milerssliu/battery-device-data-qa huggingface dataset:
Spherical [Ni0.5Mn0.5](OH)2 precursors were synthesized by the co-precipitation method. Stoichiometric amounts of NiSO4·6H2O and MnSO4·H2O (Samchun Chemical, Korea) were used as starting materials for [Ni0.5Mn0.5](OH)2. The metal solution concentration (2 mol L−1 for the metal solution), pH (∼11.0), temperature (45 °C), and stirring speed of the mixture in the batch-type reactor were carefully controlled. At the same time, aqueous NaOH (Samchun, Korea; NaOH/transition metal molar ratio = 2:1) and aqueous NH4OH (Junsei, Japan; NH4OH/transition metal molar ratio = 1.1:1) as chelating agents were separately fed into the reactor. The precursor powders were obtained by filtering, washing and vacuum drying at 110 °C overnight. For the Na[Ni0.5Mn0.5]O2 cathode, the obtained spherical precursors were mixed with Na2CO3 (Na:[Ni + Mn] molar ratio = 1.05:1, 5% excess Na2CO3), calcined at 800 °C for 24 h in an oxygen atmosphere, and quenched under vacuum conditions. For Ca-substituted Na1−2xCax[Ni0.5Mn0.5]O2 cathodes, an appropriate amount of Ca(OH)2 was mixed with the [Ni0.5Mn0.5](OH)2 precursor and Na2CO3 (Na:Ca:[Ni + Mn] molar ratio = 1.05–2x:x:1, x = 0.01, 0.02, and 0.03) in the same calcination process.

Question: What's the cathode?
Answer: Na1−2xCax[Ni0.5Mn0.5]O2
In addition, the galvanostatic discharge curves of the hybrid battery at different current densities are studied. As displayed in Fig. 6b, a capacity of 785 mA h gZn−1 is achieved at the current density of 2 mA cm−2 based on the mass of Zn consumed. The result is close to the theoretical value (820 mA h gZn−1). It demonstrates the high capacity of the hybrid battery, taking advantage of the Zn–air battery. When the active species in the cathode and the Zn consumed in the anode are both considered, a high gravimetric energy density of 950 W h kg−1 is achieved. Therefore, the results demonstrate the high capacity and energy density of the hybrid Zn battery. The stability of the hybrid battery was another crucial criterion for practical applications. As displayed in Fig. 6c, the hybrid battery exhibits good electrochemical durability with stable delivered capacity and charge/discharge profiles during cycling at 2 mA cm−2. After one thousand cycles, the voltage of the redox reaction and the ORR/OER process are still well retained (Fig. 6d), demonstrating the good long-term cycling stability of the hybrid zinc battery. In addition, high energy efficiency of 72% is achieved after one thousand cycles, which demonstrates the high efficiency of the hybrid battery.

Question: What's the anode?
Answer: Zn
The two-cycled coin-type cells were disassembled in the argon-filled glove box. The cathode electrodes were carefully extracted from the cells and then immediately rinsed in dimethyl carbonate (DMC) solvent to remove electrolyte residues and dried under vacuum overnight. The obtained electrodes were then transferred from the glove box into an oven and treated with different temperatures (210 °C, 280 °C, 350 °C) in the air for four hours. The weight loss during the high-temperature treatment was below 3% of that of the electrode, which primarily resulted from the decomposition of carbon and binder. For comparison, one of the obtained electrodes was kept in the argon-filled glove box at room temperature. After thermal treatment/being kept in the glove box, the electrodes were reassembled into coin-type cells with a fresh Li metal as the counter electrode.

Question: What's the cathode?
Answer: dimethyl carbonate (DMC)
Recently, Fan and co-authors proposed a PTCDI derivative with anthraquinone moieties (PTCDI-DAQ 11). This compound has lower solubility than PTCDI due to the increased molecular weight, as well as higher theoretical capacity of 200 mA h g−1. The observed Qm was up to 220 mA h g−1, again higher than the theoretical value. A decent capacity retention of 73% was demonstrated in the electrolyte with relatively low salt concentration (1 M KPF6 in DME). Moreover, a remarkable capacity of 137 mA h g−1 was obtained at 20 A g−1. A full cell with pre-potassiated terephthalate (K4TP) anode had a high energy density of 295 W h kg−1 (213 mA h g−1 × 1.38 V, calculated per cathode mass), excellent rate capabilities (94 mA h g−1 at 10 A g−1), and cycling stability (49% and 32% retention after 10000 and 30000 cycles, respectively).

