∼1 V lithium intercalation materials are promising anodes for lithium-ion batteries, because such materials give consideration to both the tolerance of lithium plating (e.g., graphite with ∼0.1 V versus Li+/Li easily results in lithium plating due to a too low potential) and the energy density of the batteries (e.g., Li4Ti5O12 with ∼1.55 V decreases the battery voltage, and thus reduces the energy density). Herein, the layered perovskite compound LiEuTiO4 with a 0.8 V lithium intercalation/deintercalation potential plateau was successfully synthesized by the ion-exchange reaction with NaEuTiO4 prepared via a sol–gel method. LiEuTiO4 can deliver a high capacity of 219.2 mA h g−1 (2nd discharge) at a rate of 100 mA g−1. Even after 500 cycles, the discharge capacity remains at ∼217 mA h g−1 and the Coulombic efficiency is 99.2%. To our knowledge, the cycle stability of LiEuTiO4 exceeds all previous ∼1 V electrodes. Different from the common lithium intercalation Ti-based electrodes (such as Li4Ti5O12) based on the reduction of the Ti4+ to Ti3+, electrochemical lithium intercalation into LiEuTiO4 leads to the reduction of the Eu3+ to Eu2+.

In developing all-solid-state polymer electrolytes for wide operating temperature range lithium metal batteries, an exciting organic ionic plastic crystal, N-ethyl-N-methylpyrrolidinium bis(fluorosulfonyl)imide (P12FSI), has been introduced into the pyrrolidinium-based polymeric ionic liquid (PIL)/LiTFSI solid system to obtain a novel class of PIL–P12FSI–LiTFSI solid polymer electrolytes (SPEs). Such SPEs reveal flexible mechanical characters, attractive room temperature ionic conductivity above 10−4 S cm−1, and high thermal and electrochemical stability as well as potential to suppress the lithium dendrite growth. Particularly, Li/LiFePO4 cells assembled with the as-obtained SPE exhibit high discharge capacity and excellent cycle life over a broad operating temperature range (25–80 °C) and good rate performance. This significant finding indicates that the SPE system obtained in our work has great potential for use in wide operating temperature range lithium metal batteries.

•Four hierarchical structures of TiO2 were prepared by facile routes.•The unique architecture endowed the TiO2 superior physical and chemical properties.•The as-prepared TiO2 exhibited impressive cycling performance and rate capability.Titanium dioxide (TiO2) has been considered to be a promisingly alternative anode material for lithium-ion batteries and thus attracted wide research interest. But, its practical application in lithium-ion batteries is seriously impeded by low capacity and poor rate capability. In the present work, the electrochemical performance of TiO2 is significantly improved by elaborately fabricating hierarchical structures. These as-prepared four hierarchical structure TiO2 assembled by different building blocks (TO2-2 h, TO2-6 h, TO2-18 h and TO2-24 h) all exhibit impressed performance. More importantly, the TO2-6 h constructed by curved nanosheets exhibits the best performance, delivering a capacity of 231.6 mAh g−1 at 0.2C after 200 cycles, and capacities of 187.1 and 129.3 mAh g−1 at 1 and 10C after even 1200 cycles, respectively. The results indicated that design and fabrication of hierarchical structure is an effective strategy for significantly improving the electrochemical performance of TiO2 electrodes, and the electrochemical performance of hierarchical structure TiO2 is heavily dependent on its building blocks. It is suggested that thus excellent electrochemical performance may make TiO2-6 h a promising anode material for advanced lithium-ion batteries with high capacity, good rate capability and long life.

