conductivity than solid sintering, which can be attributed to the high purity and crystallinity obtained from ball milling. Ball milling can avoid the phase segregation of Li2OHI at high temperature and promote the sufficient eutectic reaction of binary system, which can be widely used in the synthesis of other materials with low melting points.