Poor Electronic Conductivity Research Articles

Micron-Sized Cobalt Niobium Oxide with Multiscale Porous Sponge-Like Structure Boosting High-Rate and Long-Life Lithium Storage.

Niobium-based oxides show great potential as intercalation-type anodes in lithium-ion batteries due to their relatively high theoretical specific capacity. Nevertheless, their electrochemical properties are unsatisfactorily restricted by the poor electronic conductivity. Here, micron-sized Co0.5Nb24.5O62 with multiscale sponge-like structure is synthesized and demonstrated to be a fast-charging anode material. It can deliver a remarkable capacity of 287 mA h g-1 with a safe average working potential of ≈1.55 V vs Li+/Li and a high initial Coulombic efficiency of 91.1% at 0.1C. Owing to the fast electronic/ionic transport derived from the multiscale porous sponge-like structure, Co0.5Nb24.5O62 exhibits a superior rate capability of 142 mA h g-1 even at 10C. In addition, its maximum volume change during the charge/discharge process is determined to be 9.18%, thus exhibiting excellent cycling stability with 75.3% capacity retention even after 3000 cycles at 10C. The LiFePO4//Co0.5Nb24.5O62 full cells also achieve good rate performance of 101 mA h g-1 at 10C, as well as an excellent cycling performance of 81% capacity retention after 1200 cycles at 5C, further proving the promising application prospect of Co0.5Nb24.5O62.

Cation/Anion-Dual regulation in Na3MnTi(PO4)3 cathode achieves the enhanced electrochemical properties of Sodium-Ion batteries

Na3MnTi(PO4)3 (NMTP) emerges as a promising cathode material with high-performance for sodium-ion batteries (SIBs). Nevertheless, its development has been limited by several challenges, including poor electronic conductivity, the Mn3+ Jahn-Teller effect, and the presence of a Na+/Mn2+ cation mixture. To address these issues, we have developed a cation/anion-dual regulation strategy to activate the redox reactions involving manganese, thereby significantly enhancing the performance of NMTP. This strategy simultaneously enhances the structural dynamics and facilitates rapid ion transport at high rates by inducing the formation of sodium vacancy. The combined effects of these modifications lead to a substantial improvement in specific capacity (79.1 mAh/g), outstanding high-rate capabilities (35.9 mAh/g at 10C), and an ultralong cycle life (only 0.040 % capacity attenuation per cycle over 250 cycles at 1C for Na3.34Mn1.2Ti0.8(PO3.98F0.02)3) when used as a cathode material in SIBs. Furthermore, its performance in full cell demonstrates impressive rate capability (44.4 mAh/g at 5C) and exceptional cycling stability (with only 0.116 % capacity decay per cycle after 150 cycles at 1C), suggesting its potential for practical applications. This work presents a dual regulation strategy targeting different sites, offering a significant advancement in the development of NASICON phosphate cathodes for SIBs.

Rapid mechanochemical synthesis of high-performance Na4Fe2.94Al0.04(PO4)2(P2O7)/C cathode material for sodium-ion storage

Na4Fe3(PO4)2(P2O7) is regarded as a promising cathode material for sodium-ion batteries due to its affordability, non-toxic nature, and excellent structural stability. However, its electrochemical performance is hampered by its poor electronic conductivity. Meanwhile, most of the previous studies utilized spray-drying and sol–gel methods to synthesize Na4Fe3(PO4)2(P2O7), and the large-scale synthesis of the cathode material is still challenging. This study presents a composite cathode material, Na4Fe2.94Al0.04(PO4)2(P2O7)/C, prepared via a straightforward ball-milling technique. By substituting Al3+ minimally into the Fe2+ site of NFPP, Fe defects are introduced into the structure, hindering the formation of NaFePO4 and thereby enhancing Na-ion diffusion kinetics and conductivity. Additionally, the average length of AlO bonds (2.18 Å) is slightly smaller than that of FeO bonds (2.19 Å), contributing to the superior structural stability. The smaller ionic radii of Al3+ induce lattice contraction, further enhancing the structural stability. Moreover, the surface of material particles is coated with a thin layer of carbon, ensuring excellent electrical conductivity and outstanding structure stability. As a result, the Na4Fe2.94Al0.04(PO4)2(P2O7)/C cathode exhibits excellent electrochemical performance, leading to high discharge capacity (128.1 mAh g−1 at 0.2 C), outstanding rate performance (98.1 mAh g−1 at 10 C), and long cycle stability (83.7 % capacity retention after 3000 cycles at 10 C). This study demonstrates a low-cost, ultra-stable, and high-rate cathode material prepared by simple mechanical activation for sodium-ion batteries which has application prospects for large-scale production.

