Kinetics of Electrochemical Insertion and Extraction of Lithium Ion at SiO

Abstract

The kinetics of the electrochemical insertion and extraction of lithium ion at silicon monoxide ͑SiO͒ were investigated by ac impedance spectroscopy. The resultant Nyquist plots showed two semicircles at high and middle frequency regions. These two semicircles were attributed to lithium-ion transport resistance in a surface film and alloying reaction resistance ͑charge-transfer resistance͒, respectively. We evaluated the activation energies of the charge-transfer reaction from the temperature dependences of the interfacial conductivities. When an ethylene-carbonate-based electrolyte was used, the activation energy of the charge transfer was 32 kJ mol −1 . This activation energy was much smaller than those at graphite electrode or positive electrode materials ͑around 50 kJ mol −1 or more͒. Based on these results, the charge transfer at SiO is exceptionally fast compared to those at other insertion materials. Furthermore, the activation energies of the charge transfer at SiO remained unchanged in various electrolytes. These results suggest that the charge-transfer kinetics at SiO is not influenced by the desolvation of lithium ion from solvent molecules. Lithium-ion batteries have recently attracted much attention as a power source for electric vehicles ͑EVs͒ and plug-in hybrid EVs. These applications of lithium-ion batteries give severe requirements to electrode materials. One such requirement is a significant improvement in the energy density of electrode materials. Therefore, an alternative electrode material has been explored for a much higher energy density. Among the candidates for a new negative electrode are alloying materials such as Si and Sn.1,2 These materials electrochemically react with lithium to form a lithium alloy that has an extremely high energy density compared to graphite. However, the alloying reaction shows a large volume change in the materials, 3 which leads to capacity fade during charge-discharge cycles. 4 To overcome the problem, silicon monoxide ͑SiO͒ has recently attracted much attention as a next generation negative electrode. 5-13SiO shows a small volume change because it contains a relatively small amount of Si element that is active for the alloying reaction. The discharge capacity of SiO electrodes was reported to be over 600 mAh g −1 in several papers, 9-12 which is much higher than that of a graphite electrode ͑372 mAh g −1 ͒. To commercialize the SiO electrode, we need to consider the rate performance in addition to the energy density. However, there are few reports on the kinetic aspect of alloying materials. Our group focused on the kinetics of charge ͑lithium ion͒-transfer reactions at a graphite/electrolyte interface 14,15 and other interfaces. [16][17][18][19] The activation energies of the charge-transfer reactions were around 50 kJ mol −1 or more, which were higher compared to those of lithium-ion transport in solid [20][21][22][23] or liquid [24][25][26] electrolytes. This is because the desolvation of lithium ion from solvents occurs during the charge transfer at the...

Amorphous-silicon@silicon oxide/chromium/carbon as an anode for lithium-ion batteries with excellent cyclic stability

“…As an alternative to nanosilicon, SiO has attracted many researchers' interest [12][13][14][15][16][17][18][19]. At a high temperature, SiO can be disproportionated and the formed nanosilicon particles are surrounded by amorphous SiO x (0 < x 2) [20][21][22][23].…”

Electrochemical behavior of SiO anode for Li secondary batteries

“…Recently, many researchers have focused their attention on finding alternative anode materials such as Li-alloy type materials, which showed higher gravimetric and volumetric capacities than graphite . Among these possible replacement anode materials, silicon monoxide (SiO) has been extensively investigated [14][15][16][17][18][19][20][21][22][23][24][25][26][27][28]. Although SiO has a large Li insertion capacity, it also has a low initial coulombic efficiency and capacity fading upon cycling.…”

Water‐Soluble Conductive Composite Binder Containing PEDOT:PSS as Conduction Promoting Agent for Si Anode of Lithium‐Ion Batteries

“…The activation energy (E a ) of the charge-transfer reaction was calculated based on the Arrhenius equation [Eqs. (1) and (2)]: [60,61] …”