Papers 2021

1.  Effect of fluoroethylene carbonate on transport property of the electrolyte towards Ni-rich Li-ion batteries with high safety
Salatan Duangdangchote, Nutthaphon Phattharasupakun, Praeploy Chomkhuntod, Poramane Chiochan, Sangchai Sarawutanukul, Chanikarn Tomon, Nattanon Joraleechanchai, Montree Sawangphruk
Chem. Commun., 2021
Transport phenomena and the solvation structure of lithium ions (Li+) and hexafluorophosphate anions (PF6−) in the electrolyte with different fluoroethylene carbonate (FEC) concentrations as well as the electrochemical performance and safety of the Ni-rich Li-ion battery cells at the 18650 cylindrical cell level are investigated. We have found that the electrolyte with an optimized FEC concentration (25 %v/v) can effectively enhance the transport property in terms of Li+ transference number and contact ion pair (CIP) ratio leading to high performance and safety of practical 18650 cylindrical LIBs.

2.  Solar-driven energy storage enhancement of nickel hydroxide nanomaterials
Ketsuda Kongsawatvoragul, Praeploy Chomkhuntod, Montree Sawangphruk
Electrochimica Acta, Volume 388, 20 August 2021, 138654
Nickel hydroxide (Ni(OH)2) is one of the most promising cathode materials that are widely used in rechargeable batteries, for instance, the nickel-metal hydride battery (NiMH). The challenge relating to Ni(OH)2 is the charge transfer process during the electrochemical reaction. In this work, Ni(OH)2 was explored as both photo-harvesting and energy storage materials under UV-visible light (AM1.5) illumination to enhance the charge transfer process for the electrochemical reaction of Ni(OH)2 via the photovoltaic effect. The generation of polaron, an electron-hole pair of Ni(OH)2, under light and potential bias increases the charge carrier density for the electrochemical reaction. The result suggests that the capacity was enhanced by 14.4% compared with that under the dark condition. This new finding may further improve the charge storage capacity and development of NiMH and others using metal oxide and hydroxide materials as electrode materials for sustainability.

3.  The electrochemistry of size dependent graphene via liquid phase exfoliation: capacitance and ionic transport
Varisara Deerattrakul, Wisit Hirunpinyopas, Nuttapon Pisitpipathsin, Thanit Saisopa, Montree Sawangphruk, Chakrit Nualchimplee, Pawin Iamprasertkun
Phys. Chem. Chem. Phys., 2021,23, 11616-11623

Abstract: Recently, graphene-based materials have become ubiquitous in electrochemical devices including electrochemical sensors, electrocatalysts, capacitive and membrane desalination and energy storage devices. However, many of the electrochemical properties of graphene (particularly the capacitance and ionic transport) are not yet fully understood. This paper explores the capacitance and ionic transport properties of size dependent graphene (from 100 nm to 1 μm) prepared through the liquid phase exfoliation of graphite in which the size of graphene was finely selected using a multi-step centrifugation technique. Our experiment was then expanded to include basal plane graphene using highly ordered pyrolytic graphite as a model electrode, describing the assumed theoretical graphene capacitance (quoted as 550 F g−1 or 21 μF cm−2) and the electrochemical surface area of the carbon-based materials. This work improves our understanding of graphene electrochemistry (capacitance and ion transport), which should lead to the continuing development of many high-performance electrochemical devices, especially supercapacitors, capacitive desalination and ion-based selective membranes.

4.  Insight into the effect of ionic liquid-based additives at the solid electrolyte interphase for lithium metal batteries
Nattanon Joraleechanchai, Salatan Duangdangchote, Montree Sawangphruk
The Electrochemical Society, 14 April 2021
Abstract: We have investigated the effect of ionic liquids (ILs) additives in 1M LiTFSI in 1,3-dioxolane (DOL)/dimethyl ether (DME) (1:1, v/v) on the solid electrolyte interphase (SEI) using a combined theoretical and experimental method for next-generation Li metal batteries. Among all investigated cations of ILs including imidazolium (IMI+), pyrrolidinium (PYR+), and piperidinium (PIP+) cations, we have observed that the presence of IMI+ provides relatively larger decomposed products of the TFSI anion on the Li metal surface when compared with saturated-ring type cation ILs including PYR+- and PIP+-ILs due to its high electron affinity (EA). Furthermore, the reactive molecular dynamics results show that the SEI layer of the system using the ILs with saturated rings is significantly thin when compared to that of the ILs with aromatic-ring, which is desired for fast Li-ion diffusivity through the SEI. This finding may lead to an ideal design of electrolyte system for future Li-metal batteries.

