milerssliu/battery-device-data-qa huggingface dataset:
Fig. 3 shows the electrochemical performances of a half-cell in a three-electrode system and a NVP//NTP full cell. As shown in Fig. 3a and b, the NVP half-cell exhibits a pair of redox peaks with good symmetry at 0.68 V and 0.42 V vs. Ag/AgCl, which can be ascribed to the reversible conversion of the V3+/V4+ couple, corresponding to the reversible extraction/insertion of Na+ in the NVP electrode. The half-cell delivers a specific charge and discharge capacity of 110 mA h g−1 and 96 mA h g−1 in the first cycle, and exhibits good reversibility for the first time. The irreversible charge capacity mainly resulted from the dissolution of the V-ions until the appearance of O2 evolution which was recorded in CV curves. For NTP, a pair of Ti4+/Ti3+ redox peaks at −0.55 V and −0.82 V vs. Ag/AgCl can be found in the CV curves. As seen in Fig. 3c, the CV curves show that the hydrogen evolution reaction still does not occur when the potential is −1.1 V vs. Ag/AgCl, which suggests that the Na–H2O–urea–DMF electrolyte can inhibit the side reaction well. As shown in Fig. 3d, the NTP in the Na–H2O–urea–DMF electrolyte delivers a pristine discharge capacity of 118 mA h g−1, concurrently exhibiting a perfect platform and good reversibility, which is better than that of a NTP anode with cationic doping. As shown in Fig. S10 and S11,† the NTP anode exhibits an impressive cycling stability in a conventional non-aqueous electrolyte. However, the coulombic efficiency and cycling performance of the NVP cathode at 2C in a conventional non-aqueous electrolyte are poor due to the dissolution of V-ions and change of structure.

Question: What's the anode?
Answer: NTP
For the operando-XRD measurements self-standing cathode materials were prepared, using Li1.2Mn0.6Ni0.1Co0.1O2 powder, high-conductive carbon (ketjan black, Alfa Aesar, 99.99%) and PVDF (Kynar Flex, Arkema) dissolved in acetone (Poch czda) in a 70:10:20 wt% ratio, respectively. The slurry was spread on glass and dried in air for about 15 minutes at 80 °C in a glove box overnight as was discussed previously. For the tests, a home-made cell with a Berillium window, adjusted to a PANalytical Empyrean diffractometer, was assembled in an mBraun Unilab argon glovebox, using the same counter electrode and electrolyte as for the CR2032 cells. The operando-XRD measurements were conducted, using the PANalytical Empyrean diffractometer combined with s one-channel Biologic potentiostat/galvanostat with a C/50 current load applied, in the voltage regime of 2.0 V to 4.8 V.

Question: What's the cathode?
Our study underlines the importance of gaining deeper insights into the anionic redox activities of Li-rich materials for designing a new cathode material for future LIBs. Promoting the reversible anionic redox contributions while suppressing the irreversible reactions is vital in designing a cathode material with high energy density and good cycling performance. The combined computational/experimental approach presented here can be applied to predict and verify the anionic redox activities in other Li-rich materials to accelerate the discovery of materials with high energy density and good cycling performance.

Question: What's the cathode?
In this study, a flexible self-charging sodium-ion full battery (SCSFB) was feasibly designed by employing self-synthesized Na3V2(PO4)3@C as the cathode, commercial hard carbon as the anode, and a flexible BaTiO3-P(VDF-HFP) film immobilized with a liquid electrolyte of NaClO4 as the built-in piezoelectric gel-electrolyte (BaTiO3-P(VDF-HFP)-NaClO4). Owing to the excellent compatibilities of the electrodes, the flexible SCSFB delivers reasonable electrochemical performance including large specific capacity and stable cyclability. Besides, external mechanical energy from the ambient environment can also be simultaneously collected and stored via a persistent self-charging mode, whether with static compression, repeated bending or continuous palm patting. This work paves a feasible way to the achievement of sustainable sodium-ion full batteries with high flexibility and enhanced safety for wearable electronics that come into direct contact with human tissues.

