Investigation of cation substitution effect on sulfide and halide solid electrolytes for all-solid-state Li and Na batteries

Crystallography, Ab initio structure determination, Powder X-ray diffraction, Sulfide solid elec-trolytes, halide solid electrolytes, all-solid-state battery, Diffusion mechanismNⅠ. INTRODUCTION 1 Ⅱ. THEORY 12 2.1 Crystallography 12 2.1.1 X-ray diffraction 14 2.1.2 Ab-initio structure determination 16 2.1.3 Unit cell indexing 17 2.1.4 Determination of space group 17 2.1.5 Extraction of Diffraction Intensities from the Powder XRD data 18 2.1.6 Fourier synthesis electron density and phase problem 19 2.1.7 Algorithms for structure solution 20 2.1.8 Difference Fourier synthesis 22 2.1.9 Rietveld refinement 22 2.2 Bond valence sum mapping and Bond valence energy landscape calculation 23 2.2.1 bond valence sum 23 2.2.2 bond valence sum mapping 25 2.2.3 bond valence energy landscape calculation 25 2.3 Electrochemistry 26 2.3.1 Battery basics 26 2.3.2 Impedance spectroscopy 28 2.4 References 29 Ⅲ. Na2ZrCl6 enabling highly stable 3 V all-solid-state Na-ion batteries 31 3.1 Introduction 31 3.2 Experimental 33 3.2.1 Preparation of materials 33 3.2.2 Materials characterization 33 3.2.3 Electrochemical characterization 34 3.3 Results and discussion 35 3.4 Conclusions 39 3.5 References 49 Ⅳ. A New sodium ion-conductor Na4-xSn1-xAsxS4 (0 < x ≤ 0.3) for all-solid-state sodium-ion battery 55 4.1 Introduction 55 4.2 Experimental 57 4.3 Results and discussion 58 4.4 Conclusions 60 4.5 References 72 Ⅴ. Investigation of crystal Structure and ionic conductivity of Zn substituted Li4P2S6 for Li-ion Conductor 76 5.1 Introduction 76 5.2 Experimental 78 5.3 Results and discussion 79 5.4 Conclusions 82 5.5 References 90 Summary (in Korean) 93DoctordCollectio

Enhanced Li-Ion Conductivity and Air Stability of Sb-Substituted Li4GeS4 toward All-Solid-State Li-Ion Batteries

Sulfide inorganic materials have the potential to be used as solid electrolytes (SEs) in Li-ion all-solid-state batteries (ASSBs) owing to their high ionic conductivity and mechanical softness. However, H2S gas release in ambient air is a critical issue for realizing scalable production of these materials. In the present study, we designed aliovalent substitutions of Sb5+ for Ge4+ in Li4GeS4 to produce a series of materials with a general nominal composition of Li4-xGe1-xSbxS4. With increasing Sb substitution up to the solubility limit (x = 0.4), the unit cell expands, the ionic conductivity increases, and the activation energy decreases. Among the series, the material with x = 0.4 displays the highest ionic conductivity, ∼10-4 S cm-1 at 303 K, 2 orders of magnitude higher than that of the unsubstituted Li4GeS4, and the main phase of the material is determined to be Li3.68Ge0.69Sb0.31S4 by the X-ray Rietveld refinement. It also shows high air stability: 70% of the initial ionic conductivity is retained without any structural degradation after exposure to air with a relative humidity of 15% for 70 min at 303 K, in contrast to a control sample of Li3PS4 retaining only 10% of the initial conductivity. A press cell composed of a TiS2 composite cathode, an In-Li alloy anode, and a Li3.68Ge0.69Sb0.31S4 electrolyte showed excellent cycle performance, demonstrating the electrolyte as a dry-air-stable SE candidate for ASSBs. These results provide insights into the synthesis design of air-stable SEs with appropriate compositions and improved performance. © 2023 American Chemical Society.FALS

Zn substituted Li4P2S6 as a solid lithium-ion electrolyte for all-solid-state lithium batteries

