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1. Eye Tear Activated Mg‐Air Battery Driven by Natural Eye Blinking for Smart Contact Lenses

   https://doi.org/10.1002/admt.202200518  

   Pourshaban, Erfan; Banerjee, Aishwaryadev; Karkhanis, Mohit_U; Deshpande, Adwait; Ghosh, Chayanjit; Kim, Hanseup; Mastrangelo, Carlos_H (September 2022, Advanced Materials Technologies)

   Abstract A sliding electrolyte metal‐air microbattery driven by natural eye blinking motion is demonstrated as a source of electrical energy that can be integrated with smart contact lens platforms. The metal‐air battery (footprint 10 mm²) consists of a Mg anode and a Pt cathode, patterned on an insulating substrate and the battery electrolyte is a film of eye‐tear fluid that is periodically dragged on top of the electrodes during the natural eye‐blinking cycle, which activates the battery. When tested with an eye emulator, the open‐circuit voltage across the eye‐tear activated metal‐air battery (ETMAB) is 2.2 V. Impedance matching analysis reveals a maximum battery‐specific capacity of 3561 mAh g^–1obtained at a discharge current density of 5 mA cm^–2. The blinking activated battery exhibits the maximum generated power density of 1.3 mW cm^–2at the load of 740 Ω. The blinking ETMAB delivers eight times higher energy output and more than three times longer lifetime than achievable with static ETMAB designs. 

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2. Self‐Sacrificial Template Synthesis of Fe‐N‐C Catalysts with Dense Active Sites Deposited on A Porous Carbon Network for High Performance in PEMFC

   https://doi.org/10.1002/aenm.202303952  

   Jiao, Li; Arman, Tanvir_Alam; Hwang, Sooyeon; Fonseca, Javier; Okolie, Norbert; Shaaban, Ehab; Li, Gonghu; Liu, Ershuai; Pasaogullari, Ugur; Babu, Siddharth_Komini; et al (April 2024, Advanced Energy Materials)

   Abstract Iron‐nitrogen‐carbon (Fe‐N‐C) single‐atom catalysts are promising sustainable alternatives to the costly and scarce platinum (Pt) to catalyze the oxygen reduction reactions (ORR) at the cathode of proton exchange membrane fuel cells (PEMFCs). However, Fe‐N‐C cathodes for PEMFC are made thicker than Pt/C ones, in order to compensate for the lower intrinsic ORR activity and site density of Fe‐N‐C materials. The thick electrodes are bound with mass transport issues that limit their performance at high current densities, especially in H₂/air PEMFCs. Practical Fe‐N‐C electrodes must combine high intrinsic ORR activity, high site density, and fast mass transport. Herein, it has achieved an improved combination of these properties with a Fe‐N‐C catalyst prepared via a two‐step synthesis approach, constructing first a porous zinc‐nitrogen‐carbon (Zn‐N‐C) substrate, followed by transmetallating Zn by Fe via chemical vapor deposition. A cathode comprising this Fe‐N‐C catalyst has exhibited a maximum power density of 0.53 W cm⁻²in H₂/air PEMFC at 80 °C. The improved power density is associated with the hierarchical porosity of the Zn‐N‐C substrate of this work, which is achieved by epitaxial growth of ZIF‐8 onto g‐C₃N₄, leading to a micro‐mesoporous substrate. 

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3. Probing transport limitations in thick sintered battery electrodes with neutron imaging

   https://doi.org/10.1039/c9me00084d  

   Nie, Ziyang; Ong, Samuel; Hussey, Daniel S.; LaManna, Jacob M.; Jacobson, David L.; Koenig, Gary M. (January 2020, Molecular Systems Design & Engineering)

   null (Ed.)

