milerssliu/battery-device-data-qa huggingface dataset:
Combining the insights derived from the systematic set of experiments detailed in this report along with complimentary results from literature, we have uncovered a new understanding of the mechanisms underlying the growth of columnar lithium metal. A schematic representation of the proposed mechanism linking electrolyte additive concentration, initial SEI formation, and the resulting growth of lithium columns is shown in Fig. 13. The initially pristine, oxide-free copper surface enables the electrocatalytic reduction of HF at ∼2 V vs. Li/Li+ which forms (111) textured LiF deposits a few nanometers in size on the surface. Two morphologically distinct yet functionally equivalent LiF deposit morphologies are possible – uniform yet discontinuous LiF particles decorating the copper surface or a continuous polycrystalline film – with the former being more probable in this system when considering the substrate roughness and LiF crystallite size. This HF reduction and LiF deposition process slows significantly when HF becomes depleted near the interface. Subsequently, as the potential drops below 1 V, solvent molecules are decomposed on the remaining unpassivated surfaces between and/or on top of LiF particles, forming organic reduction products and slowing further reduction of electrolyte species. While the precise morphology of the LiF particle layer could not be directly imaged, both candidate morphologies shown schematically in Fig. 13 would result in an SEI with similar properties and identical effects on lithium nucleation and growth. Interfaces between individual crystalline LiF particles and/or between LiF particles and the amorphous matrix of solvent reduction products in the initial SEI act as fast lithium-ion diffusion pathways. These pathways serve to homogenize the electronic and ionic properties near the copper surface, enabling a high nucleation density of lithium metal as the potential of the working electrode is brought below 0 V vs. Li/Li+ and electrodeposition of the active material begins via an instantaneous nucleation event. High lithium-ion diffusion within the SEI created by these interfaces, which allows for easier movement of lithium ions laterally across the electrode surface, along with the layer being very thin, allow for uniform, lateral growth of the lithium metal deposits until they bump into one another. After lateral growth is inhibited the deposits are restricted to growing vertically, normal to the working electrode, resulting in the highly monodisperse (110) textured columnar morphology observed. The diameter of these lithium columns can be controlled by varying the current density during electrodeposition (Fig. S8†). Indeed, a columnar morphology may be the intrinsically preferred growth mode of lithium metal. However, such growth may be inhibited by the SEI formed in conventional electrolytes without additives due to non-uniform lithium-ion diffusivity and the presence of “hot spots” where preferential deposition occurs, whereas the nanostructured SEI formed in electrolytes with added HF would allow columnar growth to proceed uninhibited.

Question: What's the electrolyte?
In comparison with MnOx, NiO and Co3O4, TiO2 with lower theoretical capacitance has also been tested as an electrode in SCs. For instance, by using TiO2 nanofibers, activated carbon and a PVA–H3PO4 membrane, a solid-state SC was fabricated, which delivered a specific capacitance of 310 F g−1. Recently, Ta-doped TiO2 nanofibers were synthesized through the electrospinning technique. In 1 M H2SO4, the 2% Ta-doped TiO2 nanofibers could deliver nearly two times higher specific capacitance than the undoped TiO2 counterpart (111 F g−1), which was attributed to the enhanced electronic conductivity of TiO2 stemming from the replacement of Ti4+ by Ta5+ in the lattice after doping. In addition to the most studied metal oxides mentioned above, Fe2O3, V2O5 and CuO have also been applied to SCs as electrodes. The first report on a pure iron oxide electrode composed of particles with sizes of 53 nm has demonstrated a specific capacitance of 256 F g−1 in 1 M LiOH. Recently, both interconnected Fe2O3 and V2O5 nanofibers with rich meso-/macro-pores were obtained via electrospinning and subsequent heat treatment. Owing to the hierarchical porous structure that acts as an excellent conductive highway for efficient electronic transfer and ion permeation, the resultant binder-free Fe2O3 and V2O5 electrodes gave specific capacitances of 255 F g−1 and 256 F g−1, respectively, at 2 mV s−1 in 1 M Na2SO4. Moreover, an all-solid-state ASC based on an Fe2O3 negative electrode and V2O5 positive electrode could be operated at up to 1.8 V and displayed a high energy density of 32.2 W h kg−1 at an average power density of 128.7 W kg−1. In 2012, pure electrospun V2O5 nanofibers with different structures have been synthesized and tested in two studies. These pure electrospun V2O5 nanofibers displayed a capacitance of around 200 F g−1 in both the studies. A high specific capacitance of 620 F g−1 (accounting for ∼35% of their theoretical capacitance) at 2 A g−1 in 6 M KOH was reported by Jose et al. for electrospun CuO nanowires in 2014. In another reference, an ASC device based on electrospun CuO nanowires as the anode and AC as the cathode was constructed and provided an enhanced voltage window (1.6 V), specific capacitance (83 F g−1), and threefold higher energy density (29.5 W h kg−1) than the AC-based symmetric capacitor (1.4 V, 33 F g−1, 11 W h kg−1).

