Application Of Solid-state Electrolytes Research Articles

O2− substituted Li-richened Li2ZrCl6 lattice towards superionic conductivity

Emerging halide superionic conductors with remarkable oxidative stability and deformability, making them a potential game-changer for high-performance all-solid-state Li batteries (ASSLBs). The recently reported Li2ZrCl6 (LZC) with low cost possess great potential. However, its ionic conductivity at 25 °C is below 1 mS cm−1. Herein, we developed a Li-richened strategy to LZC by doping O2− at Cl− site via a mechanochemical method to form oxychloride electrolytes Li2+xZrCl6−xOx (0 ≤ x ≤ 1.8), resulting in high ionic conductivity up to 1.46 mS cm−1 at room temperature (RT). The experimental results and theoretical calculations (ab initio molecular dynamics simulations) demonstrate that the Li2O doping leading to a Li-richened LZC lattice effectively enhances the Li+ conductivity in solid-state electrolytes (SSEs). Significantly, an increasing O2− substitution in the Li2+xZrCl6−xOx microcrystalline framework induces a progressive structural evolution from triangular to monoclinic phases, accompanied by a redistribution of Li+. Furthermore, the ASSLBs formed by Li3.4ZrCl4.6O1.4 (LZCO) with Li-In anode and bare LiCoO2 cathode shows excellent long-term cycling stability (94 % capacity retention for 600 cycles at 1 C) and high-rate performance (105.7 mAh g−1 at 2 C). This exploratory study provides a promising strategy to facilitate the application of low-cost LZC-based SSEs for high-performance ASSLBs.

A Universal Self-Propagating Synthesis of Aluminum-Based Oxyhalide Solid-State Electrolytes.

Inorganic solid-state electrolytes (SSEs) play a vital role in high-energy all-solid-state batteries (ASSBs). However, the current method of SSE preparation usually involves high-energy mechanical ball milling and/or a high-temperature annealing process, which is not suitable for practical application. Here, a facile strategy is developed to realize the scalable synthesis of cost-effective aluminum-based oxyhalide SSEs, which involves a self-propagating method by the exothermic reaction of the raw materials. This strategy enables the synthesis of various aluminum-based oxyhalide SSEs with tunable components and high ionic conductivities (over 10-3 S cm-1 at 25 °C) for different cations (Li+, Na+, Ag+). It is elucidated that the amorphous matrix, which mainly consists of various oxidized chloroaluminate species that provide numerous sites for smooth ion migration, is actually the key factor for the achieved high conductivities. The application of these aluminum-based oxyhalide SSEs synthesized by our approach further pushes forward their practical application considering their easy synthesis, low cost, and low weight that ensures high-energy-density ASSBs.

Solid Electrolyte Bimodal Grain Structures for Improved Cycling Performance.

The application of solid-state electrolytes in Li batteries is hampered by the occurrence of Li-dendrite-caused short circuits. To avoid cell failure, the electrolytes can only be stressed with rather low current densities, severely restricting their performance. As grain size and pore distributions significantly affect dendrite growth in ceramic electrolytes such as Li7 La3 Zr2 O12 and its variants; here, a "detour and buffer" strategy to bring the superiority of both coarse and fine grains into play, is proposed. To validate the mechanism, a coarse/fine bimodal grain microstructure is obtained by seeding unpulverized large particles in the green body. The rearrangement of coarse grains and fine pores is fine-tuned by changing the ratio of pulverized and unpulverized powders. The optimized bimodal microstructure, obtained when the two powders are equally mixed, allows, without extra interface decoration, cycling for over 2000h as the current density is increased from 1.0 mA·cm-2 , and gradually, up to 2.0 mA·cm-2 . The "detour and buffer" effects are confirmed from postmortem analysis. The complex grain boundaries formed by fine grains discourage the direct infiltration of Li. Simultaneously, the coarse grains further increase the tortuosity of the Li path. This study sheds light on the microstructure optimization for the polycrystalline solid-state electrolytes.

Solid-State Electrolytes and Electrode/Electrolyte Interfaces in Rechargeable Batteries.

Solid-state batteries (SSBs) are considered to be one of the most promising candidates for next-generation energy storage systems due to the high safety, high energy density and wide operating temperature range of solid-state electrolytes (SSEs) they use. Unfortunately, the practical application of SSEs has rarely been successful, which is largely attributed to the low chemical stability and ionic conductivity, ineluctable solid-solid interface issues including limited ion transport channels, high energy barriers, and poor interface contact. A comprehensive understanding of ion transport mechanisms of various SSEs, interactions between fillers and polymer matrixes and the role of the interface in SSBs are indispensable for rational design and performance optimization of novel electrolytes. The categories, research advances and ion transport mechanism of inorganic glass/ceramic electrolytes, polymer-based electrolytes and corresponding composite electrolytes are detailly summarized and discussed. Moreover, interface contact and compatibility between electrolyte and cathode/anode are also briefly discussed. Furthermore, the electrochemical characterization methods of SSEs used in different types of SSBs are also introduced. On this basis, the principles and prospects of novel SSEs and interface design are curtly proposed according to the development requirements of SSBs. Moreover, the advanced characterizations for real-time monitoring of interface changes are also brought forward to promote the development of SSBs.

