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This study demonstrates that magnetron-sputtered NbSe2 film can be used as a lubricant for space current-carrying sliding contact, which accommodates both metal-like conductivity and MoS2-like lubricity. Deposition at low pressure and low energy is performed to avoid the generation of the interference phase of NbSe3. The composition, microstructure, and properties of the NbSe2 films are further tailored by controlling the sputtering current. At an appropriate current, the film changed from amorphous to crystalline, maintained a dense structure, and exhibited excellent comprehensive properties. Compared to the currently available electrical contact lubricating materials, the NbSe2 film exhibits a significant advantage under the combined vacuum and current-carrying conditions. The friction coefficient decreases from 0.25 to 0.02, the wear life increases more than seven times, and the electric noise reduces approximately 50%.

Sb-Doped high-voltage LiCoO2 was developed with unique properties.

Mn-based oxides have been regarded as a promising family of cathode materials for high-performance lithium-ion batteries, but the practical applications have been limited because of severe capacity deterioration (such as LiMnO2 and LiMn2O4) as well as further complications from successive structure changes during cycling, low initial coulombic efficiency (such as Li-rich cathode) and oxidization of organic carbonate solvents at high charge potential (such as LiNi0.5Mn1.5O4). Large amounts of efforts have been concentrated on resolving these issues towards practical applications, and many vital progresses have been carried out. Hence, the primary target of this review is focused on different proposed strategies and breakthroughs to enhance the rate performance and cycling stability of nanostructured Mn-based oxide cathode materials for Li-ion batteries, including morphology control, ion doping, surface coatings, composite construction. The combination of delicate architectures with conductive species represents the perspective ways to enhance the conductivity of the cathode materials and further buffer the structure transformation and strain during cycling. At last, based on the elaborated progress, several perspectives of Mn-based oxide cathodes are summarized, and some possible attractive strategies and future development directions of Mn-based oxide cathodes with enhanced electrochemical properties are proposed. The review will offer a detailed introduction of various strategies enhancing electrochemical performance and give a novel viewpoint to shed light on the future innovation in Mn-based oxide cathode materials, which benefits the design and construction of high-performance Mn-based oxide cathode materials in the future.

Lithium metal-based secondary batteries are very promising for next generation power battery due to their high energy density. However, lithium anodes suffer from poor electrochemical reversibility in organic electrolytes due to Li dendrites and instability of the solid electrolyte interphase. Recent research demonstrated that the problem can be alleviated via tetraethoxysilane (TEOS) treated lithium metal to form a silicon oxide layer on the lithium surface, however, its reaction mechanism is controversial. Herein, we deeply explore the reaction mechanism between TEOS and Li and propose: Fresh Li can directly react with TEOS even though no lithium hydroxide exists on the lithium surface, and the participation of water will accelerate the reaction process. Moreover, it was found that the silicon oxide layer can promote the uniform deposition of lithium ions by providing lithiophilic nucleation sites, thereby achieving a long cycle life of Li metal batteries.

Nitrocellulose (NC) is proposed to stabilize the electrolytes for Li metal batteries. The nitro group of NC preferentially reacts with Li metal, and along with the cellulose skeleton is tightly wrapped on the surface, so that the polymer-inorganic double layer is formed on the Li surface. XPS profile analysis and corroborative cryo-environmental TEM reveal that the flexible outer layer of the bilayer is a C-O organic layer, while the dense inner layer is mainly composed of crystalline lithium oxide, lithium oxynitride, and lithium nitride. The Li deposition process was observed via in situ optical microscopy, which indicated that the NC-derived bilayer facilitates the uniform deposition of Li ions and inhibits the growth of dendrites. After the introduction of NC into the electrolyte, the cycle life of the Li battery is twice than that of the Li battery without NC at 1.0 and 3.0 mA cm-2 .

Electrochemical energy storage (EES) devices having both high power density and high energy density are highly desirable. Although metal-ion hybrid capacitors (MIHCs) integrating a battery-type anode and a capacitor-type cathode are wished to realize this target, state-of-the-art MIHCs just showed the compromise performance between high-power supercapacitors (SCs) and high-energy metal-ion batteries. Herein, we propose a new concept of “device-level integration” to realize the integration of SC, MIHC and dual-ion battery (DIB) in one device. By coupling a mixed and pre-potassiated activated carbon (AC)/graphite anode and another mixed AC/graphite cathode in a K+-based organic electrolyte, as-built device can exhibit three distinctly different energy storage behaviors including SC, MIHC and DIB by simply tuning the applied voltage window. Consequently, this device is able to achieve the maximum power density at 0–2.8 V and the maximum energy density at 0–5.0 V, and exhibits a good combination of high power density and high energy density at 0–4.0 V. This work may open a new avenue for building advanced EES devices with adjustable power and energy output characteristics.

Flexible and Personalizable battery is a promising candidate for energy storage, but suffers from the weldablity and large-scale producibility of the electrode. To address the issues, we design a nickel foam catalyzed electroless deposition (NFED) derived 3D-metal-pattern embroidered electrodes. This is the first attempt to utilize this type of electrode in battery field. It is found that the current collector can be embroidered on any selected areas of any complex-shape electrodes, with high controllability and economical feasibility. As a result, the electronic conductivity of the flexible electrodes can be improved by nearly one order of magnitude, which can be easily and firmly weldded to the metal tab using the industry generic ultrasonic heating process. The embroidered electrodes could substantially promote the electrochemical performance under bending deformation, with both Li-S and Li-LiFePO4 batteries as the models. This innovation is also suitable to embroider all the VIII group elements on any electrodes with personalized shapes, which is widely attractive for the development of next generation flexible and personalizable energy storage devices.