•Polymeric ionic liquid-plastic crystal composite electrolytes are obtained.•The composite electrolytes show high ionic conductivity.•The composite electrolytes present favorable mechanical properties.•The composite electrolytes reveal impressive battery performance.In this work, composite polymer electrolytes (CPEs), that is, 80%[(1−x)PIL–(x)SN]–20%LiTFSI, are successfully prepared by using a pyrrolidinium-based polymeric ionic liquid (P(DADMA)TFSI) as a polymer host, succinonitrile (SN) as a plastic crystal, and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) as a lithium salt. XRD and DSC measurements confirm that the as-obtained CPEs have amorphous structures. The 80%[50%PIL–50%SN]–20%LiTFSI (50% SN) electrolyte reveals a high room temperature ionic conductivity of 5.74 × 10−4 S cm−1, a wide electrochemical window of 5.5 V, as well as good mechanical strength with a Young's modulus of 4.9 MPa. Li/LiFePO4 cells assembled with the 50% SN electrolyte at 0.1C rate can deliver a discharge capacity of about 150 mAh g−1 at 25 °C, with excellent capacity retention. Furthermore, such cells are able to achieve stable discharge capacities of 131.8 and 121.2 mAh g−1 at 0.5C and 1.0C rate, respectively. The impressive findings demonstrate that the electrolyte system prepared in this work has great potential for application in lithium ion batteries.

Polymeric ionic liquids (PILs) have stirred up great interest for their potential applications as electrolyte hosts in lithium metal batteries (LMBs) because of their desirable performance. In this work, PIL-based gel polymer electrolytes applied in lithium metal batteries (LMBs) at low–medium temperatures (25 °C, 30 °C and 40 °C) are first reported. A novel imidazolium-tetraalkylammonium-based dicationic polymeric ionic liquid, poly(N,N,N-trimethyl-N-(1-vinlyimidazolium-3-ethyl)-ammonium bis(trifluoromethanesulfonyl)imide) is successfully synthesized, and its structure and purity are confirmed by 1H NMR, FTIR and elemental analysis. Subsequently, the ternary gel polymer electrolytes are prepared by blending the as-synthesized dicationic PIL as the polymer host with 1,2-dimethyl-3-ethoxyethyl imidazolium bis(trifluoromethanesulfonyl)imide (IM(2o2)11TFSI) ionic liquid and LiTFSI salt in different weight ratios. The PIL-LiTFSI-IM(2o2)11TFSI electrolytes reveal low glass transition temperatures around −54 °C and high thermal stability to about 330 °C. Moreover, the ternary gel polymer electrolytes show good ion conductivity around 10−4 S cm−1 at low–medium temperatures, high electrochemical stability and good interfacial stability with lithium metal. Particularly, the Li/LiFePO4 cells assembled with polymer electrolytes at a rate of 0.1 C are able to deliver discharge capacities of about 160 mA h g−1, 140 mA h g−1 and 120 mA h g−1 at 40 °C, 30 °C and 25 °C, respectively, with excellent capacity retention, as well as exhibiting acceptable rate capability. These findings reveal that dicationic PIL-based electrolytes have great potential for use as safe electrolytes in LMBs.

Design and fabrication of tin dioxide/carbon composites with peculiar nanostructures have been proven to be an effective strategy for improving the electrochemical performance of tin dioxide-based anode for lithium-ion batteries, and thus have attracted extensive attention. Herein, we have successfully prepared a uniquely three-dimensional and interweaved wire-in-tube nanostructure of nitrogen-doped carbon nanowires encapsulated into tin dioxide@carbon nanotubes, denoted as NCNW@void@SnO2@C, via a facile and novel approach for the first time. Interestingly, one-dimension void space located between nitrogen-doped carbon nanowires and innermost wall of tin dioxide@carbon tubes is also formed. The possible formation mechanism of wire-in-tube nanostructure is also discussed and determined by transmission electron microscopy, X-ray diffraction measurement, laser Raman spectroscopy and X-ray photoelectron spectroscopy characterizations. This unique NCNW@void@SnO2@C fully combines all the advantages of using a three-dimensional architecture, hollow structure, carbon coating, and a mechanically robust carbon nanowires support, thus exhibiting an excellent electrochemical performance as promising anode materials for lithium-ion batteries. A high reversible capacity of 721.3 mAh g−1 can be remained even after 500 cycles at a current density of 200 mA g−1, as well as a capacity of 456.7 mAh g−1 is obtained even at 3000 mA g−1.

