Vanadium based NASICON-type cathodes are faced with the exorbitant cost and underdeveloped multi-electrons reaction of V species. In this work, a strategy of increased covalency of the NASICON framework combined with the reversible activation of V4+/V5+ couple is proposed to improve the electrochemical performance together with energy density of V-based cathodes. Making full use of V2+/V3+/V4+/V5+ and Ti3+/Ti4+ redox couples, Na2.5VTi0.5Al0.5(PO4)(3) exhibits admirable electrochemical performance, including a high specific capacity of 160.9 mAh g(-1) at 0.1 C and favorable cycling stability (a capacity retention of 88.3% at 20 C after 1000 cycles). Moreover, this cathode displays outstanding low temperature performance at 0 degrees C with a capacity retention of 89% after 1200 cycles at 5 C. In situ XRD and EIS analysis are conducted to reveal the Na+ storage mechanism. The cathode reveals a lattice volume variation of 2.16% upon cycling, which is responsible for the high structural stability during the extraction and intercalation process of Na+. Applying Na2.5VTi0.5Al0.5(PO4)(3) as both cathode and anode electrode, the symmetric cell is assembled and displays exceptional capacity of 59.8 mAh g(-1) at 20 C. The research provides an effective routine to stimulate the electrochemical potential of V-based electrode materials.

Manganese‐based phosphate cathodes are promising candidates for developing advanced sodium‐ion batteries, primarily driven by their reliable elemental abundance, low toxicity, and desirable cycling performance. However, the cooperative Jahn–Teller effect of Mn 3+ will inevitably lead to structural disorder and irreversible phase transition, thus greatly harming the reversible capacity, rate, and cycling performance. Herein, a stable NASICON‐type Na 3 MnHf(PO 4 ) 3 cathode is demonstrated with a volume variation of 1.9% upon the process of Na + extraction/insertion based on the robust Hf─O bond and symmetrical MnO 6 octahedron. Moreover, making full use of the stepwise redox reactions of Mn 2+ /Mn 3+ /Mn 4+ , this cathode reveals excellent cycling stability with a capacity retention of 85.4% after 2500 cycles at 10 C. Matching with commercial hard carbon anodes, the assembled full cell keeps a capacity retention of 92.1% with the Coulombic efficiency close to 100% after 600 cycles at 1 C. The research promises opportunities for the structural amelioration of manganese‐based phosphate cathodes toward the application in high‐performance sodium‐ion batteries.

Since the discovery of Rochelle salt about a century ago, ferroelectrics have been researched extensively because of their robust responses to the thermal, optical, electrical and mechanical fields. Furthermore, these researches about ferroelectric materials have been progressively extended to more diverse fields because of their unique chemical and physical properties. In this review, the most recent research progress related to the utilization of ferroelectrics in electrochemical storage systems has been summarized. First, the basic knowledge of ferroelectrics is introduced. Second, according to the order from the cathode side, the separator membrane to the anode side, the improved performance, the role of ferroelectric polarization and piezoelectric effect upon the energy storage and conversion process originated from the ferroelectric materials are revealed and discussed. Furthermore, we also offer insight into how future research may more conclusively correlate these improvements with the ferroelectricity/piezoelectricity of the ferroelectric additives. Accordingly, further progress in understanding ferroelectric physics/chemistry is expected to offer more constructive guidance about the research and development of advanced electrochemical energy storage systems.

