Charging Capability Research Articles

Prelithiated SiO x Anode Materials for Fast Chargeable Lithium-Ion Batteries

To meet the increased demands for electric vehicles(EV), Lithium-ion batteries(LIBs) requires fast charging capability. Conventional LIBs using graphite anodes (with a theoretical specific capacity of 372mAh g-1) have limitations with lithium plating and slow kinetics during fast charging process. To overcome these limitations, many anode materials have been explored in the attempt to replace graphite. Among silicon based anode materials, SiO x is one of suitable materials for fast charging due to its high reaction voltage and high energy density. However, its low initial Coulombic efficiency(ICE) and poor cycle life remain as critical challenges. Herein, we propose prelithiated SiO x materials prepared by dehydrogenation-driven prelithiation of SiO x using LiH to improve the low ICE and poor cycle life. The prelithiated SiO x shows about 85.5 % of ICE and improved long-term cycle performance for over 300 cycles. Also, the prelithiated SiO x anode shows higher charged capacity at high current density. More detailed microstructure and electrochemical properties of the prelithiated SiO x materials will be discussed in this presentation.

Fast-Charging Electrode Architecture Optimization through R2R Screen Printing

Creating vertical channels is a viable strategy for reducing the tortuosity and improving the charge transfer kinetics of electrodes, hence enhancing the fast-charge capacity of lithium-ion batteries (LIBs) to actualize fast-charging electrical products. Despite the fact that certain published approaches may directly render channels with electrodes without post-treatment, the control of channels’ diameter and edge distance is a challenge that may be exploited to investigate and optimize the relationship between channels and fast-charging electrodes. Moreover, the intricacy of these methods precludes their industrialization and commercialization. From the perspective of industrial and precision control channels, Roll-to-roll (R2R) screen printing is a simple, cost-effective, industrially scalable, and pattern-customizable continuous additive manufacturing approach for producing vertical channels, reducing the tortuosity of electrodes, and improving their fast-charging capabilities. Low-tortuosity electrodes manufactured by screen printing may be utilized to research the relationship between channel architecture and electrochemical performances of electrodes, as well as to boost and broaden mechanism studies and commercial applications.In this work, we first applied screen printing to design and fabricate vertical channels with a high resolution. Channel arrangements, diameters, and edge distances were meticulously developed and illustrated for LIB electrodes in order to maximize their capacity at high current rates. Applying LiNi0.6Mn0.2Co0.2O2 cathode ink, clear patterns were printed on the Aluminum substrate. By comparing and filtering, we revealed that 1) the staggered configuration enhances the high-rate charge capabilities of electrodes and 2) the channel diameter and edge distances decreasing improve the rate performances of electrodes. Specifically, at 4 and 6 C, the optimized electrode possesses a charge capacity that is two- and seven-times greater than the conventional bar-coated electrodes, respectively. In addition, neutron computed tomography demonstrated that the Li of the screen-printed electrodes was homogeneously spread along the channels during the charge and discharge operations. We believe that optimized channels accelerate ion transfer in the vertical direction, promote ion diffusion in the horizontal direction, and maximize transfer kinetics for electrodes. Although more research is required to improve the greatest resolution of screen printing technology and refine the internal design of screen-printed electrodes, R2R screen printing technology offers a new opportunity for the optimization, industrialization, and commercialization of fast-charging LIBs.

