The development of low-cost and long-lasting all-climate cathode materials for the sodium ion battery has been one of the key issues for the success of large-scale energy storage. One option is the ...utilization of earth-abundant elements such as iron. Here, we synthesize a NASICON-type tuneable Na
Fe
(PO
)
(P
O
)/C nanocomposite which shows both excellent rate performance and outstanding cycling stability over more than 4400 cycles. Its air stability and all-climate properties are investigated, and its potential as the sodium host in full cells has been studied. A remarkably low volume change of 4.0% is observed. Its high sodium diffusion coefficient has been measured and analysed via first-principles calculations, and its three-dimensional sodium ion diffusion pathways are identified. Our results indicate that this low-cost and environmentally friendly Na
Fe
(PO
)
(P
O
)/C nanocomposite could be a competitive candidate material for sodium ion batteries.
One major challenge in the field of lithium-ion batteries is to understand the degradation mechanism of high-energy lithium- and manganese-rich layered cathode materials. Although they can deliver 30 ...% excess capacity compared with today's commercially- used cathodes, the so-called voltage decay has been restricting their practical application. In order to unravel the nature of this phenomenon, we have investigated systematically the structural and compositional dependence of manganese-rich lithium insertion compounds on the lithium content provided during synthesis. Structural, electronic and electrochemical characterizations of Li
Ni
Mn
O
with a wide range of lithium contents (0.00 ≤ x ≤ 1.52, 1.07 ≤ y < 2.4) and an analysis of the complexity in the synthesis pathways of monoclinic-layered LiLi
Ni
Mn
O
oxide provide insight into the underlying processes that cause voltage fading in these cathode materials, i.e. transformation of the lithium-rich layered phase to a lithium-poor spinel phase via an intermediate lithium-containing rock-salt phase with release of lithium/oxygen.
Herein, we introduce a 4.0 V class high‐voltage cathode material with a newly recognized sodium superionic conductor (NASICON)‐type structure with cubic symmetry (space group P213), Na3V(PO3)3N. We ...synthesize an N‐doped graphene oxide‐wrapped Na3V(PO3)3N composite with a uniform carbon coating layer, which shows excellent rate performance and outstanding cycling stability. Its air/water stability and all‐climate performance were carefully investigated. A near‐zero volume change (ca. 0.40 %) was observed for the first time based on in situ synchrotron X‐ray diffraction, and the in situ X‐ray absorption spectra revealed the V3.2+/V4.2+ redox reaction with high reversibility. Its 3D sodium diffusion pathways were demonstrated with distinctive low energy barriers. Our results indicate that this high‐voltage NASICON‐type Na3V(PO3)3N composite is a competitive cathode material for sodium‐ion batteries and will receive more attention and studies in the future.
A new NASICON‐type high‐voltage cathode material of Na3V(PO3)3N was synthesized and its electrochemical performance was improved by carbon matrix decoration. An in‐depth investigation of the material was performed through in situ XAS and XRD, and its 3D sodium pathways were clearly identified through DFT calculations.
Limited energy density of today's Li-ion battery technologies demands for novel cell technologies, such as the all-solid-state battery (ASSB). In order to achieve high energy densities and enable ...large-scale processing, thin and flexible solid electrolyte (SE) layers have to be implemented. This study focuses on slurry-based processing of the sulfidic solid electrolyte Li10SnP2S12 (LSPS). Various polymers were investigated concerning their suitability as binders for thin and freestanding SE sheets. We conducted a parameter study in order to optimize e.g. LSPS-to-binder ratio, solids content and porosity. Significant differences were found with regard to the minimum amount of binder required for mechanically stable sheets as well as the homogeneity, density and flexibility of the resulting SE layers. The impacts of binder type and weight fraction on ionic conductivity were examined through lithium diffusion measurements. Impedance analysis was conducted in comparison, proving sufficiently high ionic conductivity for potential application of the SE sheets in ASSB. This work highlights the important role of the polymeric binder in slurry-based processing of SEs and gives an impression how important a well-considered selection of parameters is to achieve good processing properties as well as desirable features for the final SE sheet.
Glassy, glass–ceramic, and crystalline lithium thiophosphates have attracted interest in their use as solid electrolytes in all-solid-state batteries. Despite similar structural motifs, including PS4 ...3–, P2S6 4–, and P2S7 4– polyhedra, these materials exhibit a wide range of possible compositions, crystal structures, and ionic conductivities. Here, we present a combined approach of Bragg diffraction, pair distribution function analysis, Raman spectroscopy, and 31P magic angle spinning nuclear magnetic resonance spectroscopy to study the underlying crystal structure of Li4P2S6. In this work, we show that the material crystallizes in a planar structural arrangement as a glass ceramic composite, explaining the observed relatively low ionic conductivity, depending on the fraction of glass content. Calculations based on density functional theory provide an understanding of occurring diffusion pathways and ionic conductivity of this Li+ ionic conductor.
