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The pursuit of strong endurance and nonflammable performances has promoted demand for solid-state batteries (SSBs). Meanwhile, the reduction of electrolytes' thickness is the key to improving battery performance. However, a large-scale feasible method to fabricate an ultrathin solid electrolyte exhibiting high ionic conductivities is still a challenge. Here, we show a large-scale feasible method to prepare a succinonitrile/polyacrylonitrile(SN/PAN)-coated Li

We report the existence of ferromagnetism in the thiospinel compound CuCo2S4 with Tc ∼ 125 K. The magneto-electronic transport of the CuCo2S4 demonstrates a metallic conductivity and positive magnetoresistance at high temperature. At low temperature, in the ferromagnetic state, there is evidence of spin-transport coupling with magnetic domains giving a region of negative magnetoresistance near the coercive field. The electronic band structure of CuCo2S4 was calculated using density-functional theory (DFT), which shows a ferromagnetic metallic state, in agreement with experiment. With nickel doping, both the spinel CuCo1.5Ni0.5S4 and CuCoNiS4 display paramagnetism down to the lowest measured temperature (3 K). This indicates that, as in other itinerant magnetic sulfides, the exchange interactions are highly sensitive to electron/hole doping. The tunable magnetism in the spinel CuCo2S4, together with its high conductivity, suggests that this thiospinel material could be a candidate for spintronic applications.

Molybdenum carbide (Mo2C) is a promising electrocatalyst for hydrogen evolution reaction (HER) due to the similar electron orbital structure to platinum. Preparing Mo2C catalyst in nanoscale increases the exposure of active catalyst site and significantly enhances electrochemical reaction and improve HER performance. However, Mo2C is not a good electron conductor which still requires a more sufficient contact between the catalyst and electrode to transfer electron current. Here, we proposed in-situ Mo2C growth on carbon nanotubes (CNTs) by using wet impregnation of ammonium molybdate tetrahydrate as Mo source, which established a crystalline transition contact between Mo2C and CNTs and significantly improved HER performance. Our results further showed the optimized HER performance of Mo2C@Camt and achieved a lower Tafel slopes and low onset potential (ηonset) of 46.7 mV dec−1, 51.3 mV dec−1 and 73 mV and 127 mV (vs. RHE) under alkaline and acidic condition, respectively. Furthermore, Mo2C@Camt also shows less attenuation after 1000 times of cyclic voltammograms (CV) cycling stability test and 25 h continuous operation under alkaline and acidic condition.

Vacancy induced electronic structure design is considered as one of the most promising strategies to develop remarkable electrocatalysts for lithium-oxygen battery (LOB) due to its ability to tuning electronic properties and enhancing electronic migration rate. Herein, regulation of electronic structure is realized by introducing oxygen vacancy into SnO2 on Ti3C2Tx MXene (Vo-SnO2/Ti3C2Tx), which acts as physical scaffold to form a stable interface. The fully exposed active sites combining the heterogeneous interface is favorable for optimizing the adsorption capability of Vo-SnO2/Ti3C2Tx for intermediate species and promoting interfacial charge transfer, which will accelerate the kinetics of both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). The high round-trip efficiency (84%), large specific capacity (18648 mA h g−1) and extended cyclability with low overpotential (200 cycles) of the Vo-SnO2/Ti3C2Tx based LOBs experimentally confirm its superior electrocatalytic activity. This study provides a general approach for developing superior electrocatalysts via electronic structure modulation for high performance LOBs.

The commercial application of Li–O2 batteries with ultrahigh energy density hinges on the development of reliable catalysts. Therefore, a well-designed oxygen electrode with superior catalytic acti...

Exploring oxygen electrodes with superior bifunctional catalytic activity and suitable architecture is an effective strategy to improve the performance of lithium-oxygen (Li-O2) batteries. Herein, the internal electronic structure of Ni2P is regulated by heteroatom Co doping to improve its catalytic activity for oxygen redox reactions. Meanwhile, magnetron sputtering N-doped carbon cloth (N-CC) is used as a scaffold to enhance the electrical conductivity. The deliberately designed Co-Ni2P on N-CC (Co-Ni2P@N-CC) with a typical 3D interconnected architecture facilitates the formation of abundant solid-liquid-gas three-phase reaction interfaces inside the architecture. Furthermore, the rational catalyst/substrate interfacial interaction is capable of inducing a solvation-mediated pathway to form toroidal-Li2O2. The results show that the Co-Ni2P@N-CC based Li-O2 battery exhibits an ultra-low overpotential (0.73 V), enhanced rate performance (4487 mA h g-1 at 500 mA g-1) and durability (stable operation over 671 h). The pouch-type battery based on the Co-Ni2P@N-CC flexible electrode runs stably for 581 min in air without obvious voltage attenuation. This work verifies that heterogeneous atom doping and interface interaction can remarkably strengthen the performance of Li-O2 cells and thus pave new avenues towards developing high-performance metal-air batteries.