Assessing the Impact of Thick Electrode Structure on the Fast Charge Performance of Lithium-Ion Batteries

The lithium-ion battery (LIB) is a key technology for inexpensive, renewable, and safe energy storage system, but there are a few challenges that need to be addressed to make LIB more efficient. One critical challenge is increasing both energy density and fast charging capability. Increasing electrode thickness can increase the energy density of lithium-ion batteries. However, increasing electrode thickness increases transport limitations and the risk of lithium plating, which limit safe fast charging capability. This work analyzes prospective improvements to the conventional lithium-ion cell electrode structure that may facilitate high energy density and fast charging capabilities. A 2D lithium-ion battery model is applied to five different cell designs to understand the impact of thick electrode structure on performance at different charge and discharge rates for a single cell. These five different cell designs consist of one conventional cell and four cells with electrodes modified by varied electrolyte channel arrangements. The simulated electrodes were taken as Li(Ni1/3Mn1/3Co1/3)O2 (NMC) for the cathode and graphite for the anode. The simulated electrolyte was 1 M lithium hexafluorophosphate (LiPF6) in 1:1 ethylene carbonate (EC) and diethylene carbonate (DEC). All five cells were simulated under discharge at C/10, C/2 and 1C followed by charge at 1C, 3C, and 5C with no rest time prior to charge. Adding electrolyte channels on the anode side was found to facilitate lithium ion transport and reduce the risk of lithium plating. Modification of both electrodes did not present any benefit compared to the conventional cell. Analysis of cell behavior based on mass transport Fourier number and a dimensionless mass flux parameter was performed to compare different electrodes at different charge and discharge conditions. These dimensionless parameters provide a means for the general assessment of prospective electrode structure modifications.

(Invited) Bi-Layer Cathodes Comprising Different Active Material Sublayers Demonstrate Superior Fast Charge Capability

Sluggish electrolyte transport properties result in a tradeoff between energy density and rate capability in lithium-ion batteries. To increase energy density, electrodes are made thicker and less porous. However, once thick enough, lithium transport in the electrolyte becomes the rate limiting process, and capacities at elevated C rates are reduced as a result of underutilisation of active material near the current collector. Strategies have been proposed to overcome these limitations, including pore engineering to reduce through-plane tortuosity, to varying degrees of success.We introduce bilayer cathodes that aim to improve the rate performance of thick electrodes by controlling the through-thickness charging rate. The bilayer cathode structure is comprised of two discrete sublayers containing the active materials lithium iron phosphate (LFP) and lithium nickel manganese cobalt oxide (NMC). Due to LFP and NMC having open-circuit voltage (OCV) profiles in different voltage windows, the through-thickness charging rate is dependent on the location of the two active materials. The bilayer electrodes are manufactured by multi-pass doctor blade coating and, in principle, could also be produced using twin-slot dies which would require only a minor modification to the current commercial manufacturing methods. The electrochemical performance of the bilayer cathodes are compared with a blended electrode (single layer containing intimately mixed LFP and NMC) and a uniform NMC electrode, all at constant areal capacity (4.5 mAh cm-2) and porosity (30%). We report significant differences in voltage profiles when charging from 0% state of charge as well as intermediate (e.g. 50%) states of charge in electrodes containing the same mass fraction of LFP and NMC, demonstrating that the location of the active material through the electrode thickness impacts behaviour. Moreover, the best performing bilayer electrode structure (LFP layer adjacent to the current collector, NMC layer on top of the LFP layer) outperforms the uniform NMC electrode in fast charge tests. At 3C, the best performing bilayer cathode maintains 84% of its capacity whilst the uniform NMC electrode maintains only 53%. In discharge, the same electrodes both maintain approximately 52% capacity at 3C, demonstrating the anisotropic charging/discharge performance introduced by the bilayer structure.An understanding of the through-thickness charging rate, and distribution of state of charge, throughout charging is required to explain why the bilayer cathode outperforms a conventional uniform cathode. In uniform electrodes, with the same active material through the thickness of the electrode, a gradient in state of charge is formed due to a gradient in resistance to charge through the electrode thickness. This is due to much higher ionic resistance within the electrolyte than the electronic resistance within the composite electrode. In thick electrodes this effect is pronounced enough so that at the end of charge there is far greater underutilisation of active material in the part of the electrode nearest the current collector. In the bilayer cathode structure, by placing active material with a lower OCV near the current collector, we can, somewhat counterintuitively, achieve much more even through-thickness charging compared to uniform electrodes, minimising underutilisation of active material near the current collector and increasing rate performance.

