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sodium ion batteries are considered as excellent energy storage battery materials with the characteristic of low cost and renewability. As a critical component of sodium-ion energy storage batteries, cathode materials have attracted great attention from scientists around the world. Recently, Na 4 Fe 3 (PO 4) 2 P 2 O 7 (NFPP) which offer a theoretical capacity of 129 mAh g−1 has garnered widespread attention. However, the formation of inactive maricite NaFePO 4 (NFP) and low capacity Na 2 FeP 2 O 7 (Na 2 FPO) during the synthesis process restricts the capacity utilization, while poor conductivity further limits its electrochemical performance. To address these issues, here, Na 3.95 Fe 2.95 V 0.05 (PO 4) 2 P 2 O 7 /C (V 0.05 -NFPP/C) composite material was synthesized and assembled into cell for testing. A capacity of 114 mAh g−1 was given at 0.1 C and rate performance also represent 90 mAh g−1 at 10 C. Vanadium-ion improves the dynamic performance by inhibiting maricite NFP and participating in electrochemical reactions. Furthermore, sodium-ion storage mechanism of V 0.05 -NFPP/C was revealed by ex-situ XRD patterns with the assistance of first-principles calculations, and the phase transformation mechanism during the sintering process was explored. [Display omitted] • Core-shelled Na 3.95 Fe 2.95 V 0.05 (PO 4) 2 P 2 O 7 were synthesized via a straightforward spray-drying method. • Vanadium ions can effectively enhance the reaction kinetics performance of the NFPP. • The sodium-ion storage mechanism was revealed by ex-situ XRD patterns with the assistance of first-principles calculations. • The phase transformation mechanism demonstrates that vanadium ions can inhibit the formation of inactive NaFePO 4 phases. [ABSTRACT FROM AUTHOR]

TiO 2 /SiO x /carbon nanohybrid consisting of super-small sized TiO 2 and SiO x nanoparticles is in situ formed within the in situ formed carbon matrix using difunctional methacrylate monomers as solvent and carbon source. The relative composition of TiO 2 and SiO x is systematically tuned by varying the feeding mass ratio of the precursors (TEOS/TTIP) and HF etching treatment after the carbonization process. The super-small sized TiO 2 and SiO x nanoparticles are well intermixed with each other and homogeneously dispersed throughout the carbon matrix, where a good control over crystallinity, morphology, and microstructure of the nanohybrids is achieved. Synergistic effects are demonstrated from both TiO 2 and SiO x regarding the increased reversible capacity from the SiO x phase and maintenance of good cyclic stability by the TiO 2 component when being used in lithium-ion batteries. A good balance is achieved in terms of reversible capacity, capacity retention, and rate performance in the TiO 2 /SiO 2 /C nanohybrid prepared with the TEOS/TTIP mass ratio of 1.0. The reversible capacities are improved by around two times compared to the SiO x free sample with a good capacity retention of 78 %, which exhibits good rate capability at the current densities up to 3350 mA g−1 as well. TiO 2 /SiO x /C nanohybrids with super-small sized TiO 2 and SiO x nanoparticles well intermixed with each other and homogeneously dispersed in the carbon matrix are prepared, where a good balance is achieved in terms of reversible capacity, capacity retention, and rate capability with the TiO 2 /SiO 2 /C nanohybrid prepared with the TEOS/TTIP mass ratio of 1.0. Image 1 [ABSTRACT FROM AUTHOR]

Despite the promising high energy density, Li-rich layered oxides still suffer from capacity fade and voltage decay during prolonged cycling. Doping could be effective in addressing such problems, but current studies pay less attention on rhombohedral phases. To this end, Al incorporated Li 1.14 (Ni 0.136 Co 0.10 Al 0.03 Mn 0.544 )O 2 oxides are investigated. Rietveld refined X-ray diffraction and transmission electron microscope results, along with electrochemical analyses, prove the substitution of Al for Co as well as its influence mainly on rhombohedral components. With slight capacity decreases, Al doped cathodes attain superior cycling performances, presenting a capacity retention up to 94.7% as compared to 81.7% for the pristine ones after 100 cycles. Most importantly, the fatal voltage decay, is alleviated as well through the obstructed formation of spinel-like phases, which are confirmed by the ex-situ XRD and further estimated by Raman spectra. Additionally, interfaces of Al doped electrodes are also somewhat enhanced as indicated by the electrochemical impedance study. These results suggest a notable stabilization effects on host framework in Li-rich layered oxides through manipulations on rhombohedral phases. [ABSTRACT FROM AUTHOR]

