Thin-film Batteries Research Articles

Monolithically-stacked thin-film solid-state batteries

The power capability of Li-ion batteries has become increasingly limiting for the electrification of transport on land and in the air. The specific power of Li-ion batteries is restricted to a few thousand W kg−1 due to the required cathode thickness of a few tens of micrometers. We present a design of monolithically-stacked thin-film cells that has the potential to increase the power ten-fold. We demonstrate an experimental proof-of-concept consisting of two monolithically stacked thin-film cells. Each cell consists of a silicon anode, a solid-oxide electrolyte, and a lithium cobalt oxide cathode. The battery can be cycled for more than 300 cycles between 6 and 8 V. Using a thermo-electric model, we predict that stacked thin-film batteries can achieve specific energies >250 Wh kg−1 at C-rates above 60, resulting in a specific power of tens of kW kg−1 needed for high-end applications such as drones, robots, and electric vertical take-off and landing aircrafts.

Highly conductive Ag-SiNx composite thin film anode engineering for transparent battery

Silicon nitride-based electrodes (SiNx), have been proposed as promising candidates for high-capacity transparent anode electrodes in earlier studies. Unfortunately, they have low electrical conductivity, resulting in some disadvantages such as power density for application in thin film batteries. To improve electrical conductivity, bulk batteries use conductive carbon additives, which also impair transmittance. Thus, we conducted this research to enhance the electrochemical properties by improving the conductivity without compromising the transmittance by uniformly dispersed Ag nanoparticles in SiNx thin film. We obtained an Ag-SiNx composite thin-film anode via continuous composition spread sputtering and investigated the effect of the Ag concentration. The capacity of the thin-film battery raised to 242.8 μAh/cm2·μm with Ag0.236SiO0.7N anode compared to the SiO0.7N anode which had a capacity of 37.2 μAh/cm2·μm. In addition, while SiO0.7N was operated only up to 2 C, Ag0.236SiO0.7N has driven up to 5 C and 10 C, which are high C rates, was also possible. AgxSiO0.7N thin film with less than 0.236 mol content demonstrates an optical transmittance of over 60% in the visible area. These results indicate that improving the electrical conductivity by the addition of an Ag during the silicon nitride deposition can increase its electrochemical performance while maintaining its applicability to transparent batteries.

An Implantable Bio-Signal Sensor SoC with Low-Standby-Power 8K-Bit SRAM for Continuous Long-Term Monitoring

Individualized treatment of chronic diseases opens up great opportunities for implantable biosensor systems capable of tracking vital signals over long periods of time. To this end, low-power techniques in standby mode and the efficient utilization of storage space will be important issues for the implementation of such rechargeable implants with a built-in memory. This paper presents key circuit techniques, including a leakage-current-based clock generator that eliminates the need for an internal reference clock source, a low-standby-power 8Kbit SRAM with negative wordline and dynamic supply voltage scaling, and an adaptive sensing scheme to improve storage space utilization. When implemented with commercial 180 nm CMOS technology for the circuit simulation, approximately 70% (100 nW) of power dissipation was reduced from internal clock source, about 70% of power consumed by 8Kbit SRAM was saved, and the storage space utilization was improved by about 42.8%. In the end, the proposed implantable biosensor SoC consumes about 82.5 nW of standby power, saving about 42% from the previous approach and can last for 2.5 days using a 5 uAh thin-film battery (CYMBET® 1.7 × 2.2 mm2).

Combining functionalized CNT film with CuS microflowers through hyperbranched polymers for a flexible and appliable rechargeable Mg battery