Lithium–sulfur (Li–S) batteries have great potential as an electrochemical energy storage system because of the high theoretical energy density and acceptable cost of financial and environment. However, the shuttle effect leads to severe capacity fading and low coulombic efficiency. Here, graphitic carbon nitride (g–C3N4) is designed and prepared via a feasible and simple method from trithiocyanuric acid (TTCA) to anchor the polysulfides and suppress the shuttle effect. The obtained g–C3N4 exhibits strong chemical interaction with polysulfides due to its high N–doping of 56.87 at%, which is beneficial to improve the cycling stability of Li–S batteries. Moreover, the novel porous framework and high specific surface area of g–C3N4 also provide fast ion transport and broad reaction interface of sulfur cathode, facilitating high capacity output and superior rate performance of Li–S batteries. As a result, Li–S batteries assembled with g–C3N4 can achieve high discharge capacity of 1200 mAh/g at 0.2 C and over 800 mAh/g is remained after 100 cycles with a coulombic efficiency more than 99.5%. When the C–rate rises to 5 C, the reversible capacity of Li–S batteries can still maintain at 607 mAh/g.

In this work, lithium titanate (Li4Ti5O12)/N-doped carbon/stainless steel mesh (LTO/N-C/SSM) flexible electrodes for Li-ion capacitors were successfully prepared without binder via a facile method ...

Li3N is an excellent zero-residue positive electrode pre-lithiation additive to offset the initial lithium loss in lithium-ion capacitors. However, Li3N has an intrinsic problem of poor compatibility with commonly used aprotic polar solvents in electrode manufacture procedure due to its high reactivity with commonly used solvents like N-methy-2-pyrrolidone (NMP) and etc. It is the Valley of Death between research and large-scale commercialization of Li-ion capacitors using Li3N as prelithiation agent. In this work, Li3N containing electrode is prepared by a commercially adoptable route for the first time, using N,N-dimethylformamide (DMF) to homogenate the electrode slurry. The DMF molecular stabilizing mechanism is confirmed via experiment analysis and DFT simulation, indicating that the dehydrogenation energy for DMF is obviously larger than other commonly used solvents such as NMP and etc. The soft package lithium-ion capacitors (LIC250) with only 12 wt% Li3N addition in AC positive electrode exhibits excellent rate capability, cyclic stability and ultrahigh specific energy. Its specific energy is 2.3 times higher than the Li3N-free devices, with energy retention as high as 90% after 10,000 cycles.

The development of primary batteries with high energy density, long shelf life, and stable discharge voltage is essential for civilization and military applications. Primary batteries with high power output and excellent low-temperature performance can further broaden their application. Herein, a Li/LiV2(PO4)3 primary battery was proposed and investigated for the first time. In order to improve the shelf life of the Li/LiV2(PO4)3 primary battery, the mechanism and corresponding inhibition strategy of self-discharge were studied in detail. It was found that the electrolyte composition is a key factor affecting the shelf life of Li/LiV2(PO4)3 primary batteries, where the corrosion of aluminum (Al) current collector triggered by the organic radical cations generated from electrochemical oxidation of the ethylene carbonate (EC) at high potential; and the detrimental reaction between LiV2(PO4)3 and electrolyte lead to the self-discharge of the Li/LiV2(PO4)3 primary battery. When the EC solvent was replaced by the propylene carbonate (PC) solvent, the corrosion of Al foil was alleviated. Moreover, the addition of lithium bis(oxalato)borate (LiBOB) to the electrolyte could improve the stability of cathode/electrolyte interface and enhance the shelf life of the Li/LiV2(PO4)3 primary battery. As a result, 100% capacity could be maintained after over one-month storage, 86% energy could be maintained at 50C, and 63% energy could be maintained at −40 °C at a current density of 0.1C. In addition, the Li/LiV2(PO4)3 primary battery showed great potential for all-weather applications.

Sodium-ion batteries are considered surrogates for conventional lithium-ion batteries for the commercial sector. One of the most favourable anode materials for sodium-ion batteries is hard carbon. However, its performance is affected by the large irreversible capacity loss (ICL) in the initial charge process. This study proposes the Na4V2(PO4)3 (Na4VP) cathode as a possible solution for matching the hard carbon anode. The process uses a recently developed electrochemical pre-sodiation strategy, where the first step converts Na3V2(PO4)3 (Na3VP) to a Na4VP cathode by a sodiation step. After this, a de-sodiation step of Na4VP is carried out below 2.2 V (vs. Na+/Na) to entirely compensate for the ICL of the anode, and the resulting Na3VP directly acts as the cathode. As a result, the Na4VP‖HC full cell achieves a substantially high specific energy of 265 W h kg−1, which is 76% higher than that of the Na3VP‖HC full cell. Moreover, the Na4VP‖HC full cell shows excellent rate performance (62.32 mA h g−1 at 10C) and cycling stability (about 80.0% capacity retention after 100 cycles at 1C). This work is a precursor to the further study of other battery and hybrid capacitor systems, where pre-sodiation plays an important role in improving their performance.

