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Although reliable rechargeable batteries represent a key transformative technology for electric vehicles, portable electronics, and renewable energy, there are few nondestructive diagnostic techniques compatible with realistic commercial cell enclosures. Many battery failures result from the loss or chemical degradation of electrolyte. In this work, we present measurements through battery enclosures that allow quantification of electrolyte amount and composition. The study employs instrumentation and techniques developed in the context of zero-to-ultralow-field nuclear magnetic resonance (ZULF NMR), with optical atomic magnetometers as the detection elements. In contrast to conventional NMR methodology, which suffers from skin-depth limitations, the reduced resonance frequencies in ZULF NMR make battery housing and electrodes transparent to the electromagnetic fields involved. As demonstrated here through simulation and experiment, both the solvent and lithium-salt components of the electrolyte (LiPF6) signature could be quantified using our techniques. Further, we show that the apparatus is compatible with measurement of pouch-cell batteries. 

Zero- to ultralow-field (ZULF) nuclear magnetic resonance (NMR) is a version of NMR that allows studying molecules and their transformations in the regime dominated by intrinsic spin-spin interactions. While spin dynamics at zero magnetic field can be probed indirectly, J-spectra can also be measured at zero field by using non-inductive sensors, for example, optically-pumped magnetometers (OPMs). A J-spectrum can be detected when a molecule contains at least two different types of magnetic nuclei (i.e., nuclei with different gyromagnetic ratios) that are coupled via J-coupling. Up to date, no pure J-spectra of molecules featuring the coupling to quadrupolar nuclei were reported. Here we show that zero-field J-spectra can be collected from molecules containing quadrupolar nuclei with I = 1 and demonstrate this for solutions containing various isotopologues of ammonium cations. Lower ZULF NMR signals are observed for molecules containing larger numbers of deuterons compared to protons; this is attributed to less overall magnetization and not to the scalar relaxation of the second kind. We analyze the energy structure and allowed transitions for the studied molecular cations in detail using perturbation theory and demonstrate that in the studied systems, different lines in J-spectra have different dependencies on the magnetic pulse length allowing for unique on-demand zero-field spectral editing. Precise values for the 15N-1H, 14N-1H, and D-1H coupling constants are extracted from the spectra and the difference in the reduced coupling constants is explained by the secondary isotope effect. Simple symmetric cations such as ammonium do not require expensive isotopic labeling for the observation of J-spectra and, thus, may expand the applicability of ZULF NMR spectroscopy in biomedicine and energy storage. 

Abstract Numerous theories extending beyond the standard model of particle physics predict the existence of bosons that could constitute dark matter. In the standard halo model of galactic dark matter, the velocity distribution of the bosonic dark matter field defines a characteristic coherence time τ c . Until recently, laboratory experiments searching for bosonic dark matter fields have been in the regime where the measurement time T significantly exceeds τ c , so null results have been interpreted by assuming a bosonic field amplitude Φ 0 fixed by the average local dark matter density. Here we show that experiments operating in the T  ≪  τ c regime do not sample the full distribution of bosonic dark matter field amplitudes and therefore it is incorrect to assume a fixed value of Φ 0 when inferring constraints. Instead, in order to interpret laboratory measurements (even in the event of a discovery), it is necessary to account for the stochastic nature of such a virialized ultralight field. The constraints inferred from several previous null experiments searching for ultralight bosonic dark matter were overestimated by factors ranging from 3 to 10 depending on experimental details, model assumptions, and choice of inference framework. 

Solid-state battery technology is motivated by the desire to deliver flexible power storage in a safe and efficient manner. The increasingly widespread use of batteries from mass production facilities highlights the need for a rapid and sensitive diagnostic tool for identifying battery defects. We demonstrate the use of atomic magnetometry to measure the magnetic fields around miniature solid-state battery cells. These fields encode information about battery manufacturing defects, state of charge, and impurities, and they can provide important insights into battery aging processes. Compared with SQUID-based magnetometry, the availability of atomic magnetometers, however, highlights the possibility of constructing a low-cost, portable, and flexible implementation of battery quality control and characterization technology. 

The ever-increasing demand for high-capacity rechargeable batteries highlights the need for sensitive and accurate diagnostic technology for determining the state of a cell, for identifying and localizing defects, and for sensing capacity loss mechanisms. Here, we leverage atomic magnetometry to map the weak induced magnetic fields around Li-ion battery cells in a magnetically shielded environment. The ability to rapidly measure cells nondestructively allows testing even commercial cells in their actual operating conditions, as a function of state of charge. These measurements provide maps of the magnetic susceptibility of the cell, which follow trends characteristic for the battery materials under study upon discharge. In particular, hot spots of charge storage are identified. In addition, the measurements reveal the capability to measure transient internal current effects, at a level of μA, which are shown to be dependent upon the state of charge. These effects highlight noncontact battery characterization opportunities. The diagnostic power of this technique could be used for the assessment of cells in research, quality control, or during operation, and could help uncover details of charge storage and failure processes in cells. 

Hyperpolarized fumarate is a promising agent for carbon-13 magnetic resonance metabolic imaging of cellular necrosis. Molecular imaging applications require nuclear hyperpolarization to attain sufficient signal strength. Dissolution dynamic nuclear polarization is the current state-of-the-art methodology for hyperpolarizing fumarate, but this is expensive and relatively slow. Alternatively, this important biomolecule can be hyperpolarized in a cheap and convenient manner using parahydrogen-induced polarization. However, this process requires a chemical reaction, and the resulting hyperpolarized fumarate solutions are contaminated with the catalyst, unreacted reagents, and reaction side product molecules, and are hence unsuitable for use in vivo. In this work, we show that the hyperpolarized fumarate can be purified from these contaminants by acid precipitation as a pure solid, and later redissolved at a chosen concentration in a clean aqueous solvent. Significant advances in the reaction conditions and reactor equipment allow us to form hyperpolarized fumarate at a concentration of several hundred millimolar, at 13C polarization levels of 30-45%.