WP Nanocrystals on N,P Dual-Doped Carbon Nanosheets with Deeply Analyzed Catalytic Mechanisms for Lithium–Sulfur Batteries

Open AccessCCS ChemistryRESEARCH ARTICLES14 Nov 2022WP Nanocrystals on N,P Dual-Doped Carbon Nanosheets with Deeply Analyzed Catalytic Mechanisms for Lithium–Sulfur Batteries Peng Wang, Zhengchunyu Zhang, Ning Song, Xuguang An, Jie Liu, Jinkui Feng, Baojuan Xi and Shenglin Xiong Peng Wang School of Chemistry and Chemical Engineering, State Key Laboratory of Crystal Materials, Shandong University, Jinan 250100 Google Scholar More articles by this author , Zhengchunyu Zhang School of Chemistry and Chemical Engineering, State Key Laboratory of Crystal Materials, Shandong University, Jinan 250100 Google Scholar More articles by this author , Ning Song School of Chemistry and Chemical Engineering, State Key Laboratory of Crystal Materials, Shandong University, Jinan 250100 Google Scholar More articles by this author , Xuguang An School of Mechanical Engineering, Chengdu University, Chengdu 610106 Google Scholar More articles by this author , Jie Liu The State Key Laboratory of High Performance Ceramics and Superfine Microstructure, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050 Google Scholar More articles by this author , Jinkui Feng School of Materials Science and Engineering, Shandong University, Jinan 250061 Google Scholar More articles by this author , Baojuan Xi *Correspondence authors: E-mail Address: [email protected] E-mail Address: [email protected] School of Chemistry and Chemical Engineering, State Key Laboratory of Crystal Materials, Shandong University, Jinan 250100 Google Scholar More articles by this author and Shenglin Xiong *Correspondence authors: E-mail Address: [email protected] E-mail Address: [email protected] School of Chemistry and Chemical Engineering, State Key Laboratory of Crystal Materials, Shandong University, Jinan 250100 Google Scholar More articles by this author https://doi.org/10.31635/ccschem.022.202202163 SectionsSupplemental MaterialAboutAbstractPDF ToolsAdd to favoritesDownload CitationsTrack Citations ShareFacebookTwitterLinked InEmail The use of transition-metal phosphides (TMPs) as catalytic materials to accelerate kinetics of lithium polysulfide (LiPS) conversion has unique advantages. Nevertheless, simple and low-cost preparation strategies are still required for the synthesis of novel TMPs with satisfactory performance. Importantly, the in-depth understanding of the effect of intrinsic interaction between catalytic materials and LiPSs on the promoted kinetics remains limited. Herein, a novel structure of tungsten phosphide (WP) nanocrystals decorated on N,P codoped carbon sheets (WP/NPC) with uniform dispersion is designed by a structure-oriented strategy to promote LiPS redox kinetics. The electrochemical kinetics measurements coupled with density functional theory computations and in situ/ex situ characterizations demonstrate that the strong interaction through W–S bonding and the favorable interfacial charge state of WP-LiPSs promote the nucleation and dissociation of Li2S. Benefiting from this superiority, the WP/NPG-based lithium–sulfur batteries indicate significantly improved electrochemical performance with good cycling life and excellent rate capability. This work provides a methodology for the design of TMP-involved electrode materials and a fundamental understanding of the intrinsic mechanism of catalysis. Download figure Download PowerPoint Introduction With the rapid growth in the production of portable electronics and electric vehicles, the traditional lithium–ion battery system shows a series of deficiencies in terms of energy density, safety, and cost, which has motivated the development and application of emerging energy storage devices.1–3 Among a variety of candidates, lithium–sulfur batteries (LSBs) integrate a multielectron electrochemical reaction and high average voltage of about 2.15 V and are endowed with high theoretical energy density.4,5 Combined with the features of richness of S in the