Although water-in-salt (WIS) electrolytes have significantly extended the voltage window of aqueous batteries and supercapacitors, the inevitable precipitation of highly concentrated salts at low temperatures leads to performance degradation and even failure of devices. The introduction of an organic co-solvent can effectively overcome this crucial drawback; however, the underlying mechanism remains unclear. Herein, we demonstrate the study of acetonitrile (ACN) suppressing salt precipitation mechanism in NaClO4-based WIS electrolytes through combining theoretical simulation and experimental analyses. ACN molecules strongly coordinate with Na+ ions to change the solvation structure of the cation–anion from aggregates to contact ion pairs and/or solvent separated ion pairs, weakening the interaction between anions and cations, thereby suppressing the precipitation of NaClO4. Furthermore, using the hybrid electrolyte, a built carbon-based supercapacitor achieves a voltage window of 2.3 V. Impressively, it also retains 86.5% of the room-temperature capacitance and exhibits excellent rate capability and temperature resistance at an ultra-low temperature of −50 °C. This work provides guidance for non-inert co-solvents suppressing salt precipitation, which helps to obtain desired electrolytes for reliable low-temperature supercapacitors.

Lithium-sulfur (Li-S) batteries have received extensive attention because of their high theoretical energy density and low cost. However, the low sulfur utilization and the shuttle effect of polysulfide cause low initial capacity and serious capacity decay. Herein, fluorinated graphite (FG) is introduced to the cathode to alleviate these issues. The results indicated that the FG could provide additional capacity during the first discharge process and increase the porosity and polarity of the cathode via in situ formation of lithium fluoride (LiF) nanocrystals, which can enhance the infiltration of electrolyte and polysulfide adsorption. As a result, the as-prepared cathode containing FG shows a high initial specific capacity of 1602 mA h g-1 and the reversible specific capacity is 650 mA h g-1 at 0.5C after 300 cycles. Moreover, its specific capacity remains at 860 mA h g-1 at 5C, which is 367% higher than that of the sample without FG. This paper provides a new strategy to improve the energy density and the cycle stability of Li-S batteries.

The innovation of electrode structures has been lagging far behind that of materials, hampering the industrialization process of high performance batteries or electro-catalytic systems. Especially for thick electrodes with high active materials loadings, it's inadequate to achieve satisfactory performance, especially working at higher current densities, due to the restricted ion transport rate across the electrodes with traditional densely packed structure. Herein, a vertically aligned laminate porous electrode structure is designed, with ion diffusion route shortened by 85%. As a result, the as prepared C/S electrodes (for Li-S batteries) achieve a sharp increase of specific capacity by 50% at 2 C and show excellent cycling stability with a capacity of 949 mAh g−1 at 0.1 C with sulfur loading of 8.0 mg cm−2. In addition, capacities of 89 and 115 mAh g−1 at 10 C have been achieved for LiFePO4 (LFP) and NaTi2(PO4)3 (NTP) electrodes, respectively, which is over 70% and 130% compared to their contrast with active substances loading of 8.8 and 5.5 mg cm−2. It also shows a good application in the field of electroreduction of CO2.

Molybdate polyanion cathode materials have received lots of research interest for their high specific capacity, high cycling stability and interesting physical and chemical properties. Here, LiCr(MoO4)2, a new deintercalation–intercalation type cathode material for lithium ion batteries, is synthesized and studied. Ultraviolet-visible-near-infrared diffuse reflection, density functional theory calculation and four-probe measurement results suggest that LiCr(MoO4)2 possesses a narrow band gap and high electronic conductivity. Bond-valence-sum maps calculation and electrochemical impedance spectroscopy prove the fast lithium ion transport rate of LiCr(MoO4)2. Benefiting from these advantages, LiCr(MoO4)2 delivers a high specific capacity (250 mA h g−1) and good rate performances. The electrochemical reaction mechanism is studied by in situ X-ray diffraction, which indicates that the lithium ion deintercalation–intercalation is a solid solution process with Cr3+/2+ and Mo6+/5+ redox.

Magnesium ion batteries (MIBs) have attracted significant research attention owing to their low cost, high energy density, and the natural abundance of magnesium. However, lack of compatible cathode materials hinders their further development. Herein, we present a magnesium–lithium hybrid ion battery (MLIB) comprising a Li3V2(PO4)3 (LVP) cathode and magnesium metal anode, where fast reaction kinetics of Li+ ions at the LVP cathode and that of Mg2+ ions at the anode led to high reversible capacities. As a result, a rechargeable MLIB shows excellent rate performance (147.8 and 65.3 mA h g−1 at 50 and 2500 mA g−1 respectively) and capacity retention (99% for 200 cycles), which are the highest values among the reported hybrid batteries using lithium cathodes. To improve temperature adaptability of the designed MLIB, two different kinds of magnesium electrolytes (i.e. all-phenyl-complex and magnesium borohydride in diglyme) and inorganic lithium additives were investigated. It is found that the all-phenyl-complex along with LiCl additives can suppress the freezing of electrolytes effectively even at −40 °C. While, high reversible capacities of 117, 93.4, and 63.1 mA h g−1 can be obtained at 0, −20, and −40 °C respectively, at a current density of 100 mA g−1, showing a very promising prospect for low temperature applications.

