Progress and perspectives on two-dimensional silicon anodes for lithium-ion batteries

Silicon(Si)anodes with extremely high theoretical capacities are considered indispensable for next-generation high-energy lithium-ion batteries(LIBs).However,several intractable problems,including pulverization,poor electrical contact,and continuous side reactions caused by the large volume change of Si during lithia-tion/delithiation,lead to a short cycle life and poor rate capability,thus hindering the commercial use of Si anodes in LIBs.Two-dimensional(2D)Si with a unique graphene-like structure has a short ion diffusion path-way,small volume change during lithiation,and efficient redox site utilization,making it more promising than bulk Si or Si with other versatile structures for use in LIBs.Theoretical analysis demonstrated that the low energy barrier on the surface of 2D Si accelerates the transport of Li+.However,the issues surrounding 2D Si,includ-ing the tedious and user-unfriendly synthesis,ease of restacking,and atmospheric sensitivity,limit its practical applications,which are discussed in this review.Furthermore,possible solutions to these remaining challenges and new directions are provided,with the aim of designing practical and high-performance 2D Si anodes for next-generation LIBs.

Advanced all-solid-state lithium-selenium batteries enabled by selenium-nitrogen doped hierarchic meso-microporous carbon nanospheres composite cathode

Selenium,an element belonging to the same group in the periodic table as sulfur,has a high electronic conductivity(1×10^(-5)S/cm)and a high volumetric energy density(3253 mA h/cm^(3)),which is a prospective cathode material for high-energy all-solid-state rechargeable batteries.However,its wide use is hindered by large volume expansion and low utilization rate.In this work,Se-infused nitrogen-doped hierarchical meso-microporous carbon composites(Se/NHPC)are prepared by a melt-diffusion process.Amorphous Se is uniformly dispersed in meso-micropores of NHPC with a high mass loading of 81%.All-solid-state Li-Se batteries fabricated by using Se/NHPC as the cathode,a Li-In alloy as the anode,and Li_(6)PS_(5)Cl as the solid-state electrolyte,deliver a highly reversible capacity of 621 m Ah/g(92%of theoretical capacity),a good rate capability and a high capacity retention value of 80.9%after 100 cycles.It is found that the capacity decay of Se cathode is mainly related to the interfacial degradation and the separation of Se from the carbon substrate,as suggested by the continuous increase of interfacial resistance and the structural transformation from amorphous Senchains to Se8rings initial discharge/charge cycle and then to the trigonally crystalline Se chains structure after the long-term cycles.

Nitrogen and phosphorous co-doped hierarchical meso–microporous carbon nanospheres with extraordinary lithium storage for highperformance lithium-ion capacitors

Lithium-ion capacitors(LICs),consisting of a battery-like negative electrode and a capacitive porous-carbon positive electrode,deliver more than twice the energy density of electric double-layer capacitors.However,their wide application suffers from low energy density and reduced cycle life at high rates.Herein,hierarchical meso±microporous carbon nanospheres with a highly disordered structure and nitrogen/phosphorous co-doped properties were synthesized through a facile template method.Such hierarchical porous structure facilitates rapid ion transport,and the highly disordered structure and high heteroatom content provide abundant active sites for Li+charge storage.Electrochemical experiments demonstrated that the carbon nanosphere anode delivers large reversible capability,greatly improves rate capability and exhibits excellent cycle stability.An LIC fabricated with the carbon nanosphere anode and an activated carbon cathode yields a high energy density of 103 W h kg^(-1),an extremely high power density of 44,630 W kg^(-1),and longterm cyclability of over 10,000 cycles.This work presents how structural control of carbon materials at the nano/atomic scale can significantly enhance electrochemical performance,enabling new opportunities for the design of high-performance energy-storage devices.

A high-performance potassium-ion capacitor based on a porous carbon cathode originated from the Aldol reaction product

Potassium-ion capacitors(KICs) emerge as a promising substitute for the well-developed lithium-ion capacitors(LICs),however,the energy density of KICs is below expectations because of lacking a suitable electrical double-layer positive electrode.Using chemical activation of the Aldol reaction product of acetone with KOH,we synthesized a porous ca rbon with a Brunauer-Emmett-Teller surface area of up to 2947 m2/g and a narrow pore size distribution ranging from 1 nm to 3 nm.Half-cell(versus potassium metal) test demonstrates that this porous carbon has high capacitive performance in K+ based organic electrolytes.Furthermore,a novel KIC fabricated by this porous carbon as the cathode,yields high values of energy density and power density.The processes used to make this porous carbon are readily low-cost to fabricate metal-ion capacitors.