milerssliu/battery-device-data-qa huggingface dataset:
In this work, we developed lithium-ion cathodes based on 3D-interconnected Ni nanowire current collectors and a lithiated manganese oxide active material, which combine high volumetric capacity and good rate performance. The 3D-nanowire current collector exhibits high porosity and a very high surface-to-volume ratio. Consequently, upon conformally coating it with the active material, the energy-storing component is distributed over a few nanometer-thick layer. Since the Ni nanowire network provides access of electrons to the entire volume of the active material and the ionic transport in the thin active layer is unimpeded, the cathode reached very high utilization of the active material, which is typically inaccessible in bulk cathodes. As a result, the electrode exhibits a high rechargeable volumetric capacity of about 200 mA h cm−3, which is more than the capacity of most 3D-nanostructured cathodes reported in the literature. Additionally, thanks to the combination of the small thickness of the active material and its high contact area with the current collector and electrolyte, the cathode can deliver significantly high capacity during high rate charging and discharging, demonstrating its potential for use in high volumetric capacity and fast charging Li-ion batteries.

Question: What's the cathode?
LLZO pellets were sputter-coated (LEICA EM ACE600) with Au on both sides to form contacts that acted as Li ion quasi-blocking electrodes. In order to fabricate Li symmetric cells, LLZO pellets were sandwiched between two Li metal discs (Sigma Aldrich) either with or without interposition of IL interlayers. 5 μL of the gel electrolytes were introduced at each interface. Cells without the interlayer were heated till 180 °C (melting temperature of Li) to promote Li–SE mutual contact. Both Au|LLZO|Au and Li|LLZO|Li were assembled in Swagelok©-type cell holders. Electrochemical impedance spectroscopy (EIS) was performed using an electrochemical workstation (ZAHNER-Elektrik GmbH) with an applied sinusoidal excitation voltage of 10 mV in the frequency range from 5 MHz to 0.01 Hz. EIS data were fitted with ZView software. A Bio-Logic VMP-3 potentiostat was used to conduct the Li stripping and plating tests at current densities ranging from 0.05 to 0.4 mA cm−2. The cathode slurry was prepared by mixing S/NC powders (90 wt%) and the PVDF binder (10 wt%, Kynar) by magnetic stirring using NMP as solvent. The obtained slurry was cast onto aluminum foil by doctor blade techniques and thereafter dried at 60 °C for 24 h. The sulfur loading at the electrode was ∼0.5 mgsulfur cm−2. The electrochemical performance of the full cells was tested by galvanostatic cycling with 0.1C (1C = 1672 mA gsulfur−1) in the voltage range between 3 and 1.5 V, using an Arbin BT-2000 battery tester at room temperature. The preparation of the cells and all electrochemical tests were performed in an argon-filled glove-box.

Question: What's the cathode?
For more than a decade, researchers have known that layered oxide cathodes, particularly NMC and NCA materials, have fragile surfaces. Thus, it allows various chemical/electrochemical reactions with gases (e.g., storing environments) or liquids (e.g., organic electrolytes) at the surfaces. As the urgent demand for commercialization of the Co-free, Ni-rich layered cathodes, the shelf life of active powders is considered as an important characteristic due to the uncertain delay from powder production to electrode processing and to battery manufacturing. In addition, with the nickel concentration approaching 100%, and the pursuit towards Co-free materials, surface stability against the organic electrolyte is vital in the commercialization. LiNiO2-based materials are more unstable than their cobalt-containing analogs because of the increased magnetic frustration of Ni3+ than Co3+. Therefore, surface degradation is more severe in Ni-rich oxide cathodes due to the high oxidation state of nickel. We previously discovered that the electrochemical performance of LiNiO2 cathode can be improved by incorporating dual dopants through the surface and bulk properties enhancement. Herein, we exploit the platform of LiNiO2-based materials to study the surface fragility under various practical conditions. Moreover, we will further discuss advantages of doping chemistry through the post-mortem characterizations. Lastly, we are aiming to provide insights into developing low-cost, high-energy Co-free Ni-rich cathode materials.