Development of Binder for Fast-Charging for Li-Ion Battery

In the recent years, fast-charging is a battery technology that continues to be in demand for portable devices, electric vehicles and grid storage. Especially, fast charging capability has become one of the key features targeted by battery and EV industries. However, charging at high rates has been shown to accelerate degradation, causing both the capacity and power capability of batteries to deteriorate. In addition, the efficiency of fast charging depends on the materials and current in the battery, but also ambient temperature is emerging as an important issue. When the ambient temperature decreases, there is a decrease in performance and battery stability problems. This is the reason that the diffusion of Li-ion is slower in the electrodes and the electrolyte at low temperatures due to sluggish kinetics of interaction. Therefore, it is recommended to use low charging speed and voltage at low ambient temperature. In order to increase the fast charging efficiency, the material and battery design must be well designed, and among them, by improving the ionic conductivity of the binder, the resistance of the entire battery is lowered and the fast charging efficiency is improved. In addition, the resistance of material change at low temperature and its effect on fast-charging were also examined.

Improving Fast Charging Capability of Graphite Anode Material Via Si/SiO x Coating for Lithium-Ion Battery

As the electric vehicle(EV) market is expanded, Lithium-ion batteries(LIBs) have faced a new challenge of fast charging. However, currently used graphite have limitation with poor kinetics and Li plating during fast charging process. To overcome this limitation, many materials have been researched for alternative of graphite materials. In this work, we propose Si/SiO x coated graphite material to improve fast charging capability and prevent Li plating. At a rate of 10 C-rate (3600 mA g-1), Si/SiO x coated graphite anode electrode exhibited 80.9 % of capacity obtained at a rate of 0.1 C-rate (36 mA g-1). Also, the Si/SiO x coated graphite is confirmed through the OCV behavior that Li plating is controlled. Therefore, surface modification by coating Si/SiO x on graphite anode material would be noticeable method to develop an anode material with fast charging ability for LIB. Detailed characteristic that material properties and electrochemical performance of Si/SiO x coated graphite will be discussed in the presentation.

Measuring Lithium Concentration Gradients during Fast Charging in an Optically Accessible Li-Ion Cell and Comparing to a 1D Numerical Model

Lithium-ion transport limitations hinder the fast charging capabilities of Li-ion batteries. At fast charging rates, insufficient transport can result in lithium concentration polarization, cell damage, and capacity loss. The magnitude of the lithium concentration polarization has been estimated with pseudo-2D (P2D) models, but has yet to be validated under fast charge conditions. In this research, we designed and built an optically accessible Li/Li symmetric cell and measured lithium concentration polarization in situ using FTIR. This novel cell design enabled the rapid collection of IR spectral images between electrodes at small timescales. From these in situ measurements, we can measure dynamic lithium concentration polarization at timescales relevant to fast charging. The IR imaging method was demonstrated in a Li/Li symmetric cell with an electrolyte of 1M LiPF6 in 50/50 ethylene carbonate/ethyl methyl carbonate (vol./vol) revealing lithium concentration gradients of over 2mM/mm. Results were compared with 1D numerical models utilizing concentration-dependent lithium transport properties. The comparison between our experimental and computational results gives insight into the limitations of models to adequately simulate transport in highly polarized cells. This test also showed promise for accurately measuring lithium transport properties in future experiments.

