A photochromic zinc-based coordination polymer for a Li-ion battery anode with high capacity and stable cycling stability

Abstract

Rechargeable Li-ion batteries (LIBs) are currently the dominant power source for electric vehicles and portable electronic devices, and for small-scale stationary energy storage. However, one bottleneck of the anode materials for LIBs is the poor cycling performance caused by the fact that the anodes cannot maintain their integrity over several charge-discharge cycles. In this article, a zinc-based two-dimensional coordination polymer [Zn(bcbpy)(PTA)(HO)] (Zn-BCP) has been synthesized (Hbcbpy·2Cl = 1,1'-bis(3-carboxylatobenzyl)-(4,4'-bipyridinium) dichloride, PTA = terephthalic acid), which was characterized by single-crystal X-ray diffraction, powder X-ray diffraction, infrared spectroscopy and thermogravimetric analysis. Because of the presence of electron-deficient bipyridinium moieties, Zn-BCP can easily undergo photoinduced electron transfer and eye-detectable photochromic behavior. Moreover, its luminescence can be switched by UV-Vis light irradiation. When Zn-BCP acts as an anode material for lithium ion batteries, it can deliver a high reversible capacity of 386.2 mA h g at 100 mA g after 100 cycles and a high capacity retention of 93.1% after 1000 cycles at a high rate of 200 mA g, which is supposed to be due to the flexible structure characteristic of the proposed anode. The high capacity may be mainly ascribed to rich insertion sites arising from the aromatic ligands and all of the aromatic ligands are taking part in lithium storage.

The photochromic behaviour of two viologen salts modulated by the distances between the halide anions and the cationic N atoms of viologen

“…Salt 1 is EPR-silent before irradiation, but reveals a single-line signal with g = 1.9989 in the coloured state, which is close to the signal of the free radical electron (Fig. 7) (Xia et al, 2018;, further confirming that the process of photochromism is caused by photostimulated reduction of o-CBbpy to form the radical after irradiation. Both IR spectroscopic and PXRD analysis show that the crystal structure of 1 before irradiation is identical to that of 1 after irradiation (Fig.…”

Zinc(II) Carboxylate Coordination Polymers with Versatile Applications

“…Consequently, Xia and co-workers [ 127 ] synthesized compound [Zn(bcbpy) 0.5 (1,4-bdc)(H 2 O)] n ( 118 ) (bcbpy = 1,1′-bis(3-carboxylatobenzyl)-4,4′-bipyridine) which was tested as an anode material for LIBs. The lithiation and delithiation processes were studied in the voltage range 0.01–3.0 V versus Li + /Li using cyclic voltammetry.…”

The Influence of Anions on Electron-Transfer Photochromism of Bipyridinium-Derived Metal–Organic Materials

“…Photochromic materials are currently attracting great attention, not only because of their unique photochemical and photophysical properties but also because of their potential technological applications in sensors, optical data switches, information displays, electrochromic displays, optical switches, magnetic switching devices, and so on. − The current research in this area is focused on the development of new materials with better photochromic performances or various switching functions, such as electrical conductivity, catalysis, magnetism, and luminescence. − Nevertheless, traditional pure organic and inorganic photochromic compounds cannot sufficiently meet the requirements for the aforementioned functions. Recently, the development of photochromic coordination polymers has drawn more attention because of their greater structural diversity as well as the synergistic effects between their inorganic and organic components. − Photochromic coordination polymers are expected to have better properties than traditional photochromic organic and inorganic materials if efficient photochromic species are developed. − …”