Properties Of Solid Electrolytes Research Articles

Role of grain-level chemo-mechanics in composite cathode degradation of solid-state lithium batteries

Solid-state Li-ion batteries, based on Ni-rich oxide cathodes and Li-metal anodes, can theoretically reach a high specific energy of 393 Wh kg−1 and hold promise for electrochemical storage. However, Li intercalation-induced dimensional changes can lead to crystal defect formation in these cathodes, and contact mechanics problems between cathode and solid electrolyte. Understanding the interplay between cathode microstructure, operating conditions, micromechanics of battery materials, and capacity decay remains a challenge. Here, we present a microstructure-sensitive chemo-mechanical model to study the impact of grain-level chemo-mechanics on the degradation of composite cathodes. We reveal that crystalline anisotropy, state-of-charge-dependent Li diffusion rates, and lattice dimension changes drive dislocation formation in cathodes and contact loss at the cathode/electrolyte interface. These dislocations induce large lattice strain and trigger oxygen loss and structural degradation preferentially near the surface area of cathode particles. Moreover, contact loss is caused by the micromechanics resulting from the crystalline anisotropy of cathodes and the mechanical properties of solid electrolytes, not just operating conditions. These findings highlight the significance of grain-level cathode microstructures in causing cracking, formation of crystal defects, and chemo-mechanical degradation of solid-state batteries.

Investigating stacking variations in Li3InCl6 crystal structure and their influence on solid electrolyte properties

Li3InCl6 (LIC) has recently emerged as a promising halide-based solid electrolyte for all-solid-state Li batteries. This study investigates the structural characteristics of LIC, with a specific focus on potential stacking faults and their impact on the properties of the solid electrolyte. A thermodynamic assessment of crystallographic stacking structures, conducted via first-principles calculations, reveals that certain variations in stacking sequences in the [010] direction relative to the previously reported reference LIC structure result in reduced crystal energy, which implies a thermodynamically more favorable new crystal structure for LIC than the extant reference structure. The efficacy of this novel crystal structure, referred to as #7–8, is evaluated against the reference structure concerning Li-ion mobility and electrochemical stability. The results demonstrate a notable enhancement in ionic conductivity while preserving a comparable electrochemical stability window. Modifications in specific stacking configurations within LIC crystals are shown to enhance Li-ion conductivity by establishing low-energy barrier pathways for Li ions in particular directions. While the mobility in other directions may decrease, this result in an overall improvement in Li-ion conductivity. The proposed crystal structure demonstrates superior thermodynamic stability compared to the conventional reference structure and is consistent with experimentally obtained X-ray diffraction data, underscoring its potential as a novel benchmark for future analyses of LIC crystal structures. Furthermore, this study suggests that two-dimensional defects, such as stacking faults, may play a crucial role in influencing the performance of halide-based solid electrolytes.

Machine Learning-Accelerated First-Principles Study of Atomic Configuration and Ionic Diffusion in Li10GeP2S12 Solid Electrolyte.

The solid electrolyte Li10GeP2S12 (LGPS) plays a crucial role in the development of all-solid-state batteries and has been widely studied both experimentally and theoretically. The properties of solid electrolytes, such as thermodynamic stability, conductivity, band gap, and more, are closely related to their ground-state structures. However, the presence of site-disordered co-occupancy of Ge/P and defective fractional occupancy of lithium ions results in an exceptionally large number of possible atomic configurations (structures). Currently, the electrostatic energy criterion is widely used to screen favorable candidates and reduce computational costs in first-principles calculations. In this study, we employ the machine learning- and active-learning-based LAsou method, in combination with first-principles calculations, to efficiently predict the most stable configuration of LGPS as reported in the literature. Then, we investigate the diffusion properties of Li ions within the temperature range of 500-900 K using ab initio molecular dynamics. The results demonstrate that the atomic configurations with different skeletons and Li ion distributions significantly affect the Li ions' diffusion. Moreover, the results also suggest that the LAsou method is valuable for refining experimental crystal structures, accelerating theoretical calculations, and facilitating the design of new solid electrolyte materials in the future.

