Sb-Doped high-voltage LiCoO2 enabled improved structural stability and rate capability for high-performance Li-ion batteries.

Sb-Doped high-voltage LiCoO2 was developed with unique properties. In situ X-ray diffraction and density functional theory reveal that the introduction of Sb helps to shorten the Li+ diffusion distance, increase the lattice spacing and keep the structural stability during deep lithiation, thus resulting in improved rate capability and cycling performance.

Fluorinated Graphite (FG)-Modified Li-S Batteries with Superhigh Primary Specific Capacity and Improved Cycle Stability.

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.

Endogenous Symbiotic Li3 N/Cellulose Skin to Extend the Cycle Life of Lithium Anode.

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 .

Stop Four Gaps with One Bush: Versatile Hierarchical Polybenzimidazole Nanoporous Membrane for Highly Durable Li-S Battery.

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+ supplements to facilitate Li deposition and improve Li metal batteries' cyclic stability. Besides that, the PBI membrane has excellent mechanical and thermal stability and exclusive flame resistance, which guarantees the safety of the Li-S battery as well. As a result, Li-S batteries assembled with an as-developed PBI membrane demonstrated a remarkable rate capability of 780 mAh g-1 at 2C and an impressive reversible capacity of 523 mAh g-1 at 0.5C after 400 cycles, which is much higher than the commercial separators. More importantly, even with a lofty sulfur loading of 3 mg cm-2, a high discharge capacity of 744 mAh g-1 (capacity retention 93.96%, at 0.1C after 100 cycles) can also be achieved. Overall, the current study highlighted a robust material platform for stable, safe, and efficient multifunctional separators for high-performance Li-S batteries.

Ultrafast and Stable Li-(De)intercalation in a Large Single Crystal H-Nb2 O5 Anode via Optimizing the Homogeneity of Electron and Ion Transport.

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-Nb2 O5 particle to optimize the homogeneity of electron and Li-ion transport. As a result, the as-prepared H-Nb2 O5 exhibits high reversible capacity (>250 mAh g-1 at 50 mA g-1 ), unprecedented high-rate performance (≈120 mAh g-1 at 16.0 A g-1 ) and excellent cycling stability (≈170 mAh g-1 at 2.0 A g-1 after 1000 cycles), which is by far the highest performance among the H-Nb2 O5 materials. The inherent principle is further confirmed via operando transmission electron microscopy and X-ray diffraction. A novel insight into the further development of electrode materials forlithium-ion batteries is thus provided.

"Water in salt/ionic liquid" electrolyte for 2.8 V aqueous lithium-ion capacitor.

Development of high-voltage electrolytes with non-flammability is significantly important for future energy storage devices. Aqueous electrolytes are inherently non-flammable, easy to handle, and their electrochemical stability windows (ESWs) can be considerably expanded by increasing electrolyte concentrations. However, further breakthroughs of their ESWs encounter bottlenecks because of the limited salt solubility, leading to that most of the high-energy anode materials can hardly function reversibly in aqueous electrolytes. Here, by introducing a non-flammable ionic liquid as co-solvent in a lithium salt/water system, we develop a "water in salt/ionic liquid" (WiSIL) electrolyte with extremely low water content. In such WiSIL electrolyte, commercial niobium pentoxide (Nb2O5) material can operate at a low potential (-1.6 V versus Ag/AgCl) and contribute its full capacity. Consequently, the resultant Nb2O5-based aqueous lithium-ion capacitor is able to operate at a high voltage of 2.8 V along with long cycling stability over 3000 cycles, and displays comparable energy and power performance (51.9 Wh kg-1 at 0.37 kW kg-1 and 16.4 Wh kg-1 at 4.9 kW kg-1) to those using non-aqueous electrolytes but with improved safety performance and manufacturing efficiency.

3D-metal-embroidered electrodes: dreaming for next generation flexible and personalizable energy storage devices.

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.

