Journal of the Korean Physical Society, Vol. 65, No. 3, August 2014, pp. 317∼324 Effect of Copper Content in the New Conductive Material Cu-SPB Used in Low-temperature Li-ion Batteries Adnan Yaqub, Syed Atif Pervez, Umer Farooq, Mohsin Saleem and Chil-Hoon Doh ∗ Korea Electro-technology Research Institute (KERI), Changwon 642-120, Korea and Electrical Functionality Material Engineering (KERI Campus), University of Science and Technology, Daejeon 305-333, Korea You-Jin Lee, Minji Hwang, Jeong-Hee Choi and Doohun Kim Korea Electro-technology Research Institute (KERI), Changwon 642-120, Korea (Received 14 January 2014, in final form 28 February 2014) A new conductive material, copper/Super-P carbon black composite (Cu-SPB), is prepared via an efficient ion reducing method for use in low-temperature lithium-ion batteries (LIBs). The present study investigated the effects of copper content on the low-temperature performance of LIBs. Electrodes prepared with a high-copper-content conductive material (Cu = 18.54%) showed remarkably improved performance in terms of capacity retention (around 40%), cycling stability, and columbic efficiency. The electrochemical impedance spectroscopy (EIS) analysis revealed that the presence of higher Cu contents could reduce the cell’s impedance. The results were also confirmed by using a coin-type full cell’s improved capacity retention, which indicated the significance of Cu particles in enhancing the low-temperature performance of LIBs. PACS numbers: 82.47.Aa, 82.45.Yz, 81.05.Uw Keywords: Graphite anode, Copper supported SPB, Conductive material, Low-temperature LIBs DOI: 10.3938/jkps.65.317 I. INTRODUCTION Lithium ion batteries (LIBs) are considered state-of- the-art energy storage devices [1]. In 1991, when Sony launched the first LIB, shortly thereafter they showed ever increasing demand as power sources for portable de- vices such as cellular phones, laptop computers, and digi- tal cameras [2,3]. LIBs show a great deal of power and en- ergy at and around ambient temperatures [4–8]. Because of this, LIBs are dominating the market as other batter- ies NiCd and NiMH have failed to satisfy consumers’ needs [9]. LIBs are the best candidates for energy stor- age used in space and aerospace applications [10]. Power sources are used to supply of energy but also to perform over a wide temperature range [11]. However, as the tem- perature varies (high or low), the poor electrochemical performance of LIBs at low temperatures is one of the major technical barriers to their practical applications as energy sources [12]. When the temperature falls below -20 ◦ C, both the power and the energy of LIBs have been reported to be significantly reduced [13]. Usually, graphite is used as the anode in LIBs due to its good cyclic performance, safety features and abun- ∗ E-mail: chdoh@keri.re.kr; Tel: +82-55-280-1662 dant availability. However, graphite shows certain limi- tations when the temperature varies [14–16]. Recently, many efforts have been made to enhance the performance of graphite anodes at low temperatures. Several factors are responsible for the low rate capability and the poor electrochemical performance of LIBs at low temperatures such as (i) the reduced conductivity of the electrolyte and solid electrolyte interphase (SEI) film, (ii) the high charge-transfer resistance at the electrolyte-electrode in- terface, and (iii) the limited diffusivity of lithium ions within the graphite anode [17, 18]. Many efforts have been pursued to overcome such limitations. For this pur- pose, the use of metal particles (i.e., Cu, Ag, Ni, Sn) dispersed in the electrode’s slurry is useful for improving the low-temperature performance of the graphite anode [19–21]. Among various metals particles, Cu has been revealed to be one of the most productive additives for graphite electrodes used for low-temperature LIBs. The addition of small amounts of metal particles to an anode active material has already been reported [22,23]. Mari- naro et al. [1] showed that a new conductive material, the Cu-SPB composite (copper/Super-P carbon black) prepared by using a microwave-assisted procedure, could improve the intercalation capacity of anodes at low tem- peratures, but whether or not the low-temperature be- havior is improved is still debatable. -317-