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In order to develop functional energy storage device, it is necessary to improve the energy and power density. As a potential candidate that can synergistically harmonize energy and power density, lithium ion capacitor (LIC) has shown exciting promises in recent years. However, in the recent years, alternative metal has been explored to replace lithium in such metal-ion capacitor system. Hence, in this work we present zinc ion capacitor (ZIC) in which zinc acts as negative electrode and Metal Organic framework (MOF) derived carbon as positive electrode. The assembled ZIC was able to demonstrate exceptional power density of 85.5 kW kg-1 and a maximal energy density of 36.4 W h kg-1, together with 99 % capacitance retention after cycling for 20 000 cycles.

Defects can be generated when growing diamond on heterogeneous substrates. The problem dampers the widespread use of diamond films. In this paper, a novel approach is proposed which grows diamond on graphene quasi-homogeneous epitaxial substrate. Results showed that high quality diamond was synthesized on a quasi homoepitaxial graphene substrate through sp2-sp3 hybridization and covalent bond transformation. Firstly, D peak-free graphene was synthesized on nickel metal surface. C–H and C C bonds were then exploited to produce dehydrogenation and coupling reaction which caused the transform of graphene to transform into diamond. In virtue of the superior intermiscibility and catalysis of nickel to carbon, few-layer graphene grew efficiently on nickel foil surface. An internal space microstructure network of carbon atoms was produced through different non-covalent interactions. At last, graphene is converted into diamond. This process can also be used to synthesize hydrophilic porous diamond film. It is a promising approach to the development of new graphene/diamond-based components in the future.

Highlights High-voltage aqueous supercapacitors hold promise for commercial energy storage devices due to the excellent electrochemical performance.This review summarizes the efficacious measures on boosting the cell voltage of aqueous supercapacitors from the aspects of electrode, electrolyte, and asymmetric design., Due to its ultra-fast charge/discharge rate, long cyclic life span, and environmental benignity, aqueous supercapacitor (SC) is considered as a proper next-generation energy storage device. Unfortunately, limited by undesirable water electrolysis and unreasonable electrode potential range, aqueous SC normally generates a narrow cell voltage, resulting in a low energy density. To address such challenge, enormous efforts have been made to construct high-voltage aqueous SCs. Despite these achievements, the systematic reviews about this field are still rare. To fill this knowledge gap, this review summarizes the recent advances about boosting the cell voltage of aqueous SCs. From the viewpoint of electrode, doping alkali cations, modulating the electrode mass ratio, and optimizing the surface charge density are regarded as three effective pathways to achieve this goal. However, adjusting the appropriate pH level, introducing redox mediators, and constructing “water-in-salt” electrolyte are other three universal routes from the electrolyte aspect. Furthermore, it is also effective to obtain the high-voltage aqueous SCs through asymmetric design, such as designing asymmetric SCs. The confronting challenges and future development tendency towards the high-voltage aqueous SCs are further discussed.

High-efficiency alkaline seawater electrolysis is a promising strategy to promote the sustainability of wide-ranging hydrogen (H2) production, and the global goal of carbon neutrality. Searching for an ideal candidate with low cost and high electrocatalytic performance for both the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) is a major objective. Herein, we report delicate, heterostuctured NiTe-NiCoN and NiTe-NiFeN electrocatalysts constructed of nickel cobalt nitride and nickel iron nitride nanosheets uniformly anchored on NiTe nanorod arrays, respectively, which ensure outstanding HER and OER activity along with ultra-long-term stability. Impressively, the NiTe-NiCoN || NiTe-NiFeN couples in alkaline seawater solution delivered 500 mA cm−2 at a record low voltage of 1.84 V, and realized an industry-level performance via a solar-powered system and a wind-power system. Further comprehensive analysis has revealed that interface engineering strategy not only ensures that the surficial nitride exposes abundant active sites, but also induces electron modulation that optimizes the binding strength of absorption/desorption for the reaction intermediates to enhanced the the intrinsic activity, as well as facilitate faster electron-mass transfer. Notably, a high electric field intensity generated by the unique nanosheet-nanorod structure induces a local “hydroxide enrichment” environment that effectively promotes the OER kinetics, while inhibits the side effects of chlorine. This work shed lights on these novel heterostructured electrocatalysts with strong synergy, while demonstrating the key role of the unique nanostructures in high-efficiency seawater electrolysis.

