Nasicon-type Phosphate Research Articles

Optimizing the crystal structure and electrochemical properties of Na4MnCr(PO4)3 by trace La doping

Na4MnCr(PO4)3, a manganese-based NASICON-type phosphate cathode material, is attracted considerable attention due to its high voltage and energy density. However, its practical application is hindered by poor electronic conductivity and inferior sodium ion diffusion kinetics. In this study, trace La3+ is utilized to optimize the lattice structure of Na4MnCr(PO4)3 due to its unique energy level structure. La3+ doping significantly enhances the local environment of the Mn-O bond and stabilizes the lattice structure by improving covalency, thereby mitigating Mn dissolution during charge–discharge cycles. Additionally, the large ionic radius of La3+ promotes the sodium ion transport kinetics by expanding the cell volume and facilitating rapid sodium storage. As a result, the optimal Na4MnCr0.995La0.005(PO4)3/C sample demonstrates an impressive initial discharge specific capacity of 124.5 mAh g−1 at 0.1C and superior cycling stability with a capacity retention of 70.2 % after 500 cycles at 5C. Furthermore, density functional theory calculations indicate that La3+ doping can enhance conductivity and reduce the energy barrier for sodium ion diffusion. This study presents an effective and cost-efficient doping strategy for modifying high-energy density NASICON-type phosphate cathode materials, showing promising potential in the field of sodium ion batteries.

Investigation of Zn Doped Li1.5Al0.5−xZnxGe1.5(PO4)3 (x = 0, 0.1 & 0.2) as a Solid Electrolyte for Li Ion Batteries

All solid lithium-ion batteries (ASLB) have gained a lot of attention as it could deliver high energy and power density. In order to completely establish ASLB, proper understanding of solid electrolyte is very vital and the research from diverse point is still undergoing. Among them, NASICON-type phosphate based solid electrolytes are one of the promising materials due to good ionic conductivity and atmospheric stability. Addition of proper dopants into the parent material could cause an increment in their ionic conductivity as well as stability, thus fitting the material apt as solid electrolyte. This study aims in understanding the effect of ionic conductivity and stability of Lithium Aluminium Germanium Phosphate (LAGP) material upon adding Zinc as dopant material. We explored the effect of structural, ionic conductivity, stability against Li and Ac conductivity properties of Li1.5Al0.5−xZnxGe1.5(PO4)3 solid electrolyte with x = 0, 0.1 and 0.2. Our study showed that doping of aluminium with slightly bigger Zn ion could enhance the stability and conductivity of the material without changing the crystal structure. When x = 0.1 the ionic conductivity of the material attained is 1 × 10−5 S cm−1 at RT, which reaches 2.57 × 10−5 S cm−1 at 60 °C. Such a change in conductivity arises due to the expansion of ionic pathways which can be further tuned by exploring the limiting concentration 0 ≤ x < 0.1. Moreover, the sample also showed good stability at 0.03 and 0.05 mA cm−2 current densities against Li metal. Present study shows that Zn doping can improve the ionic conductivity of LAGP moderately and it can be used as a solid electrolyte for fabricating all-solid-state batteries.

Redox Couple Modulation in NASICON Phosphates toward High-Performance Cathodes for Na-Ion Batteries

Natrium superionic conductor (NASICON)-type phosphates have aroused a great interest as cathode materials for sodium-ion batteries (SIBs) by virtue of their stable 3-dimensional frameworks, flexible molecular formula tunability, and superior ionic conductivity. Nevertheless, the intrinsic low electronic conductivity and relatively low theoretical specific capacity place obstacles in their way toward achieving higher electrochemical performance. In addition, only 2-electron reactions in most NASICON cathodes and poor reversibility of high-voltage redox couples severely limit their energy density. To address the above tough issues, an in-depth understanding of transition metal selection, elements ratio optimization, and Na-storage mechanism is of paramount importance. Here, this mini review summarizes the latest progresses on the NASICON-type phosphate cathodes for SIBs from the perspective of redox couple modulation. NASICON cathodes featuring high operating voltage and multielectron reactions are discussed in detail. Finally, the remaining challenges and personal outlooks based on redox couple regulation are put forward, shedding light on the designing rules for high-energy and long-durability NASICON-type phosphate cathodes for SIBs in the future.

