milerssliu/battery-device-data-qa huggingface dataset:
To test the cyclability of columnar lithium metal during cell operation, operando GISAXS was used to probe the morphology of lithium metal deposits during cycling. GISAXS, being sensitive to length scales on the order of a few to a few hundred nanometers, exhibits a distinct set of evenly spaced intensity oscillations in the qy direction (Fig. 12) arising from the highly monodispersed columnar microstructure, with column diameters of ∼100–200 nm depending on current density (Fig. S8†); the periodicity Δqy of these oscillations is related to the column diameter d by Δqy = 2π/d. Oscillations in the qz direction arise from interference between X-rays scattered from the lithium–electrolyte and lithium–copper interfaces, complicated by multiple scattering and indicate the top surface of the film is very smooth. At the end of plating 1 mA h cm−2 of lithium, strong intensity oscillations are apparent in the qy direction, indicative of a columnar morphology (Fig. 12c). After stripping half of the plated capacity (0.5 mA h cm−2), the intensity oscillations are still present, though broader and less pronounced, indicating the columnar morphology is maintained but is less monodisperse in size and shape (Fig. 12d). At the end of the second plating half cycle the oscillations are even less pronounced (Fig. 12e), suggesting that cycling a large percentage of the plated 1 mA h cm−2 capacity, in this case 50%, with a columnar morphology leads to a loss of uniformity in the microstructure. This is further evidenced by the fact that if all the columnar lithium is stripped to a 1 V vs. Li/Li+ cutoff voltage, the second plating half cycle does not produce a columnar morphology (Fig. S9†). This is consistent with the report from Zhang et al. which demonstrated using ex situ SEM that lithium is stripped from both the tops and sides of lithium nanorods, enabled by the high lithium-ion diffusivity of the SEI, disrupting uniform re-plating onto the high aspect ratio columns. This limits the cycle life of practical batteries which must uniformly plate and strip high capacities of lithium during each charge/discharge cycle, particularly in “anode-free” configurations. Thus, further understanding the impact of additional conditions, including electrochemical profile and mechanical compression (stack pressure), which could help promote the growth of columns with a lower aspect ratio (disc-like rather than rod-like), will be crucial to maintaining morphology control after hundreds of cycles and enhancing the long term cyclability of lithium metal batteries. The effects of compression, the presence of a separator, and lower volume of electrolyte, in particular, require additional investigation as the behavior observed using the flooded open cell design employed in this study may not be directly transferable to a commercial-type battery.

Question: What's the electrolyte?
To investigate the electrochemical reaction mechanism of Zn2+ in the NV NSs@ACC//Zn battery, ex situ XRD and XPS analyses are carried out. Fig. 5a shows the different charge/discharge states during the 2nd cycle at 0.1 A g−1. During the discharge process, it can be observed that a small amount of (NH4)2V10O25·8H2O transforms to the new phase of Zn3(OH)2V2O7·2H2O (JCPDS no. 50-0570) (Fig. 5b), which could be attributed to H+/Zn2+-co-insertion into the VO layers. The peaks between the range of 10–35° for the samples cha.0.8 V and cha.1.4 V were more obvious than that for the discharge process. This is attributed to the XRD pattern of Zn(OH)2 impurity, which could arise from the deposited Zn(OH)2@glass fiber adhered on the surface of the sample. In addition, as can be seen in Fig. 5c, the peak for the (001) plane evidently shifts to a lower degree from 8.3 to 6.7° after immersion in the electrolyte for 1 h, corresponding to an increase in the interlayer spacing from 10.6 Å to 13.2 Å. Note that the interlayer distance during the subsequent discharge/charge process is always larger than that of the pristine sample, revealing that the expansion of the layer spacing upon immersion arose from water molecule intercalation, which can weaken the electrostatic attraction and thus facilitate the migration of multivalent Zn2+. More significantly, the diffraction peak (001) of NV NSs@ACC shifts to a lower degree during the discharge process and almost moves back to its original position during the charge process. The d-spacing of the (001) plane in different samples corresponding to the ex situ XRD patterns are presented in Table S4.† These results indicate the highly reversible Zn2+ intercalation/deintercalation of the NV host without the destruction of its open-framework during the subsequent discharge/charge process.

