An official website of the United States government
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.
more »
« less
Perspective—Expected Variation in Reported Coin Cell Capacities Due to Current Collector Mass Distribution
Recently publications have suggested best practices with regards to techniques and reporting for battery research. One area gaining attention is the need for battery cell replicates. In this perspective, the need for replicates is put into the context of the uncertainty in gravimetric capacity resulting from a component typically assumed as a constant—the current collector mass. The expected variation in reported gravimetric capacity just due to this factor for representative current collectors and battery materials will be discussed, and the additional importance of electrode loading to minimize the impact of this factor will be described.
more »
« less
- Award ID(s):
- 1652488
- PAR ID:
- 10303600
- Publisher / Repository:
- The Electrochemical Society
- Date Published:
- Journal Name:
- Journal of The Electrochemical Society
- Volume:
- 167
- Issue:
- 12
- ISSN:
- 0013-4651
- Page Range / eLocation ID:
- Article No. 120529
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
Hydrated vanadium pentoxide (VOH) can deliver a gravimetric capacity as high as 400 mA h g −1 owing to the variable valence states of the V cation from 5+ to 3+ in an aqueous zinc ion battery. The incorporation of divalent transition metal cations has been demonstrated to overcome the structural instability, sluggish kinetics, fast capacity degradation, and serious polarization. The current study reveals that the catalytic effects of transition metal cations are probably the key to the significantly improved electrochemical properties and battery performance because of the higher covalent character of 55% in the Cu–O bond in comparison with 32% in the Mg–O bond in the respective samples. Cu( ii ) pre-inserted VOH (CuVOH) possesses a significantly enhanced intercalation storage capacity, an increased discharge voltage, great transport properties, and reduced polarization, while both VOH and Mg( ii ) pre-inserted VOH (MgVOH) demonstrate similar electrochemical properties and performances, indicating that the incorporation of Mg cations has little or no impact. For example, CuVOH has a redox voltage gap of 0.02 V, much smaller than 0.25 V for VOH and 0.27 V for MgVOH. CuVOH shows an enhanced exchange current density of 0.23 A g −1 , compared to 0.20 A g −1 for VOH and 0.19 A g −1 for MgVOH. CuVOH delivers a zinc ion storage capacity of 379 mA h g −1 , higher than 349 mA h g −1 for MgVOH and 337 mA h g −1 for VOH at 0.5 A g −1 . CuVOH shows an energy efficiency of 72%, superior to 53% for VOH and 55% for MgVOH. All of the results suggest that pre-inserted Cu( ii ) cations played a critical role in catalyzing the zinc ion intercalation reaction, while the Mg( ii ) cations did not exert a detectable catalytic effect.more » « less
-
Sulfur and selenium based rechargeable batteries have attracted great attention due to their high gravimetric/volumetric energy densities owing to multielectron conversion reactions. Over the last few years, rationally designed nanomaterials have played a crucial role in the continuous growth of these battery systems. In this context, electrospun nanostructures are of paramount interest for the development of these rechargeable secondary batteries due to their high surface area to volume ratio and good mechanical stability. Here, a systematic and comprehensive review of the recent advances in the development of electrospun nanostructures as novel materials for next generation sulfur and selenium based lithium and sodium batteries is presented. In this review, we highlight the recent progress made in Li–S, RT Na–S, Li–S x Se y , RT Na–S x Se y , Li–Se and RT Na–Se batteries using electrospun carbon, polymers or heterostructures with tailored textural properties, compositions and surface functionalities (polysulfide trapping capability and catalytic activity) in cathodes, interlayers, separator coatings, and electrolyte membranes. The emphasis is placed on various synthesis strategies to design advanced electrospun nanostructures with tunable structural properties and the impact of these features on capacity, rate capability and long-term cycling. Moreover, we have introduced the ‘fraction of (electrochemically) active cathode (FAC)’ as a parameter to highlight the advantages of free-standing electrospun nanostructures compared to their non-electrospun or slurry-cast electrospun counterparts. Furthermore, current challenges and prospects in the use of electrospun nanostructures in each battery system are also discussed. We believe that this review will provide new opportunities in the field of advanced sulfur and selenium based rechargeable batteries using electrospun nanostructures.more » « less
-
Uwe Sauer, Dirk (Ed.)ABSTRACT State of Charge (SoC) and discharge capacity of the batteries are parameters that cannot be determined directly from the battery monitoring and control system and requires estimation. Current and voltage sensors have inherent error and delay leading to inaccurate measurements leading to inaccurate SoC and discharge capacity estimations. These sensors also have an additional cost to the battery system. This paper proposes a sensorless approach to estimate parameters of Vanadium Redox Flow Batteries (VRFBs) for both CC and CV charging methods by estimating battery current in CV mode and terminal voltage in CC mode. The results of estimations by the sensorless approach show a maximum relative error of 0.0035 in estimating terminal voltage in CC charging and a maximum relative error of 0.045 in estimating charging current in CV mode. Furthermore, long- term operation of vanadium redox flow batteries causes ion diffusions across the membrane and the depletion of active materials, which leads to capacity fading in VRFBs and inaccurate SoC estimation. To address the inaccuracy of SoC estimation in the long-term use of the battery, the capacity fading model is also considered for VRFBs in this paper. Experimental results show a 19% electrolyte volume change in the positive and negative tanks after 200 cycles of charge/discharge due to the bulk electrolyte transfer between the positive and negative sides of the battery system. This change of electrolyte volume results in 13.73% capacity fading after 200 cycles of charging/discharging. The SoC also changes by 7.1% after 200 cycles, due to the capacity and electrolyte volume loss, which shows the necessity of considering capacity fading in long-term use of the battery.more » « less
-
In Li–S batteries, the insulating nature of sulfur and Li 2 S causes enormous challenges, such as high polarization and low active material utilization. The nucleation of the solid discharge product, Li 2 S, during the discharge cycle, and the activation of Li 2 S in the subsequent charge cycle, cause a potential challenge that needs to be overcome. Moreover, the shuttling of soluble lithium polysulfide intermediate species results in active material loss and early capacity fade. In this study, we have used thiourea as an electrolyte additive and showed that it serves as both a redox mediator to overcome the Li 2 S activation energy barrier and a shuttle inhibitor to mitigate the notorious polysulfide shuttling via the investigation of thiourea redox activity, shuttle current measurements and study of Li 2 S activation. The steady-state shuttle current of the Li–S battery shows a 6-fold drop when 0.02 M thiourea is added to the standard electrolyte. Moreover, by adding thiourea, the charge plateau for the first cycle of the Li 2 S based cathodes shifts from 3.5 V (standard ether electrolyte) to 2.5 V (with 0.2 M thiourea). Using this additive, the capacity of the Li–S battery stabilizes at ∼839 mA h g −1 after 5 cycles and remains stable over 700 cycles with a low capacity decay rate of 0.025% per cycle, a tremendous improvement compared to the reference battery that retains only ∼350 mA h g −1 after 300 cycles. In the end, to demonstrate the practical and broad applicability of thiourea in overcoming sulfur-battery challenges and in eliminating the need for complex electrode design, we study two additional battery systems – lithium metal-free cells with a graphite anode and Li 2 S cathode, and Li–S cells with simple slurry-based cathodes fabricated via blending commercial carbon black/S and a binder. We believe that this study manifests the advantages of redox active electrolyte additives to overcome several bottlenecks in the Li–S battery field.more » « less