Energy Transfer Processes in NASICON-Type Phosphates under Synchrotron Radiation Excitation

The luminescence properties of NASICON-type Na3.6M1.8(PO4)3 (M = Y, Lu) and Na3Sc2(PO4)3 phosphates, undoped and rare earth-doped (RE = Tb3+, Dy3+, Eu3+, Ce3+), were studied using synchrotron radiation in a wide energy region of 4.5–45 eV. Intrinsic emission originating from self-trapped excitons with electron component localized at the 3d Sc states was detected in both doped and undoped Na3Sc2(PO4)3 while only defect-related emission was registered in Na3.6M1.8(PO4)3. Emission of RE ions substituting three-valent cations in low-symmetry sites was detected in all doped phosphates. The efficiency and pass ways of energy transfer from the host to emission centres were analysed based on luminescence excitation spectra. It is shown that the most efficient energy transfer is realized in Tb3+-doped phosphors, while it was poor for other RE ions. The differences in energy transfer efficiencies are explained by different position of RE f states in the crystal electronic band structure influencing the efficiency of charge carrier trapping in the substance. Based on excitation spectra analysis, the bandgap values were estimated to ~8 eV for all studied phosphates.

Synthesis, structure and luminescence properties of the europium–containing NASICON type phosphates

Synthesis, structure and luminescence properties of the europium–containing NASICON type phosphates

Investigation of electronic and photocatalytic properties of AgTi2(PO4)3 NASICON-type phosphate: Combining experimental data and DFT calculations

Ag-based semiconductors have attracted significant attention as promising visible-light photocatalysts for environmental purification. In this study, electronic and photocatalytic properties of AgTi2(PO4)3 NASICON-type phosphate, have been addressed in detail, combining experimental results and theoretical calculations. The as-prepared sample was characterized for its morphological, structural and optical properties by various techniques. The generalized gradient approximation by Perdew-Burke-Ernzerhof (GGA-PPE) within density functional theory (DFT) was used to investigate the electronic structure. We have applied corrective Hubbard U terms to Ti 3d orbitals in order to better reproduce the experimental band gap of 2.6 eV. The photocatalytic activity has then been performed for rhodamine B dye degradation under visible light illumination. Efficient dye degradation up to 97.2 % was achieved in 120 min. In addition, the catalyst exhibited good stability over four consecutive cycles. Finally, combining experimental and theoretical findings, the origin of the photocatalytic activity was identified and a photodegradation mechanism was proposed.

Computational Investigation of a NASICON-Type Solid Electrolyte Material LiGe2(PO4)3

Phosphate-based electrolyte materials are of great interest in the field of Li-ion batteries due to their rigid structural integrity. LiGe2(PO4)3 is a NASICON-type phosphate material with high thermal and electrochemical stability. Computational simulation techniques were employed to study the defects, diffusion, and dopant properties of LiGe2(PO4)3. Furthermore, the reaction energies for the formation of LiGe2(PO4)3 and the incorporation energies for the insertion of additional Li into this material were calculated. The calculations revealed that the Li Frenkel is the lowest-energy defect. The second most favorable defect is the Ge-P anti-site defect cluster. A low Li migration energy of 0.44 eV implies high Li ionic conductivity. The most favorable isovalent dopants on the Li and Ge sites are Na and Si, respectively. The formation of Li interstitials and oxygen vacancies can be facilitated through the doping of Ga on the Ge site. The doping of Ga slightly enhances the Li ionic conductivity. Li incorporation (up to four Li) is thermodynamically feasible.

Recent Progress on Phosphate Cathode Materials for Aqueous Zinc-Ion Batteries.