Question: What's the cathode?
Answer: AC
In comparison with MnOx, NiO and Co3O4, TiO2 with lower theoretical capacitance has also been tested as an electrode in SCs. For instance, by using TiO2 nanofibers, activated carbon and a PVA–H3PO4 membrane, a solid-state SC was fabricated, which delivered a specific capacitance of 310 F g−1. Recently, Ta-doped TiO2 nanofibers were synthesized through the electrospinning technique. In 1 M H2SO4, the 2% Ta-doped TiO2 nanofibers could deliver nearly two times higher specific capacitance than the undoped TiO2 counterpart (111 F g−1), which was attributed to the enhanced electronic conductivity of TiO2 stemming from the replacement of Ti4+ by Ta5+ in the lattice after doping. In addition to the most studied metal oxides mentioned above, Fe2O3, V2O5 and CuO have also been applied to SCs as electrodes. The first report on a pure iron oxide electrode composed of particles with sizes of 53 nm has demonstrated a specific capacitance of 256 F g−1 in 1 M LiOH. Recently, both interconnected Fe2O3 and V2O5 nanofibers with rich meso-/macro-pores were obtained via electrospinning and subsequent heat treatment. Owing to the hierarchical porous structure that acts as an excellent conductive highway for efficient electronic transfer and ion permeation, the resultant binder-free Fe2O3 and V2O5 electrodes gave specific capacitances of 255 F g−1 and 256 F g−1, respectively, at 2 mV s−1 in 1 M Na2SO4. Moreover, an all-solid-state ASC based on an Fe2O3 negative electrode and V2O5 positive electrode could be operated at up to 1.8 V and displayed a high energy density of 32.2 W h kg−1 at an average power density of 128.7 W kg−1. In 2012, pure electrospun V2O5 nanofibers with different structures have been synthesized and tested in two studies. These pure electrospun V2O5 nanofibers displayed a capacitance of around 200 F g−1 in both the studies. A high specific capacitance of 620 F g−1 (accounting for ∼35% of their theoretical capacitance) at 2 A g−1 in 6 M KOH was reported by Jose et al. for electrospun CuO nanowires in 2014. In another reference, an ASC device based on electrospun CuO nanowires as the anode and AC as the cathode was constructed and provided an enhanced voltage window (1.6 V), specific capacitance (83 F g−1), and threefold higher energy density (29.5 W h kg−1) than the AC-based symmetric capacitor (1.4 V, 33 F g−1, 11 W h kg−1).

Question: What's the anode?
Answer: CuO nanowires
In order to demonstrate their remarkable performance for electrochemical energy storage in portable and wearable electronics, we assembled the flexible quasi-solid-state ARZIBs using the NV NSs@ACC as the cathode together with the Zn NSs@CC anode (deposited Zn nanosheets on CC). Fig. S7a† depicts the crystal structure of Zn NSs@CC, in which all the peaks were in good accordance with those of hexagonal Zn (JCPDS no. 87-0713). Furthermore, the SEM images of Zn NSs@CC are illustrated in Fig. S7b.† It is clearly observed that the Zn nanosheets are uniformly grown on CC. The cycling performance of the as-assembled flexible ZIB at 0.2 A g−1 is depicted in Fig. 6a. The device achieves an initial discharge capacity of 121 mA h g−1 and a reversible capacity of 91 mA h g−1 can be maintained after 50 cycles. Furthermore, it can deliver a specific capacity of 60 mA h g−1 and maintain a stable capacity of 52 mA h g−1 after 1000 cycles with excellent coulombic efficiency (∼100%) at a high current density of 1.0 A g−1 (Fig. 6b), which can be ascribed to the stable 2D ultrathin nanosheets structure and the free-standing feature. The flexible quasi-solid-state ARZIB device was bent into three mechanical states to further evaluate its flexibility (Fig. 6c). As presented in Fig. 6d and e, there are no evident changes in the EIS spectra and capacity decline (>92% retention) under different bending states, demonstrating the extraordinary structural durability of our flexible quasi-solid-state ARZIB devices. As a demonstration of the practical application, two series-connected devices were shown to successfully illuminate a red light-emitting diode (LED, 1.8 V) (inset of Fig. 6e). These significant results indicate that this flexible quasi-solid-state ARZIB device holds potential promise for powering future portable and wearable electronics.

