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Nanostructuring has significantly contributed to alleviating the huge volume expansion problem of the Ge anodes. However, the practical use of nanostructured Ge anodes has been hindered due to several problems including a low tap density, poor scalability, and severe side reactions. Therefore, micrometer-sized Ge is desirable for practical use of Ge-based anode materials. Here, micronized Ge3N4 with a high tap density of 1.1 mg cm−2 has been successfully developed via a scalable wet oxidation and a subsequent nitridation process of commercially available micrometer-sized Ge as the starting material. The micronized Ge3N4 shows much-suppressed volume expansion compared to micrometer-sized Ge. After the carbon coating process, a thin carbon layer (≈3 nm) is uniformly coated on the micronized Ge3N4, which significantly improves electrical conductivity. As a result, micronized Ge3N4@C shows high reversible capacity of 924 mAh g−1 (2.1 mAh cm−2) with high mass loading of 3.5 mg cm−2 and retains 91% of initial capacity after 300 cycles at a rate of 0.5 C. Additionally, the effectiveness of Ge3N4@C as practical anodes is comprehensively demonstrated for the full cell, showing stable cycle retention and especially excellent rate capability, retaining 47% of its initial capacity at 0.2 C for 12 min discharge/charge condition. [ABSTRACT FROM AUTHOR]

Germanium (Ge) possesses a great potential as a high-capacity anode material for lithium ion batteries but suffers from its poor capacity retention and rate capability due to significant volume expansion by lithiation. Here, a facile synthetic route is introduced for producing nanometer-sized Ge crystallites interconnected by carbon (GEC) via thermal decomposition of a Ge-citrate complex followed by a calcination process in an inert atmosphere. The GEC electrode shows outstanding electrochemical performance, i.e., an almost 98.8% capacity retention of 1232 mAh g−1, even after 1000 cycles at the rate of C/2. Importantly, a high discharge capacity of 880 mAh g−1 is maintained at the very high rate of 10 C. The excellent anode performance of GEC stems from both effective buffering of carbon anchored to the Ge nanocrystals and the high open porosity of the GEC aggregated powder with an average pore diameter of 32 nm. Furthermore, the interfacial layer formed between Ge and carbon plays an essential role in prolonging the cycle life. The GEC electrode can be successfully employed as an anode for next generation lithium ion batteries. [ABSTRACT FROM AUTHOR]

Sodium-ion batteries (SIBs) have been increasingly studied due to sodium (Na) being an inexpensive ionic resource (Na) and their battery chemistry being similar to that of current lithium-ion batteries (LIBs). However, SIBs have faced substantial challenges in developing high-performance anode materials that can reversibly store Na+ in the host structure. To address these challenges, molybdenum sulfide (MoS2)-based active materials have been considered as promising anodes, owing to the two-dimensional layered structure of MoS2 for stably (de)inserting Na+. Nevertheless, intrinsic issues of MoS2—such as low electronic conductivity and the loss of active S elements after a conversion reaction—have limited the viability of MoS2 in practical SIBs. Here, we report MoS2 embedded in carbon nanofibers encapsulated with a reduced graphene oxide (MoS2@CNFs@rGO) composite for SIB anodes. The MoS2@CNFs@rGO delivered a high capacity of 345.8 mAh g−1 at a current density of 100 mA g−1 for 90 cycles. The CNFs and rGO were synergistically taken into account for providing rapid pathways for electrons and preventing the dissolution of S sources during repetitive conversion reactions. This work offers a new point of view to realize MoS2-based anode materials in practical SIBs. [ABSTRACT FROM AUTHOR]

The Cover picture shows an electric car powered by a Li–O2 battery driven on a road. The road is covered with graphene, which implies that the Li–O2 battery is supported by an air cathode catalyst composed of oxide nanofibers/nanoparticles attached onto graphene. The small yellow balls are RuO2 nanoparticles whereas the black wires are LaMnO3 nanofibers acting as efficient catalysts for discharging/charging battery. The big yellow balls represent lithium ions, red balls are oxygen molecules, and the gray rocks on the nanofibers are solid reaction products (Li2O2). More details can be found in the Full Paper by Yoon et al. on page 2080 in Issue 16, 2016 (DOI: 10.1002/cssc.201600341). [ABSTRACT FROM AUTHOR]