Question: What's the cathode?
Inspired by the superior ORR and OER electrocatalytic activities as well as excellent faradaic redox performance of the DBHF fibers, hybrid Zn batteries were fabricated. In the HZB, the DBHF fibers act as the cathode, Zn nanosheets on carbon cloth serve as the anode and a mixed solution of 6 M KOH and 0.2 M Zn(Ac)2 serves as the electrolyte. The charge/discharge performance of the hybrid Zn battery is investigated. As displayed in Fig. 6a, a smooth and flat voltage plateau at ∼1.21 V is detected in the initial discharging process, which indicates the ORR process of a typical Zn–air battery. In the subsequent charging process, the two voltage plateaus at ∼1.85 V and ∼2.05 V correspond to the M–O oxidation and the OER process, respectively. During the second discharge process, two voltage plateaus appear at ∼1.74 V and ∼1.21 V corresponding to the reduction reaction of M–O–OH and the ORR process, respectively. The charge/discharge results are in good agreement with the CV curves (Fig. S7†). Both results demonstrate that the fabricated hybrid battery is able to reversibly store and deliver charges via double sets of electrochemical reactions. They are the ORR/OER reactions in the Zn–air battery and the M–O/M–O–OH redox reaction in the Zn-ion battery assembled in one battery. Such a combination of complementary strength leads to a powerful hybrid Zn battery based on the Zn–air and Zn-ion systems.

Question: What's the cathode?
Answer: DBHF fibers
Besides lithium, a modern LIB typically contains non-widespread transition metals, such as copper (anode current collector), nickel and cobalt (cathode materials). The shortage in cobalt is especially acute. If cobalt-free batteries remain underdeveloped, the production of Co will have to increase up to an order of magnitude to satisfy the future demand. Additionally, extraction and processing of transition metals might be harmful to the environment and is typically energy-intensive.

Question: What's the cathode?
Answer: nickel and cobalt
Besides lithium, a modern LIB typically contains non-widespread transition metals, such as copper (anode current collector), nickel and cobalt (cathode materials). The shortage in cobalt is especially acute. If cobalt-free batteries remain underdeveloped, the production of Co will have to increase up to an order of magnitude to satisfy the future demand. Additionally, extraction and processing of transition metals might be harmful to the environment and is typically energy-intensive.

Question: What's the anode?
Answer: copper
Interestingly, in the presence of Ti-ions as a partial substitute for Mn-ions (as in the case of ‘0.2 Mn/0.3 Ti’ Na-TM-oxide), Mn was found to be completely in the +4 oxidation state (i.e., Mn4+ and not Mn3+) in the pristine electrode, unlike for the ‘0.5 Mn/0 Ti’ counterpart (see ESI Fig. S7d†). Such observations suggest that the presence of Ti-ions suppresses the reduction of Mn4+ to the deleterious Mn3+ during electrode preparation and, thus, improves the stability to some extent. However, similar to the case with ‘0.5 Mn/0 Ti’, Mn3+ did form and the content progressively increased during electrochemical cycling (as inferred from post-cycling XPS data, ESI Fig. S4e†), thus, not totally addressing the problem concerning cycling (in)stability. Of course, in the total absence of Mn-ions, as for the completely Ti-substituted ‘0 Mn/0.5 Ti’ Na-TM-oxide, the oxidation state of Ti-ions remained only as +4 in the as-prepared electrodes, as well as in those cycled for even 100 electrochemical cycles, as can be seen from Fig. 5c and d. In contrast to those observed for the ‘control’ ‘0.5 Mn/0 Ti’ Na-TM-oxide cathode, neither any notable variation of Vdischarge and Vcharge with cycling could be seen, nor any change in colour of the separator could be noted in the case of the fully Ti-substituted (for Mn-ion) Na-TM-oxide cathode, which indicates non-occurrence of TM-dissolution. Not invoking here, the possible additional contribution towards capacity fading from Jahn–Teller distortion of Mn3+ ( ) during electrochemical cycling, the oxidation states of TM-ions at the surface of the Na-TM-oxides, in particular the presence/formation of Mn3+ and its likely dissolution into the electrolyte, presents a strong justification for the capacity fading in the presence of Mn-ions and mitigation of the same upon Ti-substitution. In this case, electrode impedance is also likely to be considerably affected by the replacement of Mn-ions by Ti-ions, as discussed in the following sections.

