Effect of linear carboxylic ester on low temperature performance of LiMn_2O_4-graphite cells

To improve the low-temperature performances of Li-ion cells, three types of linear carboxylic ester-based electrolyte, such as EC/EMC/EA（1：1：2, mass ratio）, EC/EMC/EP（1：1：2, mass ratio） and EC/EMC/EB（1：1：2, mass ratio）, were prepared to substitute for industrial electrolyte（EC/EMC/DMC）. Then, 18650-type Li Mn2O4-graphite cells（nominal capacity of 1150 mA ·h） were assembled and studied. Results show that the cells containing three types of electrolyte are able to undertake 5C discharging current with above 93% capacity retention at-20 °C. Electrochemical impedance spectra show that the discharge capacity fading of Li-ion cells at low temperature is mainly ascribed to the charge transfer resistance increasing with temperature decreasing. In comparison, the cells containing electrolyte of 1.0 mol/L LiPF6 in EC/EMC/EA（1：1：2, mass ratio） have the highest capacity retention of 90% at-40 °C and 44.41% at-60 °C, due to its lowest charge-transfer resistance.

Study on low temperature performance of Gussasphalt on steel decks with hard bitumen

Using a Hamburg wheel-track test device, the resistance to rutting of Gussasphalt is tested and compared. Gussasphalt with hard bitumen has good resistance to rutting. The related resistance abilities to cracking at low temperature of Gussasphalt are tested and compared through flexural experiments and the composite structure fatigue test with temperature dropping. Gussasphalt with high performance polymer modified bitumen has a longer fatigue life and a lower breaking temperature; they can be used in the future surfaces for steel bridge decks in Germany.

Effect of aggregate gradation on low temperature performance of asphalt paving mixtures

Low temperature cracking has become one of the important factors that diminish asphalt pavement's ride quality and service life.Especially in cold region,cracking caused by low temperature is the main distress form.This paper discussed the effect of aggregate gradation on the low temperature performance in asphalt paving mixtures.A total of 11 asphalt mixtures with 11 different aggregate gradations and one asphalt binder content were studied.Volumetric properties of the coarse aggregate and asphalt mixtures showed aggregate grading has a significant impact on the degree of aggregate interlock in asphalt mixtures.A trend is existed in the low temperature performance with the change of gradation.With the aid of mathematic statistics,it indicates gradation affects the low temperature performance significantly.The findings also indicate the relationship between the degree of aggregate interlock in asphalt mixtures and the low temperature performance:With the stone-to-stone contact developed,the mixture has a high energy to resist contract and deformation at low temperature.The properties of fine aggregate and asphalt play an important part in resisting low temperature cracking in floating structure.But it provides lower energy to resist low temperature cracking compared to the skeleton structure.

Experimental study on low temperature performance of polymer drilling mud agents

Drilling fluid additives has a major impact on rheology behavior and other performances of the drilling fluid.The key to low temperature drilling fluids is choosing antifreeze and polymer agent which have a strong ability in resisting low temperature.On the basis of determining glycol as antifreeze agent,the low-temperature-performance and capacities of anti-collapse of regular validity mud agents have been studied,the mechanism of anti-caving of the partially hydrolyzed polyacrylamide(PHPA),polypropylene potassium(KPA) and PAC-141 polymer additives have been also analyzed.A pilot study of compatibility between ethylene glycol and the polymers has educed that the polymers,ethylene glycol and inorganic salt are compatible,and they can significantly reduce the freezing point of drilling fluid.Anti-collapse ability of the drilling mud is the results of synergistic action among the agents.

Interfacial built-in electric field and crosslinking pathways enabling WS_(2)/Ti_(3)C_(2)T_(x) heterojunction with robust sodium storage at low temperature

Developing efficient energy storage for sodium-ion batteries(SIBs)by creating high-performance heterojunctions and understanding their interfacial interaction at the atomic/molecular level holds promise but is also challenging.Besides,sluggish reaction kinetics at low temperatures restrict the operation of SIBs in cold climates.Herein,cross-linking nanoarchitectonics of WS_(2)/Ti_(3)C_(2)T_(x) heterojunction,featuring built-in electric field(BIEF),have been developed,employing as a model to reveal the positive effect of heterojunction design and BIEF for modifying the reaction kinetics and electrochemical activity.Particularly,the theoretical analysis manifests the discrepancy in work functions leads to the electronic flow from the electron-rich Ti_(3)C_(2)T_(x) to layered WS_(2),spontaneously forming the BIEF and“ion reservoir”at the heterogeneous interface.Besides,the generation of cross-linking pathways further promotes the transportation of electrons/ions,which guarantees rapid diffusion kinetics and excellent structure coupling.Consequently,superior sodium storage performance is obtained for the WS_(2)/Ti_(3)C_(2)T_(x) heterojunction,with only 0.2%decay per cycle at 5.0 A g^(-1)(25℃)up to 1000 cycles and a high capacity of 293.5 mA h g^(-1)(0.1A g^(-1)after 100 cycles)even at-20℃.Importantly,the spontaneously formed BIEF,accompanied by“ion reservoir”,in heterojunction provides deep understandings of the correlation between structure fabricated and performance obtained.

