Revealing the atomistic origin of the disorder-enhanced Na-storage performance in NaFePO4 battery cathode

Abstract

Revealing the atomistic origin of the disorder-enhanced Na-storage performance in NaFePO 4 battery cathode, Nano Energy,

Role of Amorphous Phases in Enhancing Performances of Electrode Materials for Alkali Ion Batteries

“…Recently, through amorphization, an important breakthrough was achieved in enhancing the Na-storage performance of maricite-type NaFePO 4 (Kim et al, 2015;Rahman et al, 2017;Liu et al, 2018;Xiong et al, 2019). Unexpectedly, after desodiation at high potential (4.5 V vs. Na + /Na) for 5 h, the maricite NaFePO 4 exhibited a high reversible sodium storage capacity of 142 mA h g −1 at C/20 without obvious decay after 200 cycles (Kim et al, 2015).…”

“…Employing another amorphization approach, i.e., mechanochemical ball milling, we attempt to obtain amorphous NaFePO 4 (Xiong et al, 2019). Systematic calorimetric characterizations indicate that the glass transition was not observed prior to the sharp crystallization peak, verifying that NaFePO 4 is a poor glass former, coinciding with the failure in preparing NaFePO 4 glass though melt-quenching method (Nakata et al, 2016).…”

“…Also, the optimized NaFePO 4 composite delivers an initial capacity of 115 mA h g −1 at 1 C (155 mA g −1 ) with capacity retention of 91.3% after 800 cycles. Furthermore, systematic structural characterizations, such as the X-ray absorption near edge and Raman spectroscopy, were performed to reveal the atomic-scale structural evolution of NaFePO 4 from crystalline to amorphous phase (Xiong et al, 2019). For example, according to the O K-edge X-ray absorption near edge spectra, the decrease of the nearest coordination number of oxygen was verified after amorphization.…”

“…To further enhance the electrochemical performances of AIBs, great efforts have been focused on the fabrication of new nanostructures in electrode materials through the atomic-scale design strategy during the past decades (Kang and Ceder, 2009;Sun Y. K. et al, 2012;Zhang et al, 2014;Xiong et al, 2015;Qing et al, 2016;Deng et al, 2017;Wei et al, 2017). However, another important strategy, i.e., amorphization engineering, recently received much attention considering the unique functionalities of amorphous phases (Liu et al, 2012;An et al, 2014;Fang et al, 2014;Mathew et al, 2014;Kim et al, 2015;Nakata et al, 2016;Zhou et al, 2017;Wei et al, 2018;Zhang et al, 2018Zhang et al, , 2019Xiong et al, 2019). For example, the electrochemical performances of crystalline host materials relatively rely on various factors, such as the available energetically equivalent sites for guestion occupation/transport, crystal orientation, structural stability, phase transition, the spatial dimension of ion migration, defects in crystal, and the stoichiometric limitation of ion insertion (Liu et al, 2015;Xiang et al, 2015;Deng et al, 2017;Wang et al, 2018).Compared to those crystalline electrodes, the amorphous counterparts could deliver much improved specific capacities and long-term cyclability over a wide potential window (Mathew et al, 2014;Wei et al, 2018;Zhang et al, 2019).…”

“…Various routes can be applied to amorphize or vitrify the corresponding crystal materials. Besides the conventional meltquenching method (Nakata et al, 2016;Zhang et al, 2018;Fan et al, 2019), there are many other techniques such as ball milling (Kapaev et al, 2017;Xiong et al, 2019), electrochemically induced amorphization (Kim et al, 2015;Rahman et al, 2017;Liu et al, 2018), sol-gel (Fang et al, 2014;Mathew et al, 2014), and magnetron sputtering (Baranchugov et al, 2007;Shi et al, 2009). Here we focus on only three techniques for amorphization: melt quenching, mechanochemical ball milling, and electrochemically induced amorphization.…”