Boosting high-rate capability of Li4Ti5O12 anode via carbon coating fabricated by magnetron sputtering

High-performances of Li4Ti5O12 anodes for lithium-ion batteries via modifying the Cu current collector through magnetron sputtering amorphous carbon

The interface between the current collector and active material is the primary interface of charge transfer. Herein, we designed an effective strategy to optimize the interface architecture by depositing molybdenum disulfide on the copper foil surface (Cu-MoS2) via magnetron sputtering. The Cu-MoS2 is directly used as a current collector and supports the Li4Ti5O12 anode (Cu-MoS2-LTO). Typically, after being cycled at 1 A g-1 for 300 cycles, the capacities of the Cu-LTO cell and Cu-MoS2 cell are about 114.94 and 128.35 mA h g-1, respectively, whereas the capacity of the Cu-MoS2-LTO cell is as high as 373.9 mA h g-1 with a capacity retention rate of 89.1%. The MoS2 not only optimizes the interfacial architecture but also provides an additional capacity contribution to the Cu-MoS2-LTO cell. Based on scanning electron microscopy and X-ray photoelectron spectroscopy test analysis, we propose a dual interface model. It is revealed that the molybdenum disulfide film can significantly improve the charge-transfer efficiency and uniformity of the interface, reduce internal resistance of the batteries, prevent oxidation of the copper foil, and thereby improve the chemical stability of the current collector. In addition, magnetron sputtering technology has large-scale productivity and greatly enhances the industrial application of this strategy.

To achieve a good combination of high capacity, cyclability and rate capability in an electrode is still a great challenge for lithium-ion batteries, especially those used for electric vehicles. The present work has developed a simple and effective strategy to solve this problem in the layer structured LiV3O8 positive electrode. This has the highest theoretical capacity of the currently available positive electrodes but it has not yet been achieved in practice along with high rate capability. In our approach, an amorphous wrapped [100] orientated nanorod structure has been fabricated in a LiV3O8 thin film by adjusting the oxygen partial pressure in the deposition process using radio frequency (RF) magnetron sputtering. With this structure, a record combination of high capacity and superior high-rate capability, namely 388 mA h g−1 at C/5 and 102 mA h g−1 at 40 C, has been achieved along with stable cycle life. The result revealed that the orientated nanorods provide additional ionic transport channels and their amorphous wrapping layer can withstand the anisotropy of the surface during the intercalation of Li ions.

Editorial: Energy Storage Materials: A Special Issue of <i>Energy Technology</i>

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

Amorphous Si film anode coupled with LiCoO 2 cathode in Li-ion cell

Fabrication and characterization of Li–Mn–Ni–O sputtered thin film high voltage cathodes for Li-ion batteries

