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Lithium metal is a promising anode material for the development of advanced all-solid-state batteries (ASSBs) with high energy density. Among the various solid electrolytes, lithium phosphorus oxynitride glass electrolyte (LiPON) is notable for facilitating stable Li plating-stripping reactions in ASSBs employing Li metal. The aim of this study is to examine the Li/LiPON interface, with a specific emphasis on the reductive decomposition of LiPON near this interface. We employed time-of-flight elastic recoil detection analysis (TOF-ERDA) to assess changes in Li concentration around the Cu/LiPON interface immediately prior to the Li plating reaction. Our electrochemical measurements indicate that critical decomposition of LiPON occurs when the voltage at the Cu electrode is reduced to 0.1 V vs. Li/Li+ at 25 °C, resulting in the in situ formation of Li3P operating at 0.7 V vs. Li/Li+ as an anode material. The TOF-ERDA findings reveal that this decomposition reaction results in a layer with partial decomposition (ranging from 5 to 25% on average) extending up to approximately 30 nm from the Cu/LiPON interface. This insight is vital for enhancing the design and performance of ASSBs. [ABSTRACT FROM AUTHOR]

Lithium phosphorus-oxynitride (LiPON) films were deposited by the method of anodic evaporation of Li3PO4 in the nitrogen plasma of a low-pressure arc. A method for adjusting the degree of decomposition of vapors is proposed based on a change in the frequency of interaction of electrons with vapors at a constant heating power of the anode-crucible. The conditions ensuring the formation of films with a homogeneous microstructure and ionic conductivity (1–2) × 10−6 S/cm at a deposition rate of 8 nm/min have been determined. It is shown that the degree of vapor dissociation critically affects the morphology of the films and the magnitude of their ionic conductivity. The results of cyclic tests of LiPON films deposited by anodic evaporation in a low-pressure arc are presented. [ABSTRACT FROM AUTHOR]

Lithium phosphorus oxynitride (LiPON) is an amorphous solid-state lithium ion conductor displaying exemplary cyclability against lithium metal anodes. There is no definitive explanation for this stability due to the limited understanding of the structure of LiPON. Herein, we provide a structural model of RF-sputtered LiPON. Information about the short-range structure results from 1D and 2D solid-state NMR experiments. These results are compared with first principles chemical shielding calculations of Li-P-O/N crystals and ab initio molecular dynamics-generated amorphous LiPON models to unequivocally identify the glassy structure as primarily isolated phosphate monomers with N incorporated in both apical and as bridging sites in phosphate dimers. Structural results suggest LiPON's stability is a result of its glassy character. Free-standing LiPON films are produced that exhibit a high degree of flexibility, highlighting the unique mechanical properties of glassy materials.

Spinel‐type LiNi0.5Mn1.5O4 (LNMO) is one of the most promising 5 V‐class cathode materials for Li‐ion batteries that can achieve high energy density and low production costs. However, in liquid electrolyte cells, the high voltage causes continuous cell degradation through the oxidative decomposition of carbonate‐based liquid electrolytes. In contrast, some solid‐state electrolytes have a wide electrochemical stability range and can withstand the required oxidative potential. In this work, a thin‐film battery consisting of an LNMO cathode with a solid lithium phosphorus oxynitride (LiPON) electrolyte is tested and their interface before and after cycling is characterized. With Li metal as the anode, this system can deliver stable performance for 600 cycles with an average Coulombic efficiency >99%. Neutron depth profiling indicates a slight overlithiated layer at the interface prior to cycling, a result that is consistent with the excess charge capacity measured during the first cycle. Cryogenic electron microscopy further reveals intimate contact between LNMO and LiPON without noticeable structure and chemical composition evolution after extended cycling, demonstrating the superior stability of LiPON against a high voltage cathode. Consequently, design guidelines are proposed for interface engineering that can accelerate the commercialization of a high voltage cell with solid or liquid electrolytes. [ABSTRACT FROM AUTHOR]

Amorphous lithium phosphorus oxynitride (LIPON) has emerged as a promising solid electrolyte for all‐solid‐state thin‐film lithium batteries. In this context, the use of theoretical modeling to characterize, understand, or screen material properties is becoming increasingly important to complement experimental analysis or elucidate features at atomistic level that are difficult to obtain through experimental studies. Density functional theory (DFT) is the method of choice for quantum mechanical material modeling at the atomistic scale. The current state of the art represents DFT values, such as the formation or migration energies relevant for bulk phase of materials, as absolute numbers. Estimating the accuracy or fluctuation range of the different density functionals is challenging. In order to investigate the thermodynamic and kinetic properties of LIPON by DFT, an approach to describe the fluctuation range caused by the choice of the exchange‐correlation (XC) functional is developed. Three different model systems were chosen to characterize various structural features of amorphous LIPON, which are distinguished by the cross‐linking of the POuN4‐u‐structural units. The uncertainty Ũ is introduced as a parameter describing the fluctuation range of energy values. The uncertainty approach does not determine the accuracy of DFT results, but rather a fluctuation range in the DFT results without the need for a reference value from a higher level of theory or experiment. The uncertainty was determined for both the thermodynamic Li‐vacancy formation energies and the kinetic Li‐vacancy migration energies in LIPON. We assume that the uncertainty approach can be applied to different material systems with different density functionals. [ABSTRACT FROM AUTHOR]

