Solid-state Graft Copolymer Electrolytes for Lithium Battery Applications

The overall goal of this procedure is to build solid polymer lithium batteries. First, use a free radical polymerization approach to synthesize a graft polymer, then coat the cathode with lithium powders. Proceed to coat the solid polymer on both the cathode and lithium metal anode.

Now assemble the cathode and anode into a full cell. The conductivity test is used to show that the solid polymer can function as an electrolyte. We first had the idea for this method because we wanted to improve the wetting between the cathode particles and the polymer electrolyte.

And we did this by using the polymer also as the cathode binder To synthesize the cathode mix. Ball milled lithium iron phosphate powders with carbon black and dissolve the mixture in the graft copolymer electrolyte solution at a weight ratio of five to one to one heat the slurry to 80 degrees Celsius with open cap under continuous stirring. Then sonicate and magnetically stir the slurry to ensure proper mixing.

Now, doctor blade the slurry at a loading factor of 10 milligrams per centimeter squared onto the aluminum foil. Dry the composite cathode in a vacuum oven at 80 degrees Celsius overnight to remove any residual tetra hydro and moisture. Transport the composite cathode into an argon filled glove box to a high precision electrode cutter punch, 1.4 centimeter squared small discs.

Then drop cast pure GCE solution onto the electrode discs to form the electrolyte layer. Heat the final cathode electrolyte discs on a hot plate inside the glove box with a dew point of 80 degrees Celsius to evaporate the THF. Now with a manual closing tool, assemble the CR 2 0 3 2 coin cells along with equal sized GCE coated metallic lithium discs.

To compare the performance, assemble a second set of cells comprised of the same lithium iron phosphate powders and lithium metal anode. But use A-P-V-D-F binder resin, A-P-V-D-F separator and a liquid electrolyte of one molar lithium hexa fluoro phosphate in an EC to DMC ratio of one. Now perform the cycling tests at ambient temperature using a 32 channel Mac 4, 000 battery tester.

Lithium based batteries have higher energy densities than lead acid, nickel, cadmium, and nickel metal hydride batteries. A full lithium ion battery consists of a cathode and anode, an electrolyte and a separator. The electrolyte affects the overall power capability due to impedance, both through the electrolyte itself and at the electrode electrolyte interfaces.

In this example, the two monomers, POEM and PDMS were used to synthesize a graft copolymer with a final molecular weight of 500, 000 grams per mole. The coin cell was assembled as depicted in this schematic showing gray particles of lithium iron phosphate, black particles of carbon, blue spaghetti, GCE, and an anode of lithium metal. Unlike in liquid, the transport of ions along polymer chains must overcome two activation barriers.

The salvation of the ions by the coordinating EO units has our hest dependence and the segmental motion of the polymer has VLE Toman vulture dependence. These data of cell cycling performance at room temperature show the charge and discharge profiles of cells with conventional liquid electrolyte at 15 milliamps per gram and graft copolymer electrolyte binder at 10 milliamps pergram. As expected, the discharge voltage profiles of the solid polymer cells are temperature dependent at different discharge currents.

The discharge voltage profiles can be plotted as functions of specific capacity. Note that at higher temperatures there is better performance. The energy densities at different power densities can be presented as a ragone plot for polymer and liquid electrolyte batteries.

Note the solid polymer batteries operate safely at high temperatures Following this procedure. Other methods like countering and particle size analysis can be used to answer additional questions like the poros osteo of the cathodes and the effect of particle size on the overall battery variability.