With the explosive growth in intermittent renewable sources and the global drive toward decarbonizing the energy economy, reliable large-scale electrical energy storage technologies with high safety and low cost are urgently needed. Aqueous batteries hold the intrinsic advantages of nonflammability and low cost; the zinc//bromine flow battery and LiMn2O4//NaTi2(PO4)3 aqueous rechargeable ion battery are two representative systems with relatively high voltages (1.6 V to 1.8 V in common aqueous solutions). However, the long-term cycling stability of intercalation/de-intercalation type cathode materials is easily impaired by pH fluctuance, while the deposition/dissolution-type zinc anode suffers from zinc dendrites and uneven deposition issues. To avoid these two issues, we propose a novel bromine//NaTi2(PO4)3 hybrid ion battery, involving an aqueous redox pair (Br3−/Br−, with high reactivity in a pH range from 0 to 9) and a high-loading ion intercalation anode (NaTi2(PO4)3, with low working voltage and little volume change). First, the high-performance NTP@C nanoparticles are synthesized by a modified sol–gel method. Then, the three-dimensional NTP@C anode with super high mass loading is designed by employing a porous and conductive carbon substrate. The crossover of bromine in aqueous catholyte is suppressed by an effective bromine complexing agent and the insufficient ion transport in a thick solid anode is conquered by a negative flowing electrolyte. As a result, the hybrid ion battery shows high areal energy density, high power density and promising cycling stability. The full cell can deliver a high energy density and power density of 12.8 mW h cm−2 (109 W h kg−1 based on NTP@C and reacted LiBr) and 29.4 mW cm−2 (250 W kg−1 based on NTP@C and reacted LiBr), respectively. Moreover, the power density can reach 106 mW cm−2 with energy density remaining at 7.95 mW h cm−2 (68 W h kg−1 based on NTP@C and reacted LiBr) at a super high current density of 100 mA cm−2. An average capacity loss of 0.075% per cycle is obtained during a 200-cycle test, demonstrating the great feasibility of the new system. Therefore, this hybrid battery has great potential in large scale electrical energy storage.

Nitrocellulose (NC) is proposed to stabilize the electrolytes for Li metal batteries. The nitro group of NC preferentially reacts with Li metal, and along with the cellulose skeleton is tightly wrapped on the surface, so that the polymer-inorganic double layer is formed on the Li surface. XPS profile analysis and corroborative cryo-environmental TEM reveal that the flexible outer layer of the bilayer is a C-O organic layer, while the dense inner layer is mainly composed of crystalline lithium oxide, lithium oxynitride, and lithium nitride. The Li deposition process was observed via in situ optical microscopy, which indicated that the NC-derived bilayer facilitates the uniform deposition of Li ions and inhibits the growth of dendrites. After the introduction of NC into the electrolyte, the cycle life of the Li battery is twice than that of the Li battery without NC at 1.0 and 3.0 mA cm

Lithium-sulfur (Li-S) batteries are considered as one of the most prospective candidates for electric vehicles, due to their superior theoretical energy density and low cost. However, the issues of polysulfide ion (PS) shuttling and uncontrollable Li dendrite growth hindered their further application. Herein, a multifunctional nanoporous polybenzimidazole (PBI) membrane with well-controllable morphology was successfully designed and fabricated to address the aforementioned obstacles. In this design, the PBI membrane could offer strong chemical binding interaction with PS, thus applying dynamic adsorption toward PS as well as stable sulfur electrochemistry, which is further verified by experiments and density functional theory (DFT) simulation. Moreover, PBI membranes with high porosity and high electrolyte uptake capability can provide ample lithium storage space and abundant Li

Exploring anode materials with fast, safe, and stable Li-(de)intercalation is of great significance for developing next-generation lithium-ion batteries. Monoclinic H-type niobium pentoxide possesses outstanding intrinsic fast Li-(de)intercalation kinetics, high specific capacity, and safety; however, its practical rate capability and cycling stability are still limited, ascribed to the asynchronism of phase change throughout the crystals. Herein this problem is addressed by homogenizing the electron and Li-ion conductivity surrounding the crystals. An amorphous N-doped carbon layer is introduced on the micrometer single-crystal H-Nb

A rechargeable aqueous lithium ion battery containing all-NASICON type cathode and anode materials is proposed and developed for the first time. In the design, LiTi2(PO4)3 and Li3V2(PO4)3 serve as the anode and cathode, respectively, which can fulfill the electrochemical window of aqueous solutions and ensure fast lithium ion diffusion into/from electrodes thus provide a safe, fast, inexpensive aqueous lithium ion battery. However, the capacity fading of the Li3V2(PO4)3 is extremely serious in common aqueous solutions. Therefore, the fading mechanism is systematically investigated and “water in salt” aqueous electrolyte is introduced to further solve the fading problem. Consequently, the cycling stability is greatly improved. Even after 100 cycles at 0.1 C, there remains a high reversible capacity of 104 mAh g−1, which is 83.2% of the initial discharge capacity. Furthermore, benefiting from the all-NASICON electrodes construction and super low freezing point of “water in salt” electrolyte, the aqueous battery deliveries remarkable low-temperature performance. It is a powerful and safe candidate for extreme-situation energy storage applications.