Rechargeable zinc-ion batteries (ZIBs) are attractive for large-scale energy storage due to their superiority in resources, safety, and environmental friendliness. However, the lack of suitable ZIBs cathode materials limits their practical applications. In consideration of the excellent electrochemical performance of phosphate materials in monovalent ion (Li+ , Na+ ) batteries, they were also employed as ZIBs cathode materials recently and performed well with high potential. But they also suffer from low capacity and poor conductivity, and the energy storage mechanism is not clear yet. This Review provides a state-of-the art overview on the developments of phosphate cathode materials in ZIBs, including NASICON-type phosphates, fluorophosphates, olivine-structured, layered-structured, and novel-structured phosphate materials mainly. This study presents the reaction mechanism and electrochemical performance of phosphate cathode materials in aqueous ZIBs, and future research directions are discussed, which are intended to provide guidance for exploring high-potential cathode materials for ZIBs.

Fe1.5V2(PO4)3/C phosphate as a negative electrode material for high-rate performance lithium-ion batteries

A NaSICon-type phosphate Fe1.5V2(PO4)3/C (FVP/C) was successfully prepared and its crystal structure and electrochemical performance as a negative electrode material for lithium-ion batteries (LIBs) were investigated. The material was synthesized via a sol-gel method and calcined at 800 °C under inert atmosphere. The obtained powder crystallized in the triclinic system with P-1 space group. The structure contains two types of dioctahedral edge-sharing V2O10 groups, while distorted Fe(1)O6 octahedra and trigonal bipyramid Fe(2)O5 were evidenced. The electrochemical performance of FVP/C versus Li+/Li were evaluated in 0.01–3.0 V voltage range. FVP/C exhibited a conversion mechanism and showed good reversible capacities at both high and low rates. The discharge capacities of 463, 307 and 311 mAh g−1 were delivered at 1C, 2C, and 5C after 100 cycles. Moreover, the lithiation/delithiation mechanism in FVP/C was evidenced by Operando diffraction using synchrotron radiations and Ex situ XPS spectroscopy, conforming the amorphization of the studied phosphate and revealing that both vanadium and iron are involved in the redox process upon cycling.

In situ synthesis of selfsupported Ag NPs on AgZr2(PO4)3 NASICON type phosphate: Application in catalytic reduction of 4-nitrophenol

Silver nanoparticles (Ag NPs) based catalysts are highly attractive for catalytic reactions. In this work, self-supported Ag NPs were successfully synthesized through in situ reduction of AgZr2(PO4)3 (AZP) NASICON-type phosphate using NaBH4 as both a reducing agent (BH4ˉ) and a source of compensator ions (Na+). The growth and self-adhesion of Ag NPs on the AZP surface and the compensation of Ag+ vacancies by Na+ inside the NASICON lattice were confirmed using various characterization techniques. The Ag NPs/Ag1-xNaxZr2(PO4)3 composite was then evaluated by the conversion of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP). The experimental results indicated that the as-fabricated catalyst revealed excellent performance, where ∼99% reduction of 4-NP to 4-AP occurred in just 420 s by using only 2 mg of AZP. Additionally, the catalyst showed long-term stability throughout reuse after 10 consecutive cycles and can be recovered and recycled several times with no appreciable loss of catalytic activity.

Self-supported Ag nanoparticles on AgTi2(PO4)3 for hazardous dyes reduction in industrial wastewater

Silver based-nanoparticles (Ag NPs) have been recently shown to be promising catalysts for the degradation of toxic organic dyes in wastewater despite the challenges of recycling. In this paper, self-supported Ag NPs were obtained at the surface of AgTi2(PO4)3 NASICON-type phosphates through in situ chemical reduction by sodium borohydride (NaBH4). The adopted approach enables the self-growth of zero-valent Ag NPs on the NASICON matrix, and concomitantly leads to the formation of Ag1−xNaxTi2(PO4)3. The crystalline structure, morphology and phase composition of the Ag nanocomposite has been characterized by several techniques. The catalytic performance of the as-fabricated Ag NPs/Ag1−xNaxTi2(PO4)3 has then been verified in the reduction of methylene blue (MB) and methyl orange (MO) dyes, chosen as target pollutants. Our findings reveal a good catalytic activity with an efficiency and time of reaction of respectively ∼ 96.30% and 320 s in the case of the MB reduction and ∼ 94.60% and 270 s in the case of the MO reduction. Additionally, the initial AgTi2(PO4)3 phase can be regenerated via simple calcination route and recycled up to five times with no appreciable loss of catalytic activity.

