milerssliu/battery-device-data-qa huggingface dataset:
qas: question: What's the cathode?
context: The Mg/Ti dual dopants also enhance the surface stability even upon deep electrochemical delithiation. Here we found that ex situ soft XAS surface analysis may provide misleading results if the charged electrodes are not handled properly. In principle, Ni should experience oxidation during charging and reduction during discharging. However, due to the cathode–electrolyte parasitic reaction, the surface nickel oxidation state at various charge/discharge states were lower than that of the bulk (Fig. S9†). Another phenomenon that we constantly observe is that the Ni oxidation states for the charged samples were lower than that at the pristine state in both the TEY and FY modes (Fig. S9†), which is counterintuitive. We believe that this might be due to the thermodynamically unstable Ni4+ continually reacting with the electrolyte during the cell teardown and subsequent sample handling. Thus, eliminating the cell resting time and removing the residual electrolyte are critical for maintaining the true Ni oxidation states for soft XAS analysis. We found that the best practice is to dissemble the cell and rinse the electrode immediately after the cell has reached the designated state of charge. This practice is particularly important for the charged electrodes. Here we rinsed the cycled electrode in an Ar filled glove box immediately after the cells were charged to 4.4 V vs. Li/Li+. The LiNiO2 delivered a higher charge capacity at this upper cutoff voltage than the Mg/Ti–LiNiO2 (Fig. S10†). If the surface was stable at the charged state, the Ni oxidation state at the surface should not exhibit significant difference in these two electrodes, because the charge capacity only differed by 22 mA h g−1 (i.e., the Ni oxidation state differed by 0.08). However, we found drastic differences between these electrodes, as explained below. The Ni L3-right/left peak ratios were averaged from three electrodes at the charged state. A significantly higher L3-right/left peak ratio in both FY and TEY modes was found in the Mg/Ti–LiNiO2 sample than that in the LiNiO2 sample (Fig. 4d), indicating enhanced surface stability of the Mg/Ti–LiNiO2 sample in the charged state. Moreover, the low L3-right/left peak ratio in the FY mode of the LiNiO2 electrodes also suggests that the surface reaction induced Ni reduction extended to the deep subsurface. The direct comparison between NMC622 and NMC811 (Fig. S11†) further supports that a higher nickel content results in more surface instability, which can potentially complicate the state of charge assessment using the surface sensitive soft XAS technique. As more studies have made use of the soft XAS technique for analyzing the surface chemistry of battery materials, our results clearly demonstrate that caution is needed when interpreting the data. Although the synchrotron characterization is not highly accessible, other surface-sensitive characterization methods, e.g., XPS, IR, Raman, TEM, ToF-SIMS, also encounter the similar challenges when preparing/handling samples. To improve the data representativeness, the effective error analysis, based on repeated measurements, is recommended.
qas: question: What's the cathode?
answers: answer_id: 81392
question_id: 66158
text: hexacyanoferrates, layered oxides, polyanionic compounds, and conversion-type
question: What's the anode?
context: As benchmark inorganic cathodes, we selected a number of materials for non-aqueous cells which, according to the reviews and to the best of our knowledge, are superior in terms of voltage, specific energy/power or cycling stability and are attributed to various material families (hexacyanoferrates, layered oxides, polyanionic compounds, and conversion-type cathodes). The list of benchmarks includes KVPO4F, K2[(VOHPO4)2(C2O4)] (KVPCO), K1.75Mn[Fe(CN)6]·0.16H2O (KMHCF), Fe[Fe(CN)6] (FeHCF), K1.81Ni[Fe(CN)6]0.97·0.086H2O (KNHCF), K0.7Mn0.5Fe0.5O2 (KMFO), K0.51V2O5 and K0.42V2O5·0.25H2O (KVO), and sulfur (S).
qas: question: What's the cathode?
context: The cathodes were prepared by mixing 80 wt% active materials, 10 wt% acetylene black and 10 wt% polyvinylidene fluoride (PVDF) binder with N-methyl-2-pyrrolidone (NMP) as the solvent. The mixture was coated on aluminum foil, pressed at 20 MPa, and dried at 120 °C in air for 2 h. The 2025 coin-type cells, consisting of the as-prepared cathode, Li metal as the anode and Celgard 2325 as the separator, were assembled in an argon-filled glove box. The electrolyte was 1 M LiPF6 dissolved in a mixture of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) (volume ratio 3:7). All cells were cycled between 2.0 and 4.8 V (versus Li/Li+) at a current density of 20 mA g−1 at room temperature on Land CT 2001A battery testers unless otherwise defined. The electrochemical impedance spectroscopy (EIS) measurements were performed from 100 kHz to 10 mHz with an amplitude of 10 mV using a multichannel potentiostat (PARSTAT MC).