Question: What's the cathode?
Answer: LiNiO2
For more than a decade, researchers have known that layered oxide cathodes, particularly NMC and NCA materials, have fragile surfaces. Thus, it allows various chemical/electrochemical reactions with gases (e.g., storing environments) or liquids (e.g., organic electrolytes) at the surfaces. As the urgent demand for commercialization of the Co-free, Ni-rich layered cathodes, the shelf life of active powders is considered as an important characteristic due to the uncertain delay from powder production to electrode processing and to battery manufacturing. In addition, with the nickel concentration approaching 100%, and the pursuit towards Co-free materials, surface stability against the organic electrolyte is vital in the commercialization. LiNiO2-based materials are more unstable than their cobalt-containing analogs because of the increased magnetic frustration of Ni3+ than Co3+. Therefore, surface degradation is more severe in Ni-rich oxide cathodes due to the high oxidation state of nickel. We previously discovered that the electrochemical performance of LiNiO2 cathode can be improved by incorporating dual dopants through the surface and bulk properties enhancement. Herein, we exploit the platform of LiNiO2-based materials to study the surface fragility under various practical conditions. Moreover, we will further discuss advantages of doping chemistry through the post-mortem characterizations. Lastly, we are aiming to provide insights into developing low-cost, high-energy Co-free Ni-rich cathode materials.

Question: What's the cathode?
Answer: Ni-rich oxide
Although decomposition is unavoidable, lithium residuals do not negatively impact capacity decay, resulting in similar capacity retentions of 73.7%, 70.1%, and 68.7% for the samples aged in the Ar glovebox, in the dry box, and in the fresh state, respectively (Fig. 2b). According to many studies, surface contaminants increase the ion diffusion energy barrier and promote increased amounts of gas generation (i.e. CO2), which ultimately contributes to battery volume expansion. Degassing process after formation cycles is commonly adopted before the battery sealing, which adds to the battery cost. Thus, washing cathode powders using water, alcohol, or other solvents, or a simple high temperature annealing under oxygen flow can be utilized to remove the lithium residues. We also noticed that upon extensive storage (three months in the dry box), the large amount of carbonates can be visible in the SEM (scanning electron microscopy) images, which would more negatively impact the battery performance (Fig. S3†). Given that these materials are sensitive to storage environment and duration, it is recommended that scientific publications should specify these details when the performance is reported.

Question: What's the cathode?
The electrode pastes were composed of active materials/carbon black/gel electrolyte precursor whose composition ratios were 60/8.5/31.5 (w/w/w) for the LiCoO2 (LCO) cathode and 52/7.5/40.5 (w/w/w) for the Li4Ti5O12 (LTO) anode, respectively. The gel polymer electrolyte precursor was prepared by mixing a UV-curable ethoxylated trimethylolpropane tri-acrylate (ETPTA) monomer (Aldrich) (including 1.0 wt% 2-hydroxy-2-methl-1-phenyl-1-1propanone (HMPP) as a photo-initiator) and high boiling point electrolyte (1 M LiPF6 in ethylene carbonate(EC)/propylene carbonate(PC) 1/1 (v/v)) in a composition ratio of 15/85 (w/w). To fabricate the bQSSB with cSiPV, the LTO anode paste was directly stencil-printed onto an Al current collector of the cSiPV module without any processing solvents and then exposed to UV irradiation. UV irradiation was performed using an Hg UV-lamp (Lichtzen) with an irradiation peak intensity of approximately 1260 mW cm−2. Subsequently, on the LTO anode (thickness = 50 μm and mass loading = 5.9 mg cm−2), a composite polymer electrolyte (CPE, gel electrolyte precursor/Al2O3 nanoparticles (average particle size ∼300 nm) = 56/44 (w/w)) was introduced through the UV curing-assisted printing process. Then, the LCO cathode paste was stencil-printed directly on the CPE/LTO anode and solidified by UV irradiation, yielding the printed LCO cathode (thickness = 30 μm and mass loading = 6.2 mg cm−2). After placing an Al current collector on top of the printed LCO cathode/printed CPE/printed LTO anode, the QSSB unit cell was obtained. Another QSSB unit cell was introduced, using the same printing process, on the top of the pre-fabricated QSSB unit cell, leading to the bQSSB with a bipolar structure. The number of QSSB unit cells on the cSiPV module was determined from the Vmax of the module concerning the voltage matching between the cSiPV and the bQSSB. Finally, the encapsulation of the bQSSB was conducted with Al pouch packaging substances and a UV-curable hydrophobic polymer (PRO-001, Novacentrix). All assembly steps of the cells were performed in a dry room.

