Tuning Li/Ni mixing by reactive coating to boost the stability of cobalt-free Ni-rich cathode

Cobalt-free cathode materials are attractive for their high capacity and low cost,yet they still encounter issues with structural and surface instability.AlPO_(4),in particular,has garnered attention as an effective stabilizer for bulk and surface.However,the impact of interfacial reactions and elemental interdiffusion between AlPO_(4) and LiNi_(0.95)Mn_(0.05)O_(2) upon sintering on the bulk and surface remains elusive.In this study,we demonstrate that during the heat treatment process,AlPO_(4) decomposes,resulting in Al doping into the bulk of the cathode through elemental interdiffusion.Simultaneously,PO_(4)^(3-)reacts with the surface Li of material to form a Li_3PO_(4) coating,inducing lithium deficiency,thereby increasing Li/Ni mixing.The suitable Li/Ni mixing,previously overlooked in AlPO_(4) modification,plays a pivotal role in stabilizing the bulk and surface,exceeding the synergy of Al doping and Li_3PO_(4) coating.The presence of Ni^(2+)ions in the lithium layers contributes to the stabilization of the delithiated structure via a structural pillar effect.Moreover,suitable Li/Ni mixing can stabilize the lattice oxygen and electrode-electrolyte interface by increasing oxygen removal energy and reducing the overlap between the Ni^(3+/4+)e_g and O^(2-)2p orbitals.These findings offer new perspectives for the design of stable cobalt-free cathode materials.

Blue-shifted and naked-eye recognition of H_(2)PO_(4)- and acetylacetone based on a luminescent metal-organic framework with new topology and good stability

Fluorescence detecting both organic and inorganic analytes has aroused tremendous scientific interests, because fluorescence techniques have high sensitivity and are easy to operate. A new threedimensional(3D) MOF {[(CH_(3))_(2)NH_(2)][Zn_(3)(bbip)(BTDI)1.5(OH)]·DMF·MeOH·3H_(2)O}n(JXUST-13, bbip = 2,6-bis(benzimidazol-1-yl)pyridine and H_(4)BTDI = 5,5-(benzo[c][1,2,5]thiadiazole-4,7-diyl)diisophthalic acid)with new 4,4,8-connceted topology has been successfully synthesized and structurally characterized. Importantly, JXUST-13 could recognize H_(2)PO_(4)-and acetylacetone(Acac) by obvious fluorescence blue shift and slight enhancement with the detection limits of 2.70 μmol/L and 0.21 mmol/L, respectively. In addition, JXUST-13 exhibits relatively good thermal stability, chemical stabilities as well as reusability, and the analytes could be distinguished by naked eye and fluorescence test paper. Remarkably, JXUST-13 is the first dual-responsive MOF sensor based on fluorescence blue shift for the detection of H_(2)PO_(4)-and Acac with good selectivity in a handy, economic, and environmentally friendly manner.

Keggin and Dawson polyoxometalates as electrodes for flexible and transparent piezoelectric nanogenerators to efficiently utilize mechanical energy in the environment

In recent years,piezoelectric nanogenerators(PENGs)have been developed as a promising energyharvesting electronic device.However,the electrodes of most PENGs devices are precious metals,thus increasing the production cost.Here,we propose a flexible transparent PENGs with polyoxometalates(POMs)as the electrodes;it can effectively utilize ambient mechanical energy to generate electricity.Five types of polyoxometalates with different structures and compositions are selected as the electrode materials for PENGs for the first time,and the output performance of different PENGs electrode devices is tested.The PENG device with(NH4)6 P2 Mo18 O62 as the electrode can steadily provide a high electric output with an open-circuit voltage of 2.8 m V and a short-circuit current of 8.5 mA at the bending degree of90°.At the same time,the transmission spectrum shows that the average visible transmittance(AVT)of PENG can reach 31%,thus outperforming the benchmark for window applications.Finally,the working mechanism,force analysis,repeatability,and stability of PENG are systematically evaluated.All the studies show that this flexible transparent device has potential application prospect in wearable electronic devices.

2D Cd-MOF and its mixed-matrix membranes for luminescence sensing antibiotics in various aqueous systems and visible fingerprint identifying

The abuse of antibiotics has brought great harm to the human living environment and health,so it is extremely significant to develop an efficient and simple method to detect trace antibiotic residues in various wastewaters.Herein,a new two-dimensional(2D)Cd-based metal−organic framework(Cd-MOF,namely LCU-111)and its mixed matrix membranes(MMMs)is sifted as luminescence sensors for efficient monitoring antibiotic nitrofurazone(NFZ)in various aqueous systems and applied as visible fingerprint identifying.The LCU-111 has good selectivity,sensibility,reproducibility and anti-interference for luminescent quenching NFZ with low detection limits(LODs)of 0.4567,0.3649 and 0.8071 ppm in aqueous solution,HEPES biological buffer,and real urban Tuhai River water,respectively.Interestingly,the luminescent test papers and MMMs allow the NFZ sensing easier and more rapid by naked eyes,only with a low LOD of 0.8117 ppm for MMMs sensor.Notably,by combining multiple experiments with density functional theory(DFT)calculations,the photo-induced electron transfer(PET)quenching mechanism is further elucidated.More importantly,potential practical applications of LCU-111 for latent fingerprint visualization provide lifelike evidences for effective identification of individuals,which can be applied in criminal investigation.

Solvent-and metal-directed lanthanide-organic frameworks based on pamoic acid:observation of slow magnetization relaxation,magnetocaloric effect and luminescent sensing

Two types of lanthanide coordination polymers, namely, [Ln（PA）（NO3）（DMA）3]n （Ln=Gd （1）, Dy （2）, Eu （3）, Tb （4）） （type I）, and {[Ln2（PA）3（DMF）4]＇2DMF} （Ln=Eu （5）, Tb （6）） （type II） （PA=Pamoic acid, DMA=dimethylacetamide, DMF=N,N-dimethylformamide）, have been synthesized by the reaction of Ln（NO3）a-6H20 with pamoic acid through layer diffusion method. These complexes were characterized by single crystal X-ray diffraction, infrared spectroscopy （IR）, thermogravimetric analysis （TGA）, fluorescence and magnetic measurements. Solvents and lanthanide atoms in the reaction play an important role in controlling different structures. Type I demonstrated 1-D linear chain structure connected by Ln atoms and PA ligands. Type II exhibited non-interpenetrating 3-D 6-connected 43612 nets based on binuclear [Ln2（CO2）6（DMF）4] cores. Magnetic properties of complexes 1-4 were investigated in details. Complex 1 shows significant magnetocaloric effect with -△Sm=20.37 J kg^-1 K^-1 at 3.0 K and 7 T. Complex 2 exhibits slow relaxation of the magnetization. Complexes 3-6 exhibit both ligand- and metal-centered fluorescent properties. Complex 6 demonstrates fluorescent sensing of DMF and Cu^2＋ ion.