Potentially safe and economically feasible magnesium batteries (MBs) have attracted tremendous research attention as an alternative to high-cost and unsafe lithium ion batteries. In the current work, for the first time, we report a novel room-temperature approach to dope the atomic species sodium between the vanadium oxide crystal lattice to obtain NaV3O8·1.69H2O (NVO) nanobelts. The synthesized NVO nanobelts are used as electrode materials for MBs. The MB cells demonstrate stable discharge specific capacity of 110 mA h g-1 at a current density of 10 mA g-1 and a high cyclic stability, that is 80% capacity retention after 100 cycles, at a current density of 50 mA g-1. Moreover, the effects of cutoff voltages (ranging from 2 to 2.6 V) on their electrochemical performance were investigated. The reason for the limited specific capacity of MBs is attributed to the trapping of Mg ions inside the NVO lattices. This work opens up a new pathway to explore different electrode materials for MBs with improved electrochemical performance.

To obtain a satisfactory rate performance of lithium–sulfur (Li–S) batteries with a high sulfur loading, the vapour induced phase inversion (VIPI) process was used to prepare sponge-like porous electrodes. It is suitable for various solvents, binders and materials on account of phase separation principles and produces electrodes with enhanced adhesive properties, high electrolyte uptake and improved capability in electron/ion transport. As a result, batteries assembled with the VIPIE delivered a high initial discharge capacity of 1171 mA h g−1 and presented a capacity retention of 56.6% within 400 cycles at 0.5C. Additionally, a high discharge capacity of 693 mA h g−1 could be also obtained at 2C due to the facilitated electron/ion transport. An electrode with a high sulfur loading of 19 mg cm−2 could be realized. The 10 mg cm−2 sulfur loaded VIPIE delivered a high capacity of 1300 mA h g−1 at 0.05C (equaling to an areal capacity of 13.0 mA h cm−2) and showed a high capacity retention of 90.7% within 60 cycles at 0.1C.

The compound Li0.93V2.07BO5 (LVBO) has been successfully designed and used for the first time as a cathode material for lithium ion batteries (LIBs). It belongs to a new family of lithium transition metal borates, namely LiMBO3 (M = Mn, Fe or Co), which are regarded as good alternatives to phosphates because of their comparably lower molecular weights, which can lead to a larger theoretical specific capacity than those of phosphate-based LiMPO4. LVBO crystallizes in the space group Pbam with V atom and Li atom occupying the same sites, which makes the structure more stable and brings a disorder effect. Further structure and components of the promising cathode material have been characterized based on the results of X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy and inductively coupled plasma mass spectrometry. The synthesized LVBO/C material displays a nanorod morphology with a size of 20-100 nm and shows good electrochemical activity. When used as cathode material in LIBs, LVBO/C delivers an initial discharge specific capacity of 125 mA h g-1 and exhibits relatively good cycle stability. These results are of great interest for further study of its electrochemical behaviors, which is of significance in exploring new borate cathode materials for LIBs.

Lithium–sulfur batteries are promising for next-generation energy storage devices due to the high energy density and low material cost. However, their development is hampered by the short cycling life and severe polarization induced by shuttle effect of polysulfides and sluggish kinetics of Li2S. Herein, for the first time, LiTi2(PO4)2.88F0.12 (LTP-F0.12) is proposed to anchor and activate sulfide based on its strong interaction with lithium polysulfide and rapid charge transfer behavior. By adding 10 wt% LTP-F0.12 to the cathode, the discharge capacity and discharge rate performance were apparently improved, while the capacity retention of about 70% at 0.1C after 200 cycles was realized, which was much higher than that of pure SP–S cathode (lower than 50%). The activation energy (voltage polarization) was decreased by almost 40%. Additional capacity of 132 mA h g−1 was also provided by the LTP-F0.12 from 3.0 to 1.85 V. This study presents a new insight in promoting the polysulfide conversion kinetics in the sulfur cathode.

Molybdate cathode materials have attracted a lot of attention due to their rich crystal structure, stable skeleton structure and moderate electronic conductivity. In this paper, a new NASICON-type material Li3Cr(MoO4) 3 has been studied for the first time as a cathode material for lithium ion batteries with high specific capacity. Comprehensive studies by X-ray diffraction, UV-vis-IR diffuse reflection, bond valence sum maps calculation, cyclic voltammetry, electrochemical impedance spectroscopy and the Four-Probe method show that Li3Cr(MoO4)3 possesses a narrow band gap, high electronic conductivity and fast lithium ion transport channels, and delivers a high specific capacity (200 mA h g−1) and rate performance. Electrochemical mechanism studies indicate that both the Mo6+/5+ and Cr3+/Cr2+ reactions contribute to the high specific capacity.

The low specific capacity of graphite limits the further increase of the energy density of lithium-ion batteries and their widespread applications. Exploring new anode materials is the key issue. Herein, a new mullite-type compound Bi2Mn4O10 is designed and synthesized. The Bi2Mn4O10/C composite delivers a high reversible specific capacity of 846 mA h g-1 (more than twice that of graphite), and exhibits a high capacity retention of 100% after 300 cycles at 600 mA g-1, which is reported for the first time. The high specific capacity originates from the combination of the conversion reaction and alloying-dealloying reaction, which has been confirmed by the ex situ XRD, IR, SEM and TEM studies. In addition, the unique nanocomposite generated during the charge-discharge process provides excellent cycling stability. This work proves that Bi2Mn4O10/C is a potential anode material for advanced lithium-ion batteries.