NASICON-type Li0.5M0.5Ti1.5Fe0.5(PO4)3 (M = Mn, Co, Mg) phosphates as electrode materials for lithium-ion batteries

A correlation between the crystal structure, the ionic conductivity and the electrochemical performance in Lithium-ion batteries was established for a series of NASICON-type phosphates Li0.5M0.5Ti1.5Fe0.5(PO4)3 (M = Mn, Co, Mg). These electrode materials, where the M1 site contains both lithium and the divalent cation M, were prepared using a simple sol-gel process while controlling the pH and the final synthesis temperature. The three phosphates crystallize in the rhombohedral system (S.G. R-3c) with comparable unit cell parameters but with slight difference in the local distortion of the PO4 tetrahedra as confirmed by the Raman study. The ionic conductivities of the Li0.5M0.5Ti1.5Fe0.5(PO4)3 materials were measured at different temperatures using a wide range of frequencies. Mn-based phosphate shows the best features for application as electrode material for Li-ion batteries in term of the conductivity at room temperature and the activation energy of Li+ conduction process. The initial discharge capacity of 100 mAh.g − 1 was obtained for the Mg-based phosphate, 104.3 mAh.g − 1 for the Co-based material while the Mn-based material delivers the best first discharge capacity of 125.3 mAh.g − 1 with the lowest polarization in relation with its better conduction properties. This result was also confirmed by the rate capability tests where Mn-based phosphate shows enhanced electrochemical performance even at fast rate of 5C.

Selective Preparation of Olefins through Conversion of C2 and C3 Alcohols on NASICON-Type Phosphates

Selective Preparation of Olefins through Conversion of C2 and C3 Alcohols on NASICON-Type Phosphates

Nasicon-type phosphates as electrode materials for safe and efficient electrochemical energy storage

Nowadays, our lives have become completely dependent on energy. That is the reason why special attention was focused to the development of clean sustainable energy sources due to the depletion of fossil fuel and its negative impact on the environment. In this regard, many electrochemical storage systems were explored. However, lithium ion batteries are the most effective systems dominating the battery market and used in several applications like cellphones, laptops, digital cameras, etc. The performance of such electrochemical energy storage system strongly depends on the used electrode material. Here we will present our recently obtained results on phosphates as safe and cost-efficient electrode materials for the battery technology.

New Ni0.5 Ti2 (PO4 )3 @C NASICON-type Electrode Material with High Rate Capability Performance for Lithium-Ion Batteries: Synthesis and Electrochemical Properties.

Ni0.5 Ti2 (PO4 )3 /C NASICON-type phosphate is introduced as a new anode material for lithium-ion batteries (LIBs). Ni0.5 Ti2 (PO4 )3 /C was synthesized through the sol-gel route and delivered some remarkable electrochemical performances. Specifically, the Ni0.5 Ti2 (PO4 )3 /C electrode demonstrates a high rate capability performance and delivers high reversible capacities ranging from 130 mAh g-1 to about 111 mAh g-1 at current rates ranging from 0.1 C to 5 C in the voltage window of 1.85-3 V (vs. Li+ /Li). In the same voltage range, the material reaches an initial capacity of 105 mAh g-1 with a capacity retention of about 82 % after 1000 cycles at the high current rate of 10 C. The electrodes are also tested in the wider voltage range of 0.5-3 V (vs. Li+ /Li) and show good reversibility and rate capability performance. Moreover, the Ni0.5 Ti2 (PO4 )3 /C electrodes enable fast Li+ diffusion (in the order of 10-13 cm2 s-1 ) compared with other NASICON-type materials. As a result, a first discharge capacity of 480 mAh g-1 is reached.

