LiCoO2 Films Research Articles

Graphene coating-modified LiCoO2 films as high-performance cathode material in quasi-solid-state thin-film lithium batteries

LiCoO2 (LCO) films were successfully prepared using a radio frequency magnetron sputtering method, and the interface between the LCO cathode films and Li1.5Al0.5Ge1.5(PO4)3 (LAGP) solid electrolyte was modified by a graphene (G) buffer layer. The composition and morphology of the thin-film samples were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, and scanning electron microscopy. The LCO thin film annealed at 600 °C had excellent charge transport properties, respectively delivering initial charge and discharge specific capacities of 162.7 mAh·g−1 and 124.5 mAh·g−1 at 0.1C in a half-cell structure. Relaxation time distribution reconstruction impedance analysis and rate characteristic analysis of an LCO/G/LAGP/G/LCO symmetric cell demonstrated that the flexible graphene buffer layer effectively improved the contact impedance of the interface and structure stability of the active materials. After cycling for 1000 h at current densities of 0.02 mA·cm−2 and 0.5 mA·cm−2, the LCO/G/LAGP/G/LCO symmetric cell still maintained stable polarization voltages of 0.05 V and 0.7 V, respectively. In addition, an assembled LCO/G/LAGP/Li quasi-solid-state film lithium battery presented an initial discharge specific capacity of 109.53 mAh·g−1 at 0.1C, with a capacity retention rate of 71.86 % after 100 cycles.

Recovery of metal ion resources from waste lithium batteries by in situ electro-leaching coupled with electrochemically switched ion exchange

A new green pathway of in situ electro-leaching coupled with electrochemically switched ion exchange (EL-ESIX) technology was developed for the separation and recovery of valuable metal ions from waste lithium batteries. By using the in situ electro-leaching, the leaching rates of Li+ and Co2+ from the prepared LiCoO2 film electrodes reached 100 % and 93.30 %, respectively, under the combined effect of the acidic microenvironment formed by the anodic electrolytic water and electrostatic repulsion. Subsequently, the Li+ in the electrolyte was further extracted by an electrochemically switched ion exchange (ESIX) process using LiMn2O4 as the film electrode, and Li+ was further enriched in the eluate by a cyclic adsorption and desorption process. The results indicate that the in situ electro-leaching has significant advantages over powder leaching, and for the recycling of waste lithium batteries, the final lithium recovery rate reached 94.51 % by using this in situ EL-ESIX technology.

Redox-based ion-gating reservoir consisting of (104) oriented LiCoO2 film, assisted by physical masking

Reservoir computing (RC) is a machine learning framework suitable for processing time series data, and is a computationally inexpensive and fast learning model. A physical reservoir is a hardware implementation of RC using a physical system, which is expected to become the social infrastructure of a data society that needs to process vast amounts of information. Ion-gating reservoirs (IGR) are compact and suitable for integration with various physical reservoirs, but the prediction accuracy and operating speed of redox-IGRs using WO3 as the channel are not sufficient due to irreversible Li+ trapping in the WO3 matrix during operation. Here, in order to enhance the computation performance of redox-IGRs, we developed a redox-based IGR using a (104) oriented LiCoO2 thin film with high electronic and ionic conductivity as a trap-free channel material. The subject IGR utilizes resistance change that is due to a redox reaction (LiCoO2 ⟺ Li1−xCoO2 + xLi+ + xe−) with the insertion and desertion of Li+. The prediction error in the subject IGR was reduced by 72% and the operation speed was increased by 4 times compared to the previously reported WO3, which changes are due to the nonlinear and reversible electrical response of LiCoO2 and the high dimensionality enhanced by a newly developed physical masking technique. This study has demonstrated the possibility of developing high-performance IGRs by utilizing materials with stronger nonlinearity and by increasing output dimensionality.

