Lithium-ion batteries(LIBs)with extreme fast charging(XFC)capability are considered an effective way to alleviate range anxiety for electric vehicle(EV)buyers.Owing to the high ionic and electronic conductivity of LiN...Lithium-ion batteries(LIBs)with extreme fast charging(XFC)capability are considered an effective way to alleviate range anxiety for electric vehicle(EV)buyers.Owing to the high ionic and electronic conductivity of LiNi_(x)Co_(y)Mn_zO_(2)(x+y+z=1,NCM)cathodes,the inevitable Li plating of graphite in NCM|graphite cell is usually identified as a key bottleneck for XFC LIBs.However,the capacity decay mechanism of cathode materials under XFC has not been fully investigated.In this work,three typical NCM cathode materials with different Ni fractions were chosen and their electrochemical performances under XFC associated with structural evolution were investigated.A faster capacity decay of NCMs under XFC conditions is observed,especially for Ni-rich NCMs.In-situ X-ray diffraction(XRD)reveals that the multiple caxis parameters appear at the high-voltage regions in Nirich NCMs,which is probably triggered by the larger obstruction of Li(de)intercalation.Particularly,NCMs with moderate Ni fraction also present a similar trend under XFC conditions.This phenomenon is more detrimental to the structural and morphological stability,resulting in a faster capacity decay than that under low current charging.This work provides new insight into the degradation mechanism of NCMs under XFC conditions,which can promote the development of NCM cathode materials with XFC capability.展开更多
Using compounds modified by the isotopes carbon-13 and nitrogen-15 helps conduct research in various fields of science, such as medicine, pharmacology, pharmacokinetics, metabolism, agriculture, and others. In the cas...Using compounds modified by the isotopes carbon-13 and nitrogen-15 helps conduct research in various fields of science, such as medicine, pharmacology, pharmacokinetics, metabolism, agriculture, and others. In the case of the availability of reliable, express, and cheap methods, the area of their use will gradually expand. A determination of the atomic fraction of the isotopes carbon-13 and nitrogen-15 directly in glycine, leucine, isoleucine, and alanine is proposed;the modification concerns all centers or one or more identical carbon and nitrogen centers separately, as well as both isotopes at the same time. There are defined mass lines of the mass spectrum of each amino acid, through which the isotopic content of carbon and nitrogen is calculated. The processes that must be taken into account for the determination of the isotopic content are also established. Isotopic analysis of these compounds until now was carried out by transforming them into carbon oxide, dioxide, and molecular nitrogen, and determination of their content in individual centers was impossible.展开更多
Readout electronics is developed for a prototype time-of-flight(TOF) ion composition spectrometer for in situ measurement of the mass/charge distributions of major ion species from 200 to 100 ke V/e in space plasma.By...Readout electronics is developed for a prototype time-of-flight(TOF) ion composition spectrometer for in situ measurement of the mass/charge distributions of major ion species from 200 to 100 ke V/e in space plasma.By utilizing a constant fraction discriminator(CFD) and time-to-digital converter(TDC), challenging dynamic range measurements were performed with high time resolution and event rates. CFD was employed to discriminate the TOF signals from the micro-channel plate and channel electron multipliers. TDC based on the combination of counter and OR-gate delay chain was designed in a highreliability flash field programmable gate array. Owing to the non-uniformity of the delay chain, a correction algorithm based on integral nonlinearity compensation was implemented to reduce the time uncertainty. The test results showed that the electronics achieved a low timingerror of < 200 ps in the input range from 35 to 500 m V for the CFD, and a time resolution of ～550 ps with time uncertainty < 180 ps after correction and a time range of6.4 ls for the TDC. The TOF spectrum from an electron beam experiment of the impacting N_2 gas further indicated the good performance of this readout electronic.展开更多
基金financially supported by the National Key R&D Program of China(No.2020YFA0406203)Shenzhen Science and Technology Innovation Commission(Nos.JCYJ20180507181806316,JCYJ20200109105618137 and SGDX2019081623240948)+1 种基金the ECS scheme(Nos.City U21307019,7005500,7005615,7005612 and 7020043)Shenzhen Research Institute,City University of Hong Kong。
文摘Lithium-ion batteries(LIBs)with extreme fast charging(XFC)capability are considered an effective way to alleviate range anxiety for electric vehicle(EV)buyers.Owing to the high ionic and electronic conductivity of LiNi_(x)Co_(y)Mn_zO_(2)(x+y+z=1,NCM)cathodes,the inevitable Li plating of graphite in NCM|graphite cell is usually identified as a key bottleneck for XFC LIBs.However,the capacity decay mechanism of cathode materials under XFC has not been fully investigated.In this work,three typical NCM cathode materials with different Ni fractions were chosen and their electrochemical performances under XFC associated with structural evolution were investigated.A faster capacity decay of NCMs under XFC conditions is observed,especially for Ni-rich NCMs.In-situ X-ray diffraction(XRD)reveals that the multiple caxis parameters appear at the high-voltage regions in Nirich NCMs,which is probably triggered by the larger obstruction of Li(de)intercalation.Particularly,NCMs with moderate Ni fraction also present a similar trend under XFC conditions.This phenomenon is more detrimental to the structural and morphological stability,resulting in a faster capacity decay than that under low current charging.This work provides new insight into the degradation mechanism of NCMs under XFC conditions,which can promote the development of NCM cathode materials with XFC capability.
文摘Using compounds modified by the isotopes carbon-13 and nitrogen-15 helps conduct research in various fields of science, such as medicine, pharmacology, pharmacokinetics, metabolism, agriculture, and others. In the case of the availability of reliable, express, and cheap methods, the area of their use will gradually expand. A determination of the atomic fraction of the isotopes carbon-13 and nitrogen-15 directly in glycine, leucine, isoleucine, and alanine is proposed;the modification concerns all centers or one or more identical carbon and nitrogen centers separately, as well as both isotopes at the same time. There are defined mass lines of the mass spectrum of each amino acid, through which the isotopic content of carbon and nitrogen is calculated. The processes that must be taken into account for the determination of the isotopic content are also established. Isotopic analysis of these compounds until now was carried out by transforming them into carbon oxide, dioxide, and molecular nitrogen, and determination of their content in individual centers was impossible.
基金supported by the National Key Scientific Instrument and Equipment Development Projects of the National Natural Science Foundation of China(No.41327802)China Mars Project
文摘Readout electronics is developed for a prototype time-of-flight(TOF) ion composition spectrometer for in situ measurement of the mass/charge distributions of major ion species from 200 to 100 ke V/e in space plasma.By utilizing a constant fraction discriminator(CFD) and time-to-digital converter(TDC), challenging dynamic range measurements were performed with high time resolution and event rates. CFD was employed to discriminate the TOF signals from the micro-channel plate and channel electron multipliers. TDC based on the combination of counter and OR-gate delay chain was designed in a highreliability flash field programmable gate array. Owing to the non-uniformity of the delay chain, a correction algorithm based on integral nonlinearity compensation was implemented to reduce the time uncertainty. The test results showed that the electronics achieved a low timingerror of < 200 ps in the input range from 35 to 500 m V for the CFD, and a time resolution of ～550 ps with time uncertainty < 180 ps after correction and a time range of6.4 ls for the TDC. The TOF spectrum from an electron beam experiment of the impacting N_2 gas further indicated the good performance of this readout electronic.