Sandwich-like high-performance Ti3C2Tx MXene/NiCo2O4 nanosphere composites for asymmetric supercapacitor application

NiCo2O4 is a promising electrode material for supercapacitors due to its low cost, high theoretical specific capacitance and good cycling stability. However, NiCo2O4 has the disadvantages of poor electronic and ionic conductivities and easy agglomeration. Moreover, the irreversible structural damage caused by the NiCo2O4 volume expansions during charging and discharging limits its use in supercapacitors. Herein, we fabricated sandwich Ti3C2Tx MXene/NiCo2O4 composites via an electrostatic self-assembly method. The problem of easy agglomeration of the NiCo2O4 nanospheres was solved by intercalating Ti3C2Tx MXene layers with the NiCo2O4 nanospheres. Furthermore, the Ti3C2Tx MXene layer was also utilized as a protective layer to limit serious volume expansion and protect the structure of NiCo2O4 nanospheres from destruction. The results showed that the prepared Ti3C2Tx MXene/NiCo2O4 composite exhibited a high specific capacitance of 1025 F g−1 at a current density of 1 A g−1 and had an initial capacity of 81 % when the current density was increased to 10 A g−1. The Ti3C2Tx MXene/NiCo2O4 composite cathode and activated carbon anode were assembled in an asymmetric supercapacitor, which showed an energy density of 36.67 Wh kg−1 at 800 W kg−1 and a capacity retention of 88.2 % after 5000 cycles.

Ultrafast room-temperature construction of hierarchical hollow rodlike nanoarrays based on amorphous NiFeCo layered double hydroxide toward enhanced oxygen evolution reaction

Designing and constructing non-noble metal electrocatalysts with high catalytic activity for oxygen evolution reaction (OER) is a significant challenge for energy storage and conversion. Transition-metal-based layered double hydroxides (LDHs) are the most efficient OER catalysts. However, their catalytic performance and commercial application are limited by their small electrochemical active areas and poor electronic conductivity. Herein, hollow hierarchical rodlike nanoarrays on nickel foam assembled with amorphous NiFeCo-LDH nanosheets were prepared using a metal–organic framework, ZIF-67, as a sacrificial template by a facile and ultrafast ion-exchanged reaction at room temperature. The as-prepared electrocatalyst possessed a large specific surface area (397 m2/g), unique structure, fast charge transfer and abundant active sites, and thus displayed a superior performance for OER with a low overpotential of 202 mV at 10 mA/cm2, a Tafel slope of 47.9 mV/dec and long-term durability in 1.0 M KOH electrolyte. This research affords a facile strategy to rationally design high activity electrocatalysts of multi-metallic LDHs for OER.

