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Lithium–sulfur (Li–S) batteries have attracted increasing attention for next-generation energy storage systems with a high energy density and low cost. However, the practical applications have been plagued by the sluggish reaction kinetics and the shuttle effect of lithium polysulfides (LiPSs). Herein, core–shell SiO2@Ti3C2Tx MXene (SiO2@MX) hollow spheres are constructed as multifunctional catalysts to boost the performance of Li–S batteries. The dual-polar and dual-physical properties of SiO2 core and MXene shell provide multiple defense lines to the shuttle effect by chemical and physical confinement to LiPSs. Density functional theory calculations prove that Ti3C2Tx MXene and SiO2 enable the stronger trapping ability of LiPSs and the fast Li2S decomposition process. With this strategy, the robust SiO2@MX/S electrodes deliver superior electrochemical performances, including a high capacity of 1263 mAh g−1, and remarkable cycling stability with an ultralow capacity decay of 0.04% per cycle over 1000 cycles at 1 C. This work highlights the significance of core-shell dual-polar structural sulfur catalysts for practical application in advanced Li–S batteries.

Due to larger atom utilization, unique electronic properties and unsaturated coordination, atomically dispersed non-precious metal catalysts with outstanding performances have received great attention in electrocatalysis. Considering the challenge of serious aggregation, rational synthesis of an atomic catalyst with good dispersion of atoms is paramount to the development of these catalysts. Herein, we report an enhanced confinement strategy to synthesize a catalyst comprised of atomically dispersed Fe supported on porous nitrogen-doped graphitic carbon from the novel and more cross-linkable Melamine-Glyoxal Resin. Densified isolated grid trapping, excessive melamine restricting, and nitrogen anchoring are strongly combined to ensure the final atomic-level dispersion of metal atoms. Experimental studies revealed enhanced kinetics of the obtained catalyst towards oxygen reduction reaction (ORR). This catalytic activity originates from the highly active surface with atomically dispersed iron sites as well as the multi-level three-dimensional structure with fast mass and electron transfer. The enhanced confinement strategy endows the resin-derived atomic catalyst with a great prospect to develop for commercialization in future.

Tailoring the architecture is of great significance for developing and designing highly active non-noble metal-based electrocatalysts for hydrogen evolution reaction (HER). Here, the architecture of the precursor was improved by alkali etching after the introduction of Prussian blue analogue (PBA). The coral-like precursor was transformed into bimetallic phosphide via phosphating. Detailed investigation disclares that the introduction of PBA could dramatically improves the electrochemical surface area of the material, and the abundant active site could be obtained via alkali etching. In addition, the removal of amorphous carbon may be the main reason for the enhanced conductivity.

The fragile electrolyte/Li interface is responsible for the long-lasting consumption of Li resources and fast failure of Li metal batteries. The polymer artificial interface with high mechanical flexibility is a promising candidate to maintain the stability of the electrolyte/Li interface; however, sluggish Li-ion transportation of the conventional polymer interface hinders the application. In this work, Li-functionalized graphene oxide (GO-ADP-Li3), which is synthesized by covalent grafting of adenosine 5'-diphosphate lithium on GO nanosheets, is used as a functional additive to improve the Li-ion conductivity of the polymer artificial interface based on PVDF-HFP/LiTFSI. The enhanced Li-ion conductivity is contributed by accelerated Li-ion hopping at the surface between polymer chains and functionalized GO as well as the reduced crystallization degree of PVDF-HFP by this novel additive. The use of this modified polymer as an artificial interface on Li foil enables highly reversible Li stripping/plating and a high capacity retention of 78.4% after 150 cycles for a 0.2 A h Li metal pouch cell (Li/NCM811, strictly following practical conditions). This Li-grafted strategy on GO sheets provides an alternative for designing a compatible electrolyte/Li interface for practical Li metal batteries.