The solid-state metal battery with solid-state electrolytes has been considered the next generation of energy storage technology owing to its superior safety and high energy density. But, unfavorable ionic conductivity and interfacial problems make it difficult to widely use in practice. In this work, Si3N4 was rationally introduced into the NASICON matrix as a sintering aid, and the influence of Si3N4 on the crystal phase, microstructure, electrochemical and electrical performance of Na3Zr2Si2PO12 (NZSP) ceramic was systematically studied. The results demonstrate that the introduction of Si3N4 can effectively lower the densification sintering temperature of Na3Zr2Si2PO12 electrolyte and enhance the room temperature ionic conductivity of the NZSP to 3.82 × 10−4 S cm−1. In addition, since Si3N4 has a high thermal conductivity and can inhibit the transmission of electrons between the grains of the electrolyte matrix, it will effectively hinder the generation of sodium metal dendrites and relieve the concentration of the heat source. Moreover, owing to the desirable interface compatibility of the Na and NZSP-Si3N4 electrolyte, the Na/NZSP-1150-1%Si3N4/Na symmetric battery exhibits excellent stability, and the electrode/electrolyte interface still maintains good integrity even after long-term cycling. The assembled Na/NZSP-1150-1%Si3N4/Na3.5V0.5Mn0.5Fe0.5Ti0.5(PO4)3 cell manifests an initial specific capacity of 152.5 mA h g−1, together with an initial Coulombic efficiency of 99.8%. Furthermore, after 200 cycles, the battery displays a capacity retention rate of 82%.

All-solid-state batteries have drawn a lot of concern owing to their distinct advantages in energy density and safety. However, the interfacial issues between the solid electrolyte and electrodes are still roadblocks to large scale application of rechargeable solid-state batteries. In this work, it reveals that promoting the Na-O affinity in Na3Zr2Si2PO12 electrolyte can effectively boost its air stability. Specifically, a two-step sintering approach is employed to actively regulate the microstructure evolution of Na3Zr2Si2PO12 electrolyte. Apart from the enhanced strength of the Na-O bond, the mechanical performance and ionic conductivity are also apparently improved in comparison with the traditional one-step sintering. Moreover, a low resistance of 68 Omega cm(2) is achieved with the Na/Na3Zr2Si2PO12 interface, demonstrating long cycling stability of 1000 cycles at 0.1 mA cm(-2). The designed Na3Zr2Si2PO12 ceramic electrolyte paired with Na3.5V0.5Mn0.5Fe0.5Ti0.5(PO4)(3) cathode and metallic Na anode manifests outstanding cycling stability with a high reversible discharge capacity of 136 mAh g(-1) after nearly 400 cycles at 1 C, and 25 degrees C. Therefore, it is believed that the delicate modulation of solid electrolyte microstructure is of great importance for accelerating the application of solid-state batteries.

Polyanionic sodium ion cathodes have attracted lots of concern because of their excellent structural stability. However, the low specific capacity is still a pressing issue hampering their practical application. In this work, a medium-entropy NASICON-structure cathode Na3.5V0.5Mn0.5Fe0.5Ti0.5(PO4)(3) (Me-NVMP) is proposed. The Me-NVMP achieves a highly reversible specific capacity of 165.8 mAh g(-1) (1.8-4.4 V vs Na+/Na) at 0.1 C via the stepwise redox reactions of Ti3+/Ti4+-Fe2+/Fe3+, V3+/V4+-Mn2+/Mn3+, and V4+/V5+-Mn3+/Mn4+. More impressively, the Me-NVMP yields super rate capability and cycling stability via the regulation of configuration entropy in NASICON. Specifically, the Me-NVMP cathode can preserve a capacity retention of 83.5% after 10,000 cycles at 100 C (17 A g(-1)). Furthermore, excellent cycling performance even at the temperature of 0 degrees C (capacity retention of 93.45% at 20 C after 1000 cycles) is also demonstrated. In situ X-ray diffraction analysis reveals that the enhanced performance can be mainly attributed to the solid-solution-type Na+ storage behavior in Me-NVMP. Moreover, issues such as Jahn-Teller distortion of Mn3+ and irreversible structural change at high voltage (>4.0 V vs Na+/Na) are effectively mitigated. This work inspires a new strategy to design high-performance polyanionic electrode materials.

