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With the increasing popularity of new energy electric vehicles, the demand for lithium-ion batteries (LIBs) has been growing rapidly, which will produce a large number of spent LIBs. Therefore, recycling of spent LIBs has become an urgent task to be solved, otherwise it will inevitably lead to serious environmental pollution. Herein, a unique recycling strategy is proposed to achieve the concurrent reuse of cathode and anode in the spent graphite/LiFePO4 batteries. Along with such recycling process, a unique cathode composed of recycled LFP/graphite (RLFPG) with cation/anion-co-storage ability is designed for new-type dual-ion battery (DIB). As a result, the recycle-derived DIB of Li/RLFPG is established with good electrochemical performance, such as an initial discharge capacity of 117.4 mA h g−1 at 25 mA g−1 and 78% capacity retention after 1000 cycles at 100 mA g−1. The working mechanism of Li/RLFPG DIB is also revealed via in situ X-ray diffraction and electrode kinetics studies. This work not only presents a far-reaching significance for large-scale recycling of spent LIBs in the future, but also proposed a sustainable and economical method to design new-type secondary batteries as recycling of spent LIBs.

The number of spent lithium-ion batteries (LIBs) is constantly increasing as their popularity grows. It is important to develop a recycling method that not only can convert large amounts of waste anode graphite into high value-added products but also is simple and environmentally friendly. In this work, spent graphite from an anode was transformed into a cathode for dual-ion batteries (DIBs) through a two-step treatment. This method enables the crystal structure and morphology of spent graphite to recover from the adverse effects of long cycling and be restored to a regular layered structure with appropriate layer spacing for anion intercalation. In addition, pyrolysis of the solid electrolyte interphase into an amorphous carbon layer prevents the electrode from degrading and improves its cycling performance. The recycled negative graphite has a high reversible capacity of 87 mAh g−1 at 200 mA g−1, and its rate performance when used as a cathode in DIBs is comparable to that of commercial graphite. This simple recycling idea turns spent anode graphite into a cathode material with attractive potential and superior electrochemical performance, genuinely achieving sustainable energy use. It also provides a new method for recovering exhausted batteries.

Although ether-based electrolytes have been extensively applied in anode evaluation of batteries, anodic instability arising from solvent oxidability is always a tremendous obstacle to matching with high-voltage cathodes. Herein, by rational design for solvation configuration, the fully coordinated ether-based electrolyte with strong resistance against oxidation is reported, which remains anodically stable with high-voltage Na3 V2 (PO4 )2 O2 F (NVPF) cathode under 4.5 V (versus Na+ /Na) protected by an effective interphase. The assembled graphite//NVPF full cells display superior rate performance and unprecedented cycling stability. Beyond that, the constructed full cells coupling the high-voltage NVPF cathode with hard carbon anode exhibit outstanding electrochemical performances in terms of high average output voltage up to 3.72 V, long-term cycle life (such as 95 % capacity retention after 700 cycles) and high energy density (247 Wh kg-1 ). In short, the optimized ether-based electrolyte enriches systematic options, the ability to maintain oxidative stability and compatibility with various anodes, exhibiting attractive prospects for application.

Graphite as a promising anode candidate of K-ion batteries (KIBs) has been increasingly studied currently, but corresponding rate performance and cycling stability are usually inferior to amorphous carbon materials. To protect the layer structure and further boost performance, tempura-like carbon/carbon nanocomposite of graphite@pitch-derived S-doped carbon (G@PSC) is designed and prepared by a facile and low-temperature modified molten salt method. This robust encapsulation structure makes their respective advantages complementary to each other, showing mutual promotion of electrochemical performances caused by synergy effect. As a result, the G@PSC electrode is applied in KIBs, delivering impressive rate capabilities (465, 408, 370, 332, 290, and 227 mA h g−1 at 0.05, 0.2, 0.5, 1, 2, and 5 A g−1) and ultralong cyclic stability (163 mA g−1 remaining even after 8000 cycles at 2 A g−1). On basis of ex-situ studies, the sectionalized K-storage mechanism with adsorption (pseudocapacitance caused by S doping)-intercalation (pitch-derived carbon and graphite) pattern is revealed. Moreover, the exact insights into remarkable rate performances are taken by electrochemical kinetics tests and density functional theory calculation. In a word, this study adopts a facile method to synthesize high-performance carbon/carbon nanocomposite and is of practical significance for development of carbonaceous anode in KIBs.

