High energy density in ultra-thick and flexible electrodes enabled by designed conductive agent/binder composite

Thick electrodes can increase incorporation of active electrode materials by diminishing the proportion of inactive constituents,improving the overall energy density of batteries.However,thick electrodes fabricated using the conventional slurry casting approach frequently exhibit an exacerbated accumulation of carbon additives and binders on their surfaces,invariably leading to compromised electrochemical properties.In this study,we introduce a designed conductive agent/binder composite synthesized from carbon nanotube and polytetrafluoroethylene.This agent/binder composite facilitates production of dry-process-prepared ultra-thick electrodes endowed with a three-dimensional and uniformly distributed percolative architecture,ensuring superior electronic conductivity and remarkable mechanical resilience.Using this approach,ultra-thick LiCoO_(2)(LCO) electrodes demonstrated superior cycling performance and rate capabilities,registering an impressive loading capacity of up to 101.4 mg/cm^(2),signifying a 242% increase in battery energy density.In another analytical endeavor,time-of-flight secondary ion mass spectroscopy was used to clarify the distribution of cathode electrolyte interphase(CEI) in cycled LCO electrodes.The results provide unprecedented evidence explaining the intricate correlation between CEI generation and carbon distribution,highlighting the intrinsic advantages of the proposed dry-process approach in fine-tu ning the CEI,with excellent cycling performance in batteries equipped with ultra-thick electrodes.

Dry electrode technology for scalable and flexible high-energy sulfur cathodes in all-solid-state lithium-sulfur batteries

All-solid-state lithium-sulfur batteries(ASSLSBs)employing sulfide solid electrolytes are one of the most promising next-generation energy storage systems due to their potential for higher energy density and safety.However,scalable fabrication of sheet-type sulfur cathodes with high sulfur loading and excellent performances remains challenging.In this work,sheet-type freestanding sulfur cathodes with high sulfur loading were fabricated by dry electrode technology.The unique fibrous morphologies of polytetrafluoroethylene(PTFE)binders in dry electrodes not only provides excellent mechanical properties but also uncompromised ionic/electronic conductance.Even employed with thickened dry cathodes with high sulfur loading of 2 mg cm^(-2),ASSLSBs still exhibit outstanding rate performance and cycle stability.Moreover,the all-solid-state lithium-sulfur monolayer pouch cells(9.2 m Ah)were also demonstrated and exhibited excellent safety under a harsh test situation.This work verifies the potential of dry electrode technology in the scalable fabrication of thickened sulfur cathodes and will promote the practical applications of ASSLSBs.

High‑Performance Flexible Microneedle Array as a Low‑Impedance Surface Biopotential Dry Electrode for Wearable Electrophysiological Recording and Polysomnography

Microneedle array(MNA)electrodes are an effective solution to achieve high-quality surface biopotential recording without the coordination of conductive gel and are thus very suitable for long-term wearable applications.Existing schemes are limited by flexibility,biosafety,and manufacturing costs,which create large barriers for wider applications.Here,we present a novel flexible MNA electrode that can simultaneously achieve flexibility of the substrate to fit a curved body surface,robustness of microneedles to penetrate the skin without fracture,and a simplified process to allow mass production.The compatibility with wearable wireless systems and the short preparation time of the electrodes significantly improves the comfort and convenience of electrophysiological recording.The normalized electrode–skin contact impedance reaches 0.98 kΩcm^(2)at 1 kHz and 1.50 kΩcm^(2)at 10 Hz,a record low value compared to previous reports and approximately 1/250 of the standard electrodes.The morphology,biosafety,and electrical/mechanical properties are fully characterized,and wearable recordings with a high signal-to-noise ratio and low motion artifacts are realized.The first reported clinical study of microneedle electrodes for surface electrophysiological monitoring was conducted in tens of healthy and sleep-disordered subjects with 44 nights of recording(over 8 h per night),providing substantial evidence that the electrodes can be leveraged to substitute for clinical standard electrodes.

Wearable multilead ECG sensing systems using on-skin stretchable and breathable dry adhesives

Electrocardiogram(ECG)monitoring is used to diagnose cardiovascular diseases,for which wearable electronics have attracted much attention due to their lightweight,comfort,and long-term use.This study developed a wearablemultilead ECG sensing system with on-skin stretchable and conductive silver(Ag)-coated fiber/silicone(AgCF-S)dry adhesives.Tangential and normal adhesion to pigskin(0.43 and 0.20 N/cm2,respectively)was optimized by the active control of fiber density and mixing ratio,resulting in close contact in the electrode–skin interface.The breathableAgCF-S dry electrodewas nonallergenic after continuous fit for 24 h and can be reused/cleaned(>100 times)without loss of adhesion.The AgCF encapsulated inside silicone elastomers was overlapped to construct a dynamic network under repeated stretching(10%strain)and bending(90°)deformations,enabling small intrinsic impedance(0.3,0.1 Hz)and contact impedance variation(0.7 k)in high-frequency vibration(70 Hz).All hard/soft modules of the multilead ECG system were integrated into lightweight clothing and equipped with wireless transmission for signal visualization.By synchronous acquisition of I–III,aVR,aVL,aVF,and V4 lead data,the multilead ECG sensing system was suitable for various scenarios,such as exercise,rest,and sleep,with extremely high signal-to-noise ratios.

Non-contact ECG Monitoring Based on Capacitive Electrodes

Recent interest in mobile-based heahhcare has driven significant demands on researching non-contact electrodes for electrocardiogram （ECG） measurement. While the conductive gel achieves the requirement in making a good contact between the electrodes and skin, several problems appear. A gel-free, non-contact electrode based on capacitive coupling theory was provided in this paper, which was integrated on the print circuit board （PCB）. The experimental results showed that clear ECG signals could be acquired in the laboratory conditions by coupling the electrodes to the chest of patients through cotton belts.

