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Employing the solid polymer electrolyte (SPE) instead of traditional liquid electrolyte is an effective way to develop high safety and high-energy density solid-state lithium batteries. Herein, for the first time, the Ni3B2O3 (NBO) nanorods are incorporated into polyethylene oxide (PEO)-based SPE. Particularly, the optimized NBO-embedded SPE shows a high ionic conductivity of 8.5 × 10−5 S cm−1 at 30 °C, lowering the operating temperature of PEO-based SPE substantially. The corresponding LiFePO4/Li battery demonstrates a high discharge capacity of 154 mAh g−1 after 80 cycles at 0.2 C under 30 °C, with favorable capacity retention of 97.5%. The remarkable properties are attributed to the high ionic conductivity of modified SPE at ambient temperature, which is resulted from the decreased crystallinity and melting transition point, increased movement of PEO chain, and promotion of lithium salt dissociation, as well as the formation of the lithium ion migrating pathway on the interface between PEO and NBO nanorods.

Silicon (Si) is widely considered to be the most attractive candidate anode material for use in next-generation high-energy-density lithium (Li)-ion batteries (LIBs) because it has a high theoretical gravimetric Li storage capacity, relatively low lithiation voltage, and abundant resources. Consequently, massive efforts have been exerted to improve its electrochemical performance. While some progress in this field has been achieved, a number of severe challenges, such as the element’s large volume change during cycling, low intrinsic electronic conductivity, and poor rate capacity, have yet to be solved. Methods to solve these problems have been attempted via the development of nanosized Si materials. Unfortunately, reviews summarizing the work on Si-based alloys are scarce. Herein, the recent progress related to Si-based alloy anode materials is reviewed. The problems associated with Si anodes and the corresponding strategies used to address these problems are first described. Then, the available Si-based alloys are divided into Si/Li-active and inactive systems, and the characteristics of these systems are discussed. Other special systems are also introduced. Finally, perspectives and future outlooks are provided to enable the wider application of Si-alloy anodes to commercial LIBs.

For the first time, novel spiral graphene (SGs), which are fabricated by an ultra-facile and robust catalytic graphitization strategy, are reported as a promising negative electrode material for lithium ion capacitors (LICs). The unique spiral graphene features a special helical structure, high graphitization and porous framework, resulting in high plateau capacity (222 mAh g−1 below 0.2 V at 0.05 A g−1) and outstanding rate capability (59 mAh g−1 at 5 A g−1). The formation mechanism of SGs is proposed by understanding the precipitation behaviour of carbon and moving trail of catalyst. The hierarchically porous carbon (HPC) derived from same source is also prepared and shows N, O co-doping property, large surface area of 1878 m2 g−1, high total pore volume of 2.11 cm3 g−1 with 86% of mesopores, making it an ideal capacitive material. More remarkably, by virtue of structural advantages, the optimized SG//HPC LICs with a mass loading of ~2.5 mg cm−2 for positive side deliver a high-energy density of 57 Wh kg−1 at a high-power density of 6323 W kg−1 and long-term cyclic stability (89.1% after 10000 cycles at 5 A g−1) in 2.0~4.2 V, outperforming advanced dual-carbon and non-dual-carbon LICs. The current work advances the design and fabrication of electrode materials for high-performance lithium ion capacitors and other energy storage devices.

The overcharge behaviors of 1000 mAh LiCoO2/graphite pouch cells are systematically investigated through the analysis of morphology, structural and thermal stability of LiCoO2 under different state of charge (SOC) of 120%, 150%, 174%, 190% and 220%. The LiCoO2 experiences the phase transition from O3 to H1-3 and then O1 together with the grain breakage and boundary slip as evidenced by XRD and SEM analysis respectively, which results in the pronounced Co dissolution after the SOC of 174%. The impedance analysis of the pouch cells and coin cells demonstrates that the main contribution of impedance increase originates from the LiCoO2 electrode. Under the combined effect of structural collapse, Co dissolution, and electrolyte oxidization, the thermal stability of LiCoO2 cathode materials reduces with the progressing of overcharge as revealed by differential scanning calorimetry (DSC) results. We hope that this comprehensive understanding can provide meaningful guidance for advancing the overcharge performance of LiCoO2/graphite pouch cells.

High ionic conductivity, good electrochemical stability, and satisfactory mechanical property are the crucial factors for polymer solid state electrolytes. Herein, fast ion conductor LiAlSiO4 (LASO) is incorporated into polyethylene oxide (PEO)-based solid-state electrolytes (SSEs). The SSEs containing LASO exhibit enhanced mechanical properties performance compared to pristine PEO-LiTFSI electrolyte. A reduced melting transition temperature of 40.57 °C is enabled by introducing LASO in to PEO-based SSE, which is beneficial to the motion of PEO chain and makes it possible for working at a moderate environment. Coupling with the enhanced motion of PEO, dissociation of the lithium salt, and conducting channel of LASO, the optimized composite polymer SSE exhibits a high ionic conductivity of 4.68 × 10−4, 3.16 × 10−4 and 1.62 × 10−4 S cm−1 at 60, 50 and 40 °C, respectively. The corresponding LiFePO4//Li solid-state battery exhibits high specific capacities of 166, 160 and 139 mAh g−1 at 0.2 C under 60, 40 and 25 °C. In addition, it remains 130 mAh g−1 at 4.0 C, and maintains 91.74% after 500 cycles at 1.0 C under 60 °C. This study provides a simple approach for developing ionic conductor-filled polymer electrolytes in solid-state lithium battery application.

