Cobalt Nanoparticles Chemically Bonded to Porous Carbon Nanosheets: A Stable High-Capacity Anode for Fast-Charging Lithium-Ion Batteries

High stable electrochemical response of atmosphere-modulated jujube cake-like Co@Co3O4 complexes to the tumor marker CD44

CD44 is a complex transmembrane glycoprotein that exists in multiple molecular forms and aberrant expression of CD44 is associated with tumorigenesis and progression. CD44 is involved in the regulation of several important signaling pathways, including tumor proliferation, invasion, metastasis, and therapy resistance, and it is also regulated by a variety of cells, which is a common biomarker for cancer stem cells. Detection and quantification of CD44 can provide essential information useful for clinical cancer diagnosis. Electrochemical sensors are prominently used for the detection of cancer biomarkers due to their rapidity, robustness, ease of miniaturization, excellent sensitivity and selectivity. In this study, we synthesized two cobalt-based materials under different atmospheres by photochemical metal-organic deposition methods (PMOD) and thermal annealing treatments, and then built and optimized two cobalt-based sensors that produce responses to CD44. The results showed that the performance of HA-Co@Co3O4 (HCo@Co3O4) electrodes were superior to that of HA-CoO@Co3O4 (HCoO@Co3O4) in terms of detection limit, sensitivity and stability, the linear range was 1 × 10-5 to 1 × 103 ng mL-1 with a detection limit of 0.619 × 10-5ng mL-1, the trend of the test results was consistent with the conventional Elisa method. The effects of different annealing atmospheres on the electrochemical activity of cobalt oxide-based materials for the detection of CD44 were investigated, which provided an experimental and theoretical basis for the electrochemical detection of CD44 and other types of tumor markers by cobalt oxides. In biomedical detection, very low concentration detection is conducive to the monitoring of CD44 dynamic changes: low concentration of CD44 changes can be detected, which is conducive to the early detection of diseases. In addition, the outstanding detection limit indicates the high selectivity of the material for the target molecule in complex biological samples and the high stability in complex biological samples, it provides a detection basis for future clinical applications.

Flexible PEDOT Multi-decorated Co3O4 Polyhedrons as Anodes for High-Performance Lithium-Ion Batteries

In this work, a Co3O4@PEDOT composite with flexible and conductive poly(3,4-ethylenedioxythiophene) (PEDOT)-coated porous Co3O4 polyhedrons is prepared. The hierarchical porous Co3O4 polyhedrons are obtained by the treatment of cobalt metal-organic framework (ZIF-67) precursors, and their surface is coated with PEDOT via in situ multistage oxidative polymerization of 3,4-ethylenedioxythiophene. Various characterizations, such as X-ray diffraction (XRD), transmission electron microscopy (TEM), and scanning electron microscopy (SEM), indicate that the Co3O4@PEDOT exhibits a core-shell structure. The core is Co3O4 polyhedron with a hierarchical porous structure made up of Co3O4 nanoparticles, while the shell is composed of amorphous PEDOT. The core-shell Co3O4@PEDOT as anode of a lithium-ion battery is tested for charge-discharge performance and exhibits excellent electrochemical performance, delivering capacities of 586 mAh g-1 and 711 mAh g-1 at current densities of 0.3 and 1C (1C = 1A g-1) at 200 cycles, respectively. As a contrast, the uncoated sample Co3O4 only has a capacity close to zero (4 mAh g-1) at 0.3C. These results indicate that the intact and good conductive PEDOT polymer improves the electronic conductive property of Co3O4 and ensures the structural stability of the porous hierarchical Co3O4. The hierarchical porous core-shell structure can provide the abundant space and pathways, which can alleviate the impact of volume changes and accelerate lithium-ion diffusion dynamics during the cyclic process.

Synthesis and Local Characterization of CoO Nanoparticles in Distinct Phases: Unveiling Polymorphic Structures

