milerssliu/battery-device-data-qa huggingface dataset:
Similar to graphene, carbon nanotubes (CNTs) with a unique 1D tubular structure and excellent electrical conductivity can also be introduced into electrospun CNFs in order to increase the electrochemical activity of the electrospun CNFs and influence their architecture. Growing CNTs on the surface of the electrospun CNFs could be an effective approach to enhance the capacitive performance of electrode materials in SCs. For instance, a symmetrical device based on CNF/CNT hybrid electrodes exhibited a specific capacitance of 3.35 ± 0.05 mF cm−2, which was 3.6 times higher than that of a pure CNF electrode-based device (0.91 ± 0.02 mF cm−2). A hierarchical nanostructure of CNFs/CNTs was synthesized through a CVD process by using C2H2 as the carbon precursor and Ni nanoparticles on CNFs as catalysts.Fig. 12c shows an SEM image of the CNFs/CNTs nanocomposites, demonstrating the formation of a hierarchical network structure consisting of densely grown CNTs on the surface of the CNFs. The obtained CNFs/CNT electrode showed a specific capacitance of 464.2 F g−1 at 0.5 A g−1 in 6 M KOH and excellent stability with 97% retention after 10000 cycles. The excellent performance was ascribed to the following aspects: (i) the intimate contact between the CNTs (to provide electrical conduction from the tip of each CNT to the edges and surfaces of the CNFs) and the CNFs; (ii) the interconnected and porous CNFs acting as an excellent path facilitated charge transfer and electrolyte permeation. Hierarchical CNFs/CNT hybrids were prepared via a tubular CVD growth process using Al/Fe composite catalysts. After KOH activation, the tips of CNTs in the hybrids can be well opened at 700 °C without changing the overall hierarchical structure. More interestingly, the tip-open CNFs/CNT hybrids showed a considerably improved specific capacitance, which increases to 3.3 times that of the pristine one. Moreover, sweep analysis indicated that the diffusion-type capacitance increases by 3.7 times while the Helmholtz-type capacitance increases by only 1.5 times, indicating that the tip-open CNTs contribute to ∼30% of the increase in double-layer capacitance. In another study, CNFs/CNT scaffolds were fabricated by the electrospinning technique combined with post-carbonization processes. The diameters of CNF skeletons, CNT density on CNF skeletons and length of CNTs were determined by the PAN concentration, Fe(acac)3 concentration in precursor solution and growth time of C2H2 flow, respectively. It was observed that a suitable size of CNF skeletons, CNT density and growth time of CNTs could greatly enhance the overall performance.

Question: What's the electrolyte?
Garnet-structured oxide electrolytes (Li7La3Zr2O12, LLZO) have significant advantage of being chemically and electrochemically stable against Li metals and allow implementation in Li metal batteries. However, a short-circuit failure due to Li penetration through the LLZO electrolyte has remained a crucial issue for safety and is a major hurdle for Li-based batteries to overcome. In, we investigated a mechanism of Li dendrite formation for the crystalline Ta-doped LLZO (LLZTO) electrolyte by examining their energy band structures and defect states using reflection electron energy loss spectroscopy (REELS), scanning photoelectron microscopy (SPEM), and nanoscale charge-based deep level transient spectroscopy (Nano Q-DLTS) techniques. The experimental results revealed that the Schottky barrier height (SBH) was lowered by 0.5 eV due to defect states localized in grain boundaries and that the metallic Li propagation along the grain boundaries is caused by the SBH reduction. Based on analytical results, the laser annealing of LLZTO was performed via bandgap engineering method to suppress the Li dendrite formation by forming a mixed surface layer of amorphous LLZTO and Li2O2, which has a wide bandgap to block the electron injection into the grain boundaries. The electrochemical measurements of laser-treated LLZTO demonstrated that the stability and cycling performance were significantly improved. This study sheds light on the importance of electronic structure, in particular, the defect states to develop high-performance oxide solid electrolytes for Li metal batteries and the practicality of surface modification by laser treatment.