Question: What's the cathode?
Answer: NV NSs@ACC
In order to demonstrate their remarkable performance for electrochemical energy storage in portable and wearable electronics, we assembled the flexible quasi-solid-state ARZIBs using the NV NSs@ACC as the cathode together with the Zn NSs@CC anode (deposited Zn nanosheets on CC). Fig. S7a† depicts the crystal structure of Zn NSs@CC, in which all the peaks were in good accordance with those of hexagonal Zn (JCPDS no. 87-0713). Furthermore, the SEM images of Zn NSs@CC are illustrated in Fig. S7b.† It is clearly observed that the Zn nanosheets are uniformly grown on CC. The cycling performance of the as-assembled flexible ZIB at 0.2 A g−1 is depicted in Fig. 6a. The device achieves an initial discharge capacity of 121 mA h g−1 and a reversible capacity of 91 mA h g−1 can be maintained after 50 cycles. Furthermore, it can deliver a specific capacity of 60 mA h g−1 and maintain a stable capacity of 52 mA h g−1 after 1000 cycles with excellent coulombic efficiency (∼100%) at a high current density of 1.0 A g−1 (Fig. 6b), which can be ascribed to the stable 2D ultrathin nanosheets structure and the free-standing feature. The flexible quasi-solid-state ARZIB device was bent into three mechanical states to further evaluate its flexibility (Fig. 6c). As presented in Fig. 6d and e, there are no evident changes in the EIS spectra and capacity decline (>92% retention) under different bending states, demonstrating the extraordinary structural durability of our flexible quasi-solid-state ARZIB devices. As a demonstration of the practical application, two series-connected devices were shown to successfully illuminate a red light-emitting diode (LED, 1.8 V) (inset of Fig. 6e). These significant results indicate that this flexible quasi-solid-state ARZIB device holds potential promise for powering future portable and wearable electronics.

Question: What's the anode?
Answer: Zn NSs@CC
In this contribution, we propose the use of a small amount of metallic 1T MoS2 nanodots (NDs, 3 wt% of the electrode) as a robust catalyst for advanced LSBs. Electrochemical tests and synchrotron in situ X-ray diffraction (XRD) characterizations demonstrated the strong anchoring and catalytic capability of MoS2 NDs. When MoS2 NDs were integrated with a porous carbon/catholyte, the new cathodes exhibited remarkable battery performance, including a high rate capacity of 8.5 mA h cm−2 at 1C and an impressive capacity retention of 9.3 mA h cm−2 after 300 cycles under a high sulfur loading of 12.9 mg cm−2, an extremely low E/S ratio of 4.6 μL mg−1, and a remarkable sulfur content of 81 wt%. Such high-energy densities delivered under high sulfur loading and lean electrolyte conditions are among the best reported so far for LSBs. Based on DFT calculations, we found that the phase and edge sites were the key to governing the catalytic capability for MoS2. Li2S anchored preferentially at Mo-terminated edges of MoS2 and the electrochemical dissociation occurred toward the surface of the monolayer where Li ions could diffuse faster. Indeed, the metallic 1T MoS2 showed a stronger affinity to polysulfides and a lower activation energy for Li2S than 2H MoS2 at most of the adsorption sites. These findings suggest that the catalytic activity in MoS2 can be maximized by downsizing 2H MoS2 flakes to 1T MoS2 NDs.

Question: What's the cathode?
Answer: MoS2 NDs
(4) Photoelectrocatalysis (PEC): PEC is a special electricity-driven photocatalytic process which could be regarded as a combination of electrocatalysis and photocatalysis. In a typical PEC cell, the photocatalysts are usually immobilized on a conductive substrate as the anode and a bias potential as well as continuous illumination are then applied to the prepared anode to generate functional radicals to remove the contaminants. In particular, it should be mentioned that the separation of photo-induced charge carriers could be significantly enhanced by the utilized bias potential since the electrons generated by photocatalysis follow the electric field to the cathode, which contributes to the reduction of the recombination rate. As a result, the photoelectrocatalytic method would significantly promote the degradation efficiency of the titanate materials. For example, Chang et al. synthesized a Cu2O/titanate composite for photocatalytic and photoelectrocatalytic degradation of ibuprofen. The results indicated that the pseudo-first rate constant could be increased from 0.804 h−1 for photocatalysis to 2.28 h−1 for PEC. Finally, the morphology modulation, trap doping and compositing strategies were also extensively applied in PEC to further enhance the separation of charge carriers, for example, layer stacking (morphology modulation), Fe-modification (trap doping) and ZnO compositing (compositing) could significantly improve the PEC performance compared to that of pristine titanate characterized by the increased photocurrent under illumination.