Anode-free solid-state batteries (AFSSBs) are considered one of the promising solutions for achieving high energy density and safety of electrochemical energy storage systems. However, owing to mechanochemical contact losses and metallic dendrite growth caused by the degradation at the current collector (CC)/electrolyte interface, the feasibility of AFSSBs is critically limited, especially upon the involvement of rigid ceramic electrolytes. Here, a new strategy is reported for NASICONstructure Na3Zr2Si2PO12 (NZSP) electrolyte-based AFSSBs by introducing a resilient ferroelectric composite substrate coated onto Al CC, eventually achieving efficient and stable operation. Compared with the bare Al foil, the ferroelectric composite substrate not only renders an intimate CC/electrolyte interface compatibility, but also dynamically regulates the distribution and migration of Na+ flux at the CC/electrolyte interface through the built-in electric field stem from ferroelectric BaTiO3, guiding homogeneous and dense sodium metal deposition. Stable plating/stripping cycling can be achieved even at a high current density of 1.2mA cm-2 with the Coulombic efficiency of (99.7 %). Significantly, the NZSP-based AFSSB integrated with the ferroelectric composite substrate and mainstream sodium ion cathodes demonstrates stable cycling and excellent capacity retention.

Solid‐state metal batteries have displayed great advantages in the domain of electrochemical energy storage owing to their remarkably improved energy density and safety. However, the practical application of solid‐state batteries (SSBs) is still greatly impeded by unfavorable interface stability and terrible low temperature performance. In this work, a local targeting anchor strategy is developed to realize an impressively long cycling life for a NASICON‐based solid‐state sodium metal battery at 0 °C. With the electrochemical migration of K + from the cathode side to the anode side, a spontaneous generated liquid Na–K interphase can stabilize the ceramic electrolyte/metallic Na anode interface, and address the issues of sluggish kinetics at the interface together with metal dendrite deposition. In addition, the capability of K + conduction in NASICON is also theoretically and experimentally validated. Of particular note, a K 2 MnFe(CN) 6 cathode paired with a Na 3 Zr 2 Si 2 PO 12 ceramic electrolyte and metallic Na anode, enable the long‐term cycling and excellent rate capability of all‐solid‐state sodium batteries at 0 °C. Without the purposely designed matrix host for a liquid Na–K interphase, this work opens up a new route for the design of high energy density SSBs.

It is critical for solid-state alkaline metal batteries to solve the issues of large interfacial resistance and poor interfacial stability between the alkaline metal anode and the solid electrolyte. We tune the interface chemistry between Na metal and a NASICON-type solid electrolyte by a facile Cu2+-ion doping method. It is demonstrated that the Cu2+-ion incorporation into Na3Zr2Si2PO12 (NZSP) significantly reduces the interfacial resistance (Rinter ) and boostss the interfacial stability during charge/discharge cyles at room temperature. The optimal Na3.4Zr1.8Cu0.2Si2PO12 (NZSP-0.2Cu) realizes an increased critical current density of 0.5 mA cm-2 and an impressively low Rinter value of 19 Ω cm2 at 25 °C, which is only 1/35 of the undoped one (665 Ω cm2). Moreover, the symmetrical Na|NZSP-0.2Cu|Na cell maintains steady Na plating/stripping cycles for as long as 1450 h under 0.2 mA cm-2, clearly indicating the desired chemical compatibility at the Na metal anode interface. A self-formed dynamically stable Cu3PO4-dominant interphase layer at the Na metal/NZSP-0.2Cu interface is verified to explain for the outstanding interfacial performance. Furthermore, a room-temperature solid-state NaCrO2|NZSP-0.2Cu|Na metal battery is assembled, exhibiting excellent cycling performance at 5 C for 660 cycles with a capacity retention of 86.5% and an overall Coulombic efficiency of 99.5%.

Sodium-ion batteries have attracted extensive concern and research for smart grids and large-scale energy storage systems owing to the low cost and high natural abundance of Na resource. Selecting appropriate electrode materials is beneficial to the development and research of SIBs. Compared with typical NASICON-structure Na3V2(PO4)3, Mn-based NASICON-type cathodes for sodium-ion batteries reveal highly attractive application prospects due to their high earth-abundance and rich valence states of elemental Mn. Besides, the adjustable merit of NASICON structure endows a big family of Mn-based material system with enriched compositions. In this review, Mn-based NASICON-type sodium ion cathodes are briefed to provide a comprehensive overview of their recent advance. The structure, electrochemical reaction mechanism and properties are demonstrated. Moreover, the critical issues happened to lots of Mn-based materials, such as Mn dissolution, Jahn–Teller distortion, the influence of liquid electrolyte, etc., are discussed. At last, perspectives and challenges about the future development of Mn-based NASICON-type cathodes are presented as well. We believe that this review can serve as a reference for preparing Mn-based NASICONs toward the utilization of both nonaqueous and aqueous rechargeable devices beyond sodium ion batteries.