The advancement of functional nanomaterials has become a major focus of recent research, driven by the exceptional properties these materials display compared to their macroscopic (bulk) counterparts. Cobalt oxide nanoparticles (CoO-NPs) stand out primarily for their catalytic and magnetic properties, which can enable a range of technological applications, such as advanced catalysts, drug delivery systems, implants, prosthetics, sensors. However, in addition to the dependence on factors such as size, morphology, and functionalization, the properties of CoO-NPs are significantly influenced by the crystal structure. Therefore, local investigation into the polymorphic structures of CoO at the nanometric scale may provide new insights into the local structural and magnetic characteristics of these systems. In this report, we address the synthesis and local characterization of cobalt oxide (CoO) nanoparticles in the rock-salt cubic fcc-CoO and Wurtzite hpc-CoO phases, obtained through thermal decomposition. We analyze the influence of oleylamine and oleic acid ligands on the structural and morphological control of these systems. The obtained nanoparticles were characterized using conventional techniques such as X-ray diffraction (XRD), transmission electron microscopy, Raman spectroscopy, and Fourier-transform infrared spectroscopy. Local characterization was carried out by the perturbed angular correlation (PAC) nuclear technique using the radioactive tracer 111In(111Cd). Measurements were conducted at 295 and 10 K to investigate possible magnetic phase transitions in these systems. XRD results confirmed the formation of fcc-CoO and hcp-CoO phases. The phase fcc was obtained with the pair of oleylamine and oleic acid ligands, while the phase hcp phase was synthesized using only oleylamine. Additionally, nanoparticles synthesized with oleylamine and oleic acid exhibited better morphological control compared to those produced with only oleylamine. Raman spectroscopy analyses suggest a phase transformation process resulting in Co3O4. PAC results for hyperfine interactions at the 111In(111Cd) probe nucleus, indicate that the hcp-CoO phase shows smaller hyperfine magnetic interactions (B hf = 1 T) compared to the fcc-CoO phase (B hf = 17 T). This suggests the mechanism of superexchange interactions, which are strongly influenced by the Co-O-Co bond angle, which is 110° for the hpc-CoO phase and 180° for the fcc-CoO phase due to the geometries of the systems.

Uncovering the origin of the anomalously high capacity of a 3d anode via in situ magnetometry

Transition metals can deliver high lithium storage capacity, but the reason behind this remains elusive. Herein, the origin of this anomalous phenomenon is uncovered by in situ magnetometry taking metallic Co as a model system. It is revealed that the lithium storage in metallic Co undergoes a two-stage mechanism involving a spin-polarized electron injection to the 3d orbital of Co and subsequent electron transfer to the surrounding solid electrolyte interphase (SEI) at lower potentials. These effects create space charge zones for fast lithium storage on the electrode interface and boundaries with capacitive behavior. Therefore, the transition metal anode can enhance common intercalation or pseudocapacitive electrodes at high capacity while showing superior stability to existing conversion-type or alloying anodes. These findings pave the way for not only understanding the unusual lithium storage behavior of transition metals but also for engineering high-performance anodes with overall enhancement in capacity and long-term durability.

Unusual pseudocapacitive lithium-ion storage on defective Co3O4nanosheets

Secondary lithium-ion batteries are restricted in large-scale applications including power grids and long driving electric vehicles owing to the low specific capacity of conventional intercalation anodes possessing sluggish Li-ion diffusion kinetics. Herein, we demonstrate an unusual pseudocapacitive lithium-ion storage on defective Co₃O₄nanosheet anodes for high-performance rechargeable batteries. Cobalt-oxide nanosheets presented here composed of various defects including vacancies, dislocations and grain boundaries. Unique 2D holey microstructure enabled efficient charge transport as well as provided room for volume expansions associated with lithiation-delithiation process. These defective anodes exhibited outstanding pseudocapacitance (up to 87%), reversible capacities (1490 mAh g^-1@ 25 mA g^-1), rate capability (592 mAh g^-1@ 30 A g^-1), stable cycling (85% after 500 cycles @ 1 A g^-1) and columbic efficiency (∼100%). Exceptional Li-ion storage phenomena in defective Co₃O₄nanosheets is accredited to the pseudocapacitive nature of conversion reaction resulting from ultrafast Li-ion diffusion through various crystal defects. The demonstrated approach of defect-induced pseudocapacitance can also be protracted for various low-cost and/or eco-friendly transition metal-oxides for next-generation rechargeable batteries.

Realization of High Energy Density Sodium-Ion Hybrid Capacitors through Interface Engineering of Pseudocapacitive 3D-CoO-NrGO Hybrid Anodes

