Revealing performance of 78Li2S-22P2S5 glass ceramic based solid-state batteries at different operating temperatures

78Li₂S-22P₂S₅ are sulfide electrolytes with high lithium-ion conductivity and wide electrochemical windows in the Li₂S-P₂S₅ system, making them attractive solid electrolytes for ASSLBs. However, the role and potential of 78Li₂S-22P₂S₅ solid electrolytes over a wide temperature range are still not fully understood. Therefore, we constructed solid-state batteries with NCM622 as the positive electrode and 78Li₂S-22P₂S₅ glass-ceramics as the electrolyte to investigate in depth the differences in battery performance over a wide temperature range and their intrinsic mechanisms. The in-situ impedance and relaxation time distribution (DRT) demonstrated the electrochemical stability of the electrolyte over a wide temperature range, while the in-situ stacking pressure observed a large volume change during cycling at 60 °C, leading to local solid-solid contact failure and poor cycling stability. This study provides insight into the advantages and problems of 78Li₂S-22P₂S₅ in the wide temperature range as well as a basis for the construction of ASSLBs with high energy density and long cycle life.     

Li2S-P2S5体系电解质及其在全固态锂离子电池中的应用研究进展

全固态锂离子电池具有安全性能好、能量密度高、工作温区广等优点,被广泛应用于便携式电子设备。固态电解质是全固态锂离子电池的关键材料之一,其中的硫化物电解质具有离子电导率高、电化学窗口宽、晶界电阻低和易成膜等特点,被认为最有希望应用于全固态锂离子电池。本文综述了Li_2S-P_2S_5体系电解质的发展状况,包括固态电解质的制备、改性、表征以及电极/固态电解质之间的固-固界面的稳定兼容问题。本文还涉及了以Li_2S-P_2S_5为电解质的全固态锂离子电池性能的研究进展。     

Li7P3S11电解质的合成、传导及应用

固态电解质是固态电池中的关键材料,开发具有高离子电导率、高化学/电化学稳定性、电极兼容性良好的固态电解质正成为研究热点。硫化物固态电解质相较其它固态电解质具有更高的离子电导率和良好的机械加工性能等优势,是最有前景实现实用化的固态电解质之一。在众多硫化物固态电解质中,Li₇P₃S₁₁因其高的离子电导率和较低的原料成本而极具研究意义。本文首先介绍了Li₇P₃S₁₁电解质的结构、Li+传导机理及合成路径;其次,针对该电解质的电导率提高、空气/水稳定性提升、固固界面稳定性及电解质自身稳定性改善等问题,综述了目前常用的改性策略研究;再次,总结了基于Li₇P₃S₁₁电解质的全固态锂离子电池和全固态锂硫电池的构筑;最后,本文分析了Li₇P₃S₁₁电解质的研究和应用面临的挑战,并指出该电解质未来发展的趋势。     

Variation in structure and Li<Superscript>+</Superscript>-ion migration in argyrodite-type Li<Subscript>6</Subscript>PS<Subscript>5</Subscript>X (X = Cl,Br, I) solid electrolytes

All-solid-state rechargeable lithium-ion batteries (AS-LIBs) are attractive power sources for electrochemical applications due to their potentiality in improving safety and stability over conventional batteries with liquid electrolytes. Finding a solid electrolyte with high ionic conductivity and compatibility with other battery components is a key factor in raising the performance of AS-LIBs. In this work, we prepare argyrodite-type Li₆PS₅X (X = Cl, Br, I) using mechanical milling followed by annealing. X-ray diffraction characterization reveals the formation and growth of crystalline Li₆PS₅X in all cases. Ionic conductivity of the order of 7?×?10^?4 S cm^?1 in Li₆PS₅Cl and Li₆PS₅Br renders these phases suitable for AS-LIBs. Joint structure refinements using high-resolution neutron and laboratory X-ray diffraction provide insight into the influence of disorder on the fast ionic conductivity. Besides the disorder in the lithium distribution, it is the disorder in the S^2?/Cl^? or S^2?/Br^? distribution that we find to promote ion mobility, whereas the large I^? cannot be exchanged for S^2? and the resulting more ordered Li₆PS₅I exhibits only a moderate conductivity. Li⁺ ion migration pathways in the crystalline compounds are modelled using the bond valence approach to interpret the differences between argyrodites containing different halide ions.     

