milerssliu/battery-device-data-qa huggingface dataset:
Recent studies have suggested that Co-free, Ni-rich layered cathodes (e.g., doped LiNiO2) can provide promising battery performance for practical applications. However, these layered cathodes suffer from significant surface instability during various stages of the sample history, which generates inherent challenges for achieving stable battery performance and obtaining statistically representative characterization results. To reliably report the surface chemistry of these materials, delicate controls of stepwise sample preparation are required. In this study, we aim to illustrate how the surface chemistry of LiNiO2 based materials changes with various environments, including human exhalation, sample storage, sample preparation, electrochemical cycling, and surface doping. Our results demonstrate that the surface of these materials is highly reactive and prone to alter at various stages of sample handling and characterization. The sensitive surface could impact the interpretation of the surface chemical and structural information, including surface carbonate formation, transition metal reduction and dissolution, and surface reconstruction. Importantly, the heterogeneity of the surface degradation calls for a consolidation of nanoscale, high-resolution characterization and ensemble-averaged methods in order to improve statistical representation. Furthermore, the doping chemistry can effectively mitigate the surface degradation and improve overall battery performance due to the enhanced surface oxygen retention. Our study highlights the necessity of strict measurements through complementary characterization at multiple length scales to eliminate unintentional biased conclusions.

Question: What's the cathode?
Answer: Co-free, Ni-rich layered
To examine the catalytic and capture property of 1T MoS2 NDs in a working Li–S cell, MoS2 ND/porous carbon/Li2S6 cathodes were prepared and subjected to synchrotron in situ XRD and in situ EIS characterizations. Fig. 4 shows the contour plot of the in situ XRD patterns collected during the first two cycles. Before discharging, no crystalline peaks were observed, confirming the high purity of the polysulfide catholyte and the low content of MoS2 NDs. When the cell was discharged to the plateau at 2.1 V, peaks referring to the (111) and (200) planes of cubic Li2S (PDF No. 023-0369, marked with a black dashed-line) appeared and reached their maximum intensity at the end of lithiation (bottom of Fig. 4). Upon charging, the intensity of Li2S decreased gradually, followed with no discernible XRD peaks and then the generation of monoclinic S8 (PDF No. 071-0137, marked with white dashed-lines), illustrating the solid (Li2S)–liquid (polysulfides)–solid (S8) reactions during the charging process. During the 2nd discharge/charge, reversible transitions between sulfur and Li2S were observed. When we compare the current in situ XRD results with peer studies, two findings can be extracted. First, MoS2 NDs propel the formation of Li2S crystals. Nelson et al. and Yang et al. both argued that the sluggish kinetics for solid (Li2S2)–solid (Li2S) conversion prevents Li2S formation upon the full discharge of sulfur/carbon electrodes, resulting in undetectable Li2S crystals during in situ XRD studies. The incomplete reduction accounted for the deficient sulfur utilization and low reversible capacities. Fortunately, the powerful MoS2 ND catalysts enabled the reversible formation of crystalline Li2S in our operando XRD studies. Second, Ye et al. reported that the poor catalytic capability of MoN led to occasioned residual S8 XRD peaks for the MoN/sulfur electrode after full discharging, which was also observed for conventional 2H MoS2 flakes-modified porous carbon/Li2S6 cathodes in this work (Fig. S9, ESI†). In contrast, no residual sulfur/Li2S crystals were observed for MoS2 ND/porous carbon/Li2S6 after full discharging/charging, respectively, again indicating the high catalytic property of the 1T MoS2 NDs.