Introduction Oxide-based all-solid-state rechargeable batteries (Ox-SSBs) have been expected as next generation energy storage devices with both high energy density and safety. Especially, thin-film type Ox-SSBs will be the most successful battery and are commercially available. In case of those thin-film Ox-SSBs, crystalline cathode electrodes are generally used, which have been prepared by RF magnetron sputtering, PLD, et al with heating process. On the other hand, aerosol deposition (AD) is a novel technique for preparing dense ceramics films at room temperature by jetting dry powders to the substrates. In addition, the deposition rate of the AD is much higher (5-50 μm min-1) than those in conventional deposition techniques such as RF magnetron sputtering (0.01-0.05 μm min-1)[1]. Hence, we focus on the AD to deposit thin films of composite cathode electrodes for thin-film type SSBs. In this work, we prepared composite electrode films composed of LiNi1/3Co1/3Mn1/3O2 (NMC) and Li1.4Ti2Si0.4P2.6O12-AlPO4(LATP) by the AD. These composite films were combined with LiPON and Si anode film, and electrochemical properties of the thin-film SSB of Si/LiPON/NMC-LATP were investigated. Experimental Composite powders of NMC (Nihon Kagaku Inc.) and LATP (Ohara Inc.) were prepared using a dry-powder mixer (NOB-MINI, Hosokawa Micron Co.). The mixing ratio of NMC to LATP was 100 : 5 in weight. Obtained composite powders were deposited onto a SUS substrate or a Si wafer by AD to fabricate a composite electrode. The resultant thin film was coated with a lithium phosphorus oxynitride (LiPON) glass electrolyte thin film by radio frequency (RF) magnetron sputtering. Subsequently, the Si anode thin film was deposited on the top of a LiPON film by RF magnetron sputtering. Cross-sections of a fabricated SSB (Si/LiPON/NMC-LATP) were observed by FE-SEM. Impedance measurements were performed in frequency ranges within 100 mHz to 200 kHz. Charge-discharge measurements were carried out for fabricated SSBs using 50 μA cm-2 (0.5C) for charging and 50-2000 μA cm-2for discharging. All electrochemical measurements were carried out at 100 °C in Ar-filled-glove boxes. Results and Discussion Figure 1 shows the cross-sectional FE-SEM image of a SSB (Si/LiPON/NMC-LATP) on a Si wafer substrate. A dense NMC-LATP composite film was successfully deposited on SUS by “one-scan” AD (ca. 6 second) as shown in Fig. 1. The thicknesses of NMC-LATP, LiPON, and Si anode layers were approximately 2.6 μm, 4.0 μm, and 300 nm, respectively. Figure 2 shows charge-discharge curves for a SSB on a SUS substrate. The discharge capacity for the first cycle at 50 μA cm-2 was 147 mAh g-1 where the cutt-off voltage was 3.0 V. This value corresponds to 98% of the capacity of a NMC-LATP composite film measured in liquid electrolyte cells. Moreover, 40 mAh g-1 was still obtained as the discharge capacity at 2.0 mA cm-2 (20C). Highly Li+-conductive-glass-ceramic LATP is supposed to promote the Li+ conduction and inhibit crack propagations associated with volume changes of NMC particles. These effects are likely to be the reason that this SSB provides higher rate capability than that in previous work[2]. We will further examine the effect of film thickness on the rate capabilities and stabilities. Reference 1. J. Akedo, S. Nakano, J. Park, S. Baba, and K. Ashida, Synthesiology 1, 130 (2008). 2. S. Iwasaki, T. Hamanaka, T. Yamakawa, W. C. West, K. Yamamoto, M. Motoyama, and Y. Iriyama, J. Power Sources, 272, 1086 (2014). Figure 1

The coating of LiFePO4 (LFP) particles with conductive nanodots is demonstrated for the first time via magnetron sputtering to improve the LFP conductivity and thus the cathode performance in lithium‐ion batteries. It is confirmed by diverse characterization that the conductive nanodots‐coated LFP have the same crystal structure as the pristine LFP. The conductive nanodots are found to be less than 10 nm in diameter and well distributed on the LFP surface. When used as a cathode material for lithium‐ion batteries, the Ag, Co, and indium tin oxide nanodots‐coated LFPs show a high discharge capacity of 161.3, 154.7, and 147.9 mAh g−1, respectively, whereas the pristine LFP has a lower specific capacity of 146.6 mAh g−1. The coated LFP also has a higher rate capability and a lower charge transfer resistance than the pristine LFP.

Recently, applications for lithium-ion batteries (LIBs) have expanded to include electric vehicles and electric energy storage systems, extending beyond power sources for portable electronic devices. The power sources of these flexible electronic devices require the creation of thin, light, and flexible power supply devices such as flexile electrolytes/insulators, electrode materials, current collectors, and batteries that play an important role in packaging. Demand will require the progress of modern electrode materials with high capacity, rate capability, cycle stability, electrical conductivity, and mechanical flexibility for the time to come. The integration of high electrical conductivity and flexible buckypaper (oxidized Multi-walled carbon nanotubes (MWCNTs) film) and high theoretical capacity silicon materials are effective for obtaining superior high-energy-density and flexible electrode materials. Therefore, this study focuses on improving the high-capacity, capability-cycling stability of the thin-film Si buckypaper free-standing electrodes for lightweight and flexible energy-supply devices. First, buckypaper (oxidized MWCNTs) was prepared by assembling a free stand-alone electrode, and electrical conductivity tests confirmed that the buckypaper has sufficient electrical conductivity (10−4(S m−1) in LIBs) to operate simultaneously with a current collector. Subsequently, silicon was deposited on the buckypaper via magnetron sputtering. Next, the thin-film Si buckypaper freestanding electrodes were heat-treated at 600 °C in a vacuum, which improved their electrochemical performance significantly. Electrochemical results demonstrated that the electrode capacity can be increased by 27/26 and 95/93 μAh in unheated and heated buckypaper current collectors, respectively. The measured discharge/charge capacities of the USi_HBP electrode were 108/106 μAh after 100 cycles, corresponding to a Coulombic efficiency of 98.1%, whereas the HSi_HBP electrode indicated a discharge/charge capacity of 193/192 μAh at the 100th cycle, corresponding to a capacity retention of 99.5%. In particular, the HSi_HBP electrode can decrease the capacity by less than 1.5% compared with the value of the first cycle after 100 cycles, demonstrating excellent electrochemical stability.