Electrochemical behavior of LiCoO2 as aqueous lithium-ion battery electrodes

Despite the large number of studies on the behavior of LiCoO₂ in organic electrolytes and its recent application as a positive electrode in rechargeable water battery prototypes, a little information is available about the lithium intercalation reaction in this layered compound in aqueous electrolytes. This work shows that LiCoO₂ electrodes can be reversibly cycled in LiNO₃ aqueous electrolytes for tens of cycles at remarkably high rates with impressive values specific capacity higher than 100 mAh/g, and with a coulomb efficiency greater than 99.7%. Stable and reproducible cycling measurements have been made using a simple cell design that can be easily applied to the study of other intercalation materials, assuming that they are stable in water and that their intercalation potential range matches the electrochemical stability window of the aqueous electrolyte. The experimental arrangement uses a three-electrode flooded cell in which another insertion compound acts as a reversible source and sink of lithium ions, i.e., as the counter electrode. A commercial reference electrode is also present. Both the working and the counter electrodes have been prepared as thin layers on a metallic substrate using the procedures typical for the study of electrodes for lithium-ion batteries in organic solvent electrolytes.     

New lithium salts in electrolytes for lithium-ion batteries (Review)

The properties of electrolyte systems based on standard nonaqueous solvent composed of a mixture of dialkyl and alkylene carbonates and new commercially available lithium salts potentially capable of being an alternative to thermally unstable and chemically active lithium hexafluorophosphate LiPF₆ in the mass production of lithium-ion rechargeable batteries are surveyed. The advantages and drawbacks of electrolytes containing lithium salts alternative to LiPF₆ are discussed. The real prospects of substitution for LiPF₆ in electrolyte solutions aimed at improving the functional characteristics of lithium-ion batteries are assessed. Special attention is drawn to the efficient use of new lithium salts in the cells with electrodes based on materials predominantly used in the current mass production of lithium-ion batteries: grafitic carbon (negative electrode), LiCoO₂, LiMn₂O₄, LiFePO₄, and also solid solutions isostructural to lithium cobaltate with the general composition LiMO₂ (M = Co, Mn, Ni, Al) (positive electrode).     

Electrolytic molybdenum sulfides for thin-layer lithium power sources

The active molybdenum sulfide compound Mo₂S₃, which should be considered as a cathode material for thin-layer rechargeable power source, has been produced by electrolysis. Using impedance spectroscopy and potential relaxation method after current interruption, the kinetic parameters of lithium intercalation in electrolytic Mo₂S₃ have been obtained. Activation energy of Li⁺ migration in electrolyte (13.76 kJ/mol), charge transfer through the Mo₂S₃ electrode/electrolyte interface (38.8 kJ/mol), and Li⁺ diffusion in a solid phase (57.3 kJ/mol) have also been established. Taking into account the coefficient data of charge mass transfer in a solid phase and the reaction rate coefficient of charge transfer through the interface electrode/electrolyte within the temperature range 20–50 °C, the stage of Li⁺ transfer in a solid phase has been determined as a limiting stage for lithium intercalation in electrolytic molybdenum sulfide Mo₂S₃.     

A novel anode material of antimony nitride for rechargeable lithium batteries

Antimony nitride thin film has been successfully fabricated by magnetron sputtering method and its electrochemistry with lithium was investigated for the first time. The reversible discharge capacity of Sb₃N/Li cells cycled between 0.3 V and 3.0 V was found above 600 mAh/g. By using transmission electron microscopy and selected area electron diffraction measurements, the conversion reaction of Sb₃N into Li₃Sb and Li₃N was revealed during the lithium electrochemical reaction of Sb₃N thin film electrode. The high reversible capacity and the good cycleability made Sb₃N one of promising anode materials for future rechargeable lithium batteries.     

Lithium Ion Pathway within Li7La3Zr2O12‐Polyethylene Oxide Composite Electrolytes

Polymer–ceramic composite electrolytes are emerging as a promising solution to deliver high ionic conductivity, optimal mechanical properties, and good safety for developing high‐performance all‐solid‐state rechargeable batteries. Composite electrolytes have been prepared with cubic‐phase Li₇La₃Zr₂O₁₂ (LLZO) garnet and polyethylene oxide (PEO) and employed in symmetric lithium battery cells. By combining selective isotope labeling and high‐resolution solid‐state Li NMR, we are able to track Li ion pathways within LLZO‐PEO composite electrolytes by monitoring the replacement of ⁷Li in the composite electrolyte by ⁶Li from the ⁶Li metal electrodes during battery cycling. We have provided the first experimental evidence to show that Li ions favor the pathway through the LLZO ceramic phase instead of the PEO‐LLZO interface or PEO. This approach can be widely applied to study ion pathways in ionic conductors and to provide useful insights for developing composite materials for energy storage and harvesting.     

