Intrinsic Electronic Conductivity Research Articles

Improved cycle stability and high-rate capability of LiNbO3-coated Li3VO4 as anode material for lithium-ion battery

Lithium vanadate (Li3VO4) has garnered considerable attention as an alternative negative electrode material for non-aqueous lithium-ion batteries due to its high capacity, energy efficiency, and stable discharge voltage. Nonetheless, the Li3VO4 material displays a low rate capability, attributed mainly to its poor intrinsic electronic conductivity. Here, we report the synthesis of lithium niobate LiNbO3-coated Li3VO4 (LVO@LNO) using a one-pot sol-gel method. The resulting LVO@LNO demonstrates a high reversible capacity of approximately 530 mAh/g, which is more than double that of free Li3VO4. To explore the effect of the LNO coating process on the morphological and structural properties, Raman, XRD, operando XRD, XPS, SEM and HTEM analyses were conducted. To explain the enhancement of electronic conductivity in our modified material after a LiNbO3 coating, we conducted an Ex-Situ electrochemical impedance (EIS) and Density Functional Theory (DFT) computational study. Additionally, we designed a full cell utilizing a 1 wt% LNO-coated LVO anode and NMC-811 cathode. The cell yielded an output voltage of approximately 2.8 V with a high initial specific capacity of 350 mAh/g versus to the anode, at 1C with a capacity retention of 85 % after 100 cycles.

Engineering Nano-Sized Silicon Anodes with Conductive Networks toward a High Average Coulombic Efficiency of 90.2% via Plasma-Assisted Milling.

Si-based anode is considered one of the ideal anodes for high energy density lithium-ion batteries due to its high theoretical capacity of 4200 mAh g-1. To accelerate the commercial progress of Si material, the multi-issue of extreme volume expansion and low intrinsic electronic conductivity needs to be settled. Herein, a series of nano-sized Si particles with conductive networks are synthesized via the dielectric barrier discharge plasma (DBDP) assisted milling. The p-milling method can effectively refine the particle sizes of pristine Si without destroying its crystal structure, resulting in large Brunauer-Emmett-Teller (BET) values with more active sites for Li+ ions. Due to their unique structure and flexibility, CNTs can be uniformly distributed among the Si particles and the prepared Si electrodes exhibit better structural stability during the continuous lithiation/de-lithiation process. Moreover, the CNT network accelerates the transport of ions and electrons in the Si particles. As a result, the nano-sized Si anodes with CNTs conductive network can deliver an extremely high average initial Coulombic efficiency (ICE) reach of 90.2% with enhanced cyclic property and rate capability. The C-PMSi-50:1 anode presents 615 mAh g-1 after 100 cycles and 979 mAh g-1 under the current density of 5 A g-1. Moreover, the manufactured Si||LiNi0.8Co0.1Mn0.1O2 pouch cell maintains a high ICE of >85%. This work may supply a new insight for designing the nano-sized Si and further promoting its commercial applications.

In situ nitrogen-doped into MnO2/carbon derived from manganese (II) – triazole framework to achieve superior zinc ions storage

The widespread application of MnO2 as cathodes for aqueous zinc ions batteries (AZIBs) suffers from challenging issues of inferior ion storage capability, poor intrinsic electronic conduction and undesirable Mn dissolution. Herein, we demonstrate that the nitrogen can be successfully in situ doped into both the MnO2 and carbon lattice to form N-doped MnO2/C (NMC) by pyrolyzing the Mn based metal-triazole (Mn-MET) framework. The generation of oxygen vacancies in MnO2 and the presence of N-doped carbon in the composite not only increase the electronic conductivity to accelerate charges transfer in MnO2, but also relieve the Mn dissolution to stabilize the MnO2 structure. As a result, the NMC cathode based AZIB is able to display high discharge capacity of 339.3 mAh g−1, much higher than the bare Mn2O3 cathode (147.8 mAh g−1). The excellent long-term cycling life with a capacity retention of 82.8 % can be also achieved after 1000 cycles under 3 A g−1. The energy storage mechanism of the NMC cathode related to the reversible H+ and Zn2+ interaction/extraction are systematically investigated through multiple ex situ characterizations. Thus, these inspiring results in our work are expected to stimulate the exploitation of MOFs derived cathode materials for high-performance AZIBs.