As a cathode for sodium‐ion batteries (SIBs), Na3V2(PO4)2F3 (NVPF) with 3D open framework is a promising candidate due to its high working voltage and large theoretical capacity. However, the severe capacity degradation and poor rate capability hinder its practical applications. The present study demonstrated the optimization of Na‐storage performance of NVPF via delicate lattice modulation. Aliovalent substitution of V3+ at Na+ in NVPF induces the generation of electronic defects and expansion of Na+‐migration channels, resulting in the enhancement in electronic conductivity and acceleration of Na+‐migration kinetics. It is disclosed that the formed stronger NaO bonds with high ionicity than VO bonds lead to the significant increase in structural stability and ionicity in the Na+‐substituted NVPF (NVPF‐Nax). The aforementioned effects of Na+ substitution achieve the unprecedented electrochemical performance in the optimized Na3.14V1.93Na0.07(PO4)2F3 (NVPF‐Na0.07). As a result, NVPF‐Na0.07 delivers a high‐rate capability (77.5 mAh g−1 at 20 C) and ultralong cycle life (only 0.027% capacity decay per cycle over 1000 cycles at 10 C). Sodium‐ion full cells are designed using NVPF‐Na0.07 as cathode and Se@reduced graphene oxide as anode. The full cells exhibit excellent wide‐temperature electrochemical performance from −25 to 25°C with an outstanding rate capability (96.3 mAh g−1 at 20 C). Furthermore, it delivered an excellent cycling performance over 300 cycles with a capacity retention exceeding 90% at 0.5 C under different temperatures. This study demonstrates a feasible strategy for the development of advanced cathode materials with excellent electrochemical properties to achieve high‐efficiency energy storage.

The reuse of waste biomass has received more and more attention in recent years due to resource and environmental problems. The development of green, environmentally friendly and cost-effective electrode materials for lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs) is currently the focus of research as key electrochemical energy storage systems. Herein, a facile strategy is adopted to prepare 3D hierarchical porous carbon anodes for LIBs/SIBs by taking advantage of waste crab shells and iron p-toluenesulfonate. The results show that the reversible specific capacity of the prepared anode could reach 703.2 mAh g−1 in LIBs and 283.2 mAh g−1 in SIBs when the current density is 0.05 A g−1. In addition, the contributions of pseudocapacitance, the kinetic characteristics and the storage mechanisms of lithium/sodium ions are investigated through cyclic voltammetry (CV) and galvanostatic intermittent titration techniques (GITTs). Due to the unique structure, the obtained material displays an excellent electrochemical performance, which lays the foundation for the improvement in the performance of waste biomass in LIBs/SIBs.

In the past years, sodium-ion batteries (SIBs) have attracted much attention due to their potential application in large-scale energy storage. However, for now, it is difficult for anode materials to achieve further practical application. In this work, we designed a sandwich structure in which SnO nanoparticles were entrapped between the layers of reduced graphene oxide (SnO/rGO) via freeze drying. The unique structure can not only offer a 3D carbon network but also relieve volume expansion during discharge/charge processes. When used as an anode material for SIBs, the material exhibits excellent rate capability and stable cycling performance. It can be found that a reversible capacity of 132.3 mA h g−1 can be obtained even at a current density of 5 A g−1. In addition, SnO/rGO shows a charge capacity of 109.5 mA h g−1 with a capacity retention of 70.62% after 1200 cycles at 4 A g−1. When assembled with Na3V2(PO4)2O2F (NVPOF) as the cathode, the sodium-ion full cells also display high rate performance, suggesting a reversible capacity of 65.7 mA h g−1 at 20C and an energy density of 138.95 W h kg−1 at −0.1C. The unique structure provides a simple and facile method to achieve high electrochemical performance which is beneficial for developing commercial anode materials for SIBs.

