milerssliu/battery-device-data-qa huggingface dataset:
The determination of metal and polymer material moduli are straightforward and taken from literature values. To verify the estimated moduli of the composite electrodes, they were stacked in various layers and acoustically interrogated. As shown in Fig. 3a, the graphite/Cu electrode has a modulus of 10.7 GPa, and the LiCoO2/Al electrode has a modulus of around 27.8 GPa, as calculated from the measured wave velocities (Fig. 3c) and the respective weighted densities of the double-sided electrodes. These values are slightly higher than the respective Hashin–Shtrikman bounds because the measured electrodes include the metal current collector which has a higher modulus. The values are lower than the single particle graphite or LiCoO2 because the composite electrodes are weighted down by the softer materials. The change in thickness of these individual electrodes during cycling can also be estimated from average peak-to-peak spacing of the intensity line profiles generated from TXM micrographs (Fig. S3†). These peak-to-peak intensities vary because of pouch cell manufacturing tolerances: the electrodes are not perfectly aligned within the cell, causing signal blurring at electrode boundaries. This percent error in thickness calculation is minimized by introducing threshold values for peak discrimination. The results of the peak spacing analysis (Fig. S4†) show that the average single layer expands upon charge and contracts upon discharge, and that the degree of hysteresis grows with current rate. The initial average electrode thickness of 170 μm confirms the ex situ digital caliper measurements of individual electrodes (180 μm for LiCoO2/Al and 200 μm for graphite/Cu) and the moduli estimation of 27.8 GPa for LiCoO2/Al and 10.7 GPa for graphite/Cu. Unfortunately, the differences in thickness changes between LiCoO2/Al and graphite/Cu during cycling are hard to discern due to the imperfect alignment of the electrode layers with the X-ray detector. For future studies, improved spatial resolution at the single electrode length scale would be aided by tests of single-layer pouch cells, where thicknesses of the single anode and cathode could be measured more accurately without stack distortion.

Question: What's the anode?
However, in the extreme case, when Qm of a dual-ion battery cathode is 300 mA h g−1 and the average potential is 5.0 V, Ecorrm is only ∼500 W h kg−1 if KPF6 is used as the supporting salt (Chart 2b). Switching to lighter salts, such as KClO4, KBF4 and particularly KF might significantly boost the energy density (Chart 2c). For potassium fluoride, an Ecorrm of ∼500 W h kg−1 is achieved already at a reasonable ∼200 mA h g−1 and 3.6 V. Optimization of the salt composition, however, has not been reported yet. Considering low solubility of KF in aprotic electrolytes, it is especially intriguing if it may succeed as the supporting salt.

Question: What's the cathode?
Uniform doping has been recognized as an effective approach to improve the cycling performance of many layered cathodes. Herein, we propose non-uniform doping as a more effective approach to enhance the cycling stability of layered cathodes via the precipitation strengthening mechanism. In this work, we investigate four doped (Cu, Ti, Mg, and Zn) P2-layered cathodes for sodium ion batteries and validate that cycling induced dopant segregation can substantially enhance the cyclability due to mitigation of bulk cracking. Our comprehensive analysis indicates that dopant evolution is quite diverse during electrochemical cycling, not only depending on the nature of each dopant but also the cycling conditions applied. The migration and segregation behaviors of inactive dopants demonstrate the complex dynamics within grain bulk during battery cycling, which also offers us chances to engineer the physicochemical properties of layered cathodes. Non-uniform doping opens a new avenue for designing battery materials with superior mechanical properties.

Question: What's the cathode?
Answer: doped (Cu, Ti, Mg, and Zn) P2-layered
To probe the surface chemistry of MoS2 NDs before and after LPS adsorption, XPS measurements were carried out. Fig. S7 (ESI†) shows the deconvoluted Mo 3d and S 2p spectra of the pristine and polysulfides-mixed MoS2 NDs. In comparison with the pristine MoS2 NDs, the Mo 3d peaks of 3d3/2 and 3d5/2 for the MoS2 ND/polysulfide were overall downshifted by ∼0.15 eV, which could be attributed to the intense interaction of the exposed Mo atoms with the surrounding strong electronegative sulfur ligand. In the S 2p spectra, peaks centered at 163.2, 162.6, and 161.3 eV, corresponding to the S 2p1/2 and 2p3/2 components of the original MoS2 ND, were almost intact after mixing with the polysulfides, possibly due to the weak interaction between the S atoms in the MoS2 NDs and polysulfides. Interestingly, new features located at 159.8 and 165.2–169.4 eV appeared for the MoS2 ND/polysulfide, which were considered due to the formation of the polythionate moiety. It is reasonable to deduce that the “sulfiphilic” surface for MoS2 NDs would significantly promote the retention of polysulfides in the cathode region. More importantly, the edge-rich MoS2 NDs increased the Mo–S bridge between the metallic catalyst and polysulfides, propelling electron transfer across the MoS2 NDs to the polysulfides, and thus significantly catalyzing the chemical redox conversion of the polysulfides.