Fast Lithium Intercalation Mechanism on Surface‐Modified Cathodes for Lithium‐Ion Batteries

AbstractEnhancing the understanding of fast lithium intercalation on cathode surfaces modified by oxides is crucial for the development of electrode materials that offer high‐power and long‐life operation. Herein, lithium transfer is elucidated by directly observing the structural changes within the cathode, through the interface, and into the electrolyte using in situ neutron reflectometry (NR). Two films are studied—a Li2ZrO3‐modified and an unmodified LiCoO2 film—and it is found that the modified film exhibits a superior rate capability. In situ NR studies indicate that the surface modification facilitates the formation of a dense cathode–electrolyte interphase (CEI), primarily composed of inorganic species. In contrast, the unmodified surface is covered by a relatively sparse and electrolyte‐impregnated CEI. These structural observations suggest that lithium desolvation during intercalation primarily occurs on the CEI and LiCoO2 surfaces for the modified and unmodified films, respectively. Fast desolvation of lithium on the CEI may contribute to the superior rate capability of the surface‐modified cathodes. This suggests a mechanism of fast intercalation achieved by surface modification of low ionically conductive oxides. Simultaneous chemical composition and morphological information is a powerful way to elucidate the dynamics at cathode/liquid electrolyte interfaces suitable for high‐power operation.

Physical Delithiation of Epitaxial LiCoO2 Battery Cathodes as a Platform for Surface Electronic Structure Investigation.

We report a novel delithiation process for epitaxial thin films of LiCoO2(001) cathodes using only physical methods, based on ion sputtering and annealing cycles. Preferential Li sputtering followed by annealing produces a surface layer with a Li molar fraction in the range 0.5 < x < 1, characterized by good crystalline quality. This delithiation procedure allows the unambiguous identification of the effects of Li extraction without chemical byproducts and experimental complications caused by electrolyte interaction with the LiCoO2 surface. An analysis by X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy (XAS) provides a detailed description of the delithiation process and the role of O and Co atoms in charge compensation. We observe the simultaneous formation of Co4+ ions and of holes localized near O atoms upon Li removal, while the surface shows a (2 × 1) reconstruction. The delithiation method described here can be applied to other crystalline battery elements and provide information on their properties that is otherwise difficult to obtain.

(Industrial Electrochemistry and Electrochemical Engineering Division H. H. Dow Memorial Student Achievement Award) Electrochemically Grown Highly Textured Thick Ceramic Oxide Films for Energy Storage: A New Manufacturing Paradigm for Cathode Materials

Electrochemical synthesis of materials has contributed to significant breakthroughs in materials processing by replacing high temperature, cost and energy intensive pyrometallurgical processes. Noteworthy examples include aluminum extraction by Hall–Heroult process, electrowinning of copper, titanium extraction through the Kroll process, electrolytic production of steel, and electrochemical synthesis of cement. Increasing the energy and power density of alkali ion intercalated transition metal oxide cathodes which power electric cars and portable electronics, has been a growing topic of global techno-economic interest. Our work demonstrates a direct electrodeposition of thick ternary ceramic oxide films as an alternate scalable manufacturing technique for fabrication of binder-and-additive free cathode materials for secondary battery. Employing an intermediate temperature (200-400°C) molten hydroxide-based electrodeposition method, a general electrochemical growth strategy for multiple Li and Na ion cathode chemistries is demonstrated for the first time including NaCoO2, NaMnO2, LiCoO2, Li2MnO3, LiMnO2, LiMn2O4, (A. Patra, P.V. Braun et. al, PNAS, 2021) in a thick (> 50 µm) thick film form factor. In-plane and through-plane texture can be electrochemically architectured in LiCoO2 and NaCoO2 films across multiple textures: <003>||ND (Li/Na ion blocking sites parallel to the normal direction), <101>||ND, <104>||ND, <110>||ND (fast lithium ion conducting sites parallel to the normal direction). An accurate control of crystallization dynamics leads to highly anisotropic, grain boundary engineered structure with low tortuosity and fastest electron and Li ion conducting pathways (<110>||ND) oriented normal to the current collector. The highly textured (<110>||ND), dense (>95%) electroplated cathodes can perform even at ultrahigh thickness of ~ 200 µm (areal capacity of ~13.6 mAh/cm2) in comparison to 40-60 µm for conventional slurry cast cathodes (areal capacity of ~3-4 mAh/cm2 with a porosity of ~10-20%), a fivefold increase in areal capacity and volumetric energy density (A. Patra, P.V. Braun et. al, to be submitted). In order to enable a high voltage (> 4.5 V vs. Li) cathode design, a functionally graded architecture is also demonstrated with a core capable of providing high-capacity and rate capability (LCO <110>||ND); and multiple capping layers (LCO <003>||ND and Li2MnO3) to suppress harmful side reactions occurring at voltages beyond the normal operation range (beyond 4.2 V vs. Li). Our work paves the way towards an electrosynthesis platform for functional oxides with the ability to generate micron scale ordering with controllable in-and-through-plane orientation in thick ceramic oxide films important for electrochemical energy storage.