Amorphous lithium phosphorus oxynitride (LiPON) films of various thicknesses were prepared by radio frequency (RF) magnetron sputtering as an electrolyte layer for inorganic all-solid-state electrochromic devices.The ionic conductivity of LiPON films measured by electrochemical impedance spectroscopy was all approximately 10−6 S/cm, and the average optical transmittance characterized by UV–Vis spectroscopy was over 80%, indicating that the prepared LiPON films were suitable for electrochromic applications. Monoclinic electrochromic devices (ECDs) (ITO/NiO x /LiPON/WO 3 /ITO) with different LiPON thicknesses were fabricated and studied. It was found that the electro-optical properties of the ECDs could be significantly affected by the thickness and surface roughness of LiPON films. The ECDs demonstrated the best combination of optical contrast (68.4% at 560 nm), switching time (27s), and cycling stability (optical modulation degradation of 6.93% for 200 cycles) when the LiPON thickness was 450 nm. The above results not only shed lights on improving the interfacial properties of solid electrolytes, but also give directions for the performance enhancement of inorganic all-solid electrochromic devices. • ITO/NiO x /LiPON/WO 3 /ITO all-solid-state ECDs with different LiPON thicknesses were fabricated and studied. • The mechanism of solid electrolyte thickness affecting interfacial properties is discussed. • This mechanism relies on the effect of electrolyte surface roughness on interfacial contact properties. • The electro-optical properties and cycling stability of the ECDs are be deeply dependent on the electrolyte thickness. [ABSTRACT FROM AUTHOR]

The structural, electronic and ion transport properties of an amorphous member of the LiPON family with non-trivial composition and cross-linking are studied by means of electronic structure calculations within Density Functional Theory. By a combination of an evolutionary algorithm followed by simulated annealing and alternatively by a rapid quenching protocol, structural models of disordered Li 5 P 4 O 8 N 3 are generated, which are characterized by a local demixing in Li-rich and Li-poor layers. These structures have a composition close to what is found experimentally in thin films and contain all the expected diversely coordinated atoms, namely triply- and doubly-coordinated nitrogens and bridging and non-bridging oxygens. The issue of ionic conductivity is addressed by calculating defect formation energies and migration barriers of neutral and charged point defects. Li + interstitials are energetically much preferred over vacancies, both when the lithium reservoir is metallic lithium and LiCoO 2 . The competitive formation of neutral Li interstitials when LiPON is contacted with metallic Li results in the chemical reduction of LiPON and the disruption of the network, as recently observed in experiments. [ABSTRACT FROM AUTHOR]

[Display omitted] • Li/LiPON bilayer thin film on LAGP improves both interfacial kinetics and stability. • Li thin film between LiPON/LAGP and Li foil reduces the interface resistance by 1/4. • The optimum thickness of LiPON is 250 nm for low resistance and stable cycling. • It restrains the Ge reduction and ensures intimate contact between LAGP and Li foil. • Li/LiPON improves a capacity and stability of all-solid-state Li-oxygen batteries. Emerging solid-state lithium batteries demand a stable solid electrolyte against both Li anodes and high-voltage cathodes. The NASICON-type Li 1.5 Al 0.5 Ge 1.5 (PO 4) 3 (LAGP) solid electrolyte is highly tolerant to high-voltage operation and air environments, but it suffers from poor interfacial compatibility with Li anodes. Herein, we revisit the Li/LiPON bilayer thin-film in mature and ultrastable thin-film batteries as a bifunctional interlayer that can resolve both chemical and mechanical interfacial problems between Li anodes and LAGP. Interestingly, defect-free contact of the Li thin film onto LiPON/LAGP dramatically reduces the anode interface impedance between LAGP and Li foil, which eliminates the step for Li foil heating. As a result, it delivers a high capacity and rate capability with a long cycle in all-solid-state Li-O 2 batteries. Moreover, by virtue of a systematic thin-film configuration, a model study with different interlayer combinations as well as LiPON thicknesses clearly distinguishes two degradation mechanisms in LAGP-based cells: chemical reduction of Ge at the anode interface and mechanical contact loss by nonuniform Li stripping/plating upon cycling. Thanks to its exceptional electrochemical stability window, this Li/LiPON-modified LAGP will help to achieve the commercialization of safe and long-lasting solid-state lithium batteries. [ABSTRACT FROM AUTHOR]

