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Research Article Issue
In-situ construction of a thermodynamically stabilized interface on the surface of single crystalline Ni-rich cathode materials via a one-step molten-salt route
Nano Research 2023, 16 (5): 6771-6779
Published: 20 August 2022
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Nickel rich LiNixCoyMn1−xyO2 cathode materials have been studied extensively to increase the energy density of lithium-ion batteries (LIBs) due to their advantages of high capacity and low cost. However, the anisotropic crystal expansion and contraction inside the secondary particles would cause detrimental micro-cracks and severe parasitic reactions at the electrode/electrolyte interface during cycling, which severely decreases the stability of crystalline structure and cathode-electrolyte interphase and ultimately affects the calendar life of batteries. Herein, a thermodynamically stabilized interface is constructed on the surface of single-crystalline Ni-rich cathode materials (SC811@RS) via a facile molten-salt route to suppress the generation of microcracks and interfacial parasitic side reactions simultaneously. Density functional theory calculations show that the formation energy of interface layer (−1.958 eV) is more negative than that of bulk layered structure (−1.421 eV). Such a thermodynamically stable protective layer can not only prevent the direct contact between highly reactive LiNixCoyMn1−xyO2 and electrolyte, but also mitigate deformation of structure caused by stress thus strengthening the mechanical properties. Raman spectra further confirm the excellent structural reversibility and reaction homogeneity of SC811@RS at particle, electrode, and time scales. Consequently, SC811@RS cathode material delivers significantly improved cycling stability (high capacity retention of 92% after 200 cycles at 0.5 C) compared with polycrystalline LiNi0.8Co0.1Mn0.1O2 (82%).

Research Article Issue
A homogenous solid polymer electrolyte prepared by facile spray drying method is used for room-temperature solid lithium metal batteries
Nano Research 2023, 16 (4): 5080-5086
Published: 13 July 2021
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The aggregation of inorganic particles with high mass ratio will form a heterogeneous electric field in the solid polymer electrolytes (SPEs), which is difficult to be compatible with lithium anode, leading to inadequate ionic conductivity. Herein, a facile spray drying method is adopted to increase the mass ratio of inorganic particles and solve the aggregation problems of fillers simultaneously. The polyvinylidene fluoride (PVDF) with lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) covers the surface of each Li6.4La3Zr1.4Ta0.6O12 (LLZTO) granules during the nebulization process, then forming flat solid electrolytes via layer-by-layer deposition. Characterized by the atomic force microscope, the obtained solid electrolytes achieve a homogenous dispersion of Young’s modulus and surface electric field. As a result, the as-prepared SPEs present high tensile strength of 7.1 MPa, high ionic conductivity of 1.86 × 10−4 S·cm−1 at room temperature, and wide electrochemical window up to 5.0 V, demonstrating increased mechanical strength and uniform lithium-ion migration channels for SPEs. Thanks to the as-prepared SPEs, the lithium-symmetrical cells show a highly stable Li plating/stripping cycling for over 1,000 h at 0.1 mA·cm−2. The corresponding Li/LCoO2 batteries also present good rate capability and excellent cyclic performance with capacity retention of 80% after 100 cycles at room temperature.

Research Article Issue
High-rate performance magnesium batteries achieved by direct growth of honeycomb-like V2O5 electrodes with rich oxygen vacancies
Nano Research 2023, 16 (4): 4880-4887
Published: 06 July 2021
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Rechargeable magnesium batteries (RMBs) have emerged as a promising next-generation electrochemical energy storage technology due to their superiority of low price and high safety. However, the practical applications of RMBs are severely limited by immature electrode materials. Especially, the high-rate cathode materials are highly desired. Herein, we propose a dual-functional design of V2O5 electrode with rational honeycomb-like structure and rich oxygen vacancies to enhance the kinetics synergistically. The result demonstrates that oxygen vacancies can not only boost the intrinsic electronic conductivity of V2O5, but also enhance the Mg2+ diffusion kinetics inside the cathode, leading to the good high-rate performance. Moreover, ex-situ X-ray diffraction (XRD), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS) characterizations reveal that Mg2+ is mainly intercalated from the (101) plane of V2O5−X based on the insertion-type electrochemical mechanism; meanwhile, the highly reversible structure evolution during Mg2+ insertion/extraction is also verified. This work proposes that the dual-functional design of electrode has a great influence in enhancing the electrochemical performance of cathode materials for RMBs.