The sodium-ion battery is a strong candidate for the large-scale energy storage device due to its low cost and abundant resources. However, the severe self-discharge issue, which is rooted in the dissolution of the solid-electrolyte interphase (SEI) film in the sodium-ion battery, impedes its practical application. Thus, the central question is how to build a stable SEI film onto the electrode surface. Here, we propose and experimentally demonstrate a LiF-rich SEI film at the surface of hard carbon (HC) anode in sodium-ion battery, which is generated by adding lithium difluoro(oxalate)borate (LiODFB) additive into the electrolyte of 1 M NaPF6 in EC:DMC (1:1 in volume ratio). The X-ray photoelectron spectroscopy (XPS) and electron microscopy (SEM and TEM) results confirm that we obtain the LiF-rich SEI film at the HC electrode surface, which grows up with the increasing of the concentration of added LiODFB additive. But it blocks the transmission of Na ions into HC as evidenced by the initial galvanostatic charge/discharge, cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS) results. Although this work shows a negative result, it denies the possibility of using the lithium compounds with lower solubility as SEI components for Na-ion battery since it allows to transfer the lithium ions rather than the Na ions.

Graphitic carbons with reasonable pore volume and appropriate graphitization degree can provide efficient Li+/electrolyte-transfer channels and ameliorate the sluggish dynamic behavior of battery-type carbon negative electrode in lithium-ion capacitors (LICs). In this work, onion-like graphitic carbon materials are obtained by using carbon quantum dots as precursors after sintering, and the effects of alkali metal salts on the structure, morphology and performance of the samples are focused. The results show that alkali metal salts as activator can etch graphitic carbons, and the specific surface area and pore size distribution are intimately related to the description of the alkali metal salt. Moreover, it also affects the graphitization degree of the materials. The porous graphitic carbons (S-GCs) obtained by NaCl activation exhibit high specific surface area (77.14 m2·g−1) and appropriate graphitization degree. It is expectable that the electrochemical performance for lithium-ions storage can be largely promoted by the smart combination of catalytic graphitization and pores-creating strategy. High-performance LICs (S-GCs//AC LICs) are achieved with high energy density of 92 Wh·kg−1 and superior rate capability (66.3 Wh·kg−1 at 10 A·g−1) together with the power density as high as 10020.2 W·kg−1.

With the proliferation of energy storage and power applications, electric vehicles particularly, solid-state batteries are considered as one of the most promising strategies to address the ever-increasing safety concern and high energy demand of power devices. Here, we demonstrate the Al4B2O9 nanorods-modified poly(ethylene oxide) (PEO)-based solid polymer electrolyte (ASPE) with high ionic conductivity, wide electrochemical window, decent mechanical property and nonflammable performance. Specifically, because of the longer-range ordered Li+ transfer channels conducted by the interaction between Al4B2O9 nanorods and PEO, the optimal ASPE (ASPE-1) shows excellent ionic conductivity of 4.35×10−1 and 3.1×10−1 S cm−1 at 30 and 60°C, respectively. It also has good electrochemical stability at 60°C with a decomposition voltage of 5.1 V. Besides, the assembled LiFePO4//Li cells show good cycling performance, delivering 155 mA h g−1 after 300 cycles at 1 C under 60°C, and present excellent low temperature adaptability, retaining over 125 mA h g−1 after 90 cycles at 0.2 C under 30°C. These results verify that the addition of Al4B2O9 nanorods can effectively promote the integrated performance of solid polymer electrolyte.

Lithium ion capacitors (LICs) have been widely used as energy storage devices due to their high energy density and high power density. For LICs, pre-lithiation of negative electrode is necessary. In this work, we employ a bifunctional Li6CoO4 (LCO) as cathodic pre-lithiation reagent to improve the electrochemical performance of LICs. The synthesized LCO exhibited high first charge specific capacity of 721 mAh g−1 and extremely low initial coulombic efficiency of 3.19%, providing sufficient Li+ for the pre-lithiation of negative electrode in the first charge. Simultaneously, Li6–xCoOy is generated from LCO during the first charge process, which exhibits pseudocapacitive property and contributes to capacity in form of surface capacitance during subsequent cycles, increasing the capacity of capacitive positive electrode. With the appropriate amounts of addition to the positive side in LICs, this bifunctional prelithiation reagent LCO shows significantly improved the electrochemical performance with the energy density of 78.5 Wh kg−1 after 300 cycles between 2.0 and 4.2 V at 250 mA g−1.

Lithium-ion capacitor (LIC) bridging the gap between the lithium ion battery and electrochemical capacitor has attracted myriad interest. Lignin, the second most abundant natural polymer, is also t...

Porous graphitic carbon nanorings (PGCNs) are proposed by smart catalytic graphitization of nano-sized graphene quantum dots (GQDs). The as-prepared PGCNs show unique ring-like morphology with diameter around 10 nm, and demonstrate extraordinary mesoporous structure, controllable graphitization degree and highly defective nature. The mechanism from GQDs to PGCNs is proven to be a dissolution-precipitation process, undergoing the procedure of amorphous carbon, intermediate phase, graphitic carbon nanorings and graphitic carbon nanosheets. Further, the relationship between particles size of GQDs precursor and graphitization degree of PGCNs products is revealed. The unique microstructure implies PGCNs a broad prospect for energy storage application. When applied as negative electrode materials in dual-carbon lithium-ion capacitors, high energy density (77.6 Wh·kg−1) and super long lifespan (89.5% retention after 40,000 cycles at 5.0 A·g−1) are obtained. The energy density still maintains at 24.5 Wh·kg−1 even at the power density of 14.1 kW·kg−1, demonstrating excellent rate capability. The distinct microstructure of PGCNs together with the strategy for catalytic conversion from nanocarbon precursors to carbon nanorings opens a new window for carbon materials in electrochemical energy storage.