Thermodynamics as a Driving Factor of LiCoO2 Grain Growth on Nanocrystalline Ta-LLZO Thin Films for All-Solid-State Batteries.

All-solid-state batteries primarily focus on macrocrystalline solid electrolyte/cathode interfaces, and little is explored on the growth and stability of nanograined Li-garnet and cathode ones. In this work, a thin (∼500 nm) film of LiCoO2 (LCO) has been grown on top of the polycrystalline layer of Ta-doped Li7La3Zr2O12 (Ta-LLZO) solid electrolyte using the pulsed laser deposition (PLD) technique. Scanning transmission electron microscopy, electron diffraction, and electron tomography demonstrated that the LCO film is formed by columnar elements with the shape of inverted cones. The film appears to be highly textured, with the (003) LCO crystal planes parallel to the LCO/Ta-LLZO interface and with internal pores shaped by the {104} and {102} planes. According to density functional theory (DFT) calculations, this specific microstructure is governed by a competition between free energies of the corresponding crystal planes, which in turn depends on the oxygen and lithium chemical potentials during the deposition, indicating that thermodynamics plays an important role in the resulting LCO microstructure even under nonequilibrium PLD conditions. Based on the thermodynamic estimates, the experimental conditions within the LCO stability domain are proposed for the preferential {104} LCO orientation, which is considered favorable for enhanced Li diffusion in the positive electrode layers of all-solid-state batteries.

Enhanced Interfacial Kinetics and High Rate Performance of LiCoO2 Thin-Film Electrodes by Al Doping and In Situ Al2O3 Coating.

The structure and surface-interface instability of LiCoO2 thin-film electrodes during charge–discharge cycles are one of the main factors leading to the deterioration of electrochemical performance. Element doping and surface coating are effective strategies to tackle this issue. In this work, Al-doped and in situ Al2O3-coated LiCoO2 composite thin-film electrodes are prepared by magnetron sputtering. The results show that the resultant composite thin-film electrodes exhibited excellent cycling stability, with a discharge specific capacity of 40.2 μAh um–1 cm–2 after 240 cycles at 2.5 μA cm–2, with a capacity retention rate of 94.14%, compared to a discharge capacity of the unmodified sample of only 37.7 μAh um–1 cm–2 after 110 cycles, with a capacity retention rate of 80.04%. In addition, the rate performance of the prepared LiCoO2 film is significantly improved, and the discharge specific capacity of the Al-doped sample reaches 43.5 μAh um–1 cm–2 at 100 μA cm–2, which is 38.97% higher than that of the unmodified sample (31.3 μAh um–1 cm–2). The enhancement of electrochemical performance is mainly attributed to the synergistic effect of Al doping and in situ Al2O3 coating. The metal Al forms a conductive network in the film, while part of the Al will enter the LiCoO2 lattice to form a LiAlyCo1–yO2 solid solution, promoting the transport of lithium ions and improving the stability of the electrode structure. The in situ continuous deposition of the coating optimizes the active material coating–electrolyte interface.