Silicon-coated molybdenum sulfide nanosheets were prepared in a thin-film shape (Si–MoS 2 TFs) through metal organic chemical vapor deposition (MOCVD) and radio frequency (RF) sputtering. By using MOCVD, the MoS 2 thin films composed of nanosheets were vertically grown on stainless steel substrates. To address the problem of polysulfide dissolution and shuttling effect of MoS 2 during discharge and charge reactions in thin-film Li-ion batteries, the entire surfaces of MoS 2 TFs were covered with silicon layers using RF sputtering. Compared with pristine MoS 2 TFs without protection, the Si–MoS 2 TFs showed excellent reversibility with a high capacity of ∼2000 mAh g−1 for 500 cycles in thin-film Li-ion batteries. Both materials – MoS 2 and Si – were synergistically taken into account to enhance the ability to store Li ions in the host structures and complement each other during repeated conversion and alloying reactions. The underlying reaction principle was elucidated, which provides insight into developing MoS 2 -based thin-film cathodes. [ABSTRACT FROM AUTHOR]

Abstract Formation cycle is a significant step in battery processing, as it leads to the build-up of stable solid electrolyte interphase layer that affects various parameters of batteries. Although fast formation cycle is more economical way to realize the battery production, it is generally known that fast formation cycle of conventional electrode materials leads to capacity degradation. In this study, we report the high-rate formation cycle step to induce excellent electrochemical performance, in the case of Co 3 O 4 nanoparticle. Surprisingly, Co 3 O 4 nanoparticle that runs in the formation cycle at rather high current density (1.0 A g−1) exhibits superior electrochemical performance compared with Co 3 O 4 nanoparticle that runs in the formation cycle at 0.05 A g−1. Such enhanced electrochemical performance after the high-rate formation cycle for Co 3 O 4 can be mainly attributed to the stabilization of solid electrolyte interphase layer upon cycling and initial partial agglomeration that forms secondary particles. This work firstly paves the possibility of employing high-rate formation cycle to induce improved electrochemical performance, which can also be extended to various alternative electrode materials. Graphical abstract Image 1 Highlights • Detailed in-depth study on the effect of high-rate formation cycle. • The effect of formation cycle was investigated for Co 3 O 4. • High-rate formation cycle leads to enhanced electrochemical performance. • Both interfacial and morphological transitions depend on formation cycle. [ABSTRACT FROM AUTHOR]

Abstract LiNi 0.5 Mn 1.5 O 4 (LNMO) cathode thin films were prepared on Pt-coated stainless steel (SS) substrates by radio-frequency magnetron sputtering. The layers were post-annealed at 500, 600 and 700 °C to study the impact of thermal treatment on the crystallization of the cathode material. As the annealing temperature increases, interdiffusion occurs between the substrate and the LNMO film, which degrades the electrochemical properties of the cathode film. In order to mitigate this problem, an In-Sn-O (ITO) interlayer was introduced between Pt and the SS substrate. The ITO film is electrochemically stable and acts as an effective diffusion barrier between the substrate and the LNMO layer, which results in improved electrochemical properties of the LNMO film for a lithium ion battery. [ABSTRACT FROM AUTHOR]

Abstract Increasing the specific capacity and cycle life of graphitic carbon anodes is crucial for realizing high-performance lithium ion batteries. Herein, we introduce a new class of graphitic carbon anodes comprising highly ordered three-dimensional nanostructures decorated with SnO 2 nanoparticles. The inch-scale, nanostructured graphitic carbon matrices are prepared by supported pyrolysis of epoxy templates patterned by advanced optical lithography. During the subsequent decoration process, the SnO 2 nanoparticles are densely formed on the matrix without agglomeration since the periodic nanostructured matrix provides a homogeneous site for nucleation and growth. The surface coverage of the decorated SnO 2 nanoparticles and the mass relative to the graphitic carbon are >80% and ∼50 wt%, respectively. The resulting nanostructured C/SnO 2 composite monoliths can be assembled solely into LIB coin cells without the aid of binders and conducting agents. The achieved specific capacity and retention are 692 mAh g−1 and 87.31% (at 70th cycle), respectively, which is superior to those of nanostructured carbon anodes prepared in a similar way. [ABSTRACT FROM AUTHOR]