The flexibility and high tolerance for mechanical deformation of batteries under operation is a critical aspect of flexible energy storage devices. In this paper, a large-area CNT film (CF) is prepared via chemical vapor deposition (CVD) method and then functionalized with hyperbranched polymers (HP) using the thiol-ene click reaction. CuS microflowers are in-situ grown on the flexible CNTs, where HP significantly enhances interfacial compatibility and greatly enhances the combination of CuS nanosheets with CNTs substrate. The modification strategy effectively promotes Mg2+ conversion reaction of CuS and greatly enhances the stability of the flexible electrode. The as-prepared flexible CuS/CF-HP cathode delivers a high magnesium storage capacity of 178 mAh g−1 at 50 mA g−1 and a good rate performance of 94 mAh g−1 at 2 A g−1, with a high Mg2+ diffusion coefficient of about ∼10−12 cm2 s−1 and a capacity retention rate of 79.2% after 200 cycles at 200 mA g−1. Furthermore, a practical flexible thin-film rechargeable Mg battery device based on the CuS/CF-HP cathode and Mg powder/CF anode was fabricated in a sealed polydimethylsiloxane package. The flexible full battery provides an outstanding power output as well as remarkable mechanical durability, demonstrating its potential applications for flexible energy storage devices.

Dynamic Electrode–Electrolyte Intermixing in Solid-State Sodium Nano-Batteries

Nanostructured solid-state batteries (SSBs) are poised to meet the demands of next-generation energy storage technologies by realizing performance competitive to their liquid-based counterparts while simultaneously offering improved safety and expanded form factors. Atomic layer deposition (ALD) is among the tools essential to fabricate nanostructured devices with challenging aspect ratios. Here, we report the fabrication and electrochemical testing of the first nanoscale sodium all-solid-state battery (SSB) using ALD to deposit both the V2O5 cathode and NaPON solid electrolyte followed by evaporation of a thin-film Na metal anode. NaPON exhibits remarkable stability against evaporated Na metal, showing no electrolyte breakdown or significant interphase formation in the voltage range of 0.05-6.0 V vs Na/Na+. Electrochemical analysis of the SSB suggests intermixing of the NaPON/V2O5 layers during fabrication, which we investigate in three ways: in situ spectroscopic ellipsometry, time-resolved X-ray photoelectron spectroscopy (XPS) depth profiling, and cross-sectional cryo-scanning transmission electron microscopy (cryo-STEM) coupled with electron energy loss spectroscopy (EELS). We characterize the interfacial reaction during the ALD NaPON deposition on V2O5 to be twofold: (1) reduction of V2O5 to VO2 and (2) Na+ insertion into VO2 to form NaxVO2. Despite the intermixing of NaPON-V2O5, we demonstrate that NaPON-coated V2O5 electrodes display enhanced electrochemical cycling stability in liquid-electrolyte coin cells through the formation of a stable electrolyte interphase. In all-SSBs, the Na metal evaporation process is found to intensify the intermixing reaction, resulting in the irreversible formation of mixed interphases between discrete battery layers. Despite this graded composition, the SSB can operate for over 100 charge-discharge cycles at room temperature and represents the first demonstration of a functional thin-film solid-state sodium-ion battery.

Effects of Li+ conduction on the capacity utilization of cathodes in all-solid-state lithium batteries.

Li+ conduction in all-solid-state lithium batteries is limited compared with that in lithium-ion batteries based on liquid electrolytes because of the lack of an infiltrative network for Li+ transportation. Especially for the cathode, the practically available capacity is constrained due to the limited Li+ diffusivity. In this study, all-solid-state thin-film lithium batteries based on LiCoO2 thin films with varying thicknesses were fabricated and tested. To guide the cathode material development and cell design of all-solid-state lithium batteries, a one-dimensional model was utilized to explore the characteristic size for a cathode with varying Li+ diffusivity that would not constrain the available capacity. The results indicated that the available capacity of cathode materials was only 65.6% of the expected value when the area capacity was as high as 1.2 mAh/cm2. The uneven Li distribution in cathode thin films owing to the restricted Li+ diffusivity was revealed. The characteristic size for a cathode with varying Li+ diffusivity that would not constrain the available capacity was explored to guide the cathode material development and cell design of all-solid-state lithium batteries.