The rational design of cathode hosts with superior polysulfide (PS) confinement properties, excellent Li+/e− transport and improved cyclability is of the utmost importance for high-areal-capacity lithium–sulfur (Li–S) batteries. Herein, multi-functional nanowall arrays (MNWAs) combining the aforementioned properties are fabricated to improve the electrochemical performance of Li–S batteries with high areal sulfur loadings. The integrated conductive networks and top-down vertically aligned Li+ transport channels are beneficial to Li+/e− transport, resulting in high rate performance with a discharge capacity of 620 mA h g−1 at a high current density of 9.6 mA cm−2 for 4 mg cm−2 sulfur-loaded S/MNWA electrodes. Additionally, the strong PS shuttling suppression via the synergetic effects of physical confinement and chemical adsorption leads to Li–S batteries with a sulfur loading of 10 mg cm−2 capable of delivering a high areal capacity of 12.4 mA h cm−2 with a high capacity retention of nearly 85% for over 100 cycles. What's more, the Li–S batteries assembled with 4 mg cm−2 sulfur-loaded S/MNWA electrodes show an ultra-low capacity decay of 0.07% per cycle over 400 cycles at 3.2 mA cm−2.

Solid electrolyte has good mechanical strength and can effectively inhibit the growth of lithium dendrite, so it has a good application prospect in lithium batteries , especially solid polymer electrolyte (SPE), such as PEO. Due to the stability of lithium metal and the excellent dissociation ability of lithium salts, PEO and its derivatives are the mainstream SPE materials. PEO performs best at high temperatures. However, the flammability and fluidity of PEO at high temperatures may pose safety concerns. In this study, sodium alginate (SA) was introduced into PEO to improve the mechanical properties of SPE and the safety of the battery through the nanofiber membrane structure. The PEO/SA composite solid electrolyte has excellent flame retardance (LOI = 28.6), good thermal stability (>120 °C) and wide electrochemical window (>4.6 V). This will help further research on lithium batteries with high energy density and voltage.

It’s challenging to obtain pure-phase metastable tetragonal niobium pentoxide (M-Nb2O5) by conventional heating methods, due to the thermodynamical stable temperature region of M-Nb2O5 partially overlaps with that of H- or T-type Nb2O5. Herein, the pure-phase M- ​Nb2O5 is synthesized by utilizing the confinement of amorphous SiO2 shells, and the pure-phase M-Nb2O5 (without SiO2) is investigated as anode material of lithium-ion batteries. The shells can not only cut off the mutual integration among Nb2O5 particles, but also inhibit the rearrangement and mobility of the atoms inside via forming Si-O-Nb bond at the interface, thus could widen the thermodynamic and kinetic stability stable regions of the M-Nb2O5. The physical and electrochemical performance of pure M-Nb2O5 (without SiO2) is characterized as the anode material of lithium-ion batteries, which exhibits an initial capacity of 246 mAh g-1, unprecedented high-rate performance (≈86 mAh g-1 at 4.0 ​A ​g-1) and excellent cycling stability (≈78 mAh g-1 ​at 2.0 ​A ​g-1 after 1000 cycles).

To meet the increasing demand of flexible and wearable electronic devices, a novel injection molding method is established to prepare flexible electrodes with controllable shapes such as film, bowl, wire, etc. It overcomes the materials limitation for traditional methods and could easily create flexible and shapeable electrodes based on 0-D active materials, even with ultra-high loadings and excellent electrochemical performance. Taking flexible and shapeable S/C electrodes as a model, sulfur loadings 24 mg cm−2 based on 30 nm S/C particles are, for the first time, successfully achieved. It can deliver ultra-high an areal capacity of 27.1 mA h cm−2 and a capacity retention of 64.1% after 100 cycles with low electrolyte to sulfur ratio (E/S) of 5.3 µL mg−1. In addition, flexible and shapeable Li-ion battery electrodes based on 17 mg cm−2 0-D Li3V2(PO4)3 (LVP) electrode could also be obtained, achieving excellent C-rate performance and cycling stability, which is 94 mA h g−1 at 5C and nearly 100% capacity retention at 1C during 100 cycles. The results provided a versatile and universal way to create flexible and shapeable electrodes for a variety of energy storage devices.

Although LiNO 3 could effectively solve the polysulfide (PS) shuttle problem in Li-S battery, however, it causes explosive hazards with the cathode composition like gun powder (KNO 3 , Sulfur, and Carbon). Herein, a LiNO 3 -free electrolyte was designed to simultaneously inhibit the PS shuttle and lithium dendrite problem, with pure 1,3-dioxolane (DOL) as the solvent, due to the low K sp of polysulfide as well as the stable SEI on lithium. As a synergistic effect, it enabled the Li-S batteries to achieve 95% coulombic efficiency, 3 times longer cycle life, and a slower self-discharging rate at 55 °C compared to the DOL/DME blend solvent. Four kinds of batteries, from coins to soft packages, were carried out to confirm the superiority of this electrolyte. Li-S soft package batteries with 4000 mAh capacity were assembled, achieving the specific energy of 350 Wh kg −1 and specific power of 60 W kg −1 , which could cycle over 30 times at 0.2 C with high capacity retention of 80%. It is among the best comprehensive Li-S batteries performance reported using LiNO 3 -free electrolyte.