Degradation Mechanism of All-Solid-State Li-Metal Batteries Studied by Electrochemical Impedance Spectroscopy.

Solid-state Li-metal batteries have the potential to achieve both high safety and high energy densities. Among various solid-state fast-ion conductors, the garnet-type Li7La3Zr2O12 (LLZO) is one of the few that are stable to Li metal. However, the large interfacial resistance between LLZO and cathode materials severely limits the practical application of LLZO. Here a LiCoO2 (LCO) film was deposited onto an Al-doped LLZO substrate at room temperature by aerosol deposition, and a low interfacial resistance was achieved. The LCO particles were precoated by Li3BO3 (LBO), which melted to join the LCO particles to the LLZO substrate at heating. All-solid-state Li/LLZO/LBO-LCO cells could deliver an initial discharge capacity of 128 mAh g–1 at 0.2 C and 60 °C and demonstrated relatively high capacity retention of 87% after 30 cycles. The cell degradation mechanism was studied by electrochemical impedance spectroscopy (EIS) and was found to be mainly related to the increase of the interfacial resistance between LBO and LCO. In-situ SEM analysis verified the hypothesis that the increase of the interfacial resistance was caused primarily by interfacial cracking upon cycling. This study demonstrated the capability of EIS as a powerful nondestructive in-situ technique to investigate the failure mechanisms of all-solid-state batteries.

Annealing Optimization of Lithium Cobalt Oxide Thin Film for Use as a Cathode in Lithium-Ion Microbatteries.

The microbatteries field is an important direction of energy storage systems, requiring the careful miniaturization of existing materials while maintaining their properties. Over recent decades, LiCoO2 has attracted considerable attention as cathode materials for lithium-ion batteries due to its promising electrochemical properties for high-performance batteries. In this work, the thin films of LiCoO2 were obtained by radio-frequency magnetron sputtering of the corresponding target. In order to obtain the desired crystal structure, the parameters such as annealing time, temperature, and heating rate were varied and found to influence the rhombohedral phase formation. The electrochemical performances of the prepared thin films were examined as a function of annealing time, temperature, and heating rate. The LiCoO2 thin film cathode annealed at 550 °C for 1 h 20 min demonstrated the best cycling performance with a discharge specific capacity of around 135 mAh g−1 and volumetric capacity of 50 µAh cm−2µm−1 with a 77% retention at 0.5 C rate.

Sputter-Deposited Amorphous Li3PO4 Solid Electrolyte Films.

This paper reports the thin-film synthesis of Li3PO4 solid electrolytes by RF magnetron sputtering. A relatively high ionic conductivity of more than 1 × 10–6 S cm–1 is achieved. It is revealed that the crystallization of Li3PO4 impedes ionic conduction, and a moderate amount of O2 addition to Ar suppresses the crystallization and guarantees long-term deposition. Another important finding in this study is that when Li3PO4 is deposited on a LiCoO2 film to construct a thin-film battery, the LiCoO2 film can be damaged depending on the substrate bias potential relative to the cathode potential propagated through the sputtering plasma. Active control of the bias potential to avoid the damage realizes negligible interface resistance in the thin-film battery.

Rapid thermal sintering of screen-printed LiCoO2 films

A rapid photonic sintering process (rapid thermal processing) was used to obtain compact films of cathode active material of lithium batteries. LiCoO2 (LCO) thick films were screen-printed on a steel substrate followed by a contactless thermal processing at 1000 °C in only 90 s. A homogenous densification of such layers could be verified by scanning electron microscopy, while the structural consistency of the LCO phase in these layers could be detected by X-ray diffraction and Raman spectroscopy. Furthermore, electrochemical activity of the layer was confirmed by electrochemical cell tests with a liquid electrolyte.

