Enhancement of electrochemical properties of platinum doped LiFePO 4 /C cathode material synthesized using hydrothermal method M. Talebi-Esfandarani, O. Savadogo ⁎ Laboratory of New Materials for Electrochemistry and Energy, École Polytechnque de Montréal, C.P. 6079, Succ. Centre Ville, Montréal, QC H3C 3A7, Canada abstract article info Article history: Received 18 November 2013 Received in revised form 26 March 2014 Accepted 28 March 2014 Available online 10 May 2014 Keywords: LiFePO 4 Hydrothermal method Platinum doping The Pt-doped LiFePO 4 /C cathode material was synthesized for the first time. LiFePO 4 and LiFe 0.96 Pt 0.04 PO 4 com- posites were synthesized using a hydrothermal method. The physical and chemical properties of samples were characterized by XRD, XPS, SEM and BET. For electrochemical property investigation, the samples were mixed with sucrose as carbon source, and calcined at 700 °C for 5 h. The XRD results showed that the platinum has been successfully doped into LiFePO 4 bulk structure. The XPS results indicated that platinum doping does not change the chemical state of Fe (II). The SEM and BET results showed that platinum doping reduces the size of the particles. The electrochemical characterization of the electrodes using discharge capacity, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) showed that the Li-ion cell based on LiFe 0.96 Pt 0.04 PO 4 /C electrode exhibited better charge/discharge performance than that of LiFePO 4 /C sample. The LiFe 0.96 Pt 0.04 PO 4 /C based cell delivered the specific capacity of 168, 162, 135, 120 and 102 mAh g -1 at 0.1C, 0.2C, 1C, 5C and 10C, respectively, in comparison with 117, 104, 83, 63 and 47 mAh g -1 for the LiFePO 4 /C cell. © 2014 Elsevier B.V. All rights reserved. 1. Introduction For the past two decades, Li-ion battery has attracted much attention for powering portable electronic devices considering its combination of high power and energy density, long cyclic life, and stability [1,2]. Con- ventionally, LiCoO 2 with a capacity of 140 mAh g -1 is being used as a cathode material in commercial Li-ion batteries. However, LiCoO 2 has its own drawbacks such as the limited abundance in nature, the toxicity issue and the high cost [2]. LiFePO 4 has been suggested as a promising candidate to replace LiCoO 2 as a cathode material for the next genera- tion Li-ion batteries. LiFePO 4 has distinctive features of high theoretical capacity (170 mAh g -1 ), high discharge potential (~3.45 V vs Li + /Li), excellent thermal stability, low cost and being environmentally friendly [3,4]. However, pristine LiFePO 4 suffers from its poor ion diffusion coef- ficient (10 -14 cm 2 s -1 ) and low electrical conductivity (10 -9 S cm -1 ), limiting its application in large devices [5,6]. To solve these drawbacks, progressive strategies have been employed such as coating particles with a conductive carbon layer [7,8], reducing the particle sizes [9,10], and doping with guest elements [11–13]. Among these strategies, particle size reduction and carbon coating have proven to be effective methods for improving the electrochemical performance of LiFePO 4 material, due to their contribution to decreasing the diffusion path length with a larger surface area for more reaction and the enhancement of electronic conductivity of surface of LiFePO 4 material [8,9,14,15]. However, there are controversial results about the doping element strategy [16–18]. The enhancement in the intrinsic electrical conductivity of bulk of LiFePO 4 material through doping has been reported [16,19–21]. Nevertheless, incorporation of element dop- ing causes formation of impurities and influences the electrochemical features of LiFePO 4 material. Some impurities such as Fe 2 P conductive film and Li 4 P 2 O 7 improve the electrochemical performance while some impurities likes insulating Li 3 PO 4 deteriorate the performance drastically. [14,17,22–24]. In addition, the theoretical studies proposed that doping is not favorable [25]. Despite of these arguments, many reports indicate enhancement of electrical conductivity and electro- chemical performance of LiFePO 4 by different doped elements [11–13, 19–21,26–29]. LiFePO 4 can be synthesized by various methods including solid- state reaction, microwave, sol-gel, co-precipitation, hydrothermal, solvothermal and etc. [30–33]. Among these methods, the hydrothermal synthesis, which has some advantages such as simple synthesis process, low energy consumption, and morphology controllability, is a useful and efficient method to obtain well-crystallized uniform LiFePO 4 particles [34–36]. In general, the synthesis method can affect the morphology, size of particles, specific surface area, purity and crystal structure of LiFePO 4 material, resulting in different electrochemical properties [15, 33,36–38]. We have already reported that the Pt-doped LiFePO 4 prepared by sol–gel method can improve the electrochemical performance [39]. This work reports for the first time the effects of platinum doping on Solid State Ionics 261 (2014) 81–86 ⁎ Corresponding author. Tel.: +1 514 3404725. E-mail address: osavadogo@polymtl.ca (O. Savadogo). http://dx.doi.org/10.1016/j.ssi.2014.03.028 0167-2738/© 2014 Elsevier B.V. All rights reserved. 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