FLEXODES, INC. — Department of Defense STTR Phase I: AFX20D-TCSO1

Description

Flexodes Lithium Sulfur Technology Technical advantages: Patented technology Tested over 800 cycles in coin and 150 cycles in Pouch cell format Low cost Sulfur used in cathode - NO heavy metals or conflict metals (Co) Projected $80-$90/KWh - significantly lower than current $150-$190/KWh System performance as compared to existing Graphite based NMC/NCA Li Ion                                                                                 Flexodes            Cathode (NCA/NMC/LFP)         140-220 mAh/g             >800 mAh/g Anode (Graphite)                        280-320 mAh/g          1800-2200 mAh/g Gravimetric energy density     200-250 Wh/Kg              350-450 Wh/Kg Volumetric Energy Density      200-600 Wh/L               400-550 Wh/L Areal capacity                              2 mAh/cm2                   >6 mAh/cm2 Voltage                                          3.3 – 3.7 V                  2 V Power                                             100-110 W/Kg          120-140 W/Kg Cycle life(100% DoD)                 300-500                     400-500(tested 800 in coin & 200 in pouch) The theoretical capacity of sulfur cathode is ~1600mAh/g and lithium is ~3800mAh/g  thus giving a potential for over  2500 Wh/Kg Energy Density. Our focused Efforts on material development utilizing our patented CNT foam architecture resulted in a practical performance of sulfur cathode > 800mAh/g and lithium anode >2000mAh/g with improved energy density of 350 – 400 Wh/kg, ~ 1.5-2X that of existing LIBs. Our patented 3D trench–wall CNT framework serves as effective free-standing sulfur/lithium dual hosts. This simultaneously tackles the most crucial challenges in both cathode and anode to achieve a high “cell”-level energy density and power for practical Li-S batteries by increasing the areal loading of sulfur rather than only the specific capacity based on the sulfur mass. The key to achieving the striking improvement is the unique nanotrenches on the wall of CNTs, created without collapsing the free-standing CNT sponge structure using facile and controllable mechanochemical method. The nanotrenches become highly polysulfide-philic and lithio-philic, impeding the polysulfide shuttle especially for a high areal loading of sulfur as well as improving lithium deposition/ stripping. A large reduction in the overpotentials during charge/discharge and improved kinetics resulted in the strikingly high areal capacity as high as 13.3 mAh cm?2 at an areal current density of 1.6 mA cm?2, and maintained at  11.0 mAh cm?2 even with tenfold increase in the current density (16 mA cm?2), suggesting both high “cell-level” energy density and power. The trench–wall CNT is an excellent host material for both cathode and anode, bringing Li-S batteries ready for practical applications. The dual-host design could be utilized in other rechargeable batteries with similar charge/discharge mechanisms.