Abstract Lithium-ion batteries (LIBs) with higher energy density are necessary to meet the increasing demands of energy storage system (ESS) in near future. Tin (IV) oxide, SnO 2 , is one of highly promising anode candidates due to its high theoretical capacity (782 mAh g−1), abundance, environmental friendliness, and safety with organic electrolytes. However, a rapid capacity fading and poor rate capabilities arising from the large volume expansion and subsequent agglomeration of Sn nanoparticles have been major issues of SnO 2. Here, we have synthesized one-dimensional (1D) SnO 2 -amorphous titanium (IV) oxide NTs (SnO 2 -a-TiO 2 NTs), which allow both facile ionic and electron transport as well as easy penetration of electrolytes. The resultant SnO 2 -a-TiO 2 NTs not only alleviate volume expansion by maintaining their structural integrity but also possess minimal charge transfer resistance even after a number of cycles. SnO 2 -a-TiO 2 NTs exhibit both excellent cycle retention characteristics (1050.2 mAh g−1 after 250 cycles) and outstanding rate capability (522.3 mAh g−1 at a current density of 5000 mA g−1), which is attributed to the introduction of amorphous TiO 2 that not only acts as buffer agent for volume changes of SnO 2 but also allows fast surface-controlled diffusion process due to its pseudocapacitive charge storage mechanisms. Graphical abstract Image 1 Highlights • Introduction of amorphous TiO 2 into SnO 2 nanotubes (SnO 2 -a-TiO 2 NTs). • SnO 2 -a-TiO 2 NTs fabricated by one-step electrospinning and calcination. • Incorporation of amorphous TiO 2 leads to higher Li diffusivity. • SnO 2 -a-TiO 2 NTs exhibit excellent cycle retention and rate capabilities. • Amorphous TiO 2 effectively alleviates the volume changes of SnO 2. [ABSTRACT FROM AUTHOR]

In the recent times, pseudocapacitive electrode materials have received great attention due to their considerable capability in storing ions at relatively fast charging rates. Among various candidates, niobium (V) pentoxide (Nb 2 O 5 ) has gained much attraction for lithium-ion batteries (LIBs) due to its insertion/extraction reaction with Li, safe redox potential, and considerably good capacity (about 200 mAhg −1 ). Nevertheless, low conductivity of Nb 2 O 5 has so far prevented its use as a viable electrode material for LIBs. In this study, we have successfully coated silver (Ag) nanoparticles (NPs) on the surface of one-dimensional orthorhombic Nb 2 O 5 fiber (1D T-Nb 2 O 5 ) using simple electrospinning processing. Ag NPs coated Nb 2 O 5 fibers (Ag-1D T-Nb 2 O 5 ) provided faster electron pathways, resulting in much improved capacity at a given current density with superior rate capabilities compared with pristine 1D T-Nb 2 O 5 . In addition, 1D T-Nb 2 O 5 was more suitable for coating Ag NPs compared with T-Nb 2 O 5 NPs, where its structural integrity was maintained even after cycling. As a result, effective coating of conductive Ag NPs on the 1D T-Nb 2 O 5 resulted in excellent cycle retention characteristics (179.7 mAhg −1 after 500 cycles at 500 mA g −1 ) as well as superior rate capabilities (103.6 mAhg −1 at a current density of 5000 mA g −1 ). [ABSTRACT FROM AUTHOR]

Careful modulation of surficial and interfacial properties of electrode materials is a critical factor for determining overall electrochemical characteristics. Recent studies have indicated that metal oxide nanocoating layer (such as titanium (IV) oxide (TiO 2 )) on metal oxide anodes (such as tin (IV) oxide (SnO 2 )) exhibited superior electrochemical properties, but fundamental research on the effect and role of TiO 2 layer thickness has been limited. Here we have successfully conducted in-depth study on how the thickness of TiO 2 overlayer on SnO 2 can have significant influence in the overall parameters of electrochemistry. It is revealed that TiO 2 overlayer with 12 nm shows good cycle retention (75.8%) even after 80 cycles and retains capacity of 438.3 mAh g −1 even at high current density (5000 mA g −1 ). Surprisingly, it was further discovered that TiO 2 layer not only alleviates the volume expansion but also helps to facilitate Li ion transport compared with SnO 2 . The improvements in both ionic and electrical conductivity of TiO 2 layer are main factors in better cycle retention and rate capabilities. Finally, in situ transmission electron microscopy analysis was adopted to observe the growth dynamics of solid electrolyte interphase layer on TiO 2 @SnO 2 , which demonstrates that TiO 2 overlayer results in homogeneous and thinner interphase layer compared with SnO 2 NTs. [ABSTRACT FROM AUTHOR]

