Unusual Formation of CoO@C “Dandelions” Derived from 2D Kagóme MOLs for Efficient Lithium Storage

Abstract

sources. [1][2][3] To satisfy the requirements of upcoming large-scale energy storage applications, it is highly urgent to develop high-energy-density LIBs by elegantly configuring advanced electrode materials. The present commercial graphite anodes have a low theoretical capacity of 372 mA h g −1 , approaching the lithium storage limit. [4][5][6] Transition-metal oxides (TMOs) outperform graphite as anode alternatives, mechanistically operating through conversion reactions. [1] Notably, cobalt oxides (CoO or Co 3 O 4 ) can theoretically deliver as much as two to three times the specific capacity of graphite due to their multielectron conversion reaction upon electrochemical cycling. [5][6][7] However, the undesired volume expansion of cobalt oxides leads to the destruction of electrodes, accompanied by rapid capacity fading during repeated lithium ion insertion/extraction processes; additionally, their poor electrical conductivity causes weak rate capability. [8,9] Therefore, the lithium storage performance of materials that include cobalt oxides requires optimization of their composition and structure through engineering to achieve lithium storage performance suitable for practical applications. [4,[10][11][12] To this end, one of the most effective strategies is confining or embedding TMOs into a carbonaceous matrix to form hybrids, which can accommodate large volume changes, improve electrical conductivity, and maintain the integrity of the electrode. Generally, the sources of TMOs and carbon are separate, and the carbonization proceeds via a gas-solid reaction. However, another strategy wherein a single precursor was pyrolyzed to simultaneously generate the two components was also efficacious to create these hybrids. This method exhibits advantages including nanosized TMO particles and a highsurface-area carbon matrix. Despite recent advances, the search for suitable precursors for advantageous novel hybrid materials with enhanced performance remains challenging.Metal-organic frameworks (MOFs) are highly ordered crystalline polymers with tailorable voids constructed by the coordination of metal ions or polynuclear clusters with polytopic organic ligands. They serve as precursors for facile transformation into hybrid structures including composites of metal oxides/carbon, metal phosphides/carbon, or metal sulfides/carbon after thermal treatment under appropriate atmospheres. [13][14][15][16][17][18] As a Despite great breakthroughs, the search for anode materials with high performance for lithium-ion batteries (LIBs) remains challenging. Hence, engineering advantageous structures via effective routes can bring new possibilities to the development of the LIB field. Herein, the precise synthesis of three-dimensional (3D) hybrids of ultrathin carbon-wrapped CoO (CoO@C) dandelions is reported by the pyrolysis of two-dimensional (2D) Kagóme metal-organic layers (MOLs) at 400 °C under an Ar atmosphere. Due to the special coordination structure of the paternal MOLs, the resulting CoO nanowires show a small diameter ...

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“…[55,56] By comparing the orange area with the total stored charge, the contribution of the capacitive process is determined. [55,56] By comparing the orange area with the total stored charge, the contribution of the capacitive process is determined.…”