Polycaprolactone-Li6PS5Cl composite polymer electrolytes for stable room temperature all-solid-state lithium batteries

Incorporating inorganic fillers into solid polymer electrolytes (SPEs) to construct composite polymer electrolytes (CPEs) serves as an effective strategy to comprehensively enhance the properties of solid electrolytes. Herein, a CPE is fabricated by integrating Li6PS5Cl particles into polycaprolactone (PCL). The addition of active fillers could effectively weaken the crystallization of polymer and increase the ionic conductivity of the solid electrolyte. In particular, the PCL-based polymer electrolyte with 3% Li6PS5Cl (PCL-3) exhibits an excellent ionic conductivity of 1.36×10−4 S cm−1 at room temperature, which is one order higher than that of PCL polymer solid electrolyte. And it achieves a high critical current density of 2.2 mA cm−2 with a capacity of 2.2 mAh cm−2. The assembled Li symmetric battery can cycle steadily for more than 3000 h at 0.5 mA cm−2 under room temperature. The LiFePO4/PCL-3/Li all-solid-state battery maintains a capacity of 125.3 mAh g−1 after 400 cycles at 0.2 C under room temperature. Notably, the LiFePO4//Li battery also shows stable cycling at 40 °C, exhibiting high reversible specific capacities of 156.7 mAh g−1 and 126.3 mAh g−1 with a retention rate of 97.15% and 94.6% at 0.2 C and 0.5 C after 100 cycles, respectively, showing promising application prospects for all-solid-state lithium metal batteries.

Effects of Grain Boundaries and Surfaces on Electronic and Mechanical Properties of Solid Electrolytes

AbstractExtended defects, including exposed surfaces and grain boundaries (GBs), are critical to the properties of polycrystalline solid electrolytes in all‐solid‐state batteries (ASSBs). These defects can alter the mechanical and electronic properties of solid electrolytes, with direct manifestations in the performance of ASSBs. Here, by building a library of 590 surfaces and grain boundaries of 11 relevant solid electrolytes—including halides, oxides, and sulfides— their electronic, mechanical, and thermodynamic characteristics are linked to the functional properties of polycrystalline solid electrolytes. It is found that the energy required to mechanically “separate” grain boundaries can be significantly lower than in the bulk region of materials, which can trigger preferential cracking of solid electrolyte particles in the grain boundary regions. The brittleness of ceramic solid electrolytes, inferred from the predicted low fracture toughness at the grain boundaries, contributes to their cracking under local pressure imparted by lithium (sodium) penetration in the grain boundaries. Extended defects of solid electrolytes introduce new electronic interfacial states within bandgaps of solid electrolytes. These states alter and possibly increase locally the availability of free electrons and holes in solid electrolytes. Factoring effects arising from extended defects appear crucial to explain electrochemical and mechanical observations in ASSBs.

Li8P2S9 solid electrolyte with high ionic conductivity and air stability by Bi2Se3 co-doping

Excellent ionic conductivity and electronic insulation are core properties of solid electrolytes. In this study, we use high-energy ball milling and high-temperature sintering heat treatment to prepare a solid electrolyte, and its ionic conductivity (1.57 × 10−4 S⋅cm−1) is comparable with that of Li8P2S9 in the glass–ceramic state. On this basis, we modify the prepared LPS solid-state electrolyte through Bi2Se3 doping. First-principles computations based on density functional theory (DFT) indicate that Bi2Se3 doping can broaden lithium-ion transport channels and increase the lithium-ion conduction rate. With a doping ratio of 4 %, the ion conductivity reaches 3.02 × 10−3 S⋅cm−1, which offers good insulation to electrons and a stable −0.5 to 5 V (vs. Li/Li+) high-voltage platform. Additionally, Bi2Se3 doping significantly improved the air stability of the LPS solid electrolyte, reducing its adsorption energy to water and preventing the replacement of S by O from H2O.