Cost-effective bifunctional electrocatalysts with desirable oxygen catalytic activity to both of ORR and OER are essential to the large-scale commercial application of metal-air batteries. In this work, a robust hydrothermal assembly strategy is presented to fabricate the three-dimensional (3D) urchin-like hybrid material of acid-treated multiwall CNTs (MWCNTs) and needle-like NiCo2O4 as a cost-effective bifunctional oxygen electrocatalyst. Benefiting from the particular 3D urchin-like mesoporous structure providing rich transport channels for O2 diffusion and electrolyte infiltration and abundant active sites for charge transfer reaction, and the synergistic effect of high electrocatalytically active NiCo2O4 and high conductive MWCNTs network, the optimized NCO@20%MWCNTs composite exhibits a superior OER and ORR catalytic activity. In its practical application, an ultrahigh initial round-trip efficiency of 79.4% and long-term cycle stability (950 cycles) at 10 mA cm−2 are achieved in Zn-air battery. This simple strategy for construction of the cost-effective unique 3D porous urchin-like structure together with the improved electrochemical catalytic activity provides a great potential for material design in oxygen catalysis and metal-air batteries.

Herein, we report a series of O3-type Na(Ni1/3Mn1/3Fe1/3)1-xAlxO2 (x = 0, 0.03, 0.05, 0.07) oxides as sodium-ion battery cathode materials synthesized via spray pyrolysis method. The structure, morphology, and electrochemical performance of Na(Ni1/3Mn1/3Fe1/3)1-xAlxO2 (x = 0, 0.03, 0.05, 0.07) are characterized by XRD, SEM, CV, and galvanostatic charge and discharge tests, respectively. Na(Ni1/3Mn1/3Fe1/3)0.95Al0.05O2 delivers an initial discharge capacity of 145.4 mAh g−1 at 0.1 C and exhibits a favorable reversible capacity about 128.4 mAh g−1 after 80 cycles at 0.2 C, with the capacity retention of 77.5% at the voltage range of 2.0 to 4.2 V. XPS analysis reveals that Al-doping could alleviate the Jahn-Teller effect caused by Mn3+ and enhance the structural stability of layered oxides. The results confirm that a small quantity of (5 at. %) Al-doping improves the structural stability of the material, therefore leading to the excellent electrochemical performance.

2D carbon materials show extraordinarily promising prospects in energy storage systems. To improve the performance of lithium-ion capacitors (LICs), it is urgently necessary for addressing the sluggish kinetics behavior of battery-type carbon negative electrode. Herein, novel 2D defective high-graphitic carbon nanosheets (GNS), which is derived from in-situ catalytic graphitization of 1D nanorods precursor, are presented and employed as negative electrode materials in LICs. The effects of defects contained in the as-prepared samples are further explored by the First-principle calculations, revealing that carbonylation and N-doping (particularly pyridine N) manifest synergistic effect on improving the electronic conductivity and regulating the microstructure. The high reversible capacity accompanied with large plateau capacity and superior rate capability in the half-cell test implies that GNS can be a promised candidate as negative electrode for LICs. Excitingly, the fabricated LICs exhibit high energy density of 112 Wh kg−1 and excellent power density of 19,600 W kg−1, together with outstanding energy density retention of 96.5% after 5000 cycles at 5 A g−1. The defects-controlled in-situ catalytic strategy for preparing GNS may provide a brand-new way for materials design for energy storage.

A simple CePO4 modification method on Li1.2Mn0.54Ni0.13Co0.13O2 is introduced. A series of CePO4-coated Li1.2Mn0.54Ni0.13Co0.13O2 materials accompanying with PO43− anion doping were successfully synthesized via a simple wet method. XRD, SEM, HR-TEM, FE-EPMA, XPS, and electrochemical measurements were used to characterize the pristine and modified materials. The results exhibit that CePO4@ Li1.2Mn0.54Ni0.13Co0.13O2 samples showed improved structural stabilities and cyclic properties. It is because that CePO4 coating film could effectively prevent Li-rich materials from the corrosion of HF during the cycle process and restrict the side reactions over electrolyte and electrode. Also, when doping with PO43− anions, the layered structure was enhanced due to the strong bonding of PO43− anions, compared with M–O bonds (M = Ni, Mn, Co). Particularly, 3 wt.% CePO4-modified material exhibits the excellent cyclic retention of 86.9% at 100 mA g−1 with the 100th discharge capacity of 210.7 mAh g−1, while pristine sample exhibits a poorer cyclic retention of 76.1%. To further investigate the modification information, the distributions of elements Mn, Ni, Co, Ce, P, and O in cross section for CePO4-modified material were obtained via FE-EPMA test.

Heterostructured materials composed of nickel and cobalt hydroxides exhibit impressive prospect in aqueous-based supercapacitors owing to their unique layered frameworks. Herein, a series of Co(OH)2-Ni(OH)2 heterostructures are prepared on nickel foam as binder-free electrodes (denoted as NCN-x) via a simple two-step electrodeposition method, where Co(OH)2 serves as the interlayer and Ni(OH)2 serves as the out layer. By tuning the deposition charge quantities of these two kinds of hydroxides, different electrode architectures with various mass ratios of α-Ni(OH)2 to β-Co(OH)2 are obtained. Among these electrodes, the smartly tailored NCN-3 electrode representing 1.0 C and 0.75 C deposition charges separately for Co(OH)2 and Ni(OH)2 exhibits particular core-shell nanosheet-like microstructure, possessing large surface area and short ion/electron transportation pathways. As a result, it delivers good cycling performance of ∼75.8% capacitance retention after 1000 cycles at 5 A g−1. Moreover, the hybrid capacitor consists of NCN-3 cathode and AC anode realizes high energy and power densities (32.6 Wh kg−1 at 465.7 W kg−1 and 25.5 Wh kg−1 at 7061.5 W kg−1). This work can serve as a guide for designing other heterostructured electrodes by electrochemical method.