Question: What's the electrolyte?
The small thickness of an active material and its high contact area with the current collector and electrolyte can be simultaneously realized using 3D-structured conductive substrates. The higher surface area of a 3D-current collector can allow distributing the active material over a thinner coating (or, similarly, increasing the loading of the active material while keeping its thickness low), simultaneously maintaining open porosity for the electrolyte. Such core–shell, structurally integral electrode design can be achieved with a variety of micro- and nanostructured 3D substrates, such as micropillars, nanoporous metals, inverse metal opals or interconnected metal nanowires, which have a big advantage over macroscopic 3D foams in effective utilization of the electrode volume. Compared to nanostructured electrodes based on nanoparticles embedded in binding and conductive additives, the electrodes based on monolithic 3D structures are typically less tortious (translating to lower polarization resistance) and can be often fabricated with high spatial precision (e.g. by lithography or area-selective electrodeposition), making them particularly attractive for all-solid-state microbatteries.

Question: What's the electrolyte?
Fig. 2a shows the photographs of the PLB-CSE; the as-prepared membrane is free-standing and exhibits excellent ductility and flexibility. It is worth noting that the composite electrolyte membrane with such a high proportion of inorganic ceramic particles still exhibits great flexibility, and no cracks could be found in the electrolyte films upon bending, indicating an excellent mechanical capability. This flexible and strong PLB-CSE membrane can be used in flexible devices. To further analyze the microstructure morphologies and the distribution of LATP inorganic nanoparticles, the SEM image is presented in Fig. 2b. The SEM image shows a flat and homogeneous surface free of pores for the electrolyte membrane; the LATP ceramic fillers are uniformly dispersed in the polymer matrix. Fig. 2c displays the cross-sectional features of the PLB-CSE membrane, the thickness of which is about 60 μm, and the corresponding EDS mapping images of titanium (Ti), phosphorus (P), sulfur (S), and fluorine (F) are given in Fig. 2d–g. It can be observed that the LATP ceramic particles are uniformly dispersed in the electrolyte membrane, and the homogeneous LATP inorganic particles are in close contact with each other forming a continuous network structure, allowing Li-ion transfer between LATP ceramic grains, enabling a fast and efficient conductive pathway, which can promote ion transportation within the composite electrolyte.

Question: What's the electrolyte?
Zero-valent nonmetal engineering can also be extended to P-regulated metal nitrides and carbides. Fu et al. selected small-sized tungsten nitride (WN; ∼3 nm) as the model to investigate the function of P dopants. The experimental results confirmed that P modification could lead to significant enhancements in catalytic activity and stability for HER in acidic media, particularly with low onset overpotential of 46 mV, Tafel slope of 54 mV dec−1, large exchange current density of 0.35 mA cm−2, and long-term stability. The enhanced performance could be attributed to the interaction of P with WN, which can increase the work function. Different from the earlier reported uncontrolled P-doping strategy, Tang et al. fabricated hierarchical nanowires comprising P-doped MoC2 nanoparticles via the controlled carbonization of ternary organic–inorganic (MoOx–phytic acid–polyaniline) nanohybrids. A series of samples with different contents of P in the range of 0–3.4 wt% were successfully prepared by varying the introduced amount of polyaniline. With an increase in the P content, the XPS peaks for Mo 3d shifted to lower binding energies, signifying that the electron density of Mo2+ in MoC2 was enriched by doping P. In addition, P doping could enrich the electrons around the Fermi level in MoC2, resulting in weakened Mo–H and promoted Hads desorption in HER kinetics. Combining optimal Hads desorption energy on Mo2C and hierarchical structure, the P–Mo2C@C nanowires with controlled P doping delivered benchmark HER activity and good stability in acidic electrolytes.