SiO x owing to high reversible capacity and moderate volume expansion has been attracting a lot of attention as state-of-the-art anodes for the next generation of Li-ion batteries. However, poor cycling performance and poor rate capability, respectively associated with detrimental volume expansion and insulative amorphous SiO 2 , are still challenging issues which need to be addressed for the actual employment as anodes for Li-ion batteries. In this regard, here we design, synthesize, characterize and test carbon coated sheet-like SiO 1.1 nanocomposites formed by Si-nanodomains confined inside amorphous SiO 2 (nano-Si/ a -SiO 2 ). As a proof-of-concept, we achieve sheet-like SiO x nanocomposites via in-situ transformation of delaminated siloxene. In particular, self-prepared siloxene with oxygen-inserted Si 6 rings terminated with H and OH ligands is prepared by delamination of CaSi 2 in dilute HCl. Importantly, the resulting carbon coated nano-Si/ a -SiO 2 material shows enhanced reaction kinetics and structural stability leading to 946 mAh g −1 capacity at 0.15 A g −1 . Intriguingly, 38.0% (~360 mAh g −1 ) of the maximum capacity is maintained even at 7.5 A g −1 , corresponding to a remarkable less than 3 min charge/discharge time. Finally, the electrode shows merely 24% of volume expansion and minor cracks with capacity retention of 92% after 300 cycles at 7.5 A g −1 . [ABSTRACT FROM AUTHOR]

A series of LiMn x Fe y (V▯) 1-x-y PO 4 samples have been synthesized as cathode materials for lithium-ion batteries. The structure and electrochemical performance of the samples are investigated systematically. All the modified samples show improved performance compared to the pristine LiMnPO 4 . Moreover, the four LiMn x Fe y (V▯) 1-x-y PO 4 samples (x = 1/3, y = 1/3; x = 0.5, y = 0.2; x = 0.5, y = 0.3 and x = 0.5, y = 0.4) exhibit enhanced electrochemical properties than LiMn 0.5 Fe 0.5 PO 4 . Among them, LiMn 1/3 Fe 1/3 (V▯) 1/3 PO 4 delivers the highest initial capacity of 161 mAh·g −1 at 0.05C and still retains 143 mAh·g −1 after 50 cycles at 0.5C with capacity retention of 98.6%. In addition, the calcination temperature is important for V 3+ doping into the olivine structure, and our results clearly indicate that the sample calcined at 600 °C performs better electrochemical performance than that at 500 °C. [ABSTRACT FROM AUTHOR]

Migration of transition metal (TM) ions to tetrahedral sites plays a crucial role on structural transformation and electrochemical behaviors for Li-rich layered oxides. Here, incorporating small B 3+ in the tetrahedral interstice is employed to block the migration channel of TM ions and stabilize the crystal structure. Benefiting from their good structural stability, Li-rich layered materials with B-doped Li 1.198 Ni 0.129 Co 0.129 Mn 0.535 B 0.01 O 2 and Li 1.196 Ni 0.127 Co 0.127 Mn 0.529 B 0.02 O 2 , exhibit excellent cycling performance and voltage stability. After 51 cycles at 0.2 C, 1 mol.% boron incorporated sample can deliver 211 mAh g −1 with capacity retention of 89.9%, which is much higher than that of the undoped sample of 177 mAh g −1 with the retention of 79.2%. Moreover, the declined voltage per cycle decreases from 3.6885 mV to 2.7530 mV after 2 mol.% boron doping. XRD patterns after extended cycling verified the suppression of the structural transformation by the incorporation of boron. [ABSTRACT FROM AUTHOR]

