A methyl pivalate (MP) based electrolyte was for the first time reported for non-aqueous lithium–oxygen (Li–O2) batteries. This new electrolyte in both superoxide radical solution and a real Li–O2 battery environment showed good chemical stability against superoxide radicals, which was confirmed by 1H NMR and 13C NMR measurements.

Storing energy harvested by triboelectric nanogenerators (TENGs) from ambient mechanical motion is still a great challenge for achieving low-cost and environmental benign power sources. Here, an all-solid-state Na-ion battery with safe and durable performance used for efficient storing pulsed energy harvested by the TENG is demonstrated. The solid-state sodium-ion batteries are charged by galvanostatic mode and pulse mode with the TENG, respectively. The all-solid-state sodium-ion battery displays excellent cyclic performance up to 1000 cycles with a capacity retention of about 85% even at a high charge and discharge current density of 48 mA g−1. When charged by the TENG, an energy conversion efficiency of 62.3% is demonstrated. The integration of TENGs with the safe and durable all-solid-state sodium-ion batteries is potential for providing more stable power output for self-powered systems.

Tannic acid, one of the most common tea polyphenols, is a superoxide radical scavenger that is coated on the PP membrane to protect it from being attacked by superoxide radicals during the discharging and charging process of the Li–O2 battery. The radical scavenging capability of TA was evaluated in both KO2 + crown solution and Li–O2 battery and the effective superoxide radical scavenging ability of TA was confirmed; moreover, due to this ability, it highly improved the cycling stability of the Li–O2 battery.

A novel electrolyte with chloromethyl pivalate (CP) used as solvent was first reported for non-aqueous lithium-oxygen (Li-O2) batteries. Since there are no α-H atoms in the structure of CP, the CP based electrolyte in both superoxide radical solution and real Li-O2 battery environment showed good chemical stability against superoxide radicals, which was confirmed by 1H NMR and 13C NMR measurements. Without a catalyst in the cathode of Li-O2 batteries, the batteries showed high specific capacity and cycling stability.Download high-res image (102KB)Download full-size imageA novel stable liquid electrolyte with chloromethyl pivalate used as solvent for Li-O2 batteries was first reported, and the batteries showed high specific capacity and good cycling stability.

A novel LiFSI/TEGDME-DX electrolyte with good compatibility to a lithium anode is firstly proposed for the rechargeable non-aqueous Li–O2 battery, in which an improved performance with longer cycle life was achieved when compared with the conventional LiTFSI/TEGDME electrolyte.

Non-aqueous lithium–oxygen (Li–O2) batteries have been considered as the superior energy storage system due to their high-energy density, however, some challenges limit the practical application of Li–O2 batteries. One of them is the lack of stable electrolyte. In this communication, a novel electrolyte with ethylene sulfite (ES) used as solvent for Li–O2 batteries was reported. ES solvent showed low volatility and high electrochemical stability. Without a catalyst in the air-electrode of Li–O2 batteries, the batteries showed high specific capacity, good round-trip efficiency and cycling stability.An ethylene sulfite based electrolyte was used in non-aqueous lithium–oxygen batteries, and the batteries showed high specific capacity, good round-trip efficiency and cycling stability.Download full-size image

To solve the wetting capability issue of commercial polypropylene (PP) separators for lithium-ion batteries (LIBs), we developed a simple and new dipping surface coating method. In this method, pyrogallic acid (PA) is used as the sole coating precursor, and the PA coatings are formed spontaneously on the PP separator surfaces. Attenuated total reflection-infrared (ATR-IR) spectroscopy and X-ray photoelectron spectroscopy (XPS) measurements show that PA has been successfully coated on the surface of the PP separator. The PA coatings make the PP surfaces hydrophilic, while the micro-porous structure of the separators remains intact. The improved LIB performance including discharge specific capacity, cycling performance and rate capability is obtained by using these PA coated PP separators due to their better wetting capability, higher electrolyte uptake and ionic conductivity. XPS measurements indicate that the PA coatings show good stability and strong adhesion to the PP separators after the cycling test in LIBs. This study provides an effective and cheap way to achieve hydrophilic modification of commercial polyolefin separators for LIB applications, and has potential application to solve similar surface property issues of other membranes.