Dual-ion battery (DIB) composed of graphite cathode and lithium anode is regarded as an advanced secondary battery because of the low cost, high working voltage and environmental friendliness. However, DIB operated at high potential (usually ≥ 4.5 V versus Li+/Li) is confronted with severe challenges including electrolyte decomposition on cathode interface, and structural deterioration of graphite accompanying with anions de-/intercalation, hinder its cyclic life. To address those drawbacks and preserve the DIB virtues, a feasible and scalable surface modification is achieved for the commercial graphite cathode of mesocarbon microbead. In/ex-situ studies reveal that, such an interfacial engineering facilitates and reconstructs the formation of chemically stable cathode electrolyte interphase with better flexibility alleviating the decomposition of electrolyte, regulating the anions de-/intercalation behavior in graphite with the retainment of structural integrity and without exerting considerable influence on kinetics of anions diffusion. As a result, the modified mesocarbon microbead exhibits a much-extended cycle life with high capacity retention of 82.3% even after 1000 cycles. This study demonstrates that the interface modification of electrode and coating skeleton play important roles on DIB performance improvement, providing the feasible basis for practical application of DIB owing to the green and scalable coating procedures

One main challenge for phosphate cathodes in sodium-ion batteries (SIBs) is to increase the working voltage and energy density to promote its practicability. Herein, an advanced Na3V2(PO4)2F3@C cathode is prepared successfully for sodium-ion full cells. It is revealed that, carbon coating can not only enhance the electronic conductivity and electrode kinetics of Na3V2(PO4)2F3@C and inhibit the growth of particles (i.e., shorten the Na+-migration path), but also unexpectedly for the first time adjust the dis-/charging plateaux at different voltage ranges to increase the mean voltage (from 3.59 to 3.71 V) and energy density (from 336.0 to 428.5 Wh kg−1) of phosphate cathode material. As a result, when used as cathode for SIBs, the prepared Na3V2(PO4)2F3@C delivers much improved electrochemical properties in terms of larger specifc capacity (115.9 vs. 93.5 mAh g−1), more outstanding high-rate capability (e.g., 87.3 vs. 60.5 mAh g−1 at 10 C), higher energy density, and better cycling performance, compared to pristine Na3V2(PO4)2F3. Reasons for the enhanced electrochemical properties include ionicity enhancement of lattice induced by carbon coating, improved electrode kinetics and electronic conductivity, and high stability of lattice, which is elucidated clearly through the contrastive characterization and electrochemical studies. Moreover, excellent energy-storage performance in sodium-ion full cells further demonstrate the extremely high possibility of Na3V2(PO4)2F3@C cathode for practical applications.

In this study, nano-sized SnO2 decorated on carbon cloth (SnO2/CC) is prepared through a simple and facile solid method. The nano-sized SnO2 is uniformly distributed on the surface of carbon fibers in carbon cloth, providing sufficient free space to relieve volume expansion and reduce electrode pulverization during cycling. The as-prepared SnO2/CC as a flexible, self-supporting and additive-free anode electrode for sodium-ion/lithium-ion batteries (SIBs/LIBs) can demonstrate outstanding electrochemical performance. SnO2/CC after annealing at 350 °C (SC-350) as an anode for SIBs can deliver a reversible capacity of 0.587 mA h cm−2 at the current density of 0.3 mA cm−2 after 100 cycles. In addition, when cycling at 1.5 mA cm−2, SC-350 can maintain 1.69 mA h cm−2 after 500 cycles when used as LIB anode. These results illustrate that the as-prepared SnO2/CC can be a promising flexible anode material for flexible SIBs/LIBs and provide a simple and practical method for designing new flexible electrode materials.

