EV batteries should be able to operate at higher C-rates (1C to 10C typical) for short periods of time, when more power is needed. The performance of the battery depends on multiple parameters: e.g., electrode loading, electrode electronic conductivity, electrode density/porosity, electrode thickness, electrolyte ionic conductivity, separator porosity/tortuosity, etc. To combine high energy density and the power performance (high C-rate) these parameters should be optimized. We have developed a new type of self-standing composite materials consisting of powdered materials embedded into a 3-dimensional network of pristine individual or a few-bundled single wall carbon nanotubes (SWNTs) [1]. The resulted composite materials typically are mechanically robust and with electronic conductivity 10 1 -10 5 S/m, depending on the material composition, density and environment. We have been using this technology to create composites of Li-ion battery materials for self-standing, binder and collector free battery electrodes. Application of these electrodes allows to increase battery energy density up to 40% and increase specific energy up to 70% in flexible pouch cells [1]. The electrode composite material can be produced with various thicknesses, including very thick (up to 3 mm) and highly loaded with active material (up to 350 mg active material /cm 2 ). We will present the dependence of the high C-rate performance of the cells on the electrode density/porosity and electrode thickness with fixed cathode areal loading and conductivity (proportional to the density of CNTs in the material). Cells with electrodes with the density in the 1.5-2 g/cm 3 range demonstrate the best C-rate performance in the 3C to 30C range in full cells vs. graphite anode. Dependence of the battery cell C-rate performances on electrode loadings and densities, and nanotube concentrations as well as the role of the ionic conductivity will be discussed. A. Kuznetsov, S. Mohanty, E. Pigos, G. Chen, W. Cai, A.R. Harutyunyan, High energy density flexible and ecofriendly lithium-ion smart battery. Energy Storage Materials , 2023 ( 54 ) 266-275, ISSN 2405-8297, doi.org/10.1016/j.ensm.2022.10.023

Reliable performance and extensive lifespan of EV batteries are crucial for vehicle dependability and safety. Typical EV battery modules consist of hundreds or even thousands of cells, and undetected flaw in even one of them leads to reduced performance and shorter lifespan of the entire module and could even result in catastrophic failures. Advance detection of battery problems and failures would be important for making technology safer, more efficient, and durable. While some of faulty cells are detected and rejected by current quality control methods at the production, formation, and aging stages, some of the defective cells do pass through and could lead to negative outcomes. Developing more comprehensive methods of battery health monitoring and problem detection, both at the production and the utilization stages of a battery life, is of great interest for the industry. Accurate monitoring of the battery state of charge (SoC) during the battery utilization allows optimization of the charge/discharge profiles and could extend battery life by up to 10%, but current monitoring methods lack reliability. Recent advances in magnetic sensing technology create opportunities to characterize and enhance the performance of electronic devices via magnetic current imaging (MCI). Quantum magnetometers based on nitrogen-vacancy (NV) centers operate at room temperature and are capable of detecting leakage magnetic fields from the currents passing through the battery structures during charge/discharge. Scanning of the magnetic sensor in the vicinity of the battery cell yields a map of the vector magnetic field distribution. The custom software then converts the measured magnetic field distribution into a detailed image of the distribution of the current density in the cell structures, and thereby can provide the unique insight about battery conditions and performance evolution. The same technique can also be useful for measuring SoC with high accuracy. EuQlid has developed a quantum diamond microscope (QDM) for magnetic current imaging. This system can operate in a serial scanning mode with an ensemble NV diamond sensing element, with spatial resolution of 100 µm, and high sensitivity (< 1 nT×s 1/2 ) for imaging current sources at larger standoff distance. Intact, new batteries with traditional commercial electrodes with several designs have been scanned by the QDM. The vector magnetic field distribution around the batteries has been mapped, and based on it, the current density distribution inside each battery has been reconstructed, including total amplitude, and X- and Y- components. The reconstructed current patterns in the batteries based on the QDM measurements match well with the theoretical predictions for each type of battery design (number of layers, electrode arrangement, tab positions) and battery state (idle, charging, discharging), clearly demonstrating the potency of the quantum microscope magnetometer for such measurements. Batteries with intentionally introduced defects (“bold” spots on electrodes, delaminations, cuts, metal inclusions, bad welds, etc.) were also produced and scanned by QDM. The current density distributions in the defective batteries were compared with that in intact batteries of the same design. The results suggest that QDM magnetometry is a promising technique for battery structural health monitoring.