α-MoO3 coated Li[Li0.2Mn0.54Ni0.13Co0.13]O2 electrode materials were obtained via a simple and effective wet chemical method. The results of X-ray diffraction (XRD), high-resolution transmission electron microscope (HR-TEM) and X-ray photoelectron spectroscopy (XPS) indicated that α-MoO3 had been successfully coated on the surface of pristine materials. Charge-discharge measurements demonstrated that the α-MoO3 thin layer could enhance the electrochemical performances. The initial coulombic efficiency improved from 75.7% to 89.6%, and the modified sample exhibited good cyclic performance of 87.0% at 100 mA g−1 after 100 cycles and 85.3% at 200 mA g−1 after 100 cycles with the excellent discharge properties. According to the analysis of electrochemical impedance spectroscopy (EIS) and cyclic voltammogram (CV), the largely enhanced electrochemical performance are mainly due to the restrain of the side reactions between electrode and electrolyte and the increased migration rate of Li+ between the electrode/electrolyte interface by α-MoO3 film.

The γ-WO3/Li2WO4 composite coated and spinel-embedded Li[Li0.2Mn0.54Ni0.13Co0.13]O2 cathode is successfully synthesized via a simple wet coating process. A series of synthesized materials were characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), high-resolution transmission electron microscope (HR-TEM), Raman and X-ray photoelectron spectroscopy (XPS). γ-WO3/Li2WO4 composite layer was successfully coated on the surface of Li-rich Mn-based materials and the spinel structure was also formed during the modification process. Charge-discharge measurements indicate that the modified samples show an enhanced cyclic properties and rate capability. After the modification process, the initial coulombic efficiency increased to 89.3% for 7 wt % W-composite coated sample with the lowest capacity loss of 33.5 mAh g−1. Particularly, 5 wt % W-composite coated sample shows the best capacity retention of 88.0% at 100 mA g−1 with the discharge capacity of 233.5 mAh g−1 and excellent rate capability with the discharge capacity of 173.0 mAh g−1 at 800 mA g−1. The improvements in electrochemical properties and structural stability were mainly due to both γ-WO3/Li2WO4 coating layer and the spinel phase formed during the modification.

In this paper, we demonstrate for the first time the synthesis of spinel LiMn2O4 using by-products of the electrolytic manganese through solid state reaction. LiMn2O4 synthesized through by-products from coated titanium anodes exhibits a special biscuit-like hierarchical micro/nano structure and excellent electrochemical performance. When used as cathode material in lithium ion batteries, it delivers an initial discharge capacity of 119.1 mA h g−1 at 14.8 mA g−1, and high reversible discharge capacities of 94.1 mA h g−1 and 75.4 mA h g−1 can be maintained when the current density reach 740 and 1480 mA g−1. High capacity retention of about 90% can be also achieved after 200 cycles in the potential range of 3–4.3 V at 148 mA g−1. The electrochemical performance is much superior to that of the counterpart sample synthesized by conventional electrolytic manganese dioxide which can be ascribed to the unique hierarchical micro/nano architecture. However, on the other side, LiMn2O4 synthesized by Pb anode slime suffer from poor electrochemical performance due to the inevitable Pb issue and other relevant impurities. These results may open up a new gate for the further application of by-product of electrolytic manganese.

A nanoscale spinel pillaring layer is introduced onto the surface of the LiNi0.8Co0.1Mn0.1O2 cathode material, which is confirmed by combined surface-probing techniques. The functional layer does not change the crystal structure after of pristine LiNi0.8Co0.1Mn0.1O2, while it plays a vital role in avoiding unfavorable side reactions occurred in the interphase between cathode materials and electrolyte. The treated sample shows suppressed capacity decay (19.3%) as compared to the pristine sample (41.9%) after 200 cycles at 2 C rate. Moreover, it can also improve the storage performance of LiNi0.8Co0.1Mn0.1O2 by restraining the generation of Li2CO3 and the NiO-like phase during the storage process in humid air. Thus, the capacity retention capability is improved after storage in air for 2 months, which improves from 52.2% to 77.6% after 200 cycles. Overall, this study offers an effective solution to improve the cyclability and storage stability of the Ni-based cathode materials.

To solve the problem of poor conductivity, monoclinic NaVPO4F with a uniform carbon coating layer is synthesized via a facile solution approach with assistance of polyvinyl pyrrolidone (PVP). On one hand, PVP acts as a surfactant, encapsulating the precursor and restraining the particle growth. On the other hand, PVP is used as carbon source, in-situ generating a uniform carbon coating layer on the surface of NaVPO4F particles. The obtained NaVPO4F/C composite shows much enhanced electronic conductivity of 4.2 × 10−2 S cm−1. As a result, the synthesized NaVPO4F/C cathode for sodium ion batteries demonstrates superior cyclic stability and rate capability, delivering a reversible capacity of 111 mAh g−1 at 0.1 C, maintaining 81.8% capacity retention after 1000 cycles at 10 C and retaining a high capacity of 68 mAh g−1 at 20 C.

Infinite volume expansion and high reactivity severely hinder the commercial applications of lithium metal batteries. Moreover, the short circuit caused by Li dendrites is fatal for the long-term performance of lithium metal batteries and may cause safety problems. Herein, lithiophilic silver/lithium (Ag/Li) composite anodes are synthesized via a spontaneous displacement reaction between silver nitrate and Li foil at room temperature, which can settle the above challenges by regulating Li nucleation and homogenizing Li-ion flux. Benefiting from the lithiophilic design, Li ion realizes zero nucleation overpotential on the as-obtained Ag/Li anodes with abundant spherical silver nanoparticles. Additionally, the by-product, lithium nitrate, acts as an electrolyte additive, which further ensures uniform Li deposition. Consequently, Ag/Li symmetric cells demonstrate ultralong lifespan with repeated plating/stripping for 1000 cycles at the current densities of 1 mA cm−2 and 5 mA cm−2, with negligible voltage fluctuations. Furthermore, the full-cell devices, paired with LiFePO4, also exhibit excellent electrochemical performance. The facile and effective strategy provides a promising prospect for commercial applications of lithium metal batteries.