Li-ion conductors are pivotal materials for all-solid-state Li batteries requiring high energy densities and operational safety. PS4-based thio-phosphate materials have been intensively investigated as solid electrolytes; however, studies on more stable P2S6-based materials are scarce. We herein report on the application of Zn-substituted Li4P2S6, Li4−2xZnxP2S6, as a Li-ion conductor. Owing to the slightly smaller ionic radius of Zn2+ than Li+, the unit cell volume decreases gradually upon Zn substitution without introducing significant structural changes. However, the ionic conductivity of the substitution phase was improved by 104 times (3.8 ​× ​10−6 ​S ​cm−1) at x ​= ​0.75 compared to unsubstituted Li4P2S6, which was achieved by generating deficiency on the Li sites via substitution. Such Li-ion deficient site enables Li ions to hop from one site to another in the crystal structure. The 3D diffusion pathway analysis using bond-valence-landscape-energy calculations suggests that the Li diffusion pathways are mostly two-dimensional in the ab plane in this structure. This study shows that an appropriate Li defect concentration within a given structure is critical to improving ionic conductivity. © 2023 Elsevier Inc.FALS

Novel layered iron vanadate as a stable high-voltage cathode material for nonaqueous magnesium-ion batteries

Magnesium-ion batteries (MIBs) have been deemed as a promising alternative to lithium-ion batteries because they can employ a Mg metal anode, potentially yielding a higher energy density. However, the lack of cathode materials capable of the reversible Mg intercalation in non-aqueous electrolytes severely limits the commercialisation of MIBs. In this study, a novel cathode material, layered iron vanadate (FeV3O9·1.1H2O), is proposed for use in non-aqueous MIBs. At 20 mA g−1, FeV3O9·1.1H2O registered a high reversible capacity and average voltage of 149 mAh/g and 2.53 V (vs. Mg/Mg2+), respectively. It also demonstrated a stable cycle life with an 85% capacity retention even after 500 discharge–charge cycles. The reversibility of the Mg intercalation reaction on this novel iron vanadate-based host was confirmed through elemental analyses, X-ray diffraction (XRD), and high-resolution transmission electron microscopy (TEM). This study offers valuable insights that could facilitate the design and development of novel oxide-based materials as high-performance cathodes for non-aqueous MIBs. © 2023FALS

Anomalous Sodium Storage Behavior in Al/F Dual-Doped P2-Type Sodium Manganese Oxide Cathode for Sodium-Ion Batteries

Various types of sodium manganese oxides are promising cathode materials for sodium storage systems. One of the most considerable advantages of this family of materials is their widespread natural abundance. So far, only a few host candidates have been reported and there is a need to develop new materials with improved practical electrochemical performance. Here, P2-type Al/F-doped sodium manganese oxide as well as its unique sodium storage mechanism is demonstrated by a combination of electrochemical characterization, structural analyses from powder X-ray diffraction (XRD) data, and 3D bond valence energy level calculations for the sodium diffusion pathways. The material exhibits a high reversible capacity of 164.3 mAh g−1 (0.3C rate) and capacity retention of 89.1% after 500 cycles (5C rate). The study clearly unravels the beneficial effect of the doping and the unique sodium intercalation mechanism devoid of the low diffusion O3 transformation. © 2020 Wiley-VCH GmbH1

Boosting Tunnel-Type Manganese Oxide Cathodes by Lithium Nitrate for Practical Aqueous Na-Ion Batteries

Aqueous Na-ion batteries are proposed as cheap, safe, environmentally friendly systems for large-scale energy storage owing to the high abundance of sodium in earth&apos;s crust and the benign nature of most of its salts. Practical utilization, however, is limited by poor electrochemical performance due to the slow diffusion kinetics of large sodium ions. Here, lithium nitrate was added to the electrolyte solutions to boost the performance of sodium manganese oxide cathodes. Ultrafast rate capability, high ion diffusivity, and superior cycling stability are attributed to enhanced conductivity of the ions in the solution, cointercalation of Li and Na ions, and lower cathode surface resistance. Three-dimensional bond valence maps illuminate the intercalation mechanism of sodium ions in the host structure. Lithium ions establish additional diffusion paths that activate sodium sites. Multistack cells were constructed and showed good electrochemical performance and high mechanical flexibility, which can be exploited to elaborate very effective practical batteries. © 2020 American Chemical Society1