•The CNT@void@SnO2@C nanostructure was prepared by a novel and facile route.•This peculiar architecture endowed the composite superior physical buffer and electric conductivity ability.•This composite exhibited excellent electrochemical performances.Tin dioxide/carbon composites is an important class of promising candidates for anode materials with superior electrochemical performance and thus have attracted extensive attention. Herein, a tube-in-tube nanostructure, denoted as CNT@void@SnO2@C, has been fabricated by a facile and novel strategy. The possible formation mechanism is also discussed and determined by TEM, XRD and XPS characterizations. As a promising anode material for lithium-ion batteries, the CNT@void@SnO2@C exhibits superior lithium storage properties, delivering a reversible capacity of 702.5 mAh g−1 at 200 mA g−1 even after 350 cycles. The excellent performances should be benefited from the peculiar tube-in-tube nanostructure, in which SnO2 located between CNT and outermost carbon coating layers can sure the structural integrity and high conductivity during long-term cycling, and one-dimensional void space formed between the inner CNT and outer SnO2@C nanotubes, in particular, can provide larger free space for alleviating the huge volume variation of SnO2 and accommodating the stress formed during repeated discharge/charge process.

•TiO2-based ionogel electrolytes are prepared by a one-pot sol–gel processing.•TiO2-based ionogel electrolytes have good electrochemical properties.•TiO2-based ionogel electrolytes reveal impressive battery performance.In this work, TiO2-based ionogel electrolytes (TIEs), TiO2/ionic liquid/LiTFSI, are prepared by a one-pot sol–gel processing. The electrochemical performance and potential application in lithium metal batteries (LMBs) of TIEs are evaluated for the first time. It is found that the as-prepared TIE system reveals liquid-like high ionic conductivity, good electrochemical stability and ability to promote uniform lithium electrodeposition. Specifically, LMBs containing the TIE show high discharge capacity and good capacity retention at 25 °C under the 0.1C rate. Also, acceptable rate performance and low-temperature discharge ability can be obtained.

In spite of high-profile theoretical capacity, the practical application of SnO2 or Sn anode materials for lithium-ion batteries is severely impeded by poor electric conductivity and structural instability. Herein, a hybrid structure of SnO2/Sn sandwiched between TiO2 and carbon with rich porosity, good electric conductivity and stable structure, denoted as TiO2@SnOx@C, is fabricated based on the complementary merits of SnO2, TiO2 and carbon anode materials. The TiO2@SnOx@C exhibits a good electrochemical performance when used as anode material for lithium-ion battery, delivering a capacity of 629 mA h g−1 at 200 mA g−1 after 300 cycles. Moreover, a reversible capacity of 490.3 mA h g−1 is obtained at 1000 mA g−1 even after 1000 cycles and is much higher than theoretical capacity of graphite (372 mA h g−1). The effectively complementary and synergic effect among structural stability of TiO2, high theoretical capacity of SnOx, and good conductive and flexible ability of carbon should be responsible for the superior electrochemical performance of TiO2@SnOx@C.

