Lithium–sulfur (Li–S) battery is an important candidate for next-generation energy storage. However, the reaction between polysulfide and lithium (Li) anode brings poor cycling stability, low Coulombic efficiency, and Li corrosion. Herein, we report a Li protection technology. Li metal was treated in crown ether containing electrolyte, and thus, treated Li was further used as the anode in Li–S cell. Due to the coordination between Li+ and crown ether, a Li+-permeable film can be formed on Li, and the film is proved to be able to block the detrimental reaction between Li anode and polysulfide. By using the Li anode pretreated in 2 wt % B15C5-containing electrolyte, Li–S cell exhibits significantly improved cycling stability, such as∼900 mAh g–1 after 100 cycles, and high Coulombic efficiency of>93%. In addition, such effect is also notable when high S loading condition is applied.Keywords: crown ether; Li-crown ether coordination; lithium anode; lithium protection; lithium sulfur battery;

•Pyr1,2O1TFSI ionic liquid was used in Li/S cell.•Solvent combination was simplified to Pyr1,2O1TFSI/DME or Pyr1,2O1TFSI/DOL.•LiFSI was added to enhance the capacity.•Optimum electrolyte was 1 mol kg−1 LiTFSI in Pyr1,2O1TFSI/DOL with 1% LiFSI.•Li/S cell showed very stable cycling and high capacity in optimum electrolyte.N-methoxyethyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide (Pyr1,2O1TFSI)-based electrolyte is used in Li/S cells, and a series of electrolyte with binary Pyr1,2O1TFSI-1,3-dioxolane (DOL) or Pyr1,2O1TFSI-1,2-dimethoxyethane (DME) solvent is investigated, and bis(fluorosulfonyl)imide lithium (LiFSI) is further used as the additive. The effect of Pyr1,2O1TFSI is studied in terms of scanning electron microscopy (SEM), UV-visible absorption spectroscopy (UV) as well as electrochemical measurement. The results show that using 1 mol kg−1 bis(trifluoromethanesulfonyl)imide lithium (LiTFSI)/Pyr1,2O1TFSI-DOL (65:35 w/w) with 1 wt % LiFSI electrolyte leads to the most stable cycling and decent capacity performance, along with high coulombic efficiency.

The Si–MnOOH composite electrode exhibits very stable cycling and excellent rate capability, such as 1200 mA h g−1 at 12 A g−1, and 700 mA h g−1 at 20 A g−1. The γ-MnOOH component significantly promotes the alloying/de-alloying reaction between Si and lithium.

•Nano-FeF3/graphene composite was fabricated by an in-situ method.•The less than 5% graphene-containing composite exhibited excellent electrochemical property.•Ultrafine particle and the uniform graphene network lead to the superior lithium storage property.•Different processing conditions and different carbon sources both influence the electrochemical performance.Nano-FeF3/graphene composite is successfully fabricated by an in-situ method. The structure and morphology of the samples are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The effect of different processing conditions and different carbon sources is investigated. The electrochemical performance of FeF3/graphene is examined by discharge/charge and electrochemical impedance measurements. The results show that the less than 5% graphene-containing composite exhibits high capacity, stable cycling, and outstanding rate capability. The ultrafine particle size and the homogeneous network between FeF3 and graphene both contribute to the excellent electrochemical property.

•The 5% graphene-containing FeF3/graphene composite exhibited excellent electrochemical property.•Ultrafine particle and graphene incorporation enhance the sodium storage property of FeF3.Nano-sized FeF3/graphene composite has been prepared by a one-pot method. The product shows a significantly improved cycling stability and rate capability comparing with pristine FeF3. The results show that the ultrafine particle size of the composite and the tight contact between graphene and FeF3 are the main reasons for the enhanced electrochemical performance.

Ferrocene-based polymers, poly(ferrocenyl-methylsilane) and its derivatives, were synthesised by ring-opening polymerization. The product shows promising cathode application in Li-ion, Na-ion and all-organic batteries. The ultra-high power density, excellent cycling stability and decent capacity performance makes it comparable or even superior to the conventional inorganic electrode materials.