Development of efficient and durable oxygen evolution reaction (OER) catalysts has a direct impact on the water splitting efficiency and cost effectiveness. In this work, we report the successful synthesis of a new Ni(OH)2 structure, strain-stabilized Ni(OH)2 nanoribbons (NR-Ni(OH)2) two to three layers thick, with widths of 2–5 nm, via an electro-oxidation route. Conventional Ni(OH)2 usually has negligible OER activity, while NR-Ni(OH)2 shows high activity for the oxygen evolution reaction and an overpotential of 162 millivolts and furthermore exhibits long-term stability in alkaline electrolyte. The substantial reduction in the overpotential of NR-Ni(OH)2 is due to its easier OOH* adsorption by the active four-coordinated Ni edge sites. The enhanced catalytic activity of NR-Ni(OH)2 makes it an excellent candidate for industrial applications.

Target tracking based on Siamese network has reached the state-of-the-art performance. However is still limited in semantic feature extraction. In this paper, we propose a novel method to distinguish positive and negative samples. Taking deep neural network as the backbone, we fuse the feature maps from different layers and feed it to RPN (Region Proposal Network). In addition, we use a loss term for loss function to achieve self-adjusting and learn more discriminative embedding features of target objects with similar semantics. In the tracking stage, one-shot detection is used as the reference, fix the first frame as the weight of tracking to track the subsequent frames. Our method has achieved outstanding performance on several benchmark data set, such as: OTB2015, VOT2016, VOT2018, and VOT2019 et al.

Currently, object detectors based on CNN, such as RetinaNet, Faster-RCNN, CornerNet series, can achieve good performance, but have some common drawbacks, like large calculation cost, high model complexity and slow detection speed. In this paper, a new lightweight object detector is proposed, which adopted a density-based approach to merge the real boxes. To reduce calculation cost and improve detection speed, the tactic of multi-scale output is adopted to predict objects of different sizes with features of different scales. Furthermore, a new lightweight network model is proposed, which can show better performance in computation, FPS, and model complexity. Meanwhile, the separation of convolution is used to improve the basic convolution layer, which can achieve better results under the same number of filters. In the experiments, we verified the capability of our methods based on ablation experiment and model evaluation, which demonstrates the superiority of our method. Moreover, we have also conducted deep network and multichannel experiments on MS-COCO2014 datasets and achieved 20.9% mAP performance.

This paper aimed to reveal the damage mechanisms of sapphire by single grit scratch tests on C-plane, which would establish the basis of damage-free machining. The deformation and damage evolution experienced five stages with increasing cutting depth resulting from the combined effect of principle stresses and activated slip/twining systems. It was proved that subsurface and surface damages occur in ductile removal regime of sapphire, which were dominantly induced by high residual stress and the rhombohedral twinning on ( 10 1 ‾ 2 ) and ( 1 ‾ 102 ) , respectively. Three critical cutting depths for suppressing subsurface damage, surface damage and surface roughness were determined, respectively. These conclusions were also supported by the acoustic emission (AE) features both in time and frequency domains during scratching. This paper also undertook the theoretical study. An improved elastic stress field model has been established to understand the deformation and damage evolution in relation to cutting depth.

Realizing an efficient electron transfer process in the oxygen evolution reaction by modifying the electronic states around the Fermi level is crucial in developing high-performing and robust electrocatalysts

Uniform magnetic nanoparticle-loaded polymer nanospheres with different loading contents of manganese ferrite nanoparticles were successfully synthesized using a flexible emulsion process. The MnFe2O4-loaded polymer nanospheres displayed an excellent dispersibility in both water and phosphate buffer saline. The effect of loading ratio and size of MnFe2O4 nanoparticles within the nanospheres on the specific absorption rate (SAR) under an alternating magnetic field was investigated. Our results indicate that a large size (here 18 nm) and a low loading ratio are preferable for a high SAR. For a smaller particle size (6 nm), the low loading ratio did not result in an enhancement of the SAR value, while a very low SAR value is expected for 6 nm. In addition, the SAR of low-content MnFe2O4 (18 nm)-loaded polymer nanospheres in the agarose gel which is simulated for in vivo environment is the highest among the samples and does not change substantially in physiological environments. This differs largely from the behaviour of singly dispersed nanoparticles. Our results have paved the way for the design of MnFe2O4-loaded polymer nanospheres as magnetic hyperthermia agents for in vivo bio-applications.