Question: What's the cathode?
Answer: Ti-substituted (for Mn-ion) Na-TM-oxid
Later, Chen et al. used K2TP under similar conditions as the anode for hybrid supercapacitors. Activated carbon was used as the cathode. Energy of 101 W h kg−1 and power of 2.16 kW kg−1 based on the mass of two electrodes were demonstrated. If the electrolyte mass was included, the values reached 41.5 W h kg−1 and 885 W kg−1, respectively. The capacity retention of the supercapacitor was 97.7% in 500 cycles. In half cells, the capacity of K2TP at 5 A g−1 was 124 mA h g−1.

Question: What's the cathode?
Answer: carbon
Later, Chen et al. used K2TP under similar conditions as the anode for hybrid supercapacitors. Activated carbon was used as the cathode. Energy of 101 W h kg−1 and power of 2.16 kW kg−1 based on the mass of two electrodes were demonstrated. If the electrolyte mass was included, the values reached 41.5 W h kg−1 and 885 W kg−1, respectively. The capacity retention of the supercapacitor was 97.7% in 500 cycles. In half cells, the capacity of K2TP at 5 A g−1 was 124 mA h g−1.

Question: What's the anode?
Answer: K2TP
To obtain strong immobilization and fast conversion kinetics for polysulfides, the concept of constructing highly adsorptive and catalyzing heterostructures has been widely developed, such as TiN–TiO2, MoN–VN, and WS2–WO3. In fact, the anchoring of polysulfides as well as Li2S precipitation are part of a continuous multielectron redox reaction in a working battery, and thus an integrated platform, such as 1T MoS2 NDs in this work, enabling smooth “immobilization–diffusion–conversion” is highly appealing. The unique advantages for 1T MoS2 ND can be summarized as following: (i) the edge-rich NDs with an intrinsically strong affinity to polysulfides serve as anchoring sites for LPSs and accelerate their reduction, which contributes to the long cycle life and high sulfur utilization; (ii) the highly conductive and catalytic nature of 1T MoS2 NDs uniformly loaded on conductive substrates can facilitate Li–S reaction kinetics (Fig. S14, ESI†) and reduce the cell resistance, which benefits the high rate performance of MoS2 ND-modified cathodes; (iii) the well-defined morphology and phase of MoS2 maximize the active sites to fully demonstrate their potential for Li–S chemistry, which enables a boost of the electrochemical performance with a small amount of electrochemical inert catalysts. In addition, post-mortem analyses revealed that MoS2 NDs/porous carbon remained stable after cycling (Fig. S15, ESI†). To further determine whether the excellent catalytic performance of the MoS2 NDs could be retained during long-term cycling, the MoS2 ND/porous carbon/Li2S6 cathode was prolonged to 500 cycles at 0.5C (Fig. S16, ESI†), and exhibited only a low capacity fading rate of 0.08% per cycle, directly indicating the stability of the MoS2 NDs as a catalyst in long-term Li–S batteries. Finally, thanks to the facile fabrication method and the low content needed to improve LSB performance, the large-scale application of 1T MoS2 NDs in high-energy LSBs should not be problematic.