Question: What's the electrolyte?
Among the many proposed applications of graphene-based materials, supercapacitors, also known as electrochemical capacitors, have been an active area of research for the past decade. Compared with secondary batteries, graphene-based supercapacitors are electrochemical energy storage devices that promise outstanding power density, charge/discharge rate, cycling stability, and operational safety. Supercapacitors are often utilized individually or in tandem with batteries for energy storage and supply (Scheme 1a(i)). They can be classified into two types: the electric double-layer capacitor (EDLC) (Scheme 1a(ii)) and the pseudocapacitor (Scheme 1a(iii)). The energy storage mechanism of the EDLC involves a simple charge separation at the interface between the conductive electrode and the electrolyte. Because there is no chemical transformation at the EDLC electrodes, the system is quite stable, although the specific capacitance is relatively low. In comparison, charge storage in a pseudocapacitor is predominantly achieved via the redox or faradic transformation of capacitive electrode materials, such as metal oxides and conductive polymers. The specific capacitance of the pseudocapacitor is generally high, but gradually decays because of structural collapse and degradation. A composite of a conductive substance and a pseudocapacitive material is desirable to enhance the overall capacitance, charge/discharge rate, and cycling lifetime. Graphene is a promising conductive component because it has a large surface area, and excellent electronic and mechanical properties. To develop a high-performance pseudocapacitor, we focused on developing a conductive polymer as an electrode counterpart to graphene. Various graphene–polymer composites with non-covalent and covalent interactions have been synthesized, and high capacitive performances have been achieved. The non-covalent interaction between graphene and polymers limits charge transfer at their interface, and hence constrains the cycling stability (Scheme 1b(i)). To address this issue, we propose the formation of the covalent bond between graphene and redox-active polymers.

Question: What's the electrolyte?
In conclusion, a new synthesis approach is presented wherein doped La2Zr2O7 pyrochlore nanocrystals are synthesized with a composition that will result in the correct stoichiometry to form Li-conducting garnets based on Li7La3Zr2O12. La and Ta co-doped pyrochlores with a La:Zr:Ta stoichiometry of 3:1.4:0.6 are demonstrated to readily form garnet-type Li6.4La3Zr1.4Ta0.6O12 between 400–550 °C in a ternary mixture of molten LiNO3–LiOH–Li2O2, with unprecedentedly low reaction temperatures. Pyrochlores can also be used as quasi-single-source precursors and blended with a Li source and reactively sintered in 2 hours at 1200 °C to form highly dense, highly conducting garnet ceramics with a microstructure similar to that obtained through advanced sintering techniques, providing a unique and successful approach to dense garnet electrolytes that can be easily extended to more advanced ceramic forming techniques such as tape-casting or additive manufacturing, potentially improving processability of garnet solid-electrolytes for solid-state lithium batteries.

Question: What's the electrolyte?
The chemical composition and structure of the SEI after 1.0 mA h cm−2 deposition at 0.2 mA cm−2, 0.5 mA cm−2 and 1.0 mA cm−2 were further probed by XPS depth profiling. The XPS depth profiles of the N 1s, Li 1s, F 1s, C 1s, and O 1s spectra are shown in Fig. 6a–i and S13–S15.† At 0.2 mA cm−2 (Fig. 6a–c), the major inorganic components comprising Li3N and LiF were distributed homogeneously in the depth direction of the SEI. Li3N, as the reduction product of LiNO3, is a well-known Li ion conductor with a conductivity of 10−3 S cm−1 at room temperature; LiF, either as an electrolyte additive or SEI component, can improve the diffusion of lithium ions at the electrode surface. The mixed Li3N and LiF layer can facilitate rapid lithium ion diffusion, stabilize the SEI and provide uniform electrodeposition. For the high current densities, especially 1.0 mA cm−2 (Fig. 6g–i), the SEI lacked the inorganic components Li3N and LiF; instead, organic ROLi species were observed. The poor ionic conductivity of ROLi impeded sufficient transport of Li ions towards the electrode surface at high current densities and induced preferential deposition. The very different SEI composition resulting from the repeated SEI breakdown and repair processes also reinforced the rupturing and re-forming cycles of the SEI. In addition, the XPS chemical composition results are in accordance with the mechanical properties obtained by AFM force probing. The SEI formed at a low current density contained a higher content of inorganic components and greater mechanical strength, while the SEI formed at a high current density contained a mixed organic–inorganic layer and was relatively soft (Fig. 6j–l).