Moss-like Hierarchical Architecture Self-Assembled by Ultrathin Na2Ti3O7 Nanotubes: Synthesis, Electrical Conductivity, and Electrochemical Performance in Sodium-Ion Batteries.

Nanocrystalline layer-structured monoclinic Na2Ti3O7 is currently under consideration for usage in solid state electrolyte applications or electrochemical devices, including sodium-ion batteries, fuel cells, and sensors. Herein, a facile one-pot hydrothermal synthetic procedure is developed to prepare self-assembled moss-like hierarchical porous structure constructed by ultrathin Na2Ti3O7 nanotubes with an outer diameter of 6–9 nm, a wall thickness of 2–3 nm, and a length of several hundred nanometers. The phase and chemical transformations, optoelectronic, conductive, and electrochemical properties of as-prepared hierarchically-organized Na2Ti3O7 nanotubes have been studied. It is established that the obtained substance possesses an electrical conductivity of 3.34 × 10−4 S/cm at room temperature allowing faster motion of charge carriers. Besides, the unique hierarchical Na2Ti3O7 architecture exhibits promising cycling and rate performance as an anode material for sodium-ion batteries. In particular, after 50 charge/discharge cycles at the current loads of 50, 150, 350, and 800 mA/g, the reversible capacities of about 145, 120, 100, and 80 mA∙h/g, respectively, were achieved. Upon prolonged cycling at 350 mA/g, the capacity of approximately 95 mA∙h/g at the 200th cycle was observed with a Coulombic efficiency of almost 100% showing the retention as high as 95.0% initial storage. At last, it is found that residual water in the un-annealed nanotubular Na2Ti3O7 affects its electrochemical properties.

Scalable synthesis of hydroxyl-functionalized boron nanosheets for high ion-conductive solid-state electrolyte applications.

A hydroxyl-functionalized boron nanosheet is developed as the filler material for the solid-state electrolyte (SSE) of lithium batteries. The nanosheet exhibits good oxidation resistance and thermal stability. Its composite SSE shows high ionic conductivity, and the resulting batteries present much enhanced capacities, rate capability and cycling performance, proving the electrochemical advances of the boron nanosheet.

A novel coral-like garnet for high-performance PEO-based all solid-state batteries

As one of the most promising next-generation energy storage devices, the lithium-metal battery has been extensively investigated. However, safety issues and undesired lithium dendrite growth hinder its development. The application of solid-state electrolytes has attracted increasing attention as they can solve safety issues and show great potential to inhibit the growth of lithium dendrites. Polyethylene oxide (PEO)-based electrolytes are very promising due to their enhanced safety and excellent flexibility. However, they suffer from low ionic conductivity at room temperature and cannot effectively inhibit lithium dendrites at high temperatures due to the intrinsic semicrystalline properties and poor mechanical strength. In this work, a novel coral-like Li6.25Al0.25La3Zr2-O12 (C-LALZO) is synthesized to serve as an active ceramic filler in PEO. The PEO with LALZO coral (PLC) exhibits increased ionic conductivity and mechanical strength, which leads to uniform deposition/stripping of lithium metal. The Li symmetric cells with PLC do not cause a short circuit after cycling for 1500 h at 60°C. The assembled LiFePO4/PLC/Li batteries display excellent cycling stability at both 60 and 50°C. This work reveals that the electrochemical properties of the composite electrolyte can be effectively improved by tuning the microstructure of the filler, such as the C-LALZO architecture.

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.

Metal Halide Superionic Conductors for All-Solid-State Batteries.

ConspectusRechargeable all-solid-state Li batteries (ASSLBs) are considered to be the next generation of electrochemical energy storage systems. The development of solid-state electrolytes (SSEs), which are key materials for ASSLBs, is therefore one of the most important subjects in modern energy storage chemistry. Various types of electrolytes such as polymer-, oxide-, and sulfide-based SSEs have been developed to date and the discovery of new superionic conductors is still ongoing. Metal-halide SSEs (Li-M-X, where M is a metal element and X is a halogen) are emerging as new candidates with a number of attractive properties and advantages such as wide electrochemical stability windows (0.36-6.71 V vs Li/Li+) and better chemical stability toward cathode materials compared to other SSEs. Furthermore, some of the metal-halide SSEs (such as the Li3InCl6 developed by our group) can be directly synthesized at large scales in a water solvent, removing the need for special apparatus or handling in an inert atmosphere. Based on the recent advances, herein we focus on the topic of metal-halide SSEs, aiming to provide a guidance toward further development of novel halide SSEs and push them forward to meet the multiple requirements of energy storage devices.In this Account, we describe our recent progress in developing metal halide SSEs and focus on some newly reported findings based on state-of-the-art publications on this topic. A discussion on the structure of metal-halide SSEs will be first explored. Subsequently, we will illustrate the effective approaches to enhance the ionic conductivities of metal halide SSEs including the effect of anion sublattice framework, the regulation of site occupation and disorder, and defect engineering. Specifically, we demonstrated that proper structural framework, balanced Li+/vacancy concentration, and reduced blocking effect can promote fast Li+ migration for metal halide SSEs. Moreover, humidity stability and degradation chemistry of metal halide SSEs have been summarized for the first time. Some examples of the application of metal halide SSEs with stability toward humidity have been demonstrated. Direct synthesis of halide SSEs on cathode materials by the water-mediated route has been used to eliminate the interfacial challenges of ASSLBs and has been shown to act as an interfacial modifier for high-performance all-solid-state Li-O2 batteries. Taken together, this Account on metal halide SSEs will provide an insightful perspective over the recent development and future research directions that can lead to advanced electrolytes.

