Abstract
With the aim to reduce the entire cost of lithium-ion batteries and to diminish the environmental impact, the extract of broccoli is used as a strong benign reducing agent for potassium permanganate to synthesize α-KyMnO2 cathode material with pure nanostructured phase. Material purity is confirmed by X-ray powder diffraction and thermogravimetric analyses. Images of transmission electron microscopy show samples with a spider-net shape consisting of very fine interconnected nanoneedles. The nanostructure is characterized by crystallite of 4.4 nm in diameter and large surface area of 160.7 m2 g−1. The material delivers an initial capacity of 211 mAh g−1 with high Coulombic efficiency of 99% and 82% capacity retention after 100 cycles. Thus, α-KyMnO2 synthesized via a green process exhibits very promising electrochemical performance in terms of initial capacity, cycling stability and rate capability.
Highlights
Lithium-ion batteries (LiBs) have been widely used to power many systems [1,2,3]
Particular attention was paid to characterize the crystal-chemistry of Ky MnO2 synthesized via the reduction of potassium permanganate, which always induces a residual fraction of K+ ions (VIII K ionic radius of 1.51 Å) located in the 2 × 2 tunnels of the α-MnO2 lattice, whose main functions are templating and stabilizing the tunneled network [37]
One-dimensional α-Ky MnO2 nanoneedles in pure cryptomelane phase were successfully prepared by a facile, one pot, scalable and environmentally-friendly method
Summary
Lithium-ion batteries (LiBs) have been widely used to power many systems (e.g., portable electronics, tools, hybrid and electric vehicles, etc.) [1,2,3]. Manganese dioxide (MDO) is an abundant, rather cheap and green material, which is used in primary lithium batteries [6], and developed as advanced electrode material for Li-ion, Li-sulfur or Li-air secondary batteries [7,8,9,10,11,12,13]. It can deliver a theoretical capacity of ~320 mAh g−1 based on the transfer of one electron per formula in the potential range of 1.5–4.0 V (vs Li+ /Li). It crystallizes in various polymorphic forms, e.g., α-, β-, γ-, λ- and δ-MnO2 , etc., which differ from each other by the different assembly of octahedral
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