•3-dimensional interweaved TiO2 hollow nanowires were fabricated by a facile strategy.•This structure can buffer the volume change and facilitate Li+ and e− diffusion.•This TiO2 anode presented effective physical buffer ability and conductivity.•It delivered a capacity of 180.8, 153.3 mAh g−1 at 0.2 C and 2 C, respectively.•It exhibited a desirable rate capability.To overcome the issue of inferior practical capacity and electronic conductivity for titanium dioxide (TiO2) anode materials in lithium-ion batteries, an effective strategy is explored to fabricate a nanostructured TiO2 with large specific surface area and confined dimension, considering the nanostructure to achieve increased contact interface between the active materials and the electrolyte, restricted agglomeration of TiO2, enhanced structure stability, shortened diffusion distance of lithium-ion and electron, contributing to desirable electrochemical properties. Herein, we have prepared an intriguing nanostructure of 3-dimensional interweaved anatase TiO2 hollow nanowires (denoted as HNW TiO2) by a facile strategy. When tested as potential anode materials for lithium-ion batteries, this nanostructured HNW TiO2 delivers a reversible capacity of 180.8, 153.3 mAh g−1 at current rate of 0.2 C and 2 C, respectively, indicating good lithium storage performance, which should be benefited from its unique architecture.

In this work, a peculiar nanostructure of SnO2/Sn@carbon nanospheres dispersed in the interspaces of a three-dimensional SnO2/Sn@carbon nanowires network composite (denoted as SnO2/Sn@C) has been successfully fabricated by a facile strategy and confirmed by scanning electron microscopy, transmission electron microscopy, high-resolution transmission electron microscopy, X-ray diffraction, laser Raman spectroscopy, Brunauer–Emmett–Teller method, energy dispersive X-ray spectrometry, and X-ray photoelectron spectroscopy characterization, illustrating the combination of the nanospheres and the 3-dimensional nanowires network. This architecture effectively withstands the volume change and restricts the agglomeration of SnO2/Sn during the cycling process. Moreover, the SnO2/Sn distributed in carbon matrix and the SnO2/Sn@carbon nanospheres dispersed in interspaces of three-dimensional SnO2/Sn@carbon nanowires network facilitate electron and ion transport throughout the electrode. As a result, this composite exhibits excellent performance as a potential anode material for lithium ion batteries and delivers a reversible capacity of 678.6 mA h g−1 at 800 mA g−1, even after 500 cycles.

•A composite of ultrasmall SnO2 embedded in carbon was prepared by a facile strategy.•The peculiar structure brought the composite sufficient physical buffer ability.•This composite (SnO2/C-59) exhibited an excellent electrochemical performance.Tin oxide (SnO2) has received great attention as promising anode for lithium ion batteries because it offers a high theoretical capacity (ca. 782 mAh g−1 for Li4.4Sn) and a safe discharge potential versus Li/Li+ in comparison to commercialized graphite anodes, whereas it also suffer from the drawbacks of the huge volume change and low electronic conductivity during lithiation/delithiation processes. Herein, we have prepared a SnO2/C composite of ultrasmall SnO2 nanoparticles (∼6 nm and ∼59.4% by weight) embedded in carbon matrix (denoted as SnO2/C-59) by a facile hydrothermal and subsequent carbonization approach. In this peculiar architecture, uniform distribution of SnO2, and electronic conductivity of carbon matrix, which can effectively solve the problems of pulverization, loss of electrical contact and particle aggregation during cycling, therefore contributing to excellent lithium storage and cycling stability. A reversible capacity of 839.1 mAh g−1 is obtained at 200 mA g−1 after 217 cycles. More importantly, 712.8 mAh g−1 can be obtained at 800 mA g−1 even after 378 cycles.

Titanium dioxide (TiO2) has received increasing attention as promising anode for lithium ion batteries because it offers a distinct safety advantage in comparison to commercialized graphite anodes, whereas it also suffer from the drawbacks of low practical capacity and relatively low electronic conductivity. Herein, one-dimensional mesoporous anatase TiO2 composed of nanocrystals prepared by a facile procedure is reported for the first time. Such peculiar architecture and intrinsical mesoporous can effectively improve pseudocapacitance charge storage, increase contact interface between the active materials and electrolyte, and enhance the structure stability during cycling, therefore contributing to good lithium storage and excellent cycling stability. A reversible capacity of 202.9 mAhg−1is obtained at 30 mAg−1 after 70 cycles. More importantly, 151 mAhg−1 can be obtained at 200 mAg−1 even after 500 cycles.

