Graphite anodes are not stable in most noncarbonate solvents (e.g., ether, sulfoxide, sulfone) upon Li ion intercalation, known as an urgent issue in present Li ions and next-generation Li−S and Li−O 2 batteries for storage of Li ions within the anode for safety features. The solid electrolyte interphase (SEI) is commonly believed to be decisive for stabilizing the graphite anode. However, here we find that the solvation structure of the Li ions, determined by the electrolyte composition including lithium salts, solvents, and additives, plays a more dominant role than SEI in graphite anode stability. The Li ion intercalation desired for battery operation competes with the undesired Li + −solvent co-insertion, leading to graphite exfoliation. The increase in organic lithium salt LiN(SO 2 CF 3 ) 2 concentration or, more effectively, the addition of LiNO 3 lowers the interaction strength between Li + and solvents, suppressing the graphite exfoliation caused by Li + −solvent co-insertion. Our findings refresh the knowledge of the well-known SEI for graphite stability in metal ion batteries and also provide new guidelines for electrolyte systems to achieve reliable and safe Li−S full batteries.

Two-dimensional (2D) transition-metal dichalcogenide (TMDC) semiconductors are important for next-generation electronics and optoelectronics. Given the difficulty in growing large single crystals of 2D TMDC materials, understanding the factors affecting the seed formation and orientation becomes an important issue for controlling the growth. Here, we systematically study the growth of molybdenum disulfide (MoS) monolayer on c-plane sapphire with chemical vapor deposition to discover the factors controlling their orientation. We show that the concentration of precursors, that is, the ratio between sulfur and molybdenum oxide (MoO), plays a key role in the size and orientation of seeds, subsequently controlling the orientation of MoS monolayers. High S/MoO ratio is needed in the early stage of growth to form small seeds that can align easily to the substrate lattice structures, while the ratio should be decreased to enlarge the size of the monolayer at the next stage of the lateral growth. Moreover, we show that the seeds are actually crystalline MoS layers as revealed by high-resolution transmission electron microscopy. There exist two preferred orientations (0° or 60°) registered on sapphire, confirmed by our density functional theory simulation. This report offers a facile technique to grow highly aligned 2D TMDCs and contributes to knowledge advancement in growth mechanism.

The shuttling effect of polysulfides severely hinders the cycle performance and commercialization of Li−S batteries, and significant efforts have been devoted to searching for feasible solutions to mitigate the effect in the past two decades. Recently, metal−organic frameworks (MOFs) with rich porosity, nanometer cavity sizes, and high surface areas have been claimed to be effective in suppressing polysulfide migration. However, the formation of large-scale and grain boundary-free MOFs is still very challenging, where a large number of grain boundaries of MOF particles may also allow the diffusion of polysulfides. Hence, it is still controversial whether the pores in MOFs or the grain boundaries play the critical role. In this study, we perform a comparative study for several commonly used MOFs, and our experimental results and analysis prove that a layer of MOFs on a separator did enhance the capacity stability. Our results suggest that the chemical stability and the aggregation (packing) morphology of MOF particles play more important roles than the internal cavity size in MOFs.

Unlike conventional routes for preparing graphene/polyaniline (G/PANI) composites coupled by van der Waals forces, an approach to graft polyaniline (PANI) nanofibers onto graphene to acquire a polyaniline–graphene (PANI–G) hybrid connected by amide groups is described in this study. The chemical bonding between graphene and PANI is confirmed by infrared spectroscopy and X-ray photoelectron spectroscopy. The Raman spectrum of PANI–G hybrid demonstrates a close interaction between graphene and PANI. Electrochemical tests show that PANI–G hybrid has a high capacitance (623.1 F/g) at a current density of 0.3 A/g, higher than that in G/PANI composites reported previously. In addition, the retained capacitance of the PANI–G hybrid in the long term charge/discharge cycling test reached as high as 510 F/g at a current density of 50 A/g, suggesting its potential use in supercapacitors. First-principle calculations were carried out to study the electronic structures of PANI–G hybrid. The results show that the carbonyl group in the amide linkage plays a key role in the formation of π-conjugated structure, facilitates charge transfer, and consequently improves capacitance and cycling ability.