qas: question: What's the cathode?
answers: answer_id: 84043
question_id: 66158
text: Na-TM-oxide
context: In the context of voltage hysteresis, ‘charge-averaged’ discharge (Vdischarge), charge (Vcharge), and net-average (viz., further average of Vdischarge and Vcharge) voltages (as true average voltages) for the ‘control’ and fully Ti-substituted (for Mn-ion) Na-TM-oxide cathodes were estimated, as per the following relations, and presented in Fig. 4 as variations with cycle number.
qas: question: What's the cathode?
answers: answer_id: 84052
question_id: 66158
text:  carbon (ZDPC)
context: In terms of anode fabrication, TiO2/C@NPSC-x was mixed sufficiently with conductive carbon and sodium carboxymethylated cellulose (CMC-Na) to form a uniform slurry (weight ratio: 7:2:1). Then, the Cu foil coated by the slurry was dried in a vacuum oven at 110 °C overnight. The anode electrodes for ex situ XRD tests were fabricated by coating the active materials/CMC-Na (weight ratio: 9:1) slurry on an Al current collector. For cathode electrodes, the home-made activated carbon (ZDPC), conductive carbon and PTFE were blended evenly in deionized water (weight ratio: 90:5:5) and painted on carbon-coated Al foil. The loading weight of each electrode was about 1.0 mg cm−2. Then, coin-type CR2032 cells were constructed inside a glove box filled with Ar gas. The electrolyte was 0.8 M KPF6 in DEC and EC (1:1, v/v). The separator was glass fibers. Fresh potassium foil served as the counter electrode. Before construction of the PIHC device, the TiO2/C@NPSC-700 anode was pre-activated at 0.1 A g−1 for 10 cycles.
qas: question: What's the cathode?
answers: answer_id: 84060
question_id: 66158
text: CNF@V2S3/S
question: What's the electrolyte?
question: What's the cathode?
answers: answer_id: 84061
question_id: 66161
text: CNF@VO0.9/S and CNF/S
context: Fig. 4d shows the comparison of the rate performances and coulombic efficiencies of the three types of cathodes under different current densities (0.1, 0.2, 0.5, 1.0, and 2.0C). All three cathodes show a coulombic efficiency over 98%, which could be due to the highly conductive CNF skeletons. And, with increasing the current density from 0.1C to 2.0C, the CNF@V2S3/S cathodes can retain a specific capacitance of 922 mA h g−1 (78.9% of the initial value), which is much higher than those of VS2-based LSBs. However, the CNF@VO0.9/S and CNF/S cathodes can retain 390 mA h g−1 (55.1%) and 592 mA h g−1 (68.8%). Here, to gain better understanding of the effect of V2S3 on the rate performances of cathodes, the in situ reaction resistances were first derived from the charge/discharge curves (see the ESI for details†). As shown in Fig. 4e, the reaction resistances of all three cathodes increase with the increasing specific capacity, which is caused by the low conductivity of intermediate LiPSs. Compared to the CNF@VO0.9/S and CNF/S cathodes, the CNF@V2S3/S ones show a much lower reaction resistance along the whole electrochemical processes. And similar results can also be obtained from Electrochemical Impedance Spectroscopy (EIS) spectra (Fig. S14†). This decrease in resistances often leads to fast redox kinetics on the CNF@V2S3/S cathodes. Besides, galvanostatic intermittent titration technique (GITT) tests were further carried out to further study the origins for fast transfer kinetics of CNF@V2S3/S cathodes (Fig. S15†). The diffusivities of Li ions between the cathode and electrolyte were estimated, as listed in Table S2.† The diffusion coefficient of Li+ ions in the CNF@V2S3/S/electrolyte system is 2.857 × 10−6 cm2 s−1, which is much higher than those of CNF@VO0.9/S and CNF/S ones (1.554 × 10−7 and 1.645 × 10−7 cm2 s−1) in this work. This greatly improved diffusivities of Li ions would result in the high specific capacity and the high rate capability of CNF@V2S3/S cathodes. Also, a similar conclusion can be obtained from EIS spectra in the low-frequency region (Fig. S14†). It can be seen that the curve slope of CNF@V2S3/S cathodes is much larger than those of the CNF@VO0.9/S and CNF/S ones (Table S3†).
qas: question: What's the cathode?