Sodium-ion hybrid capacitors (SHCs) have attracted great attention owing to the improved power density and cycling stability in comparison with sodium-ion batteries. Nevertheless, the energy density (<100 Wh·kg^-1) is usually limited by low specific capacity anodes (<150 mAh·g^-1) and "kinetics mismatch" between the electrodes. Hence, we report a high energy density (153 Wh·kg^-1) SHC based on a highly pseudocapacitive interface-engineered 3D-CoO-NrGO anode. This high-performance anode (445 mAh·g^-1 @0.025 A·g^-1, 135 mAh·g^-1 @5.0 A·g^-1) consists of CoO (∼6 nm) nanoparticles chemically bonded to the NrGO network through Co-O-C bonds. Exceptional pseudocapacitive charge storage (up to ∼81%) and capacity retention (∼80% after 5000 cycles) are also identified for this SHC. Excellent performance of the 3D-CoO-NrGO anode and SHC is owing to the synergistic effect of the CoO conversion reaction and pseudocapacitive sodium-ion storage induced by numerous Na₂O/Co/NrGO nanointerfaces. Co-O-C bonds and the 3D microstructure facilitating efficient strain relaxation and charge-transfer correspondingly are also identified as vital factors accountable for the excellent electrochemical performance. The interface-engineering strategy demonstrated provides opportunities to design high-performance transition metal oxide-based anodes for advanced SHCs.

Reversible, stable Li-ion storage in 2 D single crystal orthorhombic α-MoO3 anodes

Engineering two dimensional (2D) materials at atomic level is a key factor to achieve enhanced electrochemical Li-ion storage properties. This work demonstrates that single crystals of orthorhombic α-MoO₃ phase can preferentially grow with a 2D nanoarchitecture via a ball-milling process, followed by heat treatment at elevated temperature. Detailed FE-SEM and TEM micrographs proved the 2D architecture of α-MoO₃ nanoparticles and Raman spectroscopy evidenced the active vibration modes that correspond to the orthorhombic α-MoO₃ phase. Single crystalline MoO₃ belts depicted high intensity of (0 2 0) and (0 4 0) indexed planes indicating a preferential arrangement. As Li-ion host anode, the 2D α-MoO₃ nanostructure delivered high reversible specific discharge capacity of ~540 mA h g^-1 at 0.2 C-rate with 99.9% coulombic efficiency as well as 63% capacity retention after 200 charge-discharge cycles. An excellent reversible Li-ion storage performance (high capacity, longer cycle life and good rate capability) was attributed to the 2D α-MoO₃ arrangement consists of MoO₆ octahedron by corner sharing chains.

High-Energy-Density Sodium-Ion Hybrid Capacitors Enabled by Interface-Engineered Hierarchical TiO2 Nanosheet Anodes

Sodium-ion hybrid capacitors are known for their high power densities and superior cycle life compared to Na-ion batteries. However, low energy densities (<100 Wh kg^-1) due to the lack of high-capacity (>150 mAh g^-1) anodes capable of fast charging are delaying their practical implementation. Herein, we report a high-performance Na-ion hybrid capacitor based on an interface-engineered hierarchical TiO₂ nanosheet anode consisting of bronze (∼15%) and anatase (∼85%) crystallites (∼10 nm). This pseudocapacitive dual-phase anode demonstrated exceptional specific capacity of 289 mAh g^-1 at 0.025 A g^-1 and excellent rate capability (110 mAh g^-1 at 1.0 A g^-1). The Na-ion hybrid capacitor integrating a dual-phase hierarchical TiO₂ nanosheet anode and an activated carbon cathode exhibited a high energy density of 200 Wh kg^-1 (based on the total mass of active materials in both electrodes) and power density of 6191 W kg^-1. These values are in the energy and power density range of Li-ion batteries (100-300 Wh kg^-1) and supercapacitors (5000-15 000 W kg^-1), respectively. Furthermore, exceptional capacity retention of 80% is observed after 5000 charge-discharge cycles. Outstanding electrochemical performance of the demonstrated Na-ion hybrid capacitor is credited to the enhanced pseudocapacitive Na-ion intercalation of the two-dimensional TiO₂ anode resulting from nanointerfaces between bronze and anatase crystallites. Mechanistic investigations evidenced Na-ion storage through intercalation pseudocapacitance with minimal structural changes. This approach of nanointerface-induced pseudocapacitance presents great opportunities toward developing advanced electrode materials for next-generation Na-ion hybrid capacitors.

Cobalt-promoted fabrication of 3D carbon with a nanotube-sheet mutual support structure: scalable preparation of a high-performance anode material for Li-ion batteries

Currently, the design of carbon-based composite as a high-performance anode material for lithium-ion batteries (LIBs) presents challenges for commercial application. Herein, we developed a three-dimensional carbon-based material with a nanotube-sheet mutual support structure (MS-CNTS) engineered by the catalytic effect of Co species. The present work highlights a concise 'solvent-free' synthetic method allowing for large-scale output, which is potentially available for low cost commercial use. With the readily available acetylacetonate and cobalt (II) acetylacetonate as starting chemicals, this nanostructured carbonaceous material is fabricated with aldol condensation to construct a Co-contained carbon-link network polymer precursor followed by annealing under argon. It is composed of brim-curled graphene-like carbon nanosheets and carbon nanotubes, which support each other's structures to effectively avoid agglomeration. Therefore, it enables high performance in LIBs. In spite of the trace amount of cobalt, the carbon-based MS-CNTS anode delivers a high charge capacity of 1028 mAh g-1 at 0.1 A g-1, high rate capacity of 495 mAh g-1 at 2 A g-1, and ultra-long cycling life with a very low capacity decay of 0.008% per cycle over 1000 cycles at 0.5 A g-1, accompanied by 100% Coulombic efficiency. From full cell measurements, we further confirm the considerable promise of MS-CNTS as anodes with a long cycling life.

