Abstract
Olivine-type lithium metal phosphates (LiMPO4) are promising cathode materials for lithium-ion batteries. LiFePO4 (LFP) is commonly used in commercial Li-ion cells but the Fe3+/Fe2+ couple can be usefully substituted with Mn3+/Mn2+, Co3+/Co2+ or Ni3+/Ni2+, in order to obtain higher redox potentials. In this communication we report a systematic analysis of the synthesis condition of LiCoPO4 (LCP) using a solvothermal route at low temperature, being the latter a valuable candidate to overcome the theoretical performances of LFP. In fact LCP shows higher working potential (4.8 V vs 3.6 V) compared to LFP and similar theoretical capacity (167 mAh g-1). Our goal is to show the effect of the synthesis condition of the ability of LCP to reversibly cycle lithium in electrochemical cells. LCP samples have been prepared through a solvo-thermal method in aqueous-non aqueous solvent blends. Different Co2+salts have been used to study the effect of the anion on the crystal growth as well as the effect of solution acidity, temperature and reaction time. Materials properties have been characterized by fast-Fourier transform infrared spectroscopy, X-ray diffraction and scanning electron microscopies. The correlation between structure/morphology and electrochemical performances has been investigated by galvanostatic charge-discharge cycles in lithium half cells with a EC:DMC LiPF6 electrolyte. Going beyond the stoichiometrically-pure LCP phase, we also investigated the effect of iron doping on LCP structural features and the corresponding electrochemical properties. The simultaneous effect of iron doping and post-synthesis high-temperature annealing boosts the electrochemical performances in Li cells. The optimized material has been assempled with an high capacity anode based on a Sn-C composite to demostrate the use of an LCP-based material in a complete Li-ion cell.
Highlights
In the last decades, rechargeable lithium-ion batteries have evolved in terms of energy density, cycle life, and reliability [1] to match the increasing requirements of the commercial applications
Here we illustrate the effect of the use of different Co2+ sources, solution acidity, and reaction time on the crystal growth of the LCP particles by means of a multi-technique approach and we report the corresponding performances in lithium cells
The amount of sucrose has always been set in respect to the cobalt precursor with a molar ratio Co2+:sucrose = 1:0.03
Summary
Rechargeable lithium-ion batteries have evolved in terms of energy density, cycle life, and reliability [1] to match the increasing requirements of the commercial applications (i.e., portable electronics, power tools). Further advance is needed in order to go beyond the typical application markets of Li-ion cells. A successful massive implementation of these energy storage devices in electric vehicles requires a huge jump in the performance, safety, and calendar life [2]. One way to increase battery energy is the use of high-voltage cathode materials [3]. Olivine compounds (LiMPO4) are interesting cathode materials for lithium-ion batteries: LiFePO4. (LFP) is commonly used in commercial Li-ion cells [4].
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