Question: What's the cathode?
Answer:  LiCoO2 (LCO)
The electrode pastes were composed of active materials/carbon black/gel electrolyte precursor whose composition ratios were 60/8.5/31.5 (w/w/w) for the LiCoO2 (LCO) cathode and 52/7.5/40.5 (w/w/w) for the Li4Ti5O12 (LTO) anode, respectively. The gel polymer electrolyte precursor was prepared by mixing a UV-curable ethoxylated trimethylolpropane tri-acrylate (ETPTA) monomer (Aldrich) (including 1.0 wt% 2-hydroxy-2-methl-1-phenyl-1-1propanone (HMPP) as a photo-initiator) and high boiling point electrolyte (1 M LiPF6 in ethylene carbonate(EC)/propylene carbonate(PC) 1/1 (v/v)) in a composition ratio of 15/85 (w/w). To fabricate the bQSSB with cSiPV, the LTO anode paste was directly stencil-printed onto an Al current collector of the cSiPV module without any processing solvents and then exposed to UV irradiation. UV irradiation was performed using an Hg UV-lamp (Lichtzen) with an irradiation peak intensity of approximately 1260 mW cm−2. Subsequently, on the LTO anode (thickness = 50 μm and mass loading = 5.9 mg cm−2), a composite polymer electrolyte (CPE, gel electrolyte precursor/Al2O3 nanoparticles (average particle size ∼300 nm) = 56/44 (w/w)) was introduced through the UV curing-assisted printing process. Then, the LCO cathode paste was stencil-printed directly on the CPE/LTO anode and solidified by UV irradiation, yielding the printed LCO cathode (thickness = 30 μm and mass loading = 6.2 mg cm−2). After placing an Al current collector on top of the printed LCO cathode/printed CPE/printed LTO anode, the QSSB unit cell was obtained. Another QSSB unit cell was introduced, using the same printing process, on the top of the pre-fabricated QSSB unit cell, leading to the bQSSB with a bipolar structure. The number of QSSB unit cells on the cSiPV module was determined from the Vmax of the module concerning the voltage matching between the cSiPV and the bQSSB. Finally, the encapsulation of the bQSSB was conducted with Al pouch packaging substances and a UV-curable hydrophobic polymer (PRO-001, Novacentrix). All assembly steps of the cells were performed in a dry room.

Question: What's the cathode?
Answer: LCO
In comparison with well-protected rigid batteries with liquid electrolytes, solid-state batteries (ssBs) are more beneficial, offering high flexibility, high wearability and leakage prevention. Currently, ssBs with the capability of bending and twisting have been extensively studied. However, it remains a challenge to develop a highly stretchable ssB with the maintenance of high performance. Herein, we report a stable solid-state zinc ion battery (ssZIB) based on a cellulose nanofiber (CNF)–polyacrylamide (PAM) hydrogel electrolyte and a Mg0.23V2O5·1.0H2O cathode. The designed CNF–PAM hydrogel shows high stretchability and robust mechanical stability. Moreover, the porous CNF–PAM hydrogel electrolyte provides efficient pathways for the transportation of zinc ions. And the robust layered structure of V2O5·1.0H2O pillared with Mg2+ ions and water supports the fast insertion/extraction of zinc ions in the lattice. Therefore, the designed ssZIB shows unprecedented high capacity at high current with durable cycling life. At a current density of 5 A g−1 (charging time of around 3 minutes), the ssZIBs can deliver a high reversible capacity of 216 mA h g−1 after 2000 cycles and retain 98.6% of the initial capacity, showing a high capacity and long-life durability at high currents. Furthermore, the designed spring ssZIBs can work under stretching with the strain reaching 650%. And the designed ssZIBs are still operational even under repeated bending, freezing, and heating conditions. The ssZIBs show robust mechanical stability, high stretchability and impressive electrochemical performance, providing a potential pathway to expand the application of ZIBs to a broad range of practical energy storage devices.