Multiscale dynamics of charging and plating in graphite electrodes coupling operando microscopy and phase-field modelling

The phase separation dynamics in graphitic anodes significantly affects lithium plating propensity, which is the major degradation mechanism that impairs the safety and fast charge capabilities of automotive lithium-ion batteries. In this study, we present comprehensive investigation employing operando high-resolution optical microscopy combined with non-equilibrium thermodynamics implemented in a multi-dimensional (1D+1D to 3D) phase-field modeling framework to reveal the rate-dependent spatial dynamics of phase separation and plating in graphite electrodes. Here we visualize and provide mechanistic understanding of the multistage phase separation, plating, inter/intra-particle lithium exchange and plated lithium back-intercalation phenomena. A strong dependence of intra-particle lithiation heterogeneity on the particle size, shape, orientation, surface condition and C-rate at the particle level is observed, which leads to early onset of plating spatially resolved by a 3D image-based phase-field model. Moreover, we highlight the distinct relaxation processes at different state-of-charges (SOCs), wherein thermodynamically unstable graphite particles undergo a drastic intra-particle lithium redistribution and inter-particle lithium exchange at intermediate SOCs, whereas the electrode equilibrates much slower at low and high SOCs. These physics-based insights into the distinct SOC-dependent relaxation efficiency provide new perspective towards developing advanced fast charge protocols to suppress plating and shorten the constant voltage regime.

3D Nanocomposite Thin Film Cathodes for Micro‐Batteries with Enhanced High‐Rate Electrochemical Performance over Planar Films

AbstractHigh energy and high power density rechargeable micro‐batteries are a necessity for powering the next generation of flexible electronics, internet of things, and medical technology devices. In theory, significant improvements in the capacity, current and power densities of micro‐batteries would result if 3D architectures with enhanced interdigitated component interface areas and shortened ion diffusion path‐lengths were used. Further gains are achievable if the materials utilized have high crystalline quality and are preferentially oriented for fast lithium intercalation. In this work, this is achieved by creating epitaxial thin film cathodes comprised of nanopillars of LiMn2O4 (LMO) embedded in a supporting matrix of electronically conducting SrRuO3 (SRO). The first electrochemical study of such a 3D vertically aligned nanocomposite (VAN) that displays clear cathode redox signatures is provided, and demonstrates remarkable capacity retention under high‐rate regimes. The electrochemical performance is shown to be dependent on the nanopillar topography, namely the crystallographic orientation, nanopillar dimensions, and electrode/electrolyte interfacial surface area. This work offers a pathway to realizing 3D architectured micro‐batteries with high‐capacity retention under high‐rate conditions enabling fast charge capabilities.

Investigating the efficiency of a novel combined Direct/Indirect thermal management system in optimizing the thermal performance of a new generation 46800-type LIB pack

Although the 46800-type Li-ion batteries have superior attributes, including high driving range, energy density, and fast charging capability, it is plagued by higher heat generation during discharge impacting performance, efficiency, and lifespan. To address this problem, a novel thermal management system is proposed utilizing direct/indirect liquid cooling with water, CuO nanofluid, and HFE-7100. Meshed separator plates are developed in the direct cooling channel to improve thermal uniformity and mitigate hot spots on LIBs. The numerical evaluation considers effects such as C-rate, coolant, separator wall, flow rates, flow direction, and ambient temperature on the thermal performance of the LIB pack. During a 3C discharge operation, compared to 1C, the LIB pack experiences a 7 °C increase in maximum temperature and a 4.1 °C temperature difference. However, with a 4% CuO nanofluid, these values decrease by 4.9 °C and 3 °C respectively, compared to water. A circular meshed separator wall improved the thermal performance of the battery pack by 22.7% compared to the non-wall condition. The inflow velocities of the direct and indirect cooling channels are increased from 0.2 to 0.3 m/s and from 0.1 to 0.2 m/s, respectively, which led to the 11.5% enhancement of the LIB pack’s thermal efficiency. Finally, the thermal performance of the proposed cooling system is assessed by considering various ambient temperatures ranging from 25 °C to 40 °C for the LIB pack. The results indicated that the optimized cooling system can maintain the maximum temperature of the LIB pack below 40 °C, even at an ambient temperature of 35 °C.