earth, low cost, and environmental benignity, LSBs are regarded as the next-generation battery system with the most potential for application.5,6 However, affected by sluggish redox kinetics and the insulating nature of S, LSBs are faced with incomplete conversion of the sulfur and the “shuttle effect” from the dissolved intermediate polysulfides (LiPSs).7–9 In past research, the shuttle effect was alleviated to some extent by designing porous carbon materials as S hosts to physically limit the dissolution of LiPSs.10–12 Considering the continuous generation of LiPSs and the weak affinity toward polar LiPSs, the space confinement and physical adsorption by carbon materials cannot enable the long cycle of batteries. Inspired by the flood management strategy, the shuttle effect can be fundamentally suppressed by accelerating the conversion between LiPSs and Li2S instead of roughly blocking the LiPSs dissolution.13–15 In this respect, carbon-composited transition metal compounds with high catalytic activity can act as an accelerator of S to achieve high-performance LSBs.16 Further, regulating the type of transition metals and the exposure of active sites can successfully engineer the catalytic behavior.17–19 As a nascent catalytic material, transition-metal phosphides (TMPs), characterized by metallic electrical conductivity and moderate adsorption toward LiPSs, can furnish smooth channels for ions/electrons, which have aroused tremendous research interest.20,21 In recent years, a wide range of TMPs (CoP, Ni2P, FeP, and MoP) have been applied to prompt the LiPSs redox kinetics, and the underlying mechanisms of regulating LiPS transformation have been also explored.22–25 Despite these remarkable achievements, research into tungsten phosphide (WP) in the Li–S system has rarely been reported. With regard to synthesis, the phosphating process usually requires multiple complex steps and a large amount of phosphorus sources (such as NaH2PO2 or a high-boiling organic solvent).26 In addition, it is of great urgency to fully expose the active site of TMPs and achieve structural stability in the catalytic process through structural design. In this respect, it is extremely valuable for the development of convenient and environmentally friendly strategies toward synthesizing TMPs with excellent catalytic activity. Furthermore, theoretical studies have been effectively used to investigate the corresponding catalytic mechanism. For example, the catalytic materials can achieve accelerated Li2S decomposition in the charging process by reducing the diffusion energy barrier of lithium ions and promote Li2S nucleation in the discharging process by decreasing the Gibbs-free energy changes required for LiPSs conversion.27,28 However, the effect of interaction between catalytic materials and LiPSs in the acceleration of electron/ion transport remains to be explored. To address the above issues, a “structure-oriented template” combined with an “in situ self-phosphating” strategy was designed to prepare ultrafine tungsten phosphide (WP) nanocrystals on N,P codoped carbon sheets (WP/NPC) as the catalytic S host. This ingenious synthesis process harvested the WP/NPC through a one-step reaction without the addition of an additional phosphorus source. Systematic electrochemical analyses and structural characterizations showed us that the WP/NPC was rich in catalytic active sites and contributed to the strong affinity with and accelerated bidirectional conversion toward LiPSs. Correspondingly, the as-assembled LSBs delivered stable cycling stability of 786 mAh g−1 after 600 cycles at 0.5 C (corresponding to a capacity decay rate of 0.05% per cycle), superior rate performance of 740 mAh g−1 at 6 C, and high S-loading performance. With a combination of between in situ characterizations and density functional theory (DFT) computations, the electrocatalytic mechanisms were further investigated. On the one hand, this favorable interfacial charge state effectively reduces the electron transfer resistance, which promotes the reduction