DMF stabilized Li3N slurry for manufacturing self-prelithiatable lithium-ion capacitors.

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.

Promoting the Transformation of Li2 S2 to Li2 S: Significantly Increasing Utilization of Active Materials for High-Sulfur-Loading Li-S 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 (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 .

Bi2Mn4O10: a new mullite-type anode material for lithium-ion batteries.

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.

Li0.93V2.07BO5: a new nano-rod cathode material for lithium ion batteries.

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.

Low-Cost Room-Temperature Synthesis of NaV3O8·1.69H2O Nanobelts for Mg Batteries.

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.

Porous membranes in secondary battery technologies.

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.

Layer-by-Layer Assembled C/S Cathode with Trace Binder for Li-S Battery Application.

The C/S cathode with only 0.5 wt % binder, composed with Nafion and PVP, was assembled layer-by-layer for lithium-sulfur battery (Li-S) application. It achieved excellent binding strength and battery performance compared to the cathode with 10 wt % PVDF, which is promising to further increase the practical energy density of Li-S batteries.

Lithium Sulfur Primary Battery with Super High Energy Density: Based on the Cauliflower-like Structured C/S Cathode.

The lithium-sulfur primary batteries, as seldom reported in the previous literatures, were developed in this work. In order to maximize its practical energy density, a novel cauliflower-like hierarchical porous C/S cathode was designed, for facilitating the lithium-ions transport and sulfur accommodation. This kind of cathode could release about 1300 mAh g(-1) (S) capacity at sulfur loading of 6 ~ 14 mg cm(-2), and showed excellent shelf stability during a month test at room temperature. As a result, the assembled Li-S soft package battery achieved an energy density of 504 Wh kg(-1) (654 Wh L(-1)), which was the highest value ever reported to the best of our knowledge. This work might arouse the interests on developing primary Li-S batteries, with great potential for practical application.

A Bi-doped Li3V2(PO4)3/C cathode material with an enhanced high-rate capacity and long cycle stability for lithium ion batteries.

Bi-doped compounds Li3V2-xBix(PO4)3/C (x = 0, 0.01, 0.03, 0.05, 0.07) are prepared by a sol-gel method. The effects of Bi doping on the physical and electrochemical properties of Li3V2(PO4)3 are investigated. X-ray diffraction (XRD) analysis indicates that Bi doping does not change the monoclinic structure of Li3V2(PO4)3. A detailed analysis of the XRD patterns suggests that Bi(3+) ions partly enter into the crystal structure of Li3V2(PO4)3 and enlarge the lattice volume of Li3V2(PO4)3. According to the results of cycle and rate performance measurements, moderate Bi(3+) doping is beneficial in improving the electrochemical properties of Li3V2(PO4)3. Among all the samples, Li3V1.97Bi0.03(PO4)3/C shows the best cycle and rate performance. At 3.0-4.3 V, the initial discharge capacity of Li3V1.97Bi0.03(PO4)3/C is as high as 130 mA h g(-1), close to the theoretical specific capacity of 133 mA h g(-1). The capacity retention of Li3V1.97Bi0.03(PO4)3/C is almost 100% after 100 cycles at 3.0-4.3 V. In addition, Li3V1.97Bi0.03(PO4)3/C exhibits excellent low-temperature and high-rate performance. Impedance spectroscopy (EIS) and cyclic voltammetry (CV) curves indicate lower charge transfer resistance and a larger Li ion diffusion rate of Li3V1.97Bi0.03(PO4)3/C than the primary Li3V2(PO4)3/C. The excellent electrochemical performance of Li3V1.97Bi0.03(PO4)3/C can be attributed to its larger Li ion diffusion channels, higher electronic conductivity, higher structural stability and smaller particle size.

Carbon-Free CoO Mesoporous Nanowire Array Cathode for High-Performance Aprotic Li-O2 Batteries.

