Bidirectional Conversion Research Articles

A new role for phosphoinositides in regulating mitochondrial dynamics

Phosphoinositides are a minor group of membrane-associated phospholipids that are transiently generated on the cytoplasmic leaflet of many organelle membranes and the plasma membrane. There are seven functionally distinct phosphoinositides, each derived via the reversible phosphorylation of phosphatidylinositol in various combinations on the inositol ring. Their generation and termination is tightly regulated by phosphatidylinositol-kinases and –phosphatases. These enzymes can function together in an integrated and coordinated manner, whereby the phosphoinositide product of one enzyme may subsequently serve as a substrate for another to generate a different phosphoinositide species. This regulatory mechanism not only enables the transient generation of phosphoinositides on membranes, but also more complex sequential or bidirectional conversion pathways, and phosphoinositides can also be transferred between organelles via membrane contacts. It is this capacity to fine-tune phosphoinositide signals that makes them ideal regulators of membrane organization and dynamics, through their recruitment of signalling, membrane altering and lipid transfer proteins. Research spanning several decades has provided extensive evidence that phosphoinositides are major gatekeepers of membrane organization, with roles in endocytosis, exocytosis, autophagy, lysosome dynamics, vesicular transport and secretion, cilia, inter-organelle membrane contact, endosome maturation and nuclear function. By contrast, there has been remarkably little known about the role of phosphoinositides at mitochondria – an enigmatic and major knowledge gap, with challenges in reliably detecting phosphoinositides at this site.Here we review recent significant breakthroughs in understanding the role of phosphoinositides in regulating mitochondrial dynamics and metabolic function.

Porous N-Doped Carbon Decorated with Atomically Dispersed Independent Dual Metal Sites from Energetic Zeolite Imidazolate Frameworks as Bidirectional Catalysts for Lithium-Sulfur Batteries.

Lithium-sulfur (Li-S) batteries have ultrahigh theoretical specific capacity and energy density, which are considered to be very promising energy storage devices. However, the slow redox kinetics of polysulfides are the main reason for the rapid capacity decay of Li-S batteries. A reasonable electrocatalyst for the Li-S battery should reduce the reaction barrier and accelerate the reaction kinetics of the bidirectional catalytic conversion of lithium polysulfides (LiPSs), thereby reducing the cumulative concentration of LiPSs in the electrolyte. In this report, porous N-doped carbon nanofibers decorated with independent dual metal sites as catalysts for Li-S batteries were fabricated in one step using a fusion-foaming method. Experimental and theoretical analyses demonstrate that the synergistic effect of independent dual metal sites provides strong LiPS affinity, improved electronic conductivity, and enhanced redox kinetics of polysulfides. Therefore, the assembled Li-S battery exhibits high rate performance (discharge specific capacity of 771 mA h g-1 at 2C) and excellent cycle stability (capacity decay rate of 0.51% after 1000 cycles at 1C).

Adipose tissue browning and thermogenesis under physiologically energetic challenges: a remodelled thermogenic system.

Metabolic diseases such as obesity and diabetes are often thought to be caused by reduced energy expenditure, which poses a serious threat to human health. Cold exposure, exercise and caloric restriction have been shown to promote adipose tissue browning and thermogenesis. These physiological interventions increase energy expenditure and thus have emerged as promising strategies for mitigating metabolic disorders. However, that increased adipose tissue browning and thermogenesis elevate thermogenic consumption is not a reasonable explanation when humans and animals confront energetic challenges imposed by these interventions. In this review, we collected numerous results on adipose tissue browning and whitening and evaluated this bi-directional conversion of adipocytes from the perspective of energy homeostasis. Here, we propose a new interpretation of the role of adipose tissue browning under energetic challenges: increased adipose tissue browning and thermogenesis under energy challenge is not to enhance energy expenditure, but to reestablish a more economical thermogenic pattern to maintain the core body temperature. This can be achieved by enhancing the contribution of non-shivering thermogenesis (adipose tissue browning and thermogenesis) and lowering shivering thermogenesis and high intensity shivering. Consequently, the proportion of heat production in fat increases and that in skeletal muscle decreases, enabling skeletal muscle to devote more energy reserves to overcoming environmental stress.