context: Gas diffusion electrodes (GDEs) were fabricated by spraying a catalyst ink made from polynorbonene tetrablock copolymer powder ionomers (GT32 and GT73) and Pt-based electrocatalysts onto Toray TGP-H-060 gas diffusion layers (GDLs) with 5% PTFE. Commercially available 40% Pt/C (Alfa Aesar HiSPEC 4000, Pt nominally 40% wt, supported on Vulcan XC-72R carbon) was used at the cathode and 60% Pt–Ru/C (Alfa Aesar HiSPEC 10000, Pt nominally 40 wt%, and Ru, nominally 20 wt%, supported on Vulcan XC-72R carbon) was used as the anode. The detailed procedure for ink formulation and GDE fabrication has been previously reported, though a brief description is provided below.
qas: question: What's the cathode?
answers: answer_id: 81408
question_id: 66158
text: LMO 
context: Surface modification using some metal oxides is an appropriate approach to overcome such critical drawbacks of LMO. Metal oxides, such as Ta2O5, ZrO2, Al2O3, ZnO, MgO, and TiO2, have been used as coating layers for LMO cathode material powders. The coating layer minimizes direct contact between the cathode and the electrolyte solution, avoids unwanted interfacial reactions, and thus improves the structural stability and phase transitions. To some extent, these coating films can also improve the cycling performance of the material. Nevertheless, the reported high surface coating using metal oxides usually results in agglomerated nanoparticles and leads to increased resistance. Furthermore, the modest improvement could be a result of increased interfacial resistance due to the insulating nature of surface coating layers.
qas: question: What's the cathode?
answers: answer_id: 84054
question_id: 66158
text: LiPSs 
question: What's the electrolyte?
context: Moreover, the formation of metal sulfides with a non-crystalline structure also reveals enhanced adsorption/bonding of LiPSs owing to abundant defects and dangling bonds. For example, amorphous TiS4 has been successfully prepared by Sakuda et al. through a mechanical milling process using crystalline TiS2, sulfur, and acetylene black. When used as the cathode in a Li–S battery, the dissolution of LiPSs into the electrolyte is significantly suppressed because amorphization reduces the symmetry of the lattice, leading to the possibility of overlapping electron clouds between sulfur and titanium atoms, resulting in chemical bonding between the elements. Liu et al. reported the synthesis of a S@amorphous NiS2 composite via a coprecipitation reaction using Na2S8 and NiCl2 ethanol solution. Here the soluble sulfide ions can permeate into the loose amorphous structure, and thus the S particle would nucleate and grow in the inner space of NiS2, ensuing the high immobilization of S species. Very recently, Yu et al. meticulously designed hollow-amorphous N-doped carbon/MoS3 nanoboxes (NC/MoS3 NBs) as an advanced sulfur host for Li–S batteries. In a typical synthesis, crystalline α-Fe2O3 nanocubes are first coated with a layer of polydopamine, which are then calcined in a N2 atmosphere and etched in HCl solution to obtain N-doped carbon (NC) shells and hollow NC nanoboxes, respectively. Finally, the NC/MoS3 NB host is prepared through heterogeneous nucleation using CTAB as the surfactant and (NH4)2MoS4 as the precursor. Here, the amorphous MoS3 with unsaturated coordination Mo and electron-rich S not only has strong binding capability to LiPSs but also exhibits a catalytic effect on polysulfide conversion, which are verified by both experimental investigations and theoretical calculations. More interestingly, this synthesis strategy can be generalized to fabricate other amorphous metal chalcogenides nanoboxes such as CoSx and WSx, which is also promising to be applied in the fields of energy storage and conversion.
qas: question: What's the cathode?
answers: answer_id: 84064
question_id: 66158
text: Li-rich
context: To further analyze the electrochemical difference between the pristine and treated LMO, the initial cycle curves for the two samples are plotted together in Fig. 2a. For pristine LMO, the plateau above 4.5 V appears as the typical behavior of the Li-rich cathode, which corresponds to the delithiation, charge compensation and oxygen release process. Upon discharge, an S-shaped curve was observed with a discharge capacity of around 200 mA h g−1. Interestingly, the characteristic charge plateau (above 4.5 V) was shortened in the T-LMO sample. Simultaneously, plateaus appeared at around 4.1 V for the charged state and 4.0 V/2.8 V for the discharged state, which can be seen clearly in the dQ/dV plots (Fig. 2b), indicating that the spinel phase may exist in T-LMO.
qas: question: What's the cathode?