Question: What's the cathode?
Answer: Na3V2(PO4)3@C
In this study, a flexible self-charging sodium-ion full battery (SCSFB) was feasibly designed by employing self-synthesized Na3V2(PO4)3@C as the cathode, commercial hard carbon as the anode, and a flexible BaTiO3-P(VDF-HFP) film immobilized with a liquid electrolyte of NaClO4 as the built-in piezoelectric gel-electrolyte (BaTiO3-P(VDF-HFP)-NaClO4). Owing to the excellent compatibilities of the electrodes, the flexible SCSFB delivers reasonable electrochemical performance including large specific capacity and stable cyclability. Besides, external mechanical energy from the ambient environment can also be simultaneously collected and stored via a persistent self-charging mode, whether with static compression, repeated bending or continuous palm patting. This work paves a feasible way to the achievement of sustainable sodium-ion full batteries with high flexibility and enhanced safety for wearable electronics that come into direct contact with human tissues.

Question: What's the anode?
Answer: hard carbon
ssZIBs are composed of four components including a cathode, an anode (zinc metal), a solid electrolyte and current collectors. The gel electrolyte is sandwiched between the cathode and anode. Each component has a significant effect on the performance of the whole battery. Currently, various gel electrolytes have been studied and have been applied in ZIBs. However, the performance of ssZIBs is still not comparable with that of the batteries using liquid electrolytes, especially high rate capability, due to the low ionic conductivities of gel electrolytes. To realize high ionic conductivity, an ideal gel electrolyte requires a high-water content and efficient ion migration channels, combined with reasonable mechanical properties. As one of the principal natural polymers, cellulose nanofibers (CNFs) are widely used as a sustainable reinforcing additive in various composites. In addition, the hydrophilic skeleton of CNFs and their three-dimensional fiber network with a large space can help stabilize the channels for charge transportation. Furthermore, due to the abundant hydroxyl groups on the surface of CNFs, it is facile to link the CNFs with polyacrylamide (PAM) molecular chains through hydrogen bonding. The combination of CNFs and PAM can serve as an effective solid electrolyte with good mechanical properties and high ionic conductivity. Due to the high thermal stability of hydrogel polymers, ssBs are also able to operate under both low and high temperature conditions, which is critical for the application of batteries in some harsh environments such as cold/frozen regions and flying airplanes in space.

Question: What's the cathode?
ssZIBs are composed of four components including a cathode, an anode (zinc metal), a solid electrolyte and current collectors. The gel electrolyte is sandwiched between the cathode and anode. Each component has a significant effect on the performance of the whole battery. Currently, various gel electrolytes have been studied and have been applied in ZIBs. However, the performance of ssZIBs is still not comparable with that of the batteries using liquid electrolytes, especially high rate capability, due to the low ionic conductivities of gel electrolytes. To realize high ionic conductivity, an ideal gel electrolyte requires a high-water content and efficient ion migration channels, combined with reasonable mechanical properties. As one of the principal natural polymers, cellulose nanofibers (CNFs) are widely used as a sustainable reinforcing additive in various composites. In addition, the hydrophilic skeleton of CNFs and their three-dimensional fiber network with a large space can help stabilize the channels for charge transportation. Furthermore, due to the abundant hydroxyl groups on the surface of CNFs, it is facile to link the CNFs with polyacrylamide (PAM) molecular chains through hydrogen bonding. The combination of CNFs and PAM can serve as an effective solid electrolyte with good mechanical properties and high ionic conductivity. Due to the high thermal stability of hydrogel polymers, ssBs are also able to operate under both low and high temperature conditions, which is critical for the application of batteries in some harsh environments such as cold/frozen regions and flying airplanes in space.