Li3V2(PO4)3 (abbreviated as LVP) is considered as a prospective cathode material for next-generation Li ion batteries due to its high specific capacity and high operating potential. However, its low electronic conductivity and the difficulty in morphology control restrict its widespread application. Carbon coating has been proved to be an effective method for solving these problems. However, too thick a carbon layer will act as a barrier for Li+ diffusion. 3D hierarchical porous materials with unique electronic and structural properties have exhibited outstanding advantages. However, most methods employed for fabricating the hierarchical porous materials need templates and need acid or alkali to remove the template afterwards. This is detrimental to the LVP material because the LVP reacts with both acid and alkali. Here we present a rational design for a hierarchical porous LVP/C nanocomposite via a one-pot process, in which F127 molecules and the LVP colloids induce self-assembly. After high-temperature annealing, the mesoporous structure was developed due to the decomposition of the F127 and then the LVP/C clusters piled up to form stacked macropores. As a cathode for Li ion batteries, the LVP/C nanocomposite exhibited excellent cycle stability (96% capacity retention over 800 cycles) and enhanced high-rate performance (117 mA h g−1 at 20C). This method provides a new approach for synthesizing high-performance 3D hierarchical porous cathode materials used in other energy storage applications.

Secondary batteries have received huge attention due to their attractive features in applications of large-scale energy storage and portable electronic devices, as well as electrical vehicles. In a secondary battery, a membrane plays the role of separating the anode and cathode to prevent the occurrence of a short circuit, while allowing the transport of charge carriers to achieve a complete circuit. The properties of a membrane will largely determine the performance of a battery. In this article, we review the research and development progress of porous membranes in secondary battery technologies, such as lithium-based batteries together with flow batteries. The preparation methods as well as the required properties of porous membranes in different secondary battery technologies will be elucidated thoroughly and deeply. Most importantly, this review will mainly focus on the optimization and modification of porous membranes in different secondary battery systems. And various modifications on commercial porous membranes along with novel membrane materials are widely discussed and summarized. This review will help to optimize the membrane material for different secondary batteries, and favor the understanding of the preparation-structure-performance relationship of porous membranes in different secondary batteries. Therefore, this review will provide an extensive, comprehensive and professional reference to design and construct high-performance porous membranes.

The effect of bismuth (Bi) for both VO2+/VO2+ and V3+/V2+ redox couples in vanadium flow batteries (VFBs) has been investigated by directly introducing Bi on the surface of carbon felt (CF). The results show that Bi has no catalytic effect for VO2+/VO2+ redox couple. During the first charge process, Bi is oxidized to Bi3+ (never return back to Bi metal in the subsequent cycles) due to the low standard redox potential of 0.308 V (vs. SHE) for Bi3+/Bi redox couple compared with VO2+/VO2+ redox couple and Bi3+ exhibit no (or neglectable) electro-catalytic activity. Additionally, the relationship between Bi loading and electrochemical activity for V3+/V2+ redox couple was studied in detail. 2 wt% Bi-modified carbon felt (2%-BiCF) exhibits the highest electrochemical activity. Using it as negative electrode, a high energy efficiency (EE) of 79.0% can be achieved at a high current density of 160 mA/cm2, which is 5.5% higher than the pristine one. Moreover, the electrolyte utilization ratio is also increased by more than 30%. Even the cell operated at 140 mA/cm2 for over 300 cycles, the EE can reach 80.9% without obvious fluctuation and attenuation, suggesting excellent catalytic activity and electrochemical stability in VFBs.

By utilizing hard template method to adjust the mesopore length, and alkali activation to generate micropores, two hierarchical porous carbons (HPCs) were prepared. With controlling of their mesopore length and the activation conditions, the complex system composed by HPCs and electrolyte was simplified and the effect of mesopore length on the performance of HPCs as electrodes in supercapacitors was investigated. It is found that with the mesopore length getting smaller, the ordered area gets smaller and the aggregation occurs, which is caused by the high surface energy of small grains. HPC with long pores (HPCL) exhibits a donut-like morphology with well-defined ordered mesopores and a regular orientation while in HPC with short pores (HPCS), short mesopores are only orderly distributed in small regions. Longer ordered channels form unobstructed ways for ions transport in the particles while shorter channels, only orderly distributed in small areas, results in blocked paths, which may hinder the electrolyte ions transport. Due to the unobstructed structure, HPCL exhibits good rate capability with a capacitance retention rate over 86% as current density increasing from 50 mA/g to 1000 mA/g. The specific capacitance of HPCL derived from the cyclic voltammetry test at 10 mV/s is up to 201.72 F/g, while the specific capacitance of HPCS is only 193.65 F/g.

Aqueous lithium ion batteries have shown advantages of high safety and low cost, because of the use of nontoxic and nonflammable aqueous electrolytes. LiTi2(PO4)3/LiMn2O4 is considered as one of the most promising aqueous lithium ion battery systems for its moderate working voltage, and high electrochemical stability in aqueous electrolytes. However, the critical issue of hydrogen evolution during the charge process hinders its development. In this paper, F− was first introduced in LiTi2(PO4)3 to raise the ion intercalation potential and further to solve the hydrogen evolution problem. Besides, F− doping can decrease the band gap and further increase the intrinsic electronic conductivity. Additionally, the diffusion coefficient of Li+ increased by one order of magnitude after F− doping. Combined with the elevated potential and high conductivity, F-doped LiTi2(PO4)3 exhibited excellent cycling ability and rate performance. As a result, the power density and energy density of LiTi2(PO4)2.88F0.12/LiMn2O4 full cells reach 2794 W kg−1 and 43.7 W h kg−1 respectively, which are among the highest values ever reported for aqueous lithium or sodium ion batteries. The F− doping strategy was demonstrated to be a facile and effective method to fabricate anode materials for high-performance aqueous lithium ion batteries.