Insight into the Critical Role of Oxygen Vacancies and V=O Bonds Length in V2O5 for Advanced Zinc Ion Storage.

Due to the larger sizes and stronger positive polarity of Zn2+ than dominant univalent ions, Zn2+ sluggish diffusion within V2O5 host electrodes is an essential issue in developing aqueous zinc-ion batteries (ZIBs) of higher energy densities. Herein, a high-performance V2O5 cathode was developed through subtly synthesizing and tuning V2O5 with oxygen vacancies-enriched and elongated apical V=O1 bond by altering the gradient concentration of hydrazine hydrate in the gas-solid reaction system. This strategy can enhance both intrinsic and extrinsic conductivity to a large extent. The electrochemical testing demonstrated the oxygen vacancies-enriched and elongated apical V=O1 bond can not only increase the intrinsic electronic conductivity of V2O5, but also induce additional pseudocapacitance to enhance the Zn2+ diffusion kinetics. We used infrared spectroscopy and Raman spectroscopy to characterize the change in the bond length structure of V2O5. Simultaneously, the long-term cyclability (capacity retention of 76.9 % after 1200 cycles at 4.0 A g-1) and rate capabilities (218 mAh g-1 at 4.0 A g-1) are promoted as well. We believe that our work might shed light on the bond length engineering of V2O5 and provide insights for the reasonable designing of novel cathodes for practical rechargeable ZIBs.

Enhancing reversible Na-ion intercalation by introducing K-ions into layered vanadyl phosphate for sodium-ion battery cathodes

Vanadium-based phosphates are being extensively studied as an important family of sodium-ion battery (SIB) cathodes. Among many compositions, NaVOPO4 is considered because of various polymorphs and the high redox potential of V4+/5+. However, due to relatively poor intrinsic kinetics and electronic conductivity, approaches such as nanostructuring and carbon composites are commonly used to avoid fast performance degradation. Being different from mainstream approaches, this work utilizes the knowledge gained from potassium-ion batteries (PIBs) and applies layered KVOPO4, a PIB cathode material, as a SIB cathode material. The results demonstrate that KVOPO4 experiences an electrochemical K+-Na+ exchange during the initial cycle and a Na-dominated (de)intercalation process in the following cycles. The initial exchange results in a small amount of K+ (∼0.1 K per formula) remaining in the interlayer space and owing to the larger size of K+ than Na+, the residual K+ effectively acts as ‘pillars’ to expand interlayer spacing and facilitates the Na (de)intercalation, leading to enhanced reversible Na storage and diffusion kinetics of KVOPO4 compared to its Na counterpart NaVOPO4. KVOPO4 delivers an initial discharge capacity of 120 mAh g−1 (90% of the theoretical capacity) at 10 mA g−1 and retains 88% capacity after 150 cycles. It also delivers 52 mAh g−1 at 1 A g−1 and 91% capacity retention after 1000 cycles at 100 mA g−1, completely outperforming NaVOPO4.

Carbon coated Na3+xV2-xCux(PO4)3@C cathode for high-performance sodium ion batteries