Question: What's the anode?
Answer: zinc metal
Recently, we successfully synthesized and deployed a new family of redox shuttle additives, aromatic cyclopropenium salts, for Na-ion batteries under harsh overcharging conditions. The cyclopropenium cation combines the elements of aromaticity and ionicity, leading to superior electrochemical stability and solubility over conventional neutral shuttle molecules. Together with the other enlightening studies of cyclopropenium salts in fields such as electrophotocatalysis and redox flow batteries, we envisioned the possibility of devising a high-potential cyclopropenium cation catered to Ni-rich cathodes.

Question: What's the cathode?
Answer:  Ni-rich
The electrochemical performances of bare LMO and LMO-30 min in a full cell (S-C(PAN)‖LMO) configuration at 1C-rate and 25 °C were compared as shown in Fig. 4a. The full cell (S-C(PAN)‖LMO) with the LMO-30 min cathode shows better capacity retention of 77% after 1000 cycles at 1C, corresponding to only 0.023% fading rate per cycle from the first cycle to the 1000th cycle. In contrast, the bare LMO delivers a retention capacity of 45%, about 0.055% capacity fading rate per cycle under the same conditions. The performance is noteworthy, since S. Wei et al. have reported 0.027% capacity decay rate per cycle calculated from the second to 1000th cycle, even at low current density (0.4C-rate) for the Li/S-C(PAN) cell.

Question: What's the cathode?
To study the catalytic performance of MoS2, the potentiostatic reduction of Li2S8 (10 mM based on sulfur in tetraglyme solution) was conducted on CF-based current collectors. Here, 25 μL Li2S8 was dropped onto the CF, MoS2 sheet/CF, and MoS2 ND/CF current collectors as the cathodes. CR2032 coin cells were assembled using as-prepared cathodes, Li metal anodes, Celgard separators, and 25 μL 0.5 M LiTFSI tetraglyme electrolyte. The cells were discharged to 2.06 V at 0.112 mA, to reduce all the long chain polysulfides to Li2S4. Then, the cells were kept potentiostatically at 2.05 V to drive the nucleation and growth of Li2S until the current dropped below 10−5 A. The current–time curves were integrated based on Faraday's law to evaluate the capacities from the precipitation of Li2S on the various current collectors. To study the morphology of the precipitated Li2S, the operated cells were dissembled in a glovebox and washed with flooded DME before taking them for SEM observation.

Question: What's the cathode?
Answer: CR2032 coin cells
To study the catalytic performance of MoS2, the potentiostatic reduction of Li2S8 (10 mM based on sulfur in tetraglyme solution) was conducted on CF-based current collectors. Here, 25 μL Li2S8 was dropped onto the CF, MoS2 sheet/CF, and MoS2 ND/CF current collectors as the cathodes. CR2032 coin cells were assembled using as-prepared cathodes, Li metal anodes, Celgard separators, and 25 μL 0.5 M LiTFSI tetraglyme electrolyte. The cells were discharged to 2.06 V at 0.112 mA, to reduce all the long chain polysulfides to Li2S4. Then, the cells were kept potentiostatically at 2.05 V to drive the nucleation and growth of Li2S until the current dropped below 10−5 A. The current–time curves were integrated based on Faraday's law to evaluate the capacities from the precipitation of Li2S on the various current collectors. To study the morphology of the precipitated Li2S, the operated cells were dissembled in a glovebox and washed with flooded DME before taking them for SEM observation.

Question: What's the anode?
Answer: Li metal
To study the catalytic performance of MoS2, the potentiostatic reduction of Li2S8 (10 mM based on sulfur in tetraglyme solution) was conducted on CF-based current collectors. Here, 25 μL Li2S8 was dropped onto the CF, MoS2 sheet/CF, and MoS2 ND/CF current collectors as the cathodes. CR2032 coin cells were assembled using as-prepared cathodes, Li metal anodes, Celgard separators, and 25 μL 0.5 M LiTFSI tetraglyme electrolyte. The cells were discharged to 2.06 V at 0.112 mA, to reduce all the long chain polysulfides to Li2S4. Then, the cells were kept potentiostatically at 2.05 V to drive the nucleation and growth of Li2S until the current dropped below 10−5 A. The current–time curves were integrated based on Faraday's law to evaluate the capacities from the precipitation of Li2S on the various current collectors. To study the morphology of the precipitated Li2S, the operated cells were dissembled in a glovebox and washed with flooded DME before taking them for SEM observation.