Transition-metal doping and structural improvement are facile and feasible strategies to obtain highly active catalysts for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Herein, we prepare Mo-CoP with a nanosheet structure via hydrothermal reactions and phosphorization. Taking advantage of the nanosheet array, the good electrocatalytic performance of Co-based materials for HER and excellent performance of Co-based phosphide for OER are fully demonstrated. Mo-CoP requires only 112 and 329.9 mV to achieve a current density of 100 mA/cm2 for HER and OER in 1.0 M KOH, respectively. Furthermore, when it was used as bifunctional electrocatalyst, Mo-CoP could deliver 10 mA/cm2 at a low cell voltage of 1.54 V. It was found that the activity of Mo-CoP could be ascribed to the structure of nanosheet and the synergistic role of two different metal phosphides. The most important is that the introduction of Mo improves the activity of the catalyst.

A stable MnO2 nanowires@NiCo-layered double hydroxide (LDH) nanosheet core–shell heterostructure is prepared via a simple liquid-phase reaction method, in which the NiCo-LDH nanosheets grow uniform...

The capability in spatially resolving the interactions between components in lithium (Li)-ion battery cathodes, especially correlating chemistry and electronic structure, is challenging but critical for a better understanding of complex degradation mechanisms for rational developments. X-ray spectro-ptychography and conventional synchrotron-based scanning transmission X-ray microscopy image stacks are the most powerful probes for studying the distribution and chemical state of cations in degraded Li-rich cathodes. Herein, we propose a chemical approach with a spatial resolution of around 5.6 nm to imaging degradation heterogeneities and interplay among components in degraded Li-rich cathodes. Through the chemical imaging reconstruction of the degraded Li-rich cathodes, fluorine (F) ions incorporated into the lattice during charging/discharging processes are proved and strongly correlate with the manganese (Mn) dissolution and oxygen loss within the secondary particles and impact the electronic structure. Otherwise, the electrode-electrolyte interphase component, scattered LiF particles (100-500 nm) along with the MnF2 layer, is also visualized between the primary particles inside the secondary particles of the degraded cathodes. The results provide direct visual evidence for the Li-rich cathode degradation mechanisms and demonstrate that the low-energy ptychography technique offers a superior approach for high-resolution battery material characterization.

Owing to their low cost and high theoretical energy density, lithium-sulfur (Li-S) batteries are highly promising as a contender for the post-lithium-ion battery era. However, the intrinsic low reversible conversion ability of lithium polysulfides to sulfur/Li2S during charging/discharging seriously hinders the sulfur utilization, resulting in poor cycling life of batteries. Herein, we report an improvement of core-shell-structured sulfur nanospheres@ultrathin δ-MnO2 nanosheet electrode materials prepared by a simple precipitation reaction method, in which the ultrathin δ-MnO2 nanosheets as a catalytic layer can promote the chemical adsorption of lithium polysulfides and their conversion rates to sulfur/Li2S. Using a combination of the UV-visible adsorption spectra and first-principles calculation, the results indicate that the Mn-O coordination center on the surface of the MnO2 structure plays an efficient catalytic role in the conversion reaction of lithium polysulfides to insoluble S/Li2S. The sulfur nanospheres@ultrathin δ-MnO2 nanosheet composite with a high S mass ratio of 82 wt % reveals a high specific capacity of 846 mA h g-1 at 1 C rate and good cycling stability. Moreover, the areal capacity of the electrode with a high sulfur loading mass of 10 mg cm-2 is 5.2 mA h cm-2, approaching the practical application standard at a current density of 1 mA cm-2.

A lithium metal anode is regarded as the most promising anode material for the next generation of high-energy density batteries because of its high specific capacity and low reduction potential. Ho...

