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.

高储锂性能的氮、磷共掺杂分级多孔炭纳米球用于高比能锂离子电容器

锂离子电容器通常由一个电池型负极和一个电容型多孔炭正极组成,可输出比传统双电层电容器高两倍的能量密度,但是在高倍率条件下其能量密度低、循环寿命短,因而其广泛应用受到阻碍.本文通过模板法合成了一种结构高度无序、氮/磷共掺杂的分级介孔炭纳米球.这种分级多孔结构有利于锂离子的快速迁移,且高度无序的结构和高杂原子含量为锂离子电荷存储提供了丰富的活性位点.电化学测试表明,该炭纳米球负极具有较高比容量(在0.1 A g^(-1)时,为1108.6 mA h g^(-1)),优异的倍率性能(在8 A g^(-1)时,为276.5 mA h g^(-1)),以及良好的循环稳定性(1000次循环后仍保持85%的容量).以该分级多孔纳米球为负极,自制活性炭为正极所组装的锂离子电容器具有较高的能量密度(103 W h kg^(-1))、功率密度(44,630 W kg^(-1))以及长循环寿命(>10,000圈).该工作揭示了如何通过在纳米/原子尺度上调控炭材料微结构来提高电化学性能的方法,为设计高性能的储能设备提供了新策略.

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.