By reducing the gap between lithium-ion batteries (LIBs) and supercapacitors (SCs) effectively, lithium-ion capacitors (LICs) have attracted tremendous attention among various electrochemical energy storage systems because they exhibit a high energy density (inherited from the LIBs), a high power output, long lifespan (owing to the SCs) and favorable chemical stability. Carbonaceous electrode materials play significant roles in high performance dual-carbon LICs whether positive or negative. Here, the working mechanism, cell design principle and recent progress in carbon-based electrode materials for dual-carbon LICs are illustrated. Then, the commercialization of LICs is discussed briefly. Finally, some suggestions for the future developments associated with dual-carbon LICs are proposed.

Tin oxides as some of the potential candidates for commercial graphite anodes suffer from serious drawbacks such as poor electronic conductivity and large volume variation during cycling. Dispersing nanostructured SnOx into a carbon matrix may be an effective strategy to solve these problems. In this work, a novel dried plum-like yolk–shell SnOx/C architecture with high specific surface area and superior structural stability is constructed by an extremely facile and scalable spray pyrolysis method in ten seconds. The SnOx nanodots (

Fabricating three dimensional (3D) free-standing electrode is considerable attractive in designing supercapacitors of high energy and power densities. Co(OH)2@Ni(OH)2 core-shell nanosheets have been successfully grown on nickel foam (NF) as 3D free-standing electrode (denoted as NCN) for electrochemical capacitors via a facile stepwise electrodeposition process. It is found that the unique 3D free-standing frameworks combined with the core-shell nanosheet-like heterostructure endow the as-prepared electrode good electrochemical performances. When tested as a supercapacitor electrode, it delivers a capacitance of 1520.6 F g−1 at 1 A g−1 and still keeps 1376.6 F g−1 at 10 A g−1, exhibiting excellent rate performance. Moreover, it retains ∼71.4% initial capacitance after 1500 charging/discharging cycles at 5 A g−1, demonstrating good cycling stability. The good electrochemical performance of the NCN electrode makes it a promising electrode candidate for high performance supercapacitors.

Summary Low-cost, scalable energy storage is the key to continuing growth of renewable energy technologies. Here a battery with sedimentary slurry electrode (SSE) is proposed. Through the conversion of discrete particles between sedimentary and suspending types, it not only inherits the advantages of semi-solid flow cell but also exhibits high energy density and stable conductive network. Given an example, the zinc SSE (ZSSE) delivers a large discharge capacity of 479.2 mAh g−1 at 10 mA cm−2. More importantly, by renewal of the slurry per 20 cycles, it can run for 112 and 75 cycles before falling below 80% of designed capacity under 10 mA cm−2 (20% DODZn) and 25 mA cm−2 (25% DODZn), respectively. The lost capacity after cycles is able to recover after slurry renewal and the end-of-life SSE can be easily reused by re-formation. The concept of SSE brands a new way for electrochemical energy storage., Graphical Abstract, Highlights • A renewable semi-solid sedimentary slurry battery is proposed • Lost capacity after cycles is able to recover after slurry renewal • End-of-life SSE can be easily reused by re-formation, Energy Materials; Energy Storage; Energy Systems; Materials Characterization

The practical application of O3-type layered oxides cathode materials for sodium ion batteries (SIBs) is hindered by two major difficulties, including capacity decay rooted in multiphase transitions and storage issue originated from sensitivity to moisture. Herein, we report a series of O3-type layered oxides Na(Ni0.4Cu0.1Mn0.4Ti0.1)1-xLaxO2 (x = 0, 0.001, 0.003, 0.005, termed as NMCT, NMCT-Lax, respectively) cathode materials synthesized via spray pyrolysis followed by high-temperature sintering method, which manifest enhanced electrochemical performance and air stability as compared to the NaNi0.5Mn0.5O2 (termed as NM) material. Optimum performance is achieved in the NMCT-La0.001 material that delivers a high initial discharge capacity of 170.1 mAh g−1 in the voltage range of 2.0–4.4 V at 0.1C (1C = 150 mA g−1). NMCT-La0.001 exhibits a highly reversible structural transformation during charging/discharging as demonstrated by in-situ XRD, and it keeps the original crystal structure after being exposed to the air for 30 days. The capacity decay of NMCT is effectively decelerated at high voltage (>4.2 V) after La doping, as which can stabilize the structure of the material by reducing the Mn3+ content through suppressing the Jahn-Teller effect. The research with respect to La doping provides a facile and instructive way for the design of high-performance cathode materials for SIBs.

A series of layered Li[Li0.2Mn0.54Ni0.13Co0.13]O2 cathode materials, of which manganese source was electrolytic manganese dioxide, with different contents of SO42− were successfully synthesized via ball-milling process and solid-state sintering method. The obtained materials were characterized by XRD, XPS, SEM-EDS, C-S, ICP, and HR-TEM. All the obtained materials presented well-ordered layered structure. When the content of SO42− was below 1.30 wt%, the electrochemical properties and structural stabilities at low rate for the layered materials with SO42− were not changed dramatically, while when the content of SO42− increased to 5.85 wt%, the initial discharge capacities decreased dramatically from 248.24 to 209.23 mAh g−1 at 10 mA g−1. And the pristine sample shows excellent cyclic property and rate capability. It delivered the discharge capacity of 175.25 mAh g−1 after 100 cycles with the highest capacity retention of 90.67% at 200 mA g−1. Particularly, the treated Li-rich Mn-based materials with the highest amount of SO42− exhibited the best cyclic stability and it delivers the highest capacity retention of 95.17% after 100 cycles at 200 mA g−1. However, its discharge capacities were much lower than the pristine material. As a result, the addition of SO42− could promote side reactions between electrode and electrolyte and deep-degree corrosion of electrode materials to affect the electrochemical properties and structural stabilities of the Li-rich Mn-based materials.