Na2ZrCl6 enabling highly stable 3 V all-solid-state Na-ion batteries

Halide solid electrolytes (SEs) are emerging as an alternative to sulfide and/or oxide SEs for applications in all-solid-state batteries owing to the advantage fulfilling high (electro)chemical stability and mechanical sinterability at the same time. Thus far, the developments in halide SEs have focused on Li+ superionic conductors. Herein, the development of a new Na+-conducting halide SE, mechanochemically prepared Na2ZrCl6 (1.8 × 10−5 S cm−1 at 30°C) with excellent oxidative electrochemical stability, is described. A trigonal crystal structure with the P3¯m1 symmetry is successfully identified by the Rietveld refinement of X-ray diffraction. Additionally, the bond valence sum energy level calculations disclose one-dimensional preferable Na+-diffusion channels in Na2ZrCl6. It is to be noted that despite the rather low Na+ conductivity of Na2ZrCl6, NaCrO2 electrodes that uses Na2ZrCl6 in NaCrO2/Na-Sn all-solid-state Na-ion batteries demonstrate an exceptionally high initial Coulombic efficiency of 93.1% and a high reversible capacity of 111 mA h g−1 at 0.1C and 30 °C (98.4% and 123 mA h g−1 at 60 °C), highlighting the excellent electrochemical stability of Na2ZrCl6. © 2021 Elsevier B.V.1

The Sodium Storage Mechanism in Tunnel‐Type Na 0.44

Tunnel-type sodium manganese oxide is a promising cathode material for aqueous/nonaqueous sodium-ion batteries, however its storage mechanism is not fully understood, in part due to the complicated sodium intercalation process. In addition, low cyclability due to manganese dissolution has limited its practical application in rechargeable batteries. Here, the intricate sodium intercalation mechanism of Na0.44MnO2 is revealed by combination of electrochemical characterization, structure determination from powder X-ray diffraction data, 3D bond valence difference maps, and barrier-energy calculations of the sodium diffusion. NaI is proposed as an important electrolyte solution additive. It is shown to form a thin, beneficial, and durable cathode surface film that prevents manganese dissolution. The addition of 0.01 m NaI to electrolyte solutions based on alkyl carbonate solvents and NaClO4 greatly improves the cycling efficiency, raising the capacity retention from 86% to 96% after 600 cycles. This study determines the core aspects of the sodium intercalation mechanism in tunnel-type sodium manganese oxide and shows how it can serve as a durable cathode material for rechargeable Na batteries. © 2020 WILEY-VCH Verlag GmbH &amp; Co. KGaA, Weinheim1

New Cost‐Effective Halide Solid Electrolytes for All‐Solid‐State Batteries: Mechanochemically Prepared Fe 3+

Owing to the combined advantages of sulfide and oxide solid electrolytes (SEs), that is, mechanical sinterability and excellent (electro)chemical stability, recently emerging halide SEs such as Li3YCl6 are considered to be a game changer for the development of all-solid-state batteries. However, the use of expensive central metals hinders their practical applicability. Herein, a new halide superionic conductors are reported that are free of rare-earth metals: hexagonal close-packed (hcp) Li2ZrCl6 and Fe3+-substituted Li2ZrCl6, derived via a mechanochemical method. Conventional heat treatment yields cubic close-packed monoclinic Li2ZrCl6 with a low Li+ conductivity of 5.7 × 10−6 S cm−1 at 30 °C. In contrast, hcp Li2ZrCl6 with a high Li+ conductivity of 4.0 × 10−4 S cm−1 is derived via ball-milling. More importantly, the aliovalent substitution of Li2ZrCl6 with Fe3+, which is probed by complementary analyses using X-ray diffraction, pair distribution function, X-ray absorption spectroscopy, and Raman spectroscopy measurements, drastically enhances the Li+ conductivity up to ≈1 mS cm−1 for Li2.25Zr0.75Fe0.25Cl6. The superior interfacial stability when using Li2+xZr1−xFexCl6, as compared to that when using conventional Li6PS5Cl, is proved. Furthermore, an excellent electrochemical performance of the all-solid-state batteries is achieved via the combination of Li2ZrCl6 and single-crystalline LiNi0.88Co0.11Al0.01O2. © 2021 Wiley-VCH GmbH1