LiPON Films Research Articles

Electrochemical Performance of Deposited LiPON Film/Lithium Electrode in Lithium-Sulfur Batteries.

This paper presents a composed lithium phosphate (LiPON) solid electrolyte interface (SEI) film which was coated on a lithium electrode via an electrodeposit method in a lithium-sulfur battery, and the structure of the product was characterized through infrared spectrum (IR) analysis, X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), environment scanning electron microscope (ESEM), etc. Meanwhile, the electrochemical impedance spectrum and the interface stability of the lithium electrode with the LiPON film was analyzed, while the coulomb efficiency and the cycle life of the lithium electrode with the LiPON film in the lithium-sulfur battery were also studied. It was found that this kind of film can effectively inhibit the charge from transferring at the interface between the electrode and the solution, which can produce a more stable interface impedance on the electrode, thereby improving the interface contact with the electrolyte, and effectively improve the discharge performance, cycle life, and the coulomb efficiency of the lithium-sulfur battery. This is of great significance for the further development of solid electrolyte facial mask technology for lithium-sulfur batteries.

Highly Conformal Solid Electrolyte for Li-Ion Batteries By Atomic Layer Deposition

Lithium phosphorus oxynitride (LiP x O y N z , commonly known as LiPON) is a state-of-the-art solid electrolyte material with suitably low resistivity and high ionic conductivity for all-solid-state thin-film microbatteries [1,2]. Thin and pinhole-free layers of LiPON can be fabricated using atomic layer deposition (ALD) [3]. Uniquely among thin-film fabrication methods, ALD is a technique that works for coating even challenging 3D interfaces [4,5]. In this work, LiPON ALD processes were optimized for two different lithium precursors at reasonable temperatures (~300 °C) and precursor pulse/purge lengths (< 5 s), and LiPON films were deposited onto PillarHall® lateral high-aspect-ratio (LHAR) test structures to investigate the conformality of the material. Comparative testing was performed between the two lithium precursors.The results indicated that more conformal LiPON films can be deposited using the appropriate precursors – in this case, lithium tert-butoxide (LiO t Bu) yielded greater penetration depths than lithium hexamethyldisilazide (Li-HMDS). The improved conformality observed when using LiO t Bu indicates that this precursor is a better choice for LiPON coatings on high-aspect-ratio structures. The ALD technique allowed for the deposition of highly conformal LiPON films, ~50–115 µm deep into 100–500 nm gaps. This opens possibilities for the use of LiPON as a solid electrolyte in batteries with high-surface-area electrodes. High surface areas are important not only for unlocking higher power densities (faster charging and discharging) in batteries, but also for enabling the use of thin-film technology in fabricating microbatteries with meaningful energy storage capacities.

LiPON/Multilayer-Graphene Interface Enables High-Rate Charging and Discharging

Graphite is the anode-active material commonly used in LIBs. In LIB, solid electrolyte interphase (SEI) is formed by the reduction of the liquid electrolyte, and the SEI plays a role as a passive film. In the charging process, Li ions transport in the liquid electrolyte and SEI, desolvation reactions of Li ions occur, and then Li ions insert into the graphite anode. It has been reported that the desolvation reaction of Li ions is the rate-limiting process[1]. Lithium phosphorous oxynitride glass (LiPON) is a well-known material as a solid electrolyte. However, it has been reported that the electrochemical window of LiPON ranges from 0.68 V to 2.63 V[2]. Therefore, it is possible that the decomposition reaction of LiPON occurs when the electrochemical cell is charged. Since the decomposition products can be a resistance, LiPON that is not easily reduced is required. In this study, we focused on the lithium phosphorus oxynitride glass (LiPON) electrolyte/multilayered graphene (MGr) film interface as an example without the desolvation process. In addition, we have investigated the relationship between LiPON composition ratio, electronic properties, and interfacial resistance by changing the sputtering conditions for LiPON film. Consequently, we found that the charge-transfer resistance at the MGr/LiPON interface was significantly small, although the MGr/LiPON interface was supposed to have inorganic solid electrolyte interphase resulting from the LiPON reduction decomposition. The figure shows a schematic illustration of the Liquid Electrolyte/MGr interface and the LiPON/MGr interface. Figure 1

