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This paper explores the reaction kinetics of NiO supported on YSZ (Yttria Stabilized Zirconia) as an oxygen carrier for chemical looping combustion. Nickel particles with size less than 1 μm mixed with YSZ nano-powders are used to prepare the solid mixture, with 45% mol of NiO. Redox reactivity and oxygen carrying capacity are measured in a laboratory scale fixed bed reactor in the temperature range 500–1000 °C with different concentrations of the reactive gasses. Samples are subjected to repeated redox cycles using synthetic air (O 2 +Ar) for oxidation, and H 2 /H 2 O/Ar mixtures for reduction. NiO/YSZ demonstrates superb cyclic regenerability starting with the 2nd cycle, with full utilization of its oxygen carrying capacity. Compared to pure nickel, pronounced improvement is achieved in the kinetics and oxygen utilization. Full reduction is achieved, and the presence of H 2 O does not affect the reduction rate. Reactivity is also determined as a function of conversion. Global models of redox conversion are developed, in which surface chemistry and solid diffusion are considered. Oxidation exhibits the characteristics of a shrinking-core model with internal reactions at the Ni/NiO interface being the rate limiting step, and it is weakly temperature dependent. Reduction with H 2 generally exhibits surface chemistry limitation (adsorption-desorption), with surface product formation being the rate limiting step. YSZ significantly enhances ionic transport during oxidation and reduction. Reaction rate dependencies on conversion during the two steps suggest an optimal range for the oxygen carrying capacity of the material. [ABSTRACT FROM AUTHOR]

Redistributing the d -orbital of single Fe atom catalysts (SFeACs) has been challenging to optimize redox kinetics of lithium sulfur batteries (LSBs). Here, the Fe-N 4 /S 2 C with mounting energy level of d z 2 and partial occupation of d xz is controllably fabricated. The increased d z 2 , originating from thiophene sulfur, upshifts d band center compared to the Fe-N 4 /C with planar symmetric structure. That promotes electron transfer between Fe-N 4 and sulfur, enhancing conversion of polysulfides and solid products. The lower fill of d xz develops hybridization between Fe and S atoms via the form of bonding and antibonding, with alleviating the loss of sulfur. Thus, the sulfur cathode with Fe-N 4 /S 2 C delivers a high capacity of 749 mAh g−1 at 2.0 C, accompanied by excellent stability with a lower capacity decay of 0.07% per cycle. This work has developed a novel coordination configuration towards SFeACs and uncovered the intrinsic mechanism of facilitated redox kinetics with SFeACs for LSBs. [Display omitted] • A novel configuration (Fe-N 4 S 2) of single Fe atom catalysts (SFeACs) for lithium sulfur batteries was developed. • The increased d z 2 upshifts d band center, promoting the electron transfer between Fe-N 4 and sulfur and redox kinetics. • The lower fill of d xz develops hybridization between Fe and S atoms, with alleviating the loss of active sulfur. • A new insight on the relation among energy level of d -orbital, catalysis of SFeACs and conversion of sulfur was provided. • The sulfur cathode with Fe-N 4 /S 2 C delivers a high capacity of 749 mAh g−1 at 2 C and low-capacity decay of 0.07% per cycle. [ABSTRACT FROM AUTHOR]

Abstract Lithium–sulfur (Li–S) batteries have been regarded as promising candidates for current energy-storage technologies due to their remarkable advantages in energy density and theoretical capacity. However, one of the daunting challenges remained for advanced Li–S systems thus far deals with the synchronous suppression of polysulfide (LiPS) shuttle and acceleration of redox kinetics. Herein, a cooperative interface bridging adsorptive V 2 O 3 and conductive graphene is constructed in-situ by virtue of direct plasma-enhanced chemical vapor deposition (PECVD), resulting in the design of a novel V 2 O 3 -graphene hybrid host to synergize the LiPS entrapment and conversion. The redox kinetics and electrochemical performances of thus-derived cathodes were accordingly enhanced owing to the smooth adsorption-diffusion-conversion of LiPSs even at a sulfur mass loading of 3.7 mg cm–2. Such interfacial engineering offers us a valuable opportunity to gain insight into the comprehensive regulation of LiPS anchoring ability, electrical conductivity and ion diffusive capability in hybrid hosts on suppressing the LiPS shuttle and propelling the redox kinetics. Our devised PECVD route might pave a new route toward the facial and economic design of hetero-phased multi-functional hosts for high-performance Li–S systems. Graphical abstract fx1 Highlights • Graphene-V 2 O 3 hybrid host was designed in-situ based on PECVD route. • Thus-derived cathode showed a low capacity decay of merely 0.046% per cycle at 2 C after 1000 cycles. • Cathodes with a relatively high sulfur mass loading (3.7 mg cm–2) were fabricated. • The smooth adsorption-diffusion-conversion of polysulfides was thoroughly probed via experimental studies and DFT simulations. [ABSTRACT FROM AUTHOR]

