milerssliu/battery-device-data-qa huggingface dataset:
Although tremendous efforts have resulted in the great advances in recent years, O3-type layered oxide cathode materials have been plagued by the issue of poor thermal stability and structural stability against a humid atmosphere, which are favorable properties for practical application. To confirm the practical acceptability, we first checked the thermal stability and air-stability of the Na0.98Ca0.01[Ni0.5Mn0.5]O2 cathode by comparing it with the Na[Ni0.5Mn0.5]O2 cathode. Differential scanning calorimetry (DSC) was performed to observe the exothermic reactions of the deeply de-sodiated electrodes (highly unstable state) collected from cells charged to 4.3 V (vs. Na/Na+) after the first cycle. The results are plotted in Fig. S15,† showing both onset temperature of the exothermic reactions and the total specific heat generation. Although a similar amount of Na+ ions (according to charge capacities) was extracted from the crystal structure, the thermal reaction between NaxCa0.01[Ni0.5Mn0.5]O2 and Nax[Ni0.5Mn0.5]O2 (x is close to 0) cathodes was different. In contrast, the Nax[Ni0.5Mn0.5]O2 electrode displayed an exothermic peak at 254.1 °C with a heat generation of 634.5 J g−1, the NaxCa0.01[Ni0.5Mn0.5]O2 electrode showed a lower heat generation of 352 J g−1 and an exothermic peak at 258.9 °C. It should be noted that the thermal reaction is related to the evolution of oxygen from the crystal structure because the oxygen released from the cathode materials can react with the electrolyte solution and undergo a redox reaction. Therefore, it is strongly believed that the improved thermal stability of the Ca-substituted cathode likely resulted from the strong interaction of immobile Ca2+ with O2−, which suppresses the rate of release of thermal oxygen from the highly oxidized cathode material.

Question: What's the cathode?
Answer: O3-type layered oxide
Although tremendous efforts have resulted in the great advances in recent years, O3-type layered oxide cathode materials have been plagued by the issue of poor thermal stability and structural stability against a humid atmosphere, which are favorable properties for practical application. To confirm the practical acceptability, we first checked the thermal stability and air-stability of the Na0.98Ca0.01[Ni0.5Mn0.5]O2 cathode by comparing it with the Na[Ni0.5Mn0.5]O2 cathode. Differential scanning calorimetry (DSC) was performed to observe the exothermic reactions of the deeply de-sodiated electrodes (highly unstable state) collected from cells charged to 4.3 V (vs. Na/Na+) after the first cycle. The results are plotted in Fig. S15,† showing both onset temperature of the exothermic reactions and the total specific heat generation. Although a similar amount of Na+ ions (according to charge capacities) was extracted from the crystal structure, the thermal reaction between NaxCa0.01[Ni0.5Mn0.5]O2 and Nax[Ni0.5Mn0.5]O2 (x is close to 0) cathodes was different. In contrast, the Nax[Ni0.5Mn0.5]O2 electrode displayed an exothermic peak at 254.1 °C with a heat generation of 634.5 J g−1, the NaxCa0.01[Ni0.5Mn0.5]O2 electrode showed a lower heat generation of 352 J g−1 and an exothermic peak at 258.9 °C. It should be noted that the thermal reaction is related to the evolution of oxygen from the crystal structure because the oxygen released from the cathode materials can react with the electrolyte solution and undergo a redox reaction. Therefore, it is strongly believed that the improved thermal stability of the Ca-substituted cathode likely resulted from the strong interaction of immobile Ca2+ with O2−, which suppresses the rate of release of thermal oxygen from the highly oxidized cathode material.

Question: What's the electrolyte?
Although tremendous efforts have resulted in the great advances in recent years, O3-type layered oxide cathode materials have been plagued by the issue of poor thermal stability and structural stability against a humid atmosphere, which are favorable properties for practical application. To confirm the practical acceptability, we first checked the thermal stability and air-stability of the Na0.98Ca0.01[Ni0.5Mn0.5]O2 cathode by comparing it with the Na[Ni0.5Mn0.5]O2 cathode. Differential scanning calorimetry (DSC) was performed to observe the exothermic reactions of the deeply de-sodiated electrodes (highly unstable state) collected from cells charged to 4.3 V (vs. Na/Na+) after the first cycle. The results are plotted in Fig. S15,† showing both onset temperature of the exothermic reactions and the total specific heat generation. Although a similar amount of Na+ ions (according to charge capacities) was extracted from the crystal structure, the thermal reaction between NaxCa0.01[Ni0.5Mn0.5]O2 and Nax[Ni0.5Mn0.5]O2 (x is close to 0) cathodes was different. In contrast, the Nax[Ni0.5Mn0.5]O2 electrode displayed an exothermic peak at 254.1 °C with a heat generation of 634.5 J g−1, the NaxCa0.01[Ni0.5Mn0.5]O2 electrode showed a lower heat generation of 352 J g−1 and an exothermic peak at 258.9 °C. It should be noted that the thermal reaction is related to the evolution of oxygen from the crystal structure because the oxygen released from the cathode materials can react with the electrolyte solution and undergo a redox reaction. Therefore, it is strongly believed that the improved thermal stability of the Ca-substituted cathode likely resulted from the strong interaction of immobile Ca2+ with O2−, which suppresses the rate of release of thermal oxygen from the highly oxidized cathode material.