Anti-cracking mechanism of diatomite asphalt and diatomite asphalt mixture at low temperature

A kind of neat asphalt and three kinds of diatomite asphalt are tested using differential scanning calorimetry（DSC）. The anti-cracking mechanism of diatomite asphalt is analyzed by DSC and the thermal stress restrained specimen test（TSRST） of the asphalt mixtures. The results show that the low temperature performance of diatomite asphalt is better than that of neat asphalt. The glass transition temperature can reflect the low temperature performance of the diatomite asphalt better and has a good relationship with breaking temperatures. Besides, the TSRST, the bending test, the compressing test and the contraction coefficient test are used to study the low temperature performance of the diatomite asphalt mixture. The results prove that the low temperature performance of the diatomite asphalt mixture is better than that of the neat asphalt mixture. The critical bending strain energy density and the compressing strain energy density of the diatomite asphalt mixture are greater than those of the neat asphalt mixture. After adding diatomite to the asphalt mixture, the contraction coefficient is reduced. Based on the above results, the anti-cracking mechanism of the diatomite asphalt mixture is analyzed from the angle of contraction performance and breaking energy.

Investigation on process mechanism of a novel energy-saving synthesis for high performance Li_(4)Ti_(5)O_(12) anode material

Li_(4)Ti_(5)O_(12)(LTO) anode material demonstrates superior cycling performance due to its stable spinel structure and high lithiation/de-lithiation potential.Herein,a novel energy-saving solid-phase synthesis route for LTO has been successfully designed,employing the cheap industrial intermediate product of metatitanic acid (HTO) as titanium source.Through the in-situ Fourier transform infrared spectroscopy (FTIR)and ex-situ X-ray diffraction (XRD),it is revealed for the first time that the amorphous crystal structure of HTO is more conducive for the Li+insertion,making it possible to prepare LTO at a relatively lower sintering temperature.Utilizing the dehydration carbonization reaction between glucose and sulfuric acid,an ingenious strategy of glucose pre-coating is adopted to avoid the generation of Li_(2)SO_(4) impurity caused by the residual sulfuric acid on the surface of HTO,which meanwhile enhances the conductivity and inhibits the particle growth of LTO.The obtained ALTO@C anode material consequently exhibits excellent electrochemical performance that 132.0 m Ah g^(-1)is remained even at 20 C,and ultra low decay rate of 0.015% per cycle is achieved during 1000 cycles at 2 C.Remarkably,LiCoO_(2)//ALTO@C full cell delivers conspicuous low-temperature property (130.7 m Ah g^(-1)at 0.5 C and almost no attenuation after 300 cycles under-20℃).

Boosted electrochemical performance of Na_(3)V_(2)(PO_(4))_(3) at low temperature through synergistical F substitution and construction of interconnected nitrogen-doped carbonaceous network

Benefitting from its unique NASICON-type framework,the Na_(3)V_(2)(PO_(4))_(3)(NVP)cathodes have aroused extensive interest and have been deemed as the promising cathode candidate for sodium-ion batteries(SIBs).Unfortunately,the poor electronic conductivity,combined with the undesirable volume variations,seriously hinders the practical application of NVP cathode,especially at low temperatures.Herein,a dual-strategy,F substitution accompanied by V vacancies and the construction of three-dimensional(3D)nitrogen-doped carbonaceous frameworks(NC),were employed for the NVP cathode(F-NVP/C@3DNC).The former can remarkably decrease the particle size and enhance Na^(+)migration capability,increasing the ionic conductivity.Meanwhile,the electronic connection and effective buffering can be obtained from the latter,strengthening the electrode integrity.Consequently,up to 100 cycles at 0.1 A g^(-1),a reversible capacity of 113.8 mAh g^(-1),approaching the theoretical value(117 mAh g^(-1)),is demonstrated,accompa-nied by impressive capacity retentions at 1.0(93.75%after 4800 cycles)and 20.0 A g^(-1)(92.7%after 1000 cycles).More importantly,even at-20℃,a superior specific capacity(102.6 mAh g^(-1) after 100 cycles at 0.1 A g^(-1))and high capacity retention(86.6%at 20.0 A g^(-1) up to 1000 cycles)can still be obtained simul-taneously.Significantly,the design of F-NVP/C@3DNC provides insights for the fabrication of polyanion cathodes for applications at low temperatures with modified structure stability and reaction kinetics.

