Marta Baginska , Benjamin J. Blaiszik , Ryan J. Merriman , Nancy R. Sottos ,

Jeffrey S. Moore , and Scott R. White *

4. Experimental Section

Materials and Equipment : Low-density poly(ethylene) (LDPE, Mw = 4000, m.p. 110 ° C), Brij 76 surfactant, and sodium dodecyl sulfate (SDS), paraffifi n wax (m.p. 58–60 ° C), and n-methylpyrrolidone (NMP) solvent were purchased from Sigma-Aldrich. Xylene was purchased from Fisher Scientififi c. Poly(vinylidene flfl uoride) (PVDF) binder was purchased from Alfa Aesar. Bulk mesocarbon microbead (MCMB) anode material (Enerland), Li(Ni 1/3Co 1/3Mn 1/3)O 2 (Li333) cathode material (Enerland), Celgard 2325 separator material, and 1.2 M LiPF 6 in EC:EMC electrolyte were obtained from Argonne National Laboratory. Anodes were cut to the appropriate size using a 1.27 cm punch purchased from McMaster-Carr. Coated anodes were prepared using a Specialty Coating Systems spincoater. C2032-type coin cell hardware components and the coin cell crimper,with the exception of coin cell case,which were all purchased from Xiamen TMAX Battery Equipments Limited. The thermal testing apparatus includes 50 cP silicone oil (SigmaAldrich), hose clamps, andelectrical leads. All coin cells were cycled using an Arbin BT2000 cycler.

Anode and Separator Coating Methods : Microsphere coated anodes and separators were prepared by spin-coating a microsphere suspension directly onto the graphitic anode substrate or polymer separator. The materials required for preparation of the anodes and separators include the suspension to be spin-coated, Beckton-Dickinson syringes, 18 gauge needles, and a spin-coater apparatus. Using a 1 mL syringe outfi tted with an 18 gauge needle, the suspension (0.075 mL) was deposited onto a spinning anode or separator disk. Once coated, anodes and separators were removed from the spin-coater stage and air-dried for a minimum of 24 h before incorporation into coin cells. Surface coverage was determined gravimetrically by weighing each dried anode and dividing by the anode disk surface area.

Cell Assembly and Testing Method : Coated anodes (or separators) were assembled into coin cells in an argon-fi lled vacuum glove box. The Vacuum glove box was purchased from Xiamen TMAX Battery Equipments Limited. The stackinganode disk, Celgard 2325 separator, 1.2 M LiPF 6 in EC: EMC electrolyte (120 µ L), cathode disk, spacer, and top cap.

After assembly, cells were removed from the glove box and mounted in the cycler for testing. Cells were charged and discharged 3 times at a constant current of ± 1.75 mA. For thermal testing, the cycling program commenced as soon as the cell was fully submerged in oil. The cell was allowed to cycle until it completes 3 full cycles. Voltage after the third cycle is briefl y monitored to confi rm that the cell did not short circuit, but rather shut down. The cell is then removed from the oil, allowed to cool, and removed from the thermal testing clamp. Impedance Testing Method : Coins cells were assembled with various coverages of PE microspheres and tested as described above prior to impedance testing. Impedance testing was performed in a frequency range of 0.05 Hz to 100 kHz using both a CH Instruments Model 660 Electrochemical Workstation and a Schlumberger SI 1260 Impedance/Gain-Phase analyzer.

Profilometry Testing Method : Profi lometry testing was performed on sample uncoated and spin-coated graphite electrodes (dia. 1.27 cm) using a Sloan Dentak 3 surface profi lometer. Measurements were taken at a stylus speed of 2.5 µ m s − 1and over a distance of 4000 µ m.