Marek Marcinek

Factors Influencing the Quality of Carbon Coatings on LiFePO4

Several LiFePO4/C composites were prepared and characterized electrochemically in lithium half-cells. Pressed pellet conductivities correlated well with the electrochemical performance in lithium half-cells. It was found that carbon structural factors such as sp2/sp3, D/G, and H/C ratios, as determined by Raman spectroscopy and elemental analysis, influenced the conductivity and rate behavior strongly. The structure of the residual carbon could be manipulated through the use of additives during LiFePO4 synthesis. Increasing the pyromellitic acid (PA) content in the precursor mix prior to calcination resulted in a significant lowering of the D/G ratio and a concomitant rise in the sp2/sp3 ratio of the carbon. Addition of both iron nitrate and PA resulted in higher sp2/sp3 ratios without further lowering the D/G ratios, or increasing carbon contents. The best electrochemical results were obtained for LiFePO4 processed with both ferrocene and PA. The improvement is attributed to better decomposition of the carbon sources, as evidenced by lower H/C ratios, a slight increase of the carbon content (still below 2 wt. percent), and more homogeneous coverage. A discussion of the influence of carbon content vs. structural factors on the composite conductivities and, by inference, the electrochemical performance, is included.

Microwave Plasma Chemical Vapor Deposition of Carbon Coatings on LiNi1/3Co1/3Mn1/3O2 for Li-Ion Battery Composite Cathodes

Microwave Plasma Chemical Vapor Deposition of Carbon Coatings on LiNi 1/3 Co 1/3 Mn 1/3 O 2 for Li-ion Battery Composite Cathodes Marek L. Marcinek ab , James W. Wilcox b , Marca M. Doeff bc and Robert M. Kostecki ∗b Environmental Energy Technologies Division c Materials Sciences Division Lawrence Berkeley National Laboratory University of California Berkeley, CA 94720, USA Abstract In this paper, we report results of a novel synthesis method of thin film conductive carbon coatings on LiNi 1/3 Co 1/3 Mn 1/3 O 2 cathode active material powders for lithium-ion batteries. Thin layers of graphitic carbon were produced from a solid organic precursor, anthracene, by a one-step microwave plasma chemical vapor deposition (MPCVD) method. The structure and morphology of the carbon coatings were examined using SEM, TEM, and Raman spectroscopy. The composite LiNi 1/3 Co 1/3 Mn 1/3 O 2 electrodes were electrochemically tested in lithium half coin cells. The composite cathodes made of the carbon-coated LiNi 1/3 Co 1/3 Mn 1/3 O 2 /C powder showed superior electrochemical performance and increased capacity compared to standard composite LiNi 1/3 Co 1/3 Mn 1/3 O 2 electrodes. Current address: The Warsaw University of Technology, Warsaw, Poland . Electrochemical Society Active Member Corresponding author. E-mail address: r_kostecki@lbl.gov, tel: 00 1 510 486 6002, fax: 00 1 510 486 7303 a b

An Investigation of the Effect of Graphite Degradation on the Irreversible Capacity in Lithium-ion Cells

An Investigation of the Effect of Graphite Degradation on the Irreversible Capacity in Lithium-ion Cells Laurence J. Hardwick * , Marek Marcinek a* , Leanne Beer, John B. Kerr*, Robert Kostecki b,* Environmental Energy Technologies Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA a Electrochemical Society Active Member Present address: The Warsaw University of Technology, Noakowskiego 3, 00-664, Warsaw, Poland b Corresponding author: r_kostecki@lbl.gov, tel: (1) 510 486 6002, fax: (1) 510 486 7303

Fluorine-free electrolytes for all-solid sodium-ion batteries based on percyano-substituted organic salts

A new family of fluorine-free solid-polymer electrolytes, for use in sodium-ion battery applications, is presented. Three novel sodium salts withdiffuse negative charges: sodium pentacyanopropenide (NaPCPI), sodium 2,3,4,5-tetracyanopirolate (NaTCP) and sodium 2,4,5-tricyanoimidazolate (NaTIM) were designed andtested in a poly(ethylene oxide) (PEO) matrix as polymer electrolytes for anall-solid sodium-ion battery. Due to unique, non-covalent structural configurations of anions, improved ionic conductivities were observed. As an example, “liquid-like” high conductivities (>1 mS cm−1) were obtained above 70 °C for solid-polymer electrolyte with a PEO to NaTCP molar ratio of 16:1. All presented salts showed high thermal stability and suitable windows of electrochemical stability between 3 and 5 V. These new anions open a new class of compounds with non-covalent structure for electrolytes system applications.

Studying the Origin and Mechanism of Irreversible Capacity in Lithium-Ion Cells

It has been previously shown that the graphite suffers severe structural damage upon prolonged cycling, as the anode material, in rechargeable lithium-ion batteries [1,2,3]. This is evidenced by the increased prominence of the disorder or D-band (1330 cm) with respect to the graphite or G-band (1580 cm) in the Raman spectrum of graphite anodes from aged Li-ion cells. The observed effect has been seen in Mag-10 [1] and KS-15 [2] graphite and seems to occur generally in all graphitic carbons. In this study we investigated the result of the structural disorder in graphite on the electrochemical behaviour of the anode and its possible implications for the degradation mechanism of Li-ion cells.