Lithium transition metal oxide has superior performance for oxygen evolution reaction (OER), while its activity for catalyzing oxygen reduction reaction (ORR) is too low to meet the demand of practical applications. Herein, the NCM-based (NCM, LiNi1/3Co1/3Mn1/3O2) composite materials are prepared through the two steps method. The NCM-2 (Mn2O3/LiNi1/3Co1/3Mn1/3O2) hybrid material demonstrates excellent ORR catalytic property and high OER catalytic performance, as well as the superior stability. Besides, with NCM-2 hybrid materials as catalysts of air cathode, the Al-air battery and Zn-air battery both exhibit higher power density. Therefore, based on results of Brunauer-Emmett-Teller and O2 temperature programmed desorption analysis, the improved catalytic performance ascribed to large specific surface area, pore structure and enhanced oxygen adsorption ability. In this work, the catalytic activity of lithium transition metal oxide has been improved, and a new method was provided to synthesize bifunctional catalysts for metal-air batteries.

High energy density aqueous alkaline-ion batteries have drawn significant attention because of their intrinsic high security and low cost. As suitable anode materials with satisfying capacity and p...

Due to the high energy density and low cost, LiNi1/3Co1/3Mn1/3O2 is wildly explored as a promising cathode material for lithium-ion batteries. However, this material suffers from the destruction of surface structure in the electrolyte and the reacting of electrode with the electrolyte during cycles in highly voltage. Herein, we rationally designed core-shell nanostructure LiNi1/3Mn1/3Co1/3O2@ ultrathin δ-MnO2 nanoflakes cathode material with excellent capacity retention and rate capacity by a liquid-phase precipitation method. The unique ultrathin δ-MnO2 nanoflakes shell nanostructure plays a key role in effectively improving rate performance and cycle life of LiNi1/3Co1/3Mn1/3O2. The electrode with the coating amount of 3 wt% exhibits excellent cycle performance and superior rate capacity compared with bare electrode. The δ-MnO2 nanoflakes-coated layer can react with Li+ during cycling and convert to spinel phase, resulting in a reversibly de/lithiation coating layer to improve its specific capacity compared with other inactive coating layer, and the spinel phase can also provide a three-dimensional lithium ions diffusion channels and thus promote lithium ions diffusion. Judging from the discussion, it can be concluded that the role of δ-MnO2-nanoflakes coating layer not only acts as a protective layer to impede the electrode directly contact with electrolyte but also accelerates lithium ions diffusion and improve its specific capacity.

The application of SiO anodes in Li-ion batteries is greatly restricted by its low initial coulombic efficiency (ICE). Usually, a pre-lithiation procedure is necessary to improve the ICE, but the available technologies are associated with safety issues. Metal (M)-mixed SiO shows great promise to address these issues by reactivating Li2 O through the reaction M+Li2 O→MOx +Li+ , which is the inverse reaction to that occurring at MOx anodes. Sn is found to be a good choice of metal for this concept. Nanoscale Sn-mixed SiO composites are prepared by mechanical milling. Sn forms an outstanding conductive phase, which boosts the reaction kinetics and also reactivates the Li2 O byproduct. Sn/SiO (1:2 w/w) delivers a significant improvement in ICE from 66.5 % to 85.5 %. A higher ICE value of >90 % is obtained when the Sn content is ≥50 wt %. However, additional electrolyte decomposition occurs, which is catalyzed by Sn. In addition, coarsening of the nano-Sn material reduces the inverse conversion reactivity of Sn/Li2 O and subsequently results in rapid capacity fading. The quantitative analysis indicates that, in contrast to transition metals, the alloying and dealloying nature of Sn gives a 50 % improvement in reversible capacity, attributed to Sn/Li2 O. This work gives a general strategy to choose metals for increasing the ICE of SiOx and metal oxides.

