milerssliu/battery-device-data-qa huggingface dataset:
The wettability of electrodes is well known as an important characteristic governing the interaction between the electrolyte and electrode as well as the charge transfer at the interface. As shown in Fig. S6,† the water contact angle (WCA) of COG is measured to be 0°, and the total spreading and penetration time (TSPT) of a water drop is about 3.17 s, indicating the inherent hydrophilicity of the COG. This should be attributed to the presence of some heteroatoms in natural reed straw, leading to heteroatom doping during the carbonization process and hence improved hydrophilicity of carbon materials. In contrast, the TSPT of COG@Zn, porous COG@MnO2 and bulk COG@MnO2 is reduced to 0.92 s, 0.42 s and 0.54 s, respectively. The results indicate that the surface wettability of the electrodes has been enhanced from hydrophilic to super-hydrophilic with the incorporation of MnO2 and Zn nanosheets. As is well known, MnO2 and Zn are inherently hydrophilic. In this case, the nanosheet structure increases the roughness of the material's surface, thereby further improving the hydrophilicity of the material. This favors the accessibility of the electrolyte at the surface of the electrodes and the charge transfer between them, giving rise to enhanced electrochemical performance.

Question: What's the electrolyte?
The Li-metal anode is considered an essential component for obtaining the expected Li–S battery performance. This is because of Li's extremely low negative electrochemical potential, very high theoretical specific capacity, and low density. However, the Li-metal anode has additional issues. Safety concerns arise because of the possibility of cell damage or manufacturing failures due to Li-metal's high reactivity, as well as due to the dendrite formation throughout cycling processes which can cause short circuits if dendrites reach the cathode. The electrolyte (salt and solvent) plays a vital role for rapid lithium transport and providing stability even near the highly reactive lithium surface. At the Li surface, electrolyte decomposition due to reduction reactions triggered by their low electrochemical stability leads to the growth of a multicomponent passivating film. This film, known as the solid electrolyte interphase (SEI) may have beneficial passivation properties, or, quite the opposite, may be a cause of irreversible capacity loss. The specific film behavior depends on its chemical composition, structure, and thickness. Moreover, it has been found the SEI properties depend largely on the solvent, salt, and additives used as well as on the electrode structure. Therefore, understanding the role of the electrolyte in SEI formation and its properties should be a useful strategy for controlling dendrite formation, reducing the effects of anode degradation and stabilizing the surface, thus, potentially improving the performance, cycling and safety of the batteries.

Question: What's the anode?
Answer: Li-metal
The Li-metal anode is considered an essential component for obtaining the expected Li–S battery performance. This is because of Li's extremely low negative electrochemical potential, very high theoretical specific capacity, and low density. However, the Li-metal anode has additional issues. Safety concerns arise because of the possibility of cell damage or manufacturing failures due to Li-metal's high reactivity, as well as due to the dendrite formation throughout cycling processes which can cause short circuits if dendrites reach the cathode. The electrolyte (salt and solvent) plays a vital role for rapid lithium transport and providing stability even near the highly reactive lithium surface. At the Li surface, electrolyte decomposition due to reduction reactions triggered by their low electrochemical stability leads to the growth of a multicomponent passivating film. This film, known as the solid electrolyte interphase (SEI) may have beneficial passivation properties, or, quite the opposite, may be a cause of irreversible capacity loss. The specific film behavior depends on its chemical composition, structure, and thickness. Moreover, it has been found the SEI properties depend largely on the solvent, salt, and additives used as well as on the electrode structure. Therefore, understanding the role of the electrolyte in SEI formation and its properties should be a useful strategy for controlling dendrite formation, reducing the effects of anode degradation and stabilizing the surface, thus, potentially improving the performance, cycling and safety of the batteries.

