Flexible bidirectional pulse charging regulation achieving long-life lithium-ion batteries

Typical application scenarios,such as vehicle to grid(V2G)and frequency regulation,have imposed significant long-life demands on lithium-ion batteries.Herein,we propose an advanced battery life-extension method employing bidirectional pulse charging(BPC)strategy.Unlike traditional constant current charging methods,BPC strategy not only achieves comparable charging speeds but also facilitates V2G frequency regulation simultaneously.It significantly enhances battery cycle ampere-hour throughput and demonstrates remarkable life extension capabilities.For this interesting conclusion,adopting model identification and postmortem characterization to reveal the life regulation mechanism of BPC:it mitigates battery capacity loss attributed to loss of lithium-ion inventory(LLI)in graphite anodes by intermittently regulating the overall battery voltage and anode potential using a negative charging current.Then,from the perspective of internal side reaction,the life extension mechanism is further revealed as inhibition of solid electrolyte interphase(SEI)and lithium dendrite growth by regulating voltage with a bidirectional pulse current,and a semi-empirical life degradation model combining SEI and lithium dendrite growth is developed for BPC scenarios health management,the model parameters are identified by genetic algorithm with the life simulation exhibiting an accuracy exceeding 99%.This finding indicates that under typical rate conditions,adaptable BPC strategies can extend the service life of LFP battery by approximately 123%.Consequently,the developed advanced BPC strategy offers innovative perspectives and insights for the development of long-life battery applications in the future.

High power nano-LiMn_2O_4 cathode materials with high-rate pulse discharge capability for lithium-ion batteries

Nano-LiMn2O4 cathode materials with nano-sized particles are synthesized via a citric acid assisted sol-gel route. The structure, the morphology and the electrochemical properties of the nano-LiMn204 are investigated. Compared with the micro-sized LiMn2O4, the nano-LiMn2O4 possesses a high initial capacity （120 mAh/g） at a discharge rate of 0.2 C （29.6 mA/g）. The nano-LiMn2O4 also has a good high-rate discharge capability, retaining 91% of its capacity at a discharge rate of 10 C and 73~ at a discharge rate of 40 C. In particular, the nano-LiMn2O4 shows an excellent high-rate pulse discharge capability. The cut-off voltage at the end of 50-ms pulse discharge with a discharge rate of 80 C is above 3.40 V, and the voltage returns to over 4.10 V after the pulse discharge. These results show that the prepared nano-LiMn2O4 could be a potential cathode material for the power sources with the capability to deliver very high-rate pulse currents.

Curbing Charging Currents in Pulsed Field Emission by Prolonging Pulse Edges

In field emission under a non-dc voltage, a displacement current is inevitable due to charging the cathode–anode condenser. Under an often-used square voltage pulse, in which the voltage rises from zero to a certain value abruptly, the charging current in the circuit is very large at the rising and falling edges. This large charging current makes measurement of the actual emissive current from the cathode difficult, constitutes a threat to the components in the circuit and causes attenuation of the emissive current within the pulse. To alleviate these drawbacks, trapezoid voltage pulses, whose rising edges are extended dramatically in comparison with square voltage pulses, are employed to extract the field emission. Under a trapezoid voltage pulse, the charging current is clearly lowered as expected. Furthermore, the heat generated by the charging current under the trapezoid voltage pulse is much smaller than that under the square voltage pulse. Hence the emissive current does not show any attenuation within the pulse. Finally, the average emissive currents are found to decrease with the repetition frequency of the pulses.