Lithium-sulfur (Li-S) batteries display a high theoretical energy density compared with commercial lithium-ion batteries (LIBs). However, there are several major challenges including the poor conductivity and large volumetric expansion of sulfur, and the shuttle effect and uncontrollable deposition of lithium polysulfides, which lead to the low sulfur utilization and poor cycle life in practical applications. The fabrication of state-of-the-art separator based on high electrical conductivity of 3D porous carbon is believed to restrain the shuttle effect of lithium polysulfides and control the deposition of lithium sulfide. Herein, we report a kind of 3D mesporous carbon nanocage (PCN) with a high electrical conductivity as an efficient polysulfide buffer layer on PP separator in Li-S batteries for high sulfur utilization. The extraordinary electrical conductivity of the 3D PCN can promote the transformation reaction of Li2S/sulfur-to-lithium polysulfides between PCN separators and sulfur cathode. During charge/discharge, PCN serves as a buffer layer to redistribute the shuttling back of LiPSs owing to its abundant mesoporous structure. Thereby, Li-S batteries using PCN separator shows an extraordinary initial discharge capacity of 1044 mAh g−1 which still remains 652 mAh g−1 after 200 cycles at 1C. This is a significantly boost for sulfur utilization compared with that in Li-S batteries using PP separator. In addition, the advanced Li-S batteries with PCN separators reveal a superior areal capacity (2.5 mAh cm−2) at a high sulfur loading amount of 7.34 mg cm−2, showing the potential in practical application.

In this work, novel hollow coral-shaped Co3O4 nanostructures are synthesized via a precursor conversion method for the first time, and the detailed process of precursor conversion is revealed. l -ascorbic acid as the structure-directing agent and the origin of oxalate (C2O42−) contributes to the formation of the precursors, providing a low-cost and facile method for preparing Co3O4. Hollow coral-shaped Co3O4 nanostructures are obtained by calcining cobalt oxalate precursors in air. The special Co3O4 nanostructures exhibit noticeable pseudocapacitive properties with a capacitance of 626.5 F g-1 at 5 mV s-1 and show superior stability (capacity retention of 99%) and outstanding Coulombic efficiency (˜100%) within 5000 charge–discharge cycles at 10 A g-1. Furthermore, the asymmetric supercapacitor Co3O4//G fabricated by Co3O4 cathode and graphene hydrogel anode delivers a specific capacitance of 115 F g-1 (47.9 mA h g-1) at 1 A g-1 and attains the maximum energy density of 35.93 Wh kg-1 at the power density of 801.6 W kg-1. The excellent durability of Co3O4//G is demonstrated by the retention of 85.1% of initial capacitance after 5000 cycles at 5 A g-1. The novel and feasible route proposed in the work is expected to be applied prospectively and widely in preparing Co3O4 pseudo-capacitance material, which owns great application value in supercapacitors, as well as in batteries.

Hard carbon has emerged as a candidate for anode material because of its abundant resources and large interlayer spacing for lithium/sodium storage. However, disordered amorphous carbon with low el...

In order to reduce the overpotential of hydrogen evolution reaction (HER), the ternary coating Co-W-P was deposited on the surface of the nickel foam by electrochemical deposition to obtain a highly active electrode. Based on the measured double layer capacitance (Cdl) and HER activity, there is volcanic behavior between the intrinsic activity of Co-W-P and the Co:W ratio in the electrolyte. W and P play different roles in the formation of nanoparticles, and work together to achieve the large electrochemical surface area and excellent activity. When applied to the modification of other catalysts (Ni-P and Fe-P), the higher intrinsic activity was obtained after the introduction of W.

The ultrahigh specific capacity of lithium (Li) metal makes it possible to serve as the ultimate candidate for an anode in high-energy density secondary batteries, whereas the safety hazards caused by Li dendrite growth severely hamper the commercialization process of a lithium metal anode. Here, we propose a 3D conductive skeleton by anchoring MXene on Cu foam (MXene@CF) to significantly improve the electrochemical Li plating/stripping behavior. Li metal tends to nucleate uniformly and grow horizontally along the MXene nanosheets under the strong Coulomb interaction between adsorbed Li and MXene. Moreover, the abundant fluorine termination groups in MXene contribute to forming a stable fluorinated solid electrolyte interphase (SEI) and thus effectively regulating the Li deposition behaviors and prolonging the stability of the Li metal anode. Therefore, the MXene@CF skeleton maintains a high Coulombic efficiency (CE) of 98.5% after 200 cycles at 1 mA cm-2. The MXene@CF-based symmetric cells can run for more than 1000 h without intense voltage fluctuation and demonstrates remarkable deep charge/discharge abilities. The MXene@CF-Li|LiFePO4 full cell exhibits outstanding long-term cycling stability (95% capacity retention after 300 cycles). Our research suggests that MXene could effectively regulate the Li plating behavior that might provide a feasible solution for a dendrite-free Li anode.

