Poly(carbonate)-based ionic plastic crystal fast ion-conductor for solid-state rechargeable lithium batteries

Liquid plasticizers with a relatively higher dielectric coefficient like ethylene carbonate(EC),propylene carbonate(PC),and ethyl methyl carbonate(EMC) are the most commonly used electrolyte materials in commercial rechargeable lithium batteries(LIBs) due to their outstanding dissociation ability to lithium salts.However,volatility and fluidity result in their inevitable demerits like leakage and potential safety problem of the final LIBs.Here we for the first time device a subtle method to prepare a novel thermal-stable and non-fluid poly(carbonate) solid-state electrolyte to merge EC with lithium carriers.To this aim,a series of carbonate substituted imidazole ionic plastic crystals(G-NTOC) with different polymerization degrees have been synthesized.The resulting G-NTOC shows an excellent solid-state temperature window(R.T.-115℃).More importantly,the maximum ionic conductivity and lithium transference number of the prepared G-NTOC reach 0.36 × 10^(-3) S cm^(-1) and 0.523 at 30℃,respectively.Galvanostatic cycling test results reveal that the developed G-NTOC solid-state electrolytes are favorable to restraining the growth of lithium dendrite due to the excellent compatibility between the electrode and the produced plastic crystal electrolyte.The fabricated LiIG-NTOCILiFeP04 all-solid-state cell initially delivers a maximum discharge capacity of 152.1 mAh g^(-1) at the discharge rate of 0.1 C.After chargingdischarging the cell for 60 times,Coulombic efficiency of the solid-state cell still exceeds 97%.Notably,the LiIG-NTOCILiFeP04 cell can stably light a commercial LED with a rated power of 0.06 W for more than1 h at 30℃,and the output power nearly maintains unchanged with the charging-discharging cycling test,implying a sizeable potential application in the next generation of solid-state LIBs.

Electrochemical Impedance Spectroscopy Study on Novel Carbon-Sulfur Nano-Composite Cathodes in Lithium Rechargeable Batteries

Carbon-sulfur nano-composite cathodes for lithium rechargeable batteries were investigated by electrochemical impedance spectroscopy (EIS). The novel carbon-sulfur nano-composite material was synthesized by heating sublimed sulfur and high surface area activated carbon (HSAAC) in certain conditions. Equivalent circuits were used to fit the spectra at different discharge states. The variations of impedance spectra, charge-transfer resistance and double layer capacitance were discussed. The changes of EIS with potential were analyzed based on a plausible electrical equivalent circuit model, and some parameters were measured and analyzed about electrochemical performance and state of charge and discharge of the electrode. The good accuracy in fitting values of the model to the experimental data indicates that the mathematical model gives out a satisfying description upon the mechanism of high rate of capacity fade in lithium-sulfur battery.

Hierarchically porous, ultrathin N–doped carbon nanosheets embedded with highly dispersed cobalt nanoparticles as efficient sulfur host for stable lithium–sulfur batteries

The sluggish redox kinetics and shuttle effect of soluble polysulfides intermediate primarily restrict the electrochemical performance of lithium–sulfur(Li–S) batteries. To address this issue, rational design of high–efficiency sulfur host is increasingly demanded to accelerate the polysulfides conversion during charge/discharge process. Herein, we propose a macro–mesoporous sulfur host(Co@NC), which comprises highly dispersed cobalt nanoparticles embedding in N–doped ultrathin carbon nanosheets. Co@NC is simply synthesized via a carbon nitride–derived pyrolysis approach. Owing to the highly conductive graphene–like matrix and well defined porous structure, the designed multifunctional Co@NC host enables rapid electron/ion transport, electrolyte penetration and effective sulfur trapping. More significantly,N heteroatoms and homogeneous Co nanocatalysts in the graphitic carbon nanosheets could serve as chemisorption sites as well as electrocatalytic centers for sulfur species. These Co–N active sites can synergistically facilitate the redox conversion kinetics and mitigate the shuttling of polysulfides, thus leading to improved electrochemical cycling performance of Li–S batteries. As a consequence, the S/Co@NC cathode demonstrates high initial specific capacity(1505 mA h g-1 at 0.1 C) and excellent cycling stability at 1 C over 300 cycles, giving rise to a capacity retention of 91.7% and an average capacity decline of 0.03%cycle-1.

Novel High Rate Lithium Intercalation Cathode Materials

Application of amorphous V2O5/carbon/ncodymium oxide （Nd2O3） composite is one ot ways to surmount me lower electrical conductivity of V2O5. A new type of V2O5/carbon/Nd2O3 composite was prepared by mixing vanadium oxide hydrosol, acetone, carbon and Nd2O3 powder. High rate discharge/charge property of the composite electrode was tested electrochemically. This composite with Nd2O3 added shows the improvement of not only the discharge capacity but also cycle durability discharge capacity. The rate capability of the composite cathode also increases with the addition of Nd2O3. Even at 10 A·g^-1 current density, a capacity of about 250 mAh·g^-1 was obtained at 25 ℃. This enhanced rate capability and cycle life are probably caused by the increase in porosity of open pores and short diffusion length of the active material on the lithium-ion insertion.