Achieving a functional and durable non-platinum group metal-based methanol oxidation catalyst is critical for a cost-effective direct methanol fuel cell. While Ni(OH)2 has been widely studied as methanol oxidation catalyst, the initial process of oxidizing Ni(OH)2 to NiOOH requires a high potential of 1.35 V vs. RHE. Such potential would be impractical since the theoretical potential of the cathodic oxygen reduction reaction is at 1.23 V. Here we show that a four-coordinated nickel atom is able to form charge-transfer orbitals through delocalization of electrons near the Fermi energy level. As such, our previously reported periodically arranged four-six-coordinated nickel hydroxide nanoribbon structure (NR-Ni(OH)2) is able to show remarkable methanol oxidation activity with an onset potential of 0.55 V vs. RHE and suggests the operability in direct methanol fuel cell configuration. Thus, this strategy offers a gateway towards the development of high performance and durable non-platinum direct methanol fuel cell., Development of suitable methanol oxidation reaction catalysts for direct methanol fuel cells is challenging due to sluggish kinetics. Herein, authors show that four-coordinate nickel atoms form charge-transfer orbitals near the Fermi energy level, leading to remarkable methanol oxidation activity.

This paper investigates the effect of cutting tool geometries on the initiation of ductile-brittle transition (DBT) of monocrystalline sapphire with a series of single-grit scratching tests. According to the method of single factor experiment, four typical geometrical parameters, namely rake angle, apex angle, opening angle, and truncated section, were evaluated in 7 scratching tests. The scratching force, groove topography and critical cutting depth for DBT (DBdc) have been measured by a dynamometer, SEM, and AFM, respectively. Furthermore, a new theoretical model of DBdc with respect to the rake and apex angle is established. The predicted DBdc agrees well with experimental results. The mechanism of the initiation of DBT is further investigated by the coupled SPH-FEM simulation. The research results reveal that all of the four geometrical parameters are the dominant factors with significant impact on the initiation of DBT of sapphire. Without exceeding the critical value, an increase in the negative rake angle contributes to an increased DBdc. The apex angle and opening angle are proved to adversely affect the DBdc and give rise to DBT at a smaller cutting depth, though the mechanisms associated with these two parameters are different. The parameter of the truncated section also has a significant effect where the DBdc decreases abruptly and severe brittle fracture is present with an increasing dimension of the truncated section.

Utilizing graphene-based hybrid papers or films as multifunctional electrodes has become the focus of clean energy devices due to the beneficial combination of their excellent electrical properties and multiple functions. However, limited attention has been paid to such hybrid papers with both outstanding mechanical and electrochemical properties. Recently, we fabricate rationally designed TiO2-B nanofibrils reinforced graphene paper, which can achieve high mechanical strength (88.5 MPa) without sacrificing their electrochemical properties. They further deliver capacities of 231 mAh g−1 (408.9 mAh cm−3) for Li-ion electrode and 201 mAh g−1 (355.8 mAh cm−3) for Na-ion electrode respectively at the same current density of 33.5 mA g−1. The outstanding mechanical stability of as-prepared hybrid electrode is demonstrated with a prototype of a bendable Li-ion capacitor. Besides, the as-prepared electrodes also reveal great potential to serve as light weight and ultrathin electromagnetic interference shielding materials. Single layer of hybrid paper exhibits a shielding effectiveness of over 10 dB (corresponding ∼90% shielding). These results prove that TiO2-B nanofibrils reinforced graphene paper can serve as a multifunctional flexible electrode for diverse applications. Moreover, this work also demonstrates a novel strategy on how to enhance mechanical properties for those flexible electrodes.