Abstract Achieving satisfactory performance for a solid‐state Na‐metal battery (SSNMB) with an inorganic solid electrolyte (SE), especially under freezing temperatures, poses a challenge for stabilizing a Na‐metal anode. Herein, this challenge is addressed by utilizing a Natrium super ionic conductor (NASICON) NASICON‐type solid electrolyte, enabling the operation of a rechargeable SSNMB over a wide temperature range from −20 to 45 °C. The interfacial resistance at the Na metal/SE interface is only 0.4 Ω cm2 at 45 °C and remains below 110 Ω cm2 even at −20 °C. Remarkably, long‐term Na‐metal plating/stripping cycles lasting over 2000 h at −20 °C are achieved with minimal polarization voltages at 0.1 mA cm−2. Further analysis reveals the formation of a uniform Na3−xCaxPO4 interphase layer at the interface, which significantly contributes to the exceptional interfacial performance observed. By employing a Na3V1.5Al0.5(PO4)3 cathode, the full battery system demonstrates excellent adaptability to low temperatures, exhibiting a capacity of 80 mA h g−1 at −20 °C over 50 cycles and retaining a capacity of 108 mAh g−1 (88.5% of the capacity at 45 °C) at 0 °C over 275 cycles. This research significantly reduces the temperature threshold for SSNMB operation and paves the way toward solid‐state batteries suitable for all‐season applications.

NASICON‐type Na 3 VM(PO 4 ) 3 (M: transition metals) cathodes usually suffer from poor cycling stability in the voltage region of above 4 V versus Na + /Na owing to irreversible phase transition and severe structural distortion. Herein, the high entropy concept is extended to NASICONs and Na 3 VAl 0.2 Cr 0.2 Fe 0.2 In 0.2 Ga 0.2 (PO 4 ) 3 (NVMP) with high purity is obtained. The NVMP achieves a highly reversible specific capacity of 102 mAh g −1 (2.5–4.4 V vs Na + /Na) via the successive redox reaction of V 3+ /V 4+ /V 5+ together with a long‐term lifespan of 5000 cycles at 20 C (a capacity retention of 86.8%). Even at an extreme temperature of −20 °C, the NVMP cathode can still provide excellent cycling performance (a capacity retention of 94.2% at 5 C after 1000 cycles). Moreover, the increased configurational entropy in the electrode renders a quite small cell volume change of 1.1%. The sodium ion storage mechanism containing solid solution‐type in the voltage range of 2.5–3.8 V and bi‐phasic in 3.8–4.4 V is revealed by ex situ XRD analysis. Pairing with a hard carbon anode, NVMP//HC cell offers a specific capacity of 81 mAh g −1 at 0.2 C based on the cathode mass. This high‐entropy engineering is expected to be widely applicable for the development of polyanionic electrode materials.

The development of solid-state batteries based on NASICON-type Na3Zr2Si2PO12 (NZSP) ceramic electrolytes is critically hampered by their unfavorable room temperature ionic conductivity. Moreover, the inadvertent appearance of ionic insulator ZrO2 phase within NZSP matrix constantly bothers these relevant researches. In this work, via utilizing different kinds of starting materials, it is found that the kinds of Zr source and sintering temperature can regularly affect the relative content of ZrO2 in the NASICON matrix. More significantly, it re-veals that there is no direct correlation between the ZrO2 content and the room temperature ionic conductivity of NZSP. Moreover, NZSP obtained at 1150 degrees C via solid-state reaction with Na2CO3, ZrO2, SiO2, and NH4H2PO4 as starting materials can achieve a room temperature conductivity of 9.1 x 10-4 S cm-1, which is a relatively high value. The work here offers a thorough understanding of the origin of ZrO2 phase in NASICON as well as guidance for the mass production of NASICON-type ceramic electrolytes via conventional solid-sate reaction.