A Comparative Study of the Structural and Electrochemical Properties of Na3V2(PO4)3/C Cathode Materials for Na‐ion Batteries Prepared by Sol‐Gel vs. Solid‐State Methods

AbstractNa‐ion batteries have attracted much attention as one of the most promising alternatives to lithium‐ion batteries. Na3V2(PO4)3 has been widely investigated as a cathode material for Na‐ion batteries because of its high structural and thermal stability, leading to high cycling performance and safety. The cathode material also possesses a three‐dimensional open framework and consequently provides high ionic conductivity, as well as high‐rate capability. However, the cathode type experiences poor electronic conductivity, affecting its electrochemical properties. It is well established that preparation methods have remarkable effects on the crystal structure and morphology of electrode materials, altering their electrochemical performance. Thus, this work focuses on a comparative study of the morphology, structures, electrochemical performance, and kinetic properties of Na3V2(PO4)3/C cathodes prepared by sol‐gel and solid‐state methods, which are simple and scalable. The results reveal that sol‐gel and solid‐state reaction processes provide Na3V2(PO4)3/C cathode materials with different structural and morphological characteristics, significantly affecting their electrochemical performance and kinetic properties. This is a crucial key to finding a proper synthesis method to achieve Na3V2(PO4)3/C with high performance for commercial large‐scale production.

CoP Quantum Dots Embedded in Carbon Polyhedra through Co─P─C Bonding Enabling High‐Energy Lithium‐Ion Capacitors

AbstractPhosphides with high theoretical capacity are considered ideal anode materials for lithium‐ion capacitors (LICs), but poor electronic conductivity as well as unsatisfied cyclic stability limits the performance of the phosphides. Here a covalently bonded CoP@C heterostructure is reported, which consists of 5 nm CoP quantum dots (QDs) like pomegranate seeds pinned in carbon polyhedron through interfacial Co─P─C bonding. The ultrafine size of CoP QDs provides more reactive sites and a shorten electrons/ions diffusion path, boosting the specific capacity. The Co─P─C bond induces the energy band variation of CoP and increases the interfacial charge density, bringing about fast kinetics. Besides, the Co─P─C bond introduces a robust pining effect among CoP QDs and carbon polyhedra, greatly improving the structure stability of 5 nm CoP QDs. The CoP@C heterostructure electrode exhibits high capacity (nearly 1000 mAh g−1) and superior cycling stability. It is worth noting that a prototyped LIC full‐cell of YP80//CoP@C presents an impressive high energy density of 172 Wh kg−1 and a power density of 10.8 kW kg−1. Moreover, the LIC possesses an ultra‐long life, retaining 80% after 20,000 cycles. This study offers an effective design for phosphides achieving fast kinetics and superior structure stability through an interfacial bonding approach.

Electrochemical activity of 3d transition metal ions in polyanionic compounds for sodium‐ion batteries

AbstractSodium‐ion batteries are expected to replace lithium‐ion batteries in large‐scale energy storage systems due to their low cost, wide availability, and high abundance. Polyanionic materials are considered to be the most promising cathode materials for sodium‐ion batteries because of their cycling stability and structural stability. However, limited by its poor electronic conductivity, the electrochemical performance needs to be further improved. This paper reviews the characterization and development of 3d transition metal ions polyanionic compounds, along with the summarized effect of structure and particle size on the performance and improvement of electrochemical properties. Meanwhile, crystal structure modulation, transition metal ion choice, and transition metal ion doping can improve the electrochemical performance and energy density of polyanionic compounds. Finally, this review points out the challenges of polyanionic compounds and puts forward some particular standpoints, contributing to the promising development of polyanionic compounds in the large‐scale energy storage market.

Challenge and Design Strategies of Polymer Organic Electrodes for Lithium‐Ion Batteries

AbstractDue to the scarcity of metallic lithium and the limited specific energy density of traditional inorganic cathodes, the application of lithium‐ion batteries (LIBs) in the large‐scale energy storage market is severely limited. To meet the growing power demands of electric vehicles and electronics, low‐cost and sustainable battery technologies need to be developed. Organic batteries and organic electrode materials emerge at a historic moment and show great potential. Polymer organic materials (POEs) with longer cycle life than small organic molecules that are easily soluble in liquid electrolytes provide more opportunities for advanced electrode materials. However, many issues remain to be addressed before POEs are widely used, such as sluggish electrode reaction kinetics and poor electronic conductivity. Herein, the classification, energy storage mechanism and features of POEs are briefly summarized. Further, the existing problems and design strategies of POEs are discussed and summarized in depth. This review aims to highlight the potential role of structural and morphological design in improving the practical performance of POEs in LIBs and provides insights into the in‐depth understanding and development of organic batteries and organic electrode materials.