Na3V2(PO4)3 is considered as one of the most promising cathodes for sodium ion batteries owing to its fast Na+ diffusion, good structural stability and high working potential. However, its practical application is limited by its low intrinsic electronic conductivity. Herein, a carbon coated Cu2+-doped Na3V2(PO4)3 cathode was prepared. The carbon coating not only improve its apparent conductivity, but also inhibit crystal growth and prevent agglomeration of particles. Moreover, Cu2+ doping contributes to an enhanced intrinsic conductivity and decreased Na+ diffusion energy barrier, remarkably boosting its charge transfer kinetics. Based on the structure characterizations, electrochemical performances tests, charge transfer kinetics analyses and theoretical calculations, it’s proved that such an elaborate design ensures the excellent rate performances (116.9 mA h g−1 at 0.1C; 92.6 mA h g−1 at 10C) and distinguished cycling lifespan (95.8 % retention after 300 cycles at 1C; 84.8 % retention after 3300 cycles at 10C). Besides, a two-phase reaction mechanism is also confirmed via in-situ XRD. This research is expected to promote the development of Na3V2(PO4)3-based sodium ion batteries with high energy/power density and excellent cycling lifespan

Ultra‐Long Lifespan Ni Based Porphyrin Complex Cathode for Organic Alkali Metal Batteries

AbstractThe high solubility and low intrinsic electronic conductivity are the key challenges for application of organic materials in electrochemical energy storage. Herein, a functionalized porphyrin complex of [5,15‐Bis(ethynyl)‐10,20‐diphenylporphinato]nickel(II) (NiDEPP) is proposed as new cathode material for alkali metal ion batteries. Owing to the in‐situ electropolymerization, NiDEPP became extremely stable after initial cycling. Therefore, the NiDEPP electrode delivers remarkable reversible capacity of 153 mAh g−1 at 1 A g−1, a high specific energy density of 459 Wh kg−1 and extremely stable cyclability for 4000 cycles with negligible capacity decay in organic lithium batteries. It can further be cycled upto 10000 cycles. Due to the bipolar capability of porphyrin ring, this cathode can also be extended in both sodium and potassium based organic cells. Similar charge storage mechanism enables highly reversible capacity and long‐term cycling stability. This study would open a pathway toward new organic electrodes with long cycling life and high energy densities for renewable charge storage devices.

Highly Conductive PEDOT:PSS Aerogels

AbstractPoly(3,4‐ethylenedioxythiophene):poly(4‐styrenesulfonate) (PEDOT:PSS) aerogel has attracted much attention in bioelectronics, electromagnetic shielding, and energy‐related systems due to its biocompatibility, intrinsic electronic conductivity, and favorable processability. However, fabrication of highly conductive and low‐density PEDOT:PSS aerogels is still challenging. In this work, highly conductive PEDOT:PSS aerogels are produced via ice‐templated pre‐assembly followed by a specially designed thawing process in H2SO4 solution. Upon optimization of heat and mass transfer during the thawing process, along with the unique ice template effect, the microstructure and thin walls of PEDOT:PSS frozen samples are well preserved. Importantly, the porous structure and thin walls facilitate diffusion of H2SO4 into polymer matrix, inducing phase separation of PEDOT:PSS, thus increasing PEDOT crystallinity and partially removing of PSS component. As a result, the as‐prepared pristine PEDOT:PSS aerogels exhibit a high electrical conductivity of 1200 ± 231 S m−1 along the freezing direction at a low density of 15.3 ± 1.5 mg cm−3, enhanced mechanical properties, and a competitive electromagnetic interference shielding efficiency of 25 115 dB cm2 g−1. Moreover, the compressed aerogels show good performances as active materials in symmetrical supercapacitors with thickness‐independent capacitance (maximum 2.1 F cm−2 at 1.0 mA cm−2) and in current collector‐free micro‐supercapacitors processed by laser carving.