Spinel Li4Ti5O12 anode was prepared by traditional doctor blade method. The as-prepared electrode was coated with a thin Al2O3 layer by a facile radio frequency (RF) magnetron sputtering afterwards. The structure and morphology were characterized by XRD and SEM. The electrochemical performance was collected by galvanostatic discharge-charge tests. The measuring potential range was between 0.01 V and 3.0 V. The reversible capacity was as high as 194 mAh/g when discharge/charged at a current density of 35 mA/g. The coating layer did not hinder the performance under high current density, showing the discharge capacity of 134 mAh/g at 175 mA/g. The capacity retention after 100 cycles at 88 mA/g is 91%, much higher than that of the pristine Li4Ti5O12 electrode. The greatly improved cycle stability was attributed to the reduced polarization and the enhanced integrity of the electrode structure.

The demand for high-performance energy storage devices to power Internet of Things applications has driven intensive research on micro-supercapacitors (MSCs). In this study, RuN films made by magnetron sputtering as an efficient electrode material for MSCs are investigated. The sputtering parameters are carefully studied in order to maximize film porosity while maintaining high electrical conductivity, enabling a fast charging process. Using a combination of advanced techniques, the relationships among the morphology, structure, and electrochemical properties of the RuN films are investigated. The films are shown to have a complex structure containing a mixture of crystallized Ru and RuN phases with an amorphous oxide layer. The combination of high electrical conductivity and pseudocapacitive charge storage properties enabled a 16µm-thick RuN film to achieve a capacitance value of 0.8Fcm-2 in 1m KOH with ultra-high rate capability.

In the last years the number of high performance mobile devices, such as smart phones or tablet PCs, increases widely and accordingly data traffic augments rapidly. Devices for these equipment require high-rate processing capabilities, high-density packaging possibilities and low power consumptions for data-center and servers. Thus the demand for packed semiconductor chips with high density of components is growing. In order to accomplish high-density packaging, miniaturization technology of wiring in heterogeneous Fan-out Wafer Level Packaging (FO-WLP) is needful to multi chip module system fabrication using by the re-distribution layer (RDL) wiring technologies. To obtain the fine vias and line/space in a polyimide film, the PVD sputtering and electro-Cu deposition processes are widely used but there are three major restricting difficulties. The first is that it is difficult to make fine vias and line / space in the FO-WLP process. The second is that PVD sputtering process for high adhesion between Cu and polyimide films is also will be issue by status of surface and surface residue. The third is that surface damage of polyimide by the plasma irradiation (Ions, UV), moisture absorption.In this paper, we report the role of the dry etching to fabricate the RDL. The dry etching has already applied in various RDL fabrication process, such as dry descum process, the surface modification process and so on. Dry descum process is named that the process is the removal of photoresist (PR) residues after photo-lithography. The surface modification process has two major functions. First is the improvement of the interface adhesion of the films. To improve of the adhesion, it is necessary that the change of surface morphology. As one way, the changing of the surface configuration is suggested. To obtain the surface with large roughness, the etching process is recommended that the bombardment characteristics is more effective. As the result, the contact area is increased by the etching, so the adhesion would be improved. Alternatively, the application of the chemical response between films is suggested. To generate the chemical function groups, the etching process is recommended that the chemical response is more effective. These surface morphology is adjusted by dry etching condition. In this study, we focus the control of hydrophilic property using dry etching process. In RDL process, it is important to conduct a pre-treatment of electro-Cu deposition processes. When the polymer surface has hydrophobic characteristic, Cu plating solution would be rejected from the surface of polymer. Then, the plating solution cannot enter the bottom position of channels in polymer films, and the voids may be generated. In the future, these channels would be become reduced in size, therefore the control of hydrophilic property would be focused.

