Journal of Power Sources 195 (2010) 7445–7451 Contents lists available at ScienceDirect Journal of Power Sources journal homepage: www.elsevier.com/locate/jpowsour Physical and electrochemical properties of LiMnPO 4 /C composite cathode prepared with different conductive carbons Zhumabay Bakenov, Izumi Taniguchi ∗ Department of Chemical Engineering, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8552, Japan article info Article history: Received 8 April 2010 Received in revised form 7 May 2010 Accepted 11 May 2010 Available online 19 May 2010 Keywords: LiMnPO4/C composites Conductive carbon Spray pyrolysis Wet ballmilling abstract The olivine structured LiMnPO 4 /C composites were prepared by a combination of spray pyrolysis and wet ballmilling using different conductive carbons: acetylene black and two types of ketjen black. The ketjen black with a larger specific surface area and dibutyl phthalate absorption number was found to be more preferable compared with other conductive carbons studied in this work. The LiMnPO 4 /C composite cathode with ketjen black, which has the largest specific surface area, exhibited the largest discharge capacity compared with other LiMnPO 4 /C composites. The largest discharge capacity delivered by this composite cathode was 166 mAh g -1 at 0.05 C, which is about 97% of the theoretical value for LiMnPO 4 . The performance improvement by using this conductive carbon was attributed to its extremely large specific surface area and high ability to absorb the electrolyte, which provide enhanced charge transfer and lithium ion transport in the composite cathode structure. © 2010 Elsevier B.V. All rights reserved. 1. Introduction Secondary Li-ion batteries (LIBs) are dominating the market of portable electronics and expanding its application for the electric- ity powered transportation [1]. Despite this, the serious barriers for its wider use in large scale devices such as car batteries and sta- tionary energy storage systems remain the high cost and toxicity of the LIBs materials, especially, the Co-based cathode materials. The olivine LiMPO 4 (M = Fe, Mn) phosphates are an ideal replace- ment for these cathodes due to its low cost, non-toxicity, large theoretical capacity, and thermal and electrochemical stabilities [2–6]. However, intrinsic low ionic and electronic conductivities of LiMPO 4 restrict achieving high electrochemical activities. This dis- advantage has been successfully overcome in case of LiFePO 4 by the preparation of nanosized powders and conductive coating of the particle surface [2,7,8], and these nanoparticles exhibit a discharge capacity close to its theoretical value. LiMnPO 4 is more attractive than LiFePO 4 due to its higher operating voltage of 4.1 V. However, LiMnPO 4 still remains a challenge for researchers to be developed to the level of practical cathode for LIBs. Various synthetic routes were applied to prepare high-performance LiMnPO 4 cathode [4,5,9,10]. Preparation of nanostructured LiMnPO 4 /C composite particles and conductive carbon addition during its synthesis were used to compensate its low conductivity [5,9–11]. These allowed the per- ∗ Corresponding author. Tel.: +81 3 5734 2155; fax: +81 3 5734 2155. E-mail addresses: taniguchi.i.aa@m.titech.ac.jp, itaniguc@chemeng.titech.ac.jp (I. Taniguchi). formance improvement of LiMnPO 4 cathode material. Up to date the largest discharge capacity for LiMnPO 4 has been reported to be 149 mAh g -1 at 0.1 C in the galvanostatic charge–discharge [5], which is about 87% of the theoretical value of 171 mAh g -1 . For the trickle charge mode conditions, the initial discharge capacity was reported to be about 130 mAh g -1 at 0.1 C discharge rate [4,5,8,9], which is far below of the theoretical capacity of LiMnPO 4 . Therefore, further investigations to improve the electrochemical performance of LiMnPO 4 cathode are crucial. From this point of view, the inves- tigation of the effect of different conductive carbons used in the LiMnPO 4 /C composite on its electrochemical properties is very important [12–18]. Both the abilities of the conductive carbon to conduct electrons and transport lithium ions are crucial for the electrochemical performance of the composite cathodes. Different carbon additives have different physical properties such as parti- cle size, absorption ability and specific surface area. Each of these characteristics of the conductive carbon might have a significant effect on the overall conductivity of the electrode, the electrolyte absorption and, as a result, influence the overall electrochemical performance of the cell. Jin et al. [12] reported that acetylene black (AB) is preferable as a conductive agent for LiCoPO 4 cathode com- pared with carbon black, and the cathode with AB shows better electrochemical performance. It was suggested by Choi et al. [13] that the dibutyl phthalate (DBP) absorption number should be con- sidered more significantly when selecting the carbon black for the cathode mixture. Kuroda et al. [14] studied the effect of different conductive carbons such as ketjen black (KB), AB, and graphite on the electrochemical performance of LiCoO 2 cathode. Among other conductive carbons, KB has a larger surface area and DBP 0378-7753/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.jpowsour.2010.05.023