Our group have developed a new type of composite materials consisting of powdered materials embedded into a 3-dimensional network of un-bundled and low-bundled carbon nanotubes [1]. A wide selection of powdered materials can be used, and CNT content can be varied in a broad range. The CNT network uniformly envelops powder particles, has high surface area and numerous chemically active sites, therefore it has good mechanical, electrical and chemical contacts with them thanks to our proprietary technology of growing the material from a mixture of aerosols of pristine nanotubes and the particles. Such uniform dispersion of the particles within the CNT network and good network-particle interface is impossible to achieve by any other synthesis method which uses either pre-made nanotubes or CNT aerogel. These materials are mechanically stable and have good electronic conductivity (10 1 -10 5 S/m, depending on the material composition, density, and environment). The composites have unique mechanical (e.g., anomaly high Poisson’s ratio) and electromechanical properties: e.g., high piezoresistivity. We have been using this technology to create composites of Li-ion battery materials for self-standing battery electrodes. Application of these electrodes allows to increase battery energy density up to 40% by eliminating current collectors, binders and other electrochemically inactive components, and result in batteries with good high C-rate performance, making such battery architecture attractive for EV/EVTOL batteries. Remarkably, the free-standing electrodes can also serve as “built-in” sensors for operando monitoring of battery health utilizing their intrinsic piezoresistivity of SWNTs network, making the batteries “smart”, capable of monitoring battery condition throughout its lifecycle. We have demonstrated that such sensors can detect mechanical bending or stretching of the battery. Possibility of using these self-standing binder and current collector free electrodes for operando sensing of the battery temperature, internal/external pressure, overcharge/overdischarge, electrolyte decomposition and gas evolution in the battery, especially in large EV batteries will be presented. A. Kuznetsov, S. Mohanty, E. Pigos, G. Chen, W. Cai, A.R. Harutyunyan, High energy density flexible and ecofriendly lithium-ion smart battery. Energy Storage Materials, 2023 (54) 266-275, ISSN 2405-8297, doi.org/10.1016/j.ensm.2022.10.023

Novel type of composite materials consisting of powdered materials embedded into a 3-dimensional network of pristine individual or a few-bundled single wall carbon nanotubes (SWNTs) has been developed [1]. A wide selection of powdered materials can be used, and SWNT content can be varied in a broad range. The resulted composite materials typically are self-standing, mechanically robust and with electrical conductivity 101-105 S/m, depending on the material composition and density. We have been using this technology to create composites of Li-ion battery materials for self-standing, binder and collector free battery electrodes. Application of these electrodes allows to increase battery energy density up to 40% and increase specific energy up to 70% in relatively small flexible pouch cells [1]. Since we can produce electrodes with very high thicknesses and high loadings of the active material, with minimal amount of electrochemically inactive components, we are studying applicability of such electrodes for large EV-sized batteries and for both high energy and high-power applications typical for EV/EVTOL batteries, and what parameters of the electrode material is necessary for such applications. Normally, EV batteries operate at 0.1C to 0.5C, to allow 10 to 2 hours of driving. However, they need to be able to operate at higher C-rates (2C to 10C typical) for short periods of time, when more power is needed for passing, hill climbing, etc. Battery performance for a particular battery chemistry depends on multiple interdependent parameters: electrode loading, electrode electronic conductivity, electrode density/porosity, electrode thickness, electrolyte ionic conductivity and many others. To achieve high energy density of a battery cell its electrodes are compressed as much as possible, and the amount of the electrolyte is minimized. However, this often leads to insufficient ionic conductivity of the electrodes, and, therefore, poor power performance (high C-rate performance). Parameters of electrodes of EV/EVTOL batteries need to be optimized for these applications. Here we concentrate on dependence of the high C-rate performance of the cells on the electrode density/porosity and electrode thickness with fixed cathode areal loading and conductivity (proportional to the CNT percentage). Cells with electrodes with the density in the 1.5-2 g/cm3 range demonstrate the best C-rate performance in the 3C to 30C range. O.A. Kuznetsov, S. Mohanty, E. Pigos, G. Chen, W. Cai, A.R. Harutyunyan, High energy density flexible and ecofriendly lithium-ion smart battery. Energy Storage Materials, 2023 (54) 266-275, ISSN 2405-8297, doi.org/10.1016/j.ensm.2022.10.023

The rapidly growing battery market demands both high energy density and waste-management solutions for the anticipated global annual battery waste of about two million metric tons. To address the energy-environment dilemma, we developed self-standing composite electrodes for Li-ion batteries without electrochemically inactive metal current collectors, additives, and binders, increasing energy density by up to 40%. The electrodes were prepared via in situ mixing of as-grown single-wall carbon nanotubes (SWNTs) with aerosolized electrode active materials, leading to adequate electrical conductivity and mechanical robustness. The SWNT scaffold exhibits a piezoresistive effect, with resistance depending on the voltage-weighted number of inter-nanotube contacts. We exploit this intrinsic piezoresistance of SWNT network for operando self-monitoring of battery structural health. The proposed solution-free battery fabrication technology and architecture eliminates environmentally harmful components and enables recycling by simple mechanical separation, aiming at safety and circular economy.