Question: What's the cathode?
(4) Photoelectrocatalysis (PEC): PEC is a special electricity-driven photocatalytic process which could be regarded as a combination of electrocatalysis and photocatalysis. In a typical PEC cell, the photocatalysts are usually immobilized on a conductive substrate as the anode and a bias potential as well as continuous illumination are then applied to the prepared anode to generate functional radicals to remove the contaminants. In particular, it should be mentioned that the separation of photo-induced charge carriers could be significantly enhanced by the utilized bias potential since the electrons generated by photocatalysis follow the electric field to the cathode, which contributes to the reduction of the recombination rate. As a result, the photoelectrocatalytic method would significantly promote the degradation efficiency of the titanate materials. For example, Chang et al. synthesized a Cu2O/titanate composite for photocatalytic and photoelectrocatalytic degradation of ibuprofen. The results indicated that the pseudo-first rate constant could be increased from 0.804 h−1 for photocatalysis to 2.28 h−1 for PEC. Finally, the morphology modulation, trap doping and compositing strategies were also extensively applied in PEC to further enhance the separation of charge carriers, for example, layer stacking (morphology modulation), Fe-modification (trap doping) and ZnO compositing (compositing) could significantly improve the PEC performance compared to that of pristine titanate characterized by the increased photocurrent under illumination.

Question: What's the anode?
Answer: photocatalysts
Here, RGO serves as a 2D template and the carbon source to form the SiC/RGO nanocomposite by an in situ gas–solid reaction. The introduction of RGO not only reduces the recombination of photogenerated electron–hole pairs, but also promotes the transfer of photoexcited electrons between SiC and Li anode taking advantage of the high conductivity of RGO, which plays a crucial role in improving the performance of Li–CO2 batteries. The synthesis strategy of the SiC/RGO nanocomposite is displayed in Fig. 2a. By the sublimation of the solid Si at a high temperature, a new nucleus is generated on the surface of RGO by a gas–solid reaction (C(s) + Si(g) → SiC(s)), and then spreads around RGO to form a tightly connected SiC nanosheet on RGO. The morphology and the structure of RGO and SiC/RGO nanocomposite were studied by SEM and TEM. As shown in Fig. S1 (ESI†), the bare RGO exhibits a 2D nanosheet morphology. After the carbothermal process, SiC is uniformly distributed on the RGO substrate, presenting a distinct island-in-sea-like morphology (Fig. 2b and c). Furthermore, the elemental distribution of the material was studied by EDS. As shown in Fig. S2,† Si is present only in the island-like region and C exists throughout the test area, which directly proves that the island-like nanosheets observed in SEM and TEM images are SiC. The partial conversion of 2D RGO to the SiC/RGO nanocomposite facilitates the transfer of high energy electrons. The high resolution TEM (HRTEM) images (Fig. 2d) also demonstrate the tight junction between SiC and RGO. Clear lattice fringes with a d-spacing of 0.25 nm on the overlay correspond well to the (111) plane of SiC. It is also possible to distinguish between carbon layers due to the pleated RGO layer in the substrate with an interplanar distance of 0.34 nm. Apart from the enhanced electronic conductivity for the SiC/RGO composites, RGO also plays an important role in enhancing the CO2 adsorption capacity (Fig. S3†), which is beneficial for a higher actual discharge capacity of the cathode.

Question: What's the cathode?
In an another set of experiments, the DPP dyes 1 and 2 were cross-linked with 3 with the classical copper-catalyzed protocol by heating the photoelectrode for 10 minutes at 30 °C in a DMF solution with Cu(SO4)·5H2O, sodium ascorbate in presence of the tris(benzyltriazolylmethyl)amine (TBTA) ligand. The completion of the reaction was confirmed by the ATR-IR spectroscopy (Fig. S25 and S26†). The results of the photovoltaic performances of the solar cells made with the I3−/I− redox couple are gathered in Table S3.† Clearly, the conditions of copper catalyzed Huisgen cycloaddition, although conducted in mild conditions, negatively impact the performances of the solar cells since the PCEs are notably lower than those measured with the thermal crosslinking activation. For TiO2 based solar cells, both Jsc and Voc were diminished upon cross-linking. Interestingly, the performances of photocathodes with NiO are less degraded than those with the photoanodes based on TiO2, because only the Jsc was decreased after copper-catalyzed cross-linking. This result is consistent with the upward shift of the valence band of NiO upon insertion of copper cation into the lattice as it was previously reported. Another possibility, is the presence of remaining Cu(II) salt, which is a paramagnetic metal that could quench the excited state of the dye and consequently diminishes the charge injection quantum yield as shown by Hanson and co-workers.