Supramolecular polymers formed through host–guest complexation have inspired many interesting developments of functional materials for biological and biomedical applications. Here, we report a novel design of a non-viral gene delivery system composed of a cationic star polymer forming supramolecular complexes with the surface oleyl groups of superparamagnetic iron oxide nanoparticles (SPIONs), for magnetically enhanced delivery of DNA into mammalian cells. The cationic star polymer was synthesized by grafting multiple oligoethylenimine (OEI) chains onto an α-cyclodextrin (α-CD) core. The SPIONs were synthesized from iron(III) acetylacetonate and stabilized by hydrophobic oleic acid and oleylamine in hexane, which were characterized in terms of their size, structure, morphology, and magnetic properties. The synthesized magnetic particles were found to be superparamagnetic, making them a suitable ferrofluid for biological applications. In order to change the hydrophobic surface of the SPIONs to a hydrophilic surface with functionalities for plasmid DNA (pDNA) binding and gene delivery, a non-traditional but simple supramolecular surface modification process was used. The α-CD-OEI cationic star polymer was dissolved in water and then mixed with the SPIONs stabilized in hexane. The SPIONs were “pulled” into the water phase through the formation of supramolecular host–guest inclusion complexes between the α-CD unit and the oleyl surface of the SPIONs, while the surface of the SPIONs was changed to OEI cationic polymers. The α-CD-OEI-SPION complex could effectively bind and condense pDNA to form α-CD-OEI-SPION/pDNA polyplex nanoparticles at the size of ca. 200 nm suitable for delivery of genes into cells through endocytosis. The cytotoxicity of the α-CD-OEI-SPION complex was also found to be lower than high-molecular-weight polyethylenimine, which was widely studied previously as a standard non-viral gene vector. When gene transfection was carried out in the presence of an external magnetic field, the α-CD-OEI-SPION/pDNA polyplex nanoparticles greatly increased the gene transfection efficiency by nearly tenfold. Therefore, the study has demonstrated a facile two-in-one method to make the SPIONs water-soluble as well as functionalized for enhanced magnetofection.

In-depth understanding of corrosion behaviour is a key aspect regarding the application of additively manufactured parts. In this study, 316L stainless steel was manufactured under different scanning strategies using selective laser melting (SLM). Microstructure characterization and electrochemical tests in NaCl aqueous solution (3.5 wt%), including open circuit potential (OCP), potentiodynamic polarization, and electrochemical impedance spectroscopy (EIS), were conducted to study the influence of scanning strategies on the corrosion behaviour. The microstructure and corrosion on different planes were characterized to reveal the influence of building direction. EBSD analysis shows that the scanning strategy affects the continuity of grain growth through adjacent layers and the growth of grains inside the melt track. Electrochemical tests indicate a clear difference in corrosion resistance perpendicular and parallel to building direction and with different scanning strategies. Pitting corrosion is the main form of corrosion in SLM 316L stainless steel and preferentially initiates on molten pool boundaries.

Aqueous Zn ion batteries (ZIBs) are promising in energy storage due to the low cost, high safety, and material abundance. The development of metal oxides as the cathode for ZIBs is limited by the strong electrostatic forces between O2− and Zn2+ which leads to poor cyclic stability. Herein, Bi2S3 is proposed as a promising cathode material for rechargeable aqueous ZIBs. Improved cyclic stability and fast diffusion of Zn2+ is observed. Also, the layered structure of Bi2S3 with the weak van der Waals interaction between layers offers paths for diffusion and occupancy of Zn2+. As a result, the Zn/Bi2S3 battery delivers high capacity of 161 mAh g−1 at 0.2 A g−1 and good cycling stability up to 100 cycles with ca. 100% retention. The battery also demonstrates good cyclic performance of ca. 80.3% over 2000 cycles at 1 A g−1. The storage mechanism in the Bi2S3 cathode is related to the reversible Zn ion intercalation/extraction reactions and the capacitive contribution. This work indicates that Bi2S3 shows great potential as the cathode of ZIBs with good performance and stability.

Highlights Bi2S3 is proposed as a promising cathode material for rechargeable aqueous Zn ion battery.The Zn/Bi2S3 battery shows a reversible capacity of 161 mAh g−1 at 0.2 A g−1 and good cyclic stability of up to 100 cycles with ca. 100% retention.The storage mechanism in the Bi2S3 cathode is related to the reversible Zn ion intercalation/extraction reactions and the capacitive contribution. Electronic supplementary material The online version of this article (10.1007/s40820-019-0352-3) contains supplementary material, which is available to authorized users., Aqueous Zn ion batteries (ZIBs) are promising in energy storage due to the low cost, high safety, and material abundance. The development of metal oxides as the cathode for ZIBs is limited by the strong electrostatic forces between O2− and Zn2+ which leads to poor cyclic stability. Herein, Bi2S3 is proposed as a promising cathode material for rechargeable aqueous ZIBs. Improved cyclic stability and fast diffusion of Zn2+ is observed. Also, the layered structure of Bi2S3 with the weak van der Waals interaction between layers offers paths for diffusion and occupancy of Zn2+. As a result, the Zn/Bi2S3 battery delivers high capacity of 161 mAh g−1 at 0.2 A g−1 and good cycling stability up to 100 cycles with ca. 100% retention. The battery also demonstrates good cyclic performance of ca. 80.3% over 2000 cycles at 1 A g−1. The storage mechanism in the Bi2S3 cathode is related to the reversible Zn ion intercalation/extraction reactions and the capacitive contribution. This work indicates that Bi2S3 shows great potential as the cathode of ZIBs with good performance and stability. Electronic supplementary material The online version of this article (10.1007/s40820-019-0352-3) contains supplementary material, which is available to authorized users.