Imparting selective polysulfide conversion via geminal-atom moieties in lithium-sulfur batteries

Electrocatalysis in lithium-sulfur (Li–S) chemistry has readily stimulated extensive interests because of its irreplaceable role in realizing high-performance batteries. In this sense, achieving accelerated catalytic conversion of polysulfides is essential for the shuttle inhibition and kinetics promotion. Nonetheless, selective catalysis of sulfur reduction/evolution reaction via precise control over electrocatalytic mediators is still in its infancy. Moreover, specific catalytic role of the active metal center in dual-atom catalyst sites remains relatively unexplored. Herein, we utilize a salt-confined strategy to fabricate FeCo geminal-atom moieties dispersed on N-doped carbon support (FeCo-NC) for Li–S batteries throughout leveraging Fe and Co single-atom species with selective catalysis. The enhanced bidirectional conversion kinetics of polysulfide with the incorporation of Fe and Co atoms are uncovered throughout theoretical simulation and electrokinetic analysis. As a result, the FeCo-NC endows a rechargeable Li–S battery with excellent capacity retention rate of 98.6% after 100 cycles at 0.2 C and cycling stability with a decay rate of 0.033% per cycle over 2000 cycles at 3.0 C. More encouragingly, the assembled Li–S cell at a sulfur loading of 6.7 mg cm−2 can harvest an areal capacity of 7.13 mAh cm−2, signifying the rational design of geminal-atom mediators to dictate selective catalysis behaviors toward practical Li–S batteries.

Constructing a built-in electron reservoir to dynamically coordinate bidirectional polysulfides conversion for lithium–sulfur batteries with a wide working temperature range

Empowering electrocatalysts with appropriate electrocatalytic activity is imperative to improve the electrochemical properties of lithium–sulfur (Li–S) batteries. Nevertheless, the intricate multi-step conversion pathways of sulfur concomitant with disparate electrokinetic processes make it challenging to establish a tried-and-true strategy to dynamically modulate the electronic structure of electrocatalysts and thus precisely catalyze the specific conversion step. Herein, a built-in electron reservoir is rationally envisaged to refashion the occurrence mechanism of synchronously coordinated electrocatalysis in bidirectional sulfur redox processes. As a proof-of-concept investigation, a facile incorporation of selenium (Se) into lithium polysulfides (LiPSs) is conscripted to recognize the inherent impetus for LiPSs reduction and Li2S decomposition. In conjunction with synchrotron-based characterizations and theoretical calculations, a streamline sulfur redox triggered by Se with a synchro-tuned electronic structure is identified. Specifically, the Se in LiPSs-Se could donate electrons to prompt ample LiPSs reduction in the discharge process, while the Se in the formed Li2S-Se functions as an electron receptor to extract electrons from Li2S for rapid Li2S decomposition in the following charge process. The proposed built-in electron reservoir offers an elegant avenue for dynamically coupling distinct electrokinetics via endogenic electronic structure modulation aiding in circumventing sophisticated interfacial architecture arrangement in contemporary multi-heterogeneous electrocatalysts.

A Low-Phase-Noise RF Up/Down-Converter for Cost-Effective 5G Millimeter-Wave Test Solutions

The increasing demand for millimeter-wave (mmWave) frequencies with wider signal bandwidths, such as 5G NR, requires large investments on test equipment. This work presents a 5G mmWave up/down-converter with a 40 GHz LO, fabricated in custom PCBs with off-the-shelf components. The mmWave converter has broad IF and RF bandwidths of 1∼5 GHz and 21∼45 GHz, and the built-in LO generates 20∼29.5 GHz and 33.5∼40 GHz of output. To achieve high linearity of the converter simultaneously, the LO must produce low-phase-noise and be capable of high harmonics/spur rejection, and design techniques related to these features are demonstrated. Additionally, a reconfigurable IF amplifier for bi-directional conversion is included and demonstrates low gain variation to maintain the linearity of the wideband modulation signals. The final designed converter is tested with 5G OFDM 64-QAM 100 MHz 1-CC (4-CC) signals and shows RF/IF output power of -3/8 dBm with a linear range of 35 (30)/38 (33) dB at an EVM of25 dB.