Rechargeable lithium ion battery (LIB) has dominated the energy market from portable electronics to electric vehicles, but the fast-charging remains challenging. The safety concerns of lithium deposition on graphite anode or the decreased energy density using Li 4 Ti 5 O 12 (LTO) anode are incapable to satisfy applications. Herein, the sulfurized polyacrylonitrile (SPAN) is explored for the first time as a high capacity and safer anode in LIBs, in which the high voltage cathode of LiNi 1/3 Co 1/3 Mn 1/3 O 2 (NCM-H) is further introduced to configure a new SPAN|NCM-H battery with great fast-charging features. The LIB demonstrates a good stability with a high capacity retention of 89.7% after 100 cycles at a high voltage of 3.5 V (i.e., 4.6 V vs Li + /Li). Particularly, the excellent rate capability is confirmed and 78.7% of initial capacity can still be delivered at 4.0C. In addition, 97.6% of the battery capacity can be charged within 2.0C, which is much higher than 80% in current fast-charging application standards. The feature of lithiation potential (>1.0 V vs Li + /Li) of SPAN avoids the lithium deposition and improves the safety, while the high capacity over 640 mAh g −1 promises 43.5% higher energy density than that of LTO-based battery, enabling its great competitiveness to conventional LIBs.even shorter) has attracted considerable attention, [1][2][3][4][5] because the fast charging is one of the most important parameters for electronics and electric vehicles applications. However, the conventional fast charging LIBs using graphite anode always suffers the problem of lithium deposition, which not only shortens the cycle life but also induces the serious safety concerns (e.g., internal short circuit). This is because the potential of graphite can be reduced to the threshold of metallic lithium deposition [6][7][8] due to the large polarization under high charging current, while the deposited lithium is highly active and can react with electrolyte, leading to the death of lithium and increase of internal resistance with a rapid capacity fading. [9] Although the strategies of designing porous graphite etched by KOH [10] or synthesizing composites with conductive matrix (e.g., vaporgrown carbon fibers, [11] carbon nanotube or graphene [12] ) and 3D sponged carbon nanofiber [13] have been explored to enhance the rate capability, the new issues of low initial coulombic efficiency (CE), thick solid electrolyte interphase (SEI) or limited capacity still hinder their practical applications. Fast Charging BatteriesThe ORCID identification number(s) for the author(s) of this article can be found under https://doi.

We demonstrate a novel strategy to enhance sulfur loading and rate performance for Li-S battery by synchronously coupling a nanostructured cathode with an antifouling separator via a facile electrostatic self-assembly approach. The assembly of two dimensional (2D) MXene and positively charged 1D CNT-Polyethyleneimine was observed to controllably address the key issues of sluggish ionic transport, and produce an integrate cathode with dynamic crosslinking network. Moreover, an antifouling separator is proposed by this strategy for the first time, which features well-organized inter-lamellar porosity, dual polarity and high conductivity. The antifouling separator is found to play a pivotal role in: 1) low-order polysulfide activation, 2) high 2 rate cyclability, and 3) Li dendrites inhibition. Our integrated design realizes a long-term capacity of 980 mAh g −1 at 5 mA cm −2 over 500 cycles (sulfur loading: 2.6 mg cm −2 ). Furthermore, a flexible self-assembled cathode with high loading (5.8 mg cm −2 ) and superb mechanical strength (13 MPa), demonstrates an appealing areal capacity of 7.1 mAh cm −2 and rate performance at nearly 10 mA cm −2 .

Conventional intercalated rechargeable batteries have shown their capacity limit, and the development of an alternative battery system with higher capacity is strongly needed for sustainable electrical vehicles and hand-held devices. Herein, we introduce a feasible and scalable multilayer approach to fabricate a promising hybrid lithium battery with superior capacity and multivoltage plateaus. A sulfur-rich electrode (90 wt % S) is covered by a dual layer of graphite/Li4Ti5O12, where the active materials S and Li4Ti5O12 can both take part in redox reactions and thus deliver a high capacity of 572 mAh gcathode(-1) (vs the total mass of electrode) or 1866 mAh gs(-1) (vs the mass of sulfur) at 0.1C (with the definition of 1C = 1675 mA gs(-1)). The battery shows unique voltage platforms at 2.35 and 2.1 V, contributed from S, and 1.55 V from Li4Ti5O12. A high rate capability of 566 mAh gcathode(-1) at 0.25C and 376 mAh gcathode(-1) at 1C with durable cycle ability over 100 cycles can be achieved. Operando Raman and electron microscope analysis confirm that the graphite/Li4Ti5O12 layer slows the dissolution/migration of polysulfides, thereby giving rise to a higher sulfur utilization and a slower capacity decay. This advanced hybrid battery with a multilayer concept for marrying different voltage plateaus from various electrode materials opens a way of providing tunable capacity and multiple voltage platforms for energy device applications.

Surface modification of a cathode (e.g., lithium layered oxide, NCM) has become ever more important in lithium-ion batteries, particularly for pursuing higher energy densities and safety at high voltage. This is because structural degradation of the cathode can be mitigated significantly. Herein, an organic complex is introduced for metal phosphate (e.g., AlPO 4 ) modification through a new film-forming process in nonaqueous solution. This general strategy overcomes the challenge of nonuniform coating in current precipitation methods and then opens a new avenue toward ultrathin surface modification on a molecular scale. As one example, asprepared AlPO 4 -coated NCM exhibits much improved structural and electrochemical stability; meanwhile, thermal runaway can be suppressed significantly in overcharged cells using the modified NCM, demonstrating higher and reliable safety features. The great improvements benefit from the uniform and ultrathin AlPO 4 coating, which inhibits the collapse and conversion of the layered structure to spinel, especially to the rock salt structure at high-voltage conditions, as confirmed by HRTEM and EELS.