Question: What's the cathode?
Utilization of ceramic SE based separators is also an interesting strategy that can potentially solve problems associated with the S cathode and Li anode. Thanks to their high shear modulus, both the polysulfide shuttle and the Li dendrite growth can be mechanically suppressed. Among various inorganic ceramic SEs, Li–garnet (LLZO) is of particular interest since it offers a relatively high (electro)-chemical stability with Li metal, a much wider potential window compared to other SEs, and a high shear modulus (61 GPa for LLZO; 4.2 GPa for Li). However, the surface impurities/roughness and brittle nature of LLZO SE restrict its intimate contact with Li and other solid-state cathode materials. With S as the cathode material, the electrode/electrolyte integration will be even more challenging considering the enormous volumetric expansion during the conversion reaction with Li. In this regard, surface modification strategies including the use of thin nanometric layer coatings, and 3D interfacial architectures, or the implementation of polymer, gel and liquid interlayers have been used to keep the electrode|SE contacts intact and stabilize the interfacial ionic transport. Using Li ion conducting gel/liquid interlayers instead of using solid interlayers may prove to be an even better strategy due to their inherent tendency to penetrate through the porous structures and hence to access a greater surface area of the composite cathode.

Question: What's the cathode?
Answer: S
Utilization of ceramic SE based separators is also an interesting strategy that can potentially solve problems associated with the S cathode and Li anode. Thanks to their high shear modulus, both the polysulfide shuttle and the Li dendrite growth can be mechanically suppressed. Among various inorganic ceramic SEs, Li–garnet (LLZO) is of particular interest since it offers a relatively high (electro)-chemical stability with Li metal, a much wider potential window compared to other SEs, and a high shear modulus (61 GPa for LLZO; 4.2 GPa for Li). However, the surface impurities/roughness and brittle nature of LLZO SE restrict its intimate contact with Li and other solid-state cathode materials. With S as the cathode material, the electrode/electrolyte integration will be even more challenging considering the enormous volumetric expansion during the conversion reaction with Li. In this regard, surface modification strategies including the use of thin nanometric layer coatings, and 3D interfacial architectures, or the implementation of polymer, gel and liquid interlayers have been used to keep the electrode|SE contacts intact and stabilize the interfacial ionic transport. Using Li ion conducting gel/liquid interlayers instead of using solid interlayers may prove to be an even better strategy due to their inherent tendency to penetrate through the porous structures and hence to access a greater surface area of the composite cathode.

Question: What's the anode?
Answer: Li
For the emerging potassium-ion energy storage technology, the major challenge is seeking suitable electrode materials with a robust structure and fast kinetics for the reversible insertion/desertion of potassium ions. Here, a pseudocapacitive core–shell heterostructure of titanium oxide/carbon confined into N, P, and S co-doped carbon (TiO2/C@NPSC) is obtained by pyrolyzing a metal–organic framework (MOF) precursor of MIL-125 (Ti) modified by poly(cyclotriphosphazene-co-4,4′-sulfonyldiphenol) polymer. The distinctive structure of TiO2/C@NPSC can effectively buffer the volume variation of TiO2 nano-grains during the charge/discharge process, increase the electron/charge transfer, provide abundant active sites, and boost the pseudocapacitive-dominated K+-storage. Consequently, the TiO2/C@NPSC anode displays superior cyclability and fast kinetics behavior. Upon integrating it with a high capacitance activated carbon cathode derived from another MOF precursor, the as-built potassium-ion hybrid capacitor achieves a high-energy density of 114 W h kg−1 and a power output of 21 kW kg−1. Moreover, in a wide working potential window of 0–4.2 V, the device also maintains over 91.6% of its initial capacity after 10000 cycles, showing a superior cycle stability. Our results are conducive to understanding the importance of anode-engineering for designing advanced PIHCs.

Question: What's the cathode?
Answer: carbon