Effects of Tailed Pulse-Bias on Ion Energy Distributions and Charging Effects on Insulating Substrates

Abstract A hybrid sheath model, including a fluid model and a Monte Carlo （MC） method, is proposed to study ion energy distributions （IEDs） driven by a radiofrequency （RF） with a tailed pulse-bias on an insulating substrate, where a charging effect is obviously caused by the ions accumulated. This surface charging effect will significantly affect the IEDs on the insulating substrate. In this paper, a voltage compensation method is employed to eliminate the charging effect by making the pulse-bias waveform have a certain gradient. Furthermore, we investigate the IEDs under the condition of different pulse-bias duty ratios, waveforms, amplitudes, and cycle proportions. It is found that the parameters of the pulsed source can effectively modulate the IEDs on the insulating substrate and the charging effect, and more desired IEDs are obtained by using the voltage compensation method with modulations of pulse parameters.

Numerical Simulation of Properties of Charged Particles Initiated by Underwater Pulsed Discharge

Governing conservation equations for energy, momentum, mass and charge were deduced. Based upon these equations and the Saha equation, the particle density, temperature and pressure of the channel initiated by underwater pulsed discharge, are simulated. Influence of temperature and pressure on particles density is also analyzed. Some of the simulation results are in an agreement with experimental results. The results will be helpful in further understanding of the formation mechanism of underwater pulsed discharge plasma.

Study on the Discharge Characteristics of a Coaxial Pulsed Plasma Thruster

A new coaxial pulsed plasma thruster （PPT） laboratory model is designed and employed in this study. A Teflon sleeve is connected with the anode, which is shaped as a nozzle, and a cathode is mounted in the cavity of the Teflon sleeve and kept in close contact with it. A thread is then designed in the internal surface of the Teflon sleeve, and because of the strong field strength of the cathode triple junction （CTJ）, vacuum flashover occurs and a plasma jet is acquired behind the anode. The electric field distribution of the designed coaxial PPT laboratory model is simulated by MAXWELL 3D simulation software, and the plasma density and thrust are measured by a Langnmir probe and a piezoelectric thin-film sensor, respectively. Through a series of comparative experiments, we discuss the impact of optimal designs, such as the thread and the nozzle-shaped anode, on the discharge characteristics of the coaxial PPT. The experimental and simulation results indicate that the designed coaxial PPT laboratory model presents better discharge characteristics in view of its higher plasma density and greater thrust.

Burst pulses for positive corona discharges in atmospheric air:the collective movement of charged species

Positive corona burst pulses are an unstable pulse mode.They appear in a small range of the onset stage,and their current pulses result from the collective movement of charged species.This paper focused on the connections between these pulses and the collective movement of charged species.The movement of species is divided into four parts with respect to time:the(1)initial growth of species,(2)formation and development of the streamer region and negative ion sheath,(3)dead time(the time interval between the pulses),and(4)rapid re-growth of species.The movement of the species in the four parts and the correspondence with the current pulse were analyzed.The numerical results indicated the following:the rapid rising of the species matched the rising edge of the pulses,the streamer region,and negative ion sheath appeared in the falling edge of the primary pulse,and the rapid re-growth of species matched the re-ignition of the pulses.The results were in qualitative agreement with deductions and experimental observations in the literature.

Investigating the Thermal Stress of Millisecond Pulsed Laser Irradiation on Charge-Coupled Devices

In this study, a two-dimensional model describing thermal stress on a charge-coupled device (CCD) induced by ms laser pulses was examined. Considering the nonlinearity of the CCD’s material parameters and the melting phase transition process of aluminum electrode materials was considered by using equivalent specific heat capacity method, the physical process where a laser pulse irradiating a CCD pixel array was simulated using COMSOL Multiphysics software. The temperature field and thermal stress field were calculated and analyzed. In order to clarify the mechanism producing damage on the CCD detector, Raman spectra from silicon were measured with a micro-Raman spectrometer to determine stress change in the CCD chip. The procedure presented herein illustrates a method for evaluating strain in a CCD after laser irradiation.

