An Innovative Lithium Ion Battery System Based on a Cu2S Anode Material

Surface Structure to Tailor the Electrochemical Behavior of Mixed-Valence Copper Sulfides during Water Electrolysis

The semiconducting behavior of mixed-valence copper sulfides arises from the pronounced covalency of Cu-S bonds and the exchange coupling between CuI and CuII centers. Although electrocatalytic study with digenite Cu9S5 and covellite CuS has been performed earlier, detailed redox chemistry and its interpretation through lattice structure analysis have never been realized. Herein, nanostructured Cu9S5 and CuS are prepared and used as electrode materials to study their electrochemistry. Powder X-ray diffraction (PXRD) and microscopic studies have found the exposed surface of Cu9S5 to be d(0015) and d(002) for CuS. Tetrahedral (Td) CuII, distorted octahedral (Oh) CuII, and trigonal planar (Tp) CuI sites form the d(0015) surface of Cu9S5, while the (002) surface of CuS consists of only Td CuII. The distribution of CuI and CuII sites in the lattice, predicted by PXRD, can further be validated through core-level Cu 2p X-ray photoelectron spectroscopy (XPS). The difference in the electrochemical response of Cu9S5 and CuS arises predominantly from the different copper sites present in the exposed surfaces and their redox states. In situ Raman spectra recorded during cyclic voltammetric study indicates that Cu9S5 is more electrochemically labile compared to CuS and transforms rapidly to CuO/Cu2O. Contact-angle and BET analyses imply that a high-surface-energy and macroporous Cu9S5 surface favors the electrolyte diffusion, which leads to a pronounced redox response. Post-chronoamperometric (CA) characterizations identify the potential-dependent structural transformation of Cu9S5 and CuS to CuO/Cu2O/Cu(OH)2 electroactive species. The performance of the in situ formed copper-oxides towards electrocatalytic water-splitting is superior compared to the pristine copper sulfides. In this study, the redox chemistry of the Cu9S5/CuS has been correlated to the atomic arrangements and coordination geometry of the surface exposed sites. The structure-activity correlation provides in-depth knowledge of how to interpret the electrochemistry of metal sulfides and their in situ potential-driven surface/bulk transformation pathway to evolve the active phase.

Design of High-Capacity MoS3 Decorated Nitrogen Doped Carbon Coated Cu2 S Electrode Structures with Dual Heterogenous Interfaces for Outstanding Sodium-Ion Storage

The hierarchical Cu2 S@NC@MoS3 heterostructures have been firstly constructed by the high-capacity MoS3 and high-conductive N-doped carbon to co-decorate the Cu2 S hollow nanospheres. During the heterostructure, the middle N-doped carbon layer as the linker facilitates the uniform deposition of MoS3 and enhances the structural stability and electronic conductivity. The popular hollow/porous structures largely restrain the big volume changes of active materials. Due to the cooperative effect of three components, the new Cu2 S@NC@MoS3 heterostructures with dual heterogenous interfaces and small voltage hysteresis for sodium ion storage display a high charge capacity (545 mAh g-1 for 200 cycles at 0.5 A g-1 ), excellent rate capability (424 mAh g-1 at 15 A g-1 ) and ultra-long cyclic life (491 mAh g-1 for 2000 cycles at 3 A g-1 ). Except for the performance test, the reaction mechanism, kinetics analysis, and theoretical calculation have been performed to explain the reason of excellent electrochemical performance of Cu2 S@NC@MoS3 . The rich active sites and rapid Na+ diffusion kinetics of this ternary heterostructure is beneficial to the high efficient sodium storage. The assembled full cell matched with Na3 V2 (PO4 )3 @rGO cathode likewise displays remarkable electrochemical properties. The outstanding sodium storage performances of Cu2 S@NC@MoS3 heterostructures indicate the potential applications in energy storage fields.

Novel Nanoarchitectured Cu2Te as a Photocathodes for Photoelectrochemical Water Splitting Applications

Designing photocathodes with nanostructures has been considered a promising way to improve the photoelectrochemical (PEC) water splitting activity. Cu₂Te is one of the promising semiconducting materials for photoelectrochemical water splitting, the performance of Cu₂Te photocathodes remains poor. In this work, we report the preparation of Cu₂Te nanorods (NRs) and vertical nanosheets (NSs) assembled film on Cu foil through a vapor phase epitaxy (VPE) technique. The obtained nano architectures as photocathodes toward photoelectrochemical (PEC) performance was tested afterwards for the first time. Optimized Cu₂Te NRs and NSs photocathodes showed significant photocurrent density up to 0.53 mA cm^-2 and excellent stability under illumination. Electrochemical impedance spectroscopy and Mott-Schottky analysis were used to analyze in more detail the performance of Cu₂Te NRs and NSs photocathodes. From these analyses, we propose that Cu₂Te NRs and NSs photocathodes are potential candidate materials for use in solar water splitting.