Question: What's the cathode?
Answer: MoS2 ND/porous carbon/Li2S6
To examine the catalytic and capture property of 1T MoS2 NDs in a working Li–S cell, MoS2 ND/porous carbon/Li2S6 cathodes were prepared and subjected to synchrotron in situ XRD and in situ EIS characterizations. Fig. 4 shows the contour plot of the in situ XRD patterns collected during the first two cycles. Before discharging, no crystalline peaks were observed, confirming the high purity of the polysulfide catholyte and the low content of MoS2 NDs. When the cell was discharged to the plateau at 2.1 V, peaks referring to the (111) and (200) planes of cubic Li2S (PDF No. 023-0369, marked with a black dashed-line) appeared and reached their maximum intensity at the end of lithiation (bottom of Fig. 4). Upon charging, the intensity of Li2S decreased gradually, followed with no discernible XRD peaks and then the generation of monoclinic S8 (PDF No. 071-0137, marked with white dashed-lines), illustrating the solid (Li2S)–liquid (polysulfides)–solid (S8) reactions during the charging process. During the 2nd discharge/charge, reversible transitions between sulfur and Li2S were observed. When we compare the current in situ XRD results with peer studies, two findings can be extracted. First, MoS2 NDs propel the formation of Li2S crystals. Nelson et al. and Yang et al. both argued that the sluggish kinetics for solid (Li2S2)–solid (Li2S) conversion prevents Li2S formation upon the full discharge of sulfur/carbon electrodes, resulting in undetectable Li2S crystals during in situ XRD studies. The incomplete reduction accounted for the deficient sulfur utilization and low reversible capacities. Fortunately, the powerful MoS2 ND catalysts enabled the reversible formation of crystalline Li2S in our operando XRD studies. Second, Ye et al. reported that the poor catalytic capability of MoN led to occasioned residual S8 XRD peaks for the MoN/sulfur electrode after full discharging, which was also observed for conventional 2H MoS2 flakes-modified porous carbon/Li2S6 cathodes in this work (Fig. S9, ESI†). In contrast, no residual sulfur/Li2S crystals were observed for MoS2 ND/porous carbon/Li2S6 after full discharging/charging, respectively, again indicating the high catalytic property of the 1T MoS2 NDs.

Question: What's the cathode?
Answer: porous carbon/Li2S6
Based on eqn (12), the effective stiffness can be determined if the wave velocity and the material density are known. The wave velocity can be determined from the first arrival of the wave and cell thickness. To confirm that the measured wave velocity is accurate, calibration metals of known thicknesses and wave velocities were tested. Table 4 indicates metal foil thicknesses above 500 μm in thickness are accurately measured, whereas foil thicknesses less than 250 μm are underestimated. We attribute this error to the greater impact of the acoustic gel couplant at these lower thicknesses. The liquid gel couplant, which is necessary to induce low acoustic attenuation at the interface, is of a finite thickness and should be accounted for. Liquid gel couplant typically has a relatively lower wave velocity of around 1500 m s−1 (similar to water) and would therefore result in a significant underestimation of the wave velocity for thin metal foils where the couplant contributes to a greater proportion of the total propagation path. Fortunately, pouch cells are 500 μm thick at the minimum and can be accurately measured. To confirm the consistency of results regardless of battery thickness, pouch cells were constructed with n = 1 to n = 30 layers, with one layer (n = 1) being defined as: anode + separator + cathode. The subsequent layer is then: cathode (other side) + separator + anode. n = 30 is the full 210 mA h LiCoO2/graphite pouch cell, with 15 double-sided cathodes and 16 double-sided anodes. A schematic of the configuration is demonstrated in Fig. 1. In Fig. 3b, the last data point corresponds to n = 34, which was obtained from a slightly thicker commercial pouch cell of the same chemistry and configuration. The resulting thickness vs. first break (Fig. 3b) shows a linear relationship, indicating a constant wave velocity of approximately 1700 m s−1 and resulting in a calculated effective stiffness of 4.76 GPa (Fig. 3a). Therefore, the measured wave velocity and the resulting effective stiffness is confirmed to be the same regardless of how many repeating cell layers there are, and thicker cell stacks do not slow down the wave velocity. The measurement of 4.76 GPa is comparable to a prior ex situ study by Knehr and Hodson, where a digital caliper was used to measure the pouch cell thickness. The careful calibration and confirmatory studies here demonstrate the reliability of the acoustic measurement not only for relative shifts but also in calculating an intrinsic material stiffness.

Question: What's the cathode?
Correction for ‘Identifying the anionic redox activity in cation-disordered Li1.25Nb0.25Fe0.50O2/C oxide cathodes for Li-ion batteries’ by Mingzeng Luo et al., J. Mater. Chem. A, 2020, 8, 5115–5127, DOI: 10.1039/C9TA11739C.

Question: What's the cathode?
Answer: Li1.25Nb0.25Fe0.50O2/C oxide
5.3.2 Coexisting substrates and contaminants. The investigated substrates and contaminants for oily water separation were mainly strong electrolytes such as NaCl, HCl and NaOH. Considering these coexisting chemicals would not significantly change the surface properties of titanate, the added electrolytes were found to have no apparent effects for oil/water separation.

