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The key means to improve the performance of lithium–sulfur batteries (LSBs) is to reduce the internal resistance by building an electronic/ionic pathway and to accelerate the conversion kinetics of lithium polysulfides (LiPSs) through modulation of interface functions. Herein, inspired by a grass root system, a flexible hierarchical CNF‐CNT (carbon nanofiber‐carbon nanotube) membrane decorated with Co‐doped NiS2 nanoparticles (Co‐NiS2@CNF‐CNT) is designed as an interlayer for LSBs, in which the in situ grown CNTs (root hairs) are wound on CNF (roots). Density functional theory (DFT) calculations show that Co doping introduces electron‐deficient regions at the doping sites in NiS2, thus improving chemical adsorption and catalytic activities toward LiPSs. The cell pairs with the Co‐NiS2@CNF‐CNT interlayer exhibit a high rate performance of 951.4 mAh g−1 at 3 C, a reversible capacity of 944.1 mAh g−1 after 500 cycles at 0.2 C, and a prolonged cycle life of 3000 cycles at 5 C. More importantly, an areal capacity of 7.96 mAh cm−2 is achieved with a sulfur loading of 9.6 mg cm−2. This work provides a strategy for enhancing the electrochemical performance of LSBs by combining 3D hierarchical conductive skeletons and electron‐deficient functional adsorption and catalysis materials. [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]

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]

The reasonably regulated Li 2 MnO 3 phase content and Li/Ni disordering are developed to obtain a high-capacity high-Ni low-Co LLO Li 1.167 Ni 0.222 Mn 0.537 Co 0.074 O 2 (L2-1), by two-step adjustment of the Ni/Mn and Li/Mn ratios. Based on the XRD refinement and density functional theory calculation, it is found that a proper Li 2 MnO 3 content (36.6%) and a high Li/Ni disordering (5.93%) in LLOs play a crucial role in achieving high-capacity and high-voltage performance. [Display omitted] • A high-capacity high-Ni Li-rich layered oxide with > 280 mAh g−1 was obtained. • Li 2 MnO 3 content and Li/Ni mixing are controlled to realize the high capacity. • All high-Ni Li-rich layered oxides are designed based on the calculation models. Li-rich layered oxides (LLOs) have been considered as the promising candidate cathodes for the next high-energy Li-based batteries, but suffer from poor rate capability, lower discharge voltage, and persistent voltage fade. Appropriately increasing the Ni content in LLOs tends to improve rate capability, discharge voltage, and stability. However, the high-Ni LLOs are likely to have inferior O2−/− redox activities, causing lower capacities, typically < 250 mAh/g. Herein, the rationally regulated Li 2 MnO 3 phase content and Li/Ni disordering defects via two-step adjustment of the Ni/Mn and Li/Mn ratios are proposed to obtain a high-capacity high-Ni low-Co LLO Li 1.167 Ni 0.222 Mn 0.537 Co 0.074 O 2 (L2-1). Compared to a typical Li 1.2 Ni 0.13 Mn 0.54 Co 0.13 O 2 (Ls), the as-prepared L2-1 cathode delivers higher reversible capacity (267.2 vs 288.2 mAh/g), higher voltage, and better rate capability. Such an improvement is demonstrated by experiments and theoretical calculations that a suitable Li 2 MnO 3 content (36.6%) and a high Li/Ni disordering (5.93%) for LLOs play a crucial role in the O2−/− redox processes. This work contributes to the design of high-capacity high-Ni LLOs. [ABSTRACT FROM AUTHOR]

Lithium-sulfur (Li-S) batteries have attracted enormous attentions as new-generation energy storage devices due to their high theoretical energy density, high theoretical specific capacity, low cost and environmental friendliness. However, polysulfide shuttle and the growth of lithium dendrites significantly restrain the practical application of the Li-S batteries. In this work, a modified PP separator with nanoscale rod-like α-MnO 2 supported on carbon nanotubes was prepared. The α-MnO 2 @CNT modified separator can effectively inhibit the shuttle of polysulfide, enhance the electrochemical activity and accelerate the transfer of ions and electrons. The density functional theory (DFT) calculations demonstrate that α-MnO 2 @CNT can efficiently adsorb and catalyze the conversion of polysulfides. Due to these advantages, the α-MnO 2 @CNT-based Li-S battery delivers a initial discharge capacity of 1469 mAh g−1 at 0.05 C, 1039 mAh g−1 at 0.5 C and the capacity can still maintain 648 mAh g−1 over 500 cycles at 0.5 C (capacity decay rate of 0.075%). Expressly, the capacity decay rate is only 0.022% after 600 cycles at a high current density of 2 C. The excellent performance could be attributed to the α-MnO 2 @CNT modified separator not only accelerating the transmission of electrons but also effectively inhibiting the shuttle of polysulfides. Moreover, this work provides a better idea for practical applications of lithium-sulfur batteries in the future. [Display omitted] • The synthesized α-MnO 2 is in the shape of nanorods. • The α-MnO 2 @CNT composite has good polysulfide adsorption and catalytic conversion ability. • The α-MnO 2 @CNT modified separator shows an excellent long-term cycling stability and rate performance. [ABSTRACT FROM AUTHOR]

[Display omitted] • Honeycomb-like nanoporous carbons with dopants and tunable pore sizes were prepared. • The pore sizes can greatly influence the oxygen reduction activity. • FANC-12 receives a high power density of 174.1 mW cm−2 in a flexible Zn-air battery. • Theory calculation demonstrates that pyridinic N species are the active sites. Metal-free carbon nanomaterials doped with heteroatoms are deemed as promising alternatives to platinum for O 2 reduction in fuel cell and metal-air batteries. To boost the catalytic activity, construction of nanoporous structured carbons with exposed active sites and improved ions/gas mass transport capability is the main research objective. However, controlled preparation of carbon materials with uniform morphology and tunable nanopore sizes is still a great challenge. Herein, a novel furfuryl alcohol-derived, N, O-codoped nanoporous carbon (FANC) with honeycomb-like structure is reported, which possesses high uniformity and controllable pore sizes. Four FANCs with various pore sizes were carefully prepared and their electrocatalytic activity toward oxygen reduction reaction (ORR) were systematically investigated. Among the four FANCs, the one with a pore size of 12 nm (FANC-12) receives the best ORR performance, which is close to that of commercial Pt/C in alkaline electrolyte. A high power density of 174.1 mW cm−2 was obtained with FANC-12 as cathode catalyst in a flexible solid-state zinc-air battery. Calculation by density functional theory reveals the possible structure of this novel N, O-codoped carbon material and also demonstrates that pyridinic N species are the active sites, which is consistent with the experimental result. [ABSTRACT FROM AUTHOR]