Catalysts with high performance are urgently needed in order to accelerate the reaction kinetics of the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in lithium–oxygen (Li–O2)...

Gel polymer electrolytes (GPEs) have received extensive attention due to their excellent nonflammability, leak prevention, and low cost. However, low ionic conductivity at room temperature and poor...

In this work, a novel 2D CuCo2S4 (CCS) nanosheets with spinel type structure is fabricated and used as the cathode catalyst for rechargeable Li-O2 battery. The characteristic 2D nanosheets structure with exposure of special (113), (004), and (044) crystal faces provide sufficient active sites for ORR and OER, which promote the rate capability immensely as well as improve discharge capacity and cycle life of the battery. Specifically, Li-O2 batteries with CCS electrodes show excellent cycle stability of more than 176 cycles at limiting capacity 500 mA h g−1 and superior rate performance (2254 mA h g−1 at 2000 mA g−1). For comparison, nanostructures of CuS and Co3S4 have been synthesized employing the similar process used for CCS. When compared to conventional carbon material (Super P) and these two binary metal sulfides, CCS NSs provided the highest catalytic activities at the same mass loading. Which can be attributed to the introduction of copper in the Co3S4 lattice offers the oxygen evolution and kinetics by enhancing Cu2+ sites and also by providing a high-active high-spin stat of octahedral Co3+ for ORR and OER catalysis.

In this work, a novel free-standing CuCo2S4 nanosheet cathode (CuCo2S4@Ni) with high catalytic activity is fabricated for aprotic lithium–oxygen (Li–O2) battery. This deliberately designed oxygen e...

Herein, we report the design and synthesis of a unique honeycomb-like Ni3S2 structure growing directly on the Ni foam skeleton (H-Ni3S2/NF) and its application in lithium-oxygen (Li-O2) batteries as a free-standing cathode. Excellent electrocatalytic activity of honeycomb-like Ni3S2 and the unique network structure of Ni matrix can provide synergistic effect for facilitating electron transport and the diffusion of both oxygen and Li+, leading to the excellent electrochemical performance of Li-O2 battery. Specifically, Li-O2 batteries with H-Ni3S2/NF electrodes exhibit high energy efficiency (84.2%), outstanding cycle stability of over 116 cycles at limiting capacity of 4 mA h cm−2 and excellent rate capability (9.84 mAh cm−2 at 12 mA cm−2).

Exploring oxygen electrodes with superior bifunctional catalytic activity and suitable architecture is an effective strategy to improve the performance of lithium-oxygen (Li-O

The degradation of oxygen electrodes caused by oxygen species in lithium-oxygen (Li-O2) batteries deteriorates their energy efficiency and cyclability and seriously hinders their commercial application. To achieve high energy efficiency and long-term cycle life, gradient-porous ultrathin FeCo2S4 nanosheets on Ni foam (FeCo2S4@Ni) were deliberately designed as a noncarbonaceous freestanding oxygen electrode for Li-O2 batteries. Notably, the gradient-porous structure in FeCo2S4@Ni can offer sufficient active sites as well as mitigate polarization caused by the mass transfer during discharge and charge. The synergistic effect of the two transition metals, Fe2+ and Co3+, optimizes their d-band electronic structure and enhances the intrinsic activity of the oxygen electrode. Benefiting from the above merits, the FeCo2S4@Ni based Li-O2 battery demonstrates greatly increased discharge capacity (8001 mA h g-1), improved rate capability (with a high capacity of 4401 mA h g-1 at 500 mA g-1), and enhanced cycling stability (with a low overpotential of below 1 V after 109 cycles). Our work demonstrates that the battery performance can be improved by regulating the structure and composition of the oxygen electrode and provides a promising strategy for developing high performance Li-O2 batteries.