To adopt rooftop solar or not along with electric vehicles? Exploring the factors influencing Co-adoption decisions among electric vehicle owners in California

Co-adoption of electric vehicles (EV) and photovoltaic (PV) technology can boost the environmental benefits of the two “green” technologies for society as well as the cost-saving benefits for co-adopters. This study contributes to the literature on this topic by investigating the factors influencing the co-adoption decision among EV owners in California, a leading market for the two complementary technologies. Analyzing data from a cohort survey of EV owners in California, using statistical analyses and logistic regression, we find that there are differences between co-adopters and EV-only households in terms of sociodemographic characteristics like dwelling type, income, and household size; economic factors like residential electricity rate plan; EV type, and electric range; and access to charging capabilities at home and work. Most of these factors also influence the intention of current only EV-owners to adopt PV or not in the future. These findings raise important policy questions regarding incentive needs to improve affordability and address equity issues as well as the need for pricing mechanisms at the utility level and by charging service providers to encourage co-adoption among EV owners.

In situ construction of uniform and robust cathode-electrolyte interface toward high-stable P2-Type sodium layered oxide cathodes

As a kind of potential cathode for sodium-ion batteries (SIBs), P2-type Na2/3Ni1/3Mn2/3O2 (P2-NNMO) suffers from the dissolution of transition metals and severe side reactions in conventional electrolytes, which greatly deteriorates its electrochemical performance. Herein, an artificial cathode-electrolyte interface (CEI) is in situ constructed on P2-NNMO cathode based on a spontaneous redox reaction between P2-NNMO material and organic solvent tetrahydrofuran (THF). The uniform and robust CEI layer on P2-NNMO cathode (named P2-NNMO-T) mainly comprises organic Na-based species (R-O-Na, R-CO-Na, and R-O2CO-Na), and converts from an initial thickness of 2 nm into 4.6 nm after cycling. It can serve as a versatile interlayer to facilitate Na+ transport, shield the attack of electrolyte solvents, and suppress the transition metal dissolution effectively, thus boosting the cycling stability and fast charging capability of P2-NNMO cathodes. More importantly, the concept of in situ CEI construction can be extended to other layered oxides beyond SIBs discussed herein.

Electric Vehicle Advancements, Barriers, and Potential: A Comprehensive Review

Electric vehicles (EVs) have emerged as a promising solution to address environmental concerns and transform the transportation sector. This paper examines the state-of-the-art EVs, encompassing their history, definition, and different types. The advantages and limitations of each type are compared and contrasted, providing insights into their unique characteristics and potential applications. Critical components of EVs are thoroughly analyzed. The paper explores various types of batteries, emphasizing their features and potential for improving energy density, range, and charging capabilities. Charging infrastructure is discussed, highlighting the importance of establishing a robust network of charging stations. The impact of EVs on power grids is examined, emphasizing grid integration, load management, capacity upgrades, and power quality. Challenges and barriers hindering the wide adoption of EVs are identified, including technological limitations, infrastructure constraints, economic considerations, consumer perception, and policies. The paper delves into the environmental and economic impacts of EVs, including lifecycle analysis, air pollution reduction, and cost-effectiveness. Thus, the paper provides valuable insights into the current state of EVs and their potential to shape the future. The findings highlight the need for collaborative efforts from industry stakeholders, governments, researchers, and consumers to overcome challenges and accelerate the transition to a sustainable transportation system.