High-Performance Zn-Ion Microbatteries by Subtractive Manufacturing

Microbatteries are indispensable to power emerging miniaturized electronics for medical, environmental, or stealth applications. However, they are usually fabricated by additive printing processes, limiting their sizes and energy densities. Here, we develop a subtractive manufacturing process by slicing assembled thin-film zinc-ion batteries into microcells in batches using optimized preintercalated MnO2 (K0.27MnO2·0.54H2O, KMO) as cathodes. The composite cathode consisting of KMO and reduced graphene oxide (rGO) delivers a high specific capacity of 323.4 mAh g–1 at 0.1 A g–1 with no capacity loss after 750 cycles at 1 A g–1. Such a high performance renders Zn//KMO/rGO solid-state microbatteries with areal energy densities of 0.244 mWh cm–2, which are comparable to those of the state of the art. This microbattery, with an area of 4 × 4 mm2 and a thickness of 0.56 mm, can be modularly arranged on a chip for a stretchable energy-supply circuit, which can be closely attached to human skin.

Materials Towards the Development of Li Rechargeable Thin Film Battery

The present work gives an overview of materials towards the development of Li rechargeable thin film batteries. Conventional Li rechargeable battery faces issues related with large volume, safety issues due to the presence of liquid electrolyte. These issues are proposed to resolve by developing these batteries in thin film form. The main drawback of these batteries is finding an appropriate inorganic material to be used as electrolytes. Other issue is related with design of appropriate cathode material which should be cost effective and is able to provide better electrochemical performance compared to competitive counterparts. In this review, a brief description of lithium lanthanum zirconate as a solid-state electrolyte and Co free Ni rich layered oxide has been provided to overcome these issues. Strategies for optimizing these materials for designing a stable, safe and cost-effective thin film batteries are also elaborated.

Ordered LiFe5O8 thin films prepared by pulsed laser deposition as an anode material for all-solid thin film batteries

The search for obtaining a Co free low-cost and high-capacity anode thin film material for high energy density all-solid thin film batteries has been driving the increasing innovation and research in Li-ion battery (LIB) technology. In the present case, LiFe5O8 (LFO) thin films are prepared by pulsed laser deposition (PLD) technique and their electrochemical properties, Li ion dynamics, conducting processes at various frequencies and current rates are explored. LFO thin films are seen to crystallize in ordered α -phase with an inverse spinel structure. Chemical state of all the elements is analysed using X-ray photoelectron spectroscopy method. Cyclic voltammeter (CV) study carried out between 0–3 V shows the reduction peak at 0.76 V initially and in the later cycles at 0.86 V with a small shift depicting the exact conversion type behaviour of the LFO thin film. LFO thin film exhibits specific discharge capacity of 25 μAh/cm2 at 10 μA/cm2 current density during the first cycle. Rate capability measurements are carried out at various current densities of 10, 20, 30, 40, 50 and 10 μA/cm2. Li-ion diffusion coefficient during the de-lithiation and lithiation process is seen to be 3.78 × 10−14 cm2/s and 1.41 × 10−13 cm2/s, respectively. CV studies at various scan rates indicates that the mechanism of Li+ storage is dominated by a diffusion-controlled process at low scan rates and with increasing scan rate it becomes a surface-controlled process. Electrochemical impedance studies at various frequencies shows the decrease in charge transfer resistance with increasing cycles. Combined structural, chemical, electrochemical and impedance studies of LFO thin films indicates that these films can be employed for fabricating Co and Ni free all-solid thin film Li-ion batteries for energy storage applications.

All-Solid-State Thin-Film Lithium-Sulfur Batteries

HighlightsThe all-solid-state thin-film Li-S battery has been successfully developed by stacking VGs-Li2S cathode, lithium-phosphorous-oxynitride (LiPON) solid electrolyte, and Li anode.The obtained VGs-Li2S thin-film cathode exhibits excellent long-term cycling stability (more than 3,000 cycles), and an exceptional high temperature tolerance (up to 60 °C).The superb electrochemical performance can be attributed to the favorable compatibility and outstanding interfacial stability between VGs-Li2S thin film and LiPON.