Question: What's the cathode?
Answer: MoS2 ND-modified
To obtain strong immobilization and fast conversion kinetics for polysulfides, the concept of constructing highly adsorptive and catalyzing heterostructures has been widely developed, such as TiN–TiO2, MoN–VN, and WS2–WO3. In fact, the anchoring of polysulfides as well as Li2S precipitation are part of a continuous multielectron redox reaction in a working battery, and thus an integrated platform, such as 1T MoS2 NDs in this work, enabling smooth “immobilization–diffusion–conversion” is highly appealing. The unique advantages for 1T MoS2 ND can be summarized as following: (i) the edge-rich NDs with an intrinsically strong affinity to polysulfides serve as anchoring sites for LPSs and accelerate their reduction, which contributes to the long cycle life and high sulfur utilization; (ii) the highly conductive and catalytic nature of 1T MoS2 NDs uniformly loaded on conductive substrates can facilitate Li–S reaction kinetics (Fig. S14, ESI†) and reduce the cell resistance, which benefits the high rate performance of MoS2 ND-modified cathodes; (iii) the well-defined morphology and phase of MoS2 maximize the active sites to fully demonstrate their potential for Li–S chemistry, which enables a boost of the electrochemical performance with a small amount of electrochemical inert catalysts. In addition, post-mortem analyses revealed that MoS2 NDs/porous carbon remained stable after cycling (Fig. S15, ESI†). To further determine whether the excellent catalytic performance of the MoS2 NDs could be retained during long-term cycling, the MoS2 ND/porous carbon/Li2S6 cathode was prolonged to 500 cycles at 0.5C (Fig. S16, ESI†), and exhibited only a low capacity fading rate of 0.08% per cycle, directly indicating the stability of the MoS2 NDs as a catalyst in long-term Li–S batteries. Finally, thanks to the facile fabrication method and the low content needed to improve LSB performance, the large-scale application of 1T MoS2 NDs in high-energy LSBs should not be problematic.

Question: What's the cathode?
Answer: MoS2 ND/porous carbon/Li2S6
To investigate the failure mechanism of the overcharge protection of the TDAC, a scaled-up NCA/graphite cell was employed to reclaim enough electrolyte and electrode materials for a post-mortem analysis. The reclaimed electrolyte after overcharge was in a brownish color, which could be contributed by the dissolution of the transition metals (Co and Ni) from the cathode, the decomposition products of the electrolyte solvent, or the TDAC molecules in the harsh overcharge environment. MS, NMR and CV were used to analyse the reclaimed electrolyte in comparison with the fresh electrolyte. Fig. 5a shows a peak at a 283.2 mass/charge ratio (m/z) for both electrolytes. The MS data confirmed the existence of TDAC cation species in both electrolytes. The similar intensity of the peaks indicated that the concentration of the TDAC in the overcharged electrolyte was about the same as that in the fresh one. NMR analysis as shown in Fig. 5b also confirmed that most of the TDACs remained intact since no TDAC decomposed compounds were detected. The CV profile in Fig. 5c reveals a pair of reversible redox peaks at ∼1.35 V vs. Fc+/Fc, exhibiting no discrepancy against the fresh TDAC electrolyte. The reclaimed electrolyte was then injected into a cell with new NCA and graphite sheets. As displayed in Fig. 5d, the potential plateau at ∼4.5 V reappeared in the reassembled cell despite a lower CE and a decreased capacity.

Question: What's the cathode?
For full cells, commercial lithium iron phosphate (LFP) was used as the cathode material. A mixture of LFP powder, acetylene black (conductive additive) and polyvinylidene fluoride (PVDF) with a mass ratio of 8:1:1 in N-methyl-2-pyrrolidone (NMP) was first coated on aluminum foil, dried in a vacuum oven at 80 °C overnight and used as the LFP cathode. The areal mass loading of LFP was around 5 mg cm−2. The charge–discharge voltage was recorded from 2.0 to 4.0 V while the current rate varied from 0.2 to 2.0C (1C is equals to 170.0 mA h g−1). Electrochemical impedance spectroscopy (EIS) measurements were performed on an IVIUM electrochemical workstation with a frequency range of 105–0.01 Hz.