Catalysts with high performance are urgently needed in order to accelerate the reaction kinetics of the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in lithium-oxygen (Li-O

Lithium-oxygen batteries (LOBs) have been attracting incremental attention beyond conventional Li-ion batteries owing to their superior theoretical energy density (~3500 Wh kg−1). Developing gas diffusion electrodes with high catalytic activity for both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is considered as one of the most promising strategies to promote the practical application of this novel system. Herein, a honeycomb-like Ni2P/Ni12P5 heterostructure with abundant phosphorus vacancies in situ growing on Ni foam (Ni2P/Ni12P5@NF) is developed as an effective and stable electrode for LOBs. Phosphorus vacancies are capable of inducing delocalization of constrained electrons near the Ni-P bonds, thereby regulating the band gap to enhance both the conductivity and the catalytic activity for oxygen electrode reactions. In addition, the modulation of electronic structure along the heterogeneous interface between Ni12P5 and Ni2P optimizes the adsorption of oxygenated intermediates, which is beneficial to accelerate the interface reaction kinetics of oxygen electrode reactions. Impressively, the LOBs with Ni2P/Ni12P5@NF containing abundant phosphorus vacancies exhibit low overpotential of 0.89 V, ultra-high discharge specific capacity of 13254.1 mA h g−1, and remarkable durability of over 500 h. This work concerning engineering heterostructure with rich vacancies can provide new guidance for the development of high performance electrocatalysts.

In this work, a novel free-standing CuCo

The self-supported transition metal phosphide with specific morphology and architecture has been investigated extensively due to excellent conductivity, stability, and morphologic diversity. In the work, cobalt phosphide with special nanoprism arrays in-situ grown on the nickel foam skeleton forms a typical three-dimensional open structure. It exhibits notable electrochemical performance when employed as an anode in a single electrode system, which owns a high mass specific capacitance (1349 F g−1 at the current density of 1 A g−1, which is the highest compared with that in the extant literature), good rate capacity and cycle stability. Besides, pseudocapacitive contribution to the entire capacity is up to about 77%, revealing the nature of high mass specific capacitance of the as-prepared CoP@NF as the working electrode. Furthermore, an asymmetrical supercapacitor device has been fabricated using CoP@NF as an anode and CMK-3@NF as a cathode. It can deliver a high power density of 325 W kg−1 at the energy density of 24 Wh kg−1 and the specific capacitance retention of about 93% after 5000 cycles. The results demonstrate that CoP@NF with special nanoprism arrays is a promising potential candidate as the electrode material of supercapacitors and other energy-storing applications.

Li–O2 batteries (LOBs) with ultrahigh theoretical energy density are regarded as the most promising next-generation candidates for energy storage and conversion devices. However, the development of LOBs is severely hindered by adverse parasitic reactions and sluggish reaction kinetics. Herein, hierarchical Ni3Se2/NiSe2 heterostructure nanoforests on Ni foam (Ni3Se2/NiSe2@NF) is designed as a high efficient bifunctional electrocatalyst for LOBs. As expected, owing to 3D hierarchically branched nanoforests structure, the Ni3Se2/NiSe2@NF electrode can build up an effective channel for mass transfer and expose sufficient active sites for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). In addition, the strong interface interaction between Ni3Se2 and NiSe2 in the heterostructure causes distinct electron redistribution along the interface, which plays a vital role in enhancing electrocatalytic performance of Ni3Se2/NiSe2@NF. Accordingly, LOBs based on Ni3Se2/NiSe2@NF shows a high discharge specific capacity of 23,092 mA h g−1 at 500 mA g−1, a low voltage gap of 0.96 V and an improved cycling life of 500 cycles. It is worth noting that this study has a significant guidance for designing effective bifunctional electrocatalysts via constructing the heterostructure to boost oxygen electrode kinetics and improve Li–O2 battery performance.

Lithium-oxygen (Li–O2) batteries with excellent theoretical energy density (~3500 Wh kg−1) have attracted much attention as next generation energy storage and conversion devices. However, the safety issues caused by the growth of lithium dendrites hinder the commercial application of Li–O2 batteries at the current stage. Here, we propose a novel gel polymer electrolytes (GPE) based on poly (vinylidene fluoride-co-hexafluoropropylene (PVDF-HFP)/poly (ethylene oxide) (PEO)/Ti3C2Tx MXene (refer to as PPM). The weak trapping interactions between ethylene oxide (EO) unit in PEO and anions in lithium salts can solidify anions and promote the dissociation of lithium salts. In addition, the parallel packed two-dimensional Ti3C2Tx MXene nanosheets can effectively guide the uniform nucleation and growth of lithium on the surface of lithium electrode, inhibiting the formation of lithium dendrites during lithium plating. Based on the above advantages, the ionic conductivity and the lithium ion migration amount of the synthetic GPE can reach 5.45 × 10−4 s cm−1 and 0.47, respectively, at room temperature. Base on the above merits, the Li/PVDF-HFP-PEO-5% Ti3C2Tx MXene/Li (Li/PPM-5/Li) symmetric cell can cycle steadily for more than 650 h at a current density of 0.5 mA cm−2. Moreover, PPM-5 based Li–O2 battery can cycle more than 200 cycles at room temperature. This work is of great significance to improve both safety and cycleability of Li–O2 batteries.

