Honeycomb-Spherical Co3O4-TiO2 Hybrid Materials for Enhanced Lithium Storage

Recent Advances on Heterojunction-Type Anode Materials for Lithium-/Sodium-Ion Batteries

Rechargeable batteries are key in the field of electrochemical energy storage, and the development of advanced electrode materials is essential to meet the increasing demand of electrochemical energy storage devices with higher density of energy and power. Anode materials are the key components of batteries. However, the anode materials still suffer from several challenges such as low rate capability and poor cycling stability, limiting the development of high-energy and high-power batteries. In recent years, heterojunctions have received increasing attention from researchers as an emerging material, because the constructed heterostructures can significantly improve the rate capability and cycling stability of the materials. Although many research progress has been made in this field, it still lacks review articles that summarize this field in detail. Herein, this review presents the recent research progress of heterojunction-type anode materials, focusing on the application of various types of heterojunctions in lithium/sodium-ion batteries. Finally, the heterojunctions introduced in this review are summarized, and their future development is anticipated.

Construction of heterostructured NiFe2O4-C nanorods by transition metal recycling from simulated electroplating sludge leaching solution for high performance lithium ion batteries

NiFe2O4 has been regarded as one of the promising candidates for lithium-ion battery (LIB) anode materials due to its high theoretical specific capacity. However, the large volume expansion and pulverization of NiFe2O4 during the charge/discharge process result in severe capacity fading. Herein, heterostructured NiFe2O4-C nanorods have been successfully fabricated by recovering transition metals from simulated electroplating sludge leaching solution. The constructed NiFe2O4-C heterointerface plays a vital role in accommodating volume change, stabilizing the reaction products and providing rapid electron and Li+ ion transportation ability, resulting in a high and stable Li+ accommodation performance. The fabricated NiFe2O4-C nanorods demonstrate a high specific capacity (889.9 mA h g-1 at 100 mA g-1), impressive rate capability (861.5, 704.5, 651.4, 579.6 and 502.1 mA h g-1 at 0.2, 0.6, 1.0, 2.0 and 5.0 A g-1) and cycling stability (650.2 mA h g-1 at 2 A g-1 after 500 cycles). This work exemplifies a facile and effective approach for the fabrication of high performance LIB electrode materials by recycling metals from electroplating sludge in an application-oriented manner.

Construction of Co3O4 three-dimensional mesoporous framework structures from zeolitic imidazolate framework-67 with enhanced lithium storage properties

High-porosity mesoporous framework structures are attractive for electrochemical energy storage and other applications. Herein we demonstrate a novel synthesis strategy to make zeolitic imidazolate framework-67 oxidize to a Co₃O₄ three-dimensional mesoporous framework structure. This strategy relies on the oxygen-limitation effect of the closed nanocage and the affinity effect of polyvinylpyrrolidone towards zeolitic imidazolate framework-67. Several TiO₂ nanospheres, as the unique structure junctions, are uniformly embedded within the Co₃O₄ framework to enhance the framework strength. The TiO₂/hydrous titania polyhedron nanocage, as the protecting shell, further encapsulates the Co₃O₄ framework, forming a perfect capsule-type hybrid. As anode materials for lithium-ion batteries, TiO₂@Co₃O₄ framework capsules show superior lithium storage performance with high reversible capacity, stable cycling life and good rate capability. A reversible capacity of 1042 mAh g^-1 can be delivered after 200 cycles at a current density of 300 mA g^-1. The average discharge capacity over 200 cycles reaches 926 mAh g^-1. This demonstrates the superiority of this material structure and its great potential as an anode for high-performance lithium-ion batteries. This work indicates a new strategy to take advantage of metal-organic frameworks to synthesize their mesoporous framework derivatives.

Co3O4 hollow nanospheres/carbon-assembled mesoporous polyhedron with internal bubbles encapsulating TiO2 nanosphere for high-performance lithium ion batteries

Co₃O₄ hollow nanospheres 15 nm in the diameter were assembled to the mesoporous polyhedron together with carbon. Within the Co₃O₄ polyhedrons, the bubbles 300-500 nm in diameter were uniformly generated. Every bubble further encapsulated one TiO₂ nanosphere, forming a unique sphere-bubble structure. The specific surface area and the pore volume were calculated to be 97.85 and 0.31 cm³ g^-1. When evaluated as anode material for lithium ion batteries, the as-prepared material exhibited superior lithium storage properties with high specific capacity, excellent cycling stability and good rate capability. After 400 cycles, the discharge capacity of 609 mAh g^-1 was still delivered at current density of 335 mA g^-1. Even at a high current density of 2000 mA g^-1, the reversible capacity reached 296 mAh g^-1. The outstanding electrochemical performance was attributed to the unique hybrid structure, which avoids nanomaterial aggregation, promotes ion diffusion and electron transfer, accommodates volume change of Co₃O₄ during (de)lithiation process, enhances structure strength, cycling stability and space utilization ratio of the hollow material.

Biomimetic Straw-Like Bundle Cobalt-Doped Fe2 O3 Electrodes towards Superior Lithium-Ion Storage

Biomimetic straw-like bundles of Co-doped Fe₂ O₃ (SCF), with Co²⁺ incorporated into the lattice of α-Fe₂ O₃ , was fabricated through a cost-effective hydrothermal process and used as the anode material for lithium-ion batteries (LIBs). The SCF exhibited ultrahigh initial discharge specific capacity (1760.7 mA h^-1  g^-1 at 200 mA g^-1 ) and cycling stability (with the capacity retention of 1268.3 mA h^-1  g^-1 after 350 cycles at 200 mA g^-1 ). In addition, a superior rate capacity of 376.1 mA h^-1  g^-1 was obtained at a high current density of 4000 mA g^-1 . The remarkable electrochemical lithium storage of SCF is attributed to the Co-doping, which increases the unit cell volume and affects the whole structure. It makes the Li⁺ insertion-extraction process more flexible. Meanwhile, the distinctive straw-like bundle structure can accelerate Li ion diffusion and alleviate the huge volume expansion upon cycling.

Nanosized CoO Loaded on Copper Foam for High-Performance, Binder-Free Lithium-Ion Batteries

The synthesis of nanosized CoO anodes with unique morphologies via a hydrothermal method is investigated. By adjusting the pH values of reaction solutions, nanoflakes (CoO-NFs) and nanoflowers (CoO-FLs) are successfully located on copper foam. Compared with CoO-FLs, CoO-NFs as anodes for lithium ion batteries present ameliorated lithium storage properties, such as good rate capability, excellent cycling stability, and large reversible capacity. The initial discharge capacity is 1470 mA h g⁻¹, while the reversible capacity is maintained at 1776 m Ah g⁻¹ after 80 cycles at a current density of 100 mA h g⁻¹. The excellent electrochemical performance is ascribed to enough free space and enhanced conductivity, which play crucial roles in facilitating electron transport during repetitive Li⁺ intercalation and extraction reaction as well as buffering the volume expansion.

Preparation of 3D hierarchical porous Co3O4 nanostructures with enhanced performance in lithium-ion batteries

Three-dimensional hierarchical Co₃O₄ microspheres assembled by well-aligned 1D porous nanorods were successfully fabricated. The sample exhibited excellent electrochemical properties as anode materials for LIBs.