Question: What's the electrolyte?
Answer: (Li7La3Zr2O12, LLZO)
Garnet-structured oxide electrolytes (Li7La3Zr2O12, LLZO) have significant advantage of being chemically and electrochemically stable against Li metals and allow implementation in Li metal batteries. However, a short-circuit failure due to Li penetration through the LLZO electrolyte has remained a crucial issue for safety and is a major hurdle for Li-based batteries to overcome. In, we investigated a mechanism of Li dendrite formation for the crystalline Ta-doped LLZO (LLZTO) electrolyte by examining their energy band structures and defect states using reflection electron energy loss spectroscopy (REELS), scanning photoelectron microscopy (SPEM), and nanoscale charge-based deep level transient spectroscopy (Nano Q-DLTS) techniques. The experimental results revealed that the Schottky barrier height (SBH) was lowered by 0.5 eV due to defect states localized in grain boundaries and that the metallic Li propagation along the grain boundaries is caused by the SBH reduction. Based on analytical results, the laser annealing of LLZTO was performed via bandgap engineering method to suppress the Li dendrite formation by forming a mixed surface layer of amorphous LLZTO and Li2O2, which has a wide bandgap to block the electron injection into the grain boundaries. The electrochemical measurements of laser-treated LLZTO demonstrated that the stability and cycling performance were significantly improved. This study sheds light on the importance of electronic structure, in particular, the defect states to develop high-performance oxide solid electrolytes for Li metal batteries and the practicality of surface modification by laser treatment.

Question: What's the electrolyte?
Answer: LLZO (LLZTO)
Unique graphene-like metallic Co9S8 with a morphology comprised of interconnected porous nanosheets that form a 3D network has been successfully synthesized by Nazar's group through a microwave solvothermal approach based on the reaction of cobalt chloride and TAA in a mixed solvent of water and triethylenetetramine at 160 °C for 1.5 h. Microwaves utilize a solvent dipole–microwave interaction that leads to rapidly superheated regions, triggering rapid nucleation and growth of particles. These distinctive synthesis conditions result in the formation of a long-range nanosheet structure of Co9S8 with a broad pore size distribution. N2 adsorption/desorption analysis indicates a high BET surface area of 108 m2 g−1 and a very large pore volume of 1.07 cm3 g−1 with the majority of pores in the range of 1.2–10 nm and the remainder distributed over 10–80 nm, indicating a texture incorporating micro-, meso-, and macro-pores. This high surface area and pore volume along with hierarchical porosity are vital to induce high intrinsic LiPS adsorptivity and enhance electrolyte penetration across thick electrodes. Li et al. presented the preparation of a S/C–SnS2 composite by ball milling sublimed sulfur, Ketjen Black, and ultrathin SnS2 nanosheets, where the 2D ultrathin nanosheets, fabricated by a one-pot reaction of SnCl4, TAA, and acetic acid, bring about a remarkably large surface area to enhance immobilization capability for LiPSs. In addition to those conventional methods, some innovative technologies can also delicately control the surface area, porosity, and/or polarity of metal sulfides. As an example, Xiao et al. demonstrated a green water-steam-etched approach for the fabrication of H- and O-incorporated porous TiS2 (HOPT) via heat treatment of a commercial TiS2 ball-milling product. During heat treatment, a mist of droplets from ultrapure water is passed into a quartz tube containing the ball-milled TiS2 using Ar-carrier gas. Interestingly, the time and temperature of water steam etching play pivotal roles in modulating the porosity of HOPT. Increasing the temperature from 100 to 500 °C, the specific surface area and pore volume of HOPT increase from 12.7 to 47 m2 g−1 and from 0.075 to 0.25 cm3 g−1, respectively, resulting from the perforation of TiS2 caused by the introduction of hydrogen and oxygen into the S–Ti–S framework during etching. Note that the hydroxyl and thiol groups in HOPT significantly enhance the surface polarity of TiS2, which are also favorable for adsorbing the LiPSs, suppressing the shuttle effect. More laudably, this method possesses excellent generality and can be extended to other TMDs such as CoS2 and NbS2. As reported in a follow-up study, Xiao et al. presented another extremely similar multistep approach to construct sandwich-type NbS2@S@I-doped graphene, which also brings about enhanced polarity and binding affinity for layered NbS2 to ensnare LiPSs.