   Lithium-ion batteries have received significant research interest due to their advantages in energy and power density, which are important to enabling many devices. One route to further increase energy density is to fabricate thicker electrodes in the battery cell; however, careful consideration must be taken when designing electrodes as to how increasing the thickness impacts the multiscale and multiphase molecular transport processes, which can limit the overall battery operating power. Design of these electrodes necessitates probing the molecular processes when the battery cell undergoes electrochemical charge/discharge. One tool for in situ insights into the cell is neutron imaging, because neutron imaging can provide information of where electrochemical processes occur within the electrodes. In this manuscript, neutron imaging is applied to track the lithiation/delithiation processes within electrodes at different current densities for a full cell with a thick sintered Li 4 Ti 5 O 12 anode and LiCoO 2 cathode. The neutron imaging reveals that the molecular distribution of Li + during discharge within the electrode is sensitive to the current density, or equivalently discharge rate. An electrochemical model provides additional insights into the limiting processes occurring within the electrodes. In particular, the impact of tortuosity and molecular transport in the liquid phase within the interstitial regions in the electrodes are considered, and the influence of tortuosity was shown to be highly sensitive to the current density. Qualitatively, the experimental results suggest that the electrodes behave consistent with the packed hard sphere approximation of Bruggeman tortuosity scaling, which indicates that the electrodes are largely mechanically intact but also that a design that incorporates tunable tortuosity could improve the performance of these types of electrodes. 

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4. LiAlO2/LiAl5O8 thin films derived from flame synthesized nanopowders as a potential electro-lyte and coating materials for all solid-state batteries (ASSBs)

   https://doi.org/DOI:10.1021/acsami.0c13021  

   E. Temeche, S. Indris (July 2020, ACS applied materials interfaces)

   null (Ed.)

   Recently, γ-LiAlO2 has attracted considerable attention as a coating in Li-ion battery electrodes. However, its potential as a Li+ ceramic electrolyte is limited due to its poor ionic conductivity (<10−10 S cm−1). Here, we demonstrate an effective method of processing LiAlO2 membranes (<50 μm) using nanopowders (NPs) produced via liquid-feed flame spray pyrolysis(LF-FSP). Membranes consisting of selected mixtures of lithium aluminate polymorphs and Li contents were processed byconventional tape casting of NPs followed by thermocompressionof the green films (100 °C/10 kpsi/10 min). The sintered greenfilms (1100 °C/2 h/air) present a mixture of LiAlO2 (∼72 wt %)and LiAl5O8 (∼27 wt %) phases, offering ionic conductivities (>10−6 S cm−1) at ambient with an activation energy of 0.5 eV. This greatly increases their potential utility as ceramic electrolytes for all-solid-state batteries, which could simplify battery designs, significantly reduce costs, and increase their safety. Furthermore, a solid-state Li/Li3.1AlO2/Li symmetric cell was assembled and galvanostatically cycled at 0.375 mA cm−2 current density, exhibiting a transference number ≈ 1. 

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5. Lewis Acid Site Assisted Bifunctional Activity of Tin Doped Gallium Oxide and Its Application in Rechargeable Zn‐Air Batteries

   https://doi.org/10.1002/smll.202202648  

   Nair, Aruna_Narayanan; Sanad, Mohamed_F; Jayan, Rahul; Gutierrez, Guillermo; Ge, Yulu; Islam, Md_Mahbubul; Hernandez‐Viezcas, Jose_A; Zade, Vishal; Tripathi, Shalini; Shutthanandan, Vaithiyalingam; et al (July 2022, Small)

   Abstract The enhanced safety, superior energy, and power density of rechargeable metal‐air batteries make them ideal energy storage systems for application in energy grids and electric vehicles. However, the absence of a cost‐effective and stable bifunctional catalyst that can replace expensive platinum (Pt)‐based catalyst to promote oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) at the air cathode hinders their broader adaptation. Here, it is demonstrated that Tin (Sn) doped β‐gallium oxide (β‐Ga₂O₃) in the bulk form can efficiently catalyze ORR and OER and, hence, be applied as the cathode in Zn‐air batteries. The Sn‐doped β‐Ga₂O₃sample with 15% Sn (Sn_x=0.15‐Ga₂O₃) displayed exceptional catalytic activity for a bulk, non‐noble metal‐based catalyst. When used as a cathode, the excellent electrocatalytic bifunctional activity of Sn_x=0.15‐Ga₂O₃leads to a prototype Zn‐air battery with a high‐power density of 138 mW cm⁻²and improved cycling stability compared to devices with benchmark Pt‐based cathode. The combined experimental and theoretical exploration revealed that the Lewis acid sites in β‐Ga₂O₃aid in regulating the electron density distribution on the Sn‐doped sites, optimize the adsorption energies of reaction intermediates, and facilitate the formation of critical reaction intermediate (O*), leading to enhanced electrocatalytic activity. 

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