Significant Strain Dissipation via Stiff‐Tough Solid Electrolyte Interphase Design for Highly Stable Alloying Anodes

AbstractThe pulverization of alloying anodes significantly restricts their use in lithium‐ion batteries (LIBs). This study presents a dual‐phase solid electrolyte interphase (SEI) design that incorporates finely dispersed Al nanoparticles within the LiPON matrix. This distinctive dual‐phase structure imparts high stiffness and toughness to the integrated SEI film. In comparison to single‐phase LiPON film, the optimized Al/LiPON dual‐phase SEI film demonstrates a remarkable increase in fracture toughness by 317.8 %, while maintaining stiffness, achieved through the substantial dissipation of strain energy. Application of the dual‐phase SEI film on an Al anode leads to a 450 % enhancement in cycling stability for lithium storage in dual‐ion batteries. A similar enhancement in cycling stability for silicon anodes, which face severe volume expansion issues, is also observed, demonstrating the broad applicability of the dual‐phase SEI design. Specifically, homogeneous Li−Al alloying has been observed in conventional LIBs, even when paired with a high mass loading LiNi0.5Co0.3Mn0.2O2 cathode (7 mg cm−2). The dual‐phase SEI film design can also accelerate the diffusion kinetics of Li‐ions through interface electronic structure regulation. This dual‐phase design can integrate stiffness and toughness into a single SEI film, providing a pathway to enhance both the structural stability and rate capability of alloying anodes.

Significant Strain Dissipation via Stiff-Tough Solid Electrolyte Interphase Design for Highly Stable Alloying Anodes.

The pulverization of alloying anodes significantly restricts their use in lithium-ion batteries (LIBs). This study presents a dual-phase solid electrolyte interphase (SEI) design that incorporates finely dispersed Al nanoparticles within the LiPON matrix. This distinctive dual-phase structure imparts high stiffness and toughness to the integrated SEI film. In comparison to single-phase LiPON film, the optimized Al/LiPON dual-phase SEI film demonstrates a remarkable increase in fracture toughness by 317.8%, while maintaining stiffness, achieved through the substantial dissipation of strain energy. Application of the dual-phase SEI film on an Al anode leads to a 450% enhancement in cycling stability for lithium storage in dual-ion batteries. A similar enhancement in cycling stability for silicon anodes, which face severe volume expansion issues, is also observed, demonstrating the broad applicability of the dual-phase SEI design. Specifically, homogeneous Li-Al alloying has been observed in conventional LIBs, even when paired with a high mass loading LiNi0.5Co0.3Mn0.2O2 cathode (7 mg cm-2). The dual-phase SEI film design can also accelerate the diffusion kinetics of Li-ions through interface electronic structure regulation. This dual-phase design can integrate stiffness and toughness into a single SEI film, providing a pathway to enhance both the structural stability and rate capability of alloying anodes.

In-Situ Thermo-Mechanical Characterization and Strain Engineering of Lipon Thin Films

High temperature multi-optical-stress sensor (HTMOSS) has been used to characterize the coefficient of thermal expansion (CTE) and yield stress of 1-micron thick LiPON films. Six fully dense, amorphous films were deposited on glass and sapphire substrates. The films were then annealed at temperatures ranging from 80 to 200 C for 3 hours. The CTE of LiPON is found to be approximately 4.1e-6, and argued to be independent of the substrate type. Because of this intermediate CTE value, by varying the substrate, we could impose either tension and compression due to thermal mismatch to the film. We observed further that the yield stress of the film is approximately 60 MPa under compression and 100 MPa under tension. Using constant-load hold at and beyond yield point, the films were found to relieve the stress developed during heating with visco-plastic deformation, which led to permanent residual stress during cooling as high as 120 MPa in either tension or compression depending on substrate type. We also found that at annealing temperature higher than 140 C LiPON lost ductility which could be due to composition changes as indicated by XPS measurement. The stress-relief mechanism at constant-load indicates that LiPON may be beneficial as a protective layer against dendrites penetration. Moreover our experimental platform proves that it's an effective method to engineer strain into thin-film solid electrolytes that could be extended to other materials like LLZO or sulfide electrolyte.