Optimization of a potential manufacturing process for thin-film LiCoO2 cathodes

A radio frequency (RF) magnetron sputter deposition process designed for low-cost, high-rate fabrication of LiCoO2 (LCO) thin films was developed and used to fabricate approximately phase pure cathodes with the R3¯m crystal structure, strong (104) preferred orientation and high discharge capacities. Starting from a typical set of processing conditions for LCO films, the values of key deposition and post-deposition parameters were systematically changed to increase the deposition rate, simplify the sputter deposition process and minimize process gas use without compromising the structural properties and electrochemical performance. Cathodes were deposited onto Waspaloy (58Ni-19Cr-14Co-Mo-Ti-Al-Fe [wt%]) foil current collectors to provide enhanced thermal stability during post-deposition annealing. The best properties were attained using a process pressure of 0.5 Pa, an RF power density of 5.5 W cm−2 and a post-deposition anneal in air at 600 °C for 2 h. A sintered sputter target, oxygen gas flow and substrate heating were not required. This set of conditions resulted in a high deposition rate of ∼700–790 nm h−1, allowing the formation of a relatively thick (∼2.8–3.2 µm) film in 4 h. Furthermore, high maximum specific and areal discharge capacities of 132 mAh g−1 / 62 µAh cm−2µm−1 and 172 μAh cm−2 were attained during galvanostatic cycling at a rate of 0.1 C with an organic liquid electrolyte, which are among the highest values reported. Cycling rate tests showed that the thin-film LCO cathodes could deliver capacity up to a cycling rate of at least 2 C without causing any significant cell damage.

Low-Temperature Laser Synthesis of LiCoO2 and WO3 Films for Electrochromic Application

Low-Temperature Laser Synthesis of LiCoO2 and WO3 Films for Electrochromic Application

Flash Lamp Annealing Enables Thin-Film Solid-State Batteries on Aluminum Foil

Crystallization of cathode films in solid-state microbatteries requires thermal annealing at high temperatures, restricting the choice of substrate and current collector materials. Here, flash lamp annealing (FLA) is explored to crystallize LiCoO2 (LCO) cathodes on aluminum foils. Millisecond pulses of visible light induce rapid heating of the LCO films up to 900 °C, whereas the aluminum never exceeds the melting point. Microbatteries consisting of an FLA-processed LCO cathode, a LiPON electrolyte, and a Li metal anode are fabricated on flexible aluminum foil, with performance comparable to those on rigid silicon. This method can enable new microbattery designs at lower production costs.

Controllable preparation and electrochemical properties of In-situ annealed LiCoO2 films with a specific crystalline orientation on stainless steel substrates

The crystallization characteristics of LiCoO2 (LCO) thin films are key factors that affect the electrochemical properties of films. In this paper, in-situ annealed LCO films with a specific crystalline orientation were prepared on stainless steel (SS) substrates by radio-frequency (RF) magnetron sputtering. The effects of the high-temperature pretreatment of the SS substrate, substrate temperature and sputtering power on the crystallization and electrochemical properties of the LCO films were investigated in detail. It was found that the structure of the SS substrate was transformed from the γ phase to the δ phase after the high-temperature pretreatment, and the crystallization orientation of the LCO films could be induced by the different SS phase structures. The crystallization characteristics of the LCO films were also clearly influenced by the substrate temperature. The crystallization orientation changed from the (003) orientation to the (101) orientation when the temperature increased to a high degree, but too high of a substrate temperature (such as 600 °C) ruptured the films. The discharge specific capacity of the LCO films increased with an increasing substrate temperature, showing a capacity of 53.8 μAh cm−2 μm−1 at 550 °C and exhibiting good cycling stability. At this temperature, the crystal orientation could be controlled by adjusting the sputtering power to avoid rupturing the thin films, thereby achieving high-quality LCO films with a specific orientation. The LCO films prepared at 120 and 200 W showed obvious (101) and (003) preferred orientations, respectively. The galvanostatic charge-discharge tests showed that the (101) preferred orientation film exhibited a large initial discharge capacity of 57 μAh cm−2 μm−1, but its cycling performance was poor. The (003) preferred orientation delivered a superior cycling performance with an initial discharge capacity of 55.6 μAh cm−2 μm−1 and a capacity retention of 72% after 150 cycles. Cyclic voltammetry and electrochemical impedance spectroscopy measurements showed that the (101) preferred orientation was more conducive to the full infiltration of the electrolyte and the transport of lithium ions, but the stability of the structure and surface was poor and the impedance clearly increased during cycling. The (003) preferred orientation exhibited better structural and surface stability and exhibited better lithium-ion diffusion after repeated electrochemical processes.