Question: What's the electrolyte?
Electrochemical testing was performed in a 2032 coin-type cell using Na metal (Sigma Aldrich, USA) as the anode. Electrodes were fabricated by blending the prepared cathode powders (85 wt%), carbon black (10 wt%), and polyvinylidene fluoride (5 wt%) in N-methyl-2-pyrrolidone (Daejung Chem, Korea). The slurry was then cast on aluminum foil (Hohsen Corp., Japan) and pre-dried at 110 °C in an oven. Then, the electrode was further dried at 110 °C for 5 h in a vacuum oven, and the disks were punched out of the foil. The electrolyte solution was 0.5 M NaPF6 (Tokyo Chemical Industry, Japan) in a 1:1 volumetric mixture of ethylene carbonate (Sigma Aldrich, USA) and diethyl carbonate (Sigma Aldrich, USA) with 2 vol% fluoroethylene carbonate (Tokyo Chemical Industry, Japan). All cells were prepared in an Ar-filled glovebox (MBRAUN, Germany). The fabricated cathodes and sodium metal anodes were separated by a glass fiber (Advantec, USA) to prevent short circuiting. The loading amount of the active material for all electrodes was 3.0–4.0 mg cm−2 in the coin-type half-cell. The cells were typically tested in the constant current mode, within the voltage range of 2.0–4.3 V versus Na/Na+, where 1C = 150 mA g−1. For the full-cell test, pouch-type (3 × 5 cm) cells were fabricated and tested in the voltage range of 1.0–4.1 V at 15 mA g−1 at 25 °C. The loading amount of the active material was 9.5–10.0 mg cm−2. The anode was fabricated by blending hard carbon (provided by Aekyung Petrochemical, Korea) (80 wt%), carbon black (3 wt%), and polyvinylidene fluoride (17 wt%). The resulting slurry was covered over copper foil and dried at 110 °C for 5 h in a vacuum oven. The full cell balance was achieved by controlling the capacity ratio of anode to cathode (N/P ratio) at 1.15:1.

Question: What's the cathode?
Electrochemical testing was performed in a 2032 coin-type cell using Na metal (Sigma Aldrich, USA) as the anode. Electrodes were fabricated by blending the prepared cathode powders (85 wt%), carbon black (10 wt%), and polyvinylidene fluoride (5 wt%) in N-methyl-2-pyrrolidone (Daejung Chem, Korea). The slurry was then cast on aluminum foil (Hohsen Corp., Japan) and pre-dried at 110 °C in an oven. Then, the electrode was further dried at 110 °C for 5 h in a vacuum oven, and the disks were punched out of the foil. The electrolyte solution was 0.5 M NaPF6 (Tokyo Chemical Industry, Japan) in a 1:1 volumetric mixture of ethylene carbonate (Sigma Aldrich, USA) and diethyl carbonate (Sigma Aldrich, USA) with 2 vol% fluoroethylene carbonate (Tokyo Chemical Industry, Japan). All cells were prepared in an Ar-filled glovebox (MBRAUN, Germany). The fabricated cathodes and sodium metal anodes were separated by a glass fiber (Advantec, USA) to prevent short circuiting. The loading amount of the active material for all electrodes was 3.0–4.0 mg cm−2 in the coin-type half-cell. The cells were typically tested in the constant current mode, within the voltage range of 2.0–4.3 V versus Na/Na+, where 1C = 150 mA g−1. For the full-cell test, pouch-type (3 × 5 cm) cells were fabricated and tested in the voltage range of 1.0–4.1 V at 15 mA g−1 at 25 °C. The loading amount of the active material was 9.5–10.0 mg cm−2. The anode was fabricated by blending hard carbon (provided by Aekyung Petrochemical, Korea) (80 wt%), carbon black (3 wt%), and polyvinylidene fluoride (17 wt%). The resulting slurry was covered over copper foil and dried at 110 °C for 5 h in a vacuum oven. The full cell balance was achieved by controlling the capacity ratio of anode to cathode (N/P ratio) at 1.15:1.

Question: What's the anode?
Answer: Na metal
Electrochemical testing was performed in a 2032 coin-type cell using Na metal (Sigma Aldrich, USA) as the anode. Electrodes were fabricated by blending the prepared cathode powders (85 wt%), carbon black (10 wt%), and polyvinylidene fluoride (5 wt%) in N-methyl-2-pyrrolidone (Daejung Chem, Korea). The slurry was then cast on aluminum foil (Hohsen Corp., Japan) and pre-dried at 110 °C in an oven. Then, the electrode was further dried at 110 °C for 5 h in a vacuum oven, and the disks were punched out of the foil. The electrolyte solution was 0.5 M NaPF6 (Tokyo Chemical Industry, Japan) in a 1:1 volumetric mixture of ethylene carbonate (Sigma Aldrich, USA) and diethyl carbonate (Sigma Aldrich, USA) with 2 vol% fluoroethylene carbonate (Tokyo Chemical Industry, Japan). All cells were prepared in an Ar-filled glovebox (MBRAUN, Germany). The fabricated cathodes and sodium metal anodes were separated by a glass fiber (Advantec, USA) to prevent short circuiting. The loading amount of the active material for all electrodes was 3.0–4.0 mg cm−2 in the coin-type half-cell. The cells were typically tested in the constant current mode, within the voltage range of 2.0–4.3 V versus Na/Na+, where 1C = 150 mA g−1. For the full-cell test, pouch-type (3 × 5 cm) cells were fabricated and tested in the voltage range of 1.0–4.1 V at 15 mA g−1 at 25 °C. The loading amount of the active material was 9.5–10.0 mg cm−2. The anode was fabricated by blending hard carbon (provided by Aekyung Petrochemical, Korea) (80 wt%), carbon black (3 wt%), and polyvinylidene fluoride (17 wt%). The resulting slurry was covered over copper foil and dried at 110 °C for 5 h in a vacuum oven. The full cell balance was achieved by controlling the capacity ratio of anode to cathode (N/P ratio) at 1.15:1.