Comparative Study of Special Features of the Oxygen Reaction (Molecular Oxygen Ionization and Evolution) in Aqueous and Nonaqueous Electrolyte Solutions (a Review)

Studies of the oxygen reaction, including the oxygen ionization and evolution processes occurring at typical electrode materials in aqueous and nonaqueous electrolytes, are analyzed. A connection between the problematics of the oxygen electrode reaction in nonaqueous media and the developing of novel batteries, in the first place, Li–O₂ batteries, is emphasized. Unlike aqueous solutions, the oxygen reduction in aprotic electrolytes was shown to occur without breaking of the O–O bond; it is accompanied by formation of poorly soluble product of two-electron reaction (Li₂O₂) in the pores of positive electrode. The effect of the solvent donor number and the anion composition on the oxygen reduction mechanism and the lithium peroxide deposit structure is described. A marked reduction of the Li₂O₂ oxidation overvoltage when passing from carbonaceous materials to platinum-containing catalysts in the positive electrode is elucidated; in the latter case, the effect of electrocatalyst type upon the Li₂O₂ formation reaction is somewhat reduced. The elucidation of the contribution of processes occurring at the free and lithium-peroxide-covered electrode surface during the oxygen reaction for wide variety of active materials is formulated as the main basic problem of the future research.     

Tuning the Chemistry of Organonitrogen Compounds for Promoting All‐Organic Anionic Rechargeable Batteries

The ever‐increasing demand for rechargeable batteries induces significant pressure on the worldwide metal supply, depleting resources and increasing costs and environmental concerns. In this context, developing the chemistry of anion‐inserting electrode organic materials could promote the fabrication of molecular (metal‐free) rechargeable batteries. However, few examples have been reported because little effort has been made to develop such anionic‐ion batteries. Here we show the design of two anionic host electrode materials based on the N‐substituted salts of azaaromatics (zwitterions). A combination of NMR, EDS, FTIR spectroscopies coupled with thermal analyses and single‐crystal XRD allowed a thorough structural and chemical characterization of the compounds. Thanks to a reversible electrochemical activity located at an average potential of 2.2 V vs. Li⁺/Li, the coupling with dilithium 2,5‐(dianilino)terephthalate (Li₂DAnT) as the positive electrode enabled the fabrication of the first all‐organic anionic rechargeable batteries based on crystallized host electrode materials capable of delivering a specific capacity of ≈27 mAh/g_electrodes with a stable cycling over dozens of cycles (≈24 Wh/kg_electrodes).     

The search for a solid electrolyte,as a polysulfide barrier,for lithium/sulfur batteries

Composite Li₁₀SnP₂S₁₂ (LSPS)/polyethylene oxide (PEO) films, containing 25 to 50 % polymer, were electrophoretically deposited from acetone-based suspension and tested as possible candidates for polysulfide barriers in Li/S batteries. It was found by XRD and XPS tests that saturation of composite films by LiI salt, followed by prolonged annealing at 90 °C, diminishes the crystallinity of neat LSPS and results in the formation of a novel composite Li_10+xI_xSnP₂S₁₂ (LISPS)/P(EO)₃/LiI solid electrolyte (x < 1). The high room-temperature ion conductivity of amorphous sulfide Li_10+xI_xSnP₂S₁₂ (0.1–0.3 mS cm^?1) is restricted by slow ion transport via the polymer electrolyte (PE) imbedded in ceramics and grain boundaries between the PE and sulfide. Increase in polymer content and temperature improves total ion transport in the LISPS/PEO system. Conformal EPD coating of sulfur and lithium sulfide cathodes by the developed composite electrolyte increased the reversible capacity and Faradaic efficiency of the Li/S and Li/Li₂S cells and enabled their operation at 60 °C.     

