Electrochemical activation of oxygen atom of SnO2 to expedite efficient conversion reaction for alkaline-ion(Li+/Na+/K+)storages

SnO2-based anode materials have attracted much attention due to high capacity and relatively mild voltage platforms.However,limited by low initial Coulombic efficiency(ICE)and poor stability,its practical application is still challenging.Recently,it has been found that compositing carbon or metal particles with SnO2 is an effective strategy to achieve high alkaline-ion storages.Although this strategy may improve the kinetics and ICE of the electrochemical reaction,the specific mechanism has not been clearly elucidated.In this work,we found that the invalidation SnO2 may go through two steps:1)the conversion process from SnO2 to Sn and Li2O;2)the collapse of the electrode material resulted from huge volume changes during the alloyed Sn with alkaline ions.To address these issues,a unique robust Co-NC shell derived from ZIF-67 is introduced,in which the transited metallic Co nanoparticles could accelerate the decomposition of Sn-O and Li-O bonds,thus expedite the kinetics of conversion reaction.As a result,the SnO2@Co-NC electrode achieves a more complete and efficient transfer between SnO2 and Sn phases,possessing a potential to achieve high alkaline-ion(Li+/Na+/K+)storages.

MXene及其复合材料在钠/钾离子电池中的应用

MXene作为一种新型的二维层状结构材料而备受关注,MXene具有高电子传导率、较大的比面积、较好的机械性能以及独特的层状结构,已广泛应用于储能、催化、吸附等领域。近年来,MXene及其复合材料应用于二次电池领域引起了人们的广泛关注。氧化物、硫化物等材料具有高容量,但存在电导率低、反应过程中体积膨胀、循环稳定性差等问题,构建与MXene的复合材料既能提高容量又可以增强材料的电子导电率,有效缓解反应过程中体积膨胀,实现最佳的电化学性能。本文主要对MXene及其复合材料在钠离子电池和钾离子电池中的最新研究进展进行总结,简要介绍了钠离子电池、钾离子电池和MXene的研究背景,重点介绍了MXene复合材料在钠离子电池中的应用研究,主要按照硫化物、氧化物、碳材料进行分类,对其合成方法与电化学性能进行综述,同时总结了MXene复合材料在钾离子电池中的研究进展。最后本文对MXene及其复合材料的发展及其应用前景进行了总结与展望。

Stabilizing effects of atomic Ti doping on high-voltage high-nickel layered oxide cathode for lithium-ion rechargeable batteries

High-voltage high-nickel lithium layered oxide cathodes show great application prospects to meet the ever-increasing demand for further improvement of the energy density of rechargeable lithium-ion batteries(LIBs)mainly due to their high output capacity.However,severe bulk structural degradation and undesired electrode-electrolyte interface reactions seriously endanger the cycle life and safety of the battery.Here,2 mol%Ti atom is used as modified material doping into LiNi_(0.8)Co_(0.2)Mn_(0.2O2)(NCM)to reform LiNi_(0.6)Co_(0.2)Mn_(0.18)Ti_(0.02)O_(2)(NCM-Ti)and address the long-standing inherent problem.At a high cut-off voltage of 4.5 V,NCM-Ti delivers a higher capacity retention ratio(91.8%vs.82.9%)after 150 cycles and a superior rate capacity(118 vs.105 mAh·g^(-1))at the high current density of 10 C than the pristine NCM.The designed high-voltage full battery with graphite as anode and NCM-Ti as cathode also exhibits high energy density(240 Wh·kg^(-1))and excellent electrochemical performance.The superior electrochemical behavior can be attributed to the improved stability of the bulk structure and the electrode-electrolyte interface owing to the strong Ti-O bond and no unpaired electrons.The in-situ X-ray diffraction analysis demonstrates that Ti-doping inhibits the undesired H2-H3 phase transition,minimizing the mechanical degradation.The ex-situ TEM and X-ray photoelectron spectroscopy reveal that Ti-doping suppresses the release of interfacial oxygen,reducing undesired interfacial reactions.This work provides a valuable strategic guideline for the application of high-voltage high-nickel cathodes in LIBs.

CMOS-compatible all-optical modulator based on the saturable absorption of graphene

Graphene resting on a silicon-on-insulator platform offers great potential for optoelectronic devices.In the paper,we demonstrate all-optical modulation on the graphene-silicon hybrid waveguides(GSHWs)with tens of micrometers in length.Owing to strong interaction between graphene and silicon strip waveguides with compact light confinement,the modulation depth reaches 22.7%with a saturation threshold down to 1.38 pJ per pulse and a 30-μm-long graphene pad.A response time of 1.65 ps is verified by a pump-probe measurement with an energy consumption of 2.1 pJ.The complementary metal-oxide semiconductor compatible GSHWs with the strip configuration exhibit great potential for ultrafast and broadband all-optical modulation,indicating that employing two-dimensional materials has become a complementary technology to promote the silicon photonic platform.

Low-cost hybrid integrated 4 × 25 GBaud PAM-4CWDM ROSA with a PLC-based arrayed waveguide grating de-multiplexer

We demonstrate a low-cost hybrid integrated and compact 100 GBaud four-lane coarse wavelength division multiplexing (CWDM) receiver optical sub-assembly (ROSA) based on an arrayed waveguide grating de-multiplexer in the O band. To achieve the horizontal light coupling between the planar light-wave circuit (PLC) based arrayed waveguide grating de-multiplexer and photodetector array, a 42°polished facet is applied for total reflection.A flexible printed circuit with high-frequency coplanar waveguides is used for a power supply of trans-impedance amplifier and signal transmission.The fabricated CWDM ROSA module, whose size is 18mm×22mm×6mm, shows a 3 dB bandwidth of 21.2,18.4,19.6,and 19.3 GHz,respectively,in each lane. The overall symbol error rates are at a magnitude of 10^-7 for 25 GBaud four-level pulse amplitude modulation (PAM-4) transmission with an average input optical power of 5dBm.