Li-ion battery temperature estimation based on recurrent neural networks

The monitoring of Li-ion battery temperatures is essential to ensure high efficiency and safety.In this work,two types of recurrent neural networks (RNNs),which are long short-term memory-RNN (LSTM-RNN) and gated recurrent unit-RNN(GRU-RNN),are proposed to estimate the surface temperature of 18650 Li-ion batteries during the discharging processes under different ambient temperatures.The datasets acquired from the Prognostics Center of Excellence (PCo E) of NASA are used to train,validate and test the networks.In previous work,temperature has been set as the output of the networks;however,here the temperature difference along the time axis is adopted as the output.The net heat generated results in net temperature change,which is more closely aligned with electrochemical and thermodynamic laws.Extensive simulation results show that the two RNNs can achieve accurate real-time battery temperature estimation.The maximum absolute error in temperature estimation is approximately 0.75°C and the correlation coefficient between the estimated and measured temperature curves is greater than 0.95.The influences of three crucial parameters,which are the number of hidden neurons,initial learning rate and maximum number of iterations,are also assessed in terms of training time,root mean square error and mean absolute error.

High performance room temperature all-solid-state Na-SexS battery with Na3SbS4-coated cathode via aqueous solution

All-solid-state(ASS)Na-S batteries are promising for large-scale energy storage because of the incombustible solid electrolyte and avoiding the dissolution of intermediates.However,the poor contact between the active material and the solid electrolyte in the positive electrode leads to poor electrochemical performance.Here,we report an aqueous solution approach to fabricate Na3SbS4-coated SexS-based active materials for a Na-S battery working at room temperature.Compared with the Na3SbS4 and SexS mixed cathode,the coated cathode achieves significantly improved Na-ion diffusion kinetics and reduced impedance resistance.Additionally,the nanoparticle coating sustains the volume expansion of the cathode during cycling.The resulting batteries deliver an intensively enhanced specific capacity at various rates.Regardless of the mass loading,the Na3SbS4-coated cathode maintains a decent reversible capacity for the long-term discharge/charge cycling.The best battery achieves an initial discharge capacity of509 mAh g^-1 at a current density of 437.4 mA g^-1 and capacity retention of 98.9%for 100 cycles.To the best of our knowledge,this is one of the best room temperature ASS Na-S battery so far.This work demonstrates that Na3SbS4 is very promising for the cathode coating purpose for ASS Na-S batteries.

Role of Catalytic Materials on Conversion of Sulfur Species for Room Temperature Sodium–Sulfur Battery

Room temperature sodium–sulfur(RT Na-S)battery with high theoretical energy density and low cost has spurred tremendous interest,which is recognized as an ideal candidate for large-scale energy storage applications.However,serious sodium polysulfide shutting and sluggish reaction kinetics lead to rapid capacity decay and poor Coulombic efficiency.Recently,catalytic materials capable of adsorbing and catalyzing the conversion of polysulfides are profiled as a promising method to improve electrochemical performance.In this review,the research progress is summarized that the application of catalytic materials in RT Na-S battery.For the role of catalyst on the conversion of sulfur species,specific attention is focused on the influence factors of reaction rate during different redox processes.Various catalytic materials based on lightweight and high conductive carbon materials,including heteroatom-doped carbon,metals and metal compounds,single-atom and heterostructure,promote the reaction kinetic via lowered energy barrier and accelerated charge transfer.Additionally,the adsorption capacity of the catalytic materials is the key to the catalytic effect.Particular attention to the interaction between polysulfides and sulfur host materials is necessary for the exploration of catalytic mechanism.Lastly,the challenges and outlooks toward the desired design of efficient catalytic materials for RT Na-S battery are discussed.