of Li2S4, that is, the Li2S/Li2S2 nucleation. On the other hand, the strong interaction between WP and Li2S through W–S bonding demonstrates that the WP specializes in “tearing” Li–S bonding to facilitate the dissociation of Li2S. We shed some light on a deeper understanding of LiPS electrodeposition and decomposition reactivity, which provides the necessary theoretical and experimental basis for the large-scale application of LSBs. Experimental Section Synthesis of NPC and WP/NPC The WP/NPC was synthesized through a one-step metal chelate-assisted template self-sacrifice method. In a typical synthesis, 0.3 g of ammonium metatungstate (H28N6O41W12) and 1 mL of phytic acid (PA) were mixed into 50 mL of distilled water with violent stirring to form a uniform solution. Then 5 g of melamine (MA) was added into the above solution followed by stirring it at room temperature to guarantee the full reaction. The precursor MA–PA–W12O39 hybrid was obtained after drying the above mixture in an oven at 80 °C. The as-synthesized precursor MA–PA–W12O39 was heated at 850 °C for 2 h under an Ar atmosphere with a heating rate of 5 °C min−1 to obtain the WP/NPG. For comparison, the NPG matrix was synthesized with similar procedures without the introduction of H28N6O41W12. Preparation of [email protected] and [email protected]/NPC-based cathodes The [email protected] and [email protected]/NPC cathodes were prepared through a traditional melting-infiltrating method. First, the sublimed sulfur power and WP/NPC (NPC) were mixed thoroughly (7:3 by mass) and heated at 155 °C for 12 h and then 185 °C for 2 h in an Ar-filled glass bottle to attain [email protected] and [email protected]/NPC. Then the prepared [email protected] or [email protected]/NPC, acetylene black, and polyvinylidene fluoride (PVDF) were mixed in N-methylpyrrolidone with the mass ratio of 8:1:1 and blading onto the carbon-coated Al foil. The obtained electrodes were dried in a vacuum oven at 80 °C for 12 h and cut into discs with a diameter of 12 mm. The sulfur loading in the [email protected] and [email protected]/NPC cathodes was about 1.1–10.5 mg cm−2. Materials characterization The phase composition and surface chemistry of the samples were characterized by X-ray diffraction (XRD, SmartLab, using Cu Kα radiation, Rigaku, Japan) and X-ray photoelectron spectroscopy (XPS, ESCALAB 250Xi spectrometer, Thermo Fisher, Waltham, Massachusetts, USA). The structure and morphology were characterized by high-resolution field-emission transmission electron microscopy (ARM-200F, JEOL, Shojima City, Tokyo, Japan), field-emission scanning electron microscopy (Gemini300, Zeiss, Oberkochen, Bartenburg, Germany). The Brunauer–Emmett–Teller (BET)-specific surface areas and pore size distribution were obtained by N2 sorption measurement (ASAP 2460 system, Micromeritics, Norcross, Georgia, USA). Thermogravimetric analysis (TGA, STA 449 F3, NETZSCH, Selb, Germany) was measured under the air with a heating rate of 10 °C min−1 from 30 to 800 °C to measure the content of WP. It should be mentioned that the WP can be fully oxidized into WO3 after calcining it to 800 °C at air atmosphere. In this contribution, the results were calculated based on the following equation: 2 WP + 11 / 2 O 2 → 2 WO 3 + P 2 O 5 WP was transformed into WO3, and the P2O5 was vaporized at high temperature, accompanied by a mass decrease of 8%. We assume that the total mass of WP/NPG is 1, and the mass percentage of NPG in the WP/NPG is x, so the mass percentage of WP is (1 − x). Then, x − 8% (1 − x) = 8%. So, we get x = 14.8%, and the content of WP in WP/NPG is 85.2%. Electrochemical measurements The electrodes for the measurement of symmetric cells, Li2S nucleation, and decomposition were prepared by the WP/NPC (or NPC) and PVDF with the mass ratio of 9:1. The electrolyte was 0.15 M Li2S6 electrolyte (in 1,3-dioxolane/ dimethoxyethane (DOL/DME) with 2.0 wt % LiNO3). The symmetric cells were assembled with two identical electrodes as working and counter electrodes. And the cyclic voltammetry (CV) measurements were carried out in the voltage range of −0.8 to 0.8 V at the scan rate of 0.2 mV s−1. The electrochemical impedance spectrum (EIS) tests were performed on the CHI–760E electrochemical workstation with the applied frequency range from 0.1 Hz to 100 kHz. The cells for Li2S nucleation and decomposition were assembled by the above active electrodes as working electrode and lithium foil as counter electrode, in which 20 μL of Li2S6 electrolyte and 15 μL of blank electrolyte (without Li2S6) were employed as catholyte and anolyte, respectively. During the Li2S nucleation measurement, the assembled cells were discharged galvanostatically to 2.06 V and afterwards kept at a potentiostatical voltage of 2.05 V until the current decreased to 10−5 A. For the following Li2S dissolution measurement, the cells were potentiostatically charged at 2.35 V until the current was below 10−5 A. The Tafel plots were conducted on the same cell systems with Li2S nucleation, which were tested at a CHI–760E electrochemical workstation at a scan rate of 2 mV s−1 in the voltage range from −150 to +150 mV. And the exchange current density of the oxidation/reduction reactions were calculated through manually fitting them according to the Bulter–Volmer equation. The LSBs were assembled in CR2016 coin-type cells with the as-prepared [email protected] and [email protected] WP/NPC cathodes, Celgard 2325 separator, and conventional Li–S electrolyte (1.0 M LiTFSI in DOL/DME (v/v = 1:1) with 1 wt % LiNO3) in an Ar-filled glove box. Lithium ion diffusion coefficients were calculated by a series of CVs at different scan rates, and the peak current data were analyzed with the Randles–Sevcik equation I P = ( 2.65 × 10 5 ) n 1 .5 S D Li + 0.5 C Li + v 0 .5 where IP represents the peak current, n is the number of transferred electrons (for Li–S batteries, n = 2), S is the electrode area, CLi+ represents the lithium ion concentration in the electrolyte, and v indicates the scanning rate. The CV and charging/discharging test were conducted in a CHI–760E electrochemical workstation and LAND CT-2001A battery test station over the range of 1.7–2.8 V versus Li+/Li. DFT calculations All the DFT calculations were conducted using the Vienna Ab-initio Simulation Package following the projector-augmented wave method. The ground state electronic calculations were calculated by the generalized gradient approximation and the Perdew–Burke–Ernzerhof functions. The supercell of WP and NPG containing 4 × 4 unit cells was used. During the process of geometry optimization, a kinetic energy cutoff of 400 eV and 2 × 2 × 1 Monkhorst-Pack k-mesh for the Brillouin zone were used. The convergence tolerance was reached when the energy change was smaller than 10−6 eV, and 0.01 eV Å−1 for maximum residual force. The spin polarization was considered in all calculations. The optB86b-vdW function was used to describe physical van der Waals interaction, which explicitly accounted for the binding energy and optimization simulations. The binding energies of Li2Sx on different surfaces were obtained as follows: − B E = E ( surface ) + E ( Li 2 S x ) − E ( total ) The transition state of Li2S decomposition and Li+ transfer on the surface of WP and NPC was located by the nudged elastic band (NEB) method, where the initial and finial states were discretized. Results and Discussion Material synthesis and characterization The delicately designed “structure-oriented template” coupled with “in situ self-phosphating” strategy was developed to prepare highly dispersed tungsten phosphide (WP) ultrafine nanocrystals decorated on the N,P co-doped carbon sheets (WP/NPC). The synthetic process of WP/NPC is schematically illustrated in Figure 1a, and the detailed descriptions are presented in the Experimental Section. PA with strong chelating ability coordinated with both metal ions and proteins through its six reactive phosphate groups.29 During the synthesis of the precursor (denoted as MA–PA–W12O39), PA served as a bidirectional functional agent to link the tungsten