P/s-orbital hybridization induced by Mg-doping to active Na sites in Na2FePO4F cathode for long-life and high-rate sodium-ion batteries

The iron-based fluorophosphate Na2FePO4F (NFPF) is considered as a potential cathode for sodium-ion batteries due to the low-cost, non-toxicity and appropriate working voltage. However, the inferior intrinsic electronic conductivity and the restrained active Na sites bring the limits for full realization of electrochemical properties. Herein, Mg2+ with d0 orbital was introduced in FeO4F2 structure, aimed at activating the Na+ at Na1 site and enhancing the electronic conductivity. Different from the 3d transition metal (TM) elements that form 3d-O2p orbital interactions in the FeO4F2 structure, the Mg with d° contributes p and s orbitals mainly in Mg-O bonds, which corresponds to more stable orbital interaction and lattice structure. The electron distribution of bridge O due to the Mg-doping leads to the wooden barrel effect near the Mg site, thus activating Na+ at Na1 site by lowering the energy barrier of Na+ migration from Na1 to Na2 site. Hence, the obtained NFMPF electrode delivers high specific capacity (121.4 vs. 108.7 mAh g−1 at 0.1 C) and better cycling stability (73.8% vs. 54.2 % after 1000 cycles at 20 C). Overall, regulating the electronic structure and activating Na+ at inactive site is the key to break the bottleneck of low activity, which can be an effective strategy to design cathode materials with excellent electrochemical performance.

Improved relaxor ferroelectrics and energy storage performance of polycrystalline Ba0.95Sr0.05Ti2O5 ceramics modified with La dopants

Lead-free relaxor ferroelectrics are useful in energy storage applications. In particular, BaTi2O5-based dielectric materials may have great potential for such applications. In this study, polycrystalline Ba0.95Sr0.05Ti2O5-xLa (BST2-xLa) ceramics were synthesized using a standard solid-state reaction method with as-prepared nanoparticles prepared via a modified Pechini polymeric precursor method. The structural and electrical properties of the BST2-xLa ceramics were systematically investigated using a series of measurements. The phase analysis results confirm that La3+ is a donor dopant that replaced Ba2+ sites in the structure, which results in a decrease in oxygen vacancies to maintain charge neutrality. The intrinsic electronic conduction mechanism for electrical conductivity was evaluated from the fitted activation energy based on the Arrhenius equation. The relaxor ferroelectric behaviour and energy storage density and efficiency are improved by the addition of a small amount of lanthanum (<3.6 mol%) because of the charge and ionic radius mismatch in the structure. These results suggest that lanthanum can effectively optimise the relaxor ferroelectrics of BST2-xLa ceramics, which have promising potential as energy storage materials.

Ultrafast Carbothermal Shock Synthesis of Wadsley–Roth Phase Niobium‐Based Oxides for Fast‐Charging Lithium‐Ion Batteries

AbstractWadsley–Roth phase niobium‐based oxides show potential as anode candidates for fast‐charging lithium‐ion batteries. Traditional synthesis methods, however, usually involve a time‐consuming calcination process, resulting in poor production efficiency. Herein, a novel carbothermal shock (CTS) method that enables the ultra‐fast synthesis of various Wadsley–Roth phase Nb‐based oxides within seconds is introduced. The extremely rapid heating rates enabled by CTS alter the reaction mechanism from a sluggish solid‐state process to a swift liquid‐phase assisted one and drive the chemical reactions away from equilibrium, thereby generating abundant oxygen vacancies and dislocations. Theoretical calculations reveal that oxygen vacancies significantly lower the energy barrier for Li+ diffusion and enhance the intrinsic electronic conductivity. Moreover, dislocations help convert the surface tensile stress arising from Li+ intercalation into compressive stress, effectively improving the structural integrity during cycling. Notably, this approach can also be applied to synthesize LiFePO4 cathode materials under ambient conditions, eliminating the requirement for inert atmospheres. Consequently, the CTS‐synthesized Nb14W3O44||LiFePO4 battery demonstrates reversible structural evolution validated by in situ XRD and exceptional cycling ability (e.g., 0.0065% capacity decay per cycle at 4 A g−1 over 3000 cycles). Importantly, the Nb14W3O44||LiFePO4 configuration also shows enhanced thermal stability in the Ah‐level pouch cell nail penetration test, confirming its feasibility.

