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Materials that undergo conversion reactions to form different materials upon lithiation typically offer high specific capacity for energy storage applications such as Li ion batteries. However, since the reaction products often involve complex mixtures of electrically insulating and conducting particles and significant changes in volume and phase, the reversibility of conversion reactions is poor, preventing their use in rechargeable (secondary) batteries. In this paper, we fabricate and protect 3D conversion electrodes by first coating multiwalled carbon nanotubes (MWCNT) with a model conversion material, RuO2, and subsequently protecting them with conformal thin-film lithium phosphous oxynitride (LiPON), a well-known solid-state electrolyte. Atomic layer deposition is used to deposit the RuO2 and the LiPON, thus forming core double-shell MWCNT@RuO2@LiPON electrodes as a model system. We find that the LiPON protection layer enhances cyclability of the conversion electrode, which we attribute to two factors. (1) The LiPON layer provides high Li ion conductivity at the interface between the electrolyte and the electrode. (2) By constraining the electrode materials mechanically, the LiPON protection layer ensures electronic connectivity and thus conductivity during lithiation/delithiation cycles. These two mechanisms are striking in their ability to preserve capacity despite the profound changes in structure and composition intrinsic to conversion electrode materials. This LiPON-protected structure exhibits superior cycling stability and reversibility as well as decreased overpotentials compared to the unprotected core-shell structure. Furthermore, even at very low lithiation potential (0.05 V), the LiPON-protected electrode largely reduces the formation of a solid electrolyte interphase.

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]

Abstract Polycrystalline nickel ferrite (NiFe 2 O 4) thin films were fabricated by pulsed laser deposition (PLD) and coated with nanometer layer of lithium phosphorus oxynitride (LiPON) by radio frequency magnetron sputtering (RF sputtering). Physical characterizations demonstrated that NiFe 2 O 4 thin films were not destroyed by LiPON coating with 50 nm thickness. Discharge capacity of LiPON coated NiFe 2 O 4 thin film after 50 cycles at 5 μA cm−2 was 849 mAh g−1, much higher than the counterpart value of pristine NiFe 2 O 4 thin film (449 mAh g−1), while rate capability was also greatly enhanced. Ex situ TEM investigation confirmed the two-steps reaction mechanism between NiFe 2 O 4 and Li, which includes an irreversible decomposition reaction of NiFe 2 O 4 in the first discharge process and reversible reactions between NiO, Fe 2 O 3 and their nanosized metal particles afterward. The significant improvement on the electrochemical performance was ascribed to the amorphous LiPON layer on the surface, which suppressed the volume expansion of electrode, the formation of delaminated particles and generation of cracks on electrode surface, as proved by ex situ SEM and AFM results. The LiPON coating is an effective approach to enhance the electrochemical performance of conversion materials for lithium ion batteries. Highlights • Pristine and LiPON coated NiFe 2 O 4 thin films were fabricated. • LiPON coating benefits the electrochemical performance of NiFe 2 O 4 thin film. • Conversion mechanism was confirmed by ex situ TEM technique for the first time. • Ex situ SEM and AFM results explained the effect of LiPON coating. [ABSTRACT FROM AUTHOR]

Abstract: All-solid-state Li/LiPONB/TiOS microbatteries were manufactured at the pilot scale on silicon substrate. In a first attempt, the characterization of the active materials constituting the microbattery was achieved in order to determine their accurate composition, structure and morphology. Finally, a thorough electrochemical characterization was carried out on all-solid-state cells. Excellent performances were noted in terms of cycle life (with more than 1000 cycles), efficiency and self-discharge (less than 5% per year). In addition, the positive electrode highlighted a high volumetric capacity close to 90μAhcm−2 μm−1 when cycled at 100μAcm−2 between 1V and 3V vs. Li+/Li. [Copyright &y& Elsevier]