Fabrication of amorphous LiPON, LiAlGePO, and GeSn films in low-temperature plasma sputtering process for all-solid-state Li+-ion battery

Plasma-sputtered amorphous films for all-solid-state Li+-ion batteries are investigated. In LiPON electrolyte films, the amount of N incorporated into LiPO films is controlled by the sputtering discharge gas. Ionic conductivity increases with increasing N2 gas proportion in Ar/N2 discharge, reaching a maximum of 2.7 × 10−6 S cm−1 at Li2.39PO3.71N0.13. In amorphous LiAlGePO electrolyte films, the amounts of Al and Ge incorporated into LiPO films are controlled in a combinatorial approach using two-source co-sputtering. The P/Ge ratio varies over a wide range from 23.3 to 1.61 at the radial substrate positions, and the highest ionic conductivity of 4.32 × 10−5 S cm−1 is achieved at Li4.80Al0.80Ge1.16P3O13.1. We evaluate all-solid-state Li+-ion batteries fabricated using the developed amorphous LiPON electrolyte and GeSn anode films, where GeSn films with about 50 nm nanograins are fabricated by high-gas-pressure sputtering at 500 mTorr. A maximum capacity of 2.86 μAh cm−2 is attained for all-solid state Li+-ion battery.

Amorphous Lithium Aluminate As Solid Electrolyte Produced By Pulsed Laser Deposition

Solid state batteries are deemed to become the cornerstone of the future electric mobility. Nevertheless, research on solid electrolytes is still ongoing due the many limitations of current polycrystalline materials. The isotropic and non-periodic structure of amorphous ceramics have shown to contribute to increase the overall ionic conductivity of the material by decreasing the grain-boundary resistive contribution. At the current state, the most promising amorphous material happened to be lithium phosphate oxynitride LiPON (σLi = 10-6 S/cm, ), which demonstrates that the absence of grain boundaries, allows the formation of lithium small dendrites which can grow inside the material without cracking it, avoiding short life cycle of the battery over high current densities [1]. Gao et al. [2] addressed the limited ionic conductivity of LiPON to the strong bond between the PO 4- group with Li+: for this reason, elements with weaker electronegativity than P, such as Al, can generate an ionic bond with O with weaker electrostatic force, regulating the kinetics of Li+ transport and speeds up the diffusion process [3]. In this scenario, Lithium Aluminate (LiAlO2) and Nitrogen-doped Lithium Aluminate (LiAlON) result in a competitive position for the development of an innovative amorphous-glassy electrolyte: very few studies have been conducted on the development of lithium aluminate based solid electrolytes at the present time, mainly due to its low processability at the amorphous phase and the low ionic conductivity of the crystalline phase, more common in the traditional sintering processes.In this study, we demonstrate for the first time the possibility to obtain with Pulsed Laser Deposition (PLD), a completely amorphous LiAlO2 solid electrolyte with a room temperature ionic conductivity of 10-10 S/cm. Thanks to the PLD processing, the grade of polymorphism can be easily controlled as well as film thickness range (10nm up to 10um) and film porosity. By controlling the deposition atmosphere, different content of nitrogen doping has been achieved, promoting the formation of the highly ionic conductive LiAlON (almost two order of higher conductivity). Electrochemical analysis such as DC polarization and Impedance Spectroscopy, revealed the wide electrochemical voltage stability against lithium metal and the high ionic conductivity of the solid electrolyte. A multi-layer approach for the direct deposition of the solid electrolyte over lithium metal surface is proposed, allowing the realization of symmetric cell test and plating/stripping test. Good protection of Li metal substrate has been observed from the LiAlO2 SSE over 24h, hindering oxidation and degradation of the sample.[1] - Nowak, Berkemeier, and Schmitz, “Ultra-Thin LiPON Films – Fundamental Properties and Application in Solid State Thin Film Model Batteries.”[2] - Gao et al., “Screening Possible Solid Electrolytes by Calculating the Conduction Pathways Using Bond Valence Method.”[3] - Guan et al., “Superior Ionic Conduction in LiAlO 2 Thin-Film Enabled by Triply Coordinated Nitrogen.”

