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Li-ion batteries have polymeric binder in their electrodes resulting in high internal resistance and hence long charge times and compromised product lifetime. We have developed Li-ion batteries utilizing binder-free NMC cathodes containing carbon nanotube (CNT). Our proprietary processing of CNT into viscous organic or water-based slurry without surfactant or dispersant reduces or eliminates the need for organic binder and carbon black additives in these cathodes. The benefits of incorporating our processed CNT slurry into NMC cathode electrodes are realized by significant gains in specific energy and power. When the organic binder in the cathode is completely removed, our Li-ion batteries retain superior performance metrics over conventional binder-containing cells, including significantly reduced impedance (-31%) and increased capacity (5%). Li-ion pouch cells containing these binder-free NMC/CNT cathodes show 2.5% higher specific energy. Our cells with binder-free cathode complete 500 cycles with 50% less capacity fade than cells with binder, and display more than 2x improvement in capacity at 10C rate discharge. A processing advantage of eliminating the polymeric binder from the formulation mix was demonstrated by the use of IPA as dispersing solvent in place of the costlier and toxic NMP solvent. Li-ion cells containing binder-free NMC/CNT cathodes from IPA mix preserved their performance advantages over conventional NMP-based binder-containing cells. Figure 1

We have developed supercapacitors utilizing electrodes made of binder-free carbon nanotube (CNT) / activated carbon (AC) composites. Due to the absence of organic binder our supercapacitors exhibit a significantly higher volumetric capacitance of ~20 F/cc compared to conventional supercapacitors while maintaining low resistance. This results in higher energy in the same package or smaller, more compact package size (lower volume) with same energy. Our cells pass 1,000 hour float tests at 2.7V between -35°C and 70°C, as well as high voltage operation at 3V and 70°C. Operation for 100,000 continuous cycles at 85°C was also achieved. Flat format supercapacitor pouch cells > 100 F have been demonstrated that can be integrated into automotive panels for autonomous power. Notable features of our CNT/AC composite supercapacitor technology include: Scalable R2R coating of CNT/AC electrodes without additives. Option of water-based process with no solvent recovery Binder-free CNT/AC electrodes provide 20% higher energy density than conventional AC-based electrodes (50% higher energy density at 3V) CNT/AC supercapacitor technology is 100% packaging agnostic Fabrication of 18650 EDLC cells rated at ~ 100 F demonstrated, and pouch cells rated at ~ 350 F demonstrated The flat pouch-cell format allows installation in automotive panels as power sources for emergency door lock/unlock applications. Figure 1

Electric double layer capacitors (EDLCs) are a category of supercapacitors that generally compliment the performance of batteries through delivery of high power with significantly longer cycle life. The conventional active electrode material utilized in these EDLCs is activated carbon (AC) possessing high surface area through templated porosity. However, one of the primary limitations with AC-based supercapacitors using organic electrolytes is the operational voltage maximum around 2.75 V. Operation at higher voltages that push the 2.75 V barrier is the next essential developmental breakthrough to enable significant boosts to both energy and power densities of supercapacitors. Research into alternative active electrode materials is equally critical to enable and support high voltage operation of supercapacitors. This work demonstrates the fabrication of carbon nanotube (CNT) electrodes from organic-based dispersions without the inclusion of surfactant or binder, and subsequent assembly into supercapacitor devices. The performance of pouch cells assembled from the CNT electrodes and using conventional organic electrolytes at operating voltages ≥ 2.7 V is discussed. A significant and linear voltage dependence of capacitance (~ 3 times higher than AC) was observed for cells with CNT electrodes up to operational voltages ~ 3.5 V, which are currently not achievable using AC-based cells. Repeatable charge-discharge operation of the CNT-based EDLCs was demonstrated at 3.5 V and 70°C, with consequential increase to capacitance by ~ 25 - 30 % compared to 2.7 V operation. Power and energy densities were increased by 1.5 and 2 times respectively at 3.5 V compared to operation at 2.7 V. The performance characteristics from such CNT-based pouch cells were benchmarked against commercial-grade AC supercapacitor devices using organic electrolytes and rated at 2.75 V (single cell). Long-term performance advantages were observed for the CNT-based monocells at 3.5 V and 70°C, which passed 100k cycling tests at full discharge. Under the same test conditions, commercial AC-based cells failed early during the 100k cycling. Response times approaching 2 ms (at -45° phase angle) were also demonstrated with EDLC devices using thin CNT electrodes with 1 mF capacitance. Such EDLC devices may potentially rival aluminum electrolytic capacitors (AECs) for alternating current line-filtering applications, offering significant space savings compared to the bulky AEC components. Finally, the scalable fabrication of binder-free CNT electrodes from surfactant-free dispersion of the material was demonstrated by roll-to-roll, slot-die coating onto an Al foil current collector. The processing of these conformal CNT coatings, assembly into 18650 cylindrical cells, and the resulting EDLC performance characteristics are discussed. The CNT-based 18650 cells had an average capacitance of 7 F at 2.7 V, with low average ESR of 7 mΩ at 1 kHz, and average response time of 120 ms at -45° phase angle. Figure 1

The rapidly increasing technological advances in society place more demands on efficient energy storage and the correspondingly important fast release of the stored energy. Supercapacitors are utilized where energy needs to be stored and released quickly, however they exhibit limitations to these demands that arise from various sources within the device such as the necessary incorporation of resistive additives to the electrode formulation. In the case of activated carbon (AC) electrodes, this constitutes the insulating binder, while for carbon nanotube (CNT) electrodes, the inclusion of appropriate surfactant is almost always necessary to promote stable dispersion for processing. This work discusses the use of surfactant-free and binder-free CNT electrodes for the fabrication of supercapacitor devices. The performance characteristics from pouch cells containing such CNT electrodes in organic electrolytes were benchmarked against commercial-grade AC supercapacitor devices on both cell volume and cell weight bases. EDLC performance advantages realized from eliminating the additives of surfactant and binder were significantly lower ac impedance at low temperature operation (80% reduction @ -30°C), higher capacitance retention after 100,000 cycles, and superior retention of capacitance at high temperature (95% of initial capacitance @ 70°C). The CNT-based supercapacitors of this work exhibited these performance advantages while still maintaining very competitive energy and power densities.