Ultra-stable pseudocapacitive electrodes for lithium-ion batteries (LIBs) are increasing in demand as highly sustainable energy storage system with excellent charge transport is important. The establishment of facile, controllable, and scalable synthesis of pseudocapacitive electrode materials is an attractive solution to realize such objectives. Here, we have successfully fabricated mesoporous orthorhombic Nb 2 O 5 nanofibers (m-T-Nb 2 O 5 NFs) by simple single-spinneret electrospinning followed by calcination at 600 °C. As-formed m-T-Nb 2 O 5 NFs exhibit high surface area (23.7 m 2 g −1 ) and a number of mesopores in the vacant sites where organic polymer was once decomposed. Such rationally designed m-T-Nb 2 O 5 -NFs allow facile Li ion and electron transport, with pseudocapacitive behavior. Arising from the high surface area coupled with mesopores in-between the Nb 2 O 5 nanograins, it exhibits ultra-long cycle retention (a capacity of ∼160 mAh g −1 at 500 mA g −1 after 2000 cycles and ∼88 mAh g −1 at 3000 mA g −1 after 5000 cycles) and higher rate capability (∼70 mAh g −1 at 5000 mA g −1 ). Such cycle retention characteristics of m-T-Nb 2 O 5 -NFs are at least 100-fold slower capacity decay compared with previously reported one-dimensional (1D) Nb 2 O 5 nanostructures and even superior or comparable to recently reported Nb 2 O 5 -graphene composite materials. [ABSTRACT FROM AUTHOR]

Abstract: Polyimide (PI) nanofibers with an average diameter of 300 nm, possessing superior electrolyte wettability and thermal stability, are synthesized by electrospinning a poly(amic acid) (PAA) solution followed by an imidization process. The large pore volume of the PI nanofiber mat can facilitate faster Li+-ion transport and greater rate capability, but it also cause an irreversible increase in cell impedance during long term cycling. To overcome these problems, thin Al2O3 over-layers are coated on both sides of a PI separator via a dip-coating process. The Al2O3-coated PI separators exhibit enhanced capacity, cyclability (95.53% retention after 200 cycles at 1 C), and rate capabilities (78.91% at 10 C) compared to the bare PI separator (68.65% at 10 C) and a commercial polypropylene separator (18.25% at 10 C) with a limited increase of cell impedance. [Copyright &y& Elsevier]

Designinga highly efficient catalyst is essential to improve theelectrochemical performance of Li–O2batteries forlong-term cycling. Furthermore, these batteries often show significantcapacity fading due to the irreversible reaction characteristics ofthe Li2O2product. To overcome these limitations,we propose a bifunctional composite catalyst composed of electrospunone-dimensional (1D) Co3O4nanofibers (NFs)immobilized on both sides of the 2D nonoxidized graphene nanoflakes(GNFs) for an oxygen electrode in Li–O2batteries.Highly conductive GNFs with noncovalent functionalization can facilitatea homogeneous dispersion in solution, thereby enabling simple anduniform attachment of 1D Co3O4NFs on GNFs withoutrestacking. High first discharge capacity of 10 500 mAh/g andsuperior cyclability for 80 cycles with a limited capacity of 1000mAh/g were achieved by (i) improved catalytic activity of 1D Co3O4NFs with large surface area, (ii) facile electrontransport via interconnected GNFs functionalized by Co3O4NFs, and (iii) fast O2diffusion throughthe ultrathin GNF layer and porous Co3O4NFnetworks. [ABSTRACT FROM AUTHOR]

• Synthesis of MFC from low-grade gum wastes. • The synthesized MFC possesses high tap density (1.4–1.7 g cm−3). • High tap density leads to outstanding volumetric capacity at 3.0 A g−1. • MFC also exhibits ultra-stable high-rate cyclability (0.001881% decrease per cycle). • Structural integrity was well maintained even after cycling. Among various natural wastes, gum wastes pose major issues, as they are unusable and hard to be disposed due to their acidic and sticky nature. Herein, a rational synthetic strategy is employed to transform various kinds of gum wastes into micron-sized carbon, which also exhibit high tap density (1.4–1.7 g cm−3) desirable for practical application in lithium-ion batteries (LIBs). Gum karaya (GK) micron-size functional carbon (GKMFC) exhibits the most outstanding electrochemical performance, with a volumetric capacity of 175.4 mAh cm−3 at a current density of 3000 mA g−1 for 5000 cycles, and possesses ultra-stable high-rate cyclability (a capacity decay of only 0.001881% per cycle). Additional electrochemical analyses reveal that GKMFC exhibits stable structural integrity as well as minimal cell resistance even after cycling, showing its practical application as viable electrode for LIBs. This work sheds light on utilizing high tap density carbon from gum wastes for LIBs, which can also be applicable to other natural wastes and carbon. Image, graphical abstract [ABSTRACT FROM AUTHOR]