Li-rich layered oxides with micro-sized primary particles usually exhibit higher pellet density and better cycling performance. However, it is often at the expense of high reversible capacity. Here, we reported a simple strategy through a new chemical lithiation with micro-sized spinel-precursors and Na 2 S 2 O 8 surface treatment to obtain micro-sized particles in the Li-rich Li 1.172 Ni 0.135 Co 0.135 Mn 0.539 O 2 oxide without compromising its discharge capacity (260 mAh/g at 0.1C). Benefited from its larger particles and lower specific surface area, the obtained micron Li-rich layered material manifests its higher pellet density (3.18 g/cm 3 ) and better cycling performance in comparison with the nano-sized Li-rich layered material. After 100 cycles at 0.1 C, it can still deliver a capacity of 192 mAh/g with retention of 74%, much higher than 167 mAh/g with retention of 67% of the nano-sized sample. Moreover, the micron Li-rich layered material also exhibits good rate performance with a capacity of 174 mAh/g at 2C benefited from the 3D Li + insertion/extraction channel of its surface spinel content. These results may provide a new insight on improving pellet density of high-performance Li-rich layered cathode materials. [ABSTRACT FROM AUTHOR]

LiMn 0.8 Fe 0.2 PO 4 is becoming one of the most promising cathode materials for lithium ion batteries. However, the capacity suffers from a loss during long-term cycling, which is directly associated with Mn dissolution due to the disproportionation reaction of Mn 3+ . Here, we report a chemical vapor deposition (CVD) approach to modify LiMn 0.8 Fe 0.2 PO 4 particles with carbon so as to minimize Mn dissolution from cathode. The deposited carbon layer not only protects LiMn 0.8 Fe 0.2 PO 4 cathode from electrolyte corrosion, but also enhances the electronic/ionic conductivity owing to its higher graphitize degree. As a consequence, the electrochemical performances have a significant improvement. The capacity retention achieves 96% after 450 cycles at 1 C at room temperature (25 °C). Even at elevated temperature (55 °C), the capacity retention also reaches at 97 % after 50 cycles at 1 C rate, which is much higher than that of untreated sample (89%). Hence, the cathode material based on LiMn 0.8 Fe 0.2 PO 4 encapsulated with durable carbon by CVD method represents a promising strategy for developing its long-term cycling performance through suppressing Manganese dissolution. [ABSTRACT FROM AUTHOR]

It is a great challenge to combine good cycling performance with high rate capability for LiMn 1–x M x PO 4 cathode materials owing to the Mn dissolution upon cycling and its low electronic/ionic conductivity. Here, we report a novel concentration-gradient structure of LiMn 0.8 Fe 0.2 PO 4 material constructed by solvothermal treatment. This material shows a linear increase of Mn concentration from the edge to the particle centre, but the inverse trend for Fe concentration, which leads to the formation of Mn-rich phase in bulk and Fe-rich phase at surface. The Fe-rich phase effectively suppresses the corrosion from the electrolyte that minimizes the Mn dissolution and also improves the electronic/ionic conductivity of the surface that decreases the cathode/electrolyte interface resistance. Consequently, this concentration-gradient material achieves superior capacity retention with 98% after 50 cycles at 1 °C even at elevated temperature, and also exhibits an excellent rate capability with the reversible capacity of 130 mA h g −1 at 5 °C rate. These results suggest that the concentration-gradient LiMn 0.8 Fe 0.2 PO 4 is an ideal type of cathode material for high performance Lithium ion batteries. [ABSTRACT FROM AUTHOR]

Redox flow battery (RFB) has been widely considered to be one of the most promising grid-scale energy-storage technology. The membrane, namely separator, serves as preventing the crossover of the positive and negative active species, while facilitating the transport of the supporting electrolyte ions, is crucial to achieve a high performance and a long-term stability for an RFB. Advances in RFBs require high-performance and low-cost membranes with high ion-selective transport for the application of large-scale energy storage. Two-dimensional (2D) materials have emerged as promising functional materials owing to their atomic-scale thickness and unique physical/chemical properties, which have great potential in the application of RFB membrane. Focusing on the recent state-of-the-art of 2D materials, in this mini review, various 2D materials applied in the membrane for RFB are briefly introduced. A perspective on the near-future developments of 2D materials in RFB membranes is presented. [ABSTRACT FROM AUTHOR]

A high-efficiency flame-retarding additive, (Ethoxy)pentafluorocyclotriphosphazene (N 3 P 3 F 5 OCH 2 CH 3 , PFPN), has been synthesized and explored as a safer protection additive for rechargeable lithium batteries. The flammability tests indicate that only the addition of 5 wt% PFPN can make the electrolyte be totally non-flammable. As far as we know, the PFPN additive is the most efficient one of any flame-retarding additive ever synthesized and reported in the literature. The charge–discharge results demonstrate that the PFPN additive shows a good electrochemical compatibility on the graphitic anode and LiCoO 2 cathode. Meanwhile, the incorporated PFPN additive can greatly improve the cyclic performance of LiCoO 2 electrode at a high cut-off voltage of 4.5 V, showing a prospective flame-retarding additive for the applications in high-voltage lithium ion batteries. [ABSTRACT FROM AUTHOR]