Question: What's the electrolyte?
Answer: 25 μL 0.5 M LiTFSI tetraglyme
Later, Xu et al. investigated how the electrolyte affects the performance of 1a-based cathodes. It was shown that a KFSI solution in 1,2-dimethoxyethane (DME) enables much better rate capability and cycling stability of 1,5-AQDS, owing to a stable solid electrolyte interphase (SEI) forming in this electrolyte. For the optimized electrolyte composition, Qm was 84 mA h g−1 at 3C (390 mA g−1), and 80% of the capacity was retained after 1000 cycles.

Question: What's the cathode?
Simultaneously, the predicted structural changes of O3-Nax[Ni0.5Mn0.5]O2 during Na+ extraction/insertion are presented in Fig. 5a. With extraction of 0.75 mol of Na from O3-Na1[Ni0.5Mn0.5]O2, the c-lattice parameter gradually increased from ∼15.97 to ∼17.40 Å because of the reinforced repulsive force between O2− anions. Then, after an additional 0.25 mol Na extraction, it decreased to ∼15.24 Å owing to MeO2 slab gliding arising from the structural instability, which matched well with the structural change of other layered-type cathode materials for SIBs. Furthermore, as shown in Fig. 5b, we compared the c-lattice parameters of various O3-/P3-NaxCa0.01[Ni0.5Mn0.5]O2 verified through Rietveld refinement based on operando XRD results and those of O3/P3-Nax[Ni0.5Mn0.5]O2 predicted through the first-principles calculations. We confirmed that despite the occurrence of a partial two-phase reaction, the c-lattice parameter was increased in general during extraction of Na ions from O3-Na1[Ni0.5Mn0.5]O2 to P3-Na0.25[Ni0.5Mn0.5]O2. In the case of Na0[Ni0.5Mn0.5]O2, although two phases were detected in the XRD patterns of NaxCa0.01[Ni0.5Mn0.5]O2 from the operando XRD analysis, the average value of c-lattice parameters on the two phases was similar to the c-lattice parameter predicted through first-principles calculations. Moreover, this result implies that at the Na0[Ni0.5Mn0.5]O2 composition, coexistence of O3′ and O3′′ phases is more favorable than perfect phase transition to the O3′′ phase, which agrees with the experimental results of previous research studies.

Question: What's the cathode?
The comprehensive electrochemical and theoretical investigations suggested that the MoS2 NDs with strong LPS absorptivity and high catalytic property would be an ideal choice for robust electrochemical performance for LSBs. Thus, we systematically performed electrochemical measurements of MoS2 ND/porous carbon/Li2S6, in comparison with porous carbon/Li2S6 and MoS2 sheet/porous carbon/Li2S6 cathodes. Fig. 6a shows the CV curves of MoS2 ND/porous carbon/Li2S6 between 1.7–2.8 V vs. Li+/Li at a scan rate of 0.1 mV s−1. Two cathodic peaks at 2.26 and 2.01 V were delivered during the first scan, which were assigned to the reduction of long-chain polysulfides to short-chain Li2S4 and further to solid Li2S. The reversible oxidation of Li2S to polysulfides and to sulfur were presented by two anodic peaks at 2.39 and 2.47 V, respectively. In the following three cycles, the overlap of the discharge/charge peaks evidently indicated the excellent reversibility of the MoS2 ND/porous carbon/Li2S6 electrode. Note that a slight negative shift of the cathodic peak from 2.26 V in the 1st sweep to 2.28 V in the following sweeps could be observed, possibly due to the increased polarization as the starting material changed from a liquid catholyte to solid sulfur from the 2nd cycle. The excellent reversibility was also confirmed by discharging/charging at 0.1C for 100 cycles (Fig. 6b). The MoS2 ND/porous carbon/Li2S6 electrode presented a capacity of 1107 mA h g−1 at the 2nd cycle and retained 1020 mA h g−1 after 100 cycles, rendering a low capacity degradation rate of 0.08% per cycle. In contrast, the porous carbon/Li2S6 and MoS2 sheet/porous carbon/Li2S6 presented much higher capacity fading rates of 0.5% and 0.19% per cycle, respectively (Fig. S11, ESI†).