Research Article Issue
NaV6O15: A promising cathode material for insertion/extraction of Mg2+ with excellent cycling performance
Nano Research 2020, 13 (2): 335-343
Published: 27 January 2020
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The rechargeable magnesium batteries (RMBs) are getting more and more attention because of their high-energy density, high-security and low-cost. Nevertheless, the high charge density of Mg2+ makes the diffusion of Mg2+ in the conventional cathodes very slow, resulting in a lack of appropriate electrode materials for RMBs. In this work, we enlarge the layer spacing of V2O5 by introducing Na+ in the crystal structure to promote the diffusion kinetics of Mg2+. The NaV6O15 (NVO) synthesized by a facile method is studied as a cathode material for RMBs with the anhydrous pure Mg2+ electrolyte. As a result, the NVO not only exhibits high discharge capacity (119.2 mAh·g-1 after 100 cycles at the current density of 20 mA·g-1) and working voltage (above 1.6 V vs. Mg2+/Mg), but also expresses good rate capability. Besides, the ex-situ characterizations results reveal that the Mg2+ storage mechanism in NVO is based on the intercalation and de-intercalation. The density functional theory (DFT) calculation results further indicate that Mg2+ tends to occupy the semi-occupied sites of Na+ in the NVO. Moreover, the galvanostatic intermittent titration technique (GITT) demonstrates that NVO electrode has the fast diffusion kinetics of Mg2+ during discharge process ranging from 7.55 × 10-13 to 2.41 × 10-11 cm2·s-1. Our work proves that the NVO is a potential cathode material for RMBs.

Research Article Issue
A stable artificial protective layer for high capacity dendrite-free lithium metal anode
Nano Research 2019, 12 (10): 2535-2542
Published: 01 August 2019
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The metallic lithium (Li) is considered as the most promising anode material for high-energy batteries. Nevertheless, the uncontrollable growth of Li dendrite and unstable electrolyte/electrode interface still hinder the development of Li-based battery. In this work, a novel strategy has been proposed to stabilize Li anode by in-situ polymerizing polypyrrole (PPy) layer on Ni foam (PPy@Ni foam) as an artificial protective layer. The PPy protective layer can effectively decrease the contact between Li metal and electrolyte during cycling. In addition, the morphology characterization shows that the PPy layer can help the even Li deposition underneath the layer, leading to a dendrite-free Li anode. As a result, when deposited 2 mAh·cm-2 Li metal, the PPy@Ni foam can keep stable Coulombic efficiency (99%) during nearly 250 cycles, much better than the pure Ni foam (100 cycles). Even in the case of the Li capacity of 10 mAh·cm-2, the stable cycling performance for 60 cycles can still be achieved. Furthermore, when assembled with LiFePO4 material as the cathode for a full cell, the PPy@Ni foam can keep high capacity retention of 85.5% at 500 cycles. In our work, we provide a simple and effective method to enhance the electrochemical performances of Li metal-based batteries, and reveal a new avenue to design three-dimensional (3D) metallic current collector for protecting the Li metal anode.

Research Article Issue
Self-templating thermolysis synthesis of Cu2–xS@M (M = C, TiO2, MoS2) hollow spheres and their application in rechargeable lithium batteries
Nano Research 2018, 11 (2): 831-844
Published: 19 July 2017
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Owing to their unique structural stability and impressive long-term cycling performance, coated hollow structures are highly attractive for energy storage systems, especially batteries. Many efforts have been devoted and various strategies have been proposed to prepare such materials. In the present work, we propose a self-templating thermolysis strategy, different from traditional wet processing methods, to fabricate cuprous sulfide hollow spheres coated with different shells, by exploiting the thermal decomposition properties of the core (CuS) and the protection provided by the shell. To demonstrate the generality of this synthetic approach, three different coating materials (carbon, TiO2, MoS2) have been chosen to prepare Cu2–xS@C, Cu2–xS@TiO2 and Cu2–xS@MoS2 hollow spheres. All synthesized composite materials were then assembled as electrodes and tested in lithium batteries, showing excellent cycling stability. In particular, the electrochemical properties of Cu2–xS@C were thoroughly investigated. The results of this work provide an alternative route to prepare coated metal sulfide hollow spheres for energy storage applications.

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