Question: What's the cathode?
Answer: MoS2 NDs
Overall, crosslinking the sensitizers under copper-free conditions lead to an increase of the photovoltaic performances of all the DSSCs with both electrolytes. For NiO photocathodes, the Jsc is decreased owing to most probable iodide association with triazole, but it is compensated with the increase of Voc and ff. Crosslinking of the dyes with copper(I) catalysis is also possible, but the resulting solar cells exhibit lower performances, showing that copper has poisoned the devices.

Question: What's the cathode?
Answer: NiO
Compounds derived from hexaazatriphenylene (HAT) might reversibly accept up to six electrons per HAT unit and have excellent cycling capabilities. They might withstand 10000–50000 cycles with small capacity fading. Kapaev et al. showed that HAT-based polymer P14 delivered a Qm of up to 245 mA h g−1 at 50 mA g−1 in a 0.9–3.4 V vs. K potential range. Interestingly, the reversible capacity continuously increased upon cycling at 10 A g−1 from 150 to 169 mA h g−1 after 4600 cycles. This slow activation, of which the reasons are yet unknown, makes P14 the most stable among all reported cathode materials for non-aqueous K-based batteries. After 4600 cycles, the cells short-circuited due to dendrite formation at the potassium anode.

Question: What's the cathode?
Answer: P14
Volumetric capacity and density are usually unreported for organic materials used in potassium batteries. Density for solid polar organic compounds containing only C, H, N and O ranges between roughly 1.1 and 1.7 g cm−3, and it is smaller than for inorganic cathode materials (calc. 2.3 g cm−3 for KMHCF, calc. 3.1 g cm−3 for KVPO4F, and 3.35 g cm−3 for V2O5 ( )). This limits the applicability of organic cathode materials where the low device volume is crucial, e.g., in portable electronics. However, in some electric vehicles and large-scale stationary applications the volume is supposed to be less restricted.

Question: What's the cathode?
Answer: KMHCF
Volumetric capacity and density are usually unreported for organic materials used in potassium batteries. Density for solid polar organic compounds containing only C, H, N and O ranges between roughly 1.1 and 1.7 g cm−3, and it is smaller than for inorganic cathode materials (calc. 2.3 g cm−3 for KMHCF, calc. 3.1 g cm−3 for KVPO4F, and 3.35 g cm−3 for V2O5 ( )). This limits the applicability of organic cathode materials where the low device volume is crucial, e.g., in portable electronics. However, in some electric vehicles and large-scale stationary applications the volume is supposed to be less restricted.

Question: What's the cathode?
Answer: KVPO4F
High energy density lithium ion batteries have been applied as the main energy storage technology in portable devices and green transportation. LiCoO2, a layered oxide cathode in lithium ion batteries, has obtained unprecedented success since its commercialization in the 1990s. LiNiO2, isostructural to LiCoO2, can deliver a higher capacity within a relatively low upper cutoff voltage. However, its practical application has been hindered due to the inherent structural instability. Thus, cobalt, as an essential element, has been incorporated into the LiNiO2 system to form LiNi1−x−yMnyCoxO2 (NMC) and LiNi1−x−yCoxAlyO2 (NCA) materials to release the strong magnetic moment and ultimately stabilize the structure. At present, researchers are pursuing the theoretical capacity of NMCs either by elevating the high cutoff voltage or increasing the nickel concentration. However, these strategies have inevitably provoked some of the degradation pathways of these materials, including transition metal reduction/dissolution, surface reconstruction, gas evolution, electrolyte oxidation/decomposition, and chemomechanical breakdown. Additionally, most of these materials are synthesized in the polycrystalline form and have heterogeneous chemistry, resulting in high heterogeneous degradation patterns.

