Analysis of electrochemical performance of lithium carbon fluorides primary batteries after storage

Lithium carbon fluorides(Li/CFx)primary batteries are of highly interests due to their high specific energy and power densities.The shelf life is one of the major concerns when they are used as backup power,emergency power and storage power in landers,manned spacecraft or military applications.In this work,real-time storage tests are carried out for both energy-type and power-type Li/CFx pouch batteries at 25℃.Accelerated storage tests are performed at elevated temperature of 55℃.The electrochemical tests are conducted throughout the aging period of 0-365 days for various batteries to study the effects of temperature on both type of batteries.The observed electrochemical behaviors are explained with the evidences from multiple characterizations for post-tested samples.

Reversible potassium storage in ultrafine CF_(x): A superior cathode material for potassium batteries and its mechanism

Current studies of cathodes for potassium batteries(PBs) mainly focus on the intercalation-type materials.The conversion-type materials that possess much higher theoretical capacities are rarely discussed in previous literatures.In this work,carbon fluoride(CF_x) is reported as a high capacity conversion-type cathode for PBs for the first time.The material delivers a remarkable discharge capacity of>250 mAh g^(-1) with mid-voltage of 2.6 V at 20 mA g^(-1).Moreover,a highly reversible capacity of around 95 mAh g^(-1) is achieved at 125 mA g^(-1) and maintained for 900 cycles,demonstrating its excellent cycling stability.The mechanism of this highly reversible conversion reaction is further investigated by nuclear magnetic resonance spectra,X-ray diffraction,and transmission electron microscopy studies.According to the analyses,the C-F bond in the cycled material is different from that in the pristine state,which presents relatively higher reversibility.This finding offers important insights for further improving the performance of the CF_x.This work not only demonstrates the CF_x as a high performance cathode for PBs,but also paves a new avenue of exploring conversion-type cathodes for high energy density PBs.

Passively Q-switched S-band thulium fluoride fiberlaser with multi-walled carbon nanotube

A stable, passively Q-switched thulium fluoride fiber laser（TFFL） using a multi-walled carbon nanotube（MWCNT）-based saturable absorber（SA） for operation in the S-band region is proposed and demonstrated.The proposed TFFL has a central lasing wavelength of 1486.4 nm and an input power range of 87.1–126.6 m W.The output pulses have a repetition rate and pulse width range of 30.1–40.0 k Hz and 9.0–3.2 μs, respectively,with a maximum pulse energy of 28.9 n J. This is the first time, to the author’s knowledge, of the successful demonstration of a passively Q-switched S-band TFFL using an MWCNT-based SA.

Morphology Evolution of Poly(vinylidene fluoride) Membranes during Supercritical CO_2 Assisted Phase Inversion

A supercritical carbon dioxide（Sc CO2） assisted phase inversion was developed to produce microporous poly（vinylidene fluoride）（PVDF） membranes whose morphology characteristics arise from both liquid-liquid demixing and solid-liquid demixing（crystallization）. This result was confirmed by Fourier transform infrared spectroscopy（FTIR）, from which both α and β crystals were found. As revealed by contact angle experiment, the PVDF membranes prepared via Sc CO2 assisted phase inversion were more hydrophobic compared with the control membrane produced via conventional immersionprecipitation technique. In particular, the sample with 15 wt% PVDF prepared at 45 °C and 13 MPa exhibited a contact angle of 142°, which was mainly caused by the multilevel micro- and nano- structure. The effects of polyethylene glycol（PEG）, polyvinyl pyrrolidone（PVP） and lithium chloride（Li Cl） on the structures and crystal form were investigated. PVP promoted the formation of β phase crystal form, while PEG boosts the evolution of α phase. Li Cl restrained the crystallization degree of PVDF membrane under Sc CO2.

Gradient CNT/PVDF piezoelectric composite with enhanced force-electric coupling for soccer training

Real-time monitoring of ball–shoe interactions can provide essential information for high-quality instruction in personalized soccer training,yet existing monitoring systems struggle to reflect specific forces,loci,and durations of action.Here,we design a self-powered piezoelectric sensor constructed by the gradient carbon nanotube/polyvinylidene fluoride(CNT/PVDF)composite to monitor the interactions between the ball and the shoe.Two-dimensional Raman mapping demonstrates the gradient structure of CNT/PVDF prepared by programmable electrospinning combined with a hot pressing.Benefitting from the synergistic effect of local polarization caused by the enrichment of CNT and the reduced diffusion of silver patterns in gradient structure,the as-prepared composite exhibits enhanced force-electric coupling with an excellent sensitivity of 80 mV/N and durability over 15,000 cycles.On this basis,we conformally attach a 3×3 sensor array to a soccer shoe,enabling real-time acquisition of kick position and contact force,which could provide quantitative assessment and personalize guidance for the training of soccer players.This self-powered piezoelectric sensor network system offers a promising paradigm for wearable monitoring under strong impact forces.

Fluorinated graphite nanosheets for ultrahigh-capacity lithium primary batteries

For better performances of Ni-based catalysts at low temperatures,Ni/SiC catalyst doped with a little amount of additive La was successfully prepared.The catalytic CO methanation activity tests showed that 3%La-Ni/SiC catalyst was excellent at a low reaction temperature(95.9%CO conversion and 85.1%CH4 selectivity at250℃)with a superior stability compared with Ni/SiC(3.4%CO conversion and 0%CH4 selectivity at 250℃).This can be attributed to that the addition of La can markedly improve the dispersibility of active metal Ni and reduce the particle sizes of Ni nanoparticles or clusters,and can also regulate the interaction between active components and supports.Moreover,the high thermal conductivity and thermal stability could avoid the generation of hot spots in the catalyst bed.These results will promote the development of highly active Ni-based catalysts for the low-temperature methanation reaction.