Question: What's the electrolyte?
The Li-metal anode is considered an essential component for obtaining the expected Li–S battery performance. This is because of Li's extremely low negative electrochemical potential, very high theoretical specific capacity, and low density. However, the Li-metal anode has additional issues. Safety concerns arise because of the possibility of cell damage or manufacturing failures due to Li-metal's high reactivity, as well as due to the dendrite formation throughout cycling processes which can cause short circuits if dendrites reach the cathode. The electrolyte (salt and solvent) plays a vital role for rapid lithium transport and providing stability even near the highly reactive lithium surface. At the Li surface, electrolyte decomposition due to reduction reactions triggered by their low electrochemical stability leads to the growth of a multicomponent passivating film. This film, known as the solid electrolyte interphase (SEI) may have beneficial passivation properties, or, quite the opposite, may be a cause of irreversible capacity loss. The specific film behavior depends on its chemical composition, structure, and thickness. Moreover, it has been found the SEI properties depend largely on the solvent, salt, and additives used as well as on the electrode structure. Therefore, understanding the role of the electrolyte in SEI formation and its properties should be a useful strategy for controlling dendrite formation, reducing the effects of anode degradation and stabilizing the surface, thus, potentially improving the performance, cycling and safety of the batteries.

Question: What's the anode?
Answer:  Li-metal
In order to achieve higher power/energy densities for electrochemical energy storage, dual-ion batteries (DIBs), relying on the migration of both cations and anions to store charge concurrently, have been developed. Compared with lithium ion batteries, dual-ion migration behavior can shorten the charge carrier distance. From a cation perspective, lithium ions, as a charge carrier, have contributed to energy storage for several decades. However, many issues have also been raised, such as safety, excessive resource consumption, and environmental pollution. In the process of searching for substitutes, sodium ions, zinc ions, aluminum ions, and other metal ions have been investigated as charge carriers. Non-lithium electrochemical energy storage systems have shown signs of progress. However, no matter how they were improved, metal dendrites have still remained present during the anodic process. To address this limitation, the non-metal ionic liquid EMIm+[PF6]− has been employed as an electrolyte to realize charge transport. Unfortunately, due to the larger radius of EMIm+ (vertical: 4.3 Å; horizontal: 7.6 Å), it is not possible for traditional graphite anodes to provide a high intercalation capacity. Selecting new electrode materials to achieve the intercalation/deintercalation of EMIm+ can be a route to overcome this bottleneck limitation.

Question: What's the anode?
Answer: graphite
In order to achieve higher power/energy densities for electrochemical energy storage, dual-ion batteries (DIBs), relying on the migration of both cations and anions to store charge concurrently, have been developed. Compared with lithium ion batteries, dual-ion migration behavior can shorten the charge carrier distance. From a cation perspective, lithium ions, as a charge carrier, have contributed to energy storage for several decades. However, many issues have also been raised, such as safety, excessive resource consumption, and environmental pollution. In the process of searching for substitutes, sodium ions, zinc ions, aluminum ions, and other metal ions have been investigated as charge carriers. Non-lithium electrochemical energy storage systems have shown signs of progress. However, no matter how they were improved, metal dendrites have still remained present during the anodic process. To address this limitation, the non-metal ionic liquid EMIm+[PF6]− has been employed as an electrolyte to realize charge transport. Unfortunately, due to the larger radius of EMIm+ (vertical: 4.3 Å; horizontal: 7.6 Å), it is not possible for traditional graphite anodes to provide a high intercalation capacity. Selecting new electrode materials to achieve the intercalation/deintercalation of EMIm+ can be a route to overcome this bottleneck limitation.

Question: What's the electrolyte?
Answer: EMIm+[PF6]−
To better visualize the local contact loss distribution around the cathode particles, a single NMC particle and its surrounding voids in the sample cycled 50 times were isolated from the larger volume and are shown in Fig. 4(f). The spherical NMC particle at the center is shown in grey, and the surrounding voids are shown in red. The voids are much more concentrated on the right side of the NMC particle, suggesting that the contact loss areas caused by the cathode particle volume shrinking will mostly be on one side of the particle, rather than uniformly distributed around the particle. This is expected because the presence of voids on one side of the particle is sufficient to release the strain caused by the particle volume change. This concentration of the decohered area in the cathode particle may aggravate its effect on capacity loss as now all the Li ions going in and out of the area under the contact loss have a much larger distance to travel before they reach the solid electrolyte. This is in contrast to if the contact loss area were homogeneously dispersed across the cathode particle. In the latter case, diffusion gradients parallel to the surface, resulting from blocked-out surface area for Li to enter or leave the particle, would rapidly fade out in the cathode particle.