Nanostructured Li3V2(PO4)3/C composite has been synthesized by a facile microemulsion method. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Raman spectra, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) results confirm that the as-prepared Li3V2(PO4)3/C sample shows the pure monoclinic structure and nanosphere morphology. Li3V2(PO4)3/C has a particle size of about 100 nm, and these nanoparticles are connected each other by the conductive carbon network. Electrochemical measurements demonstratethat the Li3V2(PO4)3/C nanoparticles can deliver discharge capacities of 129.8, 126.1, 118.0, 116.1 and 110.1 mAh g−1 between 3.0 and 4.3 V, and 171.4, 163.1, 153.2, 144.0 and 133.4 mAh g−1 between 3.0 and 4.8 V at 1, 2, 5, 10 and 20 C, respectively. Even at 20 C rate, it still can present a reversible discharge capacity of 101.8 mAh g−1 with 92.5% capacity retention after 1400 cycles and 96.4 mAh g−1 with 72.3% capacity retention after 1000 cycles in the potential ranges of 3.0-4.3 V and 3.0-4.8 V, respectively. The excellent rate capability and long-term cycle performance demonstrate that the Li3V2(PO4)3/C nanoparticles prepared in this work has great potential for application as cathode materials in high-power lithium ion batteries.Spheric Li3V2(PO4)3/C nanoparticles, which are fabricated by a facile microemulsion method, exhibit excellent rate capability and long cycle life over an extended 1000 cycles when evaluated as a cathode material for lithium ion batteries. These results are due to the nanoscale Li3V2(PO4)3 particles and conductive carbon network.

A series of Ce3+-doped ordered macroporous Li3V2–xCex(PO4)3/C (x = 0, 0.01, 0.03, 0.05) samples have been fabricated via a colloidal crystal template method. The X-ray powder diffraction and scanning electron microscopy analysis demonstrate that the Ce element doping does not affect the original monoclinic structure and macroporous morphology of the pristine Li3V2(PO4)3/C sample. Electrochemical measurement results prove that the Li3V1.97Ce0.03(PO4)3/C sample presents the best electrochemical performance as the cathode material for lithium ion batteries among the as-prepared samples in the potential ranges of both 3–4.3 V and 3–4.8 V. The substitution of V3+ with an appropriate amount of Ce3+ increases the Li+ diffusion coefficient based on the electrochemical impedance spectroscopy results, which is mainly responsible for the excellent electrochemical performance.

A series of ordered macroporous Li3V2(PO4)3 (LVP) cathode materials with three different pore sizes (65 nm, 120 nm and 210 nm) are prepared via a templating method using poly(methyl methacrylate) (PMMA) colloidal crystals as templates. The structure, morphology and electrochemical properties of the as-prepared LVP samples are characterized by SEM, TEM, XRD, BET, galvanostatic charge–discharge tests, cyclic voltammograms and electrochemical impedance spectroscopy measurements. The three LVP samples all show pure monoclinic structure and ordered macroporous morphology. The LVP sample with pore size of 210 nm shows the best electrochemical performance. In the potential range of 3.0–4.8 V, it delivers a high initial discharge capacity of 189.4 mAh g−1 at 0.1 C, which is close to the theoretical capacity (197 mAh g−1). Moreover, at 0.5 C, 1 C and 5 C, it exhibits initial discharge capacities of 170.5, 166.0 and 145.9 mAh g−1, and can still retain 77.3%, 71.2% and 77.1% of the initial discharge capacity after 100 cycles, respectively.