Question: What's the cathode?
Answer:  lithium iron phosphate (LFP)
For full cells, commercial lithium iron phosphate (LFP) was used as the cathode material. A mixture of LFP powder, acetylene black (conductive additive) and polyvinylidene fluoride (PVDF) with a mass ratio of 8:1:1 in N-methyl-2-pyrrolidone (NMP) was first coated on aluminum foil, dried in a vacuum oven at 80 °C overnight and used as the LFP cathode. The areal mass loading of LFP was around 5 mg cm−2. The charge–discharge voltage was recorded from 2.0 to 4.0 V while the current rate varied from 0.2 to 2.0C (1C is equals to 170.0 mA h g−1). Electrochemical impedance spectroscopy (EIS) measurements were performed on an IVIUM electrochemical workstation with a frequency range of 105–0.01 Hz.

Question: What's the cathode?
Answer: LFP
Lithium–sulphur (Li–S) batteries with high theoretical capacity, cost-effectiveness and environmental sustainability have attracted tremendous interest as the next generation rechargeable batteries. However, the performance of Li–S batteries is constrained by sulphur's low conductivity and large volume change during lithiation/delithiation. As the cathode matrix for the sulphur cathode, h-BNNS with nitrogen vacancies (v-BN) were found to improve the cycling performance of Li–S batteries. Compared with the pristine h-BN electrode, the v-BN electrode demonstrated significantly improved capacity. The engineered vacancies were believed to improve the kinetics of polysulphide conversion, lithium-ion diffusion rate, and protection of the Li anode from corrosion.

Question: What's the cathode?
Answer: sulphur
The hybrid Na–air battery was assembled in a sandwich structure. Initially, the anode part of the hybrid Na–air cell was fabricated in a glove box. The metallic sodium was cut and pressed into a sheet with a diameter of 10 mm as the anode, followed by the injection of organic electrolyte (1 M NaClO4 in tetraethylene glycol dimethyl ether) into the anode chamber. The solid electrolyte NASICON was sealed as the separator for the anode and cathode chamber, ensuring that one side of the NASICON was in contact with the organic electrolyte and the other side was exposed to air. The NASICON solid electrolyte was chosen to avoid direct contact between the aqueous electrolyte and Na anode, and specifically allow Na ions to shuttle between the anode and cathode during the reactions. The cathode compartment was built under ambient air by directly immersing the air electrode in the O2-saturated 0.1 M NaOH electrolyte. The as-prepared electrocatalysts coated on NF (diameter 10 mm) were directly used as air cathodes. For comparison, the 20% Pt/C (Macklin) and RuO2 catalysts cast on NF (diameter 10 mm) were prepared with a mass loading of 1 mg cm−2.

Question: What's the cathode?
Answer: air
Yao et al. presented a series of aqueous systems with quinone-based anodes and industrially established cathodes, which showed excellent stability, kinetics and energy density. Particularly for K-based batteries, PAQS P1 was paired with Ni(OH)2 in alkaline media (10 M KOH). The anode showed a capacity of 200 mA h g−1. At r.t., the full cell energy density (79 W h kg−1/138 W h L−1) was smaller than for a nickel metal hydride battery (180 W h kg−1/597 W h L−1), partially due to a relatively high anode potential. However, the capacity retention (88% after 1300 cycles) was better than for the best metal hydrides. Moreover, the capacity of PAQS decreased only by 7% as the temperature decreased from 25 to −25 °C. It is in contrast with Ni-MmH, whose energy density significantly decreases at lower temperatures.

Question: What's the cathode?
Compared with graphite, Bi, Sb and P, organic-based materials are less attractive in terms of the potentials. The electrode capacities are also generally lower, although several materials with high demetalation potentials showed a Qe of above 250 mA h g−1. Areal capacities (Chart 5c) are mostly comparable for organic-based materials and the benchmarks, except for graphite, for which very high loadings (up to 28.56 mg cm−2, corresponding to ∼7.4 mA h cm−2) were demonstrated. Similar to the cathodes (Section 2.7), the material loading of the anodes is typically left unoptimized.

Question: What's the cathode?
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 cathode?