Question: What's the cathode?
Answer: LiCoO2
Against this backdrop, the presently reported work focuses on designing a composition (viz., combination of TM- and non-TM-ions) and suitably tuning some structural features of O3-type Na-TM-oxide based cathode materials to address the main issue concerning stability against hydration and also improve the electrochemical cyclic stability, as well as rate capability. While doing so, a strong correlation between the composition, structure, stability against hydration and electrochemical behavior/performance for such oxides has been established. As will be demonstrated, an air/water-stable (despite long-term exposures under stringent conditions) O3-type Na-TM-oxide has been developed, which is devoid of all the problems mentioned above, so much so that it allows the successful development of stable electrodes using a cost-effective and environment/health friendly ‘water based binder’ (i.e., Na-alginate) and water as solvent during electrode preparation (viz., ‘aqueous processing’). To the best of our knowledge, such excellent stability against hydration and electrochemical performance, despite being ‘aqueous-processed’, have not been reported earlier for O3-type Na-TM-oxide based cathodes.

Question: What's the cathode?
Answer: O3-type Na-TM-oxide based
This simple, yet methodical sonication method can be applied to evaluate the surface stability of inorganic materials. In particular, the agglomerated secondary particles require a dispersing process to prepare samples for the TEM analysis. In addition, an extended sonication may be necessary in the cycled electrodes because of the binder usage. Our results have also shown that the surface of layered oxide materials can be easily influenced by the sonication method. Furthermore, our previous study also demonstrated that the cathode surface can be transformed by simply soaking layered oxide powders in organic solvents, including typical electrolyte solvents. With the inherent surface fragility of Ni-rich oxide materials, it is crucial to take cautions in preparing samples for characterization. Alternatively, many studies have applied focused ion beam (FIB) to prepare thin samples for TEM experiments. In this case, the chemical and structural information around grain boundaries can be protected for TEM analysis. However, it is not clear how the surface region may be influenced by the typical FIB coating protection and sample handling.

Question: What's the cathode?
Research focus on cathode materials for LIBs is currently going through a paradigm shift where the previously overlooked disordered rocksalt (DRS) materials are receiving an increasing level of interest. It was reported that Li-rich materials with a high Li-to-TM ratio allow the formation of percolating network with low energy barriers for Li diffusion, which leads to good transport properties while its structural integrity is retained. Several Li-rich transition metal oxides with a DRS structure such as Li1+xTi2xFe1−3xO2 (0 ≤ x ≤ 0.333), Li1.2Ni1/3Ti1/3Mo2/5O2, Li1.2Ti0.4Mn0.4O2, Li1.3Nb0.3Fe0.4O2 ( ) and Li1.3Nb0.43Ni0.27O2 ( ) have been studied, and their high reversible capacities showed a promising prospect of discovering new cathode material in much less explored domain. Li2VO2F is the first Li-rich DRS material where O was partially substituted by F. The substitution increases the performance of the cathode such as discharge capacity and nominal voltage.

Question: What's the cathode?
Answer: Li2VO2F
To achieve aqueous zinc batteries with high capacity and superior durability, developing a scalable and efficient strategy for preparing an outstanding cathode is of pivotal importance. Herein, porous cobalt/nickel composite hydroxides supported on 3D Co–Ni foam (CNF) are used to construct a robust cathode (denoted as UTCNF) via a facile and cost-effective ultrasonic method that is suitable for scaling up to an industrial level. Attributed to the synergistic effects of the 3D foam architecture, the porous structure, and the in situ formation of electrochemically active cobalt/nickel composite hydroxides, the UTCNF//Zn battery exhibits excellent performance with a relatively high capacity (2.13 mA h cm−2 at 8 mA cm−2), excellent rate performance (47% capacity retention from 8 to 50 mA h cm−2), and superb stability (only ∼10% capacity loss after 30000 cycles at a high current density of 40 mA cm−2). Furthermore, a maximum energy density of 3.99 mW h cm−2 and a peak density of 320 mW cm−2 are also attained. Notably, a soft-package battery that uses the UTCNF as a cathode demonstrates great potential as a power supply. This work may provide valuable ideas for the achievement of large-scale aqueous zinc batteries with high performance.