In this work, we fabricated a novel free-standing Fe doped CoP nanowire on carbon cloth (Fe–CoP/CC) electrode with high catalytic activity for Li–O2 batteries. It is unexpected that the Li–O2 battery with Fe–CoP/CC electrode demonstrated a low potential of 0.8 V and exceptional cycle stability of more than 500 cycles with no significant voltage attenuation compared with previously reported counterparts. Such excellent performance can be partly attributed to its fine nanowire structure and its large specific surface area (419.14 m2 g−1). Furthermore, iron doping plays a crucial role in improvement of battery performance because the doped Fe can modulate the internal electronic structure and optimize the absorption of intermediate products, which have been proved to be the determinant for optimizing the catalytic activity. Thus, it is believed that heterogeneous element doping in binary or ternary metal compounds is a promising strategy to fabricate high performance oxygen electrode materials for Li–O2 batteries in the next few years.

Compared with the lithium-ion batteries (LIBs), lithium-oxygen batteries (LOBs) demonstrate ultra-high theoretical energy density (≈3505 W h kg−1), which arouse tremendous research interest worldwide. However, the serious challenges facing LOBs are the sluggish oxygen redox kinetics during the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) process, resulting in poor specific capacity and inferior cyclability. Herein, we fabricate phosphorus vacancies enriched Ni2P nanosheets on carbon cloth (denoted as Vp-Ni2P@CC) via a simple NaBH4 reduction strategy as oxygen electrode for high-performance LOBs. Interestingly, the Vp-Ni2P@CC based LOBs exhibit outstanding performance including large specific capacity (10 796 mA h g−1@500 mA g−1) and excellent cyclability (235 cycles@500 mA g−1) compared with LOBs with the Ni2P@CC electrode. It is found that the abundant phosphorus vacancies in the Vp-Ni2P@CC not only act as active sites for oxygen electrode reactions but also enhance the mobility of electron/Li+, simultaneously promoting the improvement of ORR/OER kinetics. Moreover, the restrained electrons around Ni–P bonds are delocalized due to the presence of phosphorus vacancies, which narrow down the band gap in Vp-Ni2P@CC, eventually contributing to high electrical conductivity and excellent electrocatalytic activity. The study provides a new orientation for further developing oxygen electrode catalysts for LOBs.

Solid-state lithium battery is considered as the next generation energy storage device with high security and outstanding energy density. However the low ionic conductivity of the electrolyte seriously limits its practical application. Here, we reported a high-performance flexible gel electrolyte based on graphene oxide (GO) doped poly (vinylidene fluoride-hexafluoro pentaene) cross-linked with poly (ethylene oxide) (PHPG) through weak bond interaction. The polymer electrolyte shows a 3D porous structure with an ionic conductivity of 3.4 × 10−4 S cm−1 at room temperature. Moreover, Li ion transference number is about 0.58, which could greatly accelerate the fast transmission of cations and anions. As a result, the PHPG-based Li symmetrical battery (Li/PHPG/Li) can run stably >750 h at 0.5 mA cm−2, showing good stability and security due to the remarkable suppression of Li dendrite growth. Li O2 batteries assembled with PHPG membrane as electrolyte can operate over 300 cycles at high current density (1 mA cm−2), indicating excellent cycling performance. The excellent performance of PHPG makes PHPG a very promising electrolyte for next-generation solid-state Li O2 batteries.

The development of high-efficiency oxygen electrode with well structural and chemical stability is critical to boost the rapid development of lithium-oxygen (Li-O2) batteries. Which are reckoned as a potent contender for next-generation energy storage devices due to their ultra-high theoretical energy density. Here, a flower-like three-dimensional self-standing ZnCo2S4-based electrode without an addition of binders are fabricated and employing as positive electrode for Li-O2 batteries. The bifunctional catalytic activity of flower-like ZnCo2S4 is conducive to improving the hysteresis kinetics of oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). Representative ultrathin petal edge exposes adequate active sites and provides a sufficient contact interface between Li2O2 and positive electrode, which are essential for reducing the charge overpotential during OER. Compared with the control electrodes, the flower-like ZnCo2S4@Ni-based Li-O2 battery shows decreased overpotential (0.78 V) and improved cycle stability (over 500 cycles).