Nonintrusive thermal-wave sensor for operando quantification of degradation in commercial batteries.

Monitoring real-world battery degradation is crucial for the widespread application of batteries in different scenarios. However, acquiring quantitative degradation information in operating commercial cells is challenging due to the complex, embedded, and/or qualitative nature of most existing sensing techniques. This process is essentially limited by the type of signals used for detection. Here, we report the use of effective battery thermal conductivity (keff) as a quantitative indicator of battery degradation by leveraging the strong dependence of keff on battery-structure changes. A measurement scheme based on attachable thermal-wave sensors is developed for non-embedded detection and quantitative assessment. A proof-of-concept study of battery degradation during fast charging demonstrates that the amount of lithium plating and electrolyte consumption associated with the side reactions on the graphite anode and deposited lithium can be quantitatively distinguished using our method. Therefore, this work opens the door to the quantitative evaluation of battery degradation using simple non-embedded thermal-wave sensors.

Extreme fast charging of commercial Li-ion batteries via combined thermal switching and self-heating approaches.

The mass adoption of electric vehicles is hindered by the inadequate extreme fast charging (XFC) performance (i.e., less than 15 min charging time to reach 80% state of charge) of commercial high-specific-energy (i.e., >200 Wh/kg) lithium-ion batteries (LIBs). Here, to enable the XFC of commercial LIBs, we propose the regulation of the battery's self-generated heat via active thermal switching. We demonstrate that retaining the heat during XFC with the switch OFF boosts the cell's kinetics while dissipating the heat after XFC with the switch ON reduces detrimental reactions in the battery. Without modifying cell materials or structures, the proposed XFC approach enables reliable battery operation by applying <15 min of charge and 1 h of discharge. These results are almost identical regarding operativity for the same battery type tested applying a 1 h of charge and 1 h of discharge, thus, meeting the XFC targets set by the United States Department of Energy. Finally, we also demonstrate the feasibility of integrating the XFC approach in a commercial battery thermal management system.

Unraveling Li growth kinetics in solid electrolytes due to electron beam charging.

Revealing the local structure of solid electrolytes (SEs) with electron microscopy is critical for the fundamental understanding of the performance of solid-state batteries (SSBs). However, the intrinsic structural information in the SSB can be misleading if the sample's interactions with the electron beams are not fully understood. In this work, we systematically investigate the effect of electron beams on Al-doped lithium lanthanum zirconium oxide (LLZO) under different imaging conditions. Li metal is observed to grow directly on the clean surface of LLZO. The Li metal growth kinetics and the morphology obtained are found to be heavily influenced by the temperature, accelerating voltage, and electron beam intensity. We prove that the lithium growth is due to the LLZO delithiation activated by a positive charging effect under electron beam emission. Our results deepen the understanding of the electron beam impact on SEs and provide guidance for battery material characterization using electron microscopy.

Tortuosity Effects in Garnet-Type Li7La3Zr2O12 Solid Electrolytes.

Intrinsic material microstructure features, such as pores or void spaces, grains, and defects can affect local lithium-ion concentration profiles and transport properties in solid ion conductors. The formation of lithium-deficient or -excess regions can accelerate degradation phenomena, such as dendrite formation, lithium plating, and electrode/electrolyte delamination. This paper evaluates the effects pores or void spaces have on the tortuosity of a garnet-type Li7La3Zr2O12 solid electrolyte. Synchrotron X-ray tomography is used to obtain three-dimensional reconstructions of different electrolytes sintered at temperatures between 1050 and 1150 °C. The magnitude of the electrolyte tortuosity and the tortuosity directional anisotropy is shown to increase with sintering temperature. Electrolytes with highly anisometric tortuosity have lower critical current densities. Alignment or elimination of pores within an electrolyte or composite cathode may provide a means for achieving higher critical current densities and higher power densities in all solid-state batteries.

Co3O4/Sm-Doped CeO2/Co3O4 Trilayer Coating on AISI 441 Interconnect for Solid Oxide Fuel Cells.