High performance all-solid-state lithium battery: Assessment of the temperature dependence of Li diffusion

All-solid-state silicon/LiPON/lithium model batteries are assembled via magnetron sputtering followed by a lithium evaporation process. The cells were characterized via cyclic voltammetry, linear sweep voltammetry and impedance spectroscopy. Cyclic voltammetry confirms a long-term stability and high coulombic efficiency of the solid cells. Also, the assembled batteries were tested at extraordinary high scan rates, showing remarkably high output currents and an exceptional fast-cycling capability. Further rate-dependent investigations via linear sweep voltammetry indicate clearly two different ion-transport mechanisms in the silicon electrode at low and high scan rates. While a diffusion-controlled mechanism is suggested at high scan rates, a homogenous concentration profile is expected at extremely low rates. As a decisive advantage of solid-state cells, electrochemical cycling can be performed at elevated temperatures. This is used to determine the temperature dependence of the diffusion coefficients of lithium in the silicon electrode from room temperature to 165 °C. The effective activation energy of the lithium-ion migration in silicon is obtained to 0.1 eV, which is remarkably lower than that of inside LiPON, i.e. 0.55 eV. Complementary impedance data reveal that the kinetics of transport in the solid-state setup at very high output currents and low temperatures is controlled by lithium-ion migration in the LiPON film. • High rate capability and temperature durability of solid-state battery are shown. • Long-term stability and high coulombic efficiency are demonstrated. • Lithiation of silicon exhibits different kinetic regimes at low and high scan rates. • Temperature dependence of diffusion coefficients of lithium in Si was determined.

In Situ and Ex Situ diagnostics of ALD-Ultrathin Lithium-Ion Films

All solid-state ion layers has an ever-growing interest in order to accomplish on-chip energy storage devices. As such, lithium-ion synaptic transistor to build artificial neural networks, integrated area-enhanced capacitors and lithium-ion microbatteries for energy supply are suitable candidates fulfilling energy-efficient devices. Atomic layer deposition (ALD) is one of the most promising techniques for manufacturing ultrathin layers for lithium-ion devices with exceptional capabilities to enable conformal growth at atomic scale. In this area, in situ diagnostics has become of vital importance for the growth process understanding especially on view of the air-sensitivity character of lithium ultra-thin layers.The purpose of this work is to present an in situ spectroscopic ellipsometry (SE) study of ALD thin films used on the fabrication of lithium-ion devices. We will consider several aspects of ALD ultrathin films growth, such as film thickness, saturation curves and initial films nucleation. We shall compare in situ SE results with those of ex situ diagnostics such as XRR (x-ray reflectometry) and XPS (x-ray photoelectron spectroscopy).We focus on the characterization of 10-100 nm thin lithium phosphate electrolyte with and without nitrogen doping deposited at ALD temperature range 300-350°C using LiHMDS-TMPO and LiHMDS-DEPA precursors, respectively. On the other hand, the realization of silicon integrated lithium ionic devices requires the implementation of essential barrier films to prevent Li-ion into the Si substrate. We will explore here the ability of titanium nitride depositions to act as lithium-ion diffusion barriers. TiN deposition (10-20 nm thin) by ALD process (350°C-400°C) uses TiCl4 and NH3 precursors.First, we investigate the growth process of LiPO, LiPON and TiN intrinsic layers deposited using thermal ALD. Secondly, we apply in situ and ex situ diagnostics on exemplary LiPO/LiPON deposited on top of the 10 nm ALD TiN film (Figure 1: Monitoring of LiPON thickness vs deposition time using in-situ Ellipsometry). The film thickness deduced from in situ SE measurements was corroborated by thickness measurements with XRR technique (Figure 2: Evolution of LiPON thickness vs ALD cycles using Ellipsometry and SE characterization techniques). Ex situ SE was used most often for WiW uniformity evaluating (Figure 3: 8” Wafer thickness mapping of ALD LiPON layers (a: 10nm TiN film; b: 17nm LiPON film). The preliminary results underline the fact that ALD growth rate and nucleation of lithium electrolyte and titanium nitride obviously depends on the ALD process parameters (temperature, pulse and purge times, number of cycles) but on the substrate nature (silicon, thermal oxide, and metallic). In situ and ex situ diagnostics highlight that initial film growth of lithium electrolytes and TiN layers strongly depends on the precursors kind used in the ALD process and the substrate material employed. Figure 1