•Sb2O3/LiMO2 was obtained by rheological phase method and ball milling post-treatment.•Sb2O3/LiMO2 has enhanced cycling stability, rate capability, and thermal safety.•Sb2O3/LiMO2 electrodes have maintained good kinetic property and improved interface.•Sb2O3-coated separator maybe has similar positive effect as Sb2O3/LiMO2.The layered LiMO2 (M = Ni, Co and Mn) materials LiNi1/3Co1/3Mn1/3O2 and LiNi0.4Co0.2Mn0.4O2 are synthesized by rheological phase method. Sb2O3-modified phases are further obtained by mechanical ball milling treatment. The structure and morphology of the bare and modified samples are characterized by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. Charge/discharge tests indicate that the modified phases all improve cycling stability, rate capability and thermal safety. Careful comparison of the charge/discharge profiles reveals that the serious polarization increment in cycling is suppressed in the Sb2O3-modified LiMO2 electrodes. AC impedance shows that Sb2O3/LiNi1/3Co1/3Mn1/3O2 electrode has smaller Rct and Rf value. Further analysis proves that Sb2O3 hinders the reaction between electrolyte and cathode during charge/discharge process and helps to stabilize the SEI. Other experiments prove that using Sb2O3-coated separator can achieve similar positive effect on layered LiMO2 cathode.

•Mesoporous nano-silicon was obtained by magnesium thermal method and HF etching.•The mesoporous nano-Si released the capacity above 1400 mAh g−1 after 100 cycles.•Good performance was obtained without architecture optimization.Magnesium thermal reduction of the silica aggregation following with HF etching is used to obtain mesoporous nano-Silicon. The product shows an 1844 mAh g−1 discharge capacity in the first cycle with 400 mA g−1 current density and it still delivers a 1444 mAh g−1 capacity after 100 cycles. Additionally, it presents a good rate capability. The mesoporous morphology and the ultra-fine particle are the reasons of the good electrochemical property.

•Almost no Ti can enter into the LiCoO2 lattice in LiCo0.998Ti0.002O2 phase.•LiCo0.998Ti0.002O2 phase shows excellent cycling stability between 3.0 and 4.3 V.•The high rate performance of the Ti-modified LiCoO2 materials has been discussed.EDAX measurement reveals that the atomic ratio of Ti/(Ti + Co) is much higher than the mole feed ratios in the preparation for the LiCo0.99Ti0.01O2 material. XPS observation further tells that in LiCo0.998Ti0.002O2 phase with quite low Ti amount, almost no Ti can enter into the LiCoO2 lattice, it is more inclined to enrich in the particle surface. Electrochemical examinations show that the cycling stability of LiCo0.998Ti0.002O2 is as good as that of LiCoO2/LiCo0.99Ti0.01O2 composite between 3.0 and 4.3 V, and the latter has a better rate performance. It is considered that the difference of the high rate performance between the Ti-modified LiCoO2 materials is more likely to originate from the different particle characteristics, when their Ti amounts are low enough.

•Polyimide is proposed as the anode for ARLB and ARSB.•Polyimide/LiCoO2 cell has higher capacity and energy density than other ARLBs.•Polyimide anode shows a good electrochemical performance in NaNO3 solution.•Using polyimide anode supplies an alternate, promising strategy for large-scale energy storage.1,4,5,8-Naphthalenetetracarboxylic dianhydride (NTCDA)-derived Polyimide is proposed as the anode material for aqueous rechargeable lithium-ion or sodium-ion battery (ARLB or ARSB), which is based on a mechanism beyond the intercalation chemistry. Comparing with other transient oxide anode for ARLB, Polyimide has more suitable working voltage, higher capacity and better structure stability. Therefore, the ARLB with Polyimide anode and LiCoO2 cathode presents a specific capacity of 71 mAh g−1 and a specific energy of 80 Wh kg−1 in 5 M LiNO3 solution at the current rate of 100 mA g−1, which is the highest among all reported ARLB system. Besides, it shows excellent cycling stability and rate capability. The ARSB system is demonstrated by Polyimide/NaVPO4F cell. It has been proved that the Polyimide anode has a good capacity performance and cycling stability in 5 M NaNO3 solution. The two aqueous rechargeable batteries with Polyimide anode both show a promising prospect in large-scale energy storage.