Glass–ceramic solid electrolytes have been reported to exhibit high ionic conductivities. Their synthesis can be performed by crystallization of mechanically milled Li2S–P2S5 glasses. Herein, the ...amorphization process of Li2S–P2S5 (75:25) induced by ball milling was analyzed via X-ray diffraction (XRD), Raman spectroscopy, and 31P magic-angle spinning nuclear magnetic resonance (NMR) spectroscopy. Several structural building blocks such as P4S10, P2S64–, P2S74–, and PS43– occur during this amorphization process. In addition, high-temperature XRD was used to study the crystallization process of the mechanically milled Li2S–P2S5 glass. Crystallization of phase-pure β-Li3PS4 was observed at temperatures up to 548 K. The kinetics of crystallization was analyzed by integration of the intensity of the Bragg reflections. 7Li NMR relaxometry and pulsed field-gradient (PFG) NMR were used to investigate the short-range and long-range Li+ dynamics in these amorphous and crystalline materials. From the diffusion coefficients obtained by PFG NMR, similar Li+ conductivities for the glassy and heat-treated samples were calculated. For the glassy sample and the glass–ceramic β-Li3PS4 (calcination at 523 K for 1 h), a Li+ bulk conductivity σLi of 1.6 × 10–4 S/cm (298 K) was obtained, showing that for this system a well-crystalline material is not essential to achieve fast Li-ion dynamics. Impedance measurements reveal a higher overall conductivity for the amorphous sample, suggesting that the influence of grain boundaries is small in this case.
Inspired by the ongoing search for new superionic lithium thiophosphates for use in solid-state batteries, we present the synthesis and structural characterization of Li2P2S6, a novel crystalline ...lithium thiophosphate. Whereas M2P2S6 with the different alkaline elements (M = Na, K, Rb, Cs) is known, the lithium counterpart has not been reported yet. Herein, we present a combination of synchrotron pair distribution function analysis and neutron powder diffraction to elucidate the crystal structure and possible Li+ diffusion pathways of Li2P2S6. Additionally, impedance spectroscopy is used to evaluate its ionic conductivity. We show that Li2P2S6 possesses P2S6 2– polyhedral units with edge-sharing PS4 tetrahedra and only one-dimensional diffusion pathways with localized Li–Li pairs, leading to a low ionic conductivity for lithium.
The interest in all solid-state batteries has increased notably over the last years. Reasons are, among others, the demand for higher energy densities in storage devices and considerable safety ...issues in classical battery systems based on liquid electrolytes. One solution is the usage of solid electrolytes in battery systems. Because the crystal structure highly correlates with ion migration, the focus of our work is a detailed determination of the structure and Li pathways in the solid electrolyte argyrodite-type Li6PS5Cl. With neutron diffraction an additional Li site was experimentally detected. The comparison of maximum entropy method and differential bond valence analysis revealed the Li ion hopping pathways. With pair-distribution function analysis, a distortion of the PS43– tetrahedra resulting in a local monoclinic structure is found. A modulation of the local monoclinic structure is averaged out on longer length scales to an overall cubic structure that is known from the literature.
A novel crystalline lithium superionic conductor, Li4PS4I, has been discovered utilizing a solvent-based synthesis approach. It was found that the starting material Li3PS4·DME reacts with LiI in a ...1:1 ratio in DME to give a precursor that results in Li4PS4I after soft heat treatment at around 200 °C in vacuum. Its crystal structure was solved ab initio by evaluating both X-ray (Mo-Kα1) and neutron (TOF, GEM, ISIS) powder diffraction data, in a combined refinement (P4/nmm, Z = 2, a = 8.48284(12) Å, c = 5.93013(11) Å, wRp = 0.02973, GoF = 1.21499). The final structure model comprises, besides Li+ ions, isolated PS4 3– tetrahedra in a layer-like arrangement perpendicular to the c-axis that are held apart by I– ions. The Li+ ions are distributed over five partially occupied sites residing in 4-, 5-, and 6-fold coordination environments. A topostructural analysis of the voids and channels within the PS4I4– substructure suggested a three-dimensional migration pathway system for the Li+ ions in Li4PS4I. The Li+ ion mobility was studied by temperature-dependent impedance spectroscopy as well as 7Li solid-state nuclear magnetic resonance (NMR) spectroscopy including the measurement of spin–lattice relaxation rates T 1 –1. The total ionic conductivity was determined to be in the range of 6.4 × 10–5 to 1.2 × 10–4 S·cm–1 at room temperature with activation energies (E A) of 0.37 to 0.43 eV. The NMR analyses revealed a hopping rate of the Li+ ions of τ–1 = 5 × 108 s–1 corresponding to a bulk conductivity of 1.3 × 10–3 S·cm–1 at 500 K and an activation energy E A = 0.23(1) eV.
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