Bidirectional redox catalyst with rambutan-like structure for advanced lithium-sulfur battery

The lithium polysulfide (LiPSs) shuttle effect and sluggish conversion kinetics hinder the commercial viability of lithium-sulfur (Li-S) batteries. To improve the properties of Li-S batteries, it is imperative to establish efficient pathways for Li-ions transmission by constructing conductivity channels of high quality, and to expedite the conversion kinetics of LiPSs by employing catalysts of exceptional activity. In this study, we synthesized a spherical superstructure of metal–organic framework nanorods (SS-MOFNR) using a self-assembly strategy with zinc-metal–organic framework (Zn-MOF) nanoparticles, followed by carbonization to obtain the spherical superstructure of carbon nanorods (SS-CNR). Subsequently, palladium nanoparticles were synthesized through the reduction and uniformly dispersed onto SS-CNR. The hollow porous structure facilitates the efficient utilization of sulfur and ensures the rapid diffusion of Li-ions. Additionally, Pd nanoparticles exhibit significant catalytic activity, effectively adsorbing LiPSs and bidirectional catalytic conversion of sulfur species, thereby effectively suppressing the shuttle effect of LiPSs. Therefore S/Pd@SS-CNR electrode demonstrates commendable electrochemical efficacy, as evidenced by its initial specific capacity of 1627.7 mAh g−1 at 0.1C and maintaining a specific capacity of 766.2 mAh g−1 even after 600 cycles at 0.5C. Moreover, it exhibits favorable cycle stability at 2C, retaining a reversible capacity of 502.3 mAh g−1 after undergoing 1000 cycles.

Boosting bidirectional conversion of polysulfide driven by the built-in electric field of MoS 2/MoP Mott–Schottky heterostructures in lithium–sulfur batteries

Boosting bidirectional conversion of polysulfide driven by the built-in electric field of MoS ₂/MoP Mott–Schottky heterostructures in lithium–sulfur batteries

A Control Design Technology of Isolated Bidirectional LLC Resonant Converter for Energy Storage System in DC Microgrid Applications

This paper presents a new control method for a bidirectional DC–DC LLC resonant topology converter. The proposed converter can be applied to power the conversion between an energy storage system and a DC bus in a DC microgrid or bidirectional power flow conversion between vehicle-to-grid (V2G) behavior and grid-to-vehicle (G2V) behavior. Furthermore, such a converter can be applied to energy storage systems for decentralized renewable energy generation systems, such as solar and wind power. In addition, this converter can be combined with a bidirectional inverter to allow energy storage in the system to improve the safety, stability, and power quality of the microgrid. In the proposed circuit structure, we use a bidirectional DC–DC LLC, which has the advantages of a higher voltage conversion ratio, lower part count, simpler control than similar converters such as DAB, CLLC, and L–LLC converters, and bidirectional power flow and electrical isolation. Specifically, to extend the battery life, it can be employed as a control strategy for discharging the energy stored in the battery (SOC) and reducing the temperature rise generated by the internal solid electrolyte interphase (SEI) when discharging the battery under the variation in distributed energy resource (DER) generation and load demand. To realize the bidirectional power conversion without using any auxiliary inductor and only changing the control strategy, the forward step-down power conversion was based on pulse frequency modulation (PFM) control, and the reverse step-up power conversion was based on pulse width modulation (PWM) control. In this paper, we introduce the bidirectional converter topology and its control strategy for the DC microgrid battery energy storage system. Finally, a 500 W prototype is built to verify the effectiveness of the proposed converter.