Question: What's the electrolyte?
Polyanionic materials are a series of compounds containing polyhedral anionic structural units, which are linked to construct a three-dimensional network structure by strong covalent bonds. The unique structure endows the compounds with a stable crystal structure, moderate capacity, high operating voltage, and safety. Among them, monoclinic LiV2(PO4)3 (discharges to be Li3V2(PO4)3) is one of the most attractive cathode materials for primary batteries, which has stable voltage plateaus between 3.0 V and 4.3 V (vs. Li+/Li) and a suitable theoretical specific capacity (133 mA h g−1) corresponding to the insertion of two Li ions per formula unit. Most importantly, the unique NASICON structure of Li3V2(PO4)3 facilitates Li+ conduction and delivers faster Li+ diffusion kinetics when compared with traditional cathode materials such as LiFePO4, LiCoO2, and LiNi1/3Co1/3Mn1/3O2, ensuring superior rate capability and low-temperature performance. Thus, LiV2(PO4)3 has great potential for application as a cathode material for lithium primary batteries. For practical application, the shelf life of the Li/LiV2(PO4)3 batteries should be long enough; this means that the self-discharge rate should be as low as possible. Since the Li/LiV2(PO4)3 primary battery possesses a high open-circuit voltage (OCV) of about 4.1 V, the side reactions among electrode materials, electrolyte, and even current collectors can severely affect the shelf life of these batteries. In addition, the corrosion of the current collector leads to self-discharge. Therefore, stabilizing the interface between the electrode and electrolyte is essential.

Question: What's the cathode?
Answer: monoclinic LiV2(PO4)3 (discharges to be Li3V2(PO4)3
Polyanionic materials are a series of compounds containing polyhedral anionic structural units, which are linked to construct a three-dimensional network structure by strong covalent bonds. The unique structure endows the compounds with a stable crystal structure, moderate capacity, high operating voltage, and safety. Among them, monoclinic LiV2(PO4)3 (discharges to be Li3V2(PO4)3) is one of the most attractive cathode materials for primary batteries, which has stable voltage plateaus between 3.0 V and 4.3 V (vs. Li+/Li) and a suitable theoretical specific capacity (133 mA h g−1) corresponding to the insertion of two Li ions per formula unit. Most importantly, the unique NASICON structure of Li3V2(PO4)3 facilitates Li+ conduction and delivers faster Li+ diffusion kinetics when compared with traditional cathode materials such as LiFePO4, LiCoO2, and LiNi1/3Co1/3Mn1/3O2, ensuring superior rate capability and low-temperature performance. Thus, LiV2(PO4)3 has great potential for application as a cathode material for lithium primary batteries. For practical application, the shelf life of the Li/LiV2(PO4)3 batteries should be long enough; this means that the self-discharge rate should be as low as possible. Since the Li/LiV2(PO4)3 primary battery possesses a high open-circuit voltage (OCV) of about 4.1 V, the side reactions among electrode materials, electrolyte, and even current collectors can severely affect the shelf life of these batteries. In addition, the corrosion of the current collector leads to self-discharge. Therefore, stabilizing the interface between the electrode and electrolyte is essential.

Question: What's the electrolyte?
Polyanionic materials are a series of compounds containing polyhedral anionic structural units, which are linked to construct a three-dimensional network structure by strong covalent bonds. The unique structure endows the compounds with a stable crystal structure, moderate capacity, high operating voltage, and safety. Among them, monoclinic LiV2(PO4)3 (discharges to be Li3V2(PO4)3) is one of the most attractive cathode materials for primary batteries, which has stable voltage plateaus between 3.0 V and 4.3 V (vs. Li+/Li) and a suitable theoretical specific capacity (133 mA h g−1) corresponding to the insertion of two Li ions per formula unit. Most importantly, the unique NASICON structure of Li3V2(PO4)3 facilitates Li+ conduction and delivers faster Li+ diffusion kinetics when compared with traditional cathode materials such as LiFePO4, LiCoO2, and LiNi1/3Co1/3Mn1/3O2, ensuring superior rate capability and low-temperature performance. Thus, LiV2(PO4)3 has great potential for application as a cathode material for lithium primary batteries. For practical application, the shelf life of the Li/LiV2(PO4)3 batteries should be long enough; this means that the self-discharge rate should be as low as possible. Since the Li/LiV2(PO4)3 primary battery possesses a high open-circuit voltage (OCV) of about 4.1 V, the side reactions among electrode materials, electrolyte, and even current collectors can severely affect the shelf life of these batteries. In addition, the corrosion of the current collector leads to self-discharge. Therefore, stabilizing the interface between the electrode and electrolyte is essential.