Question: What's the cathode?
To better visualize the local contact loss distribution around the cathode particles, a single NMC particle and its surrounding voids in the sample cycled 50 times were isolated from the larger volume and are shown in Fig. 4(f). The spherical NMC particle at the center is shown in grey, and the surrounding voids are shown in red. The voids are much more concentrated on the right side of the NMC particle, suggesting that the contact loss areas caused by the cathode particle volume shrinking will mostly be on one side of the particle, rather than uniformly distributed around the particle. This is expected because the presence of voids on one side of the particle is sufficient to release the strain caused by the particle volume change. This concentration of the decohered area in the cathode particle may aggravate its effect on capacity loss as now all the Li ions going in and out of the area under the contact loss have a much larger distance to travel before they reach the solid electrolyte. This is in contrast to if the contact loss area were homogeneously dispersed across the cathode particle. In the latter case, diffusion gradients parallel to the surface, resulting from blocked-out surface area for Li to enter or leave the particle, would rapidly fade out in the cathode particle.

Question: What's the electrolyte?
Even though the SEI film is supposed to act as an insulator being a barrier for electron transfer, at the initial nucleation stages its structure may favor electron transport. This may occur because of the differences between the amorphous character of nucleating crystals and their bulk theoretical structures, as has been found in some bulk insulator materials where changes in the electronic conductivity were observed in ultra-thin films showing a semiconductor behavior. This capability of conducting electrons of imperfectly formed SEI nuclei and phases could contribute to the growth mechanism that keeps the SEI forming until it reaches hundreds of nanometers. Another important reason for the continuous SEI growth is the presence of radical charged species that result from the SEI reactions and are able to diffuse toward the vicinity of the electrolyte inducing further reactions. Several experimental and theoretical works have studied the various stages of the SEI formation and growth process while other authors have proposed the formation of artificial SEI layers by pretreating the anode before the battery is assembled. For the early stages of the SEI formation it is crucial to improve the understanding of electrolyte decomposition by characterizing the reaction mechanisms of electrolytes typically used in battery systems. It is known that carbonate solvents have low stability when implemented with Li-metal anodes, while ether-based solvents like dimethoxyethane (DME) and dioxalane (DOL) have shown better stability with respect to the Li-metal anode and are frequently used for these battery systems. However, solvent and salt molecules decomposition are still observed and in spite of the advances reached both from experimental and theoretical studies, the mechanisms of these processes are not yet well understood.

Question: What's the anode?
Answer: Li-metal
Even though the SEI film is supposed to act as an insulator being a barrier for electron transfer, at the initial nucleation stages its structure may favor electron transport. This may occur because of the differences between the amorphous character of nucleating crystals and their bulk theoretical structures, as has been found in some bulk insulator materials where changes in the electronic conductivity were observed in ultra-thin films showing a semiconductor behavior. This capability of conducting electrons of imperfectly formed SEI nuclei and phases could contribute to the growth mechanism that keeps the SEI forming until it reaches hundreds of nanometers. Another important reason for the continuous SEI growth is the presence of radical charged species that result from the SEI reactions and are able to diffuse toward the vicinity of the electrolyte inducing further reactions. Several experimental and theoretical works have studied the various stages of the SEI formation and growth process while other authors have proposed the formation of artificial SEI layers by pretreating the anode before the battery is assembled. For the early stages of the SEI formation it is crucial to improve the understanding of electrolyte decomposition by characterizing the reaction mechanisms of electrolytes typically used in battery systems. It is known that carbonate solvents have low stability when implemented with Li-metal anodes, while ether-based solvents like dimethoxyethane (DME) and dioxalane (DOL) have shown better stability with respect to the Li-metal anode and are frequently used for these battery systems. However, solvent and salt molecules decomposition are still observed and in spite of the advances reached both from experimental and theoretical studies, the mechanisms of these processes are not yet well understood.