Power transition cycles of reversible solid oxide cells and its impacts on microgrids

Currently, reversible solid oxide cells (rSOC) are the only devices that allows a bidirectional conversion of H2O and H2, being able to operate as fuel cell and as electrolyzer. Thanks to the high-temperature operation, rSOC present a higher efficiency and additionally, provide a feasible solution for long-term energy storage in electrical systems. Experimental testing of rSOC have been mainly focused on cells characterization, thermal or degradation analysis, but the study of transition cycles has not been widely studied. The transitions between the operation as a solid oxide fuel cell (SOFC) and as a solid oxide electrolysis cell (SOEC) might have a significant impact on the rest of the electrical system in which the rSOC is integrated. This article analyzes experimentally the power responses of a rSOC stack, during each operating mode (SOEC-SOFC) and during transition between both modes. The results suggest that transition cycles can be achieved in less than 8 min and the total transition from SOEC rated power to SOFC rated power in less than 10 min, having a significant impact on microgrid operations, especially in islanded mode. The obtained results indicate that the most suitable role for rSOC in a microgrid is as grid-following. The grid-forming role is only possible if the rSOC operates along with a fast-response power source.

Tuning dual-atom mediator toward high-rate bidirectional polysulfide conversion in Li-S batteries

An emerging practice in the realm of Li-S batteries lies in the employment of single-atom catalysts (SACs) as effective mediators to promote polysulfide conversion, but monometallic SACs affording isolated geometric dispersion and sole electronic configuration limit the catalytic benefits and curtail the cell performance. Here, we propose a class of dual-atom catalytic moieties comprising hetero- or homo-atomic pairs anchored on N-doped graphene (NG) to unlock the liquid–solid redox puzzle of sulfur, readily realizing Li-S full cell under high-rate-charging conditions. As for Fe-Ni-NG, in-depth experimental and theoretical analysis reveal that the hetero-atomic orbital coupling leads to altered energy levels, unique electronic structures, and varied Fe oxidation states in comparison with homo-atomic structures (Fe-Fe-NG or Ni-Ni-NG). This would weaken the bonding energy of polysulfide intermediates and thus enable facile electrochemical kinetics to gain rapid liquid-solid Li2S4 ↔ Li2S conversion. Encouragingly, a Li-S battery based on the S@Fe-Ni-NG cathode demonstrates unprecedented fast-charging capability, documenting impressive rate performance (542.7 mA h g−1 at 10.0 C) and favorable cyclic stability (a capacity decay of 0.016% per cycle over 3000 cycles at 10.0 C). This finding offers insights to the rational design and application of dual-atom mediators for Li-S batteries.

Soft matter with magnetically oriented macro - micro structure for improving microwave absorption efficiency

The key challenge for the most widely used magnetic absorbers is how to simultaneously combine low filling with efficient electromagnetic absorption performance. This paper exploited carbonyl iron particles (CIPs) to develop some soft material that possessed orderly orientated structure via applying an external excitation signal, so as to reduce hyperosmotic threshold of conductive loss network, improve impedance matching pattern and thus modulate absorption efficiency. The arch test results showed that effective absorption band (EAB, RL<−10 dB) and reflection loss (RL) efficiency of oriented structure (40 wt%−300mT sample) was much higher than that of unoriented structure (60 wt%−0mT sample), and the reflection loss intensity was reduced to − 15.2 dB, especially EAB was expanded by 8.1 GHz, which significantly alleviated the critical conflict between low filling and electromagnetic loss performance. Also, it was attempted to reveal surface topography changes caused by multiple magnetized particles interaction, and how excitation signal intensity, magnetic particles filling concentration and structural parameters affect microwave absorption efficiency and bi-directional frequency conversion. Thus, a magnetic-manipulated absorbing material proposed laid a theoretical foundation for improving loss efficiency of magnetic materials at low filling concentration.