Question: What's the cathode?
Answer: carbon/Li2S6
To further probe the electrochemical performance of the UTCNF, a kinetic analysis was conducted. Fig. 4a shows the CV curves of the UTCNF at different scan rates. The redox electrochemical reactions occurring on the UTCNF may be described as the reversible reactions Ni(OH)2 + OH− ↔ NiOOH + H2O + e− and Co(OH)2 + OH− ↔ CoOOH + H2O + e−. According to the formula i = k1v + k2v1/2 (i and v are the current and scan rate), i at a given potential can be divided into capacitive limited effects (k1v) and diffusion-controlled effects (k2v1/2). As illustrated in Fig. 4b, the detailed capacitive fraction (blue region) was calculated to be 35.8% at 0.5 mV s−1. Moreover, the capacitive contributions at 0.1 and 1 mV s−1 were also determined (Fig. 4c) to be 20.6% and 40.4%, respectively, which indicates that the electrochemical process is controlled by both capacitive behavior and diffusion. Fig. 4d shows the Nyquist plots of the UTCNF//Zn battery and the CNF//Zn battery, and the fitting values are listed in Table S3.† The UTCNF//Zn battery shows a larger charge transfer resistance Rct (4.1 Ω) than that of the CNF//Zn battery (2.4 Ω), which may be due to the decreased conductivity due to in situ formation of cobalt/nickel composite hydroxides after ultrasonic treatment. Such a markedly enhanced performance of the UTCNF//Zn battery may be attributed to the formed surface-active materials and the unique porous structure of the UTCNF cathode.

Question: What's the cathode?
Answer: UTCNF
The need to increase the energy density of Li-ion batteries leads to continual development of electrode material technology, including engineering of the physicochemical properties of cathode materials. Among them, Li-rich layered oxides are attracting considerable research attention as a candidate for high performance positive electrodes due to their high specific charge (capacity), exceeding 200 mA h g−1. This group of compounds, proposed firstly by Thackeray and Johnson, include pristine Li2MnO3 or Li2MnO3 with partial substitution of Mn with other transition metals (TMs) and is often described as: xLi2MnO3·(1 − x)LiMO2 (or alternatively Li[LiyMn1−y−zMz]O2) (M – transition metal). Although, initially Thackeray et al. reported that Li2MnO3 (theoretical capacity 468 mA h g−1) is electrochemically inactive because Mn4+ cannot be oxidized to higher states, further studies showed that by means of appropriate activation processes Li2MnO3 can deliver higher discharge capacities than LiMnO2. Further studies by Kobobuchi et al. suggested that upon delithiation the local electronic state of lattice oxygen in Li2MnO3 may change, affecting the material performance. XAS studies of the O K-edge and Mn L-edge showed that in the Li-rich NMC sample charged up to 4.7 V vs. Li+/Li, oxygen ions also contribute to the reduction of manganese via electron transition from O-1s to the hybridized bands composed of O-2p and Mn-3dx2−y2. As a result, the change of the local electronic state surrounding Mn4+ ions triggers their migration within TMs and/or into the Li layers, which may be reflected in phase transformation of the initial monoclinic (C2/m) layered structure into either a rhombohedral (Rm) and/or a spinel structure. As confirmed by Amalraj et al. phase transition of Li2MnO3 from layered to spinel-like structures occurs even at potentials as low as 4.3 V, while at 4.5 V Li2MnO3 by partial loss of Li2O forms Li2−xMnO3−x/2 with enhanced stability associated with the existence of a composite structure built up with Li2MnO3 domains in a LiMnO2 matrix.