Recent advances in MXene-based nanomaterials as hosts for high-performance lithium metal anodes and as additives for improving the properties of solid electrolytes

Recent advances in MXene-based nanomaterials as hosts for high-performance lithium metal anodes and as additives for improving the properties of solid electrolytes

Functionalized Thiophosphate and Oxidic Filler Particles for Hybrid Solid Electrolytes

AbstractTo achieve the commercialization of solid‐state‐batteries (SSBs), solid electrolyte properties need to be further improved. The hybrid solid electrolyte (HSE) approach is expected to combine the favorable properties of different solid electrolyte classes and is therefore systematically investigated. Mixing low amounts of thiophosphate or oxide filler particles (FP) into a polyethylene oxide (PEO) polyethylene glycol (PEG) and lithium salt bis(trifluoromethane)sulfonimide (LiTFSI) matrix cannot improve the electrochemical properties. Silanization of the thiophosphate FPs significantly increases the ionic conductivity to 0.1 mS cm−1 at room temperature compared to 0.017 mS cm−1 for a pure PEO solid electrolyte. Moreover, a correlation between the intrinsic conductivity of the FPs and the resulting conductivity of the HSE is observed. Also, the functionalization is successfully transferred to oxide FPs. In addition to an equally significant increase in ionic conductivity, a strong influence of the crystallite size of the FPs on the resulting ionic conductivity of the HSE was found. The discovered effect of FP surface structure on overall HSE conductivity indicates a participation of the FP surface in ion transport and emphasizes the need for tailored filler design in HSE applications.

Recent advances in Mxene-based nanomaterials as hosts for high-performance lithium metal anodes and as additives for improving the properties of solid electrolytes

To tackle the issues of rapid electrode degradation and severe safety issues caused by the uncontrollable growth of lithium dendrites in Li metal anodes (LMAs), two-dimensional transition metal carbides/nitrides (MXenes) with a high electrical conductivity, excellent mechanical properties, and abundant surface functional groups have been used as hosts to induce uniform Li nucleation and alleviate the volume changes, eventually inhibiting the formation of Li dendrites. Recent advances in the use of MXene-based nanomaterials in LMAs are summarized. The problems with using LMAs are first considered, and the ways of using MXene-based nanomaterials for suppressing Li dendrite growth and constructing stable LMAs are then summarized. These include the use of MXenes, MXene-metal hybrids, MXene-carbon hybrids, and MXene derivatives as hosts for the anodes and as additives to modify the electrolyte compositions to increase ionic conductivity and inhibit polymer crystallization. Finally, the challenges and prospects for using MXene-based nanomaterials in next-generation LMAs are briefly discussed.

Effect of various doping on electrochemical properties of KNbO3 proton conductor

KNbO3 and KNb0.9M0.1O3-α (M = Ti, Hf, Zr, Sc, In, Yb) were prepared by solid state reaction at 920 °C for 4 h and characterized by X-ray diffraction. The electrical properties of solid electrolytes were measured by AC impedance in wet air, wet Ar and dry Ar. The order of conductivity in different atmospheres is σ(wet air)>σ(wet Ar)>σ(dry Ar). Among KNb0.9M0.1O3-α (M = Ti, Hf, Zr, Sc, In, Yb), KNb0.9In0.1O3-α displays the highest conductivity. The carriers transport numbers of each material were measured by concentration cell method. The results show KNb0.9In0.1O3-α is almost a pure proton conductor below 625 °C. KNb0.9In0.1O3-α has excellent chemical stability against CO2 and H2O, but in the process of use should avoid rapid heating and cooling.

Solid Hybrid Electrolyte Featuring a Vertically Aligned Li6.4La3.0Zr1.4Ta0.6O12 Membrane for All-Solid-State Lithium Batteries.

All-solid-state lithium batteries (ASSLBs) with enhanced safety are considered one of the most promising substitutes for liquid electrolyte-based Li-ion batteries. However, many properties of solid electrolytes, such as ionic conductivity, film formability, and electrochemical, mechanical, thermal, and interfacial stability need to be improved for their practical application. In this study, a vertically aligned Li6.4La3.0Zr1.4Ta0.6O12 (LLZO) membrane with finger-like microvoids was prepared using processes involving phase inversion and sintering. A hybrid electrolyte was then obtained by infusing the LLZO membrane with a solid polymer electrolyte based on poly(ε-caprolactone). The solid hybrid electrolyte (SHE) was a flexible thin film with high ionic conductivity, superior electrochemical stability, high Li+ transference number, enhanced thermal stability, and improved Li metal electrode-solid electrolyte interfacial stability. A solid-state Li/LiNi0.78Co0.10Mn0.12O2 cell assembled with the hybrid electrolyte exhibited good cycling performance, in terms of discharge capacity, cycling stability, and rate capability. Accordingly, the SHE using a vertically aligned LLZO membrane is a promising solid electrolyte for realizing safe, high-performance ASSLBs.