Transition metal oxides exhibit strong structure-property correlations, which has been extensively investigated and utilized for achieving efficient oxygen electrocatalysts. However, high-performance oxide-based electrocatalysts for hydrogen evolution are quite limited, and the mechanism still remains elusive. Here we demonstrate the strong correlations between the electronic structure and hydrogen electrocatalytic activity within a single oxide system Ti2O3. Taking advantage of the epitaxial stabilization, the polymorphism of Ti2O3 is extended by stabilizing bulk-absent polymorphs in the film-form. Electronic reconstructions are realized in the bulk-absent Ti2O3 polymorphs, which are further correlated to their electrocatalytic activity. We identify that smaller charge-transfer energy leads to a substantial enhancement in the electrocatalytic efficiency with stronger hybridization of Ti 3d and O 2p orbitals. Our study highlights the importance of the electronic structures on the hydrogen evolution activity of oxide electrocatalysts, and also provides a strategy to achieve efficient oxide-based hydrogen electrocatalysts by epitaxial stabilization of bulk-absent polymorphs., Converting solar energy to hydrogen fuel requires light-absorbers that well-match the wavelengths of incoming sunlight. Here, authors prepare a broadband visible-light-absorbing molecular complex that efficiently produces hydrogen from water.

Rechargeable aqueous zinc-ion batteries (ZIBs) have attracted considerable attention for large-scale energy storage systems due to their high energy density, low cost, and inherent safety. However, ZIBs suffer from limited cyclic stability with the use of the current cathode materials (such as V2O5) due to the strong electrostatic ion–lattice interactions with the diffusing divalent Zn2+, usually leading to a limited cyclic duration (

Balancing energy density and power density has been a critical challenge since the inception of supercapacitors. Introducing redox-active additives in the supporting electrolyte has been shown to increase the energy density, however the power density and cycling stability are severely hampered in the process. Herein, an extensively conjugated indole-based macromolecule consisting of 5,6-dihydroxyindole/5,6-quinoneindole motifs, prepared by electrochemical polymerization of dopamine under acidic conditions, was employed as a redox-active additive. By utilizing the conjugation effect, the HOMO–LUMO gap (HLG) of the extensively conjugated indole-based macromolecule was reduced to ca. 2.08 eV, which enhanced the electronic transfer kinetics, in turn improving the power density and reversibility of redox reactions. When coupled with a porous honeycomb-like carbon (PHC) electrode, the assembled supercapacitor delivered an excellent rate performance with a high specific capacitance of 205 F g−1 at 1000 A g−1. This work reports one of the highest power densities recorded at 153 kW kg−1 for redox-mediated electrolyte systems with a respectable energy density of 8.8 W h kg−1. In addition to an excellent cycling stability of 97.1% capacitance retention after 20 000 charge/discharge cycles, the conjugation degree has to be considered when engineering the redox-active electrolyte so as to improve the power density and stability.

Practical applications of high temperature superconductors may require them to be processed into complex geometries. In this work, slurry-based extrusion freeforming coupled with high temperature treatment was attempted for the fabrication of bulk YBa 2 Cu 3 O 7−x (YBCO) superconducting structures. YBCO parts with approximately 93% of the theoretical density were successfully fabricated after sintering at 940 °C for 60 h, with the obtained constituent phases strongly dependent on the heat treatment temperature and duration. A high critical transition temperature ( T C =92 K) and good magnetic levitation ability could be obtained after optimization of the heat treatment conditions. Overall, the experimental results demonstrate that extrusion freeforming is a feasible and effective technique for fabricating YBCO superconductors that have desirable configurations and good superconductivity properties.