Abstract: Oxynitride phosphate glasses have been obtained by ammonolysis of xLi2O (1− x)P2O5 (x =0.5, 0.55, 0.575) glasses and their electrical conductivity and lithium structural environment studied. Nitrided glasses were prepared through thermal treatment of the phosphate glasses under ammonia flow at temperatures below 800 °C. Nitrogen incorporation produces a sharp increase in conductivity for low nitrogen contents, while the activation energy decreases. Conductivity increase is very small or negligible for N/P ratios higher than 0.1, and the effect of nitrogen is analogous for all Li/P ratios. The increase in the electrical conductivity is explained through the structural modifications produced after the nitrogen substitution within the glass network. 6Li NMR experiments show that the coordination number of Li+ decreases with N/P, which is interpreted as an increase in the Li–O bonds covalence. This effect of nitrogen on the lithium environment together with the increased glass density is thought to be counteracting the increase of conductivity for high nitrogen contents. [Copyright &y& Elsevier]

A 5 V lithium secondary cell was fabricated using LiFe0.5Mn1.5O4 cathode material with all-solid-state design. As an additional approach to improve the battery performance of the all-solid-state secondary cell, a metal oxide-retaining layer was placed between the cathode material and solid electrolyte. The cathode material has an excellent cyclability in this cell design, since it just loses 5 and 18% of its initial capacity after 100 and 500 charge–discharge cycles, respectively. [Copyright &y& Elsevier]

One of the most important problems in utilizing lithium metal anodes is its poor recharge-ability due to the unstable solid electrolyte layer formed by electrolyte decomposition. To overcome this problem, the surface of the lithium electrode is covered by a thin protective solid electrolyte layer, deposited by r.f. magnetron sputtering. Lithium phosphorous oxynitride (LiPON), which is used as an electrolyte in thin film batteries (TFBs), was examined for its potential in use as a protective layer for the anode. The spectroscopic and electrochemical characteristics of the LiPON layer were examined using scanning electron microscopy (SEM), X-ray diffraction (XRD), linear sweep voltammetry (LSV), cyclic voltammetry (CV), chronopotentiometry (CP), and electrochemical impedance spectroscopy (EIS). [Copyright &y& Elsevier]

Sputter deposition of LiPON films directly onto high Li+ conductivity solid electrolyte plates has been investigated as a means to minimize the reactivity of the plates to metallic Li. The LiPON films were shown to effectively passivate the plates in contact with metallic Li, in contrast to unpassivated plates that reacted immediately in contact with Li metal. The conductivity of the passivated solid electrolyte plates was measured to be 1.0×10−4 S cm−1, with Arrhenius activation energy of 0.36 eV and an electrochemical stability window of at least 0–5.0 V versus Li/Li+. The passivated solid electrolyte was capable of supporting electrochemical plating and stripping of Li metal, as demonstrated by EIS and CV measurements. These high chemical stability, high Li+ conductivity solid electrolyte plates will be useful for solid-state batteries employing Li anodes. [Copyright &y& Elsevier]

We report the characterization of two thin-film battery materials using neutron techniques. Neutron depth profiling (NDP) has been employed to determine the distribution of lithium and nitrogen simultaneously in lithium phosphorous oxynitride (LiPON) deposited by ion beam assisted deposition (IBAD). The depth profiles are based on the measurement of the energy of the charged particle products from the 6Li(n,α)3H and 14N(n,p)14C reactions for lithium and nitrogen, respectively. Lithium at the level of 1022 atoms/cm3 and N of 1021 atoms/cm3, distributed in the film thickness on the order of 1 μm, have been determined. This information provides insights into nitrogen incorporation and lithium concentration in the films under various fabrication conditions. NDP of lithium has also been performed on IBAD LiCoO2 films, in conjunction with instrumental neutron activation analysis (INAA) to determine the cobalt concentration. The Li/Co ratio thus obtained serves as an ex situ control for the thin-film evaporation process. The non-destructive nature of the neutron techniques is especially suitable for repeated analysis of these materials and for actual working devices. [Copyright &y& Elsevier]