Although various kinds of catalysts have been developed for aprotic Li-O2 battery application, the carbon-based cathodes are still vulnerable to attacks from the discharge intermediates or products, as well as the accompanying electrolyte decomposition. To ameliorate this problem, the free-standing and carbon-free CoO nanowire array cathode was purposely designed for Li-O2 batteries. The single CoO nanowire formed as a special mesoporous structure, owing even comparable specific surface area and pore volume to the typical Super-P carbon particles. In addition to the highly selective oxygen reduction/evolution reactions catalytic activity of CoO cathodes, both excellent discharge specific capacity and cycling efficiency of Li-O2 batteries were obtained, with 4888 mAh gCoO(-1) and 50 cycles during 500 h period. Owing to the synergistic effect between elaborate porous structure and selective intermediate absorption on CoO crystal, a unique bimodal growth phenomenon of discharge products was occasionally observed, which further offers a novel mechanism to control the formation/decomposition morphology of discharge products in nanoscale. This research work is believed to shed light on the future development of high-performance aprotic Li-O2 batteries.

Hierarchical micron-sized mesoporous/macroporous graphene with well-tuned surface oxygen chemistry for high capacity and cycling stability Li-O2 battery.

Nonaqueous Li-O2 battery is recognized as one of the most promising energy storage devices for electric vehicles due to its super-high energy density. At present, carbon or catalyst-supporting carbon materials are widely used for cathode materials of Li-O2 battery. However, the unique electrode reaction and complex side reactions lead to numerous hurdles that have to be overcome. The pore blocking caused by the solid products and the byproducts generated from the side reactions severely limit the capacity performance and cycling stability. Thus, there is a great need to develop carbon materials with optimized pore structure and tunable surface chemistry to meet the special requirement of Li-O2 battery. Here, we propose a strategy of vacuum-promoted thermal expansion to fabricate one micron-sized graphene matrix with a hierarchical meso-/macroporous structure, combining with a following deoxygenation treatment to adjust the surface chemistry by reducing the amount of oxygen and selectively removing partial unstable groups. The as-made graphene demonstrates dramatically tailored pore characteristics and a well-tuned surface chemical environment. When applied in Li-O2 battery as cathode, it exhibits an outstanding capacity up to 19 800 mA h g(-1) and is capable of enduring over 50 cycles with a curtaining capacity of 1000 mA h g(-1) at a current density of 1000 mA g(-1). This will provide a novel pathway for the design of cathodes for Li-O2 battery.

Steam-etched spherical carbon/sulfur composite with high sulfur capacity and long cycle life for Li/S battery application.

Spherical carbon material with large pore volume and specific area was designed for lithium/sulfur (Li/S) soft package battery cathode with sulfur loading over 75%, exhibiting good capacity output (about 1300 mAh g(-1)-S) and excellent capacity retention (70% after 600 cycles) at 0.1 C. The spherical carbon is prepared via in situ steam etching method, which has the advantages of low cost and easy scale up.

Membranes with well-defined ions transport channels fabricated via solvent-responsive layer-by-layer assembly method for vanadium flow battery.

In this work we presented a general strategy for the fabrication of membranes with well-defined ions transport channels through solvent-responsive layer-by-layer assembly (SR-LBL). Multilayered poly (diallyldimethylammonium chloride) (PDDA) and poly (acrylic acid) (PAA) complexes were first introduced on the inner pore wall and the surface of sulfonated poly (ether ether ketone)/poly (ether sulfone) (PES/SPEEK) nanofiltration membranes to form ions transport channels with tuned radius. This type of membranes are highly efficient for the separators of batteries especially vanadium flow batteries (VFBs): the VFBs assembled with prepared membranes exhibit an outstanding performance in a wide current density range, which is much higher than that assembled with commercial Nafion 115 membranes. This idea could inspire the development of membranes for other flow battery systems, as well as create further progress in similar areas such as fuel cells, electro-dialysis, chlor-alkali cells, water electrolysis and so on.