Low‐Resistive LiCoO2/Li1.3Al0.3Ti2(PO4)3 Interface Formation by Low‐Temperature Annealing Using Aerosol Deposition

Interfacial resistance at electrode‐high Li+ conductive solid electrolytes must be reduced well to develop high‐power all‐solid‐state batteries using oxide‐based solid electrolytes (Ox‐SSBs). Herein, crystalline electrode films of LiCoO2 (LCO) are formed on a high Li+ conductive crystalline‐glass solid electrolyte sheet, Li1.3Al0.3Ti2(PO4)3 (LATP) (σ25 °C = 1 × 10−4 S cm−1), at room temperature by aerosol deposition (AD), and the effects of the annealing temperature on the interfacial resistivities (Rint) at the LCO/LATP are investigated. The Rint visibly increases by annealing over 500 °C with the growth of Co3O4 as a reactant. In contrast, Rint is reduced to ≈100 Ω cm2 by low‐temperature annealing at 250–350 °C due to superior contact through the structural rearrangement of an artificial metastable interface formed by the AD. These results are applied to bulk‐type Ox‐SSB, Li/Li7La3Zr2O12(LLZ)/LCO–LATP, and our best Ox‐SSB delivers a discharge capacity of 100 mA cm−2 at 100 °C.

Switching Response of Hydrogen-Terminated-Diamond-Based All-Solid-State Electric-Double-Layer Transistor