Multifunctional Catalytic Hierarchical Interfaces of Ni12 P5 -Ni2 P Porous Nanosheets Enabled Both Sulfides Reaction Promotion and Li-Dendrite Suppression for High-Performance Li-S Full Batteries.

The development of lithium-sulfur (Li-S) batteries is very promising and yet faces the issues of hindered polysulfides conversion and Li dendrite growth. Different from using different materials strategies to overcome these two types of problems, here multifunctional catalytic hierarchical interfaces of Ni12 P5 -Ni2 P porous nanosheets formed by Ni2 P partially in situ converted from Ni12 P5 are proposed. The unique electronic structure in the interface endows Ni12 P5 -Ni2 P effective electrocatalysis effect toward both sulfides' reduction and oxidation through reducing Gibbs free energies, indicating a bidirectional conversion acceleration. Importantly, Ni12 P5 -Ni2 P porous nanosheets with hierarchical interfaces also reduced the Li nucleation energy barrier, and a dendrite-free Li deposition is realized during the overall Li deposition and stripping steps. To this end, Ni12 P5 -Ni2 P decorated carbon nanotube/S cathode showing a high capacity of over 1500 mAh g-1 , and a high rate capability of 8 C. Moreover, the coin full cell delivered a high capacity of 1345 mAh g-1 at 0.2 C and the pouch full cell delivered a high capacity of 1114 mAh g-1 at 0.2 C with high electrochemical stability during 180° bending. This work inspires the exploration of hierarchical structures of 2D materials with catalytically active interfaces to improve the electrochemistry of Li-S full battery.

Separator modified by ternary iron molybdenum nitride and nitrogen-doped carbon composite enabling efficient polysulfide conversion for lithium-sulfur batteries

Lithium-sulfur batteries (LSBs) are appealing energy storage systems by virtue of the high theoretical energy density and abundant resources of sulfur. However, the sluggish redox reaction kinetics and shuttle effect of soluble lithium polysulfides (LiPSs) seriously restrict their practical applications. Searching for highly efficient and low cost electrocatalysts towards LiPSs conversion is one of the most promising approaches to relieve the shuttle effect and enhance the sulfur utilization. In this work, we first demonstrate the application of ternary iron molybdenum nitride hybridized with nitrogen-doped carbon, denoted as (Fe0.81Mo0.19)MoN2/NC composite, as an advanced separator modifier to boost the bidirectional catalytic conversion of LiPSs. Impressively, the as-fabricated LSBs with (Fe0.81Mo0.19)MoN2/NC modified separator display an ultrahigh initial discharge capacity of 1366.1 mAh g−1 at 0.1 C and still remains a high value of 809.1 mAh g−1 at a high rate of 4 C. Furthermore, a remarkable discharge capacity of 569.2 mAh g−1 is retained when cycling at a high rate of 1 C for 700 cycles (corresponding to a low attenuation rate of 0.065 % per cycle), indicating the good long-term cycling stability. The excellent performance could be attributed to the multiple advantages of high electrical conductivity, numerous active sites, strong adsorption ability and excellent catalytic activity, thereby effectively suppressing the shuttle effect of LiPSs. The present work indicates that the ternary transition metal nitrides could be promising separator modifiers for high-performance LSBs.