Since 5 V lithium ion batteries have attracted more and more attentions and are deemed to be an important tendency in the future, the matched design of the separators has also become a necessary and significant work. In this work, the lithium ionic conducting glass ceramic Li 1.5 Al 0.5 Ge 1.5 (PO 4 ) 3 -polypropylene (PP) based inorganic–organic composite separator (LAGP-PP) is prepared. Compared with the pristine PP separator, the LAGP-PP separator owns enhanced thermal stability and wettability. Meanwhile, the LAGP-PP separator shows higher ion conductivity than the traditional Al 2 O 3 coated PP separator due to the more facile lithium ion diffusion channels in the coating layer. The superior C-rate capacity and cyclability in the LiNi 0.5 Mn 1.5 O 4 based 5 V lithium ion batteries indicate that the LAGP-PP separator is a good alternative for the traditional inert inorganic ceramic coated polyolefin separators and is a kind of promising candidate separator for the high voltage lithium ion batteries. [ABSTRACT FROM AUTHOR]

Thiophene derivatives (THs) are examined as novel functional additives for improving the cycling performance of high-voltage LiCoO 2 . Our investigation reveals that 2,2′-Bithiophene (2TH) and 2,2′:5′,2′′-Terthiophene (3TH) can be electrochemically polymerize prior to the electrolyte solvent decomposition to form a protective layer of conducting polymer film on the cathode surface, which blocks off severe electrolyte decomposition at high voltages and, therefore, improves the cycling stability of high voltage LiCoO 2 cathode. After 100 cycles at a high cutoff voltage of 4.4 V, the discharge capacity retention is 50% in the base electrolyte, in contrast, the LiCoO 2 cathode cycled in the electrolyte containing 0.1 wt% 3TH displays a high capacity retention of 84.8% at 0.25 C rate. This work demonstrates that these thiophene derivatives have considerable potential as functional additives for the applications in high-voltage lithium-ion batteries. [ABSTRACT FROM AUTHOR]

Highlights: [•] The (1-x)LiMnPO4·LixTix(PO4)δ samples were synthesized through a solid-state method. [•] The content of Ti additive greatly affects the electrochemical performance of LiMnPO4. [•] The sample synthesized with 10% Ti exhibits the best electrochemical performance. [ABSTRACT FROM AUTHOR]

A series of (1−x)LiMnPO4·xLi3V2(PO4)3/C (x = 0, 0.1, 0.2, 0.3, 0.4, 0.5, 1) composites cathode materials are successfully synthesized by solid-state method. The structures and properties of the composites have been studied with X-ray diffraction (XRD), scanning electron microscopy (SEM), elemental mapping, high resolution transmission electron microscopy (HRTEM), energy dispersive spectroscopy (EDS) and electrochemical measurements. XRD results reveal that the composites comprise Li3V2(PO4)3 phase and LiMnPO4 phase with a small amount of LiVP2O7 impurity. The electrochemical measurement results show that the ratios of LiMnPO4 to Li3V2(PO4)3 are correlated with the electrochemical performances of the composite materials. Among these composites, the 0.6LiMnPO4·0.4Li3V2(PO4)3 exhibits the best electrochemical performance, it can deliver specific capacity of 154 mA h g−1 at 0.05 C charge–discharge rate. [ABSTRACT FROM AUTHOR]

Abstract: Despite recent worldwide research efforts, composite silicon-based anodes remain at the centre of debate in the field of lithium-ion batteries. Here, we demonstrated that successful development of composite silicon-based anodes requires the simultaneous consideration of two equally important features: fundamental and technological. The fundamental feature dictates that the in situ formed amorphous phase should remain in its amorphous state in order to achieve a long-lasting reversible electrode, while the technological feature implies that the complex active material–binder interactions have to be numerically evaluated in order to tailor the electrode properties in an appropriate way. Only the harmonic consideration of both aspects allows creation of a long-lasting reversible silicon electrode. Examples demonstrating these features are considered and lithium-ion batteries employing hybrid silicon-based electrodes are proposed. [Copyright &y& Elsevier]

