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•A lithium ionic conductor, Li2ZrO3, is coated on LiNi0.8Co0.1Mn0.1O2.•The coating process is carried on the precursor which is more close the practical production.•Cycling ...performance and rate capability of LiNi0.8Co0.1Mn0.1O2 has been improved by Li2ZrO3 coating.•The mechanism of modification is explored by various means of characterization.
Li2ZrO3 with three dimensional tunnels for Li+ diffusion is introduced to improve the electrochemical performance of LiNi0.8Co0.1Mn0.1O2. The coating process is carried on the precursor rather than on the product. The Li2ZrO3 coating layer with thickness of 10nm has been detected by morphological observation. Electrochemical tests indicate that the Li2ZrO3-coating samples display better electrochemical performance than the bare sample. Especially, the 2% Li2ZrO3 coated sample delivers desirable capacity retention of 94.5% after 200 cycles at 1C, which is superior to the bare one (82.5%). Furthermore, the 1% Li2ZrO3 coated sample exhibits superior specific capacity of 144.3mAhg−1 at 10C, much greater than the bare sample (107.4mAhg−1). The cyclic voltammograms and electrochemical impedance spectra tests demonstrate that the Li2ZrO3-coated layer can cut down the electrochemical polarization of the materials and decrease the charge-transfer resistance in the cycling process. The XRD patterns and SEM images of the electrodes before and after 200 cycles reveal the Li2ZrO3-coated samples have more stable structure during cycling.
Ether electrolytes exhibit better rate kinetics than carbonate ester electrolytes when used in several kinds of anode materials, especially in hard carbon (HC) for sodium‐ion batteries (SIBs). ...However, the mechanism causing the remarkable kinetics difference is still unclear. Here, a three‐electrode system is used first to eliminate the influence of polarization from the Na counter electrode. Then, there is systematic exploration from three steps of the electrode reaction process (Na+ storage in HC; de‐solvation; Na+ migration through solid electrolyte interphase (SE), and the underlying mysteries are uncovered. For Na+ storage in the bulk of the HC, it is found that two systems show the same storage mechanism and Na metallic nanoparticles will appear when discharged to 0.1 V. In addition, faster de‐solvation of the ether electrolyte is uncovered by three‐electrode temperature‐dependent EIS and solvation free energies calculation. Moreover, the difference of the SEI layers is unraveled by X‐ray photoelectron spectroscopy etching, scanning electron microscopy, and differential electrochemical mass spectrometry. Most importantly, by discriminating the impacts of the SEI layers and de‐solvation behavior, it can be concluded that the de‐solvation process is the rate‐controlling step of the electrode reaction process and is the main factor causing the kinetics differences between the two electrolytes. The research provides a clear mechanism to illuminate fast kinetics for ether electrolytes, which will promote its application in SIBs.
Hard carbon electrodes show the same Na+ ion storage mechanism in two electrolytes. Ether electrolytes are favorable for a faster de‐solvation process. Solid electrolyte interphase (SEI) layers with more inorganic component and uniform morphology also favor faster Na+ ion transport for ether electrolytes. The de‐solvation behavior has a more profound effect than the SEI layers and is the main factor inducing the difference in kinetics.
The effect of water washing on LiNi0.8Co0.1Mn0.1O2 cathode is extensively studied with respect to the electrochemical properties, structural stabilities, and storage characteristics. Water washing ...can improve the cycling performance and structural stability of LiNi0.8Co0.1Mn0.1O2 material in electrolyte, although with a slight deleterious effect on the capacity. Storage tests of the 4.3 V charged electrodes at 90 °C after 30 days show that Ni, Co, Mn in fresh and washed samples are dissolved in electrolyte, but the amount of dissolved Ni4+ ions after washing decreases by 31.5% compared with the fresh cathode. Moreover, the fresh sample transforms into the spinel phase with a Fd3m space group, whereas the washed sample remains as a layered hexagonal phase with an Rm3¯ space group. FTIR spectroscopy, transmission electron microscope (TEM), X-ray diffraction (XRD) and electrochemical studies indicate that the washed materials become more easily attached upon exposure to air, accompanied by significant increase in cationic disorder and NiO-like cubic phase near surface.
Water washing can improve the cycling performance and structural stability of LiNi0.8Co0.1Mn0.1O2 material in electrolyte, although with a slight deleterious effect on the capacity. Moreover, the fresh sample transformed into the spinel phase with a Fd3m space group, whereas the washed sample remained as a layered hexagonal phase with an R3¯m space group when storing in electrolyte at 90 °C for 7 days at charged state. However, the washed materials became more easily attached upon exposure to air, accompanied by significantly increased cationic disorder and NiO-like cubic phase near surface. Display omitted
► The effect of water washing on fresh LiNi0.8Co0.1Mn0.1O2 cathode was firstly studied. ► Water washing improved the cycling performance and structural stability of material. ► Water washing resulted in a slight deleterious effect on the capacity. ► Water washing made material much less resistant to H2O and CO2 when storing in air.