Study of the influence of discharge loop parameters on anode side on generation characteristics of metal plasma jet in a pulsed vacuum discharge

In a pulsed vacuum discharge,the ejection performance of a metal plasma jet can be effectively improved by preventing charged particles from moving to the anode.In this paper,the effects of resistance and capacitance on the anode side on the discharge characteristics and the generation characteristics of plasma jet are investigated.Results show that the existence of a resistor on the anode side can increase the anode potential,thereby preventing charged particles from entering the anode and promoting the ejection of charged particles along the axis of the insulating sleeve nozzle.The application of a capacitor on the anode side can not only absorb electrons at the initial stage of discharge,increasing the peak value of the cathode hump potential,but also prevent charged particles from moving to the anode,thereby improving the ejection performance of the plasma jet.In addition,the use of a larger resistance and a smaller capacitance can improve the blocking effect on charged particles and further improve the ejection performance of the plasma jet.Results of this study will provide a reference for the improvement of the ejection performance of plasma jets and their applications.

Charge Accumulation Characteristics of SF6-Epoxy Interface Under Negative Repetitive Nanosecond Pulses

Repetitve nanosecond impulses in gas-insulated metal-enclosed switchgear (GIS) are likely to trigger inside flashover. Interface charges on the spacer in GIS are considered one of the main factors damaging insulation performance and may be induced by overvoltage. For good understanding of insulation failures, accumulation characteristics of charges between SF6 and epoxy spacers under repetitive nanosecond impulses are investigated. It can be found under nanosecond impulses, the charge source in gas volume contributes to interface charge accumulation predominantly. Interface charges will be promoted by impulse number and amplitude. Accumulation processes are analyzed based on runaway electrons mechanism. When impulse amplitude exceeds a threshold value, discharge in the gas volume turns to a runaway mode. A runaway electron leads to the interface charge accumulation. Affected by motion of the runaway electrons, the potential peak gradually moves close to the grounded electrode when impulse amplitude is raised. Meanwhile, increasing impulse number can enhance surface potential. Surface potential will reach saturation eventually. However, memory effect of the repetitive impulse discharge makes the half-peak width of the surface potential at the interface change little. Design of GIS gas-solid insulations can refer to this research.

Performance improvement of lithium-ion battery by pulse current

Periodically changed current is called pulse current.It has been found that using the pulse current to charge/discharge lithium-ion batteries can improve the safety and cycle stability of the battery.In this short review,the mechanisms of pulse current improving the performance of lithium-ion batteries are summarized from four aspects:activation,warming up,fast charging and inhibition of lithium dendrites.Related content may help us use the pulse current to improve the performance of lithium-ion batteries and further optimize pulse current technology.

An ultra-fast charging strategy for lithium-ion battery at low temperature without lithium plating

Conventional charging methods for lithium-ion battery(LIB)are challenged with vital problems at low temperatures:risk of lithium(Li)plating and low charging speed.This study proposes a fast-charging strategy without Li plating to achieve high-rate charging at low temperatures with bidirectional chargers.The strategy combines the pulsed-heating method and the optimal charging method via precise control of the battery states.A thermo-electric coupled model is developed based on the pseudo-twodimensional(P2D)electrochemical model to derive charging performances.Two current maps of pulsed heating and charging are generated to realize real-time control.Therefore,our proposed strategy achieves a 3 C equivalent rate at 0℃ and 1.5 C at-10℃ without Li plating,which is 10–30 times faster than the traditional methods.The entropy method is employed to balance the charging speed and the energy efficiency,and the charging performance is further enhanced.For practical application,the power limitation of the charger is considered,and a 2.4 C equivalent rate is achieved at 0℃ with a 250 kW maximum power output.This novel strategy significantly expands LIB usage boundary,and increases charging speed and battery safety.

Effect of supply voltage and body-biasing on single-event transient pulse quenching in bulk fin field-effect-transistor process

Charge sharing is becoming an important topic as the feature size scales down in fin field-effect-transistor （FinFET） technology. However, the studies of charge sharing induced single-event transient （SET） pulse quenching with bulk FinFET are reported seldomly. Using three-dimensional technology computer aided design （3DTCAD） mixed-mode simulations, the effects of supply voltage and body-biasing on SET pulse quenching are investigated for the first time in bulk FinFET process. Research results indicate that due to an enhanced charge sharing effect, the propagating SET pulse width decreases with reducing supply voltage. Moreover, compared with reverse body-biasing （RBB）, the circuit with forward body-biasing （FBB） is vulnerable to charge sharing and can effectively mitigate the propagating SET pulse width up to 53% at least. This can provide guidance for radiation-hardened bulk FinFET technology especially in low power and high performance applications.