The NASICON-type Na3V2(PO4)3 cathode based on vanadium multiple redox is particularly attractive for largescale sodium-ion battery application. In this work, it was found that the reversible redox of V4+/V5+ can be activated by replacing a part of V3+ with Al3+, obtaining Na3V1.5Al0.5(PO4)3 with typical NASICON phase structure and offering a reversible specific capacity of 163 mAh g-1 through a three-electron redox reaction with a small volume change (2.62%). The most surprising thing is that in addition to favorable room temperature electrochemical performance, Na3V1.5Al0.5(PO4)3 also exhibits a superior low temperature (-20 degrees C) cycling stability with a capacity retention of 98.9% after 1000 cycles at 5 C. Thin and conformal CEI film as well as stable phase structure across a broad temperature range are responsible for this superior electrochemical property. A Na+ storage mechanism consisting of two-phase and solid-solution electrochemical reactions for Na3V1.5Al0.5(PO4)3 cathode is elucidated via ex-situ XRD structural analysis. DFT calculations indicate that Al3+ substitution could manipulate the localized electronic state and strengthen the oxygen ligand skeleton in the NASICON matrix. Hence, the Na3V1.5Al0.5(PO4)3 cathode renders a slight lattice variation upon the repeated desodiation and sodiation and enhanced Na+ diffusion rate along with low charge transfer resistance.

We propose grain boundary sealed Na 3 Zr 2 Si 2 PO 12 (GBS-NZSP) to address the critical issues of solid-state Na batteries. Ultra-stable Na plating/striping cycles and high-rate solid-state Na metal batteries are realized at room temperature.

The variable components and relatively high Na+ intercalation voltage makes sodium ion superconductors (NASICON) as ideal cathode materials for secondary sodium-ion batteries. Na3V2(PO4)(3), as one of the most typical NASICON-type cathode, needs urgent improvement to enable its wide application. Based on charge balance theory, via utilizing Al(3+)and SiO44- to replace V3+ and PO43- in Na3V2(PO4)(3)Na3V2(PO4)(3), respectively, Na3+xV1.5Al0.5(PO4)(3-x)(SiO4)(x) (0 <= x <= 0.5) cathode materials were prepared in this work. In comparison with the initial state, the operation potential was apparently promoted because of the reversible access of V4+/V5+ redox couple at 4.0 V vs. Na+/Na; the higher specific capacity can be achieved owing to much more conductive Na+ involved in the redox reaction of V species. Furthermore, the structural stability and diffusion kinetics is dramatically enhanced, which are further validated by ex-situ XRD and GITT analysis. Specifically, Na3.3V1.5Al0.5(PO4)(2.7)(SiO4)(0.3) can offer highly reversible capacities of 127.3 and 181.5 mAh g(-1) within the region of 2.5-4.4 V and 1.4-4.4 V, respectively, making itself a promising sodium ion cathode material. Na-ion full cells paired with Na3.3V1.5Al0.5(PO4)(2.7)(SiO4) (0.3) cathode and hard carbon anode are assembled, rendering a specific capacity of 154.3 mAh g(-1) at 0.5 C based on the mass of cathode.

High entropy materials are attracting ever-increasing concern on account of their unique structure and un-precedented potential application in various fields. In this letter, a high entropy (Cr0.2Mn0.2Fe0.2Co0.2Ni0.2)(3)O-4 (S-HEO) with Fd3m spinel structure, is prepared by solid-state reaction. Importantly, without the presence of entropy stabilization behavior, single spinel-structure of S-HEO can be retained through the re-heat treatment process. Benefiting from abundant electroactive species and various chemical valance, excellent Li+ storage capability and favorable performance toward oxygen evolution reaction (OER) are achieved with S-HEO. As anode material for Li ion batteries, S-HEO presents a high specific capacity of 560 mAh g(-1) at 100 mA g(-1) and superior capacity retention of 100% after 5000 cycles. In-situ EIS, ex-situ TEM and XRD analysis were conducted to probe insight into the diffusion kinetic and structural evolution of S-HEO upon cycling. Efficient water oxidation with an overpotential of 332 mV to reach 10 mA cm(-2) are achieved with S-HEO. With comparison to spinel-type moderate entropy oxides (S-MEOs), the synergic effect between five species highlight the merits of high-entropy feature, manifesting a better OER kinetic and higher stability in KOH solution. This research demonstrates the significant importance of high-entropy concept to boost the performance of high entropy materials for electrochemical application.