Abstract: Several series of Li1±x Mn2−y O4±δ and Li1.05Al y Mn1.95−y O4±δ samples with different oxygen defect degree have been synthesized by controlling synthesis temperature and procedures. The cycle performance of spinel as cathode in lithium batteries has been correlated with oxygen deficiency. The structure change of spinel during charge has also been investigated with respect with oxygen deficiency. [Copyright &y& Elsevier]

Abstract: Li1+x Al y Mn2−x−y O4±δ spinel cathode materials for lithium-ion batteries have been prepared by two methods, a specific two-step and the conventional one-step solid-state calcination methods. Compared with the conventional method, the new two-step method can guarantee the oxygen stoichiometry in spinel samples as well as reduced surface area. These characters lead to the improvement in cycling performance of spinel cathode even at elevated temperature. Moreover, the increase in doping amount of Al into Mn-spinel contributes to smearing the oxygen deficiency at high calcination temperature (1000°C). The oxygen stoichiometric spinel samples exhibited greatly improved cycling performance. Further, Mn dissolution from spinel cathodes into the electrolyte was sufficiently suppressed even at elevated temperature of 60°C. This beneficial influence would be reflected more remarkably in the cycles of lithium-ion full cells (spinel/C). [Copyright &y& Elsevier]

Abstract: Cathode material LiFePO4 with an excellent rate capability has been successfully prepared by a simple solid state reaction method using LiCH3COO·2H2O, FeC2O4·2H2O and (NH4)2HPO4 as the starting materials. We have investigated the effects of the sintering temperature and mixing time of the starting materials on the physical properties and electrochemical performance of LiFePO4. It was found that the rate capability of LiFePO4 is mainly controlled by its specific surface area and it is an effective way to improve the rate capability of the sample by increasing its specific surface area. In the present study, our prepared LiFePO4 with a high specific surface area of 24.1m2 g−1 has an excellent rate capability and can deliver 115mAhg−1 of reversible capacity even at the 5C rate. Moreover, we have prepared lithium ion batteries based on LiFePO4 as the cathode material and MCMB as the anode material, which showed an excellent cycling performance. [Copyright &y& Elsevier]

Abstract: We have successfully prepared the layered structure LiNi0.35Co0.3−x Cr x Mn0.35O2 with various Cr contents by a co-precipitation method. Many measurement methods have been applied to characterize the physical and electrochemical properties of LiNi0.35Co0.3−x Cr x Mn0.35O2, such as XRD, SEM, BET and electrochemical test. SEM showed that the addition of Cr has obviously changed the morphologies of their particles and increased the size of grains. The specific surface area of LiNi0.35Co0.3−x Cr x Mn0.35O2 decreases lineally from 4.9m2 g−1 (x =0) to 1.8m2 g−1 (x =0.1) with the increasing of Cr contents. Moreover, we have found that the Cr doping can greatly improve the density of the powder, which is beneficial to solve the problem of lower electrode density for these layered LiNi0.35Co0.3−x Cr x Mn0.35O2 cathode materials. Electrochemical test indicated that the cycling performance of LiNi0.35Co0.3−x Cr x Mn0.35O2 can be significantly improved with the increasing of Cr contents, although the initial discharge capacity of the sample has a little decrease. [Copyright &y& Elsevier]

Abstract: The solid solutions LiCoO2–LiNi1/2Mn1/2O2–Li2MnO3 with higher Mn content have been prepared by a spray drying method between 750 and 950°C and their electrochemical performances have also been characterized. The effects of the Li content on the structure and electrochemical performance of the samples have been studied. It was found that their lattice parameters a, c and V increase with the increase in Ni content and the decrease in Co content. The solid solutions xLiCoO2–yLiNi1/2Mn1/2O2–(1−x−y)Li2MnO3 with x =0.18, 0.27 and y =0.2 have the largest discharge capacity, which is more than 200mAh/g in the voltages of 3.0–4.6V. It is believed that the optimum Co content x in xLiCoO2–yLiNi1/2Mn1/2O2–(1−x−y)Li2MnO3 is between 0.2 and 0.3 in the charge–discharge voltage range of 3.0–4.6V. The solid solutions xLiCoO2–yLiNi1/2Mn1/2O2–(1−x−y)Li2MnO3 with x =0.18–0.36 and y =0.2 have the excellent cycling performance and the capacity retention attains to almost 100% after 50 cycles. Moreover, it is found that the discharge capacity gradually increases with the increment of cycle number especially in the initial 10 cycles. XRD showed that the layered structure has been kept all the time in 20 cycles, which is perhaps the reason why the sample has the excellent cycling performance. [Copyright &y& Elsevier]