A Mn3O4 nanospheres@rGO architecture with capacitive effects on high potassium storage capability

A two dimensional (2D) Mn₃O₄@rGO architecture has been investigated as an anode material for potassium-ion secondary batteries. Herein, we report the synthesis of a Mn₃O₄@rGO nanocomposite and its potassium storage properties. The strong synergistic interaction between high surface area reduced graphene oxide (rGO) sheets and Mn₃O₄ nanospheres not only enhances the potassium storage capacity but also improves the reaction kinetics by offering an increased electrode/electrolyte contact area and consequently reduces the ion/electron transport resistance. Spherical Mn₃O₄ nanospheres with a size of 30-60 nm anchored on the surface of rGO sheets deliver a high potassium storage capacity of 802 mA h g^-1 at a current density of 0.1 A g^-1 along with superior rate capability even at 10 A g^-1 (delivers 95 mA h g^-1) and cycling stability. A reversible potassium storage capacity of 635 mA h g^-1 is retained (90%) after 500 cycles even at a high current density of 0.5 A g^-1. Moreover, the spherical Mn₃O₄@rGO architecture not only offers facile potassium ion diffusion into the bulk but also contributes surface K⁺ ion storage. The obtained results demonstrate that the 2D spherical Mn₃O₄@rGO nanocomposite is a promising anode architecture for high performance KIBs.

A bee pupa-infilled honeycomb structure-inspired Li2MnSiO4 cathode for high volumetric energy density secondary batteries

Emerging power batteries with both high volumetric energy density and fast charge/discharge kinetics are required for electric vehicles. The rapid ion/electron transport of mesostructured electrodes enables a high electrochemical activity in secondary batteries. However, the typical low fraction of active materials leads to a low volumetric energy density. Herein, we report a novel biomimetic "bee pupa infilled honeycomb"-structured 3D mesoporous cathode. We found previously the maximum active material filing fraction of an opal template before pinch-off was about 25%, whereas it could be increased to ∼90% with the bee pupa-infilled honeycomb-like architecture. Importantly, even with a high infilling fraction, fast Li+/e- transport kinetics and robust mechanical property were achievable. As the demonstration, a bee pupa infilled honeycomb-shaped Li2MnSiO4/C cathode was constructed, which delivered a high volumetric energy density of 2443 W h L-1. The presented biomimetic bee pupa infilled honeycomb configuration is applicable for a broad set of both cathodes and anodes in high energy density batteries.

An all-in-one Sn–Co alloy as a binder-free anode for high-capacity batteries and its dynamic lithiation in situ

An all-in-one Sn–Co alloy anode is reported, which exhibits a robust electrode structure confirmed by in situ transmission electron microscopy.

Improved pseudocapacitive charge storage in highly ordered mesoporous TiO2/carbon nanocomposites as high-performance Li-ion hybrid supercapacitor anodes

A Li-ion hybrid supercapacitor (Li-HSCs), an integrated system of a Li-ion battery and a supercapacitor, is an important energy-storage device because of its outstanding energy and power as well as long-term cycle life. In this work, we propose an attractive material (a mesoporous anatase titanium dioxide/carbon hybrid material, m-TiO₂-C) as a rapid and stable Li⁺ storage anode material for Li-HSCs. m-TiO₂-C exhibits high specific capacity (∼198 mA h g⁻¹ at 0.05 A g⁻¹) and promising rate performance (∼90 mA h g⁻¹ at 5 A g⁻¹) with stable cyclability, resulting from the well-designed porous structure with nanocrystalline anatase TiO₂ and conductive carbon. Thereby, it is demonstrated that a Li-HSC system using a m-TiO₂-C anode provides high energy and power (∼63 W h kg⁻¹, and ∼4044 W kg⁻¹).

A mesoporous TiO₂/carbon nanocomposite prepared by block copolymer self-assembly improves pseudocapacitive behavior and achieves high energy/power density Li-ion hybrid supercapacitors.