Fracture Resistant CrSi2-Doped Silicon Nanoparticle Anodes for Fast-Charge Lithium-Ion Batteries.

Lithium-ion batteries (LIBs) has been developed over the last three decades. Increased amount of silicon (Si) is added into graphite anode to increase the energy density of LIBs. However, the amount of Si is limited, due to its structural instability and poor electronic conductivity so a novel approach is needed to overcome these issues. In this work, the synthesized chromium silicide (CrSi2) doped Si nanoparticle anode material achieves an initial capacity of 1729.3mAhg-1 at 0.2C and retains 1085mAhg-1 after 500cycles. The new anode also shows fast charge capability due to the enhanced electronic conductivity provided by CrSi2 dopant, delivering a capacity of 815.9mAhg-1 at 1C after 1000cycles with a capacity degradation rate of <0.05% per cycle. An in situ transmission electron microscopy is used to study the structural stability of the CrSi2-doped Si, indicating that the high control of CrSi2 dopant prevents the fracture of Si during lithiation and results in long cycle life. Molecular dynamics simulation shows that CrSi2 doping optimizes the crack propagation path and dissipates the fracture energy. In this work a comprehensive information is provided to study the function of metal ion doping in electrode materials.

Effect of Mn Substitution on GeFe2O4 as an Anode for Sodium Ion Batteries

GeFe2O4 (GFO), with its intriguing intercalation mechanism based on alloying–conversion reactions, was recently proposed as an anode material for sodium ion batteries (SIBs). However, drawbacks related to excessive volume expansion during intercalation/deintercalation and poor electronic conductivity enormously hinder its practical application in batteries. In this regard, some experimental strategies such as cation substitutions and proper architectures/carbon coatings can be adopted. In this paper, pure and Mn-doped GFO samples were prepared by hydrothermal synthesis. The doped samples maintained the spinel cubic structure and the morphology of pure GFO. The electrochemical tests of the samples, performed after proper carbon coating, showed the expected redox processes involving both Ge and Fe ions. The Mn doping had a positive effect on the capacity values at a low current density (about 350 mAh/g at C/5 for the Mn 5% doping in comparison to 300 mAh/g for the pure sample). Concerning the cycling stability, the doped samples were able to provide 129 mAh/g (Mn 10%) and 150 mAh/g (Mn 5%) at C/10 after 60 cycles.

Accelerating the electrochemical kinetics of Na3V2(PO4)3 cathode for high-performance sodium ion batteries with superior cycling stability by Cl− substitution

Na3V2(PO4)3 (NVP) has been recognized as one of most prospective cathode materials of sodium-ion batteries (SIBs) due to its excellent thermal stability and high voltage plateau. Nevertheless, its inherent poor electronic conductivity limits its further large-scale applications. Herein, we propose an efficient strategy to improve electrochemical kinetics of Na3V2(PO4)3 cathode by Cl− doping. The incorporation of Cl effectively enhances the electronic transport pathways within the NVP material. Additionally, it introduces supplementary charge carriers, thereby modulating the internal charge balance of the crystal lattice and mitigating electron confinement. Although the as-prepared Na3V2(PO4)2.8Cl0.6 and pristine NVP material show similar discharge capacity at low rate (0.1C), the former delivers higher capacity at high rates (0.2, 0.5, 1, 2, 5, 10, and 20C), indicating excellent rate performance. Notably, even after 2000 cycles at 10C, Na3V2(PO4)2.8Cl0.6 maintains a capacity retention of approximately 70 %. Remarkably, it retains 63 % of its initial capacity (48.1 mAh/g) after 5000 cycles at the demanding 20C, with a Coulombic efficiency approaching 100 %. These findings underscore the efficacy of Cl doping as a means to enhance the electrochemical properties of NVP, providing valuable insights into the designing of high-performance SIBs cathode materials.