Phosphorus-doped TiO2 mesoporous nanocrystals for anodes in high-current-rate lithium ion batteries

Limited by the intrinsic low electronic conductivity and inferior electrode kinetics, the use of TiO2 as an anode material for lithium ion batteries (LIBs) is hampered. Nanoscale surface-engineering strategies of morphology control and particle size reduction have been devoted to increase the lithium storage performances. It is found that the ultrafine nanocrystal with mesoporous framework plays a crucial role in achieving the excellent electrochemical performances due to the surface area effect. Herein, a promising anode material for LIBs consisting of phosphorus-doped TiO2 mesoporous nanocrystals (P-TMC) with ultrafine size of 2–8 nm and high specific surface area (234.164 m2 g–1) has been synthesized. It is formed through a hydrothermal process and NaBH4 assisted heat treatment for anatase defective TiO2 (TiO2–x) formation followed by a simple gas phosphorylation process in a low-cost reactor for P-doping. Due to the merits of the large specific surface area for providing more reaction sites for Li+ ions to increase the storage capacity and the presence of oxygen vacancies and P-doping for enhancing material’s electronic conductivity and diffusion coefficient of ions, the as-designed P-TMC can display improved electrochemical properties. As a LIB anode, it can deliver a high reversible discharge capacity of 187 mAh g–1 at 0.2 C and a good long cycling performance with ∼82.6% capacity retention (101 mAh g–1) after 2500 cycles at 10 C with an average capacity loss of only 0.007% per cycle. Impressively, even the current rate increases to 100 times of the original rate, a satisfactory capacity of 104 mAh g−1 can be delivered, displaying good rate capacity. These results suggest the P-TMC a viable choice for application as an anode material in LIB applications. Also, the strategy in this work can be easily extended to the design of other high-performance electrode materials with P-doping for energy storage.

Rational construction of ultrathin PtPdRhCuM (M=Mn, Co or Ni) high entropy alloy nanotubes with rich defects for enhanced electrochemical activity: Electrochemical aldicarb sulfone sensing

Tremendous efforts have been put into exploring high-entropy alloys (HEAs) for electrocatalysis, which is considered to be a pivotal cornerstone for electrochemical energy conversion. Nevertheless, HEAs have not been employed for electrochemical biosensing and the precise construction of low-dimensional architectures for HEAs is still challenging. Herein, ultrathin quinary PtPdRhCuM (M= Mn, Co or Ni) HEA nanotubes (NTs) with noticeable lattice distortion as well as rich defect sites were controllably synthesized by a template-triggered strategy combining galvanic exchange process, co-reduction pathway and the dealloying technology. Owing to the diversity of composition, high mixing entropy, intrinsic electronic conductivity, and complexity of surface structure, the PtPdRhCuM (M= Mn, Co or Ni) HEA exhibits remarkable physicochemical property and serves as an ultrasensitive sensing layer for the determination of aldicarb sulfone. The acetylcholinesterase (AChE)-Nafion/PtPdRhCuMn HEA NTs-based biosensor possessed a wide detection range of 0.45 pM – 45 nM with a low detection limit of 86.5 fM for aldicarb sulfone. Moreover, the established biosensor was applicable to pesticides in real food samples (apple and cucumber) with excellent recoveries (99.87 − 101.49% and 97.95 − 104.56%). This work forms the foundation for employing HEAs as electrode material for widespread applications such as electrochemical aldicarb sulfone sensing.

Bimetal‐Substituted Polyanion Cathode for Sodium‐Ion Batteries: Less Vanadium and Boosted Low‐Temperature Kinetics

Sodium‐ion batteries (SIBs) have emerged as an attractive alternative for large‐scale energy storage due to their low cost and high safety. The selection of cathode materials, which determine SIB performance, becomes a crucial aspect. Vanadium‐based phosphates are known for their multielectron transfer properties and stable structure, but their intrinsic electronic conductivity is limited. In this regard, bimetallic substitution is an excellent modification method for improving the conductivity property. Herein, a novel Na4VMn0.7Ni0.3(PO4)3@C (NVMNP@C) cathode with less vanadium is designed for SIBs, which exhibits outstanding electrochemical performance at 25 °C, delivering rate capacity of 67 mA h g−1 at 3 A g−1, and long‐term cyclability of remaining 74.6% after 4800 cycles at 2 A g−1. Furthermore, excellent low‐temperature adaptability (82 mA h g−1 at 20 mA g−1, 60 mA h g−1 at 400 mA g−1, and 90.4% capacity retention after 230 cycles at 100 mA g−1) at −40 °C is also achieved. This unique work has broken a feasible pathway for high‐performance SIB cathode at low temperature.