Question: What's the electrolyte?
Even though the SEI film is supposed to act as an insulator being a barrier for electron transfer, at the initial nucleation stages its structure may favor electron transport. This may occur because of the differences between the amorphous character of nucleating crystals and their bulk theoretical structures, as has been found in some bulk insulator materials where changes in the electronic conductivity were observed in ultra-thin films showing a semiconductor behavior. This capability of conducting electrons of imperfectly formed SEI nuclei and phases could contribute to the growth mechanism that keeps the SEI forming until it reaches hundreds of nanometers. Another important reason for the continuous SEI growth is the presence of radical charged species that result from the SEI reactions and are able to diffuse toward the vicinity of the electrolyte inducing further reactions. Several experimental and theoretical works have studied the various stages of the SEI formation and growth process while other authors have proposed the formation of artificial SEI layers by pretreating the anode before the battery is assembled. For the early stages of the SEI formation it is crucial to improve the understanding of electrolyte decomposition by characterizing the reaction mechanisms of electrolytes typically used in battery systems. It is known that carbonate solvents have low stability when implemented with Li-metal anodes, while ether-based solvents like dimethoxyethane (DME) and dioxalane (DOL) have shown better stability with respect to the Li-metal anode and are frequently used for these battery systems. However, solvent and salt molecules decomposition are still observed and in spite of the advances reached both from experimental and theoretical studies, the mechanisms of these processes are not yet well understood.

Question: What's the anode?
Answer:  Li-metal
The electrochemical performance of the 400-KOH-Ti3C2 anode was measured in a three-electrode system with the 2 M H2SO4 solution serving as the electrolyte. To determine the potential range of the 400-KOH-Ti3C2 electrode in this acid electrolyte, the CV curves of the 400-KOH-Ti3C2 electrode were collected in various potential windows of −0.7 to 0.3 V, −0.6 to 0.3 V, −0.5 to 0.3 V and −0.4 to 0.3 V (vs. Ag/AgCl) at a scan rate of 5 mV s−1 (Fig. S6†). It is found that the potential window of the 400-KOH-Ti3C2 electrode can be stably extended to −0.6 V (vs. Ag/AgCl) without the decomposition of the electrolyte. Thus, the potential range of the 400-KOH-Ti3C2 electrode is fixed at −0.6–0.3 V (vs. Ag/AgCl) in 2 M H2SO4 solution. To further evaluate the stable potential window of the 400-KOH-Ti3C2 electrode, we collected CV curves at various scan rates in the potential window of −0.6–0.3 V (vs. Ag/AgCl) as shown in Fig. 2a. The shape of CV curves can be well retained even at a high scan rate of 200 mV s−1, indicating good rate capability of the 400-KOH-Ti3C2 electrode. Except for CV measurements, the galvanostatic discharge–charge profiles of the 400-KOH-Ti3C2 electrode at various current densities were recorded as displayed in Fig. 2b. The discharge–charge curves exhibit a triangular symmetric shape with an inappreciable deviation, suggesting high reversibility and prominent pseudocapacitive behavior. Based on the above discharge–charge curves, the specific capacitance of the 400-KOH-Ti3C2 electrode is calculated to be 334.5 F g−1 at 1 A g−1. Even at 100 A g−1, the 400-KOH-Ti3C2 electrode still retains a specific capacitance of 93.3 F g−1 (Fig. 2c). Such high specific capacitance of the 400-KOH-Ti3C2 electrode should be attributed to the large interlayer distance, which provides more accessible active sites for the electrolyte ionic diffusion and electrochemical reaction. To illustrate this view, EIS measurements were performed at a potential of −0.1 V (vs. Ag/AgCl) for the 400-KOH-Ti3C2 electrode. The corresponding Nyquist plot of the 400-KOH-Ti3C2 electrode (Fig. 2d) shows a negligible semicircle and a quite small charge transfer resistance (Rct) of 1.2 Ω, which is obviously lower than that of original Ti3C2Tx (1.8 Ω, Fig. S7†), revealing a fast ion transport and good electronic conductivity for the 400-KOH-Ti3C2 electrode. The Nyquist plots are fitted with the equivalent circuit model shown in Fig. S8.† In addition, the 400-KOH-Ti3C2 electrode shows a stable cycle performance at 4 A g−1, maintaining a capacitance retention of about 87% over 40000 cycles and almost 100% coulombic efficiency. Such excellent cycling stability is comparable to that of most recently reported electrode materials for supercapacitors (see Table S1†). Furthermore, the SEM images of the 400-KOH-Ti3C2 electrode after 5000 cycles show that the layered structure of 400-KOH-Ti3C2 is well retained after cycling (Fig. S9†). It is noteworthy that the capacitance of the 400-KOH-Ti3C2 electrode decreases significantly in the first few hundred cycles, which is likely related to the phase transition of the electrode material.