Electochemical characteristics of LiMn<Subscript>2</Subscript>O<Subscript>4</Subscript>/Li<Subscript>4</Subscript>Ti<Subscript>5</Subscript>O<Subscript>12</Subscript> battery with conducting polymeric binder

Lithium-ion battery based on LiMn₂O₄/Li₄Ti₅O₁₂ materials was assembled for the first time. The cathode and anode of this battery are prepared with the aqueous combined binder poly-3,4-ethylenedioxythiophene: polystyrene sulfonate/carboxymethylcellulose (without polyvinylidene fluoride). The capacity of the LiMn₂O₄/Li₄Ti₅O₁₂ battery was found to be 75 mA h g^–1 at 0.1 C and 55 mA h g^–1 at 1 C. A 95% capacity was retained after 100 charge-discharge cycles. The batteries demonstrated a high Coulombic efficiency close to 100%. Scanning electron microscopy demonstrated that using the conducting binder poly-3,4-ethylenedioxythiophene: polystyrene sulfonate/carboxymethylcellulose provides formation of dense compact layers of electrode materials with good adhesion to the substrate. The electrode structure remains maintained after 100 charge-discharge cycles.     

Atomic layer coating to mitigate capacity fading associated with manganese dissolution in lithium ion batteries

Ultrathin surface coatings (< 5 nm) on electrodes have been developed to mitigate the capacity decay induced by manganese (Mn) dissolution, a limiting factor for Mn-based oxide electrode materials in lithium ion batteries. We demonstrated that the capacity decay was attributed to the Mn deposited on the graphite electrode accelerating the electrolyte decomposition. While the Al₂O₃ coating on the positive electrode suppressed the Mn dissolution, we found that the Al₂O₃ coating on the negative electrode was counter-intuitively more beneficial and efficient in preventing the Mn deposition and achieving excellent capacity retention in lithium ion batteries.     

All-solid-state batteries with Li2O-Li2S-P2S5 glass electrolytes synthesized by two-step mechanical milling

Sulfide solid electrolytes, which show high ion conductivity, are anticipated for use as electrolyte materials for all-solid-state batteries. One drawback of sulfide solid electrolytes is their low chemical stability in air. They are hydrolyzed by moisture and generate H₂S gas. Substituting oxygen atoms for sulfur atoms in sulfide solid electrolytes is effective for suppression of H₂S gas generation in air. Especially, the xLi₂O·(75-x)Li₂S·25P₂S₅ (mol%) glasses hardly generated H₂S gas in air. However, substituting oxygen atoms for sulfur atoms caused a decrease in conductivity. The x?=?7 glass showed high chemical stability in air and maintained high conductivity of 2.5?×?10^?4 S cm^?1 at room temperature. Performance of cells using the 7Li₂O·68Li₂S·25P₂S₅ and the 75Li₂S·25P₂S₅ glasses as solid electrolytes were compared. All-solid-state C/LiCoO₂ cell using the 7Li₂O·68Li₂S·25P₂S₅ glass produced performance as good as that obtained using the 75Li₂S·25P₂S₅ glass. Capacity retention and change of interfacial resistance of the former cell were superior to those of the latter cell after storage at 4.0 V and 60 °C. The diffusion of oxygen element into the 7Li₂O·68Li₂S·25P₂S₅ glass was less than that into the 75Li₂S·25P₂S₅ glass after storage at the voltage of 4.0 V at 60 °C. Improvement of the stability of sulfide solid electrolytes to moisture was related to cell performance as well as an increase in conductivity.     

Electrospun V2O5 Nanostructures with Controllable Morphology as High‐Performance Cathode Materials for Lithium‐Ion Batteries

Porous V₂O₅ nanotubes, hierarchical V₂O₅ nanofibers, and single‐crystalline V₂O₅ nanobelts were controllably synthesized by using a simple electrospinning technique and subsequent annealing. The mechanism for the formation of these controllable structures was investigated. When tested as the cathode materials in lithium‐ion batteries (LIBs), the as‐formed V₂O₅ nanostructures exhibited a highly reversible capacity, excellent cycling performance, and good rate capacity. In particular, the porous V₂O₅ nanotubes provided short distances for Li⁺‐ion diffusion and large electrode–electrolyte contact areas for high Li⁺‐ion flux across the interface; Moreover, these nanotubes delivered a high power density of 40.2 kW kg^?1 whilst the energy density remained as high as 201 W h kg^?1, which, as one of the highest values measured on V₂O₅‐based cathode materials, could bridge the performance gap between batteries and supercapacitors. Moreover, to the best of our knowledge, this is the first preparation of single‐crystalline V₂O₅ nanobelts by using electrospinning techniques. Interestingly, the beneficial crystal orientation provided improved cycling stability for lithium intercalation. These results demonstrate that further improvement or optimization of electrochemical performance in transition‐metal‐oxide‐based electrode materials could be realized by the design of 1D nanostructures with unique morphologies.     