source (W12O39) with the carbon precursor (MA) under mild conditions.26 The expected WP/NPC was harvested in the subsequent annealing process, during which MA–PA–W12O39 worked as self-sacrificing template for the self-assembly of WP nanocrystals and N/P co-doped carbon sheets. It should be mentioned that the growth of WP crystals was strongly directed by the coordination between PA and W12O39. Benefiting from this, the formation of highly dispersed WP ultrafine nanocrystals was achieved. Figure 1 | (a) Synthesis schematic illustration, (b) TEM image, (c and d) HAADF-STEM images, and (e) corresponding EDS mapping of WP/NPC. Download figure Download PowerPoint As can be seen from Supporting Information Figure S1, the scanning electron microscope (SEM) image of precursor MA–PA–W12O39 shows obvious lamellar structure, and the corresponding energy dispersive spectroscopy (EDS) demonstrates the coexistence of C, N, P and W elements. To further figure out the structure and formation of MA–PA–W12O39, Fourier transform infrared spectra were obtained for the MA, PA, and MA–PA–W12O39 ( Supporting Information Figure S2). The characteristic peak located at 814 cm−1 corresponds to the triazine ring vibration of MA and shifts to 780 cm−1 in MA–PA–W12O39, which originates from the deformation of the aromatic ring and protonation of the triazine rings. The peak at 957 cm−1 of PA assigned to the –PO4 groups shifts to 980 cm−1 in MA–PA–W12O39. The blueshift phenomenon mentioned above demonstrates the formation of hydrogen bonding between MA and PA.26 The structural feature of the as-formed WP/NPC was characterized by transmission electron microscopy (TEM). As shown in Figure 1b, the highly distributed WP ultrafine nanocrystals embed in the NPC, where the WP nanograins have the average crystal size of about 5 nm. Such structure with nanocrystals of small size that are well dispersed on thin carbon sheets, tends to expose abundant active sites for the construction of catalyst/electrolyte/reactant triple-phase boundaries. It can exhibit great potential to provide high catalytic activity for the Li–S electrochemistry. The high-angle annular dark field-scanning TEM (HAADF-STEM) images in Figure 1c,d also show the tightly fixed WP nanocrystals on the NPC and the obvious spacing of 0.288 nm for the (011) plane of WP phase. The corresponding elemental mappings of WP/NPC (Figure 1e) indicate that the C, N, P, and W are uniformly distributed throughout the total scanning region, which further confirms the uniformity of WP NPs and successful N,P functionalization of carbon sheets. The phase composition of WP/NPC is further determined by the XRD pattern. As shown in Figure 2a, all the diffraction peaks can be indexed to the orthorhombic WP (PDF#29-1364) without any impurities. TGA was implemented to evaluate the WP content within the WP/NPC hybrid. As can be seen from Figure 2b, the WP loading content is calculated to be about 85.2 wt % (the detailed calculation is presented in the Experimental Section). The BET-specific surface area of WP/NPC is evaluated to be 665 m2 g−1 by the nitrogen adsorption–desorption isotherms. And it possesses abundant micropores (<2 nm) (Figure 2c). This favorable surface configuration is conducive to abundant active areas for the adsorption and transformation of LiPSs. In order to further investigate the surface chemical state of WP/NPC, XPS analysis was used and shown in Figure 2d and Supporting Information Figure S3. Two peaks at around 32.3 and 34.5 eV in W 4f spectrum correspond to the W 4f7/2 and W 4f5/2, respectively.30 In P 2p spectrum, the doublet peaks at 130.7 and 129.8 eV are assigned to the P 2p1/2 and P 2p3/2 of W–P bonding. In addition, the obvious N 1s peaks are featured with pyridinic N (398.3 eV), pyrrolic N (399 eV), and graphitic N (401.4 eV), further confirming N doped into the carbon lattice, which has been reported to synergistically enhance the adsorption toward the LiPSs. Figure 2 | (a) XRD pattern, (b) TGA curve, (c) nitrogen sorption isotherms, and (d) high-resolution