To solve the wetting capability issue of commercial polypropylene (PP) separators in lithium-ion batteries (LIBs), we developed a simple dipping surface-coating process based on tannic acid (TA), a natural plant polyphenol. Fourier transform infrared and X-ray photoelectron measurements indicate that the TA is coated successfully on the PP separators. Scanning electron microscopy images show that the TA coating does not destroy the microporous structure of the separators. After being coated with TA, the PP separators become more hydrophilic, which not only enhances the liquid electrolyte retention ability but also increases the ionic conductivity. The battery performance, especially for power capability, is improved after being coated with TA. It indicates that this TA-coating method provides a promising process by which to develop an advanced polymer membrane separator for lithium-ion batteries.Keywords: lithium-ion battery; power capability; separator; tannic acid; wetting capability;

Yolk–shell structured Si–C nanocomposites are easily synthesized by using a new method based on alkaline etching technology, and exhibit high specific capacity, good cycling stability and rate performance as anodes for lithium-ion batteries.

•Polydopamine used as carbon precursor to prepare carbon coated TiO2 composite.•The effect of the carbon layer thickness of the lithium-ion battery is investigated.•The optimized thickness of the carbon layer is about 4–5 nm.•The lithium-ion battery using carbon coated TiO2 shows good cyclability.Anatase TiO2 has attracted much attention as a safe anode material for lithium-ion battery applications, due to its low electronic conductivity and severe aggregation during Li+ insertion/extraction processes, the practical application of the anatase TiO2 is still hindered by poor long-term cycling stability. In order to improve the cycling performance of lithium-ion batteries, a uniform thin nitrogen-doped carbon layer with a thickness of 3–6 nm is successfully coated on the surface of the anatase TiO2 nanoparticles by using polydopamine as carbon precursor. Compared with the pristine TiO2 electrode, the carbon coated TiO2 nanocomposites electrodes show very good capacity retention and cycling performance.

•Polydopamine coated electrospun PVDF nanofibrous membranes as separator are prepared.•PDA coating makes the PVDF surface hydrophilic.•The battery using the PDA coated separator exhibits better cycling performance.•The battery using the PDA coated separator shows higher power capability.In this study, polydopamine (PDA) coated electrospun poly(vinyldiene fluoride) (PVDF) nanofibrous membranes used as separator for lithium-ion batteries are successfully prepared. Their morphology, chemical and electrochemical characterization are investigated. The morphology and porosity measurements of the membranes show that the PDA coating does not harm to the structure of the electrospun PVDF nanofibrous membranes. Due to the PDA coating, it makes the PVDF surface hydrophilic and thus increases the electrolyte uptake and ionic conductivity, resulting in the enhanced performance of batteries. The battery using the PDA coated PVDF nanofibrous separator exhibits better cycling performance and higher power capability than that the battery using the bare PVDF nanofibrous separator. This study underlines that the PDA-coating treatment provides a promising process for the fabrication of advanced electrospun nanofibers separator in the lithium-ion battery applications.

•Used Nafion in the Na-form swollen with non-aqueous solvent as electrolyte.•Demonstrated a sodium-ion battery can be operated by using Nafion as electrolyte.•Sodium-ion battery using Nafion as electrolyte shows good cycling stability.Nafion 115 commercial membranes in the Na+-form (Nafion-Na) swollen with non-aqueous solvent used as both electrolyte and separator for sodium-ion battery were investigated. After swollen with ethylene carbonate (EC) – propylene carbonate (PC) mixed solvent, the Nafion-Na membranes showed ionic conductivity of 3.52 × 10−4 S cm−1 at room temperature and 1.52 × 10−3 S cm−1 at 70 °C, respectively. Compared with the conventional sodium-ion battery using the liquid electrolyte, the battery using the Nafion-Na membranes as electrolyte showed good cycling stability. For Na0.44MnO2 cathode in the sodium-ion battery, the capacity retention using the conventional liquid electrolyte (1 mol L−1 NaClO4 in EC:PC = 1:1, v:v) was about 67.6% after 50 cycles, however, the capacity retention using the Nafion-Na membrane electrolyte was about 92.5% after 50 cycles.