Question: What's the electrolyte?
Answer: 0.5 M NaPF6
Though oxygen anion redox processes remarkably boost the specific capacity of LLOs, they trigger some intractable issues, such as voltage/capacity fade, voltage hysteresis, low initial Coulombic efficiency, and inferior rate capability. It has been demonstrated that the voltage hysteresis is caused by the poor kinetics of anionic redox reactions and grows progressively with overoxidation of lattice oxygen anions. Continuous side reactions between overoxidized oxygen anions and organic electrolytes give rise to a thick cathode electrolyte interphase (CEI) film, which deteriorates the interfacial charge-transfer kinetics. Besides, the oxygen anion redox reactions greatly affect the stability of the cationic redox chemistry of these 3d-TM LLOs. Namely, the oxidation of oxygen anions is usually accompanied by irreversible TM migration into neighboring Li 3a vacancies, resulting in structural transformation from the layered to spinel and/or rock-salt phases, which further leads to capacity/voltage fade. Strategies for mitigation of these issues have focused on surface coating, inactive-ion doping, a composition-graded structure, and optimization of chemical composition. In particular, regulating the anionic redox behaviors by tuning the cation arrangement and oxygen stacking sequence has captured great attention recently. Although some intriguing progress has been made, it is a long way towards their real-world implementation in high energy-density LIBs.

Question: What's the electrolyte?
For further confirmation of the above electrochemical reaction mechanism, the HRTEM images of the discharged/charged electrodes were recorded. The ex situ images (ESI Fig. S8†) clearly showed the presence of the lattice fringes related to the β-MnS phase, thereby confirming the mechanism proposed in the present study. From these results, it is evident that such reaction mechanisms demonstrate electrochemical stability for prolonged cycling of the proposed composite electrode. The early variation in the specific capacity of the present electrode during cycling (Fig. 4c) is mostly related to the gradual activation of nanostructured electrodes. However, it remains essential to identify the individual contribution of the two reactions (intercalation and conversion) in the present electrochemical regulation to explain the variation in the long-term cycling curve (Fig. 4c) of the present α-MnS@NS-C electrode. To achieve this, further studies mostly related to in situ characterizations including the galvanostatic intermittent titration technique (GITT) and potentiostatic electrochemical impedance spectroscopy (PEIS) combined with separate examinations of the voltage profiles over regular cycling spans are required. However, the high reversibility of the present intercalation-cum-conversion reaction mechanism is actively supported by the conductive carbon network formed from the co-doping of the N and S in graphitic carbon. The unique electrode morphology and carbon matrix can improve electrical connectivity. Moreover, they impart structural stability by accommodating the volume changes caused by structural transitions and prevent polysulfide dissolution into the electrolyte during consecutive lithiation/delithiation processes. This, in turn, can enhance the electrochemical performance and cyclability of the proposed composite electrode.

Question: What's the electrolyte?
In addition to the room-temperature performance investigation, we also explored the possibility of operating the hybrid supercapacitor at low temperatures. Our previous research studies have demonstrated that rechargeable batteries using H3O+ ions as charge carriers can operate even at a low temperature of −70 °C. Therefore, it is highly possible that this hybrid supercapacitor can operate well in such cold environments. To illustrate this assumption, we evaluated its electrochemical performance at a low temperature of −70 °C. It can be observed from Fig. S19† that the acid electrolyte containing Mn2+ has frozen at −70 °C. However, the hybrid supercapacitor still displays a discharge specific capacitance of 163.6 F g−1 at 0.1 A g−1 and 62.2 F g−1 at 0.5 A g−1 (Fig. 5a). Additionally, the Ragone plot in Fig. 5b shows that the hybrid supercapacitor exhibits a maximum energy density of 27.4 W h kg−1 and power density of 605 W kg−1 at −70 °C. More surprisingly, the specific capacitance of the hybrid supercapacitor can maintain approximately 100% of the original capacitance over 1000 cycles at −70 °C (Fig. 5c). Such excellent low-temperature performance of the hybrid supercapacitor is associated with the high ionic conductivity of the electrolyte. The DSC measurements show that the freezing point of the acid electrolyte containing Mn2+ is −40.2 °C (Fig. S20†), which is lower than that of the 2 M MnSO4 solution (−11 °C, Fig. S21†). Surprisingly, it is found that this acid electrolyte containing Mn2+ can still show a decent ionic conductivity at −70 °C (2.6 mS cm−1), obtained from EIS data displayed in Fig. S22 (see the related calculations in the ESI†).

