Rationally designing electrolyte additives for highly improving cyclability of LiNi_(0.5)Mn_(1.5)O_(4)/Graphite cells

High voltage is necessary for high energy lithium-ion batteries but difficult to achieve because of the highly deteriorated cyclability of the batteries.A novel strategy is developed to extend cyclability of a high voltage lithium-ion battery,LiNi_(0.5)Mn_(1.5)O_(4)/Graphite(LNMO/Graphite)cell,which emphasizes a rational design of an electrolyte additive that can effectively construct protective interphases on anode and cathode and highly eliminate the effect of hydrogen fluoride(HF).5-Trifluoromethylpyridine-trime thyl lithium borate(LTFMP-TMB),is synthesized,featuring with multi-functionalities.Its anion TFMPTMB-tends to be enriched on cathode and can be preferentially oxidized yielding TMB and radical TFMP-.Both TMB and radical TFMP can combine HF and thus eliminate the detrimental effect of HF on cathode,while the TMB dragged on cathode thus takes a preferential oxidation and constructs a protective cathode interphase.On the other hand,LTFMP-TMB is preferentially reduced on anode and constructs a protective anode interphase.Consequently,a small amount of LTFMP-TMB(0.2%)in 1.0 M LiPF6in EC/DEC/EMC(3/2/5,wt%)results in a highly improved cyclability of LNMO/Graphite cell,with the capacity retention enhanced from 52%to 80%after 150 cycles at 0.5 C between 3.5 and 4.8 V.The as-developed strategy provides a model of designing electrolyte additives for improving cyclability of high voltage batteries.

Achieving high-capacity and long-life K^(+)storage enabled by constructing yolk-shell Sb_(2)S_(3)@N,S-doped carbon nanorod anodes

As promising anode candidates for potassium-ion batteries(PIBs),antimony sulfide(Sb_(2)S_(3))possesses high specific capacity but suffers from massive volume expansion and sluggish kinetics due to the large K^(+)insertion,resulting in inferior cycling and rate performance.To address these challenges,a yolk-shell structured Sb_(2)S_(3)confined in N,S co-doped hollow carbon nanorod(YS-Sb_(2)S_(3)@NSC)working as a viable anode for PIBs is proposed.As directly verified by in situ transmission electron microscopy(TEM),the buffer space between the Sb_(2)S_(3)core and thin carbon shell can effectively accommodate the large expansion stress of Sb_(2)S_(3)without cracking the shell and the carbon shell can accelerate electron transport and K^(+)diffusion,which plays a significant role in reinforcing the structural stability and facilitating charge transfer.As a result,the YS-Sb_(2)S_(3)@NSC electrode delivers a high reversible K^(+)storage capacity of 594.58 m A h g^(-1)at 0.1 A g^(-1)and a long cycle life with a slight capacity degradation(0.01%per cycle)for 2000 cycles at 1 A g^(-1)while maintaining outstanding rate capability.Importantly,utilizing in in situ/ex situ microscopic and spectroscopic characterizations,the origins of performance enhancement and K^(+)storage mechanism of Sb_(2)S_(3)were clearly elucidated.This work provides valuable insights into the rational design of high-performance and durable transition metal sulfides-based anodes for PIBs.

Silk fibroin-based biopolymer composite binders with gradient binding energy and strong adhesion force for high-performance micro-sized silicon anodes

Micro-sized silicon anodes have shown much promise in large-scale industrial production of high-energy lithium batteries.However,large volume change(>300%)of silicon anodes causes severe particle pulverization and the formation of unstable solid electrolyte interphases during cycling,leading to rapid capacity decay and short cycle life of lithium-ion batteries.When addressing such issues,binder plays key roles in obtaining good structural integrity of silicon anodes.Herein,we report a biopolymer composite binder composed of rigid poly(acrylic acid)(PAA)and flexible silk fibroin(SF)tailored for micro-sized silicon anodes.The PAA/SF binder shows robust gradient binding energy via chemical interactions between carboxyl and amide groups,which can effectively accommodate large volume change of silicon.This PAA/SF binder also shows much stronger adhesion force and improved binding towards high-surface/defective carbon additives,resulting in better electrochemical stability and higher coulombic efficiency,than conventional PAA binder.As such,micro-sized silicon/carbon anodes fabricated with novel PAA/SF binder exhibit much better cyclability(up to 500 cycles at 0.5 C)and enhanced rate capability compared with conventional PAA-based anodes.This work provides new insights into the design of functional binders for high-capacity electrodes suffering from large volume change for the development of nextgeneration lithium batteries.

Depolarization of Li-rich Mn-based oxide via electrochemically active Prussian blue interface providing superior rate capability

The high-rate cyclability of Li-rich Mn-based oxide(LMO)is highly limited by the electrochemical polarization resulting from the slow kinetic of the Li2MnO3 phase.Herein,the Prussian blue(PB)coating layer with specific redox potential is introduced as a functionalized interface to overcome the side effect and the escaping of O on the surface of LMO,especially its poor rate capability.In detail,the PB layer can restrict the large polarization of LMO by sharing overloaded current at a high rate due to the synchronous redox of PB and LMO.Consequently,an enhanced high rate performance with capacity retention of 87.8%over 300 cycles is obtained,which is superior to 50.5%of the pristine electrode.Such strategies on the high-rate cyclability of Li-rich Mn-based oxide compatible with good low-rate performances may attract great attention for pursuing durable performances.