CuxS nanosheets with controllable morphology and alignment for memristor devices

In electrochemical metallization memristor, the performance of resistive switching (RS) is influenced by the forming and fusing of conductive filaments within the dielectric layer. However, the growth of filaments, mostly, is unpredictable and uncontrollable. For this reason, to optimize ions migration paths in the dielectric layer itself in the Al/Cu_xS/Cu structure, uniform Cu_xS nanosheets films have been synthesized using anodization for various time spans. And the Al/Cu_xS/Cu devices show a low operating voltage of less than 0.3 V and stable RS performance. At the same time, a reversible negative differential resistance (NDR) behavior is also demonstrated. And then, the mechanism of repeatable coexistence of RS effect and NDR phenomenon is investigated exhaustively. Analyses suggest that the combined physical model of space-charge limited conduction mechanism and conductive filaments bias-induced migration of Cu ions within the Cu_xS dielectric layer is responsible for the RS operation, meanwhile, a Schottky barrier caused by copper vacancy at the Cu_xS/Cu interface is demonstrated to explain the NDR phenomenon. This work will develop a new way to optimize the performance of non-volatile memory with multiple physical attributes in the future.

Employing Ni-Embedded Porous Graphitic Carbon Fibers for High-Efficiency Lithium-Sulfur Batteries

The rational electrode design is one of the most important ways to enhance the electrochemical properties of lithium-sulfur batteries (LSBs). In this contribution, we use Ni-embedded porous graphitic carbon fiber (PGCF@Ni) as the scaffold to construct a novel cathode and anode for LSBs. With the help of elaborate surface engineering, the constructed solid electrolyte interface (SEI)@Li/PGCF@Ni anodes can effectively restrain the growth of lithium dendrites during the cycle, exhibiting an ultralow overpotential of ∼10 mV for 2000 h at 1 mA cm^-2/1 mA h cm^-2. The underlying mechanism is further investigated by COMSOL Multiphysics simulations. Additionally, the PGCF@Ni/S cathode fabricated by the molten sulfurizing method manifests superior rate performance and stability. Ultimately, the assembled SEI@Li/PGCF@Ni||PGCF@Ni/S full battery exhibits prominent electrochemical property with a high capacity retention of about 77.9% after 600 cycles at 1 C. Such success at the performance improvement in LSBs may open up avenues toward other rational designs of high-quality electrodes in electrochemical energy storage.

Rationally integrated nickel sulfides for lithium storage: S/N co-doped carbon encapsulated NiS/Cu2S with greatly enhanced kinetic property and structural stability

Nickel sulfides are promising anode materials for lithium-ion batteries (LIBs) due to their high theoretical capacities but suffer from the sluggish kinetic process and poor structural stability. Herein, we develop...

High-yield Synthesis and Hybridizations of Cu Microplates for Catalytic Applications

Because of their special geometrical features, which include a high specific surface area and high proportion of exposed surface atoms, two-dimensional (2D) metal nanostructures based on Au and Ag have...

Study of the Lithium Storage Mechanism of N-Doped Carbon-Modified Cu2 S Electrodes for Lithium-Ion Batteries

Owing to their high specific capacity and abundant reserve, Cu_xS compounds are promising electrode materials for lithium‐ion batteries (LIBs). Carbon compositing could stabilize the Cu_xS structure and repress capacity fading during the electrochemical cycling, but the corresponding Li⁺ storage mechanism and stabilization effect should be further clarified. In this study, nanoscale Cu₂S was synthesized by CuS co‐precipitation and thermal reduction with polyelectrolytes. High‐temperature synchrotron radiation diffraction was used to monitor the thermal reduction process. During the first cycle, the conversion mechanism upon lithium storage in the Cu₂S/carbon was elucidated by operando synchrotron radiation diffraction and in situ X‐ray absorption spectroscopy. The N‐doped carbon‐composited Cu₂S (Cu₂S/C) exhibits an initial discharge capacity of 425 mAh g⁻¹ at 0.1 A g⁻¹, with a higher, long‐term capacity of 523 mAh g⁻¹ at 0.1 A g⁻¹ after 200 cycles; in contrast, the bare CuS electrode exhibits 123 mAh g⁻¹ after 200 cycles. Multiple‐scan cyclic voltammetry proves that extra Li⁺ storage can mainly be ascribed to the contribution of the capacitive storage.