Question: What's the electrolyte?
Answer: NaCl, HCl and NaOH
Small molecules. Perylenetetracarboxylic dianhydride (PTCDA 9) was relatively widely studied in potassium batteries. It was first proposed for K-based cells by Hu et al., who tested it with a carbonate-based electrolyte. The material delivered a Qm of 130 mA h g−1 at 10 mA g−1 with an average discharge potential of 2.4 V, while 66% of that capacity was retained after 200 cycles. At 500 mA g−1, the capacity dropped to 73 mA h g−1.

Question: What's the electrolyte?
Answer: carbonate-based
After testing the nanomesh electrodes, we compared our results to the performance of various 3D-nanostructured core–shell cathodes reported in the literature (Fig. 6). To do that, we first constructed a Ragone plot to compare volumetric capacity and rate performance of the electrodes (Fig. 6a). Note that in this comparison, the capacities and currents are related to the total 3D volume of the cathodes, that is, including the volume of the 3D current collector, active material and the remaining porosity, but excluding any planar substrate.

Question: What's the cathode?
Finally, the versatility in designing nickel nanomesh with different pore sizes, porosities and surface areas can be used to further optimize the structure of nanomesh cathodes for either very high capacities or yet a higher rate performance. For example, in the electrodes prepared in this work, the 3D current collector occupied 24% of the electrode volume. Although this is in the normal range for 3D cathodes (that have up to 40% volume lost to the current collector, Table S3†), it leaves room for improvement. Using nanomesh with yet a higher porosity (currently, up to 89%) may allow packing more active material into the structure and further increasing its volumetric capacity. If the nanomesh is designed with a proper combination of the nanowire diameter and spacing, the high surface area of the current collector can be preserved even for such highly porous nanomesh, maintaining its benefits in high utilization of active Li-ion materials. Because of its customizable structure, nanomesh can also be used to study the fundamental effects of a 3D structure on the properties of Li-ion electrodes. Knowing that nanomesh can also be fabricated as free-standing and flexible foil, the current work paves the way for future free-standing and stackable nanomesh-based cathodes. This, combined with the upscalable and generally feasible method of their fabrication, can make the cathodes attractive for practical application in high capacity and fast charging Li-ion batteries.

Question: What's the cathode?
Answer: nanomesh
Finally, the versatility in designing nickel nanomesh with different pore sizes, porosities and surface areas can be used to further optimize the structure of nanomesh cathodes for either very high capacities or yet a higher rate performance. For example, in the electrodes prepared in this work, the 3D current collector occupied 24% of the electrode volume. Although this is in the normal range for 3D cathodes (that have up to 40% volume lost to the current collector, Table S3†), it leaves room for improvement. Using nanomesh with yet a higher porosity (currently, up to 89%) may allow packing more active material into the structure and further increasing its volumetric capacity. If the nanomesh is designed with a proper combination of the nanowire diameter and spacing, the high surface area of the current collector can be preserved even for such highly porous nanomesh, maintaining its benefits in high utilization of active Li-ion materials. Because of its customizable structure, nanomesh can also be used to study the fundamental effects of a 3D structure on the properties of Li-ion electrodes. Knowing that nanomesh can also be fabricated as free-standing and flexible foil, the current work paves the way for future free-standing and stackable nanomesh-based cathodes. This, combined with the upscalable and generally feasible method of their fabrication, can make the cathodes attractive for practical application in high capacity and fast charging Li-ion batteries.

Question: What's the cathode?
Answer:  nanomesh-based
Similarly, the cycled S-C(PAN) electrodes paired with bare and coated LMO cathodes were investigated by XPS to confirm the SEI layer components and whether there was dissolved manganese deposited on the anode surface. Fig. 7 shows the XPS spectra of the Mn 2p and O 1s peaks on the S-C(PAN) anodes cycled at 25 °C (bare LMO and LMO-30 min) and 55 °C (LMO-30 min) after 100 cycles using 0.4C-rate. Fig. 7a shows the deposition of manganese on the anode surface when a cell was cycled using a bare LMO cathode and it displays two peaks at 640.1 (Mn2+) and 641.3 eV (Mn3+) for Mn 2p3/2. The decomposition of organic compounds from the electrolyte devastates the original SEI layer and the formation of a new SEI layer on the negative electrode surface in the form of MnxOy occurs. In the case of the LMO-30 min cathode, as shown in Fig. 7b and c, the deposition of manganese on the cycled S-C(PAN) electrode was hardly observed. In addition to XPS, EDS analysis and elemental mapping were also performed. No manganese content was detected on the anode surface when the cell was cycled with the LMO-30 min cathode at 25 °C (Fig. S6†) and LMO-30 min cathode at 55 °C (Fig. S7†). However, the cycled S-C(PAN) anode paired with bare LMO shows Mn distribution in Fig. S8.† As mentioned above, the PVDF@LGLZNO fibrous film protects the cathode and reduces the direct contact of the LMO cathode and the electrolyte. The peak of Mn was absent in the PVDF@LGLZNO coated LMO cathodes. DFT calculation further suggests that the dissolved manganese ion can be adsorbed on the garnet surface, whereby the adsorption energy of Mn2+ on the surface of the garnet was calculated as −53.067 kJ mol−1. Details about the estimation can be referred to in the ESI and Fig. S9.†