(Invited) Oxide-Based All-Solid-State Batteries Prepared By Aerosol Deposition

Oxide-based all-solid-state batteries (OX-SSBs) have been expected as next generation rechargeable batteries. Although various kinds of high Li+ conductive solid electrolytes have been prepared such as Li7La3Zr2O12 (LLZ), NASICON-structured Li1.3Al0.3Ti2(PO4)3 (LATP), LiTaPO4 etc, there are serious problems to develop low-resistive positive electrode/high Li+ conductive solid electrolyte interface. Because these high Li+ conductive solid electrolytes are crystallized at 800-1000 ℃, high temperature sintering is common way to combine them with conventional crystalline insertion electrode materials (LiCoO2 (LCO), LiNi1/3Co1/3Mn1/3O2 (NCM111) etc). However, both electrodes and solid electrolytes are composed of different elements with different concentrations, such high temperature sintering process frequently provide mutual diffusion region around the interface in addition to structural degradation and then seriously impede the interfacial resistance. Thus, one strategy to prevent those side reactions will be to apply low temperature sintering or densification process. We have focused on aerosol deposition, AD, a room temperature ceramic coating process. AD can realize quick speed and wide area ceramic coating and has been estimated as a cost-effective process technology for oxide-based energy conversion devices. AD make it possible to prepare electrode-solid electrolyte composite electrodes at room temperature and LiCoO2 film electrode on LiPON film. In addition, AD enables us to investigate the effects of annealing temperature on the interfacial resistances and then limiting temperature for sintering.In this presentation, our recent works on Ox-SSBs using the AD will be introduced 1) 4V- and 5V-class bulk-type Ox-SSBs, 2) effects of annealing temperature on interfacial resistivity, an example of LCO-LATP system to determine limiting temperature for sintering.

Ultrathin RF-Sputtered Lipon Layers for Conformal Lithium Deposition

The transformation from liquid-based Li-ion batteries to solid-state Li-metal batteries is a necessary step to achieve beyond energy densities of 1000 Wh/L. However, the commercial widespread application of the solid-state Li-metal batteries has been hindered by several electrolyte constraints, among which narrow electrochemical window and low compatibility against metallic lithium as negative electrode. Among the various solid-state electrolytes, nitrogen doped lithium phosphate glass or LiPON is a well-known material with an excellent electrochemical stability above 5 V and a good compatibility against metallic lithium [1]. However, owing to its low ionic conductivity (~10-6 S/cm), application of LiPON is limited for thin-film batteries in medical implants and various sensor systems. For thin-film batteries, because the path length for Li+ ion diffusion is in the order of few 100 nm or less, low conductivity of LiPON is enough for application. LiPON has also been evaluated as solid-electrolyte coatings on electrode particles as buffer layer between active material and the bulk electrolyte. In a thin-film stack, it is an ideal model system for electrochemical study.Previously, we investigated detailed electrochemistry of RF-sputtered LiPON thin films with different thickness [2]. We demonstrated formation of an electronically insulating LiPON films down to 15 nm with a maximum conductivity of 1×10-6 S/cm. We have also formulated a breakdown mechanism for LiPON layer based on experimental measurements and thermodynamic considerations. In the present work, we investigated LiPON thin-films as artificial solid-electrolyte interphase for lithium plating and stripping on copper current collectors. The stability of 100 nm down to 10 nm LiPON thin-films was evaluated by electrochemical galvanostatic cycling test of Li plating/stripping with carbonate-based electrolyte. The LiPON thin-film with 100 nm showed reversible plating/stripping of Li with an overpotential of only ~40 mV for current density of 0.1 mA/cm2 for over 100 cycles, indicating formation of a uniform Li layer in-between substrate and LiPON without breaking of LiPON layer during the cycles. Furthermore, even with the thickness of only 10 nm, LiPON thin-film demonstrated significant improvement of coulombic efficiency of Li plating/stripping compared to without LiPON layer. In the presentation, thickness-dependence of LiPON on growth behavior of Li will be further discussed. Reference [1] X. Yu, J. B. Bates, G. E. Jellison, Jr., and F. X. Hart, J. Electrochem. Soc., 144 (1997) 524-532.[2] B. Put; P.M. Vereecken; J. Meersschaut; A. Sepúlveda; A. Stesmans, ACS Appl. Mater. Interfaces., 8 (2016) 7060-7069.