Blending different cathode materials to construct composites can be in compatibility with their individual advantages to exhibit better electrochemical performances. In this study, we blend Li-rich and classical layered cathode materials to realize the suppression of voltage decay. The electrochemical results indicate that the composite electrodes show better capacity retention exceeding 90% after 100 cycles. More importantly, the cumulative voltage decay of the composite materials with different ratio are 280 mV and 140 mV for 100 cycles' duration, which are much lower than that of the single component with 390 mV in Li-rich layered cathode, respectively. Based on the ex situ X-ray diffraction, the blended composites show the structural origin of synergy effect, which are like a pair of parallel resistors to reciprocally buffer the crystal structure change during the charge and discharge process between Li-rich and classical layered cathode materials. Blending of layered cathode oxide materials with the synergy effect provide a possible approach to achieve more excellent electrochemical performances in lithium-ion batteries. [ABSTRACT FROM AUTHOR]

Abstract Li-rich layered oxides are highlighted as promising candidates for the next-generation cathode materials in Li-ion batteries, but suffer from poor cycling stability and voltage fading during the cycling process. Currently, less efforts are devoted to addressing these issues through exploring novel binders. In this work, we explore an aqueous binder of xanthan gum with double helix superstructure containing abundant charged functional groups. This unique structure is beneficial to the occurrence of significant mechanical interlocking effect and formation of chemical bond with particles' surface, which can effectively suppress electrode exfoliation, particle pulverization and structural degradation during cycling. As a consequence, the electrode with xanthan gum still delivers the discharge capacity of 275.6 mAh g−1 with the retention of 98.4% after 200 cycles at 0.1C rate. Accordingly, the mid-point discharge voltage remains 87% (about 2.3 mV/per cycle drop). The current study provides a useful insight into how to design and develop superior binders based on charged double-helix superstructure for potential low-cost and environmentally friendly aqueous processing of high energy density Li-ion batteries. Graphical abstract Image 1 Highlights • Aqueous binder (xanthan gum) is used in high energy density cathode materials. • It can show significant mechanical interlocking effect and chemical bonding force. • It can effectively suppress electrode exfoliation and structural degradation. • It can significantly improve cycling performance and suppress voltage decay. [ABSTRACT FROM AUTHOR]

Abstract Silicon (Si) is regarded as one of the most promising lithium-ion battery anodes to replace commercial graphite due to its exceptional theoretical capacity, appropriate voltage profile, environmental friendliness and natural abundance. It is crucial to develop effective strategies to improve the cyclic performance of the Si anodes. A new concept to synthesize Si/carbon composite with three dimensional (3D) hierarchical macro-/mesoporous structure is reported. Stöber silica (SiO 2) particles are used as templating agent and precursor for Si simultaneously. Unlike conventional work reported previously, here the silica particles are composited with carbon matrix before magnesiothermic reduction. Difunctional methacrylate monomers are used as solvent and carbon source coupled with a fast, environmental friendly and energy saving photo polymerization to prepare the SiO 2 /C composite. Based on a self-templating mechanism during the magnesiothermic reduction process, 3D hierarchical macro-/mesoporous Si is formed in situ within the carbon matrix. Compared to the Si/carbon composite composed of micro-sized Si and bare macro-/mesoporous Si, the cyclic performance is significantly improved with a reasonable mass loading density. Good rate performance is exhibited comparable to the bare porous Si. The hierarchical macro-/mesoporous structure within the carbon matrix helps to retain the porous Si structure, which effectively improves the electrochemical performance. Graphical abstract Self-templating synthesis of Si/C lithium-ion battery anode with 3D hierarchical macro-/mesoporous Si network encapsulated within the carbon matrix is achieved via a magnesiothermic reduction of SiO 2 /carbon composite, whose cyclic performance is significantly improved compared to the bare porous Si and Si/C composite with micrometer sized Si particles. Image 1 Highlights • Si/carbon was fabricated by magnesiothermic reduction of the silica/carbon composite. • Macro-/mesoporous silicon was encapsulated by carbon via a self-templating process. • Improved cyclic stability and rate performance was exhibited due to unique structure. [ABSTRACT FROM AUTHOR]