A Simplified Sensorless Synchronous Rectification Method for Inner Phase Shift Control in CLLC Converters

The CLLC converter is a promising topology for bidirectional power conversion applications, such as vehicle-to-grid and battery energy storage systems. In these applications, wide output voltage range is needed. However, traditional pulse frequency modulation method is not suitable for wide output range because of wide switching frequency range. Inner phase shift (IPS) control is a good solution for this issue. In CLLC converters, to further increase the efficiency, synchronous rectification (SR) is required. In this paper, a simplified sensorless SR method is proposed for IPS control. A comprehensive operation mode analysis and an accurate operation mode model is established for IPS control in CLLC converters. With the operation mode model, waveform of secondary side current is simplified. As a result, only a standard quadratic-root formula needs to be calculated to generate SR drive signal, and no extra sensors are needed. The method is low cost and is suitable to implement in embedded systems. A prototype is built to verify the proposed simplified sensorless SR method. The proposed method achieves an obvious efficiency improvement (up to 1.88%) over uncontrolled rectification, and the effect of the proposed method is nearly the same as that of complete SR (maximum efficiency difference is 0.40%).

Time-sharing orbit jump and energy harvesting in nonlinear piezoelectric energy harvesters using a synchronous switch circuit

Nonlinearity has enabled energy harvesting to advance toward higher power output and broader bandwidth in monostable, bistable, and multistable systems. However, operating in the preferable high-energy orbit (HEO) rather than the low-energy orbit (LEO) for making such advancement has restricted their applications. Based on a monostable nonlinear system, this paper proposes a self-contained solution for time-sharing orbit jump and energy harvesting. The joint dynamics of an electromechanical assembly consisting of a nonlinear energy harvester and a switched-mode piezoelectric interface circuit for high-capability energy harvesting is studied. The proposed solution is carried out by utilizing a cutting-edge switched-mode bidirectional energy conversion circuit (BECC), which enables time-sharing dual functions of energy harvesting and vibration exciting. A theoretical model is established based on impedance analysis and multiple time scales method to analyze the stability, frequency response, and phase evolution of the autonomous and nonautonomous nonlinear energy harvesting systems. In particular, the detailed dynamics for the orbit jumps with the vibration exciting mode of BECC are studied. Experiments are performed to validate the full-hysteresis-range orbit jumps with the monostable nonlinear energy harvester. The harvested power after orbit jumps yields a nine-fold increase, compensating for the energy consumption under vibration exciting mode quickly. The proposed solution also refrains the system from extra mechanical or electrical energy sources for orbit jumps, which leads to the first self-contained solution for simultaneous energy harvesting and orbit jump in nonlinear piezoelectric energy harvesting. This work enhances the practical utility of nonlinear energy harvesting technologies toward engineering applications.

Indium/cobalt nanoparticles impregnated porous nitrogen-doped carbon matrix as a 3D sulfur host for lithium polysulfide adsorption-desorption and catalytic conversion in lithium-sulfur batteries

The development of high activity electrocatalysts is considered effective strategy to improve the cathode kinetics in lithium-sulfur batteries (LSBs), especially those operating at high current densities and containing lean electrolytes. Herein, a nanostructured bimetallic sulfur cathode electrocatalyst containing p-block element indium, In/Co-NC, is prepared for the first time. This In-based proof of concept catalyst slows the conversion of elemental sulfur into soluble polysulfides (LiPS) while accelerating their bi-directional liquid-solid conversion, thus reducing their accumulation in the electrolyte and ultimately inhibiting the shuttle effect. LSB cells assembled using the newly prepared electrocatalyst demonstrated high cycle capability of more than 600 cycles at 3 C, accompanied by a high rate capability. Moreover, the In/Co-NC cell containing a lean electrolyte (E/S = 9 μL mgsulfur−1) exhibited 250 stable cycles at 0.5C with only 0.011% capacity decay per cycle. The study provides new design direction for cathode electrocatalysts and guidance for optimization of adsorption and catalytic processes in LSBs.

A Multifaceted Educational Intervention in the Doctor-Patient Relationship for Medical Students to Incorporate Patient Agendas in Simulated Encounters.