Tunable all-solid-state wire-shaped high power device based on carbon nanotubes yarn

Energy storage devices integrated into textiles have emerged as a significant strategy for electronic applications. In this context, in the present paper novel flexible devices were developed, in which the control of both the electrode characteristics and the solid-electrolyte properties allows to build all-solid-state wire-shaped supercapacitors that can be integrated and waved. The proposed device was assembled using modified CNT yarns as electrodes and a blend of ionic liquid, Li salt and poly(ethylene glycol) acrylate to fabricate the solid-polymeric electrolyte. Excellent performance in terms of both electrochemical parameters and stability were obtained. These achievements are possible thanks to the coupling of asymmetric CNT yarns, following an optimization of the activation procedure together with the improvement of the polymeric electrolyte. The results show a capacitance as high as 1.8 mF/cm, energy density of 1.3 μWh/cm and a capacitance retention higher than 100% over 1200 cycles.

Mechanochemical synthesis, microstructure and electrochemical properties of solid electrolytes with stabilized fluorite-type structure in the PbF2-SrF2-KF system for solid-state fluoride-ion batteries

Solid solutions with fluorite-type structure in the PbF2-SrF2-KF system were prepared by mechanochemical synthesis. The structure and morphology of the synthesized materials were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and high-resolution transmission electron microscopy (HRTEM). Thermal analysis of samples confirmed the absence of phase transitions which are characteristic of PbF2. Temperature dependence of the ionic conductivity of the solid electrolytes in the PbF2-SrF2-KF system was investigated by impedance spectroscopy. The high ionic conductivity of the Pb0.75Sr0.20K0.05F1.95 sample (3.05 × 10−4 S/cm at 20 °C) made it possible to create a fluoride-ion battery model on its basis. The cell operation demonstrates the possibility of using the Pb0.75Sr0.2K0.05F1.95 solid electrolyte in solid-state fluoride-ion batteries (FIBs).

Towards advanced lithium metal solid-state batteries: Durable and safe multilayer pouch cell enabled by a nanocomposite solid electrolyte

Lithium metal solid-state batteries (SSBs) are expected to outperform the current lithium-ion battery technology, limited by the performance, energy density, and safety issues. One of the most promising classes of solid electrolytes for SSBs are polymer-inorganic composites. However, incompatibility between inorganic and polymer phases may affect the solid electrolyte properties and, therefore, the SSB performance. Therefore, in this study, novel nanocomposite solid polymer electrolytes (nCSPE), containing inert alumina nanoparticles with specially customized interface, are successfully synthesized. Thermal, mechanical, electrical and electrochemical properties of the prepared nCSPEs are evaluated to select the most promising solid electrolyte formulation for its further scale-up. Afterwards, multilayer solid state pouch-type cells with a nominal capacity of ca. 0.5 Ah are successfully prepared, using the developed nCSPE, current-collector-free thin Li metal anode, and double-sided composite LiFePO4 cathode. “Li/nCSPE/LiFePO4” prototype pouch cells are cycled at 60 °C, exhibiting long cycle life with more than 2000 cycles with a high coulombic efficiency, and enhanced safety in the fully charged state. This research could contribute to promising advances on the development of new generation of high performant and safe Li metal SSBs.

Investigation of Structure, Ionic Conductivity, and Electrochemical Stability of Halogen Substitution in Solid-State Ion Conductor Li3YBr x Cl6-x.

