Composites of Graphene and LiFePO_4 as Cathode Materials for Lithium-Ion Battery:A Mini-review

This mini-review highlights selectively the recent research progress in the composites of Li Fe PO4 and graphene. In particularly, the different fabrication protocols, and the electrochemical performance of the composites are summarized in detail. The structural and morphology characters of graphene sheets that may affect the property of the composites are discussed briefly. The possible ongoing researches in area are speculated upon.

Sacrificial template synthesis of(V_(0.8)Ti_(0.1)Cr_(0.1))_(2)AlC and carbon fiber@(V_(0.8)Ti_(0.1)Cr_(0.1))_(2)AlC microrods for efficient microwave absorption

The morphology of MAX phase powders significantly influences their microwave absorption properties.However,the traditional synthesis via solid-state reactions produces irregular powders,and the preparation of MAX phase powders with specific morphology remains a challenge.Herein,(VTiCr)Al C MAX phase microrods were fabricated for the first time in NaCl/KCl molten salts using vanadium,titanium,chromium,aluminum,and short carbon fibers as precursors.It was found that despite acting as a carbon source,carbon fibers also acted as sacrificial templates.By adjusting the molar ratio of metal powders and short carbon fibers,a series of carbon fiber@(V_(0.8)Ti_(0.1)Cr_(0.1))_(2)AlC microrods with core-sheath structure were also obtained.Carbon fiber@(V_(0.8)Ti_(0.1)Cr_(0.1))_(2)AlC microrods with a molar ratio of 8:2 showed the optimum microwave absorption performance.The reflection loss(RL)value reached up to–63.26 d B at 2.40 mm,and the effective absorption bandwidth(EAB)was about 5.28 GHz with a thickness of2.02 mm.Based on the electromagnetic parameter analysis and theoretical simulation,the enhanced microwave absorption performance was attributed to the synergistic effect of different factors like dielectric loss,magnetic loss,multiple reflection,and scattering.This work offers a facile route to modulate the morphology of MAX phase powders and may accelerate its application as microwave absorbers.

SnP entangled by carbon nanotube networks as anode for pseudocapacitive half/full battery

Due to the lower operating voltage and higher theoretical specific capacity,tin phosphide is considered a class of materials with prospects as an anode material for lithium-ion batteries(LIBs).Among them,tin monophosphide has attracted people's attention due to its unique layered structure.Unfortunately,because of the challenging synthesis method and metastable nature,the application of SnP is limited.In this work,tin phosphide/carbon nanotubes(SnP/CNTs)are prepared by controlling the nucleation and adjusting the ratio of phosphorus/carbon using carbon nanotube as initiator.Sn-MOF is used as a template to make the morphology of SnP more evenly,and carbon nanotubes can also be used as a conductive network to increase the speed of electron transmission.As an anode material for LIBs,SnP/CNTs reveals superior rate performances(reversible capability of 610 mA·h·g^(-1)at 2000 mA·g^(-1)).The full-cell was assembled and tested,after 50 cycles at 0.1 C,the capacity can maintain 292 mA·h·g^(-1),and its capacity retention rate can reach 80.5%.After 230 cycles,its capacity can maintain at around 223 mA·h·g
1.In addition,SnP/CNTs materials exhibit 89%pseudocapacitance contribution upon cycling,which indicates the robust Lit storage and satisfactory fast-charging capability.Hence,SnP/CNTs suggests a promising anode material for energy storage system.

Facile synthesis of hollow Ti_(3)AlC_(2)microrods in molten salts via Kirkendall effect

The microstructure and morphology of Ti_(3)AlC_(2)powders not only affect the preparation of Ti_(3)C_(2) MXene but also have a great influence on their potential applications,such as microwave absorbers,alloy additives,or catalytic supports.However,the synthesis of Ti_(3)AlC_(2)powders with desired microstructure and morphology remains a challenge.Herein,hollow Ti_(3)AlC_(2)microrods were prepared for the first time in NaCl/KCl molten salts by using titanium,aluminum,and short carbon fibers as starting materials.It was found that the short carbon fibers not only performed as carbon source but also acted as sacrificial template.Furthermore,it was revealed that TiC and Ti2AlC were initially formed on the surface of carbon fibers.The subsequent reactions between the outer Ti,Al and the inner carbon were dominated by the Kirkendall effect which gave rise to the formation of a hollow structure.Based on this mechanism,hollow Ti_(3)AlC_(2)microspheres and a series of hollow TiC,Ti_(2)AlC,and V_(2)AlC powders were also successfully fabricated.This work provides a facile route to synthesize hollow MAX phases and may give enlightenment on preparing other hollow carbide powders via the Kirkendall effect in the molten salts.

Carbon polyhedra encapsulated Si derived from Co-Mo bimetal MOFs as anode materials for lithium-ion batteries

Silicon(Si)holds promise as an anode material for lithium-ion batteries(LIBs)as it is widely avail-able and characterized by high specific capacity and suitable working potential.However,the relatively low electrical conductivity of Si and the significantly high extent of volume expansion realized dur-ing lithiation hinder its practical application.We prepared N-doped carbon polyhedral micro cage en-capsulated Si nanoparticles derived from Co-Mo bimetal metal-organic framework(MOFs)(denoted as Si/CoMo@NCP)and explored their lithium storage performance as anode materials to address these prob-lems.The Si/CoMo@NCP anode exhibited a high reversible lithium storage capacity(1013 mAh g^(−1)at 0.5 A g^(−1)after 100 cycles),stable cycle performance(745 mAh g^(−1)at 1 A g^(−1)after 400 cycles),and excellent rate performance(723 mAh g^(−1)at 2 A g^(−1)).Also,the constructed the full-cell NCM 811//Si/CoMo@NCP exhibited well reversible capacity.The excellent electrochemical performances of Si/CoMo@NCP were at-tributed to two unique properties.The encapsulation of NCP with doped nitrogen and porous structural carbon improves the electrical conductivity and cycling stability of the molecules.The introductions of metallic cobalt and its oxides help to improve the rate capability and lithiation capacity of the materials following multi-electron reaction mechanisms.

Fe_(2)Mo_(3)O_(8) nanoparticles self-assembling 3D mesoporous hollow spheres toward superior lithium storage properties

Unique self-assembled iron(II)molybdenum(IV)oxide(Fe_(2)Mo_(3)O_(8))mesoporous hollow spheres have been facilely constructed via the bubble-template-assisted hydrothermal synthesis method combined with simple calcination.The compact assembly of small nanoparticles on the surface of the hollow spheres not only provides more active sites for the Fe_(2)Mo_(3)O_(8),but also benefits the stability of the hollow structure,and thus improved the lithium storage properties of Fe2Mo3O8.The Fe_(2)Mo_(3)O_(8) mesoporous hollow spheres exhibit high initial discharge and charge capacities of 1189 and 997 mA∙h∙g^(−1) respectively,as well as good long-term cycling stability(866 mA∙h∙g^(−1) over 70 cycles)when used as a lithium-ion battery anode.This feasible material synthesis strategy will inspire the variation of structural design in other ternary metal molybdates.