Developing a stable porous cathode material with efficiently bifunctional activity to ORR/OER is key to achieve the high-performance Li-O2 batteries. Here, a three-dimensional (3D) porous nanoaerogels composed of Co3O4-CoFe2O4/CNTs (CO-CFO/CNTs) nanoparticles is synthesized via a facile alginate-derived biomass conversion strategy combining two-pot calcination method and serves as an effectively bifunctional electrocatalysts for Li-O2 batteries. The as-made electrocatalyst possesses a 3D porous structure with large pore volume, which can effectively shorten diffusion lengths, promote the electron transfer and provide numerous active sites. The CO-CFO/CNTs-based Li-O2 batteries exhibit improved discharge capacity of about 7800.3 mA h g−1 at 100 mA g−1, and achieve a favorable cyclability up to 48 cycles with a fixed capacity of 500 mA h g−1 at 200 mA g−1, due to the co-existence of different functional components of Co3O4 and CoFe2O4 and CNTs conductive network. In addition, the discharge product analysis indicates that the Li2O2 is the dominant product and can be completely decomposed, endowing the CO-CFO/CNTs-based Li-O2 batteries with superior performance.

Layered Li-rich and Mn-based oxides have been considered as competitive candidates for Li-ion batteries because of their high capacity (exceed 250 mAh g−1), environmentally benign, and low cost. However, their commercialization is restricted by their inherent drawbacks such as low initial coulombic efficiency, modest cycling performance and poor rate capability. To overcome these problems, we have proposed an construction strategy of a spinel-embedded and Li3PO4 modified Li[Li0.2Mn0.54Ni0.13Co0.13]O2 oxides through a facile wet chemical deposition route. During the modification process, Li+ in the pristine could be partially exchanged by H+ concomitant with the chemical deposition of Li3PO4. After a low-temperature calcination process, the spinel structure is formed accompanied with the extraction of H+ and the interaction between Li3PO4 coating layer and the surface of pristine particles was enhanced. The as-designed structure is characterized by Raman spectra, Energy-dispersive X-ray Spectroscopy (EDS), Transmission Electron Microscopy (TEM), and Cyclic Voltammetry (CV). The practical results confirm that the capacity retentions and rate capability are significantly improved after such modification. The modified sample delivers much higher capacity retention of 83.57% after 150 cycles at 1C rate compared with 70.44% for bare material. Our facile modification approach combines the advantage of spinel phase and Li-ion conductor Li3PO4 particles. It is very effective for the structural construction of robust electrolyte deteriorating durability as well as fast ion diffusion and storage capability in layered Li-rich and Mn-based oxides.

To develop a high-performance capacitive material with both superior power density and energy density, it is very important to construct a nanomaterial with a well-controlled structure. In this work, we report the preparation of NiCo2S4 nanotubes-assembled nanoclusters with a combination of hydrothermal and ion exchange processes. By optimizing the ion-exchange temperature, the tubular morphology can be both achieved and optimized. By tuning the conditions of the synthesis process, the diameter of the primary 1D structure can be increased, which leads to a compact cluster with decreased surface area. In particular, the sample prepared at 180 °C (NCS2) shows the morphology of nanoclusters assembled nanotubes with a wall thickness of about 7 nm. Such an architecture shows excellent electrochemical performance as a pseudocapacitor. It shows an initial specific capacitance of 1005 F g−1 at the current density of 1 A g−1 and remains 896 F g−1 at a current density of 20 A g−1. Moreover, it displays a favorable capacitance retention of 79.34% after 5000 cycles at a current density of 10 A g−1. Furthermore, the NCS2//AC asymmetric supercapacitor exhibits excellent rate performance (retaining 81% of the initial capacity when the current density increases from 1 A g−1 to 20 A g−1) and a high energy density of 52 Wh kg−1 at a power density of 9288 W kg−1. This work lays the foundation for the design and optimization of NiCo2S4 based nanostructured materials for energy storage.

To promote the development of supercapacitors, it is urgent to develop new class of electrode materials with low cost, high energy density and high power density. Ternary metal sulfides are one kind of promising electrode materials for high-performance energy storage devices. Here, a facile one-step potentiostatic deposition method is utilized to produce a binder-free, nanostructured NiCo2S4 electrode on FTO substrates. By controlling the Ni/Co mole ratio of the electrodepositing solution, the nanosheet-like NiCo2S4 free-standing electrode fabricated in the optimized condition exhibits a high specific capacitance of 1080 F g−1 at a current density of 1 A g−1. After 2000 cycles at 5 A g−1, there is no loss of specific capacitance, which is ascribed to the unique structure of the nanosheet arrays. These results reveal that this method can be used as a facile route to synthesize free-standing NiCo2S4 nanosheets-based electrode material of supercapacitors.