Li3YX6 (X = Cl, Br) materials are Li-ion conductors that can be used as solid electrolytes in all solid-state batteries. Solid electrolytes ideally have high ionic conductivity and (electro)chemical compatibility with the electrodes. It was proven that introducing Br to Li3YCl6 increases ionic conductivity but, according to thermodynamic calculations, should also reduce oxidative stability. In this paper, the trade-off between ionic conductivity and electrochemical stability in Li3YBr x Cl6-x halogen-substituted compounds is investigated. The compositions of Li3YBr1.5Cl4.5 and Li3YBr4.5Cl1.5 are reported for the first time, along with a consistent analysis of the whole Li3YBr x Cl6-x (x = 0-6) tie-line. The results show that, while Br-rich materials are more conductive (5.36 × 10-3 S/cm at 30 °C for x = 4.5), the oxidative stability is lower (∼3 V compared to ∼3.5 V). Small Br content (x = 1.5) does not affect oxidative stability but substantially increases ionic conductivity compared to pristine Li3YCl6 (2.1 compared to 0.049 × 10-3 S/cm at 30 °C). This work highlights that optimization of substitutions in the anion framework provide prolific and rational avenues for tailoring the properties of solid electrolytes.

Effects of B2O3 on crystallization kinetics, microstructure and properties of Li1.5Al0.5Ge1.5(PO4)3-based glass-ceramics

Lithium-ionic conductors of Li1+xAlxGe2-x(PO4)3 family are considered as one of the most attractive solid electrolytes. Li1.5Al0.5Ge1.5(PO4)3 composition obtained by glass-ceramic route exhibits the highest electrical conductivity at room temperature. The introduction of sintering additives makes it possible to modify the properties of solid electrolytes. Glass-ceramics of the Li1.5Al0.5Ge1.5(PO4)3–xB2O3 series (x = 0, 0.05, 0.1, 0.15, 0.2 wt%) was obtained by glass crystallization at optimal conditions of heat treatment. The influence of B2O3 additive on thermal stability and crystallization process of initial glasses was studied by DSC method. The phase composition, microstructure and transport properties of glass-ceramics were investigated by XRD, SEM and impedance spectroscopy, respectively. The structure of the glass-ceramics was characterized by Raman spectroscopy. Glass-ceramics was found to be single-phase (R-3c) when 0 ≤ x ≤ 0.15, but impurity phases Li4P2O7 and AlPO4 appear at x = 0.20. The conductivity of B2O3-added solid electrolytes is higher compared to the pristine Li1.5Al0.5Ge1.5(PO4)3. Its ionic conductivity reached 5.5 × 10−4 S cm−1 at 25 °C. The obtained glass-ceramic electrolytes are promising for use in all-solid-state lithium-ion batteries.

On the possibility of technosphere safety by superionic

The purpose of this article is an attempt to substantiate the possibility of using a new technology for cleaning the industrial atmosphere in a separate workshop of the Taldykorgan battery plant "Kainar AKB", which produces, in particular, powerful batteries for K–700 tractors for agriculture. The innovative technology of air purification proposed by us in the technosphere of the manufacture of batteries for the agricultural production complex is based on the use of transport ion-conducting properties of solid electrolytes made of stabilized zirconium dioxide. The traditional methods of industrial atmosphere purification in enterprises and factories known to us, in our opinion, are morally outdated in terms of bulky external dimensions, noise generation, and need for systematic maintenance. The installation developed by us from a superionic conductor is devoid of these disadvantages, it is low-inertia, does not create a noise effect, compact and small-sized. Our ion conducting solid electrolyte is a ceramic material in the form of pipes, test tubes, tablets, initially containing impurity cations of lower valence, such as calcium, yttrium, scandium, in comparison with zirconium. Actually, these impurity cations create the presence of vacancies or holes in the solid cubic structure of zirconium dioxide. Only oxygen anions will be transported through these vacancies under the effect of external factors, high temperature, and DC electric field. The research method is based on the measurement of the electromotive force, which is recorded at the boundary section: air/superionic/air, which is uniquely mathematically related to oxygen concentration in air stream.