Developing bifunctional oxygen catalysts with high efficiency and low cost to replace platinum-group metal catalysts commonly utilized in metal-air batteries is critically desired. In this article, a convenient method to synthesis NiFe nanoparticles hybridized with N-doped carbon nanotube (NiFe@N-CNTs) is reported. Electrocatalytic performance analysis indicates that NixFe1−x@N-CNTs offers favorable oxygen reduction reaction (ORR) kinetics (onset potential (Eonset) is 0.87 V and half-wave potential (E1/2) is 0.84 V), together with excellent oxygen evolution reaction (OER) performance (an overpotential of 270 mV to drive 10 mA·cm−2). Contributed by the synergetic effect between NiFe alloy and N-CNTs, when being utilized as air cathode, rechargeable Zn-air batteries present superior cycling stability for over 150 h. This research provides a universal strategy to synthesize the hybrids of intertwined carbon nanotube matrix loaded with alloy nanoparticles.

Solid-state metal batteries are attracting unprecedented concern because of their high energy density and safety. However, their service life, especially at high specific density, is hindered by the undesirable reversibility of metal anodes, owing to the inhomogeneous ion distribution and awkward charge transfer dynamics at the electrode/electrolyte interface. In this work, it is well demonstrated that ferroelectric phase BaTiO3 reinforced Na3Zr2Si2PO12 ceramic electrolyte can deconcentrate the distribution of charge transfer and self-accelerate Na+ migration at the Na/Na3Zr2Si2PO12 interface upon cycling, realizing a compact Na deposition morphology together with a high critical current density (1.05 mA cm(-2) at ambient conditions). Assembled symmetric cells based on the proposed composite electrolyte render stable cycling up to 1000 h at 0.3 mA cm(-2). Specifically, the all solid-state sodium metal batteries paired with Na3V1.5Cr0.5(PO4)(3) cathode material can deliver a capacity of 95 mAh g(-1) at 100 mA g(-1) and maintain 84.4% of the initial capacity after 400 cycles. This excellent electrochemical performance clearly confirm the feasibility of the introduction of ferroelectric BaTiO3 to suppress the dendrite nucleation and Na propagation within ceramic electrolyte. This research offers new insight into the rational design of inorganic electrolyte, revealing dendrite-free and long-term all-solid-state sodium batteries.

Solid-state alkaline metal batteries are highly sought out for their improved energy density and security over the current lithium-ion batteries. However, their practical application is heavily hindered by the interfacial issues originating from the solid electrolyte/electrode mismatch. This work demonstrates that a CuO coating layer as an active interphase can thoroughly promote the intimate contact between a Na3Zr2Si2PO12 solid electrolyte and a Na metal anode through an in situ conversion reaction. The resultant Cu/Na2O matrix forms a mixed electron/ion conducting scaffold, which facilitates stable and homogeneous Na metal plating without dendrite formation. Moreover, the symmetric Na metal cell realizes impressively steady plating/stripping cycles for 5000 h even under a high current density of 0.3 mA cm(-2). The novelty is further manifested as a room-temperature solid-state Na metal full battery of Na3V1.5Al0.5(PO4)(3)|CuO@NZSPO|Na is assembled and exhibits a highly reversible cyclability (99.85% coulombic efficiency and 99.0% capacity retention) under a charge/discharge rate of 5 C for 2250 cycles. This work effectively solves the interfacial issues at the Na metal/solid electrolyte interface and provides a convenient way toward high-performance solid-state Na metal batteries operated at room temperature.