Question: What's the cathode?
Answer: UTCNF
Electrospun NiO with different nanostructures has also been widely studied in SCs. For instance, by electrospinning a PVP/nickel nitrate/citric acid polymer solution followed by a subsequent annealing process to remove PVP, NiO hollow nanofibers comprised of NiO sheets with a diameter of 17 nm were prepared. The resultant NiO nanofibers exhibited a higher pseudocapacitance (336 F g−1 at 5 mA cm−2) than the solid NiO nanofibers fabricated without citric acid (136 F g−1). In another reference, by using electrospun PAA as a sacrificial template, NiO hollow nanofibers consisting of NiO nanoparticles with diameters varying from 10 to 30 nm were synthesized through a direct ion-exchange process in oversaturated Ni(NO3)2 solution, followed by air annealing. The NiO nanofibers with a porous structure and empty space can accommodate large volume changes and exhibited a high specific capacitance of 700 F g−1 at 2 A g−1, as well as a remarkable rate capability (80% capacitance retention with the current density increasing from 1 to 5 A g−1). In addition, electrospun nickel acetate/PVP-derived NiO nanofibers were applied as cathode materials for ASCs (AC as the anode). The device delivered a specific capacitance of 141 F g−1 with an energy density of 43.75 W h kg−1 and power density of 7.5 kW kg−1.

Question: What's the cathode?
Answer: nickel acetate/PVP-derived NiO nanofibers
Long-term cyclic stability of symmetric cells. One of the most promising applications of metal anodes is to combine them with a sulfur or air cathode with a high energy density. It is thus important to find an efficient way of infusing the alkali metal inside the anode scaffold. To introduce Na in the network, the anode was pre-assembled by stacking the CNF film on top of a pure Na foil. The Na foil was manually pressed into a thickness ranging between 200 and 400 μm. The use of this stacked design saved materials and processing time better than the classical sacrificial-cell electrodeposition method. The thickness of Na foil could be further reduced using industrial pressing tools. Fig. 6a presents a schematic of the stacking scheme of the assembled electrode which allowed Na to be effectively stripped and plated by removal and re-infiltration into the fiber network. Fig. 6b presents a side view of the CNF film stacked on top of a Na layer after 6 mA h cm−2 of Na was stripped and re-deposited at a current density of 1 mA cm−2. The image signifies successful re-infiltration of Na in the fiber network after the two-step process. The fiber diameter increased to ∼600–800 nm from the initial ∼150 nm, proving a large load of deposited Na. The final fiber thickness obtained with the stacked design was compatible with the thickness obtained with regular electrodeposition, indicating that a majority of Na was infiltrated from the initial film into the network. In view of the large variation in the measured Na thicknesses, however, it may be possible that some part of Na had been redeposited back onto the original Na film, as shown in the schematics. The above fiber network was likely to hinder any dendritic growth resulting from this scenario. The overall ZNO@CNF film thickness remained at ∼100 μm after infiltration, suggesting that the network could withstand the mechanical pressure inside of the cell while retaining its original shape. The smooth top view of the same anode shown in Fig. S26† indicates that the ZnO@CNF film was able to hold and control the deposited Na even with a high areal loading of 6 mA h cm−2.

Question: What's the cathode?
Answer: sulfur
Long-term cyclic stability of symmetric cells. One of the most promising applications of metal anodes is to combine them with a sulfur or air cathode with a high energy density. It is thus important to find an efficient way of infusing the alkali metal inside the anode scaffold. To introduce Na in the network, the anode was pre-assembled by stacking the CNF film on top of a pure Na foil. The Na foil was manually pressed into a thickness ranging between 200 and 400 μm. The use of this stacked design saved materials and processing time better than the classical sacrificial-cell electrodeposition method. The thickness of Na foil could be further reduced using industrial pressing tools. Fig. 6a presents a schematic of the stacking scheme of the assembled electrode which allowed Na to be effectively stripped and plated by removal and re-infiltration into the fiber network. Fig. 6b presents a side view of the CNF film stacked on top of a Na layer after 6 mA h cm−2 of Na was stripped and re-deposited at a current density of 1 mA cm−2. The image signifies successful re-infiltration of Na in the fiber network after the two-step process. The fiber diameter increased to ∼600–800 nm from the initial ∼150 nm, proving a large load of deposited Na. The final fiber thickness obtained with the stacked design was compatible with the thickness obtained with regular electrodeposition, indicating that a majority of Na was infiltrated from the initial film into the network. In view of the large variation in the measured Na thicknesses, however, it may be possible that some part of Na had been redeposited back onto the original Na film, as shown in the schematics. The above fiber network was likely to hinder any dendritic growth resulting from this scenario. The overall ZNO@CNF film thickness remained at ∼100 μm after infiltration, suggesting that the network could withstand the mechanical pressure inside of the cell while retaining its original shape. The smooth top view of the same anode shown in Fig. S26† indicates that the ZnO@CNF film was able to hold and control the deposited Na even with a high areal loading of 6 mA h cm−2.