The LiCo1-xSbxO2 (0 < x < 1) materials were prepared for the first time. Comparing with parent LiCoO2 sample, they show improved cycleability under higher upper limit potential, better rate capability and thermal stability. XRD, SEM and particle size analysis indicate that the introduction of Sb during preparation effectively suppress the particle growth and thus the “doping” phase shows reduced particle size. Moreover, XPS measurements tell that the added Sb is enriched in the layer near the particle surface. According to these observations, it is reasonable to believe that the mechanism of the performance improvement is attributed to some coating effect for LiCo1-xSbxO2 materials.

•Layer Li[Li0.182Ni0.182Co0.091Mn0.545]O2 was synthesized by rheological phase method under a stepped temperature.•Li[Li0.182Ni0.182Co0.091Mn0.545]O2 cathodes were fabricated by using different binders.•Electrochemical performance of cathodes using aqueous binder is better than that of cathode using non-aqueous binder.A simple rheological phase method has been successfully put forward to synthesize layer Li[Li0.182Ni0.182Co0.091Mn0.545]O2 under a stepped temperature. The structure and morphology of Li[Li0.182Ni0.182Co0.091Mn0.545]O2 powder were characterized. The sub-micron Li[Li0.182Ni0.182Co0.091Mn0.545]O2 sample possesses an integrated layer hexagonal structure with minimal cation disorder. The Li[Li0.182Ni0.182Co0.091Mn0.545]O2 cathodes were prepared with different binders of sodium carboxymethyl cellulose (CMC), polyvinylidene fluoride (PVDF) and sodium alginate (SA). Electrochemical performances, including cyclability, rate capacity and voltage decay, of the cathodes were investigated. Compared with the PVDF, favorable electrochemical properties are obtained by using SA or CMC as the binder. It indicates that the aqueous binder is more suitable for Li[Li0.182Ni0.182Co0.091Mn0.545]O2 cathode in Li-ion battery.

We have fabricated a micron-sized LiCoO2/LiCo0.99Ti0.01O2 composite successfully by solid-phase synthesis, its core-shell structure has been proved by SEM and XPS observation. Electrochemical examinations show that comparing with LiCoO2 and LiCo0.99Ti0.01O2, the obtained LiCoO2/LiCo0.99Ti0.01O2 composite presents greatly enhanced cycling stability as well as rate capability. In addition, DSC measurement indicates that LiCoO2/LiCo0.99Ti0.01O2 has a better thermal safety than LiCoO2. It is considered that all the improvement should be explained by the particular core-shell morphology of the LiCoO2/LiCo0.99Ti0.01O2 sample.Highlights► We have fabricated a micron-sized LiCoO2/LiCo0.99Ti0.01O2 composite by solid-phase synthesis. ► XPS measurement and SEM observation reveal a Ti concentration gradient in the composite. ► The obtained LiCoO2/LiCo0.99Ti0.01O2 composite presents greatly enhanced cycling stability as well as rate capability. ► DSC further indicates that the LiCoO2/LiCo0.99Ti0.01O2 composite has a better thermal stability than the bare LiCoO2.

Ethylene vinyl acetate (EVA) based positive temperature coefficient (PTC) material with a transition temperature (Tc) of 90 °C is proposed and successfully fabricated in this study. It is further introduced into LiFePO4 cathode by directly mixing it with LiFePO4 powder, binder and conductive carbon or sandwiching it between the current collector and LiFePO4 electrode membrane. Thus obtained LiFePO4/PTC composite electrodes both show a self-current-limiting effect at 90 °C. The electrochemical properties of the LiFePO4/PTC composite electrodes are determined in terms of galvanostatic charging/discharging, cyclic voltammograms and electrochemical impedance spectroscopy measurements. Comparing with bare LiFePO4 electrode, both LiFePO4/PTC composite electrodes show no degradation in cycling stability, rate capability and electrochemical kinetic property at room temperature. The results indicate that the proposed LiFePO4/PTC composite electrode with the suitable Tc of 90 °C can effectively prevent thermal runaway before the occurrence of side reactions and better protect lithium ion battery during the abnormal temperature increasing.Highlights► The Tc of PTC material is about 90 °C, much lower than the previously reported. ► They can endow the electrode with a current limiting effect at around 90 °C. ► It will not impose any negative effect on its electrochemical property. ► PTC composite also can be used with LiCoO2 or LiCo1/3Mn1/3Ni1/3O2, etc.