Vacancy‐Controlled Na+ Superion Conduction in Na11Sn2PS12

Highly conductive solid electrolytes are crucial to the development of efficient all‐solid‐state batteries. Meanwhile, the ion conductivities of lithium solid electrolytes match those of liquid electrolytes used in commercial Li⁺ ion batteries. However, concerns about the future availability and the price of lithium made Na⁺ ion conductors come into the spotlight in recent years. Here we present the superionic conductor Na₁₁Sn₂PS₁₂, which possesses a room temperature Na⁺ conductivity close to 4 mS cm^?1, thus the highest value known to date for sulfide‐based solids. Structure determination based on synchrotron X‐ray powder diffraction data proves the existence of Na⁺ vacancies. As confirmed by bond valence site energy calculations, the vacancies interconnect ion migration pathways in a 3D manner, hence enabling high Na⁺ conductivity. The results indicate that sodium electrolytes are about to equal the performance of their lithium counterparts.     

Interaction of solid and polymeric lithium electrolytes with composites based on carbon fibers and silicon nanoclusters: Quantum-chemical modeling

In the framework of the search for promising electrodes and membranes for lithium-ion batteries, quantum-chemical modeling of the contact area of the solid (Li₁₀GeP₂S₁₂) and polymeric LiNafion · nDMSO-based electrolytes with an anode as carbon fibers coated with silicon nanoclusters (Si _n C _m ) has been performed by the density functional theory method with inclusion of gradient correction and periodic conditions (PBE/PAW). It has been found that the polymeric electrolytes form a better contact with the electrode surface than the solid electrolytes. The barriers to lithium transport in the polymeric LiNafion · nDMSO-based electrolyte have been estimated at 0.3 eV, and those to Li migration from the electrolyte into the electrode have been estimated at 0.4 eV.     

Cu3V2O8 Nanoparticles as Intercalation‐Type Anode Material for Lithium‐Ion Batteries

Cu₃V₂O₈ nanoparticles with particle sizes of 40–50 nm have been prepared by the co‐precipitation method. The Cu₃V₂O₈ electrode delivers a discharge capacity of 462 mA h g^?1 for the first 10 cycles and then the specific capacity, surprisingly, increases to 773 mA h g^?1 after 50 cycles, possibly as a result of extra lithium interfacial storage through the reversible formation/decomposition of a solid electrolyte interface (SEI) film. In addition, the electrode shows good rate capability with discharge capacities of 218 mA h g^?1 under current densities of 1000 mA g^?1. Moreover, the lithium storage mechanism for Cu₃V₂O₈ nanoparticles is explained on the basis of ex situ X‐ray diffraction data and high‐resolution transmission electron microscopy analyses at different charge/discharge depths. It was evidenced that Cu₃V₂O₈ decomposes into copper metal and Li₃VO₄ on being initially discharged to 0.01 V, and the Li₃VO₄ is then likely to act as the host for lithium ions in subsequent cycles by means of the intercalation mechanism. Such an “in situ” compositing phenomenon during the electrochemical processes is novel and provides a very useful insight into the design of new anode materials for application in lithium‐ion batteries.     

脉冲激光沉积CrP薄膜及其电化学性能

采用脉冲激光溅射Cr和P粉的混合靶成功制备了CrP薄膜,选区电子衍射(SAED)和光电子能谱(XPS)分析显示经过真空原位400℃退火以后,薄膜主要由多晶态的CrP组成。非原位HRTEM和SEM测试结果表明CrP薄膜在充放电前后的形貌有较大的改变。SAED、充放电和循环伏安测试证实了CrP和锂的电化学反应机理如下：CrP在Li⁺的驱动下,生成了Cr和Li₃P。在其后的充放电过程中,发生了Li在LiP中可逆的嵌入和脱出反应。由于CrP首次容量高达1 168 mAh·g^-1以及在0.7 V左右具有平稳的放电平台,显示了它可能成为一种新型的锂离子电池的负极材料。