Rutile titanium dioxide (TiO 2) is regarded as one of the most promising electrode candidates for various rechargeable ion batteries applied in large-scale energy storage systems (ESSs) and electronic vehicles (EVs) due to its great cycling stability, high safety, and natural abundance. However, its poor electronic and ionic conductivities are the biggest obstacles on the way towards practical applications. In the past decades, four mainstream optimizing strategies were proposed to alleviate this issue, including constructing nanostructures, compositing with highly conductive materials, creating dual-phase interfaces, and introducing defects. Based on these strategies, a large number of rutile TiO 2 -based electrode materials were developed and gained good electrochemical performance for various rechargeable ion batteries. In this review, we retrospect the development pathway of TiO 2 -based electrode materials from the theoretical studies at the very beginning to today's prosperity in material diversity. With a unique chronological perspective, the general and detailed evolution trends of rutile TiO 2 electrode materials with different optimizing strategies are summarized. It is expected that this review can provide not only a complete overview of the development history of rutile TiO 2 electrode materials but also a spotlight for the future trends of this promising electrode material towards practical applications. [Display omitted] • A discussion of rutile TiO 2 electrode materials in rechargeable ion batteries with a chronological perspective is presented. • The development of rutile TiO 2 -based electrode materials from theoretical studies to material diversity are retrospected. • The mainstream optimizing strategies for rutile TiO 2 electrode materials are also discussed elaborately. [ABSTRACT FROM AUTHOR]

Abstract: Spherical LiNi0.5Mn1.5O4 material with a core–shell structure is synthesized by a urea-assisted hydrothermal method followed by heat treatment with LiOH at high temperature. After the process of hydrothermal treatment, the carbonate precursor with a concentration gradient is produced, in a single spherical particle, the content of Ni in the surface is higher than that in the center while Mn has a reversal trend. LiNi0.5Mn1.5O4 synthesized through the hydrothermal route has a great improvement in cycling stability at elevated temperature and rate capability. The capacity retention can maintain at 95% after 30 cycles at 55 °C. Furthermore, it can deliver a discharge capacity of 118 mAh g−1 at a high rate of 10 C at room temperature. Such excellent electrochemical properties of LiNi0.5Mn1.5O4 can be ascribed to its unique core–shell structure and nano-size particle. [Copyright &y& Elsevier]

Abstract: The Fe-doping LiMnPO4 (LiMn1−x Fe x PO4, x ≤ 0.5) nanomaterials are solvothermally synthesized in a mixed solvent of water and polyethylene glycol (PEG). The particle morphology can be controlled simply by adjusting the pH values of precursor suspensions. Electrochemical test shows that LiMn0.9Fe0.1PO4 nanoplates with a thickness of 20–30 nm could deliver the largest discharge capacity, which is attributed to the fast Li+ diffusion in the diffusion path of [010] crystallographic axis along the short radial direction of the nanoplates. It is demonstrated that Fe doping could significantly increase the initial reversible capacity, cycle performance and rate capability. The first discharge capacities of Fe-doped LiMnPO4 are all above 150 mAh g−1 at the discharge rate of 0.05 C. Especially, LiMn0.5Fe0.5PO4 delivers 100% capacity retention with the reversible capacity of 147 mAh g−1 at the discharge rate of 1 C, and losses only about 23.4% capacity with the discharge rate varying from 0.1 C to 5 C. The variation of energy density predicts that LiMn0.5Fe0.5PO4 shows the potential application for high-power devices. [Copyright &y& Elsevier]

Abstract: The Li1.2−x Na x Ni0.13Co0.13Mn0.54O2 (0≤ x ≤0.1) cathode materials have been synthesized by a solid-state reaction method. The effects of the Na+ contents on the structure, surface components and electrochemical performance are studied by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and electrochemical techniques. The XRD data indicate that the Li1.2−x Na x Ni0.13Co0.13Mn0.54O2 samples evolve from a sole layered structure (0≤ x ≤0.02) to a mixture of Na+-contained layered structure (0.02< x ≤0.1), which would transform into the single layered structure after the initial charge and discharge process. XPS data demonstrate that some of the Na+ ions could be reversibly de-/re-intercalated for the Li1.2−x Na x Ni0.13Co0.13Mn0.54O2 materials. An electrochemical test reveals that a small amount of Na+ (x ≤0.02) in the Li1.2−x Na x Ni0.13Co0.13Mn0.54O2 materials can significantly increase the rate capacity, yet the capacity retention becomes worse. We also find that the capacity retention increases with the Na+ contents. [Copyright &y& Elsevier]