Local Structure of Glassy Lithium Phosphorus Oxynitride Thin Films: A Combined Experimental and Ab Initio Approach

AbstractLithium 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.

(Invited) Lithium Batteries Enabled By Thin Film Composite Solid Electrolyte Separators

Over the past decade, solid-state lithium ion conductors with conductivities on par and even exceeding the conductivities of conventional liquid electrolytes have been developed. However, practical solid-state lithium metal batteries have not yet been realized due to challenges associated with fabricating and integrating solid electrolyte separators into electrochemical cells. To achieve the power metrics and effective energy densities of existing lithium ion cells, solid electrolytes must be fabricated with comparable area specific resistances and thicknesses on the order of 10 μm, without a significant increase in cost. Thin film composite separators, where a dense solid electrolyte film is coated onto microporous membranes (separators), are one possible solution. The solid thin film electrolyte enables reversible cycling of Li metal by isolating it from the catholyte and inhibiting growth of dendritic structures, while the porous scaffold mechanically supports the thin film and hosts the catholyte within its porosity for efficient ion transport.In this work, lithium phosphate oxynitride (Lipon) thin films with thicknesses on the order of 50 - 100 nm were deposited onto microporous polypropylene separators. These composite separators were robust and flexible; the Lipon film didn’t fracture as the separator was handled, enabling the integration into standard lithium cells, such as coin cells. Due to its thinness, the area specific resistance (ASR) of the solid electrolyte layer was 5 - 10 Ω-cm2, and a relatively low interfacial resistance of 2.5 Ω-cm2 between the Lipon and liquid electrolyte was observed. The Lipon layer was shown to be chemically and physically stable in several common liquid electrolyte formulations. Negligible evolution of interfacial resistance and reaction products at the Lipon/liquid electrolyte were observed after extended exposure to these electrolytes. In Li cycling tests, the Lipon layer promoted smooth, dense Li morphologies in electrodeposits with areal capacities exceeding 15 mAh cm-2. Without the dense Lipon layer, the morphology of the Li electrodeposits was rough – consistent with “mossy” lithium morphology typically observed in liquid electrolytes. In operando impedance spectroscopy showed that a stable resistance of the Lipon bulk was maintained during Li plating, suggesting that the Lipon layer remains intact. The solid electrolyte membrane was also shown to inhibit the polysulfide shuttle in Li-S cells, preventing the reaction of the polysulfide with Li metal. The Li-S cell using the composite separators showed high coulombic efficiency and stable cycling performance. In LiMn2O4-Li cells, the thin film composite separators protected the Li metal from reactions with Mn ions dissolved in liquid electrolyte. The development of these composite solid electrolyte separator offers a promising path to energy dense lithium metal batteries. This work was supported by the ARPA-E IONICS program, U.S. Department of Energy, award DE-AR0000775.

All solid-state thin-film lithium-ion battery with Ti/ZnO/LiPON/LiMn2O4/Ti structure fabricated by magnetron sputtering

An all solid-state thin-film Lithium-ion Battery with Ti/ZnO/LiPON/LiMn2O4/Ti structure was successfully deposited on the glass substrate by magnetron sputtering without any heat treatments. With the protection of LiPON films, the cell formed by crystal ZnO, amorphous LiPON and LiMn2O4, and Ti films presents a stable reversible capacity of 22 μAh/cm2 between 0.5 and 5 V at the current density of 5 μA/cm2 in the air at the room temperature. The microstructure and phase structure of cell were characterized with XRD, SEM and Raman spectroscopy techniques, respectively. Good electrical performance proves it could be useful for low-power thin film battery applications onto lower-temperature substrate materials and battery stacks.