Mixed transition metal oxides with hierarchical, porous structures, constructed from interconnected nano-building blocks, are considered promising positive electrodes for high-performance hybrid ...supercapacitors. Here we report our findings in design, fabrication, and characterization of 3D hierarchical, porous quaternary zinc-nickel-aluminum-cobalt oxide (ZNACO) architectures assembled from well-aligned nanosheets grown directly on nickel foam using a facile and scalable chemical bath deposition process followed by calcination. When tested as a binder-free electrode in a 3-electrode configuration, the ZNACO display high specific capacity (839.2Cg−1 at 1Ag−1) and outstanding rate capability (~82% capacity retention from 1Ag−1 to 20Ag−1), superior to those of binary-component NiCo2O4 and ZnCo2O4 as well as single-component Co3O4 electrode. More remarkably, a hybrid supercapacitor consisting of an as-fabricated ZNACO positive electrode and an activated carbon negative electrode exhibits a high energy density of 72.4Whkg−1 at a power density of 533Wkg−1 while maintaining excellent cycling stability (~90% capacitance retention after 10,000 cycles at 10Ag−1), demonstrating a promising potential for development of high-performance hybrid supercapacitors. Further, the unique electrode architecture is also applicable to other electrochemical systems such as batteries, fuel cells, and membrane reactors.
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•3D hierarchical porous Zn-Ni-Al-Co oxide (ZNACO) nanosheets grown directly on Ni foam is constructed for the first time.•The resultant binder-free electrodes manifest outstanding electrochemical performances with high capacity, excellent rate capability and cycling stability.•The synergetic contribution and advantageously structural features contribute to outstanding capacitive performance.•The assembled ZNACO//AC hybrid supercapacitor achieved a remarkable energy density of 72.4Whkg−1 at a power density of 533Wkg−1.
The degradation of Ni-rich LiNi0.8Co0.15Al0.05O2 cathode material is successfully suppressed via a facile in situ oxidizing-coating method. KMnO4 is used as not only a Mn source but also an oxidant. ...X-ray diffraction (XRD) and scanning electron microscope (SEM) results demonstrate that the structure and morphology of the KMnO4-pretreated sample are the same as the pristine one. X-ray photoelectron spectroscopy (XPS) confirms that the valence state of Mn is +4 and the Ni3+ ions are partly reduced to Ni2+ when the material is doped with Mn4+. Besides, the Mn4+ ions are proved to distribute uniformly on the surface of the materials particles through energy dispersive spectrometer (EDS) and EDS elemental mapping. And it is confirmed that the concentration of Ni in the outer layer is reduced by the Mn-surface-modification. From the electrochemical characterizations, it is confirmed that the presence of tetravalent Mn at the surface can suppress the capacity fading during charge–discharge cycles, even under elevated temperature and overcharge conditions, and can prevent the material from deterioration during storage in air.
•Mn is uniformly doped at the surface of LiNi0.8Co0.15Al0.05O2 particles.•The capacity fading under room temperature and high temperature is suppressed.•The capacity fading under overcharge condition is suppressed.•The degradation during storage in air is delayed.
Novel three-dimensional (3D) hierarchical Co3O4/CuO nanowire (NW) arrays on nickel foam composed of CuO NW stems and Co3O4 nanosheet branches are synthesized by combining a facile, scalable, and ...cost-effective thermal oxidation method with a simple but powerful chemical bath deposition followed by a calcination process. These arrays are further investigated as binder- and conductive-agent-free anodes for lithium-ion batteries (LIBs). The smart hybridization of CuO NWs and Co3O4 nanosheets into hierarchical core/shell array configuration results in remarkably enhanced electrochemical performances with good cycle performance, high reversible capacity, and excellent rate capability compared with pure CuO NW and single net-like Co3O4 nanosheets. A high reversible capacity of 1191mAhg−1 with 90.9% capacity retention after 200 cycles at a current density of 200mAg−1, and reversible capacity up to 810mAhg−1 even after 500 cycles at a current density as high as 1000mAg−1 can be maintained. The superior electrochemical performances of electrodes composed of hierarchical Co3O4/CuO NW arrays connected directly on nickel foam make them potential anode materials for high-performance LIBs.
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•Electron beam evaporation followed by oxidation to prepare CuO NWs on Ni foam.•Novel chemical bath deposition of Co3O4 to form 3D CuO/Co3O4 core/shell NW arrays.•Excellent cyclability, high capacity, and good rate capability as used in LIBs.•Synergetic effect of CuO NW core/Co3O4 shell results in remarkable performance.