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.

Impact of composite modes on electrochemical properties of Fe3O4/CNTs for Li-ion storage

Transition metal oxides (TMOs, e.g., Fe3O4) with high theoretical capacity hold tremendous potential in the field of lithium-ion batteries. Unfortunately, TMOs still suffer from the significant volume expansion and low intrinsic electronic conductivity, which results in irreversible structural collapse, uncontrollable particle aggregation, and sluggish electrochemical reaction kinetics, leading to bad rate performance and cycling stability. Combining TMOs with carbon has become the most effective approach to address the aforementioned issues. However, the interaction mechanism between TMOs and carbon influencing on electrochemical properties has not yet been thoroughly explored and widely recognized. Herein, we proposed a simple and controllable method to synthesize a series of Fe3O4 composites, i.e., Fe3O4 combined with carbon nanotubes (CNTs), via different composite modes, i.e., mixing, embedding and encapsulation. The mixing one exhibits the highest initial capacity but the poorest cycling stability. Encapsulating Fe3O4 into the cavities of CNTs effectively mitigates the volume expansion of Fe3O4, thereby achieving satisfactory rate performance. The embedded composite produces ultrafine Fe3O4 particles within the walls of CNTs, which not only enhances the dispersion of Fe3O4, but also provides an efficient pathway for electronic transport. The electrode based on the embedded composite mode demonstrates excellent cycling stability and an acceptable reversible capacity of 683.7 mAh/g at 1 A/g after 100 cycles. The relationship between structure and electrochemical properties of Fe3O4/CNTs composites is elaborated, which provides universal aspect for future design of high-energy–density lithium-ion batteries.

Well-Dispersed Bi nanoparticles for promoting the lithium storage performance of Si Anode: Effect of the bridging Bi nanoparticles

Silicon (Si) is considered a promising anode material for lithium-ion batteries (LIBs) due to its high theoretical specific capacity of up to 4200 mAh/g. However, the poor cycling and rate performances of Si induced by the low intrinsic electronic conductivity and large volume expansion during the lithiation/delithiation process limit its practical application. Herein, a novel silicon/bismuth@nitrogen-doped carbon (Si/Bi@NC) composite with nanovoids was synthesized and investigated as an advanced anode material for LIBs. In such a structure, ultrafine bismuth nanoparticles coupled with an N-doped carbon layer were introduced to modify the surface of Si nanoparticles. Subsequently, the lithiated LixBi has excellent high ionic conductivity and acts as a fast transport bridge for lithium ions. The introduced carbon coating layer and nanovoids can buffer the volume expansion of Si during the lithiation/delithiation process, thus maintaining structural stability during the cycling process. As a result, the Si/Bi@NC composite exhibits excellent electrochemical performance, providing a relatively high capacity of 955.8 mAh/g at 0.5 A/g after 450 cycles and excellent rate performance with a high capacity of 477.8 mAh/g even at 10.0 A/g. Furthermore, the assembled full cell with LiFePO4 as cathode and pre-lithium Si/Bi@NC as anode can provide a high capacity of 138.8 mAh/g at 1C after 90 cycles, exhibiting outstanding cycling performance.

