Stable Carbon–Selenium Bonds for Enhanced Performance in Tremella‐Like 2D Chalcogenide Battery Anode

Abstract

LIBs) as the most popular energy storage system have been widely adopted in portable electronic devices and electric vehicles. [1] Besides, sodium-ion batteries (SIBs, NIBs) that have potential beyond LIBs have also received much interest recently due to the naturally abundant sodium source. [2] Both of these two energy storage systems require significant improvement in cycling life and energy density to meet the increasing need for smart power grids, which depends on the development of electrode materials. For the anode materials, carbon-based materials are deeply studied by researchers because of their good cycling stability and low cost. [3] However, the tapping density and specific capacity of carbon are relatively low, which lead to the poor volumetric capacity and limit the commercial application. As typical functional materials, 2D transitionmetal chalcogenides (TMCs) based on conversion reaction are able to give much higher theoretical capacity, which originates from multiple electron transfer per metal anion. [4] The reversible electrochemical conversion reaction of TMCs can be described as follows [5] A M X e A X M 0 nm mn m n n m nin which A = Li + , Na + , etc.; M = Co 2+ , Ni 2+ , Cu 2+ , etc.; X = S 2− , Se 2− , etc. Using the high-profile transition-metal sulfides (MS x ) for LIBs as an example, they usually exhibit poor cycle performance, which can be ascribed to the severe irreversibility happening in the initial delithiation. [6] Under the voltage range of 2.0-2.4 V, a portion of Li 2 S should be oxidized to polysulfides that prefer to dissolve into the electrolyte, which is similar to that of the reason for shuttle effect in Li-S batteries. [7] Therefore, improving the reversibility of the abovementioned reaction and further suppressing the generation of polysulfides is a challenge. As we all know, the electrochemical reversibility depends on the diffusion kinetics of Li + as well as the conductivity of activity materials. [8] Morphology control of electrode material is demonstrated to be an effective technology to elevate its specific capacity and cycling life through providing preferential diffusion pathways for ions, conduction pathways for electrons, and increasing contact areas between active materials and electrolyte. [9] For example, Zhao and co-workers [10] used the two-step synthetic approach to prepare a layer-by-layer 2D cobalt selenide based on conversion reaction has attracted much attention due to its open layered structure and high specific capacity. However, effectively suppressing the fast capacity fade caused by the irreversible Se dissolution and serious volume change during the cycling process is still a challenge. Herein, the concentration of dispersion liquid under supercritical conditions is tuned to induce the CoSe crystal to grow along the graphene oxide (GO), and finally obtain the Tremella-like CoSe-reduced GO (rGO) hybrid. The nature of epitaxial growth leads to the formation of stable CSe bonds, which maintain a favorable conductive connection between CoSe ...

Thermally driven mesoscale chemomechanical interplay in Li0.5Ni0.6Mn0.2Co0.2O2 cathode materials

“…The real-world battery operating conditions could introduce complex local chemical events that are undesired for sustaining battery cycle and safety. Commonly observed local chemical events include but are not limited to local overcharge/overdischarge, 14,15 oxygen release, 16 local structural transformation, 8,17 domain deactivation, 18 transition metal dissolution/precipitation, 6,8,19,20 and dendrite/whisker/protrusion growth. 21,22 The local regions that undergo these undesired chemical reactions may not account for much of the total mass or volume of the battery materials, but they can significantly impact the deliverable energy through impedance growth as well as undermine the safety characteristics of the battery cells through thermal runaway.…”

Recent advances in graphene based materials as anode materials in sodium-ion batteries

“…Besides transition metal sulfides, oxides and phosphides, transition metal selenides [199] and tellurides [200] store Na + via conversion reactions. Wu et al prepared Tremella-like CoSe-rGO hybrid with improved electrical conductivity and mechanical stability by forming stable C-Se bonds [201] . The C-Se bonds with remarkable mechanical stretching, supress the dissolution of Se and mitigate the volume expansion during charge-discharge process.…”

ZIF-67-Derived CoSe/NC Composites as Anode Materials for Lithium-Ion Batteries

“…However, the anode material of commercial LIBs is graphite, and the theoretical capacity of graphite is only 372 mAh g −1 , which cannot meet the capacity requirements of large-scale electronic equipment such as electric vehicles, and limits the application and development of LIBs [3–6]. Therefore, scientists have developed a variety of anode materials to increase the capacity and rate performance of LIBs, such as carbon materials [7–9], transition metal oxides [10–13], metal sulfides [14–17], metal phosphides [18–21], and metal selenide [22–25].…”

“…Compared with widely studied oxides and sulfides, selenide has been relatively rare in the field of LIBs. Among selenides, CoSe is regarded as an excellent anode material for LIBs because of its two-dimensional layer structure, good electrical conductivity, and high theoretical capacity [22]. However, as a negative electrode material for lithium storage based on conversion reaction, like transition metal oxides and sulfides, CoSe suffers serious volume expansion during charge and discharge, resulting in the breakage and pulverization of active materials and loss the connection with the current collector, further causing the acute capacity attenuation [10].…”

“…However, at present, metal compounds and carbonaceous matrix are connected through physical adsorption. Compared with strong coupling, such as chemical bonds, the weak connection will make the metal compounds nanoparticles fall off from carbonaceous matrix under the condition of large current density and long-term cycle [4, 22]. The construction of strong coupling between metal compounds and carbonaceous matrix is still a challenge.…”