Operando Synchrotron X-Ray Diffraction and Mössbauer Spectroscopy of the Cathode Materials for Li-Ion and Na-Ion Batteries

Application of different diffraction and spectroscopic techniques to operando studies on the electrode materials became an integral part of the metal-ion battery research. Combination of novel operando electrochemical cell with sapphire windows [1], synchrotron X-ray diffraction (SXRD) and Mössbauer spectroscopy (MS) has enabled us to study crystal structure evolution and phase transformation behavior during electrochemical cycling of several cathode materials for Li-ion and Na-ion batteries. Two of them are given below. Phase transformations and evolution of the Fe cations environment in LiFePO4, LiFe1/2Mn1/2PO4 and LiFe1/3Mn1/3Co1/3PO4 during Li+ (de)intercalation were studied in operando regime by means of synchrotron SXPD and MS. Presence of a certain amount of Li+ in M2 position in the crystal structure of the initial phosphates leads to appearing of additional component in MS spectra of all studied compounds, corresponding to ferric ions in the same position with distorted second coordination sphere. Evolution of MS spectra during charge/discharge revealed clear connection between relative contribution of this component and the mechanism of Li+ (de)intercalation. Extended single-phase regions with large Li+ non-stoichiometry in triphilite and heterosite phases of Li1-xFePO4 observed by means of SXPD appear due to Li-Fe defects existing in Li-rich olivines and acting as a “diluting” agent preventing two-phase spinodal decomposition. These features can be regarded as an additional merit of Li-rich olivines [2] as a promising cathodes for high-power Li-ion batteries. Unusual phase transformation behavior was also observed for Na4MnV(PO4)3 cathode material with NASICON-type structure by means of operando SXPD. In contrast with other NASICON-type phosphates, Na4MnV(PO4)3↔ Na3MnV(PO4)3 transition proceeds via single phase mechanism. The next step Na3MnV(PO4)3↔ Na2MnV(PO4)3 is biphasic. Further desodiation results in appearance of additional voltage plateau at ~3.9 V vs. Na/Na+, associated with re-distribution of Na atoms over available positions and activation of Na1 site, which previously was considered as inactive. During reverse process, all extracted Na cations are introduced back via continuous solid solution region. The demonstrated behavior is in part similar with Li-ion monoclinic Li3-xV2(PO4)3, where fully deintercalated Li+ cations introduce disorder in the structure which leads to single-phase intercalation mechanism [3]. This work was supported by the Russian Science Foundation (Grant No. 17-73-30006). Reference s : [1] Drozhzhin, O.A., Tereshchenko, I.V., Emerich, H., Antipov, E.V., Abakumov, A.M., Chernyshov, D., J. Synchrotron Rad., (2018) 25 (2), pp. 468-472. [2] K.-Y. Park, I. Park, H. Kim, G. Yoon, H. Gwon, Y. Cho, Y.-S. Yun, J.-J. Kim, S. Lee, D. Ahn, Y. Kim, H. Kim, I. Hwang, W.-S. Yoong, K. Kang, Energy Environ. Sci., 2016,9, 2902-2915 [3] Zakharkin M. V., Drozhzhin O. A., Tereshchenko I. V., Chernyshov D., Abakumov A. M., Antipov E. V., Stevenson K. J., ACS Applied Energy Materials, 1 (2018) pp. 5842-5846. Figure 1

Interfacial Stability of Phosphate-NASICON Solid Electrolytes in Ni-Rich NCM Cathode-Based Solid-State Batteries.