Hard carbon draws great interests as anode material in lithium ion batteries (LIBs) due to its high theoretical capacity, high rate capability and abundance of its precursors. Herein we firstly synthesize the lignin-melamine resins by grafting melamine onto lignin. Afterwards, nitrogen doped hard carbon is prepared by the pyrolysis of lignin-melamine resins with the aid of catalyst (Ni(NO3)2·6H2O) at 1000 °C. Compared with the samples without nitrogen-doping and catalysis, as-prepared nitrogen doped hard carbon exhibits higher reversible capacity (345 mAh g–1 at 0.1 A g−1), higher rate capability (145 mAh g−1 at 5 A g–1) and excellent cycling stability. The superior electrochemical performance is ascribed to the synergistic effect of nitrogen doping, graphitic structure and amorphous structure. Among them, nitrogen doping could create the vacancies around the nitrogen sites, which enhance the reactivity and the electronic conductivity of materials. Additionally, graphitic structure also enhances the electronic conductivity of materials, thus improving the electrochemical performance of hard carbon. It is worthwhile that lignin, renewable and abundant biopolymer, is converted to hard carbon with good electrochemical performance, which realizes the high value utilization of lignin.

Even though Li-rich layered oxide is considered to be a promising cathode material for Li-ion batteries because of the high discharge capacity, it still suffers from many fundamental challenges such as low initial coulombic efficiency, the voltage fading upon cycling and poor rate performance. In this work, lithium-rich layered Li[Li0.2Ni0.13Co0.13Mn0.54]O2 cathode materials are pretreated by NH4F through a facile solid state method to overcome these problems. After pretreating, the spinel phase LiM2O4 coating layer is formed accompanying with the formation of oxygen vacancies caused by NH3 decomposed from NH4F. Compared with the pristine material, materials pretreated by appropriate amount of NH4F present significantly improved electrochemical performances such as high initial coulombic efficiency and improved stability in successive electrochemical cycling, excellent rate capability and suppressed voltage decay. The pretreated material delivers the highest initial coulombic efficiency of 102.2% (NF10) compared to 74.5% of NF0 and the highest voltage retention of 90.6% compared to 86.2% of NF0. The NF0 delivers the best comprehensive performance, with higher initial coulombic efficiency and voltage retention, improved rate performance and capacity stability.

The severe degradation of Ni-rich cathode materials on exposure to air is a crucial restriction for their large-scale application. To overcome this issue, a MnO2 functional layer has been introduced to the surface of LiNi0.8Co0.15Al0.05O2 oxide via a wet-chemical method. Compared with pristine sample, the modified LiNi0.8Co0.15Al0.05O2 shows an enhanced chemical stability because of its low sensitivity to moisture and CO2. The formation of absorbed Li2CO3/LiOH species and spontaneous reduction of Ni3+ to Ni2+ on the surface of MnO2-modified sample have been delayed remarkably, which is confirmed by characterizations of SEM, TEM, XPS and FTIR. Benefit from these merits, the modified LiNi0.8Co0.15Al0.05O2 displays a specific capacity of 183 mAh g−1 at 0.1 C after air-storage for 40 days, while the pristine sample drops from 195 to 144 mAh g−1 promptly. Meanwhile, the MnO2 layer inhibits the generation of HF and protects the active material against the erosion of electrolyte in the working cell. Therefore, the MnO2 modified LiNi0.8Co0.15Al0.05O2 after storage shows a capacity retention of 87.1% at 1 C after 100 cycles, which is more stable than that of stored pristine sample (70.3%).

Mg-doped Li[Li0.2Mn0.54 − x/3Ni0.13 − x/3Co0.13 − x/3Mgx]O2 (x = 0, 0.005, 0.007, 0.01, and 0.02) cathode materials have been synthesized by mixing Mn0.54Ni0.13Co0.13(CO3)0.8 precursor, Li2CO3, and MgO, followed by high-temperature solid-state method. X-ray diffraction (XRD) results show that Mg-doped samples have enlarged interlayer distance and orderly layered structure. Scanning electron microscope (SEM) results indicate that all the samples have similar morphologies. Electrochemical tests indicate that Mg doping facilitates the activation of Li2MnO3 phase and suppresses the transformation from layered to spinel-like phase. Mg-doped samples possess improved cyclic and rate performance. The Li[Li0.2Mn0.54 − x/3Ni0.13 − x/3Co0.13 − x/3Mgx]O2 (x = 0.01) sample delivers a capacity retention of 92.07% compared with 75.25% of the undoped one after 200 cycles at 250 mA g−1 and exhibits the discharge capacity of 198.56 mAh g−1 at 500 mA g−1. The reasons for the improved electrochemical performance are the enlarged interslab spacing and the enhanced structural stability.

Conjugated porous polymers (CPPs) possess great potential in the energy storage aspect. In this work, a boron-dipyrromethene (BODIPY)-conjugated porous polymer (CPP-1) is achieved by a traditional organic synthesis route. Following this, a carbonization process is employed to obtain the carbonized porous material (CPP-1-C). The two as-prepared samples, which are characterized by doping with heteroatoms and their porous structure, are able to shorten the lithium-ion pathways and improve the lithium-ion storage property. Then, CPP-1 and CPP-1-C are applied as anode materials in lithium-ion batteries. As expected, long-term cyclic performances at 0.1 and 1 A g–1 are achieved with maintaining the specific capacity at 273.2 mA h g–1 after 100 cycles at 0.1 A g–1 and 250.8 mA h g–1 after 300 cycles at 1 A g–1. The carbonized sample exhibits a better electrochemical performance with a reversible specific capacity of 675 mA h g–1 at 0.2 A g–1. Moreover, the capacity is still stabilized at 437 mA h g–1 after 500 cycles at 0.5 A g–1. These results demonstrate that BODIPY-based CPPs are capable of being exploited as promising candidates for electrode materials in the fields of energy storage and conversion.