Incorporating electrocatalysts into lithium-sulfur (Li-S) batteries is a promising strategy to relieve the deleterious shuttle effect and sluggish conversion kinetics of lithium polysulfides (LiPSs). However, atomic modulation of the electrocatalysts to boost the catalytic activity is still challenging because of their intrinsic structural complexity. Herein, we report the theoretical prediction and experimental realization of Mo single atoms with different ligand coordinations (Mo-N x C 3−x), wherein we find that the LiPSs adsorption and conversion are well modulated by the atomic coordination species of single Mo centers. The resultant Mo-N 2 C 1 displays a moderate bonding strength with LiPSs in comparison with the Mo-N 1 C 2 and Mo-N 3 counterparts, which facilitates the charge transfer kinetics and reduces the Li 2 S precipitation/decomposition energy barrier. Consequently, the constructed Li-S batteries with Mo-N 2 C 1 present a durable cyclability with a low capacity decay rate of 0.055% each cycle over 1000 cycles at a high current rate of 10 C and a decent areal capacity of 4.27 mAh cm−2 after 100 cycles with a low electrolyte/sulfur ratio of 8 µL mg−1. This work demonstrates that optimizing LiPSs adsorption and conversion through local composition and coordination modulation is an effective strategy for developing efficient and durable electrocatalysts for advanced Li-S batteries. [Display omitted] • LiPSs adsorption energy can be effectively modulated through the ligand engineering of single Mo atoms at the atomic level. • Mo-N 2 C 1 presents a mild adsorbability toward LiPSs compared with the counterparts. • Rapid interfacial charge transfer kinetics and LiPSs conversion are achieved for Mo-N 2 C 1. • A high capacity of 732.1 mAh g−1 at 10 C associated with a low capacity decay rate of 0.055% over 1000 cycles is delivered. [ABSTRACT FROM AUTHOR]

The current technology of lithium-sulfur (Li-S) batteries is hindered by the sluggish kinetics and low utilization of sulfur (S) due to its electronic insulating nature. Herein, tellurium (Te) is introduced into S by forming Te x S y solid solutions to reshape Li-S chemistry and facilitate the solid-state conversion of the cathode in carbonate-based electrolytes. Numerical calculations suggest a more delocalized charge-density difference around the Te atoms in Li 16 Te 1 S 7 compared to site-equivalent S atoms in Li 2 S, thus enabling lower energy barriers throughout the Li migration pathway. Mesoporous carbon Ketjenblack (KB) is employed to confine Te x S y materials via a melt diffusion method. By tuning the molar ratio of Te/S, it is found that the Te 1 S 7 /KB cathode delivers the highest reversible capacity of 1306.7 mAh g−1 at 0.1 A g−1 and maintains a capacity of 959.8 mAh g−1 after 400 cycles at 1 A g−1. Kinetics analysis reveals that the introduction of Te accelerates Li-ion diffusion and decreases reaction resistance during the charge/discharge process, thus enabling fast and reversible redox conversion. Moreover, the Te-containing solid electrolyte layer on the electrode surface is generated to prevent the loss of Te 1 S 7 active materials. These encouraging findings suggest that the heteroatomic Te 1 S 7 /KB is a promising cathode to achieve long cycle life and high energy density for Li-S batteries. [Display omitted] • An optimized Te x S y composite cathode is constructed for Li-S batteries. • Theoretical simulations suggest the lowered energy barrier for Li-ion migration in Te 1 S 7. • The Te x S y cathode shows significant enhancement in capacity, stability and kinetics. • A robust SEI is generated to maintain good structural integrity and prevent active materials loss. [ABSTRACT FROM AUTHOR]

