Self-assembled Co 3 O 4 nanostructure with controllable morphology towards high performance anode for lithium ion batteries

Nanostructure-Mediated Phase Evolution in Lithiation/Delithiation of Co3O4

Nanostructured transition-metal oxides have been under intensive investigation for their tantalizing potential as anodes of next-generation lithium-ion batteries (LIBs). However, the exact mechanism for nanostructures to influence the LIB performance remains largely elusive. In this work, we discover the nanostructure-mediated lithiation mechanism in Co₃O₄ anodes using ex situ transmission electron microscopy (TEM) and X-ray diffractometry: while Co₃O₄ nanosheets exhibit a typical two-step conversion reaction (from Co₃O₄ to CoO and then to Co⁰), Co₃O₄ nanoarrays can go through a direct conversion from Co₃O₄ to Co⁰ at a high discharge rate. Such nanostructure-dependent lithiation can be rationalized by the slow lithiation kinetics intrinsic to Co₃O₄ nanoarrays, which at a high discharge rate may cause local accumulation of lithium to initiate a one-step Co₃O₄-to-Co⁰ conversion. Combined with the larger volume change observed in Co₃O₄ nanoarrays, the slow lithiation kinetics can lead to inhomogeneous expansion with large stress developed at the reaction front, which can eventually cause structure failure and irreversible capacity loss, as explicitly observed by in situ TEM as well as galvanostatic discharge-charge measurement. Our observation resolves the nanostructure-dependent lithiation mechanism of Co₃O₄ and provides important insights into the interplay among lithiation kinetics, phase evolution, and lithium-storage performance, which can be translated into electrode design strategies for next-generation LIBs.

Several carbon-coated Ga2O3 anodes: efficient coating of reduced graphene oxide enhanced the electrochemical performance of lithium ion batteries

Gallium oxide as a novel electrode material has attracted attention because of its high stability and conductivity. In addition, Ga2O3 will be converted to Ga during the charge and discharge process, and the self-healing behavior of Ga can improve the cycling stability. In this paper, we synthesized Ga2O3 nanoparticles with a size of about 4 nm via a facile sol-gel method. Meanwhile, we employed three types of carbon materials (reduced graphene oxide, mesoporous carbon nanofiber arrays, and carbon nanotubes) to avoid the aggregation of Ga2O3 nanoparticles and improve the conductivity of Ga2O3 during the discharge/charge process as well. Among the three samples, the deactivating defective sites and special carbon matrix of reduced graphene oxide can provide more attachment points for Ga ions, so the Ga2O3 nanoparticles can be more closely and uniformly distributed on rGO. Benefitting from the perfect combination of reduced graphene oxide sheets and Ga2O3 nanoparticles, a stable capacity of the Ga2O3/rGO electrode can be maintained at 411 mA h g-1 at a current density of 1000 mA g-1 after 600 cycles. We believe that this work provides a novel and efficient way to improve the electrochemical stability of Li-ion batteries.

Experimental and theoretical investigations of the effect of heteroatom-doped carbon microsphere supports on the stability and storage capacity of nano-Co3O4 conversion anodes for application in lithium-ion batteries

Conversion-type anode materials have been intensely studied for application in Li-ion batteries (LIBs) due to their potentially higher capacities than current graphite-based anodes. This work reports the development of a high-capacity and stable anode from a nanocomposite of N and S co-doped carbon spheres (NSCSs) with Co₃O₄ (NSCS-Co₃O₄). A hydrothermal reaction of saccharose with l-cysteine was carried out, followed by its carbonization. CSs when used as supports for conversion-type materials provide efficient electron/ion transfer channels, enhancing the overall electrochemical performance of the electrodes. Additionally, the heteroatoms doped in a carbon matrix alter the electronic properties, often increasing the reactivity of the carbon surface, and they are reported to be effective for anchoring metal oxide nanoparticles. Consequently, the NSCS-Co₃O₄ nanocomposites developed in this work exhibit enhanced and stable reversible specific capacity over several cycles. Stable cycling behavior was observed at 1 A g^-1 with 1285 mA h g^-1 of specific capacity retained after 350 cycles along with more than 99% of coulombic efficiency. This material shows excellent rate capability with a specific capacity of 745 mA h g^-1 retained even at a high current density of 5 A g^-1. Detailed DFT-based calculations revealed the role of doped supports in controlling the volume expansion upon lithiation.

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.

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.

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.

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.