context: Metal–air batteries with high energy density have emerged as key players in the energy storage sector. They operate on two underlying processes, namely, the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER). It provides the impetus to design efficient, earth-abundant and economic bifunctional electrocatalysts vis-à-vis precious metal-based catalysts. In this perspective, a few polyanionic battery insertion materials have been reported as potential electrocatalysts. In the current work, metal fluorophosphate (Na2MPO4F, M = Fe/Co/Mn) family of sodium insertion materials have been shown as a new class of bifunctional electrocatalysts with robust structural stability. In particular, Na2CoPO4F was found to exhibit superior catalytic performance with an onset potential of 0.903 V (vs. RHE) for the ORR and an overpotential of 380 mV (vs. RHE) for the OER. The underlying mechanism and kinetics were explored using ab initio computational studies. Overall, polyanionic transition metal fluorophosphates were explored for the first time as bifunctional electrocatalysts capable of working as potential cathode materials in hybrid metal–air batteries.
qas: question: What's the cathode?
context: Imide-functionalized small molecules are represented by 3,4,9,10-perylene-tetracarboxylic diimide (PTCDI 10), recently proposed by Fan et al. It has lower solubility compared to PTCDA, which should have improved its cycling stability. Nevertheless, with 1 M and 3 M KFSI solutions in EC:DMC, rapid capacity fading associated with the material dissolution was observed. The cathode dissolution was suppressed by using 5 M KFSI in EC:DMC, which ensured ∼0% capacity decay over 100 cycles at 100 mA g−1 and ∼90% retention after 600 cycles at 4 A g−1. The reported Qm at 100 mA g−1 was 157 mA h g−1, which is higher than the theoretical value of 137 mA h g−1; the additional capacity (∼27 mA h g−1) originated from the carbon additive. Impressive capacities of 137 and 80 mA h g−1 were observed at 1 and 10 A g−1, respectively. The rate performance of PTCDI was reported to be superior compared to PTCDA under the same conditions. PTCDI-based full cells, which had pre-potassiated graphite as the anode, delivered a Qm of 140 and 80 mA h g−1 at 50 and 500 mA g−1, respectively. The output voltage was 2 V and ∼50% of the capacity retained after 500 cycles at 500 mA g−1.
qas: question: What's the cathode?
answers: answer_id: 84050
question_id: 66158
text: potassium iron(II) hexacyanoferrate
question: What's the anode?
answers: answer_id: 84048
question_id: 66159
text: PTCDA
question: What's the electrolyte?
answers: answer_id: 84049
question_id: 66160
text: 30 M KFSI aqueous solution
context: Later, Wang et al. published a similar study, using annealed PTCDA as the anode material and 30 M KFSI aqueous solution as the electrolyte. The reversible capacity of PTCDA reached 134 mA h g−1 at 0.2 A g−1. Decent rate and cycling capabilities were demonstrated. A full cell with potassium iron(II) hexacyanoferrate as the cathode delivered 39 mA h g−1 based on the combined mass of the electrodes, and it was almost constant up to 4 A g−1 current density. The capacity retention of the full cell was 89% after 1000 cycles at 2 A g−1.
qas: question: What's the cathode?
answers: answer_id: 84053
question_id: 66158
text: air
context: Determined by a continuous discharging test over 27 h, the recorded specific capacity of the battery with the CNT@CNP catalyst is 846.7 mA h gZn−1, and the relative energy density is 1059.92 mW h gZn−1 at an average voltage of 1.2 V, as shown in Fig. 7(d). These outcomes are better than those of most current Fe–N–C catalysts shown in Table 2. Moreover, the rechargeable performance of the battery, equipped with the CNT@CNP catalyst and commercial 20 wt% IrO2 on carbon paper as an air cathode, has been tested by us. As observed in Fig. 7(e), the novel battery shows remarkably improved ORR and OER properties, compared with the reference of the battery equipped with the commercial Pt/C and IrO2 counterpart. At a constant current density of 20 mA cm−2 for 10 h, the cycling of charge and discharge reaches 2 times with respect to the reference battery, as shown in Fig. 7(f). The battery almost maintains a stable discharge potential of 0.83 V and a recharge voltage of 2.25 V even after 60 cycles, which is much better than that of the reference battery shown in Fig. 7(f). So, the synthesized catalyst shows a very good power density in comparison with the corresponding results available in the literature shown in Table 2. Therefore, the optimal catalytic performance of the carbon interpenetrating networks may be attributed to the formation of abundant edge Fe–Nx moieties as active sites at the boundaries and interfaces in the CNT@CNP composites with a smart structure. If so, developing Fe–N–C with interpenetrating network structures may be major breakthroughs of non-PGM materials serving as next-generation catalysts for the ORR.
qas: question: What's the cathode?