Electrochemical Approaches for Reviving Solid-State Batteries

Garnets are a promising solid electrolyte family due to high mechanical strength, ionic conductivity, wide electrochemical stability window, and processability. However, dendrite formation, physical contact loss, cathode interphase formation, and limited ion conduction pathways in cathode during cycling are challenges that need to be addressed for long-term and safe operation of garnet-based All-Solid-State batteries(ASSB) [1]. Interfacial inhomogeneities, irregular electrodeposition and electrodissolution of Li-metal, heterogenous current distribution at the interface, interfacial defects, stress concentration, diffusion limitation of Li and lower dynamic properties of solid electrolytes are amongst the main reasons identified for dendrite formation and physical contact loss [2]. Significant efforts are reported in the literature to suppress dendrite formation and ensuring interface contact via interfacial coatings, SE material modifications, and modified operating conditions all of which either increases system complexity or cost of ASSB operation [3]. Additionally, these solutions have been investigated for lower current densities compared to what will be ideally required to operate a full ASSB (1C – 10C). Higher current density will lead to inhomogeneity in current distribution and pore generation leading to dendrite formation and cell failure. In this work, we demonstrate several non-destructive electrochemical strategies for the removal of Li-dendrites and ensuring physical contact at Li | LALZO interface during long-term cycling [4]. The initial results on symmetric cells indicate that dendrite can be completely removed from the bulk of solid electrolytes at lower current densities. The combination of various current ranges with specific cut-off voltages leads to better interfacial contact at Li | LALZO interface. Similar electrochemical strategies are being investigated for full ASSBs with Li | LALZO | LFP configuration at various temperatures and pressure ranges. The obtained results illustrate that the battery cells can be repaired, improved, and rescued from the failure mode and enable longer life. Hatzell et al., ACS Energy Lett. 2020, 5, 3, 922–934.Lewis et. al., Trends in Chemistry, 2019, 1, 9, 845-857.Xiao et. al., Nature Reviews Materials, 2020, 5, 105–126.Parejiya et. al., ACS Energy Lett. 2020, 5, 11, 3368–3373 Figure 1

Nanostructured zeolitic imidazolate framework-67 reinforced poly(ethylene oxide) composite electrolytes for all solid state Lithium ion batteries

Composite polymer electrolyte is a promising solid electrolyte for all solid state lithium ion batteries (ASSLIBs) due to its reliable safety, high ionic conductivity and excellent flexibility. Here, the uniform rhomboid dodecahedron structured zeolitic imidazolate framework-67 (ZIF-67) with high specific surface area and abundant nano-pores have been prepared by adjusting the synthetic solvent, which are subsequently incorporated into poly(ethylene oxide) (PEO) matrixes to form solid composite electrolyte (SCE). ZIF-67 MOFs can reduce the crystallinity of PEO matrixes, coordinate with C-O-C bonds of PEO and improve the mechanical properties of solid electrolyte. Additionally, abundant pore structure of ZIF-67 can endow its ability to absorb anions. The optimized SCE shows high ionic conductivities of 1.51 × 10−5 S/cm at 25 °C, wide electrochemical stable window of around 5.2 V and good interfacial compatibility with lithium. Furthermore, LiFePO4/Li ASSLIB exhibits high electrochemical performances. At current rates of 0.2 C, 0.5 C, 1 C and 2 C, the battery has specific discharging capacities of 155.13, 153.77, 148.83 and 139.90 mAh·g−1, respectively, and it demonstrates high capacity retention of 90.17% after 100 cycles at 0.5 C. Therefore, it is concluded that ZIF-67/PEO SCE is a good solid electrolyte candidate for ASSLIB.

Quantifying the Density and Mobility of Mobile Ions in Solid Electrolytes By Transient Current Measurements

Solid electrolytes are a key component in enabling new technological advances for rechargeable batteries by mitigating many of the challenges associated with the use of liquid organic electrolytes. One of the key properties of solid electrolytes is their ability to transport ions between the anode and the cathode. This ion migration is usually characterized by measuring the ionic conductivity by means of impedance spectroscopic measurements. However, the ionic conductivity is proportional to both the density and the mobility of mobile ions. Only the mobility represents the actual velocity of the mobile ions.Using lithium phosphorus oxynitride (LiPON), we show how measuring the temperature-dependent current transients can be used to independently quantify both the mobility and the density of mobile ions in solid electrolytes. By changing the mobile ion density in Li7La3Zr2O12 (LLZO) solid electrolyte by co-sputtering LLZO and Li2O, we show how samples that seem to have the same ionic conductivity can still differ in ionic mobility. Finally, we employ this method to quantify the effects of Al and Ga doping on the ion migration in LLZO solid electrolytes. The proposed approach in quantification of mobile ions can be extended to other solid electrolytes for a better understanding of ion migration and the influence on battery performance.