An artificial solid electrolyte interphase (SEI) consisting of a lithium‐ion conducting material enables the use of a LiNi0.5Mn1.5O4 cathode with conventional carbonate electrolytes. The coulombic loss and electrolyte oxidation are largely remedied by the nanometer‐scale artificial SEI. The thickness of the artificial SEI is optimized by balancing the protection and additional resistance. [ABSTRACT FROM AUTHOR]

Abstract: The influence of nitrogen in the mechanism of ionic conduction has been studied in lithium phosphorus oxynitride glasses with composition xLi2O.(100−x)P2O5 (x=38–60mol%). A correlation between glass structure and ionic conductivity has been established for explaining the conduction mechanism. The change of glass structure during nitridation has been studied as a function of lithium and nitrogen contents. Raman spectra confirm the increase of P2O7 4− groups with increasing lithium and the presence of nitrogen, as also shown by X-Ray Photoelectron Spectroscopy. The O1s core-level XPS spectra allow determining the variation of the bridging (BO) to non-bridging (NBO) oxygen ratio, observing that its decrease is directly linked to an increase of ionic conductivity. The ionic conductivity of oxynitride glasses is higher than that of their parent phosphate glasses, although this increase also depends on the lithium content. Furthermore, it has been demonstrated that the influence of nitrogen is higher in glasses with smaller amount of lithium. These findings will contribute to the design of glasses with lower lithium contents and high ionic conductivity for their application as solid electrolytes in lithium rechargeable batteries. [Copyright &y& Elsevier]

Abstract: Nanoindentation has been used to characterize the elastic modulus and hardness of LiPON films ranging in thickness from 1 to 10μm. Four fully dense, amorphous films were deposited on glass and sapphire substrates with one film annealed at 200°C for 20min. The modulus of LiPON is found to be approximately 77GPa, and argued to be independent of the substrate type, film thickness, and annealing. Based on the numerical analysis of Monroe and Newman, this value may be sufficiently high to mechanically suppress dendrite formation at the lithium/LiPON interface in thin film batteries . Using Sneddon''s stiffness equation and assuming the modulus is 77GPa, the hardness is found to be approximately 3.9GPa for all but the annealed film. The hardness of the annealed film is approximately 5% higher, at 4.1GPa. Atomic force microscopy images of the residual hardness impressions confirm the unexpected increase in hardness of the annealed film. Surprisingly, the indentation data also reveal time-dependent behavior in all four films. This indicates that creep may also play a significant role in determining how LiPON responds to complex loading conditions and could be important in relieving stresses as they develop during service. [Copyright &y& Elsevier]

[Display omitted] Lithium phosphorus oxy-nitride (LiPON) is a candidate solid electrolyte material for potential use in rechargeable lithium-ion batteries. The use of density functional theory simulations has allowed us to gain atomic-scale insight into the defect properties, solution of dopants and incorporation of lithium in LiPON. The Li 2 O Schottky is the most favourable disorder process in this material ensuring the formation of Li and O vacancies which are in turn required for vacancy mediated self-diffusion. The Na, As and S are the promising isovalent dopants that can be substituted on the Li, P and O sites respectively. The doping of Mg on the Li site leads to the formation of Li vacancies in LiPON. The promising dopant on the P site to create Li interstitials and oxygen vacancies is the Ge. The stability of the crystal structure upon Li incorporation (up to four Li) was considered. The incorporation confirmed the formation of Li+ ions and expanded the volume of the lattice. Incorporation of multiple Li atoms is more favourable than a single Li incorporation. The band gap of this material decreases upon of Li incorporation without changing its insulating character. [ABSTRACT FROM AUTHOR]

Construction of a stable artificial interlayer is a promising strategy to enhance cycling performance of high-voltage cathodes. Here, amorphous lithium phosphorus oxynitride (LiPON) thin film with a thickness of ∼15 nm was coated onto LiNi 0.5 Mn 1.5 O 4 (LNMO) thin film by magnetron sputtering. Detailed microstructure, electrochemical property, and electrochemical impedance spectroscopy (EIS) were undertaken to characterize and understand the role of LiPON at the interface. LiPON coating with favorable Li+ intercalating capability increases ionic conductivity of electrodes, protects high-voltage LNMO surface from side reaction, and inhibits dissolution of transition metals to control the integrity of spinel structure. Also, the space charge layer between LNMO and LiPON transports oxygen vacancy and heightens the manganese ions valence state. Therefore, with LiPON as artificial cathode-electrolyte interface covered on LNMO film, this composite cathode exhibits higher discharge capacities, longer cycling life, and better rate capability than the bare LNMO cathode. • The LiPON coating on LNMO exhibits higher discharge capacities, and better rate capability than the bare LiNi 0.5 Mn 1.5 O 4 cathode. • The space charge layer between LNMO and LiPON transports oxygen vacancy and heightens the manganese ions valence state. • LiPON coating with favorable Li+ intercalating capability increases ionic conductivity of electrodes, protects high-voltage LNMO surface from side reaction, and inhibits dissolution of transition metals to control the integrity of spinel structure. [ABSTRACT FROM AUTHOR]