To improve the stability of LiVPO4F electrode/electrolyte interface, Li3PO4 is used to modify LiVPO4F composite (P-LVPF) for the first time. Morphological characterization shows that LiVPO4F ...particles are wrapped by amorphous carbon and lithium ionic conductor Li3PO4 as the interlayer and outer layer, respectively. Compared to the pristine sample, the resultant P-LVPF exhibits greatly improved rate capability and elevated-temperature cycle performance when applied as the cathode material for lithium ion batteries. Specifically, the Li3PO4 modified sample specific capacity maintains 77.6% at 1 C after 100 cycles under 55 °C. Such improvement is attributed to the fact that the Li3PO4 coating layer not only acts as a good ionic conductor for LiVPO4F, but also serves as a physical barrier between electrode and electrolyte which can build a stable interface.
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•Li3PO4 coating builds stable LiVPO4F/electrolyte interface for the first time.•LiVPO4F coated with Li3PO4 shows enhanced cycle performance at 55 °C.•Li3PO4 is proposed to act as a physical barrier as well as a Li+ transfer media.
•Graphite/Silicon@Graphene is synthesized via spray drying and subsequent annealing.•Thermal reduction of graphene oxide was used to obtain graphene.•Graphite and silicon are wrapped by graphene to ...form a spherical structure.•Graphene acts as a carbon matrix to buffer volume effect of silicon particles.•A more stable conductivity network is maintained by graphene.
The Graphite/Silicon@reGO composite was synthesized via spray drying and subsequent annealing. According to XRD, Raman spectroscopy and FT-IR, graphene was demonstrated to be existed in the composite. Moreover, SEM and TEM were also used to illustrate the morphology of Graphite/Silicon@reGO. Used as anode for lithium-ion battery, it exhibited good cyclability with a high reversible charge capacity of 575.1mAhg−1 and showed a capacity retention ratio of 73.1% after 50 cycles at a current density of 50mAg−1. It also presented good rate capability at different rates of 50–1000mAg−1. EIS test showed that the composite electrode had a lower SEI resistance and charge-transfer resistance due to the existence of graphene.
This study first reports the synthesis of the nanosized LiVPO4F/graphene composite (LVPF/G). The LVPF/G composite is prepared by a facile mechanochemical approach. XRD results reveal that the ...prepared composite are well crystallized with triclinic LiVPO4F. SEM and TEM images demonstrate that the LiVPO4F nanoparticles in the composite are well enwrapped by graphene. Used as anode material for lithium ion batteries, the prepared LVPF/G composite exhibits greatly improved electrochemical performance. Furthermore, the electrochemical properties the LVPF/G composite depend heavily on the discharge cut-off potential. When the cut-off potential is altered to 0.01 V vs. Li/Li+, it possesses the best electrochemical performance. Under such optimal charge–discharge condition (3–0.01 V vs. Li/Li+), it shows an initial charge capacity of 287 mAh g−1 at 0.1C rate (1C = 310 mA g−1) and shows no capacity fading after 100 cycles. It also exhibits good rate capability, delivering about 168 mAh g−1 at 10C rate.
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•First synthesis of nanosized LiVPO4F/graphene (LVPF/G) composite.•First introduction of LVPF/G as anode material.•Altering the discharge cut-off potential to improve the performance of LVPF/G.•Superior cycle ability and rate capability delivered by LVPF/G at 3.0–0.01 V.
Herein, we report a series of O3-type Na(Ni
1/3
Mn
1/3
Fe
1/3
)
1-x
Al
x
O
2
(
x
= 0, 0.03, 0.05, 0.07) oxides as sodium-ion battery cathode materials synthesized via spray pyrolysis method. The ...structure, morphology, and electrochemical performance of Na(Ni
1/3
Mn
1/3
Fe
1/3
)
1-x
Al
x
O
2
(
x
= 0, 0.03, 0.05, 0.07) are characterized by XRD, SEM, CV, and galvanostatic charge and discharge tests, respectively. Na(Ni
1/3
Mn
1/3
Fe
1/3
)
0.95
Al
0.05
O
2
delivers an initial discharge capacity of 145.4 mAh g
−1
at 0.1 C and exhibits a favorable reversible capacity about 128.4 mAh g
−1
after 80 cycles at 0.2 C, with the capacity retention of 77.5% at the voltage range of 2.0 to 4.2 V. XPS analysis reveals that Al-doping could alleviate the Jahn-Teller effect caused by Mn
3+
and enhance the structural stability of layered oxides. The results confirm that a small quantity of (5 at. %) Al-doping improves the structural stability of the material, therefore leading to the excellent electrochemical performance.
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