Lithium-sulfur (Li-S) batteries with high sulfur loading are urgently required in order to take advantage of their high theoretical energy density. Ether-based Li-S batteries involve sophisticated multistep solid-liquid-solid-solid electrochemical reaction mechanisms. Recently, studies on Li-S batteries have widely focused on the initial solid (sulfur)-liquid (soluble polysulfide)-solid (Li

Lithium-sulfur (Li-S) batteries with high sulfur loading are urgently required in order to take advantage of their high theoretical energy density. Ether-based Li-S batteries involve sophisticated multistep solid-liquid-solid-solid electrochemical reaction mechanisms. Recently, studies on Li-S batteries have widely focused on the initial solid (sulfur)-liquid (soluble polysulfide)-solid (Li2 S2 ) conversion reactions, which contribute to the first 50% of the theoretical capacity of the Li-S batteries. Nonetheless, the sluggish kinetics of the solid-solid conversion from solid-state intermediate product Li2 S2 to the final discharge product Li2 S (corresponding to the last 50% of the theoretical capacity) leads to the premature end of discharge, resulting in low discharge capacity output and low sulfur utilization. To tackle the aforementioned issue, a catalyst of amorphous cobalt sulfide (CoS3 ) is proposed to decrease the dissociation energy of Li2 S2 and propel the electrochemical transformation of Li2 S2 to Li2 S. The CoS3 catalyst plays a critical role in improving the sulfur utilization, especially in high-loading sulfur cathodes (3-10 mg cm-2 ). Accordingly, the Li2 S/Li2 S2 ratio in the discharge products increased to 5.60/1 from 1/1.63 with CoS3 catalyst, resulting in a sulfur utilization increase of 20% (335 mAh g-1 ) compared to the counterpart sulfur electrode without CoS3 .

The intrinsic properties of nanoscale active materials are always excellent for energy storage devices. However, the accompanying problems of ion/electron transport limitation and active materials shedding of the whole electrodes, especially for high-loaded electrode composed of nanoparticles with high specific surface area, bring down their comprehensive performance for practical applications. Here, this problem is solved with the as proposed “phase inversion” method, which allows fabrication of tricontinuous structured electrodes via a simple, convenient, low cost, and scalable process. During this process, the binder networks, electron paths, and ion channels can be separately interconnected, which simultaneously achieves excellent binding strength and ion/electron conductivity. This is verified by constructing electrodes with sulfur/carbon (S/C) and Li3V2(PO4)3/C (LVP/C) nanoparticles, separately delivering 869 mA h g−1 at 1 C in Li–S batteries and 100 mA h g−1 at 30 C in Li–LVP batteries, increasing by 26% and 66% compared with the traditional directly drying ones. Electrodes with 7 mg cm−2 sulfur and 11 mg cm−2 LVP can also be easily coated on aluminum foil, with excellent cycling stability. Phase inversion, as a universal method to achieve high-performance energy storage devices, might open a new area in the development of nanoparticle-based active materials.

The exploration of cathode materials with high capacity and power, fast charge/discharge rate, long lifespan and broad temperature adaptability is a challenge for the practical application of lithium ion batteries. Here, submicro-sheet Li 3 V 2 (PO 4 ) 3 /C (LVP/C) cathode materials have been successfully synthesized via a simple and universal phase-change method. This designed melting process increases the crystallinity and decreases the Li + diffusion distance, which effectively enhances the cycling stability and rate performances of the LVP/C cathode materials. The LVP/C cathode materials exhibit high discharge specific capacity of 130 mAh g −1 in the first cycle. The capacity retention is almost 100% after 100 cycles. In addition, at 10 C, more than 80% of initial discharge capacity is retained after 800 cycles, indicating excellent cycle performance at high rate. Moreover, the synthesized LVP/C materials perform excellent low-temperature properties. At −20 °C, the specific capacity can reach 105 mAh g −1 at 0.5 C. This study provides a novel template-free synthesis method for nano/micro materials.

A novel tri-modal mesoporous carbon (TMC)/S composite as a high performance cathode for Li-S battery is reported. The TMC host, synthesized by a simple sol-gel templating method, possesses one of the highest surface area of 2371 m2 g−1, pore volume of 2.85 cc g−1 and a unique tri-modal mesopore structure (2.5 nm/9 nm/15 nm). Electrochemical tests reveal that the TMC/S–50 wt% nanocomposite cathode delivers an initial capacity up to 1029 mAh g−1 at 3350 mA g−1 (2C), and maintains a high reversible capacity of 843 mAh g−1 after 100 cycles. And it retains a stable capacity of 708 mAh g−1 after 100 cycles at 5025 mA g−1 (charge/discharge in 20 min, 3C). Even with a higher sulfur loading, the TMC/S–70 wt% nanocomposite still reaches a reversible capacity of 700 mAh g−1, and demonstrates a very low decay rate of only 0.088% per cycle over 300 cycles at 838 mA g−1 (0.5C). We attribute such superior performance to the collective effect of tri-modal mesopore architecture, especially to the contribution of the exterior large mesopores (15 nm), designed being not only large enough to accommodate rapid electrolyte transport, moreover, small enough to serve as additional buffer spaces for polysulfides entrapment.