Talga's patent application: WO2020261194A1SILICON AND GRAPHITE CONTAINING COMPOSITE MATERIAL AND METHOD FOR PRODUCING SAME describes the process of producing silicon/carbon composites between 1 and 40 microns such as could be used in the 4680 battery.
Few layer graphene is produced during the milling of the graphite with the silicon. .
[0087] ... The process 10 comprises an initial silicon material size reduction step, for example a milling step 14 producing silicon nanoparticles 16, and another size reduction step, for example a milling step 18, in which the silicon nanoparticles are milled in a solvent withgraphite particles 20 to produce each of graphite nanoparticles 22, few-layer graphene 24 and graphene coated silicon nanoparticles 26. The solvent is a non-aqueous solvent, for example isopropyl alcohol. The milling steps 14 and 18 may conveniently be conducted in one or more ceramic bead mills, utilising beads of 500 micron in size.
[0088] The silicon nanoparticles are provided, for example, in the range of about 80 nm - 150 nm. The graphite particles 20 may be provided at a size of less than about 30 micron. In one form of the present invention the graphite particles are provided in the form of pre-exfoliated graphite.
[0089] The process 10 further comprises a processing step 28, for example a spray-drying or mechanofusion step, in which the product of the milling step 18, with the addition of a binder 30, is spray dried or mechanofused to produce secondary particles or composites 32. The binder 30 may be provided in the form of pitch. Alternatively, another organic carbon source may constitute the binder 30. The composites 32 produced by the processing step 28 are, for example, of a size between 1 and 40 micron.
[0090] The process 10 still further comprises a thermal treatment step, for example pyrolysis 34, of the composites 32, by which the binder 30 is converted to amorphous carbon thereby forming a first intermediate composite material 12. The pyrolysis 34 takes place at a temperature of between about 500°C to 700°C.
[0091 ] A further coating is applied to the first intermediate composite material 12 with a binder 36, for example an organic source, to form a second intermediate composite 38. In one form the binder 36 is provided in the form of pitch. The binder 36 may in some forms contain one of, or mixtures of, oxide materials. The oxide materials may for example be AI2O3, T1O2, ZrC>2, BaTiC>3, MgO, CuO, ZnO, Fe2C>3, GeC>2, U2O, MnO, NiO, or Zeolite, or a combination thereof.
[0092] The process 10 still further comprises a further thermal treatment step, for example a pyrolysis step 40, in which the second intermediate composite 38 is pyrolysed and the binder 36 converted to amorphous carbon, thereby forming the composite material 42. The pyrolysis step 40 takes place at a temperature of between 750°C to 1100°C, for example between 800°C to 1000°C.
[0093] Because of the presence of the graphene, FLG and GNP, it is understood by the Applicants that the composite material possesses some elastic properties, which will be helpful to keep the micron size anode composites integrated during expansion (lithiation) and prevent or at least reduce the direct exposure of the silicon surfaces to an electrolyte.
The range of 1 to 40 microns is a catchall, and the actual particles would probably be a smaller range within that range.
TLG Price at posting:
$1.80 Sentiment: Buy Disclosure: Held
(20min delay)