In this work, a peculiar nanostructure of SnO2/Sn@carbon nanospheres dispersed in the interspaces of a three-dimensional SnO2/Sn@carbon nanowires network composite (denoted as SnO2/Sn@C) has been successfully fabricated by a facile strategy and confirmed by scanning electron microscopy, transmission electron microscopy, high-resolution transmission electron microscopy, X-ray diffraction, laser Raman spectroscopy, Brunauer–Emmett–Teller method, energy dispersive X-ray spectrometry, and X-ray photoelectron spectroscopy characterization, illustrating the combination of the nanospheres and the 3-dimensional nanowires network. This architecture effectively withstands the volume change and restricts the agglomeration of SnO2/Sn during the cycling process. Moreover, the SnO2/Sn distributed in carbon matrix and the SnO2/Sn@carbon nanospheres dispersed in interspaces of three-dimensional SnO2/Sn@carbon nanowires network facilitate electron and ion transport throughout the electrode. As a result, this composite exhibits excellent performance as a potential anode material for lithium ion batteries and delivers a reversible capacity of 678.6 mA h g−1 at 800 mA g−1, even after 500 cycles.

Polymeric ionic liquids (PILs) have stirred up great interest for their potential applications as electrolyte hosts in lithium metal batteries (LMBs) because of their desirable performance. In this work, PIL-based gel polymer electrolytes applied in lithium metal batteries (LMBs) at low–medium temperatures (25 °C, 30 °C and 40 °C) are first reported. A novel imidazolium-tetraalkylammonium-based dicationic polymeric ionic liquid, poly(N,N,N-trimethyl-N-(1-vinlyimidazolium-3-ethyl)-ammonium bis(trifluoromethanesulfonyl)imide) is successfully synthesized, and its structure and purity are confirmed by 1H NMR, FTIR and elemental analysis. Subsequently, the ternary gel polymer electrolytes are prepared by blending the as-synthesized dicationic PIL as the polymer host with 1,2-dimethyl-3-ethoxyethyl imidazolium bis(trifluoromethanesulfonyl)imide (IM(2o2)11TFSI) ionic liquid and LiTFSI salt in different weight ratios. The PIL-LiTFSI-IM(2o2)11TFSI electrolytes reveal low glass transition temperatures around −54 °C and high thermal stability to about 330 °C. Moreover, the ternary gel polymer electrolytes show good ion conductivity around 10−4 S cm−1 at low–medium temperatures, high electrochemical stability and good interfacial stability with lithium metal. Particularly, the Li/LiFePO4 cells assembled with polymer electrolytes at a rate of 0.1 C are able to deliver discharge capacities of about 160 mA h g−1, 140 mA h g−1 and 120 mA h g−1 at 40 °C, 30 °C and 25 °C, respectively, with excellent capacity retention, as well as exhibiting acceptable rate capability. These findings reveal that dicationic PIL-based electrolytes have great potential for use as safe electrolytes in LMBs.

∼1 V lithium intercalation materials are promising anodes for lithium-ion batteries, because such materials give consideration to both the tolerance of lithium plating (e.g., graphite with ∼0.1 V versus Li+/Li easily results in lithium plating due to a too low potential) and the energy density of the batteries (e.g., Li4Ti5O12 with ∼1.55 V decreases the battery voltage, and thus reduces the energy density). Herein, the layered perovskite compound LiEuTiO4 with a 0.8 V lithium intercalation/deintercalation potential plateau was successfully synthesized by the ion-exchange reaction with NaEuTiO4 prepared via a sol–gel method. LiEuTiO4 can deliver a high capacity of 219.2 mA h g−1 (2nd discharge) at a rate of 100 mA g−1. Even after 500 cycles, the discharge capacity remains at ∼217 mA h g−1 and the Coulombic efficiency is 99.2%. To our knowledge, the cycle stability of LiEuTiO4 exceeds all previous ∼1 V electrodes. Different from the common lithium intercalation Ti-based electrodes (such as Li4Ti5O12) based on the reduction of the Ti4+ to Ti3+, electrochemical lithium intercalation into LiEuTiO4 leads to the reduction of the Eu3+ to Eu2+.