Polyanion-type compounds, used as promising cathode materials for sodium-ion batteries (SIBs), have attracted great attention because of their suitable operating voltage, stable framework and good thermal stability. However, they suffer from inherent low conductivity, poor high-rate capability and unsatisfactory cycle stability. Herein, in order to overcome these deficiencies, a feasible strategy, which integrates high conductivity reduced graphene oxide (rGO) with the representative vanadium-based fluorophosphates to form a 3D carbon network constructed in NaVPO4F, is proposed and investigated. Based on microstructural and morphological characterization, the NaVPO4F nanoparticles are successfully synthesized and uniformly embedded in a robust rGO carbon network. Ascribed to the multifunctional structure design, the reaction kinetics of NaVPO4F were significantly improved, as demonstrated by the electrochemical impedance spectroscopy, cyclic voltammetry at varied scan rates and galvanostatic intermittent titration technique. Moreover, the hard carbon (HC) and the NaVPO4F@rGO composite are employed as the anode and the cathode, respectively, to fabricate a sodium-ion full battery, which exhibits an excellent high-rate capability (75.1 mA h g−1 at 15C) and an outstanding cycling stability (0.0115% capacity decay per cycle over 1500 cycles at 5C rate). This study provides a feasible and effective method to develop high-performance polyanion-type electrode materials for SIBs.

Achieving fast-charging/discharging (FCD) performance for sodium-ion batteries (SIBs) has always been a great challenge, because of their slow reaction kinetics and the difficulty in ensuring the stability of the electrode during sodiation/desodiation. In this study, a hypoxic graphene (HG) is rationally designed and prepared using a simple high temperature treatment process. It is confirmed that the hypoxic surface is more conducive to the rapid conduction of electrons and forming a high quality SEI film in the first cycle to avoid irreversible side reactions. Furthermore, a versatile electrolyte suitable for improving the FCD performance of different carbon materials is screened and used in this system. As a result, the best sample of HG-1300 shows almost full pseudocapacitive behavior as an anode material for SIBs, and exhibits a super FCD performance (110 mA h g−1 at an ultrahigh current density of 200 A g−1, only 4 seconds per cycle) and ultralong lifespan (90.7% capacity retention over 100 000 cycles at 20 A g−1), even surpassing supercapacitors.

Covalent organic frameworks (COF) possess a robust and porous crystalline structure, making them an appealing candidate for energy storage. Herein, we report an exfoliated polyimide COF composite (P-COF@SWCNT) prepared by an in situ condensation of anhydride and amine on the single-walled carbon nanotubes as advanced anode for potassium-ion batteries (PIBs). Numerous active sites exposed on the exfoliated frameworks and the various open pathways promote the highly efficient ion diffusion in the P-COF@SWCNT while preventing irreversible dissolution in the electrolyte. During the charging/discharging process, K

Impossible voltage plateau regulation for the cathode materials with fixed active elemental center is a pressing issue hindering the development of Na-superionic-conductor (NASICON)-type Na

The graphite material from exhausted Li-ion batteries (LIBs) is reused as a favorable anode for Na-ion batteries (NIBs) and K-ion batteries (KIBs) through a recycling treatment. The optimized electrode delivers improved electrochemical performance, such as 162 mA h g−1 in NIBs at 0.2 A g−1 and 320 mA h g−1 in KIBs at 0.05 A g−1. In addition, the insights into Na/K-ion de-/intercalation model evolution and corresponding electrochemical analysis are conducted through in operando X-ray diffraction and a series of other characterization methods, discovering a visible transitional stage for NIBs and an irreversible initial cycle phase transformation for KIBs. In a word, we not only provide a new recycling concept for waste graphite anodes but also carry out a series of significant intercalation mechanism studies, which contribute to anode recycling and shed light on the development of graphite material for promising alternative ion batteries.