Question: What's the cathode?
C-based materials such as spheres, fibers, and cages have been reported to adsorb polysulfides. Their ability to trap LiPSs in cathodes suppresses the shuttle effect, and improves the cycling of Li–S batteries. To compare the LiPS adsorption on hollow Co5.47Nx–C and C spheres, visual adsorption tests were conducted using Li2S6 as the LiPS; the results are presented in Fig. 4a. The initially yellow Li2S6 solution containing hollow Co5.47Nx–C spheres became colorless after 8 h. In contrast, the equivalent test with C spheres showed slight fading of the yellow solution. This showed that the Co5.47Nx–C spheres adsorbed the LiPS more readily than the C spheres. This was attributed to both physical and chemical adsorption because of the Co5.47Nx nanoparticles and mesoporous hollow layer of the Co5.47Nx–C spheres.

Question: What's the cathode?
Fig. 5b and d display the images of S-C(PAN) anodes cycled with bare LMO and LMO-30 min, respectively. Also, the images of S-C(PAN) anodes cycled with PLMO-10 min and LMO-10 min are shown in Fig. S4b and d.† The morphologies of cycled S-C(PAN) electrodes with bare LMO, PLMO-10 min, and LMO-10 min electrodes seem rough with obvious cracks. In contrast, Fig. 5d displays the smooth surface of the S-C(PAN) electrode with no severe cracking. The surface feature and integrity are believed to be related to the manganese dissolution of the LMO cathode and the re-deposition on the anode surface, which will be discussed in detail in the following text.

Question: What's the cathode?
Answer: LMO
Fig. 5b and d display the images of S-C(PAN) anodes cycled with bare LMO and LMO-30 min, respectively. Also, the images of S-C(PAN) anodes cycled with PLMO-10 min and LMO-10 min are shown in Fig. S4b and d.† The morphologies of cycled S-C(PAN) electrodes with bare LMO, PLMO-10 min, and LMO-10 min electrodes seem rough with obvious cracks. In contrast, Fig. 5d displays the smooth surface of the S-C(PAN) electrode with no severe cracking. The surface feature and integrity are believed to be related to the manganese dissolution of the LMO cathode and the re-deposition on the anode surface, which will be discussed in detail in the following text.

Question: What's the anode?
Answer: S-C(PAN)
Here, we demonstrate a new method to modify the surface of an LMO electrode for the first time. A stabilized LMO cathode was achieved by the electrospun coating of PVDF and gallium (Ga) and niobium (Nb) co-doped LLZO (Li5.6Ga0.26La2.9Zr1.87Nb0.05O12, LGLZNO). The PVDF@LGLZNO fibrous film coating acts as an effective artificial CEI to suppress the manganese dissolution and significantly minimize the undesirable interfacial reaction between the cathode and electrolyte. The improved LMO was further verified by coupling with an S-C(PAN) composite anode to realize stable rate performance and long cycling stability.

Question: What's the cathode?
Answer: LMO
Here, we demonstrate a new method to modify the surface of an LMO electrode for the first time. A stabilized LMO cathode was achieved by the electrospun coating of PVDF and gallium (Ga) and niobium (Nb) co-doped LLZO (Li5.6Ga0.26La2.9Zr1.87Nb0.05O12, LGLZNO). The PVDF@LGLZNO fibrous film coating acts as an effective artificial CEI to suppress the manganese dissolution and significantly minimize the undesirable interfacial reaction between the cathode and electrolyte. The improved LMO was further verified by coupling with an S-C(PAN) composite anode to realize stable rate performance and long cycling stability.

Question: What's the anode?
Answer: S-C(PAN) composite