Question: What's the cathode?
Answer: Mg0.23V2O5·1.0H2O
To investigate the electrochemical Na ion storage mechanism to predict the theoretical properties of Nax[Ni0.5Mn0.5]O2, we performed first-principles calculations based on the structural information verified through the Rietveld refinement analysis. At this stage, even though 0.01 mol of Ca2+ ions was incorporated into the bulk Na sites, Na0.98Ca0.01[Ni0.5Mn0.5]O2 showed a nearly identical crystal structure with Na[Ni0.5Mn0.5]O2; hence, we assumed that Na0.98Ca0.01[Ni0.5Mn0.5]O2 experienced the same O3–P3 phase transformation during the Na+ extraction/insertion process. Various Na/vacancy configurations on O3-Nax[Ni0.5Mn0.5]O2 compositions (0 ≤ x ≤ 1) were generated through the cluster assisted statistical mechanics (CASM) code and then, we predicted the theoretical formation energies of the O3-Nax[Ni0.5Mn0.5]O2 composition. Based on information of the formation energies, we calculated the redox potentials of O3-Nax[Ni0.5Mn0.5]O2 during Na+ extraction/insertion using the following equation where E(x) indicates the formation energy on the most stable Na/vacancy configuration of x species. By considering the typical O3–P3 phase transition in the O3-type layered oxide cathode in SIBs, we calculated the formation energies of P3-Nax[Ni0.5Mn0.5]O2 and then applied this information to compare the thermodynamic stability between O3- and P3-phases. As presented in Fig. 4a, we predicted that the O3–P3 phase transition occurred after extraction of 0.25 mol of Na ions from O3-Na1[Ni0.5Mn0.5]O2, and then, when the Na content in P3-Nax[Ni0.5Mn0.5]O2 was reduced to less than 0.25 mol, the O3–P3 phase transition re-occurred. Moreover, we verified that in the case of O3-/P3-Nax[Ni0.5Mn0.5]O2, the redox potentials required for Na+ extraction/insertion were less than ∼4.11 V (vs. Na+/Na) and more than ∼2.48 V, which indicates that 1 mol of Na ions can be reversibly extracted/inserted from/into the O3-Na1[Ni0.5Mn0.5]O2 structure despite the O3–P3 phase transition. Fig. 4b illustrates the predicted redox potential range of the O3/P3-Nax[Ni0.5Mn0.5]O2 cathode as a function of the Na content (0 ≤ x ≤ 1) with experimentally measured galvanostatic intermittent titration technique (GITT) profiles in the voltage range of 2.0–4.3 V. To confirm our hypothesis that the Ca-substituted cathode would undergo a similar O3–P3 phase transformation during the sodiation/de-sodiation process, we checked the GITT profiles of the Na0.98Ca0.01[Ni0.5Mn0.5]O2 cathode and overlaid the results with the predicted theoretical redox potential of the Nax[Ni0.5Mn0.5]O2 cathode. Interestingly, we confirmed that the slope of the charge/discharge curve of O3-Na0.98Ca0.01[Ni0.5Mn0.5]O2 matched the predicted redox potential of the Nax[Ni0.5Mn0.5]O2 cathode well within the wide voltage window of 2.0–4.3 V; this clearly verified our hypothesis and confirmed that ∼1.0 mol of Na+ ions could be extracted/inserted from/into Na0.98Ca0.01[Ni0.5Mn0.5]O2.

Question: What's the cathode?
Answer: O3-type layered oxide
To investigate the electrochemical Na ion storage mechanism to predict the theoretical properties of Nax[Ni0.5Mn0.5]O2, we performed first-principles calculations based on the structural information verified through the Rietveld refinement analysis. At this stage, even though 0.01 mol of Ca2+ ions was incorporated into the bulk Na sites, Na0.98Ca0.01[Ni0.5Mn0.5]O2 showed a nearly identical crystal structure with Na[Ni0.5Mn0.5]O2; hence, we assumed that Na0.98Ca0.01[Ni0.5Mn0.5]O2 experienced the same O3–P3 phase transformation during the Na+ extraction/insertion process. Various Na/vacancy configurations on O3-Nax[Ni0.5Mn0.5]O2 compositions (0 ≤ x ≤ 1) were generated through the cluster assisted statistical mechanics (CASM) code and then, we predicted the theoretical formation energies of the O3-Nax[Ni0.5Mn0.5]O2 composition. Based on information of the formation energies, we calculated the redox potentials of O3-Nax[Ni0.5Mn0.5]O2 during Na+ extraction/insertion using the following equation where E(x) indicates the formation energy on the most stable Na/vacancy configuration of x species. By considering the typical O3–P3 phase transition in the O3-type layered oxide cathode in SIBs, we calculated the formation energies of P3-Nax[Ni0.5Mn0.5]O2 and then applied this information to compare the thermodynamic stability between O3- and P3-phases. As presented in Fig. 4a, we predicted that the O3–P3 phase transition occurred after extraction of 0.25 mol of Na ions from O3-Na1[Ni0.5Mn0.5]O2, and then, when the Na content in P3-Nax[Ni0.5Mn0.5]O2 was reduced to less than 0.25 mol, the O3–P3 phase transition re-occurred. Moreover, we verified that in the case of O3-/P3-Nax[Ni0.5Mn0.5]O2, the redox potentials required for Na+ extraction/insertion were less than ∼4.11 V (vs. Na+/Na) and more than ∼2.48 V, which indicates that 1 mol of Na ions can be reversibly extracted/inserted from/into the O3-Na1[Ni0.5Mn0.5]O2 structure despite the O3–P3 phase transition. Fig. 4b illustrates the predicted redox potential range of the O3/P3-Nax[Ni0.5Mn0.5]O2 cathode as a function of the Na content (0 ≤ x ≤ 1) with experimentally measured galvanostatic intermittent titration technique (GITT) profiles in the voltage range of 2.0–4.3 V. To confirm our hypothesis that the Ca-substituted cathode would undergo a similar O3–P3 phase transformation during the sodiation/de-sodiation process, we checked the GITT profiles of the Na0.98Ca0.01[Ni0.5Mn0.5]O2 cathode and overlaid the results with the predicted theoretical redox potential of the Nax[Ni0.5Mn0.5]O2 cathode. Interestingly, we confirmed that the slope of the charge/discharge curve of O3-Na0.98Ca0.01[Ni0.5Mn0.5]O2 matched the predicted redox potential of the Nax[Ni0.5Mn0.5]O2 cathode well within the wide voltage window of 2.0–4.3 V; this clearly verified our hypothesis and confirmed that ∼1.0 mol of Na+ ions could be extracted/inserted from/into Na0.98Ca0.01[Ni0.5Mn0.5]O2.