Coaxial nanotubes are a significant class of nanoscale building blocks for advanced electrodes of secondary batteries. Herein, one-dimensional (1D) coaxial double nanotubes (DNTs) consisting of α-MnSe inner tubes and N-doped carbon (N–C) outer tubes (abbreviated as α-MnSe@N–C DNTs) are successfully prepared and are demonstrated to be promising anode material for Li-ion and Na-ion batteries (LIBs/NIBs). When used in LIBs, it was revealed by ex situ XRD/HRTEM studies and electrode kinetics that a new electrochemical α → β phase transition plays a crucial role in improving the cycling stability. As a result, the α-MnSe@N–C DNTs electrode delivers a high Li-storage capacity (800 mA h g−1 at 50 mA g−1), excellent rate capability (405 mA h g−1 at 14 A g−1) and ultra-long cycling stability (a high capacity retention of 87.2% even after 9000 cycles at 2 A g−1) with retained 1D morphology. In addition, the outer N–C nanotube can effectively protect the active α-MnSe inner nanotube to realize such outstanding electrochemical properties owing to the high electrical conductivity and particular 1D coaxial nanoarchitecture of the inner nanotube. Moreover, α-MnSe@N–C DNTs also exhibit excellent Li/Na-storage properties and full-cell performances when coupled with commercial LiFePO4 and LiNi0.6Co0.2Mn0.2O2 cathodes in LIBs as well as with the Na3V2(PO4)2O2F cathode in NIBs.

Summary: The development of high-performance cathodes for sodium-ion batteries (SIBs) is one key issue required for the success of large-scale energy storage systems. In addition to performance degradation during cycling, electrode materials are usually hampered by instability when stored in various environments severely restricting their practical application. Here, we report a stable cathode material that shows no obvious capacity attenuation in various storage conditions. The cathode is composed of regular and homogeneous Na3V2(PO4)2O2F0.99Cl0.01 (NVPFCl) microcubes, with electrochemical properties, including high specific capacity (128.2 mA h g-1 at 0.1 C), excellent rate capability (79.8 mA h g-1 at 20 C), long-term cycle life, and all-climate performance. Studies using in/ex situ characterization and electrode kinetics are implemented to reveal the possible reasons for the stability and electrochemical activity of NVPFCl. This work may provide a pathway for the development of all-climate and storage-stable SIB cathode materials.

There are still many problems that hinder the development of sodium-ion batteries (SIBs), including poor rate performance, short-term cycle lifespan, and inferior low-temperature property. Herein, excellent Na-storage performance in fluorophosphate (Na3 V2 (PO4 )2 F3 ) cathode is achieved by lattice regulation based on charge balance theory. Lattice regulation of aliovalent Mn2+ for V3+ increases both electronic conductivity and Na+ -migration kinetics. Because of the maintaining of electrical neutrality in the material, aliovalent Mn2+ -introduced leads to the coexistence of V3+ and V4+ from charge balance theory. It decreases the particle size and improves the structural stability, suppressing the large lattice distortion during cathode reaction processes. These multiple effects enhance the specific capacity (123.8 mAh g-1 ), outstanding high-rate (68% capacity retention at 20 C), ultralong cycle (only 0.018% capacity attenuation per cycle over 1000 cycles at 1 C) and low-temperature (96.5% capacity retention after 400 cycles at -25 °C) performances of Mn2+ -induced Na3 V1.98 Mn0.02 (PO4 )2 F3 when used as cathode in SIBs. Importantly, a feasible sodium-ion full battery is assembled, achieving outstanding rate capability and cycle stability. The strategy of aliovalent ion-induced lattice regulation constructs cathode materials with superior performances, which is available to improve other electrode materials for energy storage systems.

Over the past years, the biomass-derived materials are receiving more and more attention as high-performance and low-cost anodes for sodium-ion batteries (SIBs) and lithium-ion batteries (LIBs). Herein, the hard carbon derived from unburned charcoal (UC-x) is prepared by acid and heat treatment. And it is inferred from morphological characterization that the unique net structure is favorable for electrolyte permeation and charge transfer for Na+/Li+. As a result, the UC-x electrode as an anode shows high specific capacity (150 m Ah g − 1 for SIBs and 350 m A h g − 1 for LIBs at 0.1 A g − 1) and enhanced cycling stability (250 mA h g − 1 after 300 cycles for LIBs and 273 mA h g − 1 after 200 cycles for SIBs). In addition, UC-1200 possesses fast electrochemical kinetics for Na+/Li+ (1–6 × 10−10 cm2 s − 1 for Na+ and 1–2.5 × 10−10 cm2 s − 1 for Li+) and the dominated electrode reaction is mainly controlled by pseudocapacitance. In a word, this work provides a kind of unique biomass material as anodes for SIBs/LIBs from the reutilization of the waste and promotes the development of carbonaceous electrode materials.