Self-adhesive and biocompatible dry electrodes with conformal contact to skin for epidermal electrophysiology

Long-term biopotential monitoring requires high-performance biocompatible wearable dry electrodes.But currently,it is challenging to establish a form-preserving fit with the skin,resulting in high interface impedance and motion artifacts.This research aims to present an innovative solution using an all-green organic dry electrode that eliminates the aforementioned challenges.The dry electrode is prepared by introducing biocompatible maltitol into the chosen conductive polymer,poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate).Thanks to the secondary doping and plasticizer effect of maltitol,the dry electrode exhibits good stretchability(62%),strong self-adhesion(0.46 N/cm),high conductivity(102 S/cm),and low Young's modulus(7 MPa).It can always form a conformal contact with the skin even during body movements.Together with good electrical properties,the electrode enables a lower skin contact impedance compared to the current standard Ag/AgCl gel electrode.Consequently,the application of this dry electrode in bioelectrical signal measurement(electromyography,electrocardiography,electroencephalogra-phy)and long-term biopotential monitoring was successfully demonstrated.

Claw-shaped flexible and low-impedance conductive polymer electrodes for EEG recordings: Anemone dry electrode

Electroencephalogram(EEG) signals provide important brain information in healthcare settings. Wet electrodes have several limitations, including their time-consuming preparation and no long-term acquisition, and dry electrodes have become a promising candidate. However, dry electrodes face several challenges related to signal quality, comfort, conductivity and cost.This study aims to develop and evaluate a novel dry electrode for EEG recordings. The electrode material properties are characterized by electrochemical, mechanical force, and skin measurements. The electrode performance is evaluated by comparing the impedance, signal-to-noise ratio(SNR), and EEG signal features of the proposed electrode with those of a wet electrode and two commercial dry electrodes. The dry electrode design is based on the biological structure of the sea anemone and demonstrates an improved scalp fit and reduced signal noise and motion artifacts. The electrode materials include advanced conducting polymers combined with thermoplastic elastomers(TPEs) and carbon nanotubes(CNTs), which exhibit good electrical conductivity, mechanical properties, and safety. A low-cost injection molding fabrication method is proposed. The dry electrodes show a scalp contact impedance of 7 kΩ at 20 Hz, which is lower than that of wet and commercial dry electrodes.Resting-state EEG and event-related potential signals collected by the anemone dry electrode achieved more than 90% similarity with signals acquired by wet electrodes. Thus, a low-cost, comfortable anemone dry electrode that exhibits excellent EEG recording performance is presented. The anemone dry electrode represents an important technological advance in material and structural design for EEG recording sensors.

Effect of needle number on drying rate of kiwi fruit in EHD drying process

Electrohydrodynamic (EHD) drying is a novel method of non-thermal processing. In this drying method, drying can be carried out using either AC or DC high voltages. The thermodynamic considerations regarding the lowering of temperature under EHD drying include rapid rates of evaporation and exothermic interaction of the electric field with a dielectric material. Multi-point and plate electrode systems are efficient in accelerating drying of agricultural materials. The electrode produces corona wind, which resembles a round jet, impinges and removes moisture from the surface. The enhancement of drying rate by corona discharge from needle electrodes has been experimentally evaluated in this study. Effects of three different categories, one needle, nine needles and seventeen needles on drying rate of kiwi fruit were studied, moreover in each category, Experiments were carried out using DC voltage levels of 6, 10.5 and 15 kV and field intensities 4.5 kV/cm. Results showed that the effect of needle number on drying rate was significant and drying rate of kiwi fruit reduced with increasing in needle numbers.

A low-power portable ECG sensor interface with dry electrodes

This paper describes a low-power portable sensor interface dedicated to sensing and processing elec- trocardiogram （ECG） signals. Dry electrodes were employed in this ECG sensor, which eliminates the need of conductive gel and avoids complicated and mandatory skin preparation before electrode attachment. This ECG sensor system consists of two ICs, an analog front-end （AFE） and a successive approximation register analog-to- digital converter （SAR ADC） containing a relaxation oscillator. This proposed design was fabricated in a 0.18 #m 1P6M standard CMOS process. The AFE for extracting the biopotential signals is essential in this ECG sensor. In measurements, the AFE obtains a mid-band gain of 45 dB, referred noise of 2.8μV rms while consuming 1μW from the a bandwidth from 0.6 to 160 Hz, and a total input 1.8 V supply. The noise efficiency factor （NEF） of our design is 3.4. After conditioning, the amplified ECG signal is digitized by a 12-bit SAR ADC with 61.8 dB SNDR and 220 fJ/conversion-step. Finally, a complete ECG sensor interface with three dry copper electrodes is demonstrated in real-word setting, showing successful recordings of a capture ECG waveform.

Advanced electrode processing of lithium ion batteries:A review of powder technology in battery fabrication

Lithium ion batteries have achieved extensive applications in portable electronics and recently in electronic vehicles since its commercialization in 1990s.The vast applications of lithium ion batteries are not only derived from the innovation in electrochemistry based on emerging energy materials and chemical engineering science,but also the technological advances in the powder technologies for electrode processing and cell fabrication.Revealing the effects of powder technology on electrode microstructure evolution during electrode processing is with critical value to realize the superior electrochemical performance.This review presents the progress in understanding the basic principles of the materials processing technologies for electrodes in lithium ion batteries.The impacts of slurry mixing and coating,electrode drying,and calendering on the electrode characteristics and electrochemical performance are comprehensively analyzed.Conclusion and outlook are drawn to shed fresh lights on the further development of efficient lithium ion batteries by advancing powder technologies and related advanced energy materials.