SELF-SUSTAINED POWER FOR MOBILE DEVICES: A STEPPER MOTOR-DRIVEN SOLUTION

This study introduces a self-sustained power solution for mobile devices using a stepper motor-driven mechanism. The objective is to ensure reliable power supply during critical situations when traditional sources are unavailable. A prototype device was designed and experimentally evaluated.The device utilizes a stepper motor as a generator, converting mechanical energy into electrical energy through a hand crank. A full bridge rectifier transforms the generated alternating current into direct current compatible with mobile devices. A battery serves as the primary power storage, enabling energy accumulation.Experimental testing verified the device's performance. Mobile devices, including cellphones, laptops, and routers, were connected to assess charging capabilities. The results demonstrated successful charging, providing dependable power during outages and inaccessible charging methods.The findings establish the stepper motor-driven self-sustained power device as a practical emergency power solution. It empowers individuals to maintain communication channels and power mobile devices during critical situations, enhancing resilience. Its versatility and portability ensure effectiveness in diverse locations where conventional power sources are unreliable.In conclusion, this study presents a novel self-sustained power solution employing a stepper motor-driven mechanism. Experimental results confirm its capability to charge mobile devices, supporting communication and resilience during emergencies. The device has significant potential to benefit individuals and communities, providing reliable power and improving emergency response and communication capabilities.

A hybrid approach based energy management for building resilience against power outage by shared parking station for EVs

A major contribution of this work is to develop an efficient hybrid technique for building energy resilience against natural disasters, which cause power outages for commercial and residential buildings. The novelty of the proposed method is the combination of Chicken Search Optimization and the Spike Neural Network learning algorithm. The buildings are designed using shared electric vehicle parking station. Buildings are modeled with peer-to-peer functionality. Electric vehicle inside the parking station are available in a variety of forms, as the commercial building utilizes parking station at day time, also the residential building mostly utilizes at midnight. These variations help vehicles to be utilized for additional hours. A building is maintained through power management options to deal with these interruptions. The choices include peer-to-peer building operation, electric vehicle charging and discharging, partial charge capability, load reduction, and load adjustment. The proposed technique makes use of building components and does not require any additional components for building energy management. The main contribution of this paper is to diminish energy costs and increase energy resilience to natural disasters. Resiliency is described as the ability to restore harmful loads while experiencing minimum power loss after successive power outages. The performance of the proposed system is evaluated using the MATLAB platform and compared to existing systems.

Enhancing the Whole Migration Kinetics of Na+ in the Anode Side for Advanced Ultralow Temperature Sodium‐Ion Hybrid Capacitor

AbstractBoosting the ultralow temperature (below −30 °C) performance of Na‐ion hybrid capacitors (SIHCs), which integrate the high energy density of batteries with the high output power and long life of supercapacitors, is critical for the application of advanced electronics in extreme environments. However, their low‐temperature performance, especially fast charging capability, is hindered by difficult desolvation and slow pass solid electrolyte interphase (SEI) together with sluggish diffusion within the electrode. Herein, a “single‐solute–single‐solvent” electrolyte is developed and a through‐hole hollow carbon sphere (TH‐HCS) is constructed, and it is demonstrated through theoretical calculations and experimental investigations that the weakly solvated structure and high ionic conductivity facilitate the Na+ transportation at low temperatures, the highly fluorinated SEI facilitates the Na+ migration, and the through‐hole hollow structure alleviates the volume expansion during sodiation, thus ensuring fast kinetics and structural stability. As expected, TH‐HCS using this electrolyte exhibits a high specific capacity of 87.5 mAh g−1 after 11 000 cycles at 1.0 A g−1 and −40 °C. Coupled with activated carbon, the assembled SIHC displays an energy density of 106.1 and 52.0 Wh kg−1 at 25 and −40 °C, respectively, far exceeding the performance of commercial energy storage systems at low temperature.

Multimodal investigation of electronic transport in PTMA and its impact on organic radical battery performance

