Université de Fribourg

A nano-rattle SnO2@carbon composite anode material for high-energy Li-ion batteries by melt diffusion impregnation

Maharajan, Sivarajakumar ; Kwon, Nam Hee ; Brodard, Pierre ; Fromm, Katharina M.

In: Nanomaterials, 2020, vol. 10, no. 4, p. 804

The huge volume expansion in Sn-based alloy anode materials (up to 360%) leads to a dramatic mechanical stress and breaking of particles, resulting in the loss of conductivity and thereby capacity fading. To overcome this issue, SnO2@C nano- rattle composites based on < 10 nm SnO2 nanoparticles in and on porous amorphous carbon spheres were synthesized using a silica template and tin melting...

Université de Fribourg

Li0.5Ni0.5Ti1.5Fe0.5(PO4)3/C electrode material for lithium ion batteries exhibiting faster kinetics and enhanced stability

Srout, Mohammed ; Kwon, Nam Hee ; Ben Youcef, Hicham ; Semlal, Nawal ; Fromm, Katharina M. ; Saadoune, Ismael

In: ACS Applied Materials & Interfaces, 2020, vol. 12, no. 16, p. 18496–18503

Natrium super ionic conductor (NASICON) materials providing attractive properties such as high ionic conductivity and good structural stability are considered as very promising materials for use as electrodes for lithium- and sodium-ion batteries. Herein, a new high-performance electrode material, Li0.5Ni0.5Ti1.5Fe0.5(PO4)3/C, was synthesized via the sol–gel method and was...

Université de Fribourg

Surface modifications of positive-electrode materials for lithium ion batteries

Kwon, Nam Hee ; Conder, Joanna ; Srout, Mohammed ; Fromm, Katharina M.

In: CHIMIA International Journal for Chemistry, 2019, vol. 73, no. 11, p. 880–893

Lithium ion batteries are typically based on one of three positive-electrode materials, namely layered oxides, olivine- and spinel-type materials. The structure of any of them is 'resistant' to electrochemical cycling, and thus, often requires modification/post- treatment to improve a certain property, for example, structural stability, ionic and/or electronic conductivity. This review...

Université de Fribourg

New Ni0.5Ti2 (PO4)3@C NASICON-type electrode material with high rate capability performance for lithium-ion batteries: Synthesis and electrochemical properties

Srout, Mohammed ; Kwon, Nam Hee ; Luo, Wen ; Züttel, Andreas ; Fromm, Katharina M. ; Saadoune, Ismael

In: ChemSusChem, 2019, vol. 12, no. 21, p. 4846–4853

Ni0.5Ti2(PO4)3/C NASICON‐type phosphate is introduced as a new anode material for lithium‐ion batteries (LIBs). Ni0.5Ti2(PO4)3/C was synthesized through the sol–gel route and delivered some remarkable electrochemical performances. Specifically, the Ni0.5Ti2(PO4)3/C electrode demonstrates a high rate capability performance and delivers high reversible capacities ranging from...

Université de Fribourg

Early-stage sustainability evaluation of nanoscale cathode materials for lithium ion batteries

Hischier, Roland ; Kwon, Nam Hee ; Brog, Jean?Pierre ; Fromm, Katharina M.

In: ChemSusChem, 2018, vol. 11, no. 13, p. 2068–2076

Results of an early-stage sustainability evaluation of two development strategies for new nanoscale cathode materials for Li-ion batteries are reported: (i) a new production pathway for an existing material (LiCoO2) and (ii) a new nanomaterial (LiMnPO4). Nano-LiCoO2 was synthesized by a single-source precursor route at a low temperature with a short reaction time, which results in a smaller...

Université de Fribourg

Characteristics and properties of nano-LiCoO2 synthesized by pre-organized single source precursors: Li-ion diffusivity, electrochemistry and biological assessment

Brog, Jean?Pierre ; Crochet, Aurélien ; Seydoux, Joël ; Clift, Martin J. D. ; Baichette, Benoît ; Maharajan, Sivarajakumar ; Barosova, Hana ; Brodard, Pierre ; Spodaryk, Mariana ; Züttel, Andreas ; Rothen?Rutishauser, Barbara ; Kwon, Nam Hee ; Fromm, Katharina M.

In: Journal of Nanobiotechnology, 2017, vol. 15, p. 58

LiCoO₂ is one of the most used cathode materials in Li-ion batteries. Its conventional synthesis requires high temperature (>800 °C) and long heating time (>24 h) to obtain the micronscale rhombohedral layered high-temperature phase of LiCoO₂ (HT-LCO). Nanoscale HT-LCO is of interest to improve the battery performance as the lithium (Li⁺) ion pathway is expected to be shorter in...

Université de Fribourg

Nanoparticle shapes of LiMnPO4, Li+ diffusion orientation and diffusion coefficients for high volumetric energy Li+ ion cathodes

Kwon, Nam Hee ; Yin, , Hui ; Vavrova, Tatiana ; Lim, Jonathan H-W. ; Steiner, Ullrich ; Grobéty, Bernard ; Fromm, Katharina M.

In: Journal of Power Sources, 2017, vol. 342, p. 231–240

Nanoparticles of LiMnPO₄ were fabricated in rod, elongated as well as cubic shapes. The 1D Li⁺ preferred diffusion direction for each shape was determined via electron diffraction spot patterns. The shape of nano-LiMnPO₄ varied the diffusion coefficient of Li⁺ because the Li⁺ diffusion direction and the path length were different. The particles with the shortest dimension along the...

Université de Fribourg

Impact of composite structure and morphology on electronic and ionic conductivity of carbon contained LiCoO2 cathode

Kwon, Nam Hee ; Yin, Hui ; Brodard, Pierre ; Sugnaux, Claudia ; Fromm, Katharina M.

In: Electrochimica Acta, 2014, vol. 134, p. 215–221

Cathodes in lithium ion batteries consist of an ionic conductor, an electronic conductor and a binder in order to make a composite that is both electronically and ionically conductive. The carbon coating on the cathode material plays a critical role for the electrochemical properties of lithium ion batteries due to the increased electronic conductivity. We explain the relationship between the...

Université de Fribourg

The effect of carbon morphology on the LiCoO2 cathode of lithium ion batteries

Kwon, Nam Hee

In: Solid State Sciences, 2013, vol. 21, p. 59–65

Conductive carbon coatings on cathode materials play a critical role in the electrochemical performance of lithium ion batteries due to the increased electronic conductivity and the protective effect of the organic electrolyte on the cathode material. The composite structure of a cathode depends on the physicochemical properties of the carbonaceous materials. We investigated several types of...

Université de Fribourg

Enhanced electrochemical performance of <30 nm thin LiMnPO4 nanorods with a reduced amount of carbon as a cathode for lithium ion batteries

Kwon, Nam Hee ; Fromm, Katharina M.

In: Electrochimica Acta, 2012, vol. 69, p. 38-44

5–10 nm thin rod shaped LiMnPO₄ nanoparticles are synthesized by an improved thermal decomposition method. The synthesis parameters such as the concentration of surfactants, reaction temperature and time, as well as the presence of a solvent play a critical role in the formation of spherical, thin or thick nanorods, and needle-shaped particles of LiMnPO₄. A washing procedure to efficiently...