Mn doped Ag–In–Zn–S nanoparticles (Mn:AgInZnS) were successfully synthesized by using a practical hot-injection method. The as-prepared Mn:AgInZnS nanoparticles were triangular shape with average radius of 6(±0.5) nm, and the composition of doped Mn was about 7.29 by wt.%. Moreover, the Mn:AgInZnS nanoparticles demonstrated strong and stable photoluminescence emission at about 620 nm, and the UV–vis absorption spectrum further revealed band gap absorption around 600 nm. Furthermore, the photoluminescence lifetime of Mn:AgInZnS nanoparticles was about 1.38 μs which indicated the tremendous potential applications in cell labelings, fluorescent imaging, solar cells and LEDs. Keywords: Mn:AgInZnS nanoparticles, Photoluminescence lifetime

Bendable freestanding films composed of reduced graphene oxide (RGO) and one dimensional conducting polymers (CPs) including polyaniline (PANI) and polypyrrole (PPy) are successfully fabricated by self-assembly assisted filtration method. The morphology and intrinsic properties of both components are well preserved and the desired synergetic effects are achieved. The intercalated one dimensional CPs act as not only pseudocapacitors to improve the overall capacitances but also an effective framework to open the penetrative channels for the electrolyte. The hybrid freestanding electrodes thus obtained exhibit superior performance in terms of gravimetric capacitance, volumetric capacitance and cycling stability. For example, at the current density of 0.2 A g−1, the RGO/PPy film electrode gives rise to a gravimetric capacitance of 374 F g−1 and a volumetric capacitance of 355 F cm−3; while the RGO/PANI film electrode yields a high gravimetric capacitance of 540 F g−1 and a volumetric capacitance of 616 F cm−3. Both RGO/PANI and RGO/PPy hybrid film electrodes deliver good cycling stabilities with ∼86% of original capacitances being retained after 5000 cycles.

Magnetic single-domain islands based on in-plane anisotropy (usually, shape anisotropy) and their dipole—dipole interactions have been investigated extensively in recent years. This has been driven by potential applications in magnetic recording, spintronics, magneto-biology, etc. Here, we propose a concept of outof-plane magnetic clusters with configurable domain structures (multi-flux states) via dipole—dipole interactions. Their flux stages can be switched through an external magnetic field. The concept has been successfully demonstrated by patterned [Co/Pd] islands. A [Co/Pd] multilayer exhibits a large perpendicular anisotropy, a strong physical separation, and uniform intrinsic properties after being patterned into individual islands by electron beam lithography. A threeisland cluster with six stable flux states has been realized by optimizing island size, thickness, gap, anisotropy, saturation magnetization, etc. Using [Co/Pd] multilayers, we have optimized the island structure by tuning magnetic properties (saturation magnetization and perpendicular anisotropy) using Landau—Liftshitz—Gilbert (LLG) simulation/calculation. Potential applications have been proposed, including a flexi-programmable logic device with AND, OR, NAND, and NOR functionalities and a magnetic domino, which can propagate magnetic current as far as 1 µm down from the surface via vertical dipole—dipole interactions.

Piezoelectric energy harvesters can be used to convert ambient energy into electrical energy and power small autonomous devices. In recent years, massive effort has been made to improve the energy harvesting ability in piezoelectric materials. In this study, reduced graphene oxide was added into poly(vinylidene fluoride) to fabricate the piezoelectric nanocomposite films. Open-circuit voltage and electrical power harvesting experiments showed remarkable enhancement in the piezoelectricity of the fabricated poly(vinylidene fluoride)/reduced graphene oxide nanocomposite, especially at an optimal reduced graphene oxide content of 0.05 wt%. Compared to pristine poly(vinylidene fluoride) films, the open-circuit voltage, the density of harvested power of alternating current, and direct current of the poly(vinylidene fluoride)/reduced graphene oxide nanocomposite films increased by 105%, 153%, and 233%, respectively, indicating a great potential for a broad range of applications.

Li-rich Li(Li0.2Mn0.54Ni0.13Co0.13)O2 cathode coated with carbon layer has been prepared by a hydrothermal approach followed by a post annealing process. The cathode after surface modification exhibits both enhanced cyclability and improved rate capability compared with the pristine one without coating. The carbon coating process causes a phase transformation from Li2MnO3-like domain to cubic-spinel domain with Fdm symmetry at surface regions of particles. As a consequence, the valence state of Mn on the surface accordingly varies. Such transformed surface spinels, as well as the wrapped carbon layers as a result of this coating strategy are believed to be responsible for the enhanced electrochemical performance.