An ion exchange polymer coating on the LiMn2O4 cathode to overcome capacity fading of a lithium-ion battery at high temperatures is first demonstrated, and it shows very good capacity retention compared with the pristine LiMn2O4 cathode without coating.

New sodium-ion batteries using ion exchange membranes swollen with nonaqueous solvents as both electrolytes and separators have been first demonstrated, which show not only higher reversible specific capacity, but also better cycling stability compared with the conventional sodium-ion batteries using a liquid electrolyte.

In order to overcome severe capacity fading of LiMn2O4 cathode lithium-ion battery, tris(trimethylsilyl) borate (TMSB) is used as an electrolyte additive. With 0.5 wt% TMSB addition into the electrolyte (EC/DMC with 1 M LiPF6), the capacity retention is significantly improved at both room temperature and 55 °C. The effects of the TMSB on the LiMn2O4 electrode are investigated via a combination of cyclability, capacity retention of high temperature storage, electrochemical impedance spectroscopy (EIS), scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). Based on these results, it is suggested that the improved cyclability of the cells containing the TMSB additive is mainly originated from the participation in the formation of solid electrolyte interface (SEI) on the surface of electrode, the dissolution of LiF out of the SEI and the enhancement of cyclability of Li anode.Highlights► TMSB used as additive to improve cyclability of LiMn2O4 cathode lithium-ion battery. ► The lithium-ion battery containing TMSB shows excellent capacity retention at 55 °C. ► TMSB participated in the formation of SEI on the surface of electrode. ► Enhancement of cyclability of Li anode by TMSB additive.

•Nitrogen-doped carbon coated TiO2 composite are prepared.•Polydopamine is used as nitrogen-containing carbon precursor.•An uniform carbon layer is coated on the surface of TiO2 nanoparticles.•The battery using carbon coated TiO2 anode shows excellent cycling performance.In order to improve cycle life of lithium-ion batteries, nitrogen-doped carbon coated anatase TiO2 (TiO2@C) anode materials were prepared by using polydopamine as carbon precursor. Transmission electron microscopy measurements showed that an uniform and continuous carbon layer with thickness of 4±0.5 nm was coated on the surface of the TiO2 nanoparticles. From X-ray photoelectron spectroscopy analysis, the weight content of nitrogen in the carbon coating layer was about 7.96 wt%. Thermogravimetric analysis results showed that the carbon content of the TiO2@C nanocomposite is about 4.2 wt%. Compared with the pristine TiO2 electrode, the TiO2@C nanocomposite electrode showed higher discharge retention and better cycling performance.

A lithium-ion polymer battery using the lithiated perfluorinated sulfonic ion-exchange membranes swollen with organic non-aqueous solvent as both separator and electrolyte is demonstrated, and shows very good capacity retention compared with the conventional lithium-ion battery using the liquid electrolyte.

High ionic conductivity exceeding 10−3 S cm−1 at room temperature is achieved with lithiated perfluorinated sulfonic acid (PFSA-Li) ion exchange membranes by swelling in nonaqueous organic solvents. The dependence of ionic conductivity on the membrane equivalent weight, solvent uptake, solvent properties including viscosity and dielectric constant and temperature is investigated for PFSA-Li membranes. The high performance of Li-ion battery using the PFSA-Li membranes as both electrolyte and separator is demonstrated. This new battery shows very good thermal stability and cyclic performance as compared to conventional Li-ion battery using organic liquid electrolytes. At 55 °C, this battery shows less than 3% discharge capacity loss over 120 cycles, however battery with liquid electrolyte decreased to 76% of the initial capacity after 80 cycles.

A LiMn2O4 cathode lithium-ion battery using lithiated ion exchange membranes swollen with organic non-aqueous solvent as the electrolyte to overcome capacity fading at high temperature is first demonstrated, and shows very good capacity retention compared with conventional lithium-ion batteries using liquid electrolyte.