INTRODUCTION High-density electronic carrier control using an electric double layer (EDL) at electrolyte/electrode interfaces has been attracting attention for the application in various electronic devices. Specifically, the use of solid electrolyte is advantageous for practical use owing to its high compatibility with other peripheral devices.Recently, we have achieved an in situ modulation of hole density in hydrogen-terminated diamond (H-terminated diamond) using an all-solid-state electric double layer transistor (EDLT) [1]. The hole density increased from 1010 cm-2 to 1013 cm-2, a 3-order-of-magnitude difference, applying a negative gate voltage (V G). This indicates that the two-dimensional hole gas was electrostatically modulated by EDL charging at the solid electrolyte/H-terminated diamond interface. Then, we focus on a switching response speed, which is an important parameter for EDLTs. Towards further development of all-solid-state EDLTs for practical use, high switching response is desired. Because diamond is suitable for high-frequency electronic device owing to its high carrier mobility, diamond-based all-solid-state EDLT is a candidate to exceed the response speed of conventional all-solid-state EDLTs EXPERIMENTAL An H-terminated diamond thin film was homoepitaxially grown on the surface of an Ib-type HPHT diamond single crystal (100) using microwave plasma chemical vapor deposition. The channel area was fabricated by photolithography, and O2 plasma ashing. Source and drain electrodes were made of Pt/Pd. Gate electrode was made of LiCoO2 (LCO) and Pt films. We chose a Li+ conducting Li2O-ZrO2-SiO2 (LZSO) amorphous thin film as a solid-state-electrolyte. To compare response speed, we also fabricated EDLT with the same structure except for the gate electrode. The gate electrode of another EDLT was made of Au. Electrochemical measurements were performed using a Keithley 4200-SCS parameter analyzer and an atmosphere/temperature tunable prober system (Nagase). RESULTS AND DISCUSSION Figure 1 shows the switching characteristics of EDLTs measured at the drain voltage of 0.5 V. The measurements were performed in steps of 2 K. When a pulse (V G) is applied, drain current (i D) instantaneously decreases from the 10 microampere order to less than 10 nanoampere order. Thus, EDLTs are switched from an on-state to off-state. As explained in the introduction, this is attributed to the effect of EDL charging at the LZSO solid electrolyte/H-terminated diamond interface. In both EDLTs, the response time is shorter than 50 ms at 298 K. Because the speed is not affected even when the type of the gate electrode was changed, the effect of EDL charge and discharge at the LZSO/LCO interface can be ignored. Therefore, this response speed mainly resulted from EDL charge and discharge processes at the LZSO/H-terminated diamond interface. The response speed becomes faster with an increase in the temperature. This is attributed to an increase in the Li+ conductivity of LZSO. The conductivity of LZSO exhibited a thermally activated behavior with an activation energy of 0.66 eV; the conductivity of LZSO increased from 8×10-9 S/cm at 298 K to 2×10-7 S/cm at 340 K. Although the conductivity of the H-terminated diamond channel changed with an increase in the temperature, the variation was about 25%, which is sufficiently small compared to the variation in that of LZSO. Therefore, the rate of the response speed in EDLTs is determined by the conductivity of LZSO. At 340 K (Li+ conductivity: 2×10-7 S/cm), EDLTs show the response time of less than 800 μs. Thus, H-terminated diamond-based all-solid-state EDLT has a potential for ultrafast switching even at room temperature if an electrolyte with better conductivity is used. Since RbAg4I5 Ag+ superionic conductor (0.12 S/cm at RT [2]) was previously reported as an electrolyte for EDL capacitors [3], RbAg4I5 is a good candidate for ultrafast EDLTs, of which the response speed is expected to exceed 1 GHz.In the presentation, we will show the switching characteristics for H-terminated diamond-based all-solid-state EDLTs using various solid electrolytes. Acknowledgements This work was in part supported by JSPS KAKENHI Grant Number JP20H05816 (Grant-in-Aid for Scientific Research on Innovative Areas “Interface Ionics”), JP19K05279 and JP19J22244 (Grant-in-Aid for JSPS Fellows). REFERENCES [1] T. Tsuchiya, M. Takayanagi, M. Imura, Y. koide, T. Higuchi, and K. Terabe, Abstr. 22nd Intl. Conf. on Solid State Ionics, 2019, P-TUE-108.[2] J.N. Bradley and P.D. Greene, Trans. Faraday Soc., 63 (1967) 424.[3] J. E. Oxley, Proc. Power Sources Symp., 24, 20 (1970)Fig. 1. Switching characteristics of H-terminated diamond-based all-solid-state EDLTs in the temperature range of 298-340 K. The gate electrodes are (a) Pt/LCO and (b) Au. 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.

Binder-assisted electrostatic spray deposition of LiCoO2 and graphite films on coplanar interdigitated electrodes for flexible/wearable lithium-ion batteries

Flexible battery technologies have lately attracted much attention in the field of wearable electronics. A coplanar interdigitated electrode design encompasses the merits of bending tolerance and increased kinetics owing to shortened diffusion length for applications in these batteries. However, the fabrication of a coplanar patterned electrode remains a challenge because the conventional slurry casting method is unsuitable. In this study, we present a new process to prepare an interdigitated coplanar electrode using binder-assisted electrostatic spray deposition (ESD) without vacuum or high-cost techniques. Using the binder-assisted ESD method, it is possible to deposit powder of any type or size. Moreover, this approach is versatile and universal for application to the design of any coplanar cell configuration and is achieved using a binder-assisted dispersion method based on a commercially available active material. A full-cell flexible battery is fabricated with a coplanar interdigitated electrode using a LiCoO2 cathode and graphite anode. The low cost, simplicity, efficacy, and flexibility of this method are very promising attributes in the design and fabrication of flexible/wearable batteries.