XPS spectrum of W 4f for WP/NPC. Inset in panel (c) is the corresponding pore size distribution curve. Download figure Download PowerPoint The SEM and TEM images also show that distinct lamellar structure features NPC with submicron size and the thickness of several nanometers ( Supporting Information Figure S4a,b). The corresponding elemental mappings confirm the presence of N and P elements within carbon sheets ( Supporting Information Figure S4c–f). In addition, the XRD pattern exhibits two broad peaks at 25° and 45° assigned to the carbon ( Supporting Information Figure S5a). The extensive specific surface area of NPC (714 m2 g−1) provides sufficient space for the dispersion of WP NPs ( Supporting Information Figure S5b). Catalytic performance evaluation It has been reported that a highly efficient catalytic process in Li–S chemistry comprises strong adsorption, smooth migration, and accelerated transformation of LiPSs. In this regard, a visual adsorption test was firstly done to validate the interaction between WP and LiPSs species. As shown in Supporting Information Video S1, the Li2S6 solution was dropped into the DME solvent containing a certain amount of NPC, and it was expected to remain yellow after mixing. In contrast, the Li2S6 solution rapidly faded upon being added into the WP/NPC solution with an equal specific surface area to NPC ( Supporting Information Video S2). After resting for 30 min, the WP/NPC-DME solution completely decolored, whereas the NPC-DME solution kept its yellow color ( Supporting Information Figure S6). The surface interactions between WP and LiPSs can be further verified by the XPS technique, where high-resolution XPS spectra of WP/NPC before and after Li2S6 adsorption were calibrated with the reference of the C–C/C=C peak (284.64 eV). As can be seen from Supporting Information Figure S7, the markedly diminished intensity of W 4f5/2, W 4f7/2, P 2p1/2, and P 2p3/2 bands after Li2S6 adsorption reveals the interaction with Li2S6 on the surface. Moreover, the W 4f5/2 and W 4f7/2 peaks shift negatively by 0.2 eV after interacting with Li2S6, implying the electrons transfer from Li2S6 to the unfilled d orbitals of W ions to form S–W bonding based on the Lewis acid–base theory.31 These observations are evidence that the WP/NPC affords strong adsorbability toward LiPSs species through S–W bonding, which is beneficial to the inhibition of the shuttle effect and the ensuing diffusion and conversion of LiPSs. As the second step of the catalytic process, the migration rate of LiPSs determines the conversion kinetics, which was reflected by the lithium ion diffusion coefficient (DLi+).32,33 Considering that, the DLi+ values are evaluated by the Randles–Sevcik equation according to the CV curves of [email protected]/NPC and [email protected] As displayed in Figure 3a–f, the [email protected]/NPC electrode exhibits much higher DLi+ for peaks 1, 2, and 3 (1.83 × 10−8, 2.54 × 10−8, and 4.3 × 10−8 cm2 s−1) than its [email protected] counterparts (0.83 × 10−8, 0.94 × 10−8, and 1.6 × 10−8 cm2 s−1). It is obvious that with WP/NPC as the sulfur host the LiPSs can diffuse faster than in the case of the NPC matrix. Figure 3 | CV curves of the LSBs assembled with (a) [email protected] and (b) [email protected]/NPC. (c) The summary of DLi+ values. The linear fitting results of the peak current as a function of scan rate for different LSBs at (d) reductive peak 1, (e) reductive peak 2, and (f) oxidative peak 3. Download figure Download PowerPoint Given the intricate redox reaction of LSBs caused by multifarious LiPSs species and multistep reactions, the WP/NPC potentialities for boosting LiPSs redox kinetics were extensively investigated. As shown in Figure 4a, the electrocatalytic activity of WP/NPC was initially estimated by the exchange-current density (i0) measurements, and the i0 values were calculated from the fitted Tafel curves. The WP/NPC exhibited much higher i0 (0.68 mA cm−2 for the oxidation reaction and 0.72 mA cm−2 for reduction reaction) than NPC (0.01 mA cm−2 