Anti-noise performance of the pulse coupled neural network applied in discrimination of neutron and gamma-ray

In this study,the anti-noise performance of a pulse-coupled neural network(PCNN)was investigated in the neutron and gamma-ray(n-γ)discrimination field.The experiments were conducted in two groups.In the first group,radiation pulse signals were pre-processed using a Fourier filter to reduce the original noise in the signals,whereas in the second group,the original noise was left untouched to simulate an extremely high-noise scenario.For each part,artificial Gaussian noise with different intensity levels was added to the signals prior to the discrimination process.In the aforementioned conditions,the performance of the PCNN was evaluated and compared with five other commonly used methods of n-γdiscrimination:(1)zero crossing,(2)charge comparison,(3)vector projection,(4)falling edge percentage slope,and(5)frequency gradient analysis.The experimental results showed that the PCNN method significantly outperforms other methods with outstanding FoM-value at all noise levels.Furthermore,the fluctuations in FoM-value of PCNN were significantly better than those obtained via other methods at most noise levels and only slightly worse than those obtained via the charge comparison and zerocrossing methods under extreme noise conditions.Additionally,the changing patterns and fluctuations of the FoMvalue were evaluated under different noise conditions.Hence,based on the results,the parameter selection strategy of the PCNN was presented.In conclusion,the PCNN method is suitable for use in high-noise application scenarios for n-γdiscrimination because of its stability and remarkable discrimination performance.It does not rely on strict parameter settings and can realize satisfactory performance over a wide parameter range.

Dynamic energy spectrum and energy deposition in solid target by intense pulsed ion beams

A method for analyzing the dynamic energy spectrum of intense pulsed ion beam(IPIB) was proposed.Its influence on beam energy deposition in metal target was studied with IPIB produced by two types of magnetically insulated diodes(MID).The emission of IPIB was described with space charge limitation model,and the dynamic energy spectrum was further analyzed with time-of-flight method.IPIBs generated by pulsed accelerators of BIPPAB-450(active MID) and TEMP-4M(passive MID) were studied.The dynamic energy spectrum was used to deduce the power density distribution of IPIB in the target with Monte Carlo simulation and infrared imaging diagnostics.The effect on the distribution and evolution of thermal field induced by the characteristics of IPIB dynamic energy spectrum was discussed.

Deposition of SiCxHyOz thin film on epoxy resin by nanosecond pulsed APPJ for improving the surface insulating performance

Non-thermal plasma surface modification for epoxy resin（EP）to improve the insulation properties has wide application prospects in gas insulated switchgear and gas insulatedtransmission line.In this paper,a pulsed Ar dual dielectrics atmospheric-pressure plasma jet（APPJ）was used for Si CxHyOzthin film deposition on EP samples.The film deposition was optimized by varying the treatment time while other parameters were kept at constants（treatment distance：10 mm,precursor flow rate：0.6 l min-（-1）,maximum instantaneous power：3.08 k W and single pulse energy：0.18 m J）.It was found that the maximum value of flashover voltages for negative and positive voltage were improved by 18%and 13%when the deposition time was3 min,respectively.The flashover voltage reduced as treatment time increased.Moreover,all the surface conductivity,surface charge dissipation rate and surface trap level distribution reached an optimal value when thin film deposition time was 3 min.Other measurements,such as atomic force microscopy and scanning electron microscope for EP surface morphology,Fourier transform infrared spectroscopy and x-ray photoelectron spectroscopy for EP surface compositions,optical emission spectra for APPJ deposition process were carried out to better understand the deposition processes and mechanisms.The results indicated that the original organic groups（C–H,C–C,C=O,C=C）were gradually replaced by the Si containing inorganic groups（Si–O–Si and Si–OH）.The reduction of C=O in ester group and C=C in p-substituted benzene of the EP samples might be responsible for shallowing the trap level and then enhancing the flashover voltage.However,when the plasma treatment time was longer than 3 min,the significant increase of the surface roughness might increase the trap level depth and then deteriorate the flashover performance.