Question: What's the electrolyte?
Herein, a Li/LiV2(PO4)3 primary battery was proposed and studied for the first time. The unique NASICON structure of monoclinic LiV2(PO4)3 facilitated Li+ diffusion, ensuring superior rate capability and low-temperature performance of the battery. However, the short shelf life of the Li/LiV2(PO4)3 primary batteries hinders their practical applications. The shelf life of the Li/LiV2(PO4)3 primary batteries was improved by optimizing the electrolyte composition. It was found that the corrosion of the Al foil triggered by the organic radical cations generated from the electrochemical oxidation of EC at high potentials leads to the self-discharge of the Li/LiV2(PO4)3 primary battery. When EC was replaced by PC, the corrosion of the Al foil was alleviated, and the shelf life of the Li/LiV2(PO4)3 primary battery was significantly improved. However, the loss of capacity still occurred after storage, which is ascribed to the oxidation decomposition of the electrolyte on the surface of the LiV2(PO4)3 cathode. A slow two-phase transition process from the LiV2(PO4)3 phase to the Li3V2(PO4)3 phase with the reduction of V4+ to low-valence V was characterized by the in situ XRD of the LiV2(PO4)3 cathode during its storage; this process was accompanied by the spontaneous insertion of Li back into LiV2(PO4)3. It was found that LiBOB as an additive effectively helps to improve the shelf life of the Li/LiV2(PO4)3 primary battery by alleviating the side reaction between LiV2(PO4)3 and electrolyte according to the XPS results, 100% of capacity could be maintained after one-month storage. Meanwhile, the Li/LiV2(PO4)3 primary battery exhibited superior rate capability and low-temperature performance: 86% energy could be maintained at 50C and 63% energy could be maintained at −40 °C and 0.1C, which was substantially better than the performance of the Li/MnO2 primary battery. Thus, our Li/LiV2(PO4)3 primary battery is an ideal candidate for applications in extreme situations.

Question: What's the cathode?
Answer:  LiV2(PO4)3
Herein, a Li/LiV2(PO4)3 primary battery was proposed and studied for the first time. The unique NASICON structure of monoclinic LiV2(PO4)3 facilitated Li+ diffusion, ensuring superior rate capability and low-temperature performance of the battery. However, the short shelf life of the Li/LiV2(PO4)3 primary batteries hinders their practical applications. The shelf life of the Li/LiV2(PO4)3 primary batteries was improved by optimizing the electrolyte composition. It was found that the corrosion of the Al foil triggered by the organic radical cations generated from the electrochemical oxidation of EC at high potentials leads to the self-discharge of the Li/LiV2(PO4)3 primary battery. When EC was replaced by PC, the corrosion of the Al foil was alleviated, and the shelf life of the Li/LiV2(PO4)3 primary battery was significantly improved. However, the loss of capacity still occurred after storage, which is ascribed to the oxidation decomposition of the electrolyte on the surface of the LiV2(PO4)3 cathode. A slow two-phase transition process from the LiV2(PO4)3 phase to the Li3V2(PO4)3 phase with the reduction of V4+ to low-valence V was characterized by the in situ XRD of the LiV2(PO4)3 cathode during its storage; this process was accompanied by the spontaneous insertion of Li back into LiV2(PO4)3. It was found that LiBOB as an additive effectively helps to improve the shelf life of the Li/LiV2(PO4)3 primary battery by alleviating the side reaction between LiV2(PO4)3 and electrolyte according to the XPS results, 100% of capacity could be maintained after one-month storage. Meanwhile, the Li/LiV2(PO4)3 primary battery exhibited superior rate capability and low-temperature performance: 86% energy could be maintained at 50C and 63% energy could be maintained at −40 °C and 0.1C, which was substantially better than the performance of the Li/MnO2 primary battery. Thus, our Li/LiV2(PO4)3 primary battery is an ideal candidate for applications in extreme situations.

Question: What's the electrolyte?