Aqueous zinc batteries are among the most promising large-scale energy storage technologies but their practical application is hindered by the low redox reversibility of Zn anode in aqueous electrolytes. In this work, an indium-coated carbon-zinc composite (ICZ) anode is demonstrated with outstanding cyclic stability in classic aqueous zinc sulfate electrolytes. Compared with Zn and the carbon-zinc composite (CZ) anodes, the ICZ anode reduces the high overpotential required for Zn nucleation, and prevents high-rate HER and its related parasitic reactions, endowing high redox reversibility of the ICZ anode. Consequently, the ICZ anode enhances the cyclic stability of zinc ion batteries and zinc ion capacitors. The practical potential of the ICZ anode is demonstrated by an ICZ//porous carbon pouch cell delivering a high areal capacity of 4.7 mAh cm−2 at 6 mA cm−2. Our work provides an effective redox-kinetics regulation strategy for Zn anodes in aqueous zinc batteries. [Display omitted] • An indium-carbon composite coating layer is utilized to boost the reversibility of Zn anode. • Poor cycling stability of Zn foil is elucidated by the GCD curves and microscopy images. • High energy barrier for Zn nucleation triggers high-rate parasitic reactions. • The ICZ anode shows superior effects in suppressing parasitic reactions. • The ICZ pouch cell achieves a high areal capacity of 4.7 mAh cm−2 at 6 mA cm−2. [ABSTRACT FROM AUTHOR]

Nickel-rich layered cathode is a forefront candidate for lithium-ion batteries; however, structural degradation such as intragranular cracking and phase transition in polycrystals focus researchers' attention towards single-crystals. Nevertheless, the sluggish ionic transport and redox kinetics in single-crystals hinder their rate capability and electrochemical performance in harsh conditions. Herein, a synergy of gradient Nb doping on single-crystal LiNi 0.8 Co 0.1 Mn 0.1 O 2 stabilizes the core by strong Nb-O bond and induces Li/Ni antisite migration forming a disordered buffer layer on the surface. The disordered structure maintains the structural integrity by suppressing the phase transition and triggering the Li+ transport. Thus, the modified single-crystal (SNCM@Nb-2) delivers remarkable capacity retention of 92.54% after 100 cycles at 1 C between 2.7 and 4.3 V@ 25 °C (84.26% for SNCM, respectively) and 86.7% at an elevated temperature of 55 °C (SNCM 76.69%). The fast redox kinetics results in remarkably enhanced rate capability and ultra-stable high voltage performance at 4.5 V with SNCM@Nb-2 delivers an initial discharge capacity of 285.2 mAh g−1 with retention of 79.8% (SNCM with 192.1 mAh g−1, 64.1%). The findings of this study provide advancement for the inadequate kinetic properties of single-crystal Ni-rich cathodes under harsh operational conditions. [Display omitted] • Single crystal NCM811 was modified by gradient doping of high-valent Nb5+. • Nb5+ reduces Ni and facilitate Li/Ni antisite defect formation. • Li/Ni antisite migration results in a disordered buffer layer on the surface. • Stronger Nb-O retain surface oxygen, maintaining the structural integrity. [ABSTRACT FROM AUTHOR]

Catalysis is a fundamental solution in suppressing the shuttling of lithium polysulfides (LiPSs), which is essential to the practical applications of lithium-sulfur batteries with high energy density. However, the uncontrollable deposition of electronic and ionic insulative Li 2 S always passivates the catalyst surface for the continuous LiPS conversion. Herein, we propose an effective method to regulate Li 2 S deposition to avoid the catalyst surface passivation by introducing grain boundaries (GBs) in the catalyst. Hollow microspheres composed of MoN-Mo 2 N heterostructure with abundant and highly accessible GBs were prepared as the models. The results show GBs act as the two-dimensional nucleation sites, guiding the fast nucleation and three-dimensional deposition of Li 2 S around them, avoiding the formation of dense Li 2 S coating on their surface. Thus, the high capacity Li 2 S deposition with enhanced conversion kinetics was achieved. The interlayer composed of the above catalyst and carbon nanotube effectively suppresses the shuttling of LiPSs and promotes their fast conversion, leading to a low capacity decay of 0.049% per cycle at 1 C for 800 cycles for the assembled battery. With a higher sulfur loading of 4.7 mg cm−2 under 0.5 C, high capacity retention of 77.2% after 200 cycles could also be achieved. [Display omitted] • The MoN-Mo 2 N catalyst with abundant grain boundaries (GBs) was prepared. • The rich GBs guide the three-dimensional and high capacity Li 2 S deposition. • The Li-S batteries with MoN-Mo 2 N based interlayer show good reversibility and cycling stability. [ABSTRACT FROM AUTHOR]