Question: What's the cathode?
Answer: O3/P3-Nax[Ni0.5Mn0.5]O2
Another critical property of an electrode material toward practical application is the ease of handling against a moist environment. Most of the O3-type transition metal oxide cathodes reported so far are moisture sensitive because of the low redox potential associated with 3d-metals. Once the cathode is exposed to air or moisture, water oxidizes the transition metal ions with the concomitant removal of Na+ ions, which further react with CO2 and H2O in air to form Na2CO3 or NaOH. Such undesirable reactions usually cause structural degradation and poor electrochemical performances and thus make them difficult to handle. As revealed in Fig. 7, after exposure to air with a relative humidity of ≈55%, the Na[Ni0.5Mn0.5]O2 exhibited an apparent structural change to a Na-deficient monoclinic O′3 phase together with formation of Na2CO3·nH2O on the surface. In contrast, Na0.98Ca0.01[Ni0.5Mn0.5]O2 remarkably retarded spontaneous phase transition and retained the original O3 structure. To confirm in detail the structural stability against a humid atmosphere, a comparative study of the XRD evolution of the Na0.98Ca0.01[Ni0.5Mn0.5]O2 and Na[Ni0.5Mn0.5]O2 cathodes was conducted as a function of exposure time (1, 3, and 5 days and 1 week) (Fig. S16†). After 1 day, there were no significant structural changes in either cathode. However, after three days, the Na[Ni0.5Mn0.5]O2 cathode was readily oxidized in the presence of moisture, and subsequently, the intensity of (003)hex. and (104)hex. peaks decreased in the XRD patterns. After 5 days, splitting of the (003)hex. and (006)hex. diffraction lines was observed, indicating a slightly enlarged interslab distance for the new monoclinic O3 phase. Finally, after 1 week, the phase transformation from the hexagonal O3 to the monoclinic O′3 phase occurred in the Na[Ni0.5Mn0.5]O2 cathode. This monoclinic O′3 phase transformation can be observed in the sodium deficient structure when the sodium ions are extracted down to 20 mol% in the original O3 structure. In contrast, throughout the week, the intensified peaks, (003)hex., (006)hex., (101)hex., (102)hex., and (104)hex., in the O3 phase were well retained persistently for the Na0.98Ca0.01[Ni0.5Mn0.5]O2 cathode, indicating less reactivity against moisture. These results suggest that the Ca2+ ions on the Na sites with strong Ca–O bonding prevent the removal of Na+ ions from the structure when exposed to air. As expected, in Fig. S17,† the Na0.98Ca0.01[Ni0.5Mn0.5]O2 cathode demonstrated higher reversible capacity with lower voltage polarization and better cycling stability after prolonged exposure, while the Na[Ni0.5Mn0.5]O2 cathode showed poor electrochemical performance and even exhibited an irreversible reaction during charging, due to the decomposition of Na2CO3 which is a by-product of removed Na+ ions and CO2 in air. Such a comparison of the thermal properties and air-stability strengthens the merits of Ca-substituted cathodes in practical application.

Question: What's the cathode?
Answer: Na0.98Ca0.01[Ni0.5Mn0.5]O2 and Na[Ni0.5Mn0.5]O2