Question: What's the anode?
Answer: 400-KOH-Ti3C2
The electrochemical performance of the 400-KOH-Ti3C2 anode was measured in a three-electrode system with the 2 M H2SO4 solution serving as the electrolyte. To determine the potential range of the 400-KOH-Ti3C2 electrode in this acid electrolyte, the CV curves of the 400-KOH-Ti3C2 electrode were collected in various potential windows of −0.7 to 0.3 V, −0.6 to 0.3 V, −0.5 to 0.3 V and −0.4 to 0.3 V (vs. Ag/AgCl) at a scan rate of 5 mV s−1 (Fig. S6†). It is found that the potential window of the 400-KOH-Ti3C2 electrode can be stably extended to −0.6 V (vs. Ag/AgCl) without the decomposition of the electrolyte. Thus, the potential range of the 400-KOH-Ti3C2 electrode is fixed at −0.6–0.3 V (vs. Ag/AgCl) in 2 M H2SO4 solution. To further evaluate the stable potential window of the 400-KOH-Ti3C2 electrode, we collected CV curves at various scan rates in the potential window of −0.6–0.3 V (vs. Ag/AgCl) as shown in Fig. 2a. The shape of CV curves can be well retained even at a high scan rate of 200 mV s−1, indicating good rate capability of the 400-KOH-Ti3C2 electrode. Except for CV measurements, the galvanostatic discharge–charge profiles of the 400-KOH-Ti3C2 electrode at various current densities were recorded as displayed in Fig. 2b. The discharge–charge curves exhibit a triangular symmetric shape with an inappreciable deviation, suggesting high reversibility and prominent pseudocapacitive behavior. Based on the above discharge–charge curves, the specific capacitance of the 400-KOH-Ti3C2 electrode is calculated to be 334.5 F g−1 at 1 A g−1. Even at 100 A g−1, the 400-KOH-Ti3C2 electrode still retains a specific capacitance of 93.3 F g−1 (Fig. 2c). Such high specific capacitance of the 400-KOH-Ti3C2 electrode should be attributed to the large interlayer distance, which provides more accessible active sites for the electrolyte ionic diffusion and electrochemical reaction. To illustrate this view, EIS measurements were performed at a potential of −0.1 V (vs. Ag/AgCl) for the 400-KOH-Ti3C2 electrode. The corresponding Nyquist plot of the 400-KOH-Ti3C2 electrode (Fig. 2d) shows a negligible semicircle and a quite small charge transfer resistance (Rct) of 1.2 Ω, which is obviously lower than that of original Ti3C2Tx (1.8 Ω, Fig. S7†), revealing a fast ion transport and good electronic conductivity for the 400-KOH-Ti3C2 electrode. The Nyquist plots are fitted with the equivalent circuit model shown in Fig. S8.† In addition, the 400-KOH-Ti3C2 electrode shows a stable cycle performance at 4 A g−1, maintaining a capacitance retention of about 87% over 40000 cycles and almost 100% coulombic efficiency. Such excellent cycling stability is comparable to that of most recently reported electrode materials for supercapacitors (see Table S1†). Furthermore, the SEM images of the 400-KOH-Ti3C2 electrode after 5000 cycles show that the layered structure of 400-KOH-Ti3C2 is well retained after cycling (Fig. S9†). It is noteworthy that the capacitance of the 400-KOH-Ti3C2 electrode decreases significantly in the first few hundred cycles, which is likely related to the phase transition of the electrode material.

Question: What's the electrolyte?
Answer:  2 M H2SO4