A high-energy/power and ultra-stable aqueous ammonium ion microbattery based on amorphous/crystalline dual-phase layered metal oxides

The prosperity of microelectronic systems stimulates fast development of high-performance power sources with micro/nano sizes. Considering the defects of conventional lithium-ion microbatteries, i.e. high cost, severe safety concerns as well as the unsatisfactory power delivery due to the sluggish ion transport of the organic electrolytes, novel energy storage microdevices are worth looking forward to. Here, we assemble an aqueous ammonium-ion microbattery using 2D (NH4)xV2O5 with amorphous/crystalline dual-phase nanostructure deposits on 3D nanoporous Au as anode while nanoporous Au/δ-MnO2 composite as cathode. As a result of the superb electronic/ionic conductivities as well as the large voltage window, the resultant NP Au/ac-(NH4)xV2O5//NP Au/δ-MnO2 aqueous ammonium-ion microbattery exhibits ultrahigh energy density of 0.126 Wh cm−3 with electrical powers ∼280-fold higher than commercial lithium thin-film batteries, in addition to excellent rate capability (∼84.2% capacity retention at 5–50 mV s−1 scan rates) and cycling stability (retains ∼93.3% of the initial value after 10,000 cycles at 500 mV s−1). The superb performance endows it to be promising candidate as monolithic micropower source for micro/nano portable/wearable electronics with high energy storage and power delivery demands.

Search for a space charge layer in thin film battery materials with low-energy muons

In an all solid state Li-ion battery, it is crucial to reduce ionic resistivity at the interface between the electrode and the electrolyte in order to enhance Li+ mobility across the interface. Recent first principles calculations predict the presence of a space-charge layer (SCL) at the interface due to the difference in the Li+ chemical potential at the interface between two different materials, as in the metal-semiconductor junction in electronic devices. However, the presence of SCL has never been experimentally observed. Our first attempt in a fresh multilayer sample, Cu(10 nm)/Li3PO4(50 nm)/LiCoO2(100 nm) on a sapphire substrate, with low-energy µ +SR (LE µ +SR) revealed a gradual change in the nuclear magnetic field distribution width as a function of implantation depth even across the interface between Li3PO4 and LiCoO2. This implies that the change in the field distribution width at SCL of the sample is too small to be detected by LE µ +SR.

Protons Inside the LiCoO2 Electrode Largely Increase Electrolyte–Electrode Interface Resistance in All-Solid-State Li Batteries

Formation of an electrolyte–electrode interface that allows smooth Li-ion transport is essential for the further development of all-solid-state Li batteries. Water vapor is recognized as one critical origin of increased resistance at the electrolyte–electrode interface. However, the detailed mechanism of the degradation remains unclarified. This study uses a thin-film battery with a LiCoO2 electrode to investigate how protons at the interface contribute to the degradation. Protons were introduced to the LiCoO2 by exposing the surface to water vapor. Electrochemical, compositional, and structural investigations reveal that the protons induce the mixing of Li and Co during the first charging process. The mixing induces the formation of low-temperature-phase LiCoO2; this layer acts as an interphase layer that degrades battery performance. Understanding these interfacial phenomena contributes to increasing the power density of all-solid-state Li batteries.

Oxygen-Related Defect Engineering of Amorphous Vanadium Pentoxide Cathode for Achieving High-Performance Thin-Film Aqueous Zinc-Ion Batteries

Thin-film aqueous zinc-ion batteries are expected to serve as next-generation energy storage devices that are both low-cost and safe. However, to realize practical energy storage devices based on zinc-ion batteries, it is necessary to develop reliable, high-capacity cathode materials. In this study, we prepared a V2O5-based thin-film electrode and investigated the effect of varying the Ar pressure during radio frequency magnetron sputtering of V2O5, a representative cathode material in thin-film zinc-ion batteries, to control the number of oxygen vacancies in the oxide lattice. The optimized V2O5 thin-film electrode exhibited enhanced electrochemical activities, low degree of polarization, improved ion diffusion, and increased electrical conductivities. Specifically, an oxygen-deficient V2O5–x thin-film prepared by sputtering under high pressure exhibited a high rate capability (57.2 mAh g–1 at 20 C) and superior electrochemical performance (105.2 mAh g–1 for up to 1000 cycles at a current density of 5 C). The mechanism for the performance enhancement was revealed by density functional theory calculations, which showed that the oxygen-deficient V2O5–x had a lower Zn2+-ion diffusion energy barrier than that of pristine V2O5. This defect engineering strategy for tuning the oxidation state should aid in designing high-performance cathodes for advanced thin-film aqueous battery chemistry.