Concentrated dual-salt electrolytes for improving the cycling stability of lithium metal anodes

Lithium（Li） metal is an ideal anode material for rechargeable Li batteries, due to its high theoretical specific capacity（3860 mAh/g）, low density（0.534 g/cm3）, and low negative electrochemical potential（-3.040 V vs. standard hydrogen electrode）. In this work, the concentrated electrolytes with dual salts, composed of Li[N（SO2F）2]（Li FSI） and Li[N（SO2CF3）2]（Li TFSI） were studied. In this dual-salt system, the capacity retention can even be maintained at 95.7%after 100 cycles in Li｜Li FePO4 cells. A Li｜Li cell can be cycled at 0.5 mA/cm2 for more than 600 h, and a Li｜Cu cell can be cycled at 0.5 m A/cm2 for more than 200 cycles with a high average Coulombi efficiency of 99%. These results show that the concentrated dual-salt electrolytes exhibit superior electrochemical performance and would be a promising candidate for application in rechargeable Li batteries.

Surface Films Formed on SnO_2 Anode in Lithium Secondary Batteries by FTIR Spectroscopy

The chemical composition of the passivating layer formed on nano SnO2 anodes in 1 M LiClO4＋ （ethylene carbonate）EC ＋ （dimethyl carbonate）DMC at different charge/discharge states in lithium secondary batteries was studied using extra reflectance FTIR spectra. Results show that solvent decomposition reaction that generally occurs on the surface of carbon and alkali metal electrodes also takes place on nano-SnO2 anode, and the major constituent of the passivating layer is Li2CO3 and ROCO2Li. Formation of the passivating layer would certainly lead to the irreversible capacity loss.

Synthesis of CDMO from LiOH and EMD and the Performances of Li/CDMO Rechargeable Batteries

The synthesis of CDMO from LiOH and EMD has been investigated by thermogravimetry and pow- der X-ray diffraction analysis.The results showed that it took place from below 100 to 400℃.When the proportion of Li:Mn in the starting mixture was 3:7,the measured weight loss during this process was 7.40% for heat-treated EMD and 8.33% for non-heat-treated EMD.Based on these data and X-ray diffraction results the obtained product would be 3LiMn204 - MnO2.This material was es- sentially amorphous.It can insert 4.7 Li per 3LiMn_2O_4·MnO_2,leading to a capacity of 170- 200 mAh/g and demonstrated reasonable discharge and recharge cycle performance for both test cells and practical batteries.

A review of solid-state lithium metal batteries through in-situ solidification

High-energy-density lithium metal batteries are the next-generation battery systems of choice,and replacing the flammable liquid electrolyte with a polymer solid-state electrolyte is a prominent conduct towards realizing the goal of high-safety and high-specific-energy devices.Unfortunately,the inherent intractable problems of poor solid-solid contacts between the electrode/electrolyte and the growth of Li dendrites hinder their practical applications.The in-situ solidification has demonstrated a variety of advantages in the application of polymer electrolytes and artificial interphase,including the design of integrated polymer electrolytes and asymmetric polymer electrolytes to enhance the compatibility of solid–solid contact and compatibility between various electrolytes,and the construction of artificial interphase between the Li anode and cathode to suppress the formation of Li dendrites and to enhance the high-voltage stability of polymer electrolytes.This review firstly elaborates the history of in-situ solidification for solid-state batteries,and then focuses on the synthetic methods of solidified electrolytes.Furthermore,the recent progress of in-situ solidification technology from both the design of polymer electrolytes and the construction of artificial interphase is summarized,and the importance of in-situ solidification technology in enhancing safety is emphasized.Finally,prospects,emerging challenges,and practical applications of in-situ solidification are envisioned.

Spent rechargeable lithium batteries in e-waste： composition and its implications

The amount of spent rechargeable lithium batteries （RLBs） is growing rapidly owing to wide application of these batteries in portable electronic devices and electric vehicles, which obliges that spent RLBs should be handled properly. Identification of spent RLBs can supply fundamental information for spent RLBs recycling. This study aimed to determine the differences of physical components and chemical compositions among various spent RLBs. All the samplings of RLBs were rigorously dismantled and measured by an inductive coupled plasma atomic emission spectrometer. The results indicate that the average of total weight of the separator, the anode and the cathode accounted for over 60% of all the RLBs. The weight ratio of valuable metals ranged from 26% to 76%, and approximately 20% of total weight was Cu and Al. Moreover, no significant differences were found among different manufacturers, applications, and electrolyte types. And regarding portable electronic devices, there is also no significant difference in the Co-Li concentration ratios in the leaching liquid of RLBs.

Electrochemical Performance of PEO_(10)LiX-Li_2TiO_3 Composite Polymer Electrolytes

The conductivities of polyethylene oxide (PEO)-based polymer electrolytes (PE) can be improved by the addition of inorganic inert powder. The composite polymer electrolytes (CPE) PEO10LiX (X=4ClO- or 322N(CFSO)-)-Li2TiO3 were prepared by solution casting with inorganic solid electrolyte Li2TiO3 powder as a filler. Results showed that the conductivities of PEO10LiClO4-3wt% Li2TiO3 and PEO10LiN(CF3SO2)2-10wt% Li2TiO3 at 30 ℃ were 8.6×10-6 and 5.6×10-5 S·cm-1, respectively. The conductivities of CPE increased with the decrease of filler抯 particle size. The ionic conduction mechanism analysis showed that there may be three conduction routes in the CPE, i.e., PEO bulk, polymer-filler interface and Li2TiO3 crystal.