Surface-controlled sodium-ion storage mechanism of Li4Ti5O12 anode

The development of fast-charging lithium-ion batteries (LIBs) is crucial for achieving significant market adoption of electric vehicles (EVs). The successful achievement of fast-charging LIBs depends on efficient charge transfer and the diffusivity of lithium ions. The photo-assisted battery system exhibits promising fast-charging properties. Previous research has shown that direct exposure to white light can induce a more oxidized center in a spinel LiMn2O4 (LMO) cathode, accelerating its charging rate.[ 1] Recently, our group found that illumination with red light on an operating LMO cathode induces an Mn d-d electron excitation, simultaneously shrinks the Mn-Mn lattice, and facilitates faster delithiation of the LMO cathode.[ 2] Consequently, the charging time of the battery decreases. This encourages us to consider whether the photon energy from a specific wavelength of light can also enhance the lithiation process on the anode side. Spinel Li4Ti5O12 (LTO) is a promising material for faster-charging anodes due to its small volume charge and high-rate capability in lithium intercalation. However, the system displays slow lithium diffusivity due to poor bulk ionic conductivity. To examine the photon effect of light on these anodes, we demonstrate the photo-accelerated fast-charging (lithiation process) mechanism with an LTO spinel anode.The thin film LTO's energy band gap (Eg), approximately 3.4 eV, was determined through intense UV-visible (UV-Vis) absorption spectrum analysis, assessed in a transmission mode employing Tauc’s Law. This indicates that an LED light with photon energy around 3.4 eV might trigger rapid charging by exciting electron transfer to the T-t2g band. To explore the impact of light on the fast-charging behavior of the LTO electrode, current was measured while applying a constant voltage of 1.2 V. During the 20-minute chronoamperometry experiment, utilizing the 3.4 eV UV LED to illuminate the cell resulted in a progressive increase in current. This current increase peaked at approximately 200s, leading to a maximum average capacity increase of 13 mA h g-1. This suggests that UV illumination accelerates the lithiation process compared to the dark state, particularly favoring the early lithiation stage. Subsequently, a red LED emitting 2 eV photon energy was used to illuminate the same cell, resulting in no discernible change in current levels compared to the dark state. Electrochemical impedance spectroscopy (EIS) further revealed a significant reduction in charge transfer resistance of the window cell when illuminated with UV light compared to both the dark state and red illumination. This alteration in electrode reaction kinetics at the interface suggests a distinct influence of different light wavelengths on the charging process.In addition to assessing charge transfer at the electrode interface, galvanostatic intermittent titration technique (GITT) analysis was conducted at a 2 C rate to further elucidate diffusion within the LTO electrode. The GITT curves reveal that the diffusion of Li+ ions was approximately 1.3 times faster when the cell was illuminated by UV light compared to dark conditions. Consequently, we deduce that photo-accelerated fast charging can also occur during the lithiation process (reduction reaction) of anode materials, driven by optical forces.To delve into the underlying mechanisms, we conducted first-principles density functional theory (DFT) calculations. The outcomes revealed that the generation of additional electrons in LTO results in a reduction in the bandgap and shifts the Fermi level above the conduction band minimum, effectively transforming LTO into an active conductor of electricity. These calculations indicate that UV light illumination has the capability to surmount the bandgap of LTO, generating electron-hole pairs and thereby facilitating charge transfer and lithium-ion diffusion.In conclusion, our study showcased that UV light illumination on the LTO anode can lead to a faster charging speed of approximately 17% compared to dark conditions. We posit that the observed phenomenon of photo-accelerated fast charging in LTO is linked to the formation of electron-hole pairs in intrinsically wide-bandgap insulators or semiconducting materials. This discovery holds considerable implications for the advancement of fast charging technologies for lithium-ion batteries, potentially mitigating range anxiety concerns and facilitating the widespread adoption of electric vehicles.Acknowledgments: This work was supported by funding from Royal Dutch Shell plc. Argonne National Laboratory operates under contract no. DE-AC02-06CH11357 with the U.S. Department of Energy Office of Science. We gratefully acknowledge use of the Bebop or Swing or Blues cluster in the Laboratory Computing Resource Center at Argonne National Laboratory and supported by the U.S. Department of Energy Office of Science.Reference[1] A. Lee et al., Nat. Commun., 10, 4946 (2019).[2] J. Lipton et al., Cell Reports Physical Science, 3, 101051 (2022).