Question: What's the anode?
Answer: S-C(PAN)
Liquid rechargeable Zn–air batteries were assembled with a homemade cell. A zinc sheet (purity 99.9 wt%) was used as the anode, which was polished with sandpaper before use. A mixed solution of 6 M KOH and 0.2 M Zn(Ac)2 was used as the electrolyte. The air cathode was composed of three layers, a catalyst layer, a nickel foam layer and a gas diffusion layer. The catalytic layer was fabricated by homogeneously mixing the NCAG/Fe–Co catalyst, acetylene black, PTFE (60 wt%) at the mass ratio of 6:1:3. The nickel foam was treated with 0.2 M HCl, water and ethanol for 20 min, successively, and then vacuum dried at 60 °C before use. The three layers were compressed with a roll press to obtain the cathode, which was then vacuum dried at 60 °C for 3 h.

Question: What's the cathode?
Liquid rechargeable Zn–air batteries were assembled with a homemade cell. A zinc sheet (purity 99.9 wt%) was used as the anode, which was polished with sandpaper before use. A mixed solution of 6 M KOH and 0.2 M Zn(Ac)2 was used as the electrolyte. The air cathode was composed of three layers, a catalyst layer, a nickel foam layer and a gas diffusion layer. The catalytic layer was fabricated by homogeneously mixing the NCAG/Fe–Co catalyst, acetylene black, PTFE (60 wt%) at the mass ratio of 6:1:3. The nickel foam was treated with 0.2 M HCl, water and ethanol for 20 min, successively, and then vacuum dried at 60 °C before use. The three layers were compressed with a roll press to obtain the cathode, which was then vacuum dried at 60 °C for 3 h.

Question: What's the anode?
Answer: zinc sheet
Liquid rechargeable Zn–air batteries were assembled with a homemade cell. A zinc sheet (purity 99.9 wt%) was used as the anode, which was polished with sandpaper before use. A mixed solution of 6 M KOH and 0.2 M Zn(Ac)2 was used as the electrolyte. The air cathode was composed of three layers, a catalyst layer, a nickel foam layer and a gas diffusion layer. The catalytic layer was fabricated by homogeneously mixing the NCAG/Fe–Co catalyst, acetylene black, PTFE (60 wt%) at the mass ratio of 6:1:3. The nickel foam was treated with 0.2 M HCl, water and ethanol for 20 min, successively, and then vacuum dried at 60 °C before use. The three layers were compressed with a roll press to obtain the cathode, which was then vacuum dried at 60 °C for 3 h.

Question: What's the electrolyte?
Answer: A mixed solution of 6 M KOH and 0.2 M Zn(Ac)2
The non-aqueous gel polymer electrolyte (GPE) with dual redox additives was prepared by the “solution-cast” technique. Solid pellets of the host polymer PVdF-HFP (1 g) were put in 20 ml acetone and allowed to dissolve properly at room temperature by continuous stirring on a magnetic stirrer for 12 hours. Thereafter, 4 g IL was added in the polymer solution and stirred for another 12 hours. Redox additives (0.04 g KI) and (0.04 g DPA) were added in the PVdF-HFP/IL solution and stirred for further 12 hours at room temperature to obtain a homogeneous and clear solution. The solution was then poured in a glass petri dish and the common solvent acetone was allowed to evaporate slowly at room temperature. Upon complete evaporation of acetone, a free-standing, flexible and mechanically stable GPE film was obtained. The thickness of the dual redox-active GPE film was ∼400 μm. For the comparison, GPEs of compositions PVdF-HFP:IL (20:80 w/w), and PVdF-HFP/IL/DPA and PVdF-HFP/IL/KI with different amounts of redox additives were also prepared by the same procedure, as described above. These GPEs were stored in a dry atmosphere to avoid moisture adsorption. These GPE films were characterized by electrochemical impedance spectroscopy (EIS), linear sweep voltammetry (LSV), and thermogravimetric analysis (TGA). The room temperature ionic conductivity of all the GPEs was measured by EIS in the frequency range from 105 Hz to 1 Hz. The electrochemical stability window (ESW) for each GPE film was measured by LSV at a scan rate of 5 mV s−1. EIS and LSV were performed on an electrochemical analyzer (CHI660E, CH Instruments, USA). TGA was performed on a Perkin Elmer (USA) TGA-7 system from room temperature to 600 °C at a heating rate of 10 °C min−1 in a N2 atmosphere.