for both oxidation and the reduction reaction). Furthermore, the CV curves of symmetrical cells were calculated to assess the liquid–liquid conversion. In Figure 4b, at a scan rate of 0.2 mV s−1, the WP/NPC-based symmetry cell exhibits two pairs of redox peaks at ±0.05 and ±0.34 V with high current response, which are assignable to the two-step transformation between Li2S6 and Li2S. In sharp contrast, the absence of redox peaks and reduced current was observed in the NPC-based symmetry cell. It should be mentioned that the redox peaks were still maintained even if the scan rate is up to 20 mV s−1, which indicates rapid electron/ion exchange and superior electrochemical reversibility assisted by the catalysis of WP/NPC ( Supporting Information Figure S8). Meanwhile, from the EIS (Figure 4c), the WP/NPC-based symmetrical cell has a decreased charge transfer impedance (Rct) of 36 Ω compared with the NPC counterpart (69 Ω). Both the higher i0 and the current response of the symmetry cells imply that the WP/NPC played a distinct role in accelerating dynamic transformation between S and Li2S. Figure 4 | (a) The Tafel curves and (b) CV curves of symmetric cells for the NPC and WP/NPC electrodes. (c) EIS of NPC- and WP/NPC-based symmetric cells. The inset shows the corresponding equivalent circuit. Potentiostatic discharge profiles at a voltage of 2.05 V for the (d) WP/NPC and (e) NPC electrodes. (f) Potentiostatic charge profiles at 2.35 V for the WP/NPC and NPC electrodes. Download figure Download PowerPoint Liquid–solid conversion largely determines the discharging process, so the regulation role of WP/NPC toward the conversion from LiPS to Li2S needs to be investigated through the Li2S precipitation experiments. In Figure 4d,e, the WP/NPC based electrode not only reaches the peak with an earlier peak time (316 s) but also delivers more dominant Li2S nucleation capacity (287 mAh g−1) than the NPC-based electrode (984 s and 133 mA g−1). The significantly greater deposition capacity is known to be influenced by the morphology of the deposited Li2S. To gain further insight into the above result, the dimensionless current–time transient was further fitted, and the SEM images of deposited electrodes were synchronously monitored. As shown in Supporting Information Figures S9 and S10a,b, a traditional two-dimensional (2D) growth model happens in the NPC case, consistent with the visual 2D sheet-like morphology of Li2S2/Li2S deposition. This common morphology in ether electrolyte impedes the electronic transfer from conductive substrate to the insulating Li2S, unfavorable for the continual deposition and subsequent decomposition of Li2S. With the introduction of WP, the Li2S deposition follows a unique quasi-three-dimensional deposition model and is characterized with thick moss-like morphology, tightly anchored on the surface of the WP/NPC electrode ( Supporting Information Figure S10c,d). The formation of favorable Li2S morphology mainly pertains to the high catalytic effect and abundant active sites of WP/NPC, which accelerate the nucleation and growth of Li2S. For a more accurate demonstration of the improved kinetics toward the solid–liquid conversion process, the oxidation of deposited Li2S was examined with a constant potential of 2.35 V for the fully discharged electrodes. As shown in Figure 4f, the WP/NPC-based cell offers the significantly increased oxidation current density of 1757 mA g−1 and earlier peak time of 725 s than the NPC-based cell (685 mA g−1 and 1375 s), which suggests an elevated dynamic for the Li2S conversion assisted by the introduction of WP nanocrystals. DFT calculations This remarkable catalytic performance impelled us to investigate the LiPS conversion by WP nanocrystals in greater depth through theoretical analyses. Rapid electron transport is indispensable to the facilitation of LiPS redox and improved electrochemical performance. In this respect, the electronic structure of WP was analyzed through the total density of states (DOS). In Figure 5a, the notable absence of b