5.  Enhancing bifunctional electrocatalysts of hollow Co3O4 nanorods with oxygen vacancies towards ORR and OER for Li–O2 batteries

Chanikarn Tomon, Atiweena Krittayavathananon, Sangchai Sarawutanukul, Salatan Duangdangchote, Nutthaphon Phattharasupakun, Kan Homlamai, Montree Sawangphruk
Electrochimica Acta Volume 367, 20 January 2021, 137490
Abstract: The Co3O4, which is on the top of volcano plot, having high oxygen vacancy of ca. 30% finely tuned promotes narrow band gap, resulting in the facilitation of the electron and charge transportation. The as-synthesized Co3O4 catalyst can improve the electrocatalytic activity towards oxygen evolution reaction (OER) and oxygen reduction reaction (ORR). The as-prepared catalyst exhibits the superior ORR/OER stability for which the relative current decays only 7% and 14% for OER and ORR, respectively. By contrast, the OER stability of the RuO2 catalyst presents the significant decay in relative current about 20%. The ORR stability of Pt/C also remarkably decreases to 29%. The catalyst here can be used as an efficient bifunctional catalyst at the cathode of Li–O2 battery. It provides the superior performance as compared to that using the state-of-the-art Pt/C and RuO2/C electrocatalysts.

6.  Controlling the flake size of bifunctional 2D WSe2nanosheets as flexible binders and supercapacitor materials
Pawin Iamprasertkun, Wisit Hirunpinyopas, Varisara Deerattrakul, Montree Sawangphruk, Chakrit Nualchimplee
Nanoscale Adv., 2021,3, 653-660
Abstract: A new approach using graphene as a conductive binder in electrical supercapacitors has recently been proposed. Graphene shows outstanding properties as a conductive binder, and can be used to replace conductive, additive, and polymer binders. However, graphene follows an EDLC behaviour, which may limit its electrochemical performance. In the process described in this work, we introduced WSe2 nanoflakes as a new approach to using pseudocapacitive materials as binders. The WSe2 nanoflakes were produced through liquid phase exfoliation of bulk WSe2, and the flake size was finely selected using a controlled centrifugation speed. The physical and electrochemical properties of the exfoliated WSe2 flakes were analysed; it was found that the smallest flakes (an average flake size of 106 nm) showed outstanding electrochemical properties, expanding our understanding of transition metal dichalcogenide (TMD) materials, and we were able to demonstrate the applicability of using WSe2 as a binder in supercapacitor electrodes. We also successfully replaced conductive additives and polymer binders with WSe2. The overall performance was improved: capacitance was enhanced by 35%, charge transfer resistance reduced by 73%, and self-discharge potential improved by 9%. This study provides an alternative application of using TMD materials as pseudo capacitive binders, which should lead to the continued development of energy storage technology.

7.  Core-shell Ni-rich NMC-Nanocarbon cathode from scalable solvent-free mechanofusion for high-performance 18650 Li-ion batteries
Nutthaphon Phattharasupakun, Juthaporn Wutthiprom, Salatan Duangdangchote, Sangchai Sarawutanukul, Chanikarn Tomon, Farkfun Duriyasart, Suchakree Tubtimkuna, Chalita Aphirakaramwong, Montree Sawangphruk
Energy Storage Materials Volume 36, April 2021, Pages 485-495
Abstract: Although the Ni-rich LiNi0.8Mn0.1Co0.1O2 (NMC811) cathode can store high electrical energy suitable for powering long-range electric vehicles, its poor cycling stability still hinders the practical application. Herein, a surface coating approach using a green scalable solvent-free mechanofusion process is introduced to prepare an infusing thin layer carbon nanosphere shell to improve the intrinsic drawbacks of NMC811 including poor electrical conductivity, Li+/Ni2+ cation mixing, parasitic reactions with electrolytes, and micro-crack formation. The in operando XRD of NMC811@carbon core@shell so-called NMC811cs reveals the smooth and fast phase transition through H1-H2-H3 with higher Li utilization and better stability even though it shows larger abrupt change in c lattice parameter compared to the pristine NMC811. In addition, the onset potential of CO2 and H2 evolution is found to be extended by the carbon coating as observed by an online Differential Electrochemical Mass Spectrometry. Finally, the practical application of the NMC811cs is demonstrated by the 18650 battery prototype which shows higher specific capacity and energy as well as excellent cycling stability compared to the pristine NMC811. This work provides both fundamental understanding and economical strategy towards highly stable and practical high-energy Li-ion batteries.

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