Effect of yttrium and manganese addition on catalytic soot combustion activity and anti-high-temperature stability of CeO_(2) catalyst

In order to analyze the influence of the addition of yttrium and manganese on the soot combustion performance and high temperature stability of CeO_(2) catalyst,a series of Y/Mn-modified CeO_(2) catalysts were prepared.The effects of structural properties,textural properties,oxygen vacancies,Ce^(3+),surface adsorbed oxygen species,reduction properties and desorption properties of oxygen species on the activity were analyzed by various characterization methods.The results of the activity test show that the addition of manganese is beneficial to enhancement of the activity,while the addition of yttrium increases the amount of reactive oxygen species,but decreases the activity.After aging at 700℃,the activity of the CeMn catalyst decreases most sharply,while the catalytic activity of the CeY catalyst can be maintained to a certain extent.Interestingly,the addition of yttrium and manganese at the same time can stabilize the activity.The fundamental reason is that yttrium and manganese move to the surface of the solid solution after aging,which increases the reduction performance of the catalyst,thus contributing to the increase of activity.Although the activity of CeYMn catalyst decreases after aging at 800℃,it is still higher than that of other catalysts aged at 700℃.

Effect of Polydimethylsilxoane Molecular of Soft Segment on Novel Urethane-Siloxane Copolymers

Novel segmented urethane-siloxane copolymers were synthesized by a two-step bulk polymerization procedure using 4,4'-methylenediphenyl diisocyanate( MDI) and 1,4-butanediol( BDO)as the hard segment components and novel polypropyleneoxide polyether( PPO) blocked polydimethylsilxoane( PDMS) α,ω-dihydroxy-( PPO-PDMS-PPO) as the soft segment component,where the hard segment content was 30% by weight,and the molar ratio of NCO / OH was 1. 02. A series of urethane-siloxane copolymers were prepared from different molecular weights of α,ω-dihydroxy-( PPO-PDMS-PPO). The soft segments were different in the molecular of PDMS block segment. Chemical structure,morphology,mechanical properties,surface properties and thermal properties of thermoplastic polyurethane( TPU) were investigated by Fourier transform infrared spectroscopy( FT-IR),scanning electron microscopy and energy dispersive X-ray spectroscopy( SEM-EDX),mechanical properties( MP) test,water contact angle( WCA) test,differential scanning calorimetry( DSC),thermogravimetric analysis( TGA), respectively. According to the obtained results, the hydrophobicity of silicone modified TPU promoted,surface WCA increased from 73° to 120°. Low temperature resistant performance was improved,and the glass transition temperature decreased from- 44. 2℃ to- 120. 8℃. Thermal stability was also improved,the beginning temperature of thermal degradation increased from 281 ℃to 299 ℃.

Solid State Reaction Preparation of LiFePO_4/(C+Cu) Cathode Material and Its Electrochemical Performance

Cu-C co-coated LiFePO4 （LiFePO4/（C ＋ Cu）） cathode material was successfully prepared through solid state reduction reaction. The optimized additive amount of CuO was determined by electrochemical test of series content-dependent samples. Electrochemical performances of LiFePO4/（C ＋ Cu） cathode material were investigated. Crystalline structure, morphology and electrochemical performance of the samples were characterized by X-ray diffraction, scanning electron microscopy （SEM）, transmission electron microscopy （TEM）, energy dispersive spectroscopy （EDS）, charge-discharge tests and AC impedance techniques. Results showed that crystal structure of the bulk material was not destroyed after Cu particles distributed on the surface of LiFePO4/C. With 5 wt% CuO additive, the LiFePO4/（C ＋ Cu） cathode material showed improved electrochemical performance especially at high rates and low temperature. At 25 ℃ and 0.1 C current rate, specific capacity of the Cu-coated sample reaches 161.3 mA h/g. The result was 47 mA h/g higher than that of the un-coated one. At -20 ℃, the discharge capacity of Cu-coated materials was 113.4 mA h/g at 0.1 C rate and 83.8 mA h/g at 5 C rate, which reached about 70% of that at room temperature, respectively.