The study of effect of solid electrolyte on charge-discharge characteristics of thin-film lithium-ion batteries

Results of studies of the solid electrolyte effect on capacitance of thin-film electrodes on the basis of Si-O-Al and VxOy nanocomposites are presented. The studies were carried out by comparing the charge-discharge characteristics of two pairs of the identical electrodes, one of which was covered by LiPON film, within prototypes with two lithium electrodes - the counter and the reference electrode.

Development of the Technology of Magnetron Sputtering Deposition of LiPON Films and Investigation of Their Characteristics

The results of developing the technology of magnetron sputtering deposition of a LiPON solid electrolyte and an experimental investigation of its characteristics are presented. The basic processing operations and parameters providing the formation of films of the proper morphology, structure, and elemental and phase composition are described. The data of the measurement of the physical parameters of the films by cyclic voltammetry and potentiometry are represented.

An experimental examination of thin films of lithium phosphorus oxynitride (a solid electrolyte)

The results of examination of thin-film samples of the LiPON solid electrolyte, which were synthesized by magnetron sputtering, are reported. Data on the morphology, structure, elemental and phase composition, and electrophysical parameters of LiPON films are presented.

Electronic Conductivity Measurements for Li x Ni0.45Mn1.5Cr0.05O4 (0 < x < 2) Thin Films

Spinel-structured Li x Ni0.45Mn1.5Cr0.05O4 (LNM) is known as a 5-V-class cathode material [1]. The LNM shows the redox reactions of Ni2+/3+/4+ in the 5 V region with x from 1 to 0. In addition, the redox reactions of Mn3+/4+ take place in the 3 V region with x from 1 to 2. As has been reported by West et al., stable charge-discharge reactions in the 3-5 V region occurs in case of thin-film all-solid-state battery (SSB) using LNM film electrodes, which utilize the capacity of LNM up to 250 mAh g-1 [2]. During these charge-discharge reactions, several phase transition reactions occur and 3 V region shows hysteresis at room temperature. Measuring the electronic conductivity (σ) of LNM is one of the effective approaches to understand this hysteresis mechanism around 3 V region because the σ of LNM will depend on the Li composition and crystal structure. Although electronic conductivity variations of LNM (0<x<1) has been already reported [1], wide compositional range (0<x<2) of the LNM has not been investigated at all. This study investigates the variation of σ with x in LNM films from 0 to 2 as SSB. We used interdigitated array (IDA) electrodes with patterned Pt comb electrodes on quartz substrates for the σ measurements [3]. Thin films of LNM with the thickness of 40 nm were deposited onto the IDA electrodes by pulsed laser deposition (PLD). In case of the conductivity measurements using SSB, both an amorphous Li-P-O (LPO) film and a lithium phosphorus oxynitride glass (LiPON) film were sequentially deposited on the LNM film by PLD and radio frequency (RF) magnetron sputtering, respectively. After that, thin film of Li was deposited on the LiPON film by vacuum evaporation on the LiPON film. Lithium insertion/extraction reactions of LNM films were carried out by the CV at 0.5 mV s-1, and the voltages were maintained at desired points for the σ measurement until the current density decreased below to 10 nA cm-2. After that, the σ in LNM film was measured in-plane direction by electrochemical impedance spectroscopy (EIS). All these experiments were conducted at room temperature (25°C) in an Ar-filled grove box. Figure 1 shows a CV of SSB and σ measured after the voltage of the SSB is maintained at numbered potentials during the CV. The CV started from 3.7 V (No. 1) and was swept to 2.0 V-5.0 V-3.7 V. At initial voltage of 3.7 V, the σ was 1.5 × 10-4 S cm-1. The σ then slightly decreased after the lithium insertion peak A (No. 3) and drastically decreased at 2.0 V after the peak B (No. 4). The decreased σ partially recovered at anodic scan after the peak A’ (No. 6) and the σ gradually increased until the peak B’ (No. 7&8). At higher voltage region (No. 9-14), the σ showed reversible change against Li+ insertion/extraction reactions and finally returned to initial value at 3.7 V (No. 15). Wide-range variations of the σ of LNM film during the charge-discharge reactions were successfully measured as SSB by using IDA electrodes. Same measurements were carried out in liquid electrolyte, but the hysteresis of σ appeared different manner. Based on these data, lithium insertion/extraction reaction at 3-5 V region of LNM will be discussed in the poster session. Reference 1. Z. M. Rosenberg, A. Huq, J. B. Goodenough, and A. Manthiram, Chem. Mater., 27, 6934 (2015). 2. W. C. West, Y. Ishii, M. Kaneko, M. Motoyama, and Y. Iriyama, ECS Electrochem. Lett., 3, A99 (2014). 3. M. Nishizawa, T. Ise, H. Koshika, T. Itoh, and I. Uchida, Chem. Mater., 12, 1367 (2000). Figure 1