Question: What's the cathode?
Answer: Na0.98Ca0.01[Ni0.5Mn0.5]O2
On the other hand, the HER and OER are the two half-reactions involved in electrocatalytic water splitting. These hydrogen-based and oxygen-based alkaline electrochemical reactions are often hindered by sluggish kinetics, which leads to a large overpotential and low round-trip efficiency. Enormous effort has been devoted to the development of highly efficient electrocatalysts for the HER and OER based on the structure–activity relationship, to increase the reaction rate and efficiency of the total system. Accordingly, Liu et al. reported AuPtPdRhRu alloy nanoparticles for HER application by an ultrasonication-assisted wet chemical method (Fig. 5a and b). The as-synthesized quinary AuPtPdRhRu nanoparticles on carbon (AuPtPdRhRu/C), whose average diameter is 2.6 ± 0.3 nm, exhibited excellent HER activity and durability in a 1.0 M KOH electrolyte. The required overpotential of AuPtPdRhRu/C to drive a current density of −30 mA cm−2 was 190 mV, which is smaller than those of quaternary AuPtPdRh/C (260 mV) and ternary AuPtRh/C (600 mV) catalysts. AuPtPdRhRu/C exhibited a lower Tafel slope of 62 mV dec−1 compared to AuPtPdRh/C (91 mV dec−1), AuPtPd/C (177 mV dec−1), and benchmark Pt/C (77 mV dec−1) catalysts, indicating its superior activity toward the alkaline HER. Moreover, AuPtPdRhRu/C exhibited stable electrocatalytic performance over 8 h, verified by chronopotentiometry at a current density of 100 mA cm−2. Likewise, Qiu et al. reported noble-metal free nanoporous HEA catalysts for the OER under alkaline conditions. Quinary nanoporous NiCoFeAlX (np-NiCoFeAlX, X = V, Cr, Mn, Cu, Zr, Nb, Mo) and senary np-MoCuNiCoFeAl catalysts were fabricated by a mechanical alloying and chemical dealloying strategy. Among the catalysts, np-MoNiCoFeAl exhibited the lowest OER overpotential (240 mV) to drive a current density of 10 mA cm−2 in a 1.0 M KOH electrolyte. Moreover, the np-MoNiCoFeAl catalyst also showed a smaller Tafel slope of 46 mV dec−1, compared to ternary np-NiFeAl (62 mV dec−1) and quaternary np-NiCoFeAl (61 mV dec−1). Moreover, the quinary np-MoNiCoFeAl exhibited high durability compared to ternary and quaternary catalysts, and retained more than 95% of its initial activity after 2000 potential cycles. Due to the oxidative potential under OER conditions, the surface of np-MoNiCoFeAl might undergo oxidation, forming surface oxides on the HEA surfaces. After a chronopotentiometry test at 20 mA cm−2 for 50 h, however, the five elements were still uniformly distributed in np-MoNiCoFeAl, forming a high-entropy-oxide (HEO) skin that exhibits high-entropy driven stability.

Question: What's the cathode?
Answer: 1.0 M KOH
Lithium sulfur batteries (LSBs) with high theoretical energy densities of 2600 W h kg−1 are considered promising candidates to take precedence over lithium ion batteries (LIBs) in meeting the emerging and demanding applications, such as electric vehicles and smart grids. However, the practical implementation of LSBs is plagued by several fundamental challenges, including the dissolution and shuttling of lithium polysulfides (LPSs), the insulating nature of sulfur and lithium sulfides, and the instability of Li metal anodes. In the past decade, progress in structural design and materials chemistry has induced discernible improvements in battery performance. For instance, a high sulfur utilization of 1620 mA h g−1 with long cycle life of 1000 cycles was reported for sulfur/graphene composite electrodes. However, statistical analysis of the reported cathodes indicates that the major cathodes tested under low sulfur loadings (<2 mg cm−2) and high electrolyte/sulfur (E/S) ratios (>10 μL mg−1) are unacceptable for practical applications. Based on theoretical estimations, LSBs should possess sulfur loadings of above 7 mg cm−2, areal capacities of over 6 mA h cm−2, and E/S ratios of less than 5 μL mg−1, to outperform current LIBs in terms of the practical energy density.