Owing to their low cost and high theoretical energy density, lithium-sulfur (Li-S) batteries are highly promising as a contender for the post-lithium-ion battery era. However, the intrinsic low reversible conversion ability of lithium polysulfides to sulfur/Li

Nowadays, it is an urgent need but challenging to develop an efficient and resource-rich electrocatalysts with electrocatalysts activity for the oxygen reduction reaction (ORR) electrocatalyst. Therefore, we rationally designed and synthesized a unique 3-dimensional (3D) structure of flower-like NiFe-layered double hydroxide (NiFe-LDH) growing on graphene oxide (GO) with large surface area, widely-exposed active sites and good electrical conductivity, of which the weight percentage of GO in NiFe-LDH/GO was about 27.37%. Consequently, compared with pure NiFe-LDH (0.71 V (vs RHE), 95 mV dec−1) in alkaline electrolyte, the NiFe-LDH/GO possesses a relatively high onset potential of 0.88 V (vs RHE) and a smaller Tafel slope of 82 mV dec−1. Impressively, the prepared optimized NiFe-LDH/GO presents a highly stability than commercial Pt/C after stability testing due to strong interaction between graphene oxide and LDHs. In view of the above properties, these composite materials have better research prospects and open up a new opportunity for rational design.

Two-dimensional graphene-based materials attract much attention in catalysis due to their high specific surface area and continuous electron transport pathways. However, this material is suffering layer stacking, resulting the masked of most surface active sites, and also being detrimental to mass transfer. Based on the amine-aldehyde resin polymerization method, we constructed a multifactorial synergistic catalyst of nitrogen-doped graphene with surface in situ grown carbon nanotubes (CNTs, Co@NGC). This construction involving two to three-dimensional structural transformation not only avoids layer stacking, but further facilitates the formation of more well-dispersed Co and N species embedded into carbon networks of graphene and CNTs (to form Co N and C N active sites) and increases the accessibility of active sites. After evaluating the test results of comparative experiments, we elucidated the formation process and the activity source of the catalyst. The prepared optimal Co@NGC-800 realized praiseworthy oxygen reduction activity in alkaline media, showing an onset potential of 1.00 V (vs RHE) and a half-wave potential of 0.86 V (vs RHE). Enhanced stability attained comparing with NG (nitrogen doped graphene without the growth of CNTs), the half-wave potential of Co@NGC-800 lost only 8 mV after 40 000 s chronoamperometry.

We report a simple method for the preparation of 3D structure sea urchins Ni-Co layered double hydroxide (NiCo-LDH) with one-step hydrothermal self-assembly. The obtained NiCo-LDH has large specific surface area, porous structure and large interlayer spacing, which causes excellent electrochemical performance. The specific capacitance of the NiCo-LDH electrode, can reach 808.4 C g−1 at the current density of 1 A g−1. Moreover, asymmetric supercapacitors fabricate dusing the negative carbon as positive electrode and NiCo-LDH as activated electrode displays a high energy density of 41.46 Wh/kg at a 212.68 W/kg power density at 1 A g−1.

Co2(OH)3Cl was synthesized by a facile solvothermal method with different solvent ratios of water/glycol (Vwater:Vglycol). The Co2(OH)3Cl prepared at the ratio of 1:2 showed uniform cubic nanostructure and provided the highest specific capacitance of 321.79 F g−1 at 0.5 A g−1. The capacitance retention and the Coulombic efficiency were both kept at 100% without obvious decay after continuous 10,000 charge-discharge cycles, demonstrating the durability and eximious stability of the Co2(OH)3Cl when utilized as the supercapacitor electrode material.