Modeling the Resistance of Thin-Film Current Collectors in Thin-Film Batteries

Thin-film lithium-ion batteries (LIBs) have attracted much attention as one of the state-of-the-art energy storage technologies. However, most research regarded the current collector as infinitely conductive or with no separate simulation for this part. Herein, a model is proposed to simulate thin-film current collectors’ potential distribution and resistance. The effects of changing the aspect ratio and the thickness on the thin-film current collector are investigated. The experimental results obtained are in excellent agreement with the model. At the same time, this method is quite generic and can also be used for other types of batteries.

Cover Feature: LiNi0.5Mn1.5O4 Thin Films Grown by Magnetron Sputtering under Inert Gas Flow Mixtures as High‐Voltage Cathode Materials for Lithium‐Ion Batteries (ChemElectroChem 3/2023)

The Cover Feature illustrates the magnetron sputtering process with variable ratio of Ar/N as process gas that leads to the formation of thin-films of N-containing LNMO high voltage cathodes. These results in improved electrochemical performance with respect to bare LNMO could be used to fabricate thin-film high voltage Li-ion batteries. More information can be found in the Research H. Darjazi et al.

Impedance of a thin-film lithium-ion battery Si@O@Al|LiPON|LiCoO-=SUB=-2-=/SUB=- at temperatures from -20-=SUP=-o-=/SUP=-C to +50-=SUP=-o-=/SUP=-C

The results on measuring the impedance of a solid-state thin-film lithium-ion battery of the Si@O@Al-LiPON-LiCoO2 electrochemical system in the temperature range from -20oC to +50oC are presented. A structural model is proposed and the parameters of its elements, providing the best fit for the experimental Nyquist diagrams, are calculated. It is shown that the main contribution to the internal resistance is made by the LiPON-LiCoO2 interface. Based on the temperature dependence of the LiPON solid electrolyte conductivity the activation energy of lithium is determined, which is in good agreement with the literature data. Keywords: Nanocomposite, lithium-ion battery, impedance spectroscopy, structural model, ionic conductivity.

Особенности протекания твердофазных реакций в трехслойной пленочной системе Sn/Fe/Cu

Study of the mechanisms of the solid-state reactions in Sn/Fe/Cu thin films is interesting both from a fundamental point of view and from a view of the importance of emerging intermetallics in the technology of solder joints and thin-film lithium-ion batteries. By the integrated approach, including both X-ray phase analysis and local elemental analysis of the cross-sections of the films, the phase composition and the mutual arrangement of phases were studied, at various stages of the solid-state reaction occurring at different temperatures. The observed sequence of the appearing phases differs significantly from the expected one if the mass transfer took place by a volume diffusion through the forming layers.

Electrochemical Characteristics of LiNbO<sub>3</sub> Anode Film and Its Applications in All-Solid-State Thin-Film Lithium-Ion Battery

Electrochemical Characteristics of LiNbO<sub>3</sub> Anode Film and Its Applications in All-Solid-State Thin-Film Lithium-Ion Battery

Investigation of LiCoO2 thin film battery properties with changing Ar/O2 gas atmosphere

Thin film batteries are considered the most promising next-generation batteries due to their superior safety and highly developed energy density. The deposition of LiCoO2 thin films with 200 nm thickness was carried out by radio frequency magnetron sputtering. The LiCoO2 thin films were deposited in Ar/O2 gas mixture and coated samples which were deposited in 3% and 10% oxygen amounts, labeled as LCO-3 and LCO-10, respectively. Deposited LCO-3 and LCO-10 thin films possess phase purity and high crystallinity and have a uniform nanostructure with an average grain size of 30-60 nm with homogeneous dispersion. The cyclic voltammetry curves of LCO-3 and LCO-10 electrodes upon electrochemical cycling revealed phase transformations of both materials. The ionic conductivity of the LCO-10 thin films have been exhibited more convenient results than LCO-3 samples. The electrode manifests superior specific capacity of 48 ?Ah/cm2 in the initial cycle. This study provides an information on how LiCoO2 crystal structure and electrochemical properties are affected by changing deposition parameters such at the Ar/O2 gas mixture.