A novel one-step reaction sodium-sulfur battery with high areal sulfur loading on hierarchical porous carbon fiber

Room temperature sodium-sulfur(RT Na-S)batteries are gaining extensive attention as attractive alternatives for large-scale energy storage,due to low cost and high abundancy of sodium and sulfur in nature.However,the dilemmas regarding soluble polysulfides(Na_(2)Sn,4<n<8)and the inferior reaction kinetics limit their practical application.To address these issues,we report the activated porous carbon fibers(APCF)with small sulfur molecules(S2-4)confined in ultramicropores,to achieve a reversible single-step reaction in RT Na-S batteries.The mechanism is investigated by the in situ UV/vis spectroscopy,which demonstrates Na2S is the only product during the whole discharge process.Moreover,the hierarchical carbon structure can enhance areal sulfur loading without sacrificing the capacity due to thorough contact between electrolyte and sulfur electrode.As a consequence,the APCF electrode with 38 wt%sulfur(APCF-38S)delivers a high initial reversible specific capacity of 1412 mAh g^(-1) and 10.6mAh cm^(-2)(avg.areal sulfur loading:7.5 mg cm^(-2))at 0.1 C(1C=1675 mA g^(-1)),revealing high degree of sulfur utilization.This study provides a new strategy for the development of high areal capacity RT Na-S batteries.

Manipulating metal-sulfur interactions for achieving high-performance S cathodes for room temperature Li/Na-sulfur batteries

Rechargeable lithium/sodium-sulfur batteries working at room temperature(RT-Li/S,RT-Na/S)appear to be a promising energy storage system in terms of high theoretical energy density,low cost,and abundant resources in nature.They are,thus,considered as highly attractive candidates for future application in energy storage devices.Nevertheless,the solubility of sulfur species,sluggish kinetics of lithium/sodium sulfide compounds,and high reactivity of metallic anodes render these cells unstable.As a consequence,metal-sulfur batteries present low reversible capacity and quick capacity loss,which hinder their practical application.Investigations to address these issues regarding S cathodes are critical to the increase of their performance and our fundamental understanding of RT-Li/S and RT-Na/S battery systems.Metal-sulfur interactions,recently,have attracted considerable attention,and there have been new insights on pathways to high‐performance RT-Li/Na sulfur batteries,due to the following factors:(1)deliberate construction of metal-sulfur interactions can enable a leap in capacity;(2)metal-sulfur interactions can confine S species,as well as sodium sulfide compounds,to stop shuttle effects;(3)traces of metal species can help to encapsulate a high loading mass of sulfur with high‐cost efficiency;and(4)metal components make electrodes more conductive.In this review,we highlight the latest progress in sulfide immobilization via constructing metal bonding between various metals and S cathodes.Also,we summarize the storage mechanisms of Li/Na as well as the metal-sulfur interaction mechanisms.Furthermore,the current challenges and future remedies in terms of intact confinement and optimization of the electrochemical performance of RT-Li/Na sulfur systems are discussed in this review.

Multi-stage constant current charging strategy considering SOC intervals and voltage thresholds

Conventional multi-stage constant current charging strategies often use higher multiples of current to charge the battery in pursuit of shorter charging times.However,this leads to an increase in battery temperature,while shortening the charging time.This in turn affects the safety of the charging process.Furthermore,the higher charging currents are not ideal for shortening the charging time in the later stages of charging.To solve the aforementioned problems,in this study,a multi-stage constant current charging strategy is presented.This strategy can shorten the battery charging time by using the increase in battery temperature during the charging process as a constraint,using a genetic algorithm to calculate the charging current value,and investigating the phased approach to charging.Finally,the charging strategy is experimentally validated at different ambient temperatures and different initial SOCs.The experimental results show that the charging strategy proposed in this paper not only reduces the amount of calculations,but also reduces the temperature rise by up to 46.4%and charging time by up to 4.2%under different operating conditions.

