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26XV International Symposium on Self-Propagating High-Temperature Synthesis
COMBUSTION SYNTHESIZED MATERIALS FOR ELECTROCHEMICAL APPLICATIONS
K.-Y. Chan*", A. A. Voskanyan", C.-K. Ho", L. Wang"A, W. Y. Lam", C.-Y. V. Li", and B. Qin"
^Department of Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong SAR ^Department of Chemistry, Nankai University, China *e-mail: hrsccky@hku.hk
DOI: 10.24411/9999-0014A-2019-10029
There are immense interests in exploring electrochemical power systems, such as metal-ion, metal-air, and flow batteries, to meet the growing demand in large scale energy storage. Reported high performance electrodes of these devices are usually composed of advanced nanostructured materials which cannot be synthesized economically in large scale. Combustion synthesis is attractive for its relatively low capital costs and minimum energy demand. Compositions of metal/metal oxides mixtures can be conveniently controlled with precursors atomically mixed in solution combustion. Porosity is created by gas evolution during combustion and the temperature profile favors particles of well-developed crystallinity. A large range of product composition and structural properties can be tuned by amounts and choices of precursors, fuels, oxidants, solvents, and inert additives.
We discuss here a few recent investigations of applying combustion synthesized metal/metal oxides to electrochemical devices.
Manganese dioxide was synthesized with manganese nitrate and glycine precursors using a previously reported colloidal solution combustion synthesis (CSCS) method, [1] in which 22 nm colloidal SiO2 particles are added before combustion and removed from the product by etching after combustion. The manganese dioxide synthesized has uniform pores of 29 nm dia., 120 m2/g surface area, 0.35 mL/g pore volume, and is composed of 2-3 nm S-phase crystals (S-MnO2).[2] Electrochemical studies of the CSCS synthesized MnO2 show excellent performance as an anode in a lithium-ion battery (LIB) and better than most MnO2 electrodes reported in literature [2].
The overlapping redox peaks after the 1st cycle in Fig. 1a show good reversibility in discharge (lithiation) and charge (delithiation) processes. Figure 1b shows charge/discharge profiles at different rates compared with a commercial P-MnO2 (CommMnO2). Besides high rate capability, CSCS-MnO2 showed excellent cyclability and was able to maintain a high capacity of 320 mAh/g on average for 160 cycles. The SEM image of Fig. 1c after 200 cycles also verifies the preservation of the uniform pore structure.
In another example, high quality palladium thin film was deposited via a one-step aqueous combustion process onto glassy carbon as shown in Fig. 2a with a relatively low deposition temperature of 250°C [3]. Excellent catalytic property and stability are shown in Fig. 2b for electrooxidation of ethanol in alkaline solution. Electrochemical oxygen reduction in a rotating disk operation is shown in Fig. 2c with corresponding kinetics shown in the Koutechy-Levich plot of Fig. 2d.
We also discuss other recent investigations of combustion synthesized materials for applications in electrochemical devices which include the positive electrode (cathode) of lithium-ion battery and negative electrode(anode) of sodium-ion battery.
iSHS 2019 Moscow, Russia
1400
Potential (V VS. Lf/U) Cycle number
(a) (b) (c)
Fig. 1. (a) CV curves of CSCS synthesized 5-MnÜ2 at 0.2 mV/s performed in a lithium-ion coin cell with lithium foil counter electrode, at 1 M LiPF6 in 1:1:1 ethyl carbonate/dimethyl carbonate/ethylmethyl carbonate solution. (b) The rate performance of CSCS synthesized 5-MnÜ2 and commercial ß-MnÜ2 as well as cycling performance at high current density of 1 A g-1; (c) SEM image of CSCS 5-MnÜ2 anode demonstrating well-preserved mesoporous structure after 200 cycles at 1 A g-1 current density.
(a) (b) (c) (d)
Fig. 2. (a) Detachable glassy carbon electrode before and after deposition of Pd film by combustion; (b) Cyclic voltammograms in 0.5 M NaOH + 0.5 M ethanol; (c) Oxygen reduction polarization curves at different rotation speeds for Pd film in an oxygen saturated 0.1 M NaOH solution at a scan rate of 10 mV s-1; and (d) Koutecky-Levich plot of I-1 versus at 0.3 V vs RHE.
This work was fully supported by a grant from the Research Grant Council of the Hong Kong
Special Administrative Region, China (Project no. T23-601/17-R).
1. A.A. Voskanyan, K.Y. Chan, C.Y.V. Li, Colloidal solution combustion synthesis: toward mass production of a crystalline uniform mesoporous CeÜ2 catalyst with tunable porosity, Chem. Mater., 2016, vol. 28, no. 8, pp. 2768-2775.
2. A.A. Voskanyan, C.K. Ho, K.Y. Chan, 3D 5-MnÜ2 nanostructure with ultralarge mesopores as high-performance lithium-ion battery anode fabricated via colloidal solution combustion synthesis, J. Power Sources, 2019, vol. 421, no. 1, pp. 162-168.
3. A.A. Voskanyan, C.Y.V. Li, K.Y. Chan, Catalytic palladium film deposited by scalable low-temperature aqueous combustion, ACS Appl. Mater. Interfaces, 2017, vol. 38, no. 9, pp. 33298-33307.