A nondegrading, low-impedance interface between a solid electrolyte and cathode active materials remains a key challenge for the development of functional all-solid-state batteries (ASSBs). The widely employed thiophosphate-based solid electrolytes are not stable toward oxidation and suffer from growing interface resistance and thus rapid fading of capacity in a solid-state battery. In contrast, NASICON-type phosphates such as Li1+ xAl xTi2- x(PO4)3 and Li1+ xAl xGe2- x(PO4)3 are stable at high potentials, but their mechanical rigidity and high grain boundary resistance are thought to impede their application in bulk-type solid-state batteries. In this work, we present a comparative study of a LiNi0.8Co0.1Mn0.1O2 (NCM-811) cathode composite employing either β-Li3PS4 (LPS) or Li1.5Al0.5Ti1.5(PO4)3 (LATP) as a solid electrolyte. LPS is employed as a separator in both cases to assemble a functional ASSB. To avoid high-temperature processing of LATP, along with subsequent detrimental interfacial reactions with NCM materials, the ASSBs are constructed and operated in a hot-press setup at 150 °C. The cathode interfaces are investigated using in situ electrochemical impedance spectroscopy and X-ray photoelectron spectroscopy, which reveals that the interface resistance is strongly suppressed and the chemical state of the composite is unchanged during cycling when employed with LATP. The cell using LATP is reversibly charged and discharged for multiple cycles and outperforms a comparable cell using a thiophosphate composite electrode. The results indicate that LATP in the cathode composite represents an excellent candidate to overcome interfacial challenges in bulk-type solid-state batteries.

Temperature dependent of luminescence and decay behavior of Eu2+ in NASICON-type phosphate CaZr4(PO4)6

The temperature dependence of photoluminescence properties and decay times in the range 10–300K is reported for Eu2+ doped NASICON-type phosphate CaZr4(PO4)6. Luminescence from the Eu2+ impurity has been investigated. Two different Eu2+ centers have been detected in the host structure, 3a and 3b, corresponding to the emission bands peaking at 531 and 480nm. The emission intensity and lifetimes decrease with increasing temperature due to temperature quenching. The values of Stokes shift, quenching temperature T1/2 and activation energy for thermal quenching are evaluated. The mechanism of thermal quenching is also discussed.

Anode Surface Evolution in Aqueous Sodium-Ion Batteries

Aqueous sodium-ion batteries may solve the cost and safety issues associated with the energy storage systems for the fluctuating supply of electricity based on solar and wind power. Compared to their lithium counterparts, aqueous sodium-ion batteries offer multiple advantages including more earth abundant sodium, cheaper electrode materials and electrolyte solutions as well as less costly manufacturing conditions. However, poor overall performance and low electrode utilization (much of the electrode material ends up being electrochemically inactive) are the main barriers implementing them in (micro)grid systems. Here we characterize the surface reactions on NASICON-type phosphate anode material and rationalize their close associations with capacity fading upon slow cycling of aqueous sodium-ion batteries. The surface reactions result in the formation of an electrically insulating surface layer causing the failure of electrochemical performance and the precipitation of surface particles that blocks the pores thereby leading to poor electrode utilization. These findings provide insight into new possibilities of improving the electrochemical performance of aqueous sodium-ion batteries by the design of protective layers through surface modifications that prevent the formation of insulating surface layers and insoluble precipitates.

Catalytic activity of LiZr2(PO4)3 nasicon-type phosphates in ethanol conversion process in conventional and membrane reactors

In this paper synthesis and catalytic properties of new catalysts based on double lithium-zirconium phosphate (LiZr2(PO4)3) with monoclinic NASICON-type structure, doped by indium, niobium and molybdenum are discussed. The obtained samples with particle size of 50–300nm were characterized by X-ray diffraction, scanning electron microscopy and X-ray microanalysis. The synthesized samples exhibit catalytic activity in the dehydration and dehydrogenation reactions of ethanol conversion. The main products were acetaldehyde, diethyl ether, hydrogen, C2- and C4-hydrocarbons. Indium- and molibdenum-doped samples were characterized by high activity in dehydrogenation processes, while niobium-doped was more active in dehydration processes. The highest selectivity in diethyl ether formation was achieved for LiZr2(PO4)3 and Nb-doped samples (90 and 60% at 300°C). The highest hydrogen yield (up to 60%) was obtained with the use of In-doped catalyst. LiZr2(PO4)3 and Mo-doped samples are also noticeable for high C4-hydrocarbons formation, selectivity to which reaches 60% at 390°C. Use of a 100% hydrogen selective palladium-ruthenium alloy membrane increases hydrogen yield by 20%.