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SnS 2 @CS, as sulfur host and separator modifier, with high electrical conductivity, high specific surface area and abundant active sites can not only contribute to the fast electron transport to improve the electrochemical activity but also can efficiently adsorb and catalyse polysulfides and improve the utilization of active sulfur. [Display omitted] Lithium-sulfur (Li-S) batteries are considered promising candidates for next-generation advanced energy storage systems due to their high theoretical capacity, low cost and environmental friendliness. However, the severe shuttle effect and weak redox reaction severely restrict the practical application of Li-S batteries. Herein, a functional catalytic material of tin disulfide on porous carbon spheres (SnS 2 @CS) is designed as a sulfur host and separator modifier for lithium-sulfur batteries. SnS 2 @CS with high electrical conductivity, high specific surface area and abundant active sites can not only effectively improve the electrochemical activity but also accelerate the capture/diffusion of polysulfides. Theoretical calculations and in situ Raman also demonstrate that SnS 2 @CS can efficiently adsorb and catalyse the rapid conversion of polysulfides. Based on these advantages, the SnS 2 @CS-based Li-S battery delivers an excellent reversible capacity of 868 mAh/g at 0.5C (capacity retention of 96 %), a high rate capability of 852 mAh/g at 2C, and a durable cycle life with an ultralow capacity decay rate of 0.029 % per cycle over 1000 cycles at 2C. This work combines the design of sulfur electrodes and the modification of separators, which provides an idea for practical applications of Li-S batteries in the future. [ABSTRACT FROM AUTHOR]

Cycling voltage properties and calculation models of L1 and L2. [Display omitted] Li-rich layered oxides are recognized as promising candidates for next-generation Li-ion batteries owing to the high capacity of >250 mAh g−1, but the severe voltage fade has prevented their commercialization. It is widely known that high-voltage charge processes result in layered-to-spinel structural evolution and voltage fade in Li-rich layered oxides. This work emphasizes that limiting the low-voltage reduction can maintain the structure and voltage stability of Li-rich layered oxides after the 4.6 V high-voltage charge processes. A strategy of limiting the low-voltage (<2.8 V) reduction by cycling at 4.6–2.8 V was performed in traditional Li 1.2 Ni 0.13 Mn 0.54 Co 0.13 O 2 and high-Ni Li 1.2 Ni 0.222 Mn 0.504 Co 0.074 O 2. After 300 cycles, traditional Li 1.2 Ni 0.13 Mn 0.54 Co 0.13 O 2 and high-Ni Li 1.2 Ni 0.222 Mn 0.504 Co 0.074 O 2 cycling at 4.6–2 V showed midpoint discharge voltages of 2.83 V and 2.97 V with high voltage fade rates of 2.25 mV/cycle and 2.24 mV/cycle, respectively. While the two materials cycling at 4.6–2.8 V can maintain discharge midpoint voltages of 3.34 V and 3.49 V, with low voltage decay rates of 0.692 mV/cycle and 0.632 mV/cycle, respectively. To better understand the voltage performance, their electric structures were calculated by density functional theory. Physical characterizations were also used to analyze their differences in structural evolution. The results suggested that limiting low-voltage reduction in Li-rich layered oxides is highly necessary for maintaining their structure and voltage stability. [ABSTRACT FROM AUTHOR]

[Display omitted] Highly efficient electrochemical catalysts for oxygen reduction reactions (ORRs) are urgently needed for various energy conversion and storage devices to overcome sluggish ORR kinetics. Here, N,O-codoped carbon spheres with uniform mesopores and a high specific surface area were used as supports for decorating Co 3 O 4 nanoparticles via a facile immersion route. In addition to the benefit of ions and gas mass transfer, the abundant mesopores present in the three-dimensional (3D) carbon spheres also confine and isolate the Co 3 O 4 nanoparticles growing in it, which help to provide rich Co 3 O 4 active sites. The resulting hybrid material exhibits superior ORR activity in terms of even-better half-wave potential and stability than that of commercial Pt/C (40 wt%) in 0.1 M KOH electrolyte. To verify its catalytic activity, the hybrid material was employed as the cathode catalyst in a flexible solid-state zinc-air battery, which achieves a high power density of 227 mW cm−2; this power density is much higher than that of a Pt/C catalytic zinc-air battery (133 mW cm−2) under identical conditions. The improvement in catalytic activity in both aqueous and nonaqueous electrolytes can be attributed to the abundant active sites of the entangled Co 3 O 4 nanoparticles, as well as the novel N,O-codoped carbon structure. [ABSTRACT FROM AUTHOR]