Question: What's the electrolyte?
Over the past several decades, rechargeable lithium-ion batteries (LIBs) have been widely used in the energy storage market of portable electronic devices and electric vehicles. However, the scarcity and rising costs of Li raw materials have restricted the further large-scale commercialization of LIBs, and thus have spurred extensive research in seeking cost-effective and more reliable energy storage systems. Among various promising alternatives, Na-ion batteries (NIBs) have attracted considerable attention because of the high abundance and low cost of Na resources. Of various anode candidates for NIBs, Na metal anodes are prized for their high specific capacity (1166 mA h g−1) and low electrochemical potential (−2.714 V vs. standard hydrogen electrode). However, the naturally formed solid electrolyte interphase (SEI) that originates from the instantaneous reaction between the highly reactive Na and electrolyte solvents is generally non-uniform and fragile. The heterogeneous feature easily causes uneven Na deposition and the formation of Na dendrites, and thus brings about serious safety issues. Additionally, the fragile SEI cannot tolerate huge volume changes upon the repetitive plating/stripping process, which gives rise to repeated breakdown/repair of the SEI, leading to a low coulombic efficiency (CE) and short cycle life. These issues impede the practical applications of Na metal anodes.

Question: What's the anode?
Answer: Na metal
Over the past several decades, rechargeable lithium-ion batteries (LIBs) have been widely used in the energy storage market of portable electronic devices and electric vehicles. However, the scarcity and rising costs of Li raw materials have restricted the further large-scale commercialization of LIBs, and thus have spurred extensive research in seeking cost-effective and more reliable energy storage systems. Among various promising alternatives, Na-ion batteries (NIBs) have attracted considerable attention because of the high abundance and low cost of Na resources. Of various anode candidates for NIBs, Na metal anodes are prized for their high specific capacity (1166 mA h g−1) and low electrochemical potential (−2.714 V vs. standard hydrogen electrode). However, the naturally formed solid electrolyte interphase (SEI) that originates from the instantaneous reaction between the highly reactive Na and electrolyte solvents is generally non-uniform and fragile. The heterogeneous feature easily causes uneven Na deposition and the formation of Na dendrites, and thus brings about serious safety issues. Additionally, the fragile SEI cannot tolerate huge volume changes upon the repetitive plating/stripping process, which gives rise to repeated breakdown/repair of the SEI, leading to a low coulombic efficiency (CE) and short cycle life. These issues impede the practical applications of Na metal anodes.

Question: What's the electrolyte?
To quantitatively evaluate the ECD performance, the difference (ΔT) in transmittance values in coloured (TC) and bleached (TB) states is defined as below: The measurement results regarding the visible light transmittance of the ECDs under coloured and bleached states according to various UV curing times of 0, 5, 10, and 20 minutes are presented in Fig. 3a and Fig. S4 (ESI†). To assess the ΔT value, the transmittance values at a wavelength of 550 nm were chosen (Fig. 3b). For the ECD with 5 min of curing, the ΔT was reduced from 54.7% to 51.7%, as shown in Fig. 3b and Table 1. As the UV curing time was delayed, the ΔT values were slightly decreased to approximately 50.0% primarily owing to the increased TC value. This suggests that the UV curing process can deteriorate the EC performance of ECDs. It could be inferred that immobile PMMA molecules block many of the reaction sites on the surfaces of both the electrodes. Fig. 3c shows the dynamic spectra of the UV-cured EDCs at a wavelength of 550 nm under a periodic bias voltage between −1.2 and 0 V. The reliabilities of all the UV-cured ECDs were maintained for the first five cycles, which is comparable to that of uncured ECD using the liquid electrolyte. Furthermore, their low driving voltage of −1.2 V and natural state (0 V) bleaching characteristics are beneficial for low-power devices such as Internet of Things (IoT) devices and wearable displays.