In-situ construction of Ti3C2TX/Ni-HHTP heterostructure as anode for lithium-ion batteries

Pursuing anode materials with high specific capacity and long cycle stability is critical for advanced lithium-ion batteries (LIBs). Metal-organic frameworks (MOFs) with high specific surface area, regular pore channels, and multiple active sites are promising anode materials for LIBs. However, the poor electronic conductivity limits their application in LIBs. Thus, introducing some conducting materials is necessary. MXene, known for its excellent electronic conductivity in electrochemical energy storage systems, is an ideal candidate. Herein, a heterostructure composite material (Ti3C2TX/Ni-HHTP) that combines the advantages of both MOFs and MXene has been synthesized via an in-situ growth method, the composite exhibits regular pore channels, enhanced electronic conductivity, and excellent stability. When it is used as an anode material in LIBs, the composite presents satisfying rate performance and cycling stability. The initial discharge capacity of the Ti3C2TX/Ni-HHTP electrode exhibits 424.4 mA h g−1 at 0.5 A g−1 and remains at 390.2 mA h g−1 after 800 cycles with a capacity retention rate of 92.0%. This design strategy provides valuable insights into constructing MOF hybrid materials with enhanced electronic conductivity for various electrochemical applications.

Black-Fe2O3 Polyhedron-Assembled 3D Film Electrode With Enhanced Conductivity and Energy Density for Aqueous Solid-State Energy Storage

Abstract The construction of advanced Fe2O3 materials with high energy density for energy storage faces challenges due to the defects of conventional widely known red-brown Fe2O3 such as poor electronic conductivity and insufficient physical/chemical stability. Unlike previous works, we successfully synthesized a novel black-Fe2O3 (B-Fe2O3) thin film electrode by adopting a simple hydrothermal strategy. Physical characterizations indicate that the as-made B-Fe2O3 product is composed of polyhedrons (mainly exhibit four to eight sides) with a micrometer grade size range. Besides, the Fe-based thin film electrode with this 3D structure has a stronger affinity and high electronic conductivity. As anode of aqueous solid-state energy storage devices, the as-synthesized B-Fe2O3 film electrode exhibits excellent volume energy density of 14.349 kWh m−3 at a power density of 1609 kW m−3, which is much higher than the best result of previous works (∼8 kWh m−3). This study may provide new insights into the development of the Fe2O3 series on developing high-efficiency Fe-based anode materials for solid-state energy storage.

Efficient Structural Regulation Platform for the Controlled Synthesis of LiFePO4 Cathodes with Shorter Li-Ion Diffusion Paths.

The rate performance of lithium iron phosphate (LiFePO4) is mainly limited by its poor electronic conductivity and slow Li-ion diffusion rate. Graphene-based materials are often compounded with LiFePO4 (LFP) to improve their rate performance, mainly because of their excellent electrical conductivity. Unlike most past composite work focusing on the conductive network between LFP and graphene, in this work, we further developed the functionality of graphene-based materials as nanoparticle carriers, where the nitrogen-doping strategy endows graphene with properties that make it an efficient structural regulation platform during the solvothermal process. Compared to reduced graphene oxide, not only does the nitrogen-doped sites confer more nucleation growth sites for LFP on the graphene surface during the solvothermal process, but also the localized formation of an EG-enriched microenvironment helps to further inhibit the in situ growth of LFP along [010]. The efficient structural regulation platform assisted the synthesis of (010)-oriented LFP with a smaller particle size, which further shortens the Li-ion diffusion paths. The optimized LFP composite electrode materials exhibit a discharge-specific capacity of 133.1 mA·h/g at 10C, which exceeds/is comparable to that of previously reported LFP compounded with graphene-based materials. This work broadens the functionality of graphene-based carriers and provides new ideas for the controllable synthesis of nanoparticles.