Tris(trimethylsilyl) borate (TMSB) used as new electrolyte additive to improve performance of LiFePO4 based lithium-ion battery is investigated in this paper. The effects of the TMSB on the LiFePO4 electrode are investigated via a combination of electrochemical impedance spectroscopy (EIS), cyclability, scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS). It is found that the LiFePO4 battery with a composite LiPF6-based electrolyte containing 1 wt% TMSB additive exhibits higher discharge retention and better cycling performance than the battery without TMSB additive at both 30 °C and 55 °C. SEM and XPS measurements show the changes of surface morphology and formation of solid electrolyte interface (SEI). EIS results indicate that the interfacial impedances of the batteries after cycled at 55 °C with the electrolyte containing TMSB additive are significantly smaller than the batteries without additive. The improved performances are ascribed to the enhancement of the thermal stability of the electrolyte and the modification of SEI component on the LiFePO4 electrode.Highlights► TMSB is investigated as a new electrolyte additive for lithium-ion battery. ► Use of TMSB additive improves effectively the cycle performance of battery. ► TMSB would be a promising additive for lithium-ion battery.

Supercritical carbon dioxide (Sc-CO2) thermal treatment to enhance performance of Nafion 212 (NR212) commercial membranes for direct methanol fuel cells (DMFCs) is described. It is shown that the microstructure of NR212 membranes is re-organized after the Sc-CO2 treatment, and then the performance of NR212 membranes is improved. Specifically the thinner NR212 membranes after the Sc-CO2 treatments have higher proton conductivity and better capacity of barrier to methanol crossover compared with the thicker Nafion 117 membranes. It is demonstrated that the DMFC performance of the Sc-CO2 treated NR212 membranes is better than that of Nafion 117 membranes.Highlights► Supercritical carbon dioxide treatment was used to enhance performance of NR212. ► The microstructure of NR212 membranes was reorganized after the Sc-CO2 treatment. ► The treated NR212 membranes showed higher proton conductivity than Nafion 117. ► The treated NR212 membranes showed lower methanol permeability than Nafion 117. ► DMFC performance of the treated NR212 membranes was better than Nafion 117.

Supercritical carbon dioxide (Sc-CO2) thermal treatment to enhance performances of both Nafion 212 (NR212) commercial membranes with H-form and Na-form for direct methanol fuel cells (DMFCs) is described. XRD measurements show that the crystallinity of H-form NR212 membranes increases with increasing the treated temperature in the Sc-CO2 system, however, the crystallinity of Na-form NR212 membranes decreases with increasing the treated temperature. Since the bigger crystallites formed after the Sc-CO2 treatments, it improves the mechanical strength and dimensional stability of the Sc-CO2 treated NR212 membranes with H-form and Na-form. Compared with the as-received NR212 membranes, all the Sc-CO2 treated NR212 membranes show higher proton conductivity and better capacity of barrier to methanol crossover. From Fenton test, it can be found that the Sc-CO2 treated NR212 membranes have better chemical stability than that of NR212 membranes. Therefore, NR212 membranes treated by the Sc-CO2 method may be promising candidate electrolytes for DMFC applications.Highlights► NR212 membranes are treated by using supercritical carbon dioxide for DMFCs. ► NR212 membranes with H-form and Na-form are treated. ► Proton conductivity of the treated NR212 membranes is improved. ► Methanol permeability of the treated NR212 membranes is lower than that of NR212. ► The treated NR212 membranes show better chemical stability.

High performance polyvinylidene fluoride (PVDF) flat sheet ultrafiltration (UF) membranes have been prepared by an immersion precipitation phase inversion method using perfluorosulfonic acid (PFSA) as a pore former and as a hydrophilic component of the membranes and polyethylene glycol (Mw = 400) (PEG400) as a pore forming agent. The effects of the presence of PEG and the concentration of the PFSA on the phase separation of the casting solutions and on the morphologies and performance of UF membranes including their porosity, water flux, rejection of bovine serum albumin (BSA) protein, and anti-fouling property were investigated. Phase diagrams, viscosities and the phase separations upon exposure to water vapor showed that both PEG400 and PFSA promoted demixing of the casting solution. Scanning electron microscopy measurements showed that the PVDF-PFSA blend membranes had more macropores and finger-like structures than the native PVDF membranes. The PVDF-PFSA membrane (5 wt-% PEG400 + 5 wt-% PFSA) had a pure water flux of 141.7 L/m2·h, a BSA rejection of 90.1% and a relative pure water flux reduction (RFR) of 15.28%. These properties were greatly superior to those of the native PVDF membrane (pure water flux of 5.6 L/m2·h, BSA rejection of 96.3% and RFR of 42.86%).

The transport properties of PFSA for direct methanol fuel cell application were investigated, including water uptake, proton conductivity, methanol permeability and selectivity of perfluorosulfonic acid (PFSA) membranes as a function of the ion exchange capacity.

Bimetallic Pt–Co nanoparticles were co-deposited on polypyrrole (PPy)-multiwalled carbon nanotube (MWCNT) composite by formaldehyde reduction route to develop an anode catalyst for direct methanol fuel cells (DMFCs). PPy-MWCNT support was prepared by in situ polymerization of pyrrole on MWCNT. The electrochemical activity of this catalyst towards methanol oxidation and the important influencing factors have been investigated. The Pt–Co/PPy-MWCNT composite via over-oxidation treatment shows higher catalytic activity and potential application value for DMFCs.

A LiMn2O4 cathode lithium-ion battery using lithiated ion exchange membranes swollen with organic non-aqueous solvent as the electrolyte to overcome capacity fading at high temperature is first demonstrated, and shows very good capacity retention compared with conventional lithium-ion batteries using liquid electrolyte.

New sodium-ion batteries using ion exchange membranes swollen with nonaqueous solvents as both electrolytes and separators have been first demonstrated, which show not only higher reversible specific capacity, but also better cycling stability compared with the conventional sodium-ion batteries using a liquid electrolyte.

Tannic acid, one of the most common tea polyphenols, is a superoxide radical scavenger that is coated on the PP membrane to protect it from being attacked by superoxide radicals during the discharging and charging process of the Li–O2 battery. The radical scavenging capability of TA was evaluated in both KO2 + crown solution and Li–O2 battery and the effective superoxide radical scavenging ability of TA was confirmed; moreover, due to this ability, it highly improved the cycling stability of the Li–O2 battery.

A polymer lithium–oxygen battery based on lithiated perfluorinated sulfonic conducting ionomers swollen with non-aqueous solvents used as both the electrolyte and separator is successfully operated at room temperature, and shows good cycling stability and rate capability and is even operable for many cycles with a capacity as high as 1500 mA h gcarbon−1. It demonstrates the suitability of the polymer lithium–oxygen battery as a high-energy storage system.

Core–shell nano-structured carbon composites have been used as electrode materials in lithium-ion batteries (LIBs) with increasing attention. The large volume swing during lithiation/delithiation processes and poor electronic conductivity are two key issues in the newly-proposed electrode materials, which severely limit their practical applications in LIBs. In order to solve these problems, we report a facile and versatile method to prepare core–shell nano-structured carbon composites using low cost and widely available tannic acid as the carbon source. The carbon layers with controlled thicknesses of 6–12 nm and 1–3 nm were coated on the surface of Si and TiO2 nanoparticles, respectively. Due to the carbon layers, both the Si@C and TiO2@C nanocomposites used as anode materials in LIBs showed excellent electrochemical performances including good cycling stability and high rate capability. We believe that this method may be applicable to various carbon-coating nanocomposites.

Yolk–shell structured Si–C nanocomposites are easily synthesized by using a new method based on alkaline etching technology, and exhibit high specific capacity, good cycling stability and rate performance as anodes for lithium-ion batteries.

To solve the wetting capability issue of commercial polypropylene (PP) separators for lithium-ion batteries (LIBs), we developed a simple and new dipping surface coating method. In this method, pyrogallic acid (PA) is used as the sole coating precursor, and the PA coatings are formed spontaneously on the PP separator surfaces. Attenuated total reflection-infrared (ATR-IR) spectroscopy and X-ray photoelectron spectroscopy (XPS) measurements show that PA has been successfully coated on the surface of the PP separator. The PA coatings make the PP surfaces hydrophilic, while the micro-porous structure of the separators remains intact. The improved LIB performance including discharge specific capacity, cycling performance and rate capability is obtained by using these PA coated PP separators due to their better wetting capability, higher electrolyte uptake and ionic conductivity. XPS measurements indicate that the PA coatings show good stability and strong adhesion to the PP separators after the cycling test in LIBs. This study provides an effective and cheap way to achieve hydrophilic modification of commercial polyolefin separators for LIB applications, and has potential application to solve similar surface property issues of other membranes.