Question: What's the electrolyte?
Besides NiFe-based catalysts, the performance of transition metal sulfides can also be enhanced by Fe incorporation, similar to the effect of Fe-ion doping. For instance, Liu's group reported a novel HER candidate, namely, a Fe-doped NiS2 nanosheet, with high activity and long-time durability. The theoretical and experimental results show that Fe3+ doping into the surface lattice of the NiS2 (002) crystal plane can reduce the activation energy of H2 formation. Further, Fe-doped NiS2 nanosheets can be a bifunctional electrocatalyst with high activities toward both OER and HER in the same media. Sun's group reported the exploitation of iron-doped nickel disulfide nanoarrays on Ti substrate via subsequent sulfidation treatment and used it as a bifunctional electrocatalyst with overall water-splitting capacity. In addition, Cao's group prepared a vertically oriented Fe-doped Ni3S2-nanosheet-based bifunctional electrocatalyst toward both HER and OER with outstanding activity and stability in alkaline electrolytes. Based on detailed experiments and theoretical simulations, it was proved that the electrochemically active surface area, water adsorption ability, and hydrogen adsorption energy of Ni3S2 can be regulated via Fe doping (Fig. 5). For transition metal selenides, the effect of Fe incorporation is also evident. Yu and co-workers described ultrathin Fe-doped NiSe2 nanowires (diameter: <1.7 nm) via a soft-template-mediated colloidal synthesis strategy, further revealing the amorphous hydroxide layers formed in situ that contributed toward the enhanced OER activity. Moreover, Zhao et al. incorporated both Fe dopants and Co vacancies into atomically thin CoSe2 nanobelts for oxygen evolution catalysis, and the resultant CoSe2–DFe–VCo exhibits much higher catalytic activity than other defect-activated CoSe2 and previously reported FeCo compounds. Deeper characterizations and theoretical calculations identify the most active centers of Co2 sites that are adjacent to the VCo-nearest Fe site. Fe doping and Co vacancy can synergistically tune the electronic states of Co2 to a near-optimal value, resulting in considerably decreased binding energy of OH* and consequently lowering the catalytic overpotential.

Question: What's the electrolyte?
Answer: alkaline
Typical NASICON compounds (such as a NVP cathode and a NTP anode) suffering from severe performance degradation in aqueous electrolytes were employed. The crystal structures, X-ray diffraction (XRD) patterns and SEM images of the prepared NVP/C and NTP/C are shown in Fig. S7.† In Fig. S8,† all of the materials have two featured Raman shifts, in which the G-band (ordered graphitic structure) peak is at 1590 cm−1 and the D-band (disordered portion) is at 1352 cm−1. The thin carbon layer provides good electro-conductivity to NVP/C and NTP/C. In addition, the carbon content of the NVP/C and NTP/C composites measured by elemental analysis (Table S2†) and TG analysis (Fig. S9†) is approximately 3.5 wt%.

Question: What's the cathode?
Typical NASICON compounds (such as a NVP cathode and a NTP anode) suffering from severe performance degradation in aqueous electrolytes were employed. The crystal structures, X-ray diffraction (XRD) patterns and SEM images of the prepared NVP/C and NTP/C are shown in Fig. S7.† In Fig. S8,† all of the materials have two featured Raman shifts, in which the G-band (ordered graphitic structure) peak is at 1590 cm−1 and the D-band (disordered portion) is at 1352 cm−1. The thin carbon layer provides good electro-conductivity to NVP/C and NTP/C. In addition, the carbon content of the NVP/C and NTP/C composites measured by elemental analysis (Table S2†) and TG analysis (Fig. S9†) is approximately 3.5 wt%.

Question: What's the anode?
Answer: NTP
Typical NASICON compounds (such as a NVP cathode and a NTP anode) suffering from severe performance degradation in aqueous electrolytes were employed. The crystal structures, X-ray diffraction (XRD) patterns and SEM images of the prepared NVP/C and NTP/C are shown in Fig. S7.† In Fig. S8,† all of the materials have two featured Raman shifts, in which the G-band (ordered graphitic structure) peak is at 1590 cm−1 and the D-band (disordered portion) is at 1352 cm−1. The thin carbon layer provides good electro-conductivity to NVP/C and NTP/C. In addition, the carbon content of the NVP/C and NTP/C composites measured by elemental analysis (Table S2†) and TG analysis (Fig. S9†) is approximately 3.5 wt%.

Question: What's the electrolyte?
The nanomesh after galvanostatic EMD deposition is shown in Fig. 2c–e. The electrodeposition resulted in conformal coating of the nanowires with a 8.5 ± 1 nm thick EMD layer. Despite the limited pore size of the nanomesh, the coating was uniformly distributed throughout the depth of the nanowire network, without closing the pores within and at the top of the nanomesh (Fig. 2d). Such open porosity of the cathode is crucial to ensure its high contact area with the battery electrolyte and facilitate transport of Li+ into and out of the electrode. The excellent conformality of EMD on the nanomesh network can be ascribed to both the relatively slow diffusion of reactants through the growing oxide layer, and the pre-deposited MnO2 seed layer, which increases the homogeneity and coulombic efficiency of EMD electrodeposition. X-ray Photoemission Spectroscopy (XPS) confirmed that the as-deposited EMD consists of hydrated MnO2 (Fig. S2†), in agreement with previous observations on the hydrous nature of pristine EMD deposited from aqueous electrolytes. Note that the total thickness of the EMD-coated 3D electrode is much higher than the maximum attainable thickness of electrodeposited MnO2 on planar electrodes (500 nm on Ni and 1.5 μm on carbon-coated TiN), where the thicker EMD layers easily delaminate.