Self-Standing All-Solid-State Lithium Battery Prepared By Electrochemical in-Situ Electrode Growth Method

Introduction All-solid-state rechargeable lithium battery (SSB) is one of the candidates for next generation rechargeable batteries. A crucial problem to improve the performance of the SSB will be the reduction of charge-transfer resistance at electrode/solid-electrolyte interface. Here, we focused on partial conversion of solid electrolyte [e.g. Li1.3Al0.3Ti1.7(PO4)3 (LATP)] into electrode active material via electrochemical irreversible Li+ insertion reaction into the LATP, that is, electrode active material grows in-situ from the LATP by electrochemical process. Charge transfer resistance at in-situ formed electrode/LATP is small probably because of well-connected interface without any mutual diffusion layer [1]. However, the growth amount of the in-situ formed electrode was extremely small at room temperature and the growth area was limited only around the LATP/current collector interface. This problem will arise from less electronic conductivity of the in-situ formed electrode material. In this work, in-situ formed electrodes were grown at higher temperatures. These conditions are supposed to be effective to increase the growth amount of in-situ formed electrode because the electronic conductivity increases at higher temperatures. This study focuses on the temperature dependency on the thickness of in-situ formed electrode in the LATP. Experimental A mirror-polished-Li+-conductive-glass-ceramic (LATP; manufactured by OHARA Inc.) sheet with a thickness of 150 µm was used as the solid electrolyte. Lithium phosphorus oxynitride glass electrolyte (LiPON) was deposited on one side of a LATP sheet by RF magnetron sputtering. Thin film of Li was deposited on the LiPON film by vacuum evaporation. The opposite side of the LATP sheet was covered with Au film with a thickness of 100 nm. Eventually, a Li/LiPON/LATP/Au multilayer was fabricated, where electrode area of Au was 0.64 cm2. Electrochemical properties of the resultant cells were measured by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and charge-discharge measurements. Results and Discussion The Li/LiPON/LATP/Au cell delivered a couple of redox peaks at 2.35 V (vs. Li+/Li) in the CV measurements between 3.0 V and 1.5 V as shown in Fig. 1, which was in good agreement with the past work [1]. Initial discharge capacity at 25°C was 45 mC cm-2, which increased with increasing the reaction temperature. At 100°C, the capacity attained to 1250 mC cm-2, ca. 27 times larger value than that at 25°C. This result suggests that the in-situ formed electrode grow deeply inside the LATP sheet at higher temperatures. The growth distance of in-situ formed electrode from the current collector (Au) was ca. 700 nm at room temperature [2]. Thus, the in-situ formed electrode can grow few tens of micron meters from the interface at higher temperatures. To clarify this point, we used thinner LATP sheet (20 μm) alternatively and examined same measurements. At 70°C, all the LATP sheet exchanged to the in-situ formed electrode material though some of cracks were also observed. Electrochemical properties of those batteries will be discussed in the poster session. Reference 1. Y. Amiki, F. Sagane, K. Yamamoto, T. Hirayama, M. Sudoh, M. Motoyama, and Y. Iriyama, J. Power Sources, 241,583 (2013). 2. K. Yamamoto, Y. Iriyama, T. Asaka, T. Hirayama, H. Fujita, K. Nonaka, K. Miyahara, Y. Sugita and Z. Ogumi, Electrochem. Comm., 20, 113 (2012). Figure 1