Question: What's the cathode?
Answer: air
Ni foams, typical 3D porous substrates, are extensively employed as current collectors/supports in energy storage devices, because they not only afford large surface areas and easy electrolyte access, but also enable efficient ion diffusion and charge transfer. For example, Chen and coworkers designed hierarchical micro-nano sheet arrays of nickel–cobalt double hydroxide supported on Ni foam (NiCo-DH) via an etching-deposition-growth strategy. The corresponding Ni–Zn battery with a NiCo-DH electrode as the cathode delivered a high specific capacity of 329 mA h g−1. Wang et al. synthesized a Co3O4@NiV-LDH nanowires array grown on the surface of a Ni foam with a hierarchical structure. When used as the cathode, the assembled battery demonstrated a satisfactory capacity of ∼1.25 mA h cm−2. Despite the favorable electrochemical performance of these cathodes, the complicated or multi-step preparation processes required substantially impede their industrial application. Furthermore, the ex situ formed active materials deposited on the Ni foam are unavoidably peeled off during long-term charge–discharge tests, which may cause trouble for the cyclic stability of zinc batteries.

Question: What's the cathode?
Answer: Co3O4@NiV-LDH
Typically, a certain amount of P(VDF-HFP) powder and BaTiO3 piezoelectric particles (4:1 in m/m) were firstly added into a mixture of N,N-dimethylformamide (DMF) and deionized (DI) water under constant stirring at ambient temperature, forming a well-dispersed solution. The solution was then spread on a clean glass substrate, followed by an immersion in a flowing water bath at 80 °C. Several minutes later, a homogeneous white BaTiO3-P(VDF-HFP) film was obtained and self-peeled off from the glass substrate. Next, the film was dried at 100 °C under vacuum to remove the containing water. Afterwards, the dried film was punched according to the size of the anode or cathode, followed by an appropriate polarization under a DC field of 3.5 kV mm−1 in air atmosphere at ambient temperature for 0.5 h. Finally, the polarized pieces were fully soaked in a liquid electrolyte of 1 mol L−1 NaClO4 dissolved in propylene carbonate (PC) with a 5 vol% fluorinated ethylene carbonate (FEC) additive in a glove box over 24 h, yielding the desired BaTiO3-P(VDF-HFP)-NaClO4 piezoelectric gel-electrolyte.

Question: What's the cathode?
Typically, a certain amount of P(VDF-HFP) powder and BaTiO3 piezoelectric particles (4:1 in m/m) were firstly added into a mixture of N,N-dimethylformamide (DMF) and deionized (DI) water under constant stirring at ambient temperature, forming a well-dispersed solution. The solution was then spread on a clean glass substrate, followed by an immersion in a flowing water bath at 80 °C. Several minutes later, a homogeneous white BaTiO3-P(VDF-HFP) film was obtained and self-peeled off from the glass substrate. Next, the film was dried at 100 °C under vacuum to remove the containing water. Afterwards, the dried film was punched according to the size of the anode or cathode, followed by an appropriate polarization under a DC field of 3.5 kV mm−1 in air atmosphere at ambient temperature for 0.5 h. Finally, the polarized pieces were fully soaked in a liquid electrolyte of 1 mol L−1 NaClO4 dissolved in propylene carbonate (PC) with a 5 vol% fluorinated ethylene carbonate (FEC) additive in a glove box over 24 h, yielding the desired BaTiO3-P(VDF-HFP)-NaClO4 piezoelectric gel-electrolyte.

Question: What's the anode?