Interfacial-Confined Isochronous Conversion to Biphasic Selenide Heterostructure with Enhanced Adsorption Behaviors for Robust High-Rate Na-Ion Storage.

Sodium-ion batteries (SIBs) have gradually become one of the most promising energy storage techniques in the current era of post-lithium-ion batteries. For anodes, transitional metal selenides (TMSe) based materials are welcomed choices , owing to relatively higher specific capacities and enriched redox active sites. Nevertheless, current bottlenecks are blamed for their poor intrinsic electronic conductivities, and uncontrollable volume expansion during redox reactions. Given that, an interfacial-confined isochronous conversion strategy is proposed, to prepare orthorhombic/cubic biphasic TMSe heterostructure, namely CuSe/Cu3 VSe4 , through using MXene as the precursor, followed by Cu/Se dual anchorage. As-designed biphasic TMSe heterostructure endows unique hierarchical structure, which contains adequate insertion sites and diffusion spacing for Na ions, besides, the surficial pseudocapacitive storage behaviors can be also proceeded like 2D MXene. By further investigation on electronic structure, the theoretical calculations indicate that biphasic CuSe/Cu3 VSe4 anode exhibits well-enhanced properties, with smaller bandgap and thus greatly improves intrinsic poor conductivities. In addition, the dual redox centers can enhance the electrochemical Na ions storage abilities. As a result, the as-designed biphasic TMSe anode can deliver a reversible specific capacity of 576.8mAhg-1 at 0.1Ag-1 , favorable Na affinity, and reduced diffusion barriers. This work discloses a synchronous solution toward demerits in conductivities and lifespan, which is inspiring for TMSe-based anode development in SIBs systems.

Mo-doped porous Co3O4 nanoflakes as an electrode with the enhanced capacitive contribution for asymmetric supercapacitor application

Cobalt oxide (Co3O4) electrode materials have tremendous properties for supercapacitors, such as being environmentally friendly, having a high surface area, being low cost, and having high theoretical specific capacitance (3560 Fg−1). However, its poor electronic conductivity restricts the performance of the practical application. Doping transition metal ions into the host materials is an effective method to improve conductivity and enhance storage capacity. In this research work, we studied Mo-doped Co3O4 nanostructure electrodes synthesized using the electrodeposition technique. The integrated material samples were characterized by XRD, SEM with EDAX, XPS, FTIR, Raman spectra, UV–visible, and BET for their structure, morphology, composition, optical, and surface area properties. The 2 mM Mo-doped Co3O4 electrode exhibits excellent electrochemical pseudocapacitive properties. The optimized Mo2-doped Co3O4 shows a maximum specific capacitance of 1674 Fg−1 at 10 mA cm−2 current density in 1 M KOH electrolyte solution. Finally, the asymmetrical hybrid supercapacitor device (AsHScD) Mo2-Co3O4//rGO) demonstrates the highest power density of 159.0 KWKg−1 and maximum energy density of 13.80 WhKg−1 with a long-term stability of 95 % up to 2000 cycles. The Mo2-Co3O4 electrode is a promising candidate material for a charge-storage hybrid supercapacitor in an aqueous 1 M KOH electrolyte.

Design strategy for metal–organic framework assembled on modifications of MXene layers for advanced supercapacitor electrodes

The poor electronic conductivity and instability of metal–organic framework (MOFs) nanomaterials have been considered as the main reasons that hinder their practical application. Here, the bimetallic NiCo-MOF is in-situ grown by two-dimension expanded MXene to construct promising hierarchical electrodes. Benefitting from the hydroxyl group on the surface of MXene attracts metal (Ni, Co) ions by weak coordination, leading to oxygen vacancies during NiCo-MOF formation. At the same time, the density functional theory (DFT) calculation displays that the redox active center of NiCo-MOF is guaranteed to possess excellent electron and ion transport performance. Moreover, the open morphology based on expanded MXene by the hard template method can solve the re-stacking problem of MXene and provide a larger growth area for NiCo-MOF. The electrode design engineering strategy significantly improves the capacitance performance by increasing the electrochemically active site and promoting the ion dynamics. Specifically, the integrated solid-state hybrid supercapacitor (HSC) with MXene@NiCo-MOF and activated carbon (AC) exhibits energy density of 40.23 Wh·kg−1 at a power density of 1495.07 W·kg−1 and 84.4 % capacitance retention after 10,000 cycles via adopting this strategy. The strategy also provides a new route to improve the performance of flexible MXene-based supercapacitors with polyvinyl alcohol hydrogel electrolytes.