Question: What's the cathode?
The nanomesh after galvanostatic EMD deposition is shown in Fig. 2c–e. The electrodeposition resulted in conformal coating of the nanowires with a 8.5 ± 1 nm thick EMD layer. Despite the limited pore size of the nanomesh, the coating was uniformly distributed throughout the depth of the nanowire network, without closing the pores within and at the top of the nanomesh (Fig. 2d). Such open porosity of the cathode is crucial to ensure its high contact area with the battery electrolyte and facilitate transport of Li+ into and out of the electrode. The excellent conformality of EMD on the nanomesh network can be ascribed to both the relatively slow diffusion of reactants through the growing oxide layer, and the pre-deposited MnO2 seed layer, which increases the homogeneity and coulombic efficiency of EMD electrodeposition. X-ray Photoemission Spectroscopy (XPS) confirmed that the as-deposited EMD consists of hydrated MnO2 (Fig. S2†), in agreement with previous observations on the hydrous nature of pristine EMD deposited from aqueous electrolytes. Note that the total thickness of the EMD-coated 3D electrode is much higher than the maximum attainable thickness of electrodeposited MnO2 on planar electrodes (500 nm on Ni and 1.5 μm on carbon-coated TiN), where the thicker EMD layers easily delaminate.

Question: What's the electrolyte?
On the basis of the change in the direction of the exfoliating voltage, electrochemical exfoliation of 2D antimony, bismuth and their compounds can be divided into DC voltage exfoliation and square-wave voltage exfoliation. DC voltage exfoliation uses a DC power supply to provide the voltage, and the voltage direction does not change during the exfoliation process. The process of preparing 2D antimony, bismuth and their compounds by the DC voltage exfoliation method is similar to that of cathode exfoliation graphene. The exfoliation process was conducted by using a large block of antimony or bismuth or its compound as the cathode and platinum wire or foil as the anode and in an organic solution. This process applies a voltage to the bulk of antimony, bismuth and their compounds at the cathode, drives the insertion of cations in the electrolyte, and uses jet force that produces hydrogen to promote the peeling of antimony, bismuth and their compounds. In 2017, Li et al. illustrated the possible mechanism of cathodic exfoliation to prepare 2D Sb nanosheets in 0.5 M Na2SO4 solution. Driven by the voltage, the Na+ intercalation layer that accumulates at the negative electrode enters the interlayer of the bulk Sb crystal. Because a large amount of the Na+ intercalation layer enters the interlayer of the Sb crystal, the exfoliation of Sb is eventually promoted by the expansion force (Fig. 4a). Furthermore, the positive and negative voltage and the size of the electrolyte cations affect the efficiency of exfoliation.

Question: What's the cathode?
On the basis of the change in the direction of the exfoliating voltage, electrochemical exfoliation of 2D antimony, bismuth and their compounds can be divided into DC voltage exfoliation and square-wave voltage exfoliation. DC voltage exfoliation uses a DC power supply to provide the voltage, and the voltage direction does not change during the exfoliation process. The process of preparing 2D antimony, bismuth and their compounds by the DC voltage exfoliation method is similar to that of cathode exfoliation graphene. The exfoliation process was conducted by using a large block of antimony or bismuth or its compound as the cathode and platinum wire or foil as the anode and in an organic solution. This process applies a voltage to the bulk of antimony, bismuth and their compounds at the cathode, drives the insertion of cations in the electrolyte, and uses jet force that produces hydrogen to promote the peeling of antimony, bismuth and their compounds. In 2017, Li et al. illustrated the possible mechanism of cathodic exfoliation to prepare 2D Sb nanosheets in 0.5 M Na2SO4 solution. Driven by the voltage, the Na+ intercalation layer that accumulates at the negative electrode enters the interlayer of the bulk Sb crystal. Because a large amount of the Na+ intercalation layer enters the interlayer of the Sb crystal, the exfoliation of Sb is eventually promoted by the expansion force (Fig. 4a). Furthermore, the positive and negative voltage and the size of the electrolyte cations affect the efficiency of exfoliation.

Question: What's the anode?