Question: What's the electrolyte?
Answer: non-aqueous gel polymer
The non-aqueous gel polymer electrolyte (GPE) with dual redox additives was prepared by the “solution-cast” technique. Solid pellets of the host polymer PVdF-HFP (1 g) were put in 20 ml acetone and allowed to dissolve properly at room temperature by continuous stirring on a magnetic stirrer for 12 hours. Thereafter, 4 g IL was added in the polymer solution and stirred for another 12 hours. Redox additives (0.04 g KI) and (0.04 g DPA) were added in the PVdF-HFP/IL solution and stirred for further 12 hours at room temperature to obtain a homogeneous and clear solution. The solution was then poured in a glass petri dish and the common solvent acetone was allowed to evaporate slowly at room temperature. Upon complete evaporation of acetone, a free-standing, flexible and mechanically stable GPE film was obtained. The thickness of the dual redox-active GPE film was ∼400 μm. For the comparison, GPEs of compositions PVdF-HFP:IL (20:80 w/w), and PVdF-HFP/IL/DPA and PVdF-HFP/IL/KI with different amounts of redox additives were also prepared by the same procedure, as described above. These GPEs were stored in a dry atmosphere to avoid moisture adsorption. These GPE films were characterized by electrochemical impedance spectroscopy (EIS), linear sweep voltammetry (LSV), and thermogravimetric analysis (TGA). The room temperature ionic conductivity of all the GPEs was measured by EIS in the frequency range from 105 Hz to 1 Hz. The electrochemical stability window (ESW) for each GPE film was measured by LSV at a scan rate of 5 mV s−1. EIS and LSV were performed on an electrochemical analyzer (CHI660E, CH Instruments, USA). TGA was performed on a Perkin Elmer (USA) TGA-7 system from room temperature to 600 °C at a heating rate of 10 °C min−1 in a N2 atmosphere.

Question: What's the electrolyte?
Answer: GPE
Carbon surfaces often exhibit poor electrochemical characteristics and therefore need special pretreatment, frequently termed as “activation”. For surface sensitive redox couples the electron transfer at carbon electrodes may depend on edge plane exposure, surface functional groups and cleanliness. Porous electrode structures, such as carbon felts and carbon papers composed of randomly oriented CFs, also suffer from poor electrolyte accessibility, high pressure drops within the cell, and non-uniform electrolyte velocities. These issues limit the mass transport, for instance in redox flow cells, and thus their electrochemical performance. Some improvements have been achieved by modifying the cell architecture (by adding flow fields) and the electrode design. Another strategy is to employ electrodes that allow for control of the orientation of their fibres along the electrolyte flow.

Question: What's the electrolyte?
Owing to their attractive high carrier mobility, ambient stability, superior mechanical flexibility, large band gap and excellent optical properties, group IV–V compounds, as a new kind of 2D materials, show a promising potential application for optoelectronic devices. Herein, 2D GeP nanosheets were exfoliated by a facile LPE method and a photoelectrochemical (PEC)-type photodetector employing a doctor blade deposited 2D GeP nanosheet electrode on an ITO-coated glass was fabricated. Ultrafast carrier dynamics was carefully probed by transient absorption spectroscopy, and the parameters of the photodetector, such as the voltage and electrolyte concentration, were highly optimized. It shows remarkable performance with a responsivity of 187.5 μA W−1, a detectivity of 2.14 × 1012 Jones and an EQE of 61.3% at an ultraviolet wavelength of 380 nm. The proposed strategy avoids complicated material preparation and device fabrication and facilitates large-area photodetection.

Question: What's the electrolyte?