The need to protect the vulnerable and limited resources that are naturally available while meeting the growing energy demand of the world makes the sustainable development of renewable energy of paramount importance. To address these needs, a new type of battery electrode has been developed at Honda Research Institute (HRI), based on free-standing single-wall carbon nanotube (SWNT) films containing active battery materials as dispersed nanoparticles. The SWNT films provide both mechanical support and electrical conductivity, removing the need for metal electrodes (increasing the energy density of the battery) and binder materials (making the process environmentally friendly). Under cyclic strain, the SWNT-based electrodes show hysteretic behaviors in both stress-strain and electrical resistance-strain relations. The electrical resistance-strain behavior shows a different trend from the previously observed behavior on 2D SWNT films (on elastic substrate). We hypothesize that this change can be attributed to the differences in the SWNT network structures in the 2D and 3D films. To understand the microscopic origin of the hysteresis, we performed coarse-grained molecular statics (CGMS) simulations of the SWNT film. The simulations show that the intrinsic Van der Waals interaction between SWNTs is responsible for the observed robust mechanical properties of the electrodes. In addition, our study also reveals that the sparsity of the 3D morphology results in the current being carried across the simulation box only by a few paths. As a consequence, the resistance hysteresis is governed entirely by the change in the power-carrying capacity of the network due to the breaking and formation of contacts between the SWNTs during loading-unloading. The qualitative nature of the resistance-strain hysteresis can thus be attributed to the rapid formation of inter-nanotube contacts, as the nanotube bundles (elongated by initial loading) buckle during unloading.

Lithium-Sulfur is a long-studied, but yet to be practically implemented battery chemistry which carries a promise of creating high energy density batteries. It uses cheap and abundant materials, but faces major technological challenges. One of the key challenges is that sulfur as the cathode material has negligible electronic conductivity (5x10 -28 S/m), preventing electron exchange in the cathode during battery charge/discharge cycling. The other challenge is the significant (up to 80%) volume changes of sulfur during battery cycling that leads to cracking, delamination, voids formation and loss of electrical contacts, therefore limiting battery durability. To overcome these problems, we have developed a solution-free technology of manufacturing composite self-standing electrodes by in-situ mixing of the aerosolized phases and co-deposition [1]. The electrodes consist of sulfur and catholyte particles imbedded in a 3D network of as grown, pristine single-walled carbon nanotubes. The electrodes are flexible and do not include current collector metal foils or binders. They can be produced up to 1 mm thick, up to 200 mg sulfur /cm 2 loading, or 330 mAh/cm 2 capacity without the loss of the SWCNT network 3D structure. The macroscopic electrical conductivity of the material increases 30 orders of magnitude compared to that of sulfur, and reaches 10 2 -10 4 S/m, depending on the SWCNT concentration. The presence of SWCNT network not only solves the electrical conductivity challenge but also durability issue, since flexible/stretchable SWCNT network accommodates the volume change of the sulfur active particles without disruption of the cathode integrity. The electrodes fabricated by this method are being studied as perspective cathodes for solid-state LiS batteries. A. Kuznetsov, S. Mohanty, E. Pigos, G. Chen, W. Cai, A.R. Harutyunyan, High energy density flexible and ecofriendly lithium-ion smart battery. Energy Storage Materials , 2023 ( 54 ) 266-275, ISSN 2405-8297, doi.org/10.1016/j.ensm.2022.10.023