Currently, rechargeable sodium-ion batteries (SIBs) with high voltage and high energy density have attracted considerable attention. However, compared with lithium-ion batteries (LIBs), there are many urgent challenges that need to be solved to achieve the practical application of SIBs. Due to the similar physicochemical properties of sodium and lithium, the study of SIBs is based on LIBs. However, the radius of Na+ is larger than that of Li+, a limited number of LIBs electrode materials can be used in SIBs, especially anode materials. Graphite can store sodium ions if an ether-based electrolyte is being used. The storage capacity of graphite for sodium is low (∼35 mAh g−1) when traditional carbonate-based electrolyte is used. Therefore, it is vital that anode materials with splendid rate capability, outstanding cycling performance and low cost are developed rapidly. Among all types of anode materials, metal sulfides (MSx) with higher theoretical specific capacity and lower cost are an ideal practical anode material. Here, a summaryof the recent research advances on MSx of SIBs is provided. The crystal structures, sodium storage mechanism and optimization strategies for high performance batteries are summarized. this paper hopes to provide inspiration for the development of MSx to assist the development of the next generation of rechargeable battery applications.

Metallic selenides have been widely investigated as promising electrode materials for metal-ion batteries based on their relatively high theoretical capacity. However, rapid capacity decay and structural collapse resulting from the larger-sized Na+ /K+ greatly hamper their application. Herein, a bimetallic selenide (MoSe2 /CoSe2 ) encapsulated in nitrogen, sulfur-codoped hollow carbon nanospheres interconnected reduced graphene oxide nanosheets (rGO@MCSe) are successfully designed as advanced anode materials for Na/K-ion batteries. As expected, the significant pseudocapacitive charge storage behavior substantially contributes to superior rate capability. Specifically, it achieves a high reversible specific capacity of 311 mAh g-1 at 10 A g-1 in NIBs and 310 mAh g-1 at 5 A g-1 in KIBs. A combination of ex situ X-ray diffraction, Raman spectroscopy, and transmission electron microscopy tests reveals the phase transition of rGO@MCSe in NIBs/KIBs. Unexpectedly, they show quite different Na+ /K+ insertion/extraction reaction mechanisms for both cells, maybe due to more sluggish K+ diffusion kinetics than that of Na+ . More significantly, it shows excellent energy storage properties in Na/K-ion full cells when coupled with Na3 V2 (PO4 )2 O2 F and PTCDA@450 °C cathodes. This work offers an advanced electrode construction guidance for the development of high-performance energy storage devices.

Hard carbon is regarded as a promising anode material for sodium-ion batteries (SIBs). However, it usually suffers from the issues of low initial Coulombic efficiency (ICE) and poor rate performance, severely hindering its practical application. Herein, a flexible, self-supporting, and scalable hard carbon paper (HCP) derived from scalable and renewable tissue is rationally designed and prepared as practical additive-free anode for room/low-temperature SIBs with high ICE. In ether electrolyte, such HCP achieves an ICE of up to 91.2% with superior high-rate capability, ultralong cycle life (e.g., 93% capacity retention over 1000 cycles at 200 mA g-1 ) and outstanding low-temperature performance. Working mechanism analyses reveal that the plateau region is the rate-determining step for HCP with a lower electrochemical reaction kinetics, which can be significantly improved in ether electrolyte.

This paper deals with the stabilization of fuzzy stochastic systems with multiplicative noise subject to actuator saturation. The Ito's differential equation is used to present the nonlinear stochastic system. Moreover, the Takagi-Sugeno (T-S) fuzzy model is employed to approximate a nonlinear continuous system with multiplicative noise. The actually physical capacity of the actuator is limited and the actuator saturation may severely degrade the performance of the closed-loop systems, lead to a large overshoot, induce a limit cycle and even make the otherwise stable closed-loop system unstable. Thus, the fuzzy controller design problem subject to actuator saturation is discussed in this paper for the fuzzy stochastic systems with multiplicative noise.