Structural,electrochemical and cycling properties of Nb^(5+)doped LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2)cathode materials at different calcination temperatures for lithium-ion batteries

LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2)cathode material is prepared by sol-gel method and the effects of Nb^(5+)doping and different calcination temperatures on cathode materials were deeply investigated.Structural and morphological characterizations revealed that the optimal content of 1 mol%Nb^(5+)can stabilize layered structures,mitigate Ni^(2+)migration to Li layers,improve lithium diffusion capacity,and reduce lattice expansion/shrinkage while cycling.And calcination temperature at 800℃can not only ensure good morphology,but also suppress the mixed discharge of lithium and nickel in the internal structure.Electrochemical performance evaluation revealed that Nb^(5+)doping improves the discharge-specific capacity of the material,which is conducive to ameliorating its rate capability and cycle performance.And the material at 800℃exhibits the highest discharge specific capacity,the best magnification performance,low polarizability,and the best cycle reversibility.

Polyethylene Oxide-Coated Electrospun Polyimide Fibrous Seperator for High-Performance Lithium-Ion Battery

A polyethylene oxide （PEO）-coated polyimide （PI） membrane was prepared by electrospinning method followed by a dip-coating and drying process for high-performance lithium-ion batteries （LIB）. 8emicrystal PEO was covered on the surface of the fibers and partially enmeshed in PI matrix, which formed unique porous structures. The pores with an average size of 4.1 μm and a porosity of 90% served as ion transport channels. Compared with the cell with Celgard 2400 membrane, the half-cell using PEO-coated P1 membrane as a separator exhibits excellent electrochemical performance both at room temperature and at low temperature. The electrolyte uptaking rate of PEO-coated PI membrane was 170% and the ionic conductivity was 3.83 × 10^-3 S cm^-1. PEO-coated PI membrane possessed 5.3 V electrochemical window. The electrode-electrolyte interfacial resistance was 62.4 Ω. The capacity retention ratios with PEO- coated PI membrane were 86.4% at 5 C and 73.5% at 10 C at 25 ℃ and 75% at 5 C at 0 ℃. Furthermore, the cell using the separator demonstrates excellent capacity retention over cycling. These advanced characteristics would boost the application of the PEO-coated PI membrane for high-power lithium ion battery.

Reasonable suppression of polysulfides/polyselenides shuttle based on MXene in Na-SeS_(2)batteries

Metal-sulfur/selenium batteries have become the focus of new-generation energy storage systems due to the advantages of low-cost and high energy density.However,it still suffers from the notorious shuttle of polysulfides/polyselenides,poor electronic conductivity and tremendous volume expansion.Herein,a dual defense system for polysulfides/polyselenides was proposed and constructed based on MXene.The nitrogen-doped porous carbon(NPC)decorated by Ti_(3)C_(2)T_(x)MXene(M@NPC)was employed as the SeS_(2)host(SeS_(2)@M@NPC).Particularly,Ti_(3)C_(2)T_(x)sheets wrapped on NPC guarantee the rapid ion diffusion and serve as the first barrier for SeS_(2)and dissolved sodium polysulfides/polyselenides.Meanwhile,the few-layered Ti_(3)C_(2)T_(x)sheets coated on glass fiber separators act as the second barrier for alleviating the shuttle of polysulfides/polyselenides through physical interception and chemical adsorption.With this elaborate design,the integrated Na-SeS_(2)battery achieves a high specific capacity of 1243 mAh·g^(-1)at 1.0C,revealing a distinct superiority over its counterparts(SeS_(2)@M@NPC,1083mAh·g^(-1)at 0.5C;and SeS_(2)@NPC,823 mAh·g^(-1)at 0.5C).The findings gained in this work provide a creative idea for the construction of durable room-temperature Na-SeS_(2)batteries based on MXenes and their derivative materials.

Monitoring of lithium-ion cells using a microcontroller

Safe and efficient operation of batteries is always desired but batteries with a high energy density pose a threat to the system causing thermal breakdown,reduced performance and rapid ageing.To reduce such vulnerabilities,an optimum environment with controlled parameters is required.Four parameters have been considered for analysis,i.e.state of charge,current,voltage and temperature.The module makes a detailed analysis of the above-mentioned parameters and suggests a microcontroller-based prototype that is capable of monitoring the external factors in real time and generating relevant warnings.