Abstract: In this work, layered lithium-excess materials Li1+x Ni0.5Mn0.3Co0.2O2+δ (x =0, 0.05, 0.10 and 0.15), of spherical morphology with primary nanoparticles assembled in secondary microspheres, were synthesized by a coprecipitation method. The effects of lithium content on the structure and electrochemical performance of these materials were evaluated by employing X-ray diffraction (XRD), inductive coupled plasma (ICP), scanning electron microscopy (SEM), electrochemical impedance spectroscopy (EIS) and galvanostatic charge/discharge tests. It is found that Li1.10Ni0.5Mn0.3Co0.2O2+δ , i.e., Li[(Ni0.5Mn0.3Co0.2)0.95Li0.05]O2 showed the best electrochemical performance due to the highly ordered layered structure, reduced cation mixing and the lowest charge transfer resistance. Li1.10Ni0.5Mn0.3Co0.2O2+δ delivered a discharge capacity of 145mAhg−1 at 125mAg−1 in the cut-off voltage of 2.5–4.3V, and had a capacity retention of 100% after 50 cycles at room temperature. [Copyright &y& Elsevier]

Abstract: In the paper, we have investigated the preparation and electrochemical performance of the solid solution Li2MnO3–LiCoO2 (or written as Li[Li x/3Co1−x Mn2x/3]O2). The chemical composition determined by ICP–AES indicates that the chemical formula of our prepared samples is very closely to that of the ideal Li2MnO3–LiCoO2 solid solution in chemical stoichiometry. It was found that the oxidation states of Co and Mn are +3 and +4, respectively by redox titration and X-ray photoelectron spectroscopy (XPS). XRD shows that most peaks of the samples prepared at 950°C could be simply indexed as a layered α-NaFeO2 structure (space group , no. 166) except some additional peaks between 21° and 25°, which is caused by the appearance of the superlattice structure. The monoclinic phase has been formed for Li[Li x/3Co1−x Mn2x/3]O2 (x =0.5) at 750°C, which is reversibly transformed into a hexagonal phase with the increasing of sintering temperature from 750 to 950°C. It is found that the charge capacity of the samples Li[Li x/3Co1−x Mn2x/3]O2 (0.5≤ x ≤0.7) increases and the discharge capacity has no obvious change with the increasing of the sintering temperature due to the appearance of a flat charge voltage plateau at 4.45V. Moreover, the discharge capacity of the samples gradually reduces with the increasing Li2MnO3 content. The sample has the excellent electrochemical cycling performance with the charge–end voltage of 4.5V. XRD patterns of the charged product indicate that the layered structure has been kept during the charge process, which may be the reason for its good cycling performance. [Copyright &y& Elsevier]

The stability of electrolyte at high voltage is important to the development of Li-ion battery that required by the high energy density and high security. However, the decomposition of commercial electrolyte at high voltage limits its practical application. Herein, we introduce a "localized concentrated high-concentration electrolyte" which indicates underlying prospect in high voltage batteries. The "localized concentrated high-concentration electrolyte" can be achieved by adding 1,1,1,3,3,3-hexafluoroisopropyl methyl ether into traditional dimethyl carbonate and fluoroethylene carbonate solvents. The electrolyte (3 mol L−1 LiPF 6 DMC/FEC/HFPM 6/1/3) exhibits excellent flame retardant, low viscosity, wide electrochemical window and superior wettability. The Li‖LiNi 0.5 Mn 1.5 O 4 and Li‖Li 1.144 Mn 0.544 Ni 0.136 Co 0.136 O 2 coin cells with this electrolyte display splendid discharge capacity of 122.2 mAh g−1 after 400 cycles and 221.0 mAh g−1 after 100 cycles at 0.5 C, respectively. While 100.1 mAh g−1 after 35 cycles and 194.8 mAh g−1 after 100 cycles are obtained in commercial electrolyte, respectively. Further analysis shows that stability of high voltage cathodes is mainly contributed to the fluoride protective layer. This method offers a novel pathway for high-concentration electrolyte to improve the performance of Li-ion batteries. [ABSTRACT FROM AUTHOR]