In this paper, the electrochemical behavior of the reduction products in solution for Li/S cell is studied by UV–visual spectroscopy and electrochemical impedance spectroscopy (EIS). The results tell that the redox process of the polysulfide intermediate contains five charge-transfer steps in the practical Li/S cell. The formation of final reduction product of Li2S and the final re-oxidation product of S8 is completely irreversible. The transform between polysulfide and Li2S2 is electrochemical sluggish. The peaks corresponding to transformation Li2Sx ↔ Li2Sy (2 < x < y ≤ 6) are still symmetrical in spite of an increasing polarization with the proceeding of CV scan. While the redox process corresponding to Li2Sm ↔ Li2Sn (4 < m < n ≤ 8) is reversible. The dissolution long-chain polysulfide and deposition of short-chain polysulfide contribute mostly to the electrode deterioration even electrode blockage. Therefore, homogeneous mixing element sulfur with conductive components and alleviating the polysulfide dissolution are equally important to improving the active material utilization and rechargeability for rechargeable Li/S battery.

A facile preparation of the LiFePO4/C composite is achieved through the microwave irradiation method in several minutes. Electrochemical measurements were conducted to examine the evolution of the impurity phase during the microwave heating. It is found that a short microwave heating usually leads to the existence of an amorphous, ferric intermediate, while microwave firing longer than 3 min favors the formation of the Li3Fe2(PO4)3 impurity. A further calcination treatment on the microwave-derived sample has been proved to be an effective way to eliminate the ferric impurity and thus-obtained, phase-pure sample can release a capacity of 160 mAhg− 1.

Poly(anthraquinonyl sulfide) is synthesized and investigated as a novel organic cathode material for rechargeable lithium batteries, which shows excellent reversibility and cyclabilty, and gives important insights into developing a new generation of organic cathode materials with higher performance.

A highly crystalline LiFePO4/C phase was successfully synthesized by a microwave irradiation method in 4 min. SEM and particle size analysis indicate that the particle size of resulting LiFePO4/C is much smaller than that of the solid-state derived sample and that it mostly distributes in the range of 160–600 nm. Cycling tests show that the sample prepared by microwave method can deliver 150 mAh g− 1 at 17 mA g− 1(0.1C). Further AC impedance measurements reveal that the LiFePO4 electrode can be well activated after the first cycle as reflected by the dramatic decrease in the charge transfer resistance.

A novel partly silanized ether solvent of 12,12-diethyl-2,5,8-trioxa-12-silatetradecane is proposed for Li/organo-sulfide or Li/S battery in this paper. It is superior to other ether solvent in high boiling point, high flash point and thus resulted high safety. The conductivity of it-contained electrolyte was measured to be 5.7 × 10−4 S/cm at 25 °C, which meets the requirement for practical application. Anodic polarization curve of it-contained electrolyte attests to its strong resistivity to electro-oxidation, and AC impedance measurement also approves that it has a good compatibility with lithium electrode. Cycling test of Li/1 M LiTFSI in 12,12-diethyl-2,5,8-trioxa-12-silatetradecane/PABTH cell indicates a good utilization of the active material in the new electrolyte system.

The Si–MnOOH composite electrode exhibits very stable cycling and excellent rate capability, such as 1200 mA h g−1 at 12 A g−1, and 700 mA h g−1 at 20 A g−1. The γ-MnOOH component significantly promotes the alloying/de-alloying reaction between Si and lithium.

Poly(anthraquinonyl sulfide) is synthesized and investigated as a novel organic cathode material for rechargeable lithium batteries, which shows excellent reversibility and cyclabilty, and gives important insights into developing a new generation of organic cathode materials with higher performance.

Ferrocene-based polymers, poly(ferrocenyl-methylsilane) and its derivatives, were synthesised by ring-opening polymerization. The product shows promising cathode application in Li-ion, Na-ion and all-organic batteries. The ultra-high power density, excellent cycling stability and decent capacity performance makes it comparable or even superior to the conventional inorganic electrode materials.