Question: What's the cathode?
Answer: LiFePO4, LiCoO2, and LiNi1/3Co1/3Mn1/3O2
NaxTMO2 type [TM: transition metal(s)] ‘layered’ oxides, having an initial Na-content (x) of ∼1 (i.e., ‘O3’), are important as potential cathode materials for upcoming Na-ion battery systems. However, among other problems (viz., phase transformations during Na-removal/insertion, TM-dissolution etc.), such oxides suffer from severe instability against hydration in a generic sense, which in turn, negatively impacts the stability, electrochemical performances and environment/health friendliness. Against this backdrop, we have designed a composition (viz., combination of TM-/non-TM-ions) to address the aforementioned problems, in particular, air/water-instability. Partial/complete substitution of Ti-ions for Mn-ions eliminated the presence of Mn3+ (which dissolves in electrolyte) at the particle surface, suppressed the increment in impedance (as well as voltage hysteresis) during electrochemical cycling and, thus, significantly improved cyclic stability. More importantly, the air/water-stability improved drastically, such that no phase/structural change occurred even after 40 days of air-exposure and 12 h of stirring in water, unlike for predominately Mn-ion containing counterparts, which progressively evolved O′3 and P3 phases. In fact, water-stability enabled the usage of environment/health friendly, as well as less expensive, ‘aqueous-binder’ (viz., Na-alginate) and water (as solvent) for electrode preparation. The as-developed environment/health friendly ‘aqueous-processed’ electrode also exhibits excellent long-term cyclic stability, with capacity retention being ∼82% after 100 cycles (∼60% after 500 cycles and ∼56% after 750 cycles) at C/5, along with just ∼4% capacity fade over the last 250 cycles investigated (viz., cycles 500–750). Such an elimination of requirements for toxic/hazardous-cum-expensive ‘non-aqueous’ solvents/binders for electrode preparation and the associated learning, in terms of suitable combinations of TM-/non-TM-ions for these oxides in the pursuit of desired structural features, are significant steps towards the development of alkali metal-ion batteries in general.

Question: What's the cathode?
Answer: NaxTMO2
NaxTMO2 type [TM: transition metal(s)] ‘layered’ oxides, having an initial Na-content (x) of ∼1 (i.e., ‘O3’), are important as potential cathode materials for upcoming Na-ion battery systems. However, among other problems (viz., phase transformations during Na-removal/insertion, TM-dissolution etc.), such oxides suffer from severe instability against hydration in a generic sense, which in turn, negatively impacts the stability, electrochemical performances and environment/health friendliness. Against this backdrop, we have designed a composition (viz., combination of TM-/non-TM-ions) to address the aforementioned problems, in particular, air/water-instability. Partial/complete substitution of Ti-ions for Mn-ions eliminated the presence of Mn3+ (which dissolves in electrolyte) at the particle surface, suppressed the increment in impedance (as well as voltage hysteresis) during electrochemical cycling and, thus, significantly improved cyclic stability. More importantly, the air/water-stability improved drastically, such that no phase/structural change occurred even after 40 days of air-exposure and 12 h of stirring in water, unlike for predominately Mn-ion containing counterparts, which progressively evolved O′3 and P3 phases. In fact, water-stability enabled the usage of environment/health friendly, as well as less expensive, ‘aqueous-binder’ (viz., Na-alginate) and water (as solvent) for electrode preparation. The as-developed environment/health friendly ‘aqueous-processed’ electrode also exhibits excellent long-term cyclic stability, with capacity retention being ∼82% after 100 cycles (∼60% after 500 cycles and ∼56% after 750 cycles) at C/5, along with just ∼4% capacity fade over the last 250 cycles investigated (viz., cycles 500–750). Such an elimination of requirements for toxic/hazardous-cum-expensive ‘non-aqueous’ solvents/binders for electrode preparation and the associated learning, in terms of suitable combinations of TM-/non-TM-ions for these oxides in the pursuit of desired structural features, are significant steps towards the development of alkali metal-ion batteries in general.

Question: What's the electrolyte?