In addition to recent worldwide renewable energy commitments, advances in electrical vehicle technologies, flexible electronics, smart wearable devices, and internet of things, have contributed to the increasing demand for batteries with a wide range of electrochemical and electromechanical properties. In response, the battery industry has launched intensive research and development efforts in search for new materials, technologies, and concepts. However, these rapid developments give rise to a growing concern on the impact of this industry on Nature. Hence, the rapidly growing battery market demands resolutions for both energy and waste-management challenges in anticipation of about two million metric tons of annual battery waste generated globally. One way to resolve this energy and environment dilemma is by revising the conventional battery architecture to assure both high energy density and efficient recyclability aiming at circular economy. Within this strategy we fabricated self-standing composite electrodes that eliminated electrochemically inactive metal current collectors and binders from the Li-ion battery architecture, increasing energy density up to 40%. These electrodes were prepared via in situ mixing of as-grown single-wall carbon nanotubes (SWNTs) with aerosolized electrode active materials in ratios (≥0.25 wt%) that provide adequate electrical conductivity and mechanical robustness under stretching (≤15%), bending (d≥2 mm) and twisting (θ~180o) cycles. Remarkably, the resultant SWNT scaffold in composite electrodes operates as an intrinsic piezoresistive strain sensor (Gauge Factor ~6.2) that for the first time allows in situ/operando self-monitoring of battery structural health without interfering with electrochemical reactions. Moreover, the developed solution-free fabrication method eliminates hazardous, toxic, and environmentally harmful components and procedures from the electrode production line and allows their recycling by simple sonication and recovering of the active materials. In addition, the absence of current collector foils and binder allows for easy recycling and recovery of the constituent materials by using physical separation methods. These new features not only reduce consumption of the natural resources but also promote the eco-friendly circular economy for batteries.

A sulfonamide-based electrolyte can greatly improve the cycling stability of the commercial LiCoO2 cathode at high cut-off voltages in Li metal||LCO batteries by stabilizing the electrode–electrolyte interfaces on both the anode and cathode.

Rapid development and miniaturization of portable and wearable electronic require compact powering devices with highest possible energy density combined with mechanical flexibility. Li-ion batteries remain most practical energy storage devices. Their energy density can be increased by removing electrochemically dead components such as metal collector foils, binder and additives. We developed novel self-standing collector-, and binder-free electrodes produced by a mixing of battery active materials with as-grown carbon nanotubes in a gas-phase. Resulted composite sheets consisting of the particles of the active material imbedded in the 3-dimentional network of pristine carbon nanotubes. The method allow exploiting particles/flakes of any active materials. Electrodes grown by this method can be up to 2 mm thick and have up to 25 mAh/cm2 areal capacity density (in case of NMC 5:2:3 active cathode material). Electrodes are flexible and stretchable in a wide range of compositions, allowing fabrication of flexible battery cells. Since metal collector foils are not present, the electrodes are naturally two-sided, simplifying manufacturing of stacked cells. Batteries that exploit the electrodes fabricated by this method can power flexible electronics.

Despite many newly proposed concepts and a variety of materials applied, Li-ion batteries remain as the most reliable energy storage system for a broad range of applications. As a result, intense research is underway worldwide for further enhancement of their key parameters such as energy/power densities, charge/discharge rates and safety. These attempts include discovering new cathode/anode materials, electrolytes, additives, binders and optimization of metal collectors. Here we present Li-ion battery based on freestanding anode and cathode electrodes consisting only of active material and single wall carbon nanotubes, eliminating the need of additives, binders and collectors. Since, those components constitute about a 30 % in a battery weight, then it is expect an increase of energy density. Our freestanding electrodes have been obtained, for the first time, by a one-step in situ mixing of the active material powder with pristine carbon nanotubes, providing homogenous mixing, preventing nanotubes bundling, and thereby reducing percolation point of electrical conductivity of obtained electrodes. Controlling this parameter is also important for enhancement of power density. Moreover, our method allows continuous production of freestanding, flexible sheets of electrodes that open new perspectives for powering flexible electronics and sensors/actuators for wearable devices. The results of battery performance, evaluations, and impedance studies depending on C-rates, nanotube concentrations, density of electrodes and their conductivities will be presented for two different configurations: coin and pouch cells for half and full cells, respectively.

There was proposed method of toxic water soluble substances with low concentrations from very large volume of water using suspended ultradisperse magnetocontrollable sorbents. Suspension of particles of magnetocontrollable sorbents mixed with contaminated water. Due to small size and density close to the density of water, the sorbent particles can be a longtime in the water column, carrying out absorption of pollution. Then sorbent particles with absorbed contaminant removed by magnetic or cyclone separation. For natural water bodies (rivers, lakes) magnetic separation seems preferable, since allows the sorbent to remove magnetic particles without removing the natural particles suspended in water (silt, plankton and other non-ferromagnetic impurities). There was proposed design of magnetic separators suitable for very much volume of water and how to use them. There were considered particles types of magnetocontrollable sorbent, applicable for this method. The most promising particles tested in model systems.