N-doped lithium titanium oxide for high power Li-ion rechargeable batteries with excellent cyclability

Lithium titanate, Li4Ti5O12 (LTO) is being explored as an anode in Li-ion batteries owing to its minimal structural change during lithiation/delithiation and excellent capacity retention at higher current rates. However, the lack of stable cyclability at higher applied currents owing to low electronic conductivity, restricts its widespread applications. Solid state anionic doping represents a convenient strategy to improve the intrinsic electronic conductivity of the LTO material. Hence, a facile and scalable solid state‐inspired protocol has primarily been devised aimingthe large-scale production of nitrogen-doped LTO. The structural analysis demonstrates the diffusion of nitrogen into the lattice without damaging the intrinsic microstructure of LTO. The 2% nitrogen-doped LTO as a working electrode in Li-ion half-cell, displays enhancement in Li-storage capacity by 30%. Moreover, it exhibits excellent rate performance (131 mAhg−1 @ 5C) and ultra-long cycling stability upto 1000 cycles retaining 82 % capacity. Further, full cell study of N@LTO with LiCoO2 exhibits specific capacities of more than 155 mAh/g at a 0.05C rate. Overall, the enhancement in performance attributes to N doping which is likely to improve not only the electrical conductivity but also the ion transport capabilities. Hence the N@LTO will have potential in high power Li-ion batteries.

Carbonized polyacrylonitrile-coated three-dimensional porous TiP2O7 as a high-rate capability anode for lithium-ion batteries

TiP2O7 is a hopeful anode material for lithium-ion batteries (LIBs) due to its three-dimensional (3D) open skeletons, excellent ion transfer kinetics, and good structural stability. However, the inferior intrinsic electronic conductivity degrades seriously the electrochemical performance of LIBs. Herein, a strategy of carbonized polyacrylonitrile-coated TiP2O7 (TPO/cPAN) with 3D porous structures was proposed to enhance Li+-storage capability. The TPO/cPAN modified with 30 wt% polyacrylonitrile and calcined at 800 ℃ delivers superior long-term cycling stability at 0.5 A g−1 and excellent rate capacities of 558.7, 523.8, 477.5, 409.8, and 303.4 mAh g−1 at 0.1, 0.2, 0.4, 0.8, and 1.6 A g−1, respectively. Structural characterizations and electrochemical analysis reveal that the pyrolytic N-doped carbon layer markedly ameliorates the electron transferability and protects the electrode from organic electrolyte erosion. Meanwhile, the design of 3D porous structures and the generation of rich oxygen defects facilitate Li+ transport and pseudocapacitance energy storage. The work provides a novel pathway for optimizing the electron/ion migration of polyanionic electrode materials.

Boosting the interfacial dynamics and thermodynamics in polyanion cathode by carbon dots for ultrafast-charging sodium ion batteries.

Ultrafast-charging is the focus of next-generation rechargeable batteries for widespread economic success by reducing the time cost. However, the poor ion diffusion rate, intrinsic electronic conductivity and structural stability of cathode materials seriously hinder the development of ultrafast-charging technology. To overcome these challenges, an interfacial dynamics and thermodynamics synergistic strategy is proposed to synchronously enhance the fast-charging capability and structural stability of polyanion cathode materials. As a case study, a Na3V2(PO4)3 composite (NVP/NSC) is successfully obtained by introducing an interface layer derived from N/S co-doped carbon dots. Density functional theory calculations validate that the interfacial bonding effect of V-N/S-C significantly reduces the Na+ transport energy barrier. D-band center theory analysis confirms the downward shift of the V d-band center enhances the strength of the V-O bond and considerably inhibits irreversible phase transformation. Benefitting from this interfacial synergistic strategy, NVP/NSC achieves a high capability and excellent cycling stability with a surprisingly low carbon content (2.23%) at an extremely high rate of 100C for 10 000 cycles (87.2 mA h g-1, 0.0028% capacity decay per cycle). Furthermore, a superior performance at 5C (115.3 mA h g-1, 92.1% capacity retention after 800 cycles) is exhibited by the NVP/NSC‖HC full cell. These findings provide timely new insights for the systematic design of ultrafast-charging cathode materials.