Organic radical batteries (ORBs) represent a viable pathway to a more sustainable energy storage technology compared to conventional Li-ion batteries. For further materials and cell development towards competitive energy and power densities, a deeper understanding of electron transport and conductivity in organic radical polymer cathodes is required. Such electron transport is characterised by electron hopping processes, which depend on the presence of closely spaced hopping sites. Using a combination of electrochemical, electron paramagnetic resonance (EPR) spectroscopic, and theoretical molecular dynamics as well as density functional theory modelling techniques, we explored how compositional characteristics of cross-linked poly(2,2,6,6-tetramethyl-1-piperidinyloxy-4-yl methacrylate) (PTMA) polymers govern electron hopping and rationalise their impact on ORB performance. Electrochemistry and EPR spectroscopy not only show a correlation between capacity and the total number of radicals in an ORB using a PTMA cathode, but also indicates that the state-of-health degrades about twice as fast if the amount of radical is reduced by 15%. The presence of up to 3% free monomer radicals did not improve fast charging capabilities. Pulsed EPR indicated that these radicals readily dissolve into the electrolyte but a direct effect on battery degradation could not be shown. However, a qualitative impact cannot be excluded either. The work further illustrates that nitroxide units have a high affinity to the carbon black conductive additive, indicating the possibility of its participation in electron hopping. At the same time, the polymers attempt to adopt a compact conformation to increase radical–radical contact. Hence, a kinetic competition exists, which might gradually be altered towards a thermodynamically more stable configuration by repeated cycling, yet further investigations are required for its characterisation.

A solution-to-solid conversion chemistry enables ultrafast-charging and long-lived molten salt aluminium batteries

Conventional solid-to-solid conversion-type cathodes in batteries suffer from poor diffusion/reaction kinetics, large volume changes and aggressive structural degradation, particularly for rechargeable aluminium batteries (RABs). Here we report a class of high-capacity redox couples featuring a solution-to-solid conversion chemistry with well-manipulated solubility as cathodes—uniquely allowed by using molten salt electrolytes—that enable fast-charging and long-lived RABs. As a proof-of-concept, we demonstrate a highly reversible redox couple—the highly soluble InCl and the sparingly soluble InCl3—that exhibits a high capacity of about 327 mAh g−1 with negligible cell overpotential of only 35 mV at 1 C rate and 150 °C. The cells show almost no capacity fade over 500 cycles at a 20 C charging rate and can sustain 100 mAh g−1 at 50 C. The fast oxidation kinetics of the solution phase upon initiating the charge enables the cell with ultrafast charging capability, whereas the structure self-healing via re-forming the solution phase at the end of discharge endows the long-term cycling stability. This solution-to-solid mechanism will unlock more multivalent battery cathodes that are attractive in cost but plagued by poor reaction kinetics and short cycle life.

Aging of a dielectric fluid used for direct contact immersion cooling of batteries

Batteries of electric vehicles require appropriate cooling to allow for increased performances such as high energy density and fast charging capabilities. Immersion of the cells in a dielectric fluid provides substantial benefits in terms of safety and performance, but the selection of a relevant coolant remains a complex task and guidance to engineers in the field of vehicle electrification is sparce. This paper reviews the fluid properties which are considered most significant for this application, and provides an experimental comparison of the key properties of one candidate fluid under various aging conditions devised to reproduce several years of operation in a vehicle.

A flexible triboelectric nanogenerator based on PVA/PTT/LiCl conductive hydrogel for gait monitoring in basketball

Recently, wearable flexible sensors for intelligent sports monitoring have attracted much attention. In this work, we designed the polyvinyl alcohol (PVA)/polytrimethylene terephthalate (PTT)/LiCl hydrogel to act as the flexible conductive of triboelectric nanogenerator (PPL-TENG). Significantly, the PPL-TENG device has high transparency and stretchability, demonstrating excellent ability in complex mechanical energy harvesting. From the results, the PPL-TENG achieve the maximum power density of 159.6 µW cm−2. In addition, the PVA/PTT/LiCl hydrogel exhibits good mechanical properties, thus endowing PPL-TENG devices with excellent application value. Also, the electrical output of PPL-TENG exhibits good stability and excellent fast charging capability. In addition to mechanical energy harvesting, PPL-TENG also has excellent sensing performance and can be used as a self-powered sensor for basketball motion monitoring. After experimental testing, PPL-TENG can recognize the characteristics of body joints and gait in basketball, which will play an auxiliary role in basketball sports. This research will promote the development of intelligent wearable sports devices.