Solid‐State Electrolytes: Progress and Perspective of Solid‐State Lithium–Sulfur Batteries (Adv. Funct. Mater. 38/2018)

Application of solid-state electrolytes is quite significant to enhance the safety and energy density of Li-S batteries. In article number 1707570, Yan-Bing He and co-workers provide an overview of solid-state electrolytes for addressing the major drawbacks of Li-S batteries, including the lithium polysulfides shuttle effect and lithium dendrites growth.

SYNTHESIS AND ELECTROCHEMICAL CHARACTERIZATION OF Li3PO4 FORSOLID STATE ELECTROLYTES

SYNTHESIS AND ELECTROCHEMICAL CHARACTERIZATION OF Li 3 PO 4 FORSOLID STATE ELECTROLYTES . The application of solid state electrolytes to solid state battery becomes important research area, recently, to overcome leakage and combustion issues involved in liquid electrolytes. Solid state electrolytes are safer, easily packaged and have several advantages, including easy fabrication, high ionic conductivity at room temperature and wide compositional range. Here in this study we characterized Li 3 PO 4 for solid state electrolyte, synthesized by solid state reaction and wet chemical reaction methods. The samples were characterized using Electrochemical Impedance Spectrometer (EIS) to determine its electrical properties in addition to X-Ray Diffraction and Scanning Electron Microscope -Energy Dispersive X-Rays Spectroscopy (SEM-EDS) characterizations. Both of samples that have been characterized have a high electrical resistivity on the order of tens MW, with DC conductivity in order of 10-10 to 10 -9 S/cm.

(Invited) Overview on the Application of Solid State Electrolytes in Li-Ion Batteries and Beyond

In recent years, much effort has been pursued in developing solid state electrolytes for Li-ion batteries and beyond. While advances have been made in this field, challenges still exist. A few excellent review papers have been published discussing the mechanism and synthesis of solid state electrolytes with some examples of reducing the interfacial resistances between particles, which provide useful information to understand solid state chemistry underlying the electrolytes. Different from previous overview, this talk will categorize different solid state electrolytes according to their applications including Li-ion batteries, Li-air, Li-S batteries and Li metal protection. Both fundamental science and practical applications will be discussed and the energy density will be projected to compare with state-of-art Li-ion batteries.

Structure of amorphous Ag/Ge/S alloys: experimentally constrained density functional study

Density functional/molecular dynamics simulations have been performed to determine structural and other properties of amorphous Ag/Ge/S and Ge/S alloys. In the former, the calculations have been combined with experimental data (x-ray and neutron diffraction, extended x-ray absorption fine structure). Ag/Ge/As alloys have high ionic conductivity and are among the most promising candidates for future memristor technology. We find excellent agreement between the experimental results and large-scale (500 atoms) simulations in Ag/Ge/S, and we compare and contrast the structures of Ge/S and Ag/Ge/S. The calculated electronic structures, vibrational densities of states, ionic mobilities, and cavity distributions of the amorphous materials are discussed and compared with data on crystalline phases where available. The high mobility of Ag in solid state electrolyte applications is related to the presence of cavities and can occur via jumps to a neighbouring vacant site.

Structure, electronic, and vibrational properties of amorphousAsS2andAgAsS2: Experimentally constrained density functional study

Density functional/molecular dynamics simulations and experimental data (x-ray and neutron diffraction, extended x-ray absorption fine structure) have been combined to determine structural and other properties of amorphous ${\text{AsS}}_{2}$ and $\text{Ag}{\text{AsS}}_{2}$. These semiconductors represent the two small regions of the Ag-As-S ternary diagram where homogeneous glasses form, and they have quite different properties, including ionic conductivities. We find excellent agreement between the experimental results and large-scale (over 500 atoms) simulations, and we compare and contrast the structures of ${\text{AsS}}_{2}$ and $\text{Ag}{\text{AsS}}_{2}$. The calculated electronic structures, vibrational densities of states, ionic mobilities, and cavity distributions of the amorphous materials are discussed and compared with data on crystalline phases where available. The high mobility of Ag in solid state electrolyte applications is coupled to the large cavity volume in ${\text{AsS}}_{2}$ and local modifications of the covalent As-S network in the presence of Ag.