We report solar cells with both black Si antireflection and SiO2 surface passivation provided by inexpensive liquid-phase chemistry, rather than by conventional vacuum-based techniques. The best cell efficiency from our first efforts was 16.4 %. Nanoporous black Si antireflection on crystalline Si by aqueous etching promises low surface reflection for high photon utilization, together with lower manufacturing cost compared to vacuum-based antireflection coating. Ag-nanoparticle-assisted black Si etching and post-etching chemical treatment recently developed at NREL enables excellent control over the pore diameter and pore separation. Performance of black Si solar cells, including open-circuit voltage, short-circuit current density, and blue response, has benefited from these improvements. Prior to this study, our black Si solar cells were all passivated by thermal SiO2 produced in a tube furnace. Although this passivation is effective, it is not ideal for ultra-low-cost manufacturing. In this study, we report, for the first time, the integration of black Si with a proprietary liquid-phase deposition (LPD) passivation from Natcore Technology. The Natcore LPD forms a layer of < 10-nm SiO2 on top of the black Si surface in a relatively mild chemical bath at room temperature. We demonstrate black Si solar cells with LPD SiO2 with a spectrum-weighted average reflection lower than 5 %, similar to the more costly thermally grown SiO2 approach. However, LPD SiO2 provides somewhat better surface-passivation quality according to the lifetime analysis by the photo-conductivity decay measurement. Moreover, black Si solar cells with LPD SiO2 passivation exhibit higher spectral response at short wavelength compared to those passivated by thermally grown SiO2. With further optimization, the combination of aqueous black Si etching and LPD could provide a pathway for low-cost, high-efficiency crystalline Si solar cells.

Carbon filaments can be grown using hydrocarbons with either exothermic or endothermic catalytic decomposition enthalpies. By in situ monitoring the evolution of the reaction enthalpy during nanotube synthesis via methane gas, we found that although the decomposition reaction of methane is endothermic an exothermic process is superimposed which accompanies the nanotube growth. Analysis shows that the main contributor in this liberated heat is the radiative heat transfer from the surroundings, along with dehydrogenation reaction of in situ formed secondary hydrocarbons on the catalyst surface and the carbon hydrogenation/oxidation processes. This finding implies that nanotube growth process enthalpy is exothermic, and particularly, it extends the commonly accepted temperature gradient driven growth mechanism to the growth via hydrocarbons with endothermic decomposition enthalpy.

Biodistribution of doxorubicin and ferrocarbon carrier particles in organism during and after magnetically controlled anti-tumor drug delivery and deposition was studied. Animal tests show high concentration of the cytostatic drug in the target zone, while its concentration is three orders of magnitude lower in bloodstream and other organs. A significant depot of the drug remains on the deposited particles days after the procedure. Macrophages actively phagocytose the ferrocarbon (FeC) particles and remain viable long enough to carry them to the lymph nodes.

We considered applicability of acoustic imaging technology for the detection of magnetic microparticles and nanoparticles inside soft biological tissues. Such particles are widely used for magnetically targeted drug delivery and magnetic hyperthermia. We developed a new method of ultrasonic synchronous tissue Doppler imaging with magnetic modulation for in vitro and in vivo detection and visualization of magnetic ultradisperse objects in soft tissues. Prototype hardware with appropriate software was produced and the method was successfully tested on magnetic microparticles injected into an excised pig liver.

A new method was used to measure the fraction of semiconducting nanotubes in various as-grown or processed single-walled carbon nanotube (SWCNT) samples. SWCNT number densities were compared in images from near-IR photoluminescence (semiconducting species) and AFM (all species) to compute the semiconducting fraction. The results show large variations among growth methods and effective sorting by density gradient ultracentrifugation. This counting-based method provides important information about SWCNT sample compositions that can guide controlled growth methods and help calibrate bulk characterization techniques.

Single-walled carbon nanotubes can be classified as either metallic or semiconducting, depending on their conductivity, which is determined by their chirality. Existing synthesis methods cannot controllably grow nanotubes with a specific type of conductivity. By varying the noble gas ambient during thermal annealing of the catalyst, and in combination with oxidative and reductive species, we altered the fraction of tubes with metallic conductivity from one-third of the population to a maximum of 91%. In situ transmission electron microscopy studies reveal that this variation leads to differences in both morphology and coarsening behavior of the nanoparticles that we used to nucleate nanotubes. These catalyst rearrangements demonstrate that there are correlations between catalyst morphology and resulting nanotube electronic structure and indicate that chiral-selective growth may be possible.