In order to improve the rate capability and mitigate the voltage decay of lithium rich layered oxides, chromium doped cathode materials Li1.2[Mn0.54Ni0.13Co0.13]1−xCrxO2 (x = 0,0.003,0.005,0.007) is synthesized via co-precipitation method followed by calcination. As a result, Cr-doped samples present shortened voltage platform at 4.5 V, indicating that the escape of lattice oxygen is suppressed by Cr doping. Among all samples, Li1.2[Mn0.54Ni0.13Co0.13]1−xCrxO2 (x = 0.005) sample shows the greatest rate capability (119.3 mAh g−1 at 10 C) and the minimum voltage drop (0.6167 V) after 200 cycles at 1.0 C. The reasons for the improved electrochemical performance are the enhanced structural stability, the stronger Cr O bond than Mn O band and the decreased metal–oxygen covalency induced by Cr doping.

Generally, sulfur elimination from nickel matte was incomplete in the one-step oxidation roasting process. In this work, X-ray diffraction, scanning electron microscopy/energy-dispersive X-ray spectroscopy, and chemical analysis of the roasted products were carried out to explain this phenomenon. The results indicated that the melting of heazlewoodite was the main limiting factor. Thereafter, the oxidation mechanism of high-grade nickel matte from room temperature to 1000 °C was studied. It was found that the transformation from heazlewoodite (Ni3S2) to nickel sulfide (NiS) took place from 400 °C to 520 °C. Considering that the melting temperature of NiS was much higher than that of Ni3S2, a low-temperature roasting step was suggested to suppress the melting of heazlewoodite. Under the optimum conditions (520 °C for 120 minutes followed by 800 °C for 80 minutes), the degree of desulfurization reached 99.52 pct. These results indicated that the two-step oxidation roasting method could be a promising process for producing low-sulfur calcine from high-grade nickel matte.

Iron oxides are considered as attractive electrode materials because of their capability of lithium storage, but their poor conductivity and large volume expansion lead to unsatisfactory cycling stability. We designed and synthesized a novel Fe3O4 cluster microspheres/Graphene aerogels composite (Fe3O4/GAs), where Fe3O4 nanoparticles were assembled into cluster microspheres and then embedded in 3D graphene aerogels framework. In the spheres, the sufficient free space between Fe3O4 nanoparticles could accommodate the volume change during cycling process. Graphene aerogel works as flexible and conductive matrix, which can not only significantly increase the mechanical stress, but also further improve the storage properties. The Fe3O4/GAs composite as an anode material exhibits high reversible capability and excellent cyclic capacity for lithium ion batteries (LIBs). A reversible capability of 650 mAh g−1 after 500 cycles at a current density of 1 A g−1 can be maintained. The superior storage capabilities of the composites make them potential anode materials for LIBs.

To suppress the capacity fade of Li-rich Li1.2Ni0.13Co0.13Mn0.54O2 material as cathode materials for lithium-ion battery, we introduce a LiF coating layer on the surface to improve the cycling performance of Li1.2Ni0.13Co0.13Mn0.54O2 material. The modified sample shows a capacity of 163.2 mAh g−1 with a capacity retention of 95% after 100 cycles at a current density of 250 mA g−1, while the pristine sample only delivers a capacity of 129.9 mAh g−1 with a capacity retention of 82%. Compared with the pristine material, the LiF-modified sample exhibits an obvious enhancement in the electrochemical performance, which will be very beneficial for this material to be commercialized on the new energy vehicles and other related areas.

In this study we report a series of nickel-rich layered cathodes LiNi 1−2 x Co x Mn x O 2 ( x = 0.075, 0.05, 0.025) prepared from chlorides solution via ultrasonic spray pyrolysis. SEM images illustrate that the samples are submicron-sized particles and the particle sizes increase with the increase of Ni content. LiNi 0.85 Co 0.075 Mn 0.075 O 2 delivers a discharge capacity of 174.9 mAh g −1 with holding 93% reversible capacity at 1 C after 80 cycles, and can maintain a discharge capacity of 175.3 mAh g −1 at 5 C rate. With increasing Ni content, the initial specific capacity increases while the cycling and rate performance degrades in some extent. These satisfying results demonstrate that spray pyrolysis is a powerful and efficient synthesis technology for producing Ni-rich layered cathode (Ni content > 80%).

Compact-structured silicon/carbon composites consisting of silicon, graphite, and coal tar pitch pyrolysis carbon are prepared via two heating procedures after liquid solidification. The first heating procedure plays a key role in the formation of compact-structured silicon/carbon composites, in which the coal tar pitch has a good fluidity at 180 °C above the softening temperature, and it is easy to form a uniform coating on the surface of materials. At the same time, the fluidic coal tar pitch could also fill the voids between particles to form compact-structured silicon/carbon composites. As-prepared silicon/carbon composites exhibit moderate reversible capacity of 602.4 mAh g−1, high initial charge-discharge efficiency of 82.3%, and good cycling stability with the capacity retention of 93.4% at 0.1 A g−1 after 50 cycles. It is noteworthy that the synthetic method is scalable which is suitable for mass production.

Mg-doped lithium-rich layered oxide Li1.2Mn0.54Ni0.13Co0.13O2 with smooth morphology is synthesized by co-precipitation followed by calcination. The morphologies of bare particles and electrodes have been studied through scanning electron microscopy (SEM), which illustrates that, compared with the Mg-doped particles, the pristine particles are characteristic of angular and corrosion is much more likely to happen. Additionally, the Mg substitution can make the crystal structure stable during the electrode process and then enhance the cycle performance. Electrochemical impedance spectroscopy and transmission electron microscopy have been utilized to gain insight to the properties of pristine and Mg-doped particles before and after the electrode process. Mg-doped particles show lower charge transfer resistance and higher diffusion coefficients (D) of the diffusing lithium ions. After 100 cycles at 250 mA g−1, the morphology and crystal structure of Mg-doped materials show smaller changes than those of pristine particles.