From the beginning of their clinical training, medical students demonstrate difficulties when incorporating patient perspectives. This study aimed to assess if students, after an instructional programme, increased their sensitivity towards patients' needs and carried out bidirectional conversations. An observational study involving 109 medical students prior to their clerkships was designed. They attended a five-step training programme designed to encourage the use of communication skills (CSs) to obtain patients' perspectives. The course developed experiential and reflective educational strategies. The students improved their use of CSs throughout three sessions, and the overall score for these patient consultations went up in the opinions of both the external observer (EO) (5; 6.6; 7.5) and the simulated patients SPs (5.3; 6.6; 7.8). Most of the students (83.9%) considered that the CSs addressed were useful for clinical practice, particularly the interviews and the feedback received by the SP and the lecturer. The programme seems to help the students use CSs that facilitate a more bidirectional conversation in a simulated learning environment. It is feasible to integrate these skills into a broader training programme. More research is needed to assess whether the results are applicable to students in real settings and whether they influence additional outcomes.

Spatiotemporal variations in the soil quality of agricultural land and its drivers in China from 1980 to 2018

Soil quality is essential for maintaining the sustainability of agroecosystems, especially under intensified agricultural activities and rapid land use change. The sampling and analysis of soil properties to assess the status of agricultural land is widely practiced at the field scale; however, the spatiotemporal variations in soil quality and its influencing factors at a large scale remain unclear. Here, we quantified spatiotemporal variations in the soil quality of agricultural land in China during 1980–2018 by using the soil quality index (SQI) area approach, and explored the drivers with a geographical detector method. The results showed that the distribution of the SQI in the two periods had a similar spatial trend, except for that in the southwest (SWC), and the SQI decreased from north to south regardless of land use type. The soil quality of woodland was comparatively good with mean SQI values of 1.55 and 1.53 in 1980 and 2018, respectively, followed by that in grassland and cropland. Soil organic carbon, total nitrogen and cation exchange capacity were the dominant soil indicators explaining the spatial heterogeneity of the SQI in all land uses; moreover, climatic factors (i.e., temperature and precipitation) showed a stronger effect on woodland. From 1980 to 2018, the SQI of grassland decreased deeply, especially in the SWC, which showed a severe decline of 12.5 %. The changes in precipitation and temperature were identified as the largest drivers of SQI temporal changes in woodland and grassland, respectively, and their interaction achieved the highest impact across all land uses. In addition, the bidirectional conversion between cropland and grassland in recent decades has aggravated the deterioration of soil quality. Therefore, quantifying spatiotemporal changes in the SQI and elucidating the role of factors influencing soil quality in agroecosystems can provide a guide for designing sustainable agriculture policies and improving environmental quality.

Improvement of Redox Kinetics of Dendrite-Free Lithium–Sulfur Battery by Bidirectional Catalysis of Cationic Dual-Active Sites

The practical application of lithium–sulfur batteries (LSBs) is hampered by the slow lithium polysulfide (LIPS) conversion kinetics and the uncontrollable anode-metal lithium dendrites. Herein, a three-dimensional cation dual-active-site eggshell structure compound (3DCS-FMO@C) was synthesized by soft template, ion exchange, and pyrolysis to modify the commercial separator. Experimental and theoretical analysis results showed that Mn2+ and Fe2+ sites in 3DCS-FMO@C can synergistically adsorb LIPSs, effectively regulate the bidirectional conversion dynamics of intermediate liquid-phase LIPSs and solid-phase lithium sulfide, and reduce the energy barrier of the reaction. The 3DCS-FMO@C-modified separator with high mechanical stability and no reduction in ion diffusion also had a lithiophilic central core that can homogenize the lithium-ion flow, thereby inhibiting the dendrite growth of lithium. Based on the above advantages, 3DCS-FMO@C-modified separator LSBs had better electrochemical performance, including an initial capacity of 1530 mAh g–1 at 0.1C and an ultralow decay rate of 0.029% for 1000 cycles at 0.5C. A high area capacity of 8.7 mAh cm–2 was achieved even with high sulfur loading and poor electrolyte. This work provided a basis for understanding the bidirectional catalysis for practical application in LSBs and simultaneously solved the problem of lithium dendrites.