A single-event transient induced by a pulsed laser in a silicon-germanium heterojunction bipolar transistor

A study on the single event transient （SET） induced by a pulsed laser in a silicon-germanium （SiGe） heterojunction bipolar transistor （HBT） is presented in this work. The impacts of laser energy and collector load resistance on the SET are investigated in detail. The waveform, amplitude, and width of the SET pulse as well as collected charge are used to characterize the SET response. The experimental results are discussed in detail and it is demonstrated that the laser energy and load resistance significantly affect the SET in the SiGe HBT. Furthermore, the underlying physical mechanisms are analyzed and investigated, and a near-ideal exponential model is proposed for the first time to describe the discharge of laser-induced electrons via collector resistance to collector supply when both base-collector and collector-substrate junctions are reverse biased or weakly forward biased. Besides, it is found that an additional multi-path discharge would play an important role in the SET once the base-collector and collector-substrate junctions get strongly forward biased due to a strong transient step charge by the laser pulse.

Nonlinear Response Analysis for Insulation Diagnosis of Water-tree Aged 10 kV XLPE Cable Using Pulse Voltage

The diagnosis of water trees of cable insulation is of great importance as the water-treeing is a primary cause of aging breakdown for the middle voltage cables. In this paper, it is described how the water-tree-aged 10 kV XLPE cables were diagnosed. The cables were subjected to electrical stress of 5.9 kV/mm and a thermal load cycle in a curved water-filled tube for 3, 6 and 12 months of aging in accor- dance with the accelerated water-tree test method. The aged cables were used as the samples for water-tree diagnosis. First, the water-tree degraded cable, was charged by a DC voltage, and then the cable was grounded while a pulse voltage was applied to it for releasing the space charge trapped in the water trees. The amount of the space charge, which corresponds to the deterioration degree of the water trees, was calculated. The effects of DC voltage amplitude, pulse voltage repetition rate and aging conditions on the amount of the space charge were studied. Obtained results show that the amount of the space charge has a positive correlation with the applied DC voltage and the ag- ing time of the cables, and that a peak value of space charge appears with the increase of the pulse voltage repetition rate. An optimum pulse voltage repetition rate under which the space charge can be released rapidly is obtained. Furthermore, the releasing mechanism of space charge by the pulse voltage is discussed. Accumulated results show that the presented method has a high resolution for the diagnosis of water tree degradation degree and is expected to be applied in practice in future.

A pulse shape discrimination of CsI(Tl) crystal with ~6He beam

The performance test of a CsI(Tl) crystal (70×27×23 mm3) was performed by applying the pulse shape discrimination technique for identification of light charged particles .The crystal is coupled to a photomultiplier tube during an experiment with 6He beam.The pulse waveform is fully recorded by employing a high precision digital oscilloscope.The fast and slow gates are used for the pulse shape discrimination and the best values for the gate widths were determined to be 0.5 μs and 1.67 μs,respectively.The 6He,4He and 3He are successfully discriminated with this technique.

A High Power Semiconductor Switch RSD for Pulsed Power Applications

High power switch is one of the most important components in pulsed power technology. The RSD （Reversely Switched Dynistor）, turned on by a thin layer of an electron-hole plasma, is a high power semiconductor switch. In this study, the RSD turn-on conditions were investigated by numerical analysis and device simulation as well as the experiments conducted to validate the turn-on conditions. A design of a triggering high-voltage RSD is presented based on a saturable transformer.