In this work, a novel Co/Sm-doped CeO2 (SDC)/Co trilayer of ∼6 µm is deposited by alternating electrodeposition and electrophoresis and oxidized to a Co3O4/SDC/Co3O4 trilayer structure. This coating is unique and effective in the following aspects: (1) The area specific resistance of the coated interconnect is more stable and lower than that of the uncoated interconnect after thermal treatment at 800 °C for 400 h. (2) The Co3O4/SDC/Co3O4 coating layer can effectively inhibit Cr diffusion and evaporation and significantly slow the oxidation rate of the interconnect. (3) The Sm0.5Sr0.5Co0.2Fe0.8O3 cathode in the electrolyte/cathode/interconnect half-cell retains its initial stoichiometry after 100 h of the thermal treatment. Subsequently, the ohmic resistance RΩ, high frequency polarization resistance RH, and low frequency polarization resistance RL of the half-cell with the Co3O4/SDC/Co3O4 coated interconnect are all smaller than those of the half-cell with the bare interconnect. The Co3O4/SDC/Co3O4 coating layer has great advantages to be used as a protective layer for the metallic interconnect in solid oxide fuel cells to improve cell performance, stability, and durability.

Quantum dots coupled ZnO nanowire-array panels and their photocatalytic activities.

Fabrication and characterization of a heterojunction structured by CdS quantum dots@ZnO nanowire-array panels were presented. Firstly, ZnO nanowire-array panels were prepared by using a chemical bath deposition approach where wurtzite ZnO nanowires with a diameter of about 100 nm and 3 microm in length grew perpendicularly to glass substrate. Secondly, CdS quantum dots were deposited onto the surface of the ZnO nanowire-arrays by using successive ion layer absorption and reaction method, and the CdS shell/ZnO core heterojunction were thus obtained. Field emission scanning electron microscopy and transmission electron microscope were employed to characterize the morphological properties of the as-obtained CdS quantum dots@ZnO nanowire-array panels. X-ray diffraction was adopted to characterize the crystalline properties of the as-obtained CdS quantum dots@ZnO nanowire-array panels. Methyl orange was taken as a model compound to confirm the photocatalytic activities of the CdS shell/ZnO core heterojunction. Results indicate that CdS with narrow band gap not only acts as a visible-light sensitizer but also is responsible for an effective charge separation.

Photovoltaic activity of ZnO nanorods arrays co-sensitized by CdS and CuInS2 quantum dots.

One-dimensional ZnO nanorods arrays were self-assembly grown on a ZnO thin film, and then CdS quantum dots were deposited on the ZnO nanorods arrays by a successive ionic layer adsorption and reaction process. Scanning electron microscopy and transmission electron microscopy results indicate that the CdS quantum dots can be uniformly deposited on the ZnO nanorods arrays and the thickness of the CdS shell can be controlled through varying the number of the adsorption and reaction cycle. For a typical sample prepared by the adsorption and reaction cycles of 10 times, the thickness of the CdS is about 4.0 nm. Monodispersed CulnS2 quantum dots with a size of 3.5 nm were synthesized by a solvothermal route and then deposited on the ZnO nanorods arrays coated with the CdS quantum dots by using an electrophoretic deposition technique. Optical and electrical properties indicate that the as-fabricated ZnO/CdS/CulnS2 heterojunction structure not only exhibits a high absorption of the incident light in visible region but also can reduce a leakage current as compared to the ZnO/CdS heterojunction structure. Electrical impedance spectroscopy is used to analyze the electrochemical reaction of the interfaces.

Enhanced photocatalytic activity of ZnO microspheres via hybridization with CuInSe2 and CuInS2 nanocrystals.

ZnO microspheres sensitized by CuInSe(2) and CuInS(2) nanoparticles, which were synthesized by a solvothermal method and have a size about 20 and 3.5 nm, respectively, were used to a photodegradation of rhodamine B under an irradiation of mercury lamp. Results show that the photocatalytic activities of the ZnO/CuInSe(2) and the ZnO/CuInS(2) are much higher than that of the ZnO microspheres because of a formation of the heterojunction in two systems. It is also noted that the ZnO/CuInS(2) exhibits a higher photocatalytic activity than the ZnO/CuInSe(2), which is probably related to more suitable band gap to sunlight for CuInS(2) nanocrystals and the larger specific surface due to a small size. Particularly, the ZnO/CuInSe(2)/CuInS(2) shows the highest photocatalytic activities in all measured photocatalysts, which should be attributed to the formation of double heterojunctions among ZnO, CuInSe(2), and CuInS(2).