Heterostructured Co/CeO2-Decorating N-Doped Porous Carbon Nanocubes as Efficient Sulfur Hosts with Enhanced Rate Capability and Cycling Durability toward Room-Temperature Na-S Batteries.

Room-temperature sodium-sulfur (RT Na-S) batteries have gained significant interest thanks to their satisfactory energy density and abundant earth resources. Nevertheless, practical implementations of RT Na-S batteries are still impeded by serious shuttle effects of sodium polysulfide (NaPS) intermediates, sluggish redox kinetics of cathodes, and poor electronic conductivity from S-species. To solve these problems, heterostructured Co/CeO2-decorating N-doped porous carbon nanocubes (Co/CeO2-NPC) are constructed as a S support, which integrates the strong adsorption and fast conversion of NaPSs, together with superior electronic conductivity. Consequently, the as-synthesized S@Co/CeO2-NPC cathode for RT Na-S batteries exhibits improved rate performance (1275, 561.1, and 485 mAh g-1 at 0.1, 5, and 10 C, respectively) and superior cyclic durability (capacity degeneration of 0.027% per cycle after 1000 cycles at 5 C). Such a S cathode combining a heterostructure interface, hierarchical porous carbon nanocubes, and polar compositions can considerably increase electronic conductivity and promote NaPS adsorption and conversion, achieving superior performance toward RT Na-S batteries.

The N-doped carbon coated Na3V2(PO4)3 with different N sources as cathode material for sodium-ion batteries: Experimental and theoretical study

NASICON (super ion conductor)-type Na3V2(PO4)3 (NVP) is considered to be one of the most promising cathode materials for sodium-ion batteries (SIBs) due to its good structural stability, fast Na+ diffusion coefficient, and excellent electrochemical properties. However, the poor intrinsic conductivity and electronic conductivity and severe volume shrinkage of NVP, resulting in serious limitations in the practical application of NVP materials. Carbon, especially N-doped carbon modification, is the most effective method and strategy to improve the conductivity of NVP. The study of N source and N content in carbon plays a very important role in improving the electronic properties. Herein, N-doped carbon coated NVP composites was synthesized via the classical sol-gel method using common, green and inexpensive urea and polyvinylpyrrolidone (PVP) as N sources, respectively. According to EIS tests and GITT tests, N-doped carbon layers with urea as the N source significantly improved the conductivity of the carbon layers and the Na+ diffusion kinetics. The effects of N-doped carbon layers on the electrode kinetics and electrochemical properties of NVP materials were investigated in detail. The optimized U-NC15@NVP composite exhibited a maximum discharge capacity of 114.2 mAh g−1 at 0.2C and 92.1% capacity retention after 400 cycles at 1C. When the optimal U-NC15@NVP electrode was selected to assemble a symmetric full cell, the reversible discharge capacity was 75.0 mAh g−1 after 100 cycles at 1C. The density functional theory (DFT) calculations establish that N-doped carbon can generate lots of active sites and external defects, which is beneficial to reduce the energy bandwidth of the carbon layer and thus improve the conductivity of the carbon layer. Additionally, it can also reduce the Na+ diffusion barrier and improve the adsorption energy for Na+. Experimental tests and theoretical calculations show that N-doped carbon can significantly increase the conductivity of the carbon layer and improve the electrochemical properties of NVP.