A calcium fluoride composite reduction graphene oxide functional separator for lithium-sulfur batteries to inhibit polysulfide shuttling and mitigate lithium dendrites. [Display omitted] Lithium-sulfur (Li-S) batteries have attracted tremendous attention as promising next-generation energy-storage systems due to their high specific capacity and high specific energy. However, the shuttle of polysulfides and the growth of Li dendrites severely obstruct the practical applications of these batteries. In this work, a functional separator is designed and fabricated in which nano-calcium fluoride (CaF 2) particles are embedded in reduced graphene oxide (rGO) and bladed on a PP separator. The density functional theory (DFT) calculations of the adsorption energy and bond length reveal that CaF 2 has a satisfying adsorption and catalytic effect on polysulfides (Li 2 S n). The factional separator could accelerate homogenous Li+ flow and retard the growth of Li dendrites. In addition, an initial specific capacity of 1504 mAh g−1 at 0.05C is achieved, and it still retains a discharge capacity of 1050 mAh g−1 over 100 cycles at 0.2C. Moreover, the capacity decay rate is only 0.06% per cycle over 420 cycles at a high current density of 0.5 C. The excellent performance could be attributed to the CaF 2 @rGO modified separator not only accelerating the transmission of electrons but also effectively inhibiting the shuttling of polysulfides. This work provides a better method for attaining practical applications of high-performance lithium-sulfur batteries. [ABSTRACT FROM AUTHOR]

We prepared the Cr-doped Li-rich cathodes coated by Li 3 PO 4 with stable capacity and median voltage for lithium-ion batteries. Lithium-rich layered oxides exhibit one of the highest reversible discharge capacities among cathode materials for lithium-ion batteries. However, their voltage decay and poor cycle stability severely restrict their use as a commercial cathode material. In this work, a novel approach of that combines Cr doping and a Li 3 PO 4 coating was designed to address the problems associated with lithium-rich Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 O 2 materials. The synergistic method not only increases the discharge capacity and cycle stability but also decreases the voltage decay. The 1.0 wt% Li 3 PO 4 coating and 0.08 Cr doping on Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 O 2 cathode shows a capacity retention of 76.5% compared to the 59.0% capacity retention for the pristine electrode after 200 cycles. The initial discharge capacity is also increased from 255.8 mAh·g−1 to 265.2 mAh·g−1. In addition, the discharge voltage decay decreases from 0.84 V to 0.39 V after 200 cycles as a result of the Cr doping and Li 3 PO 4 coating. These enhanced electrochemical properties are attributed to the fact that the Cr doping stabilized the layered structure and inhibited its phase transformation to the spinel phase, and the Li 3 PO 4 coating confined the interfacial side reactions between the electrode and electrolyte. This work may provide a new method to solve the subsistent problems of lithium-rich cathode materials. [ABSTRACT FROM AUTHOR]

We prepared nonstoichiometric Li-rich cathodes with stable capacity and median voltage for lithium-ion batteries. • The nonstoichiometry of Li-rich cathodes were firstly synthesized for lithium-ion batteries. • The nonstoichiometric cathodes exhibit stable capacity and median voltage upon cycling. • The improvement of cycling ability attributes to the production of Ni3+ ions in the nonstoichiometric samples. Lithium-rich layered oxides are considered as promising cathode materials for lithium-ion batteries due to its high capacity, but the rapid decay of capacity and operating voltage are great challenges to achieve its commercial application. In this work, the nonstoichiometry of Li-rich layered oxide Li 1.2 Mn 0.6 Ni 0.2 O 2 was designed by directly declining the Mn amounts in the form of Li 1.2 Mn x Ni 0.2 O 2 (x = 0.59, 0.57, 0.55). The nonstoichiometric sample Li 1.2 Mn 0.55 Ni 0.2 O 2 exhibits a capacity of 170.73 mAh g−1 at 0.5 C, a little lower than 187.29 mAh g−1 of Li 1.2 Mn 0.6 Ni 0.2 O 2 , however, better cycling stability of operating voltage and capacity is attained with the reduction of Mn amounts, compared to that of Li 1.2 Mn 0.6 Ni 0.2 O 2. The capacity retention of Li 1.2 Mn 0.55 Ni 0.2 O 2 is enhanced to 88.7% via 74.7% of Li 1.2 Mn 0.6 Ni 0.2 O 2 after 100 cycles at 0.5 C. The declining value of operating voltage for Li 1.2 Mn 0.55 Ni 0.2 O 2 is 0.200 V as compared to 0.559 V for Li 1.2 Mn 0.6 Ni 0.2 O 2. X-ray photoelectron spectra (XPS) was employed to confirm the existence of Ni3+ in the nonstoichiometric samples, and the amounts of Ni3+ increase along the Mn contents decrease. The improvement of electrochemical properties for nonstoichiometric samples is attributed to the presence of Ni3+ due to Ni3+ can defer the transition of layered-to-spinel structure through decreasing the Li/Ni mixing. [ABSTRACT FROM AUTHOR]