answers: answer_id: 84063
question_id: 66158
text: CNF@V2S3/S composite
context: Fig. 1c shows the main fabrication processes of high-performance LSBs based on CNF@V2S3/S composite cathodes. Electrospun nanoscale fibrous skeletons were often used as conductive substrates for active materials in energy-storage devices. During the annealing under Ar, many V atoms were forced out to the surface of electrospun nanofibers under the Kirkendall effect, and formed into VO0.9 nanocrystals. Then, the formed VO0.9 nanocrystals will further be vulcanized into V2S3 nanocrystals with an ultralow rate during the vulcanization reaction in a S/Ar environment. As a result, many V2S3 nanocrystals are stably connected to the surface of CNFs, which benefit the transport of electrons through the CNF/V2S3 composites. And these tiny V2S3 nanocrystals can also show a high specific surface area and a high catalytic activity, which can benefit the chemisorption and the transformation of sulfur species during the charge/discharge processes in LSBs.
qas: question: What's the cathode?
answers: answer_id: 84059
question_id: 66158
text: F-doped h-BNNS 
context: F-doped h-BNNS were used as the cathode material for magnesium batteries, a potential alternative to Li-ion batteries due to their higher safety and lower cost. It was reported that fluorine can be grafted via a reaction between h-BNNS and fluoroboric acid. Fluorination effectively improves the electrical conductivity of h-BNNS and their electrochemical performance for Mg batteries.
qas: question: What's the cathode?
answers: answer_id: 84071
question_id: 66158
text: activated carbon (AC)
context: Recently, a high energy density (97.6 W h kg−1) along with impressive cycling steadiness (73% retention after 5000 cycles at 1 A g−1) was reported by Yang et al. for a lithium-ion capacitor fabricated by using PAN/hydrothermal-made V3O7·H2O nanowire derived CNFs/V2O3 hybrids as the anode and commercial activated carbon (AC) as the cathode. Additionally, the prepared CNFs/V2O3 nanocomposites with internal void spaces displayed a high capacity of 569.1 mA h g−1 at 0.1 A g−1 as well as unexpected rate capability (238.5 mA hg−1 at 10.0 A g−1) in half-cell tests. By electrospinning a PAN/VO(acac)2 precursor solution, followed by calcination, V–O–C nanocomposites with a specific surface area of 587.9 m2 g−1 were obtained. An atomic level dispersion of vanadium within the composite nanofibers enabled the resultant V–O–C nanocomposites to deliver a specific capacitance of 463 F g−1 at 1 A g−1 with good electronic conductivity and electrolyte penetration. Moreover, the electrochemical properties of V5+ are superior to those of V3+ and V4+ when vanadium oxide-embedded carbon fibers are applied in a supercapacitor. Bai et al. produced CNFs/V2O3, CNFs/VO2–V2O5 and CNFs/V2O5via electrospinning a PAN/VO(acac)2 precursor solution, followed by different calcination processes. The results showed that the electrochemical performance of CNFs/V2O5 is better than that of CNFs/V2O3 and CNFs/VO2–V2O5 when they were applied to SCs. In Tang's work, CNFs/VO/VOx web-like nanocomposites were obtained by electrospinning a polymer-based solution containing PAN, PVP, hybrid vanadium precursors (VO2, V2O5, and VO(acac)2) and DMF, followed by carbonization treatment. The formation of quasi-metallic VO (∼102 Ω−1 cm−1) in the CNF enhanced the rate of electron transfer in the web-like electrode. Besides, the well-developed pore structure and rich vanadium redox couples also promoted the rapid ion transfer rate. As a consequence, the SC equipped with symmetric CNFs/VO/VOx electrodes exhibited a specific capacitance of 325.7 F g−1 at 1 A g−1 with 92% retention at 4 A g−1 after 5000 cycles.
qas: question: What's the cathode?
answers: answer_id: 84076
question_id: 66158
text: LiFePO4 
context: Second, the electrode capacity was calculated (eqn (4)) to be 453 mA h g−1 and third, by integrating the potential profile (eqn (5)), the gravimetric electrode energy density was estimated to be 570 W h kg−1. Both values are here for the organic redox-active part (AQ4), while if we take into account the entire electrode (AQnC72), we arrive at significantly more modest values: 222 mA h g−1 and 279 W h kg−1 (Table S8†). Neither of these measures are totally fair to be compared with traditional electrodes as we also assume a role as current collector for the graphene. With this caveat, the former measure provides twice the experimentally measured capacity of pure AQ, reported to be 217 mA h g−1 ( ) and a theoretical gravimetric energy density comparable to the cathode active materials LiFePO4 (544 W h kg−1) and LiMn2O4 (548 W h kg−1).
qas: question: What's the cathode?
context: During the initial discharge on the cathode: