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In this work, N-doped biomass derived porous carbon (NSBDC) has been prepared utilizing low-cost agricultural waste--sugarcane bagasse as the prototype, and needle-like PANI as the dopant. NSBDC possesses a special 3D interconnected framework structure, superior hierarchical pores and suitable heteroatom doping level, which benefits a large number of applications on ion storage and high-rate ion transfer. Typically, the NSBDC exhibits the high specific capacitance (298 F g−1 at 1 A g−1) and rate capability (58.7% capacitance retention at 20 A g−1), as well as the high cycle stability (5.5% loss over 5000 cycles) in three-electrode systems. A two-electrode asymmetric system has been fabricated employing NSBDC and the precursor of NSBDC (sugarcane bagasse derived carbon/PANI composite) as the negative and positive electrodes, respectively, and an energy density as high as 49.4 Wh kg−1 is verified in this asymmetric system. A NSBDC-based whole symmetric supercapacitors has also been assembled, and it can easily light a 1.5 V bulb due to its high energy density (27.7 Wh kg−1). In addition, for expanding the application areas of NSBDC, it is also applied to lithium ion battery, and a high reversible capacity of 1148 mAh g−1 at 0.1 A g−1 is confirmed. Even at 5 A g−1, NSBDC can still deliver a high reversible capacity of 357 mAh g−1 after 200 cycles, indicating its superior lithium storage capability.

Unstable solid electrolyte interphase between lithium metal and electrolyte results in low coulombic efficiency and limited cycle life, which hinder the utility of lithium metal anode. Besides, how to settle the cathode material corrosion in practical lithium metal batteries is also a key challenge. Here, lithium 2 trifluoromethyl-4,5-dicyanoimidazolide (C6F3LiN4) is reported as valid electrolyte additive for bi-electrode protective films formation in practical Li metal-based batteries. The C6F3LiN4 plays distinct functions in bi-electrode interface, it attributes to robust F, N-rich polymer interphase layer on the cathode which effectively protect the cathode from deterioration. And it promotes the even distribution of LiF and polycarbonate species on anode and prevent the formation of Li dendrites. The symmetric cell of C6F3LiN4 exhibits stable cycling performance with 1 mA cm−2 (700 h). In addition, the improvement in the Li metal deposition uniformity has been confirmed by atomic force microscope and simulation. Benefiting from the synergistic enhanced stability and uniformity of electrode interphase, the LiNi0.5Co0.2Mn0.3O2 || Li metal battery with C6F3LiN4 can maintain high capacity retention of 82.6% after 400 cycles. Importantly, the Li metal pouch battery pairing high-loading cathode (16.12 mg cm−2) also deliver longer cycle life, validating its feasibility in practical applications.

The catalytic activity and stability of electrocatalyst is critical for the commercialization of fuel cells, and recent reports reveal the great potential of the hollow structures with Pt skin coat for developing high-powered electrocatalysts due to their highly efficient utilization of the Pt atoms. Here, we provide a novel strategy to prepare the Pt skin coated hollow Ag-Pt structure (Ag-Pt@Pt) of ∼8 nm size at room temperature. As loaded on the graphene, the Ag-Pt@Pt exhibits a remarkable mass activity of 0.864 A/mgPt (at 0.9 V, vs. reversible hydrogen electrode (RHE)) towards oxygen reduction reaction (ORR), which is 5.30 times of the commercial Pt/C catalyst, and the Ag-Pt@Pt also shows a better stability during the ORR catalytic process. The mechanism of this significant enhancement can be attributed to the higher Pt utilization and the unique Pt on Ag-Pt surface structure, which is confirmed by the density functional theory (DFT) calculations and other characterization methods. In conclusion, this original work offers a low-cost and environment-friendly method to prepare a high active electrocatalyst with cheaper price, and this work also discloses the correlation between surface structures and ORR catalytic activity for the hollow structures with Pt skin coat, which can be instructive for designing novel advanced electrocatalysts for fuel cells.

The high-temperature and high-humidity storage behaviors and electrochemical degradation mechanism of LiNi0.6Co0.2Mn0.2O2 cathode material are investigated systematically. After stored at 55 °C and 80% relative humidity, three kinds of changes are observed compared to the fresh materials. The first change is adsorbed species on the surface of the materials caused by atmospheric H2O and CO2. The second is a layer of impurities consisting of LiOH and Li2CO3 coated on the surface of the materials non-uniformly. The third is a delithiation layer directly contacting with the bulk materials in the near-surface region, which is believed to be formed by lithium-ions migrating out from the lattice accompanied by the generation of the impurities. A different combination of heating temperature, heating time and heating atmosphere is performed to achieve the separation of the adsorbed species and the delithiation layer (together with the impurities) and study the role of different part in electrochemical degradation, respectively. For the first and the following cycles, the effect of the adsorbed species on the electrochemical properties takes a larger proportion than that of the delithiation layer and impurities.

In lithium-ion batteries (LIBs), benefiting from various functional components, functional separators can possess different capabilities to cope with the risks in complex application scenarios. In this work, a functional separator based on the phosphonate-modified nano-scale silica ceramic particles is fabricated to reduce the safety risks in LIBs. Through an anhydrous polymerization process, dimethyl vinylphosphonate (DMVP), a kind of widely used flame retardants, is grafted on silica (SiO2). Then the modified SiO2 (mSiO2) is coated on the pristine polyethylene separator by a typical coating process. Combining the function of the ceramic and phosphonate, the modified ceramic separator displays substantially enhanced thermal stability, without visual thermal shrink up to 200 °C. The flame resistances of separator itself and pouch cells are also significantly improved, even though flammable electrolyte is added. Different from the case when the phosphonate is used as an additive in electrolyte, the phosphonate is fixed firmly on the separator and not easy to be embedded in carbon anode after battery cycles. The coin cells assembled with the modified separators are away from the irreversible loss of discharge capacity and low Coulombic efficiency for the first cycle, which can be attributed to the firm immobilization of organic phosphonate.

The energy density of LiNi0.5Co0.2Mn0.3O2 (NCM523) can be enhanced by increasing the upper-limit charging potential, but it exhibits a significant “capacity decay” during cycling. Therefore, it is necessary to study the intrinsic mechanism for the performance improvement of high-voltage NCM523. In this work, through combining the intrinsic state-of-charge (SOC) of NCM523 revealed by Raman spectroscopy with the electrochemical characterization, the kinetic degradation of Li+ de-/intercalation is found to be a key factor for the apparent capacity decay of NCM523 under the high upper-limit charging potential (>4.3 V). Meanwhile, the apparent capacity loss can be restored significantly by reducing the current density or increasing the operating temperature. Furthermore, the formation of the electrochemical passivation layer on the surface of NCM523 particles is detected by the surface characterization of high-resolution transmission electron microscopy (HR-TEM) and X-ray photoelectron spectroscopy (XPS), which is proved to be another important factor for the kinetic degradation, besides the particle pulverization of NCM523 and the decomposition products of electrolyte adsorbed on the material surface. Thus, this work can help to rationally improve the electrochemical performance of the high-voltage NCM523.

To optimize the electrochemical behavior of NCM-based high-energy lithium-ion batteries (LIBs) in wide temperature ranges, Phenyl trifluoromethane sulfonate (PTM) is demonstrated as the novel electrolyte additive to enhance the electrochemical behavior of LiNi0·6Co0·2Mn0·2O2/graphite cells at 25 °C, −20 °C and 45 °C. The cells with 1.0 wt% PTM-containing electrolyte deliver 80.6% capacity retention after 350 cycles at 25 °C, 73.4% after 100 cycles at −20 °C, and 82.6% after 300 cycles at 45 °C, which are significantly higher than that in standard electrolyte (STD), corresponding to 36.4% at 25 °C, 40.3% at −20 °C, and failure at 45 °C, respectively. According to density functional theory (DFT) simulations and quantitative calculations, the PTM preferentially reduces on the anode and oxidizes on the cathode to participate in the formation of solid electrolyte interphase (SEI) films. In addition, the scanning electron microscopy (SEM), Transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS) and other analysis suggest that the formed SEI films are thinner and more stable for the electrolyte containing PTM, and the formed SEI films effectively control the decomposition of carbonate-based electrolytes and greatly decrease the increased resistance during the cycle.

A new method for the preparation of the mono-sheet bipolar membrane applied to fuel cells was developed based on the pre-irradiation grafting technology. A series of bipolar membranes were successfully prepared by simultaneously grafting of styrene onto one side of the poly(ethylene- co -tetrafluoroethylene) base film and 1-vinylimidazole onto the opposite side, followed by the sulfonation and alkylation, respectively. The chemical structures and microstructures of the prepared membranes were investigated by ATR-FTIR and SEM-EDS. The TGA measurements demonstrated the prepared bipolar membranes have reasonable thermal stability. The ion exchange capacity, water uptake and ionic conductivity of the membranes were also characterized. The H 2 /O 2 single fuel cells using these membranes were evaluated and revealed a maximum power density of 107 mW cm −2 at 35 °C with unhumidified hydrogen and oxygen. The preliminary performances suggested the great prospect of these membranes in application of bipolar membrane fuel cells.

More and more application scenarios of rechargeable batteries like lithium-ion batteries are set up in high-temperature environments, such as large-scale energy storage, aerospace, oil extraction industry, etc. Besides of electrolyte, the separator is also a vital part of the battery's sustainable operation at high temperature working condition, however traditional polyolefin separators and even ceramic-coated polyolefin separators have poor thermal stability. This article provides a fiber-supported aluminum oxide separator with improved flexibility and thermal stability because of the introduced flexible SiC fiber network skeleton. The ceramic separator exhibits electrochemical performance equivalent to commercial separators at room temperature. What's more, with high-temperature electrolyte system, its conductivity at 120 °C reaches 5.12 mS cm−1, which is 3 times higher than that at room temperature, so that the LiFePO4 half-cell has excellent rate performance that still maintains a specific capacity of 140 mAh g−1 for 200 cycles under a rate of 20C at 120 °C. Specially, the half-cell containing the high temperature stable fiber-supported aluminum oxide separator realizes cycles of charging at a high temperature with high rate as 20C and discharging at a room temperature with normal rate of 1C, which is of great guiding significance to practical application.

We have found that the formation of passivation film plays a major role in the negative shift of the decomposition voltage in the hydrogen-generating process. Both the hydrolysis of weak acid ions and the decarboxylation reaction of carboxylate can make the LiCO2CH3 produce a passivation film to inhibit the water decomposition to a certain extent. As for the LiCO2CF3 without hydrolysis of weak acid ion, it can be highly possible to facilitate the introduction of CO2 via its carboxylate specific decarboxylation reaction, and further produce lithium carbonate passivation film as well. However, the water decomposition voltage in the oxygen-producing process is more dependent on the properties of lithium salt anions. Those with strong electron-absorbing groups such as the trifluoromethyl are more likely to effectively endue the aqueous electrolyte with a high oxidative decomposition potential. Moreover, the concentration of LiCO2CF3 aqueous electrolyte can reach up to 28 mol kg−1, and hence the electrochemical stability window of this water-base electrolyte can be expanded to about 3.0 V. This work provides a new idea for the selection of high concentration lithium salt.

Nowadays, the high-nickel ternary cathode materials attract more and more attention because of their high capacity. However, compared with other cathode materials, the disadvantage of high-nickel ternary cathode materials in storage performance is very obvious. The obvious impurities on the surface of high-nickel ternary materials are generated after storage for a period of time, and its electrochemical performance produce a cliff-like decline. In this work, we use the pre-blending of conductive agent to simply and effectively improve the storage performance of LiNi0.6Co0.2Mn0.2O2 cathode materials under high temperature and high humidity conditions. Fine particles of conductive agent can be well filled in the gap between the primary particles of the material, suppressing the sites where impurities are most easily formed during storage. Compared with the pristine materials, when stored for the same time, the impurities generated on the surface of modified materials are significantly fewer, the increase of weight is smaller, and more excellent electrochemical performance is exhibited. It can be seen from the results that the pre-blending of the conductive agent can greatly improve the storage performance of the high-nickel ternary cathode materials.

Novel anion-exchange membranes based on two kinds of pyrrolidonium type ionic liquids, N-methyl-N-vinyl-pyrrolidonium (NVMP) and N-ethyl-N-vinyl-pyrrolidonium (NVEP), have been synthesized via polymerization and crosslinking treatment, followed by membrane casting. The covalent cross-linked structures of these membranes are confirmed by FT-IR. The obtained membranes are also characterized in terms of water uptake, ion exchange capacity (IEC), ionic conductivity as well as thermal, dimensional and chemical stability. The membranes display hydroxide conductivity of above 10−2 S cm−1 at 25 °C. Excellent thermal stability with onset degradation temperature above 235 °C, good alkaline stability in 6 mol L−1 NaOH at 60 °C for 168 h and remarkable dimensional stability of the resulting membranes have been proved. H2/air single fuel cells employed membrane M3 and N3 show the open-circuit voltage (OCV) of 0.953 V and 0.933 V, and the maximum power density of 88.90 mW cm−2 and 81.90 mW cm−2 at the current density of 175 mA cm−2 and 200 mA cm−2 at 65 °C, respectively.

Novel anion exchange membranes (AEMs) based on two types of imidazolium ionic liquids, 1-vinyl-3-methylimidazolium iodide [VMI]I and 1-vinyl-3-butylimidazolium bromide [VBI]Br, have been synthesized by copolymerization. The obtained membranes are characterized in terms of water uptake, ion exchange capacity (IEC), ionic conductivity as well as thermal and chemical stability. The conductivity reaches 0.0226 Scm−1 at 30 °C. All the membranes show excellent thermostability. The membranes are stable in 10 mol L−1 NaOH solution at 60 °C for 120 h without obvious changes in ion conductivity. Fuel cell performance using the resulting membrane has been investigated. The open circuit voltage (OCV) of the H2/O2 fuel cell is 1.07 V. A peek power density of 116 mW cm−2 is obtained at a current density of 230 mA cm−2 at 60 °C. The results demonstrate the brilliant prospect of the developed membranes for alkaline fuel cell applications.

In an endeavor to improve the thermal stability of lithium-ion batteries (LIBs), a new kind of ceramic coated separator has been developed based on introducing one-dimensional silica tubes (ST) to one side of a commercial polyethylene (PE) porous separator. The ST interpenetrating network diminishes the thermal-induced dimensional change of the commercial separator without compromising the cell performance. In particular, compared to spherical silica particle (SP) coated separator, the ST coated separator exhibits significantly enhanced thermal stability at elevated temperature. Furthermore the ST coated separator shows better mechanical performance as well as the improved electrolyte absorption and retention behavior, which provides a promising solution to replace conventional polymer separator for high-performance LIBs.

Copper sulfides are synthesized by heating a mixture of copper and sulfur powders in different stoichiometries in N-methyl-2-pyrrolidinone (NMP) solvent. All the electrodes show excellent electrochemical performance, especially ‘copper excess’ copper sulfides electrodes. These electrodes can be charged and discharged at high rate, with good capacity retention. The electrochemical reaction mechanism of copper sulfides during discharge–charge process is investigated. It is most likely that all of S element in the copper excess electrode would transfer into a crystal of Cu2S during charge–discharge cycles, which corresponded to a single electrochemical reaction and showed excellent cycling and rate performance. These encouraging results indicate that copper-excess copper sulfides could be a promising anode material for lithium batteries with high rate capability.

The V 2 O 5 -coated LiNi 0.5 Mn 1.5 O 4 (LNMO) cathode materials are synthesized via a wet-coating method. V 2 O 5 is capable of lithium intercalating, so the surface of materials is purified. Furthermore lithium ion conductor V 2 O 5 is not only a barrier between electrolyte and LNMO surface to prevent electrolyte decomposition especially at high voltage, but also a HF scavenger thus the spinel structural integrity of LNMO can be preserved for a better cycling reversibility, especially at high temperatures under which conditions the dissolution of Mn 3+ ions into electrolyte via reacting with HF is severely problematic for pristine LNMO as cathode materials. The amount of V 2 O 5 coating affects the electrochemical properties of these samples. We discover that the optimal amount of V 2 O 5 on LNMO surface is about 5 wt%. Compared with pristine LNMO, the coating amount with 5 wt% exhibits an excellent rate capability and better reversibility. The discharge capacity is increased by 15.8%, 17.9%, 16.2%, 16.3%, 19.1% and 21.0% in comparison with pure LNMO, presenting a discharge specific capacity of 123.9, 119.1, 120.8, 117.5, 111.9 and 105.3 mAh g −1 at the rates of 0.2, 0.5, 1, 2, 5 and 10C respectively. In addition, the sample presents a discharge capacity of 131.5 mAh g −1 at 1C, with a retention of 92.2% after 100 cycles. Even cycling at 5C rate and 55 °C, the cell with 5% V 2 O 5 -coated LNMO cathode can has a capacity of 126.3 mAh g −1 , with 92% capacity retention after 100 cycles, implying that V 2 O 5 -coating of LNMO is an effective modified method for lithium ion batteries.

The x Li 2 MnO 3 ·(1− x )Li(Mn 0.33 Co 0.33 Ni 0.33 )O 2 ( x = 0.3, 0.5, 0.7) cathode material with uniform spherical morphology has been successfully prepared by a facile carbonate co-precipitation method. These cathode materials are characterized by X-ray powder diffractometry (XRD), scanning electron microscopy (SEM), and inductively coupled plasma emission spectrometry (ICP-AES). The electrochemical properties of these cathode materials have been studied by charge/discharge cycling at various current rates. The results of these studies suggest that among these materials, the composite cathode with x = 0.5 (Li 1.2 Mn 0.54 Co 0.13 Ni 0.13 O 2 ) exhibiting the better electrochemistry performances than those with x = 0.3 and 0.7. Correspondingly, 2 wt% CuO-coated Li 1.2 Mn 0.54 Co 0.13 Ni 0.13 O 2 possess better cycling stability (173.9 mAh g −1 after 50 cycles at 1C rate and 50 cycles at 2C rate) and rate capability than the pristine one. Meanwhile, the CuO-coating layer of the material has a contribution to improve its thermal stability. We believe it is a promising cathode for the high energy lithium batteries.

In this work, we report the formation of porous Li2MTi3O8 (M = Zn, Co) flakes (hereafter referred to as f-Li2MTi3O8) via a facile one-step solution-combustion in less than 10 min. As anodes for rechargeable lithium-ion batteries, the synthesized f-Li2MTi3O8 exhibits high reversible charge–discharge capacity, great cycling stability and high rate performance. These results can be attributed to the intrinsic characteristics of spinel Li2MTi3O8 flakes, in which a porous framework could provide a diffusion space for lithium ion insertion into and extraction from the anode material, resulting in excellent cycle performance, even cycling at high rate of 2000 mA g−1.

In this paper, a new kind of ceramic-coating separator for lithium-ion batteries is successfully prepared by forming a ceramic layer consisted of Al2O3 powder, carboxymethyl cellulose (CMC) and styrene-butadiene rubber (SBR) mix binder onto one side of pristine PE separator. During the preparation of the separator, water is used as solvent and a very small amount of SBR–CMC mixture is applied as binder to obtain better thermal stability. The effect of thickness of the ceramic-coating layer on its thermal stability, physical properties and electrochemical performance is also investigated. The results clearly showed that the ceramic-coating separator with SBR–CMC binder has wonderful thermal stability, good wettability and high uptake of liquid electrolyte. Pouch cell tests with the ceramic-coating separator also show excellent stable cycle performance.

The LiNi0.8Mn0.1Co0.1O2/Silicon-carbon (NCM811/Si@C) lithium ion battery is used in the plug-in electric vehicle due to its high specific energy. The mileage of electric vehicles can be improved by increasing the energy density of batteries, but the charging process becomes a more challenge issue since the excessive charging current results in high temperature while the thermal stability of NCM811 material is poor. Also, the increasing of temperature may cause the thermal runaway of lithium ion battery. In this work, in order to study the thermal runaway prevention during charging process, the NCM811/Si@C battery model is set up, and the simulation results are verified by the experimental results. The detailed temperature distribution of the battery is observed, which can advise on the thermal management system of the batteries. Based on the thermal runaway data, the maximum safe charge current under different ambient temperature is predicted, and the relationship between maximum safe charging current and ambient temperature is found.

Fundamental insights into Li storage mechanism in α-Ga2O3 allow manipulating materials with improved electrochemical performance. Here, conversion reactions coupled with alloying/dealloying process are uncovered for Li storage in α-Ga2O3 anode, on the basis of ex-situ XRD, XPS, SAED and EDS mapping results. Specifically, both processes are part of irreversible. α-Ga2O3 decorated with amorphous carbon and graphene (α-Ga2O3@C@G) and nitrogen doping are successfully fabricated via a facile approach, showing distinctly improved performance compared with pristine α-Ga2O3 and α-Ga2O3 decorated with graphene (α-Ga2O3@G). In the Ga2O3@C@G, dual carbon improves the electronic conductivity and facilitates electrochemical reconstruction of the Ga2O3@C@G upon cycling that renders high lithium ion diffusion, giving rise to enhanced capacitive contribution for lithium storage. As a result, the Ga2O3@C@G exhibits high discharge/charge capacity of 458/447.3 mAh g−1 after 50 cycles at 0.1 A g−1, with capacitive contribution of 59.2% for lithium ion storage at a scan rate of 1 mV s−1.

A novel electrolyte system having well structurally controlled aliphatic oligoether dendrons with a carbonate core is developed for lithium ion batteries. The synthetic dendrons have high boiling point, much higher dielectric constant up to 7.4–8.7 and better stability against oxidation than the conventional linear carbonates such as DEC. The ionic conductivities of the electrolyte with 80 wt% of dendrons and 20 wt% of LiTFSI are 0.11–0.61 mS cm −1 at 20 °C. A 463443-type prismatic battery having the electrolyte solution with 20 wt% dendrons was prepared and its battery performance such as capacity and cycleability was investigated. The prismatic battery with dendron-based electrolyte has the same level of capacity to that with the conventional carbonate-based electrolyte, and shows good cycleability, suggesting a high possibility to use as a kind of cosolvents for lithium ion batteries.