KOH activated carbon derived from biomass-banana fibers as an efficient negative electrode in high performance asymmetric supercapacitor

Here we demonstrate the fabrication, electrochemical performance and application of an asymmetric supercapacitor (AS) device constructed with ss-Ni(OH)(2)/MWCNTs as positive electrode and KOH activated honeycomb-like porous carbon (K-PC) derived from banana fibers as negative electrode. Initially, the electrochemical performance of hydrothermally synthesized ss-Ni(OH)(2)/MWCNTs nanocomposite and K-PC was studied in a three-electrode system using 1 M KOH. These materials exhibited a specific capacitance (Cs) of 1327 Fig and 324 F/g respectively at a scan rate of 10 mV/s. Further, the AS device i.e., ss-Ni(OH)(2)/MWCNTs// K-PC in 1 M KOH solution, demonstrated a Cs of 156 F/g at scan rate of 10 mV/s in a broad cell voltage of 0-2.2 V. The device demonstrated a good rate capability by maintaining a Cs of 59 F/g even at high current density (25 A/g). The device also offered high energy density of 63 Wh/kg with maximum power density of 5.2 kW/kg. The AS device exhibited excellent cycle life with 100% capacitance retention at 5000th cycle at a high current density of 25 A/g. Two AS devices connected in series were employed for powering a pair of LEDs of different colors and also a mini fan. (C) 2016 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier B.V. and Science Press. All rights reserved.

Boosting lithium batteries under harsh operating conditions by a resilient ionogel with liquid-like ionic conductivity

New chemistries are being developed to increase the capacity and power of rechargeable batteries. However, the risk of safety issues increases when high-energy batteries using highly active materials encounter harsh operating conditions. Here we report on the synthesis of a unique ionogel electrolyte for abuse-tolerant lithium batteries. A hierarchically architected silica/polymer scaffold is designed and fabricated through a facile soft chemistry route, which is competent to confine ionic liquids with superior uptake ability (92.4 wt%). The monolithic ionogel exhibits high conductivity and thermal/mechanical stability, featuring high-temperature elastic modulus and dendrite-free lithium cycling. The Li/LiFePO_(4) pouch cells achieve outstanding cyclability at different temperatures up to 150 ℃, and can sustain cutting, crumpling, and even coupled thermal–mechanical abuses. Moreover, the solid-state lithium batteries with LiNi_(0.60)Co_(0.20)Mn_(0.20)O_(2), LiNi_(0.80)Co_(0.15)Al_(0.05)O_(2), and Li_(1.2)Mn_(0.54)Ni_(0.13)Co_(0.13)O_(2) cathodes demonstrate excellent cycle performances at 60 ℃. These results indicate that the resilient and high-conductivity ionogel electrolyte is promising to realize high-performance lithium batteries with high energy density and safety.

Three-dimensional ordered hierarchically porous carbon materials for high performance Li-Se battery

Developing host materials with high specific surface area, good electron conductivity, and fast ion transportation channel is critical for high performance lithium-selenium(Li-Se) batteries. Herein, a series of three dimensional ordered hierarchically porous carbon(3D OHPC) materials with micro/meso/macropores are designed and synthesized for Li-Se battery. The porous structure is tuned by following the concept of the generalized Murray’s law to facilitate the mass diffusion and reduce ion transport resistance.The optimized 3D Se/OHPC cathode exhibits a very high 2 nd discharge capacity of 651 m Ah/g and retains 361 m Ah/g after 200 cycles at 0.2 C. Even at a high current rate of 5 C, the battery still shows a discharge capacity as high as 155 m Ah/g. The improved electrochemical performance is attributed to the synergy effect of the interconnected and well-designed micro, meso and macroporosity while shortened ions diffusion pathways of such Murray materials accelerate its ionic and electronic conductivities leading to the enhanced electrochemical reaction. The diffusivity coefficient in Se/OHPC can reach a very high value of 1.3 × 10^(-11)cm^(2)/s, much higher than those in single pore size carbon hosts. Their effective volume expansion accommodation capability and reduced dissolution of polyselenides ensure the high stability of the battery. This work, for the first time, established the clear relationship between textural properties of cathode materials and their performance and demonstrates that the concept of the generalized Murray’s law can be used as efficient guidance for the rational design and synthesis of advanced hierarchically porous materials and the great potential of 3D OHPC materials as a practical high performance cathode material for Li-Se batteries.

Tris(trimethylsilyl) borate as an electrolyte additive for high-voltage lithium-ion batteries using LiNi_(1/3)Mn_(1/3)Co_(1/3)O_2 cathode

The influence of tris(trimethylsilyl) borate (TMSB) as an electrolyte additive on lithium ion cells have been studied using Li/LiCo1/3Ni1/3Mn1/3O2 cells at a higher voltage, 4.7 V versus Li/Li+. 1 wt% TMSB can dramatically reduce the capacity fading that occurs during cycling at room temperature (RT) and elevated temperature (60 degrees C). After 150 cycles at 1 C rate (1 C= 278 mAh/g), the capacity retention of Li/LiCo1/3Ni1/3Mn1/3O2 is up to near 72% in the electrolyte with TMSB added, while it is only about 35% in the baseline electrolyte. The electrochemical behaviors, the surface chemistry and structure of Li/LiCo1/3Ni1/3Mn1/3O2 cathode are characterized with charge/discharge test, linear sweep voltammetry (LSV), X-ray photoelectron spectroscopy (XPS), electrochemical impedance spectroscopy (EIS), thermal gravimetric analyses (TGA), scanning electron microscope (SEM) and transmission electron microscopy (TEM). These analysis results reveal that the addition of TMSB is able to protectively modify the electrode CEI film in a manner that suppresses electrolyte decomposition and degradation of electrode surface structure, even though at both a higher voltage of 4.7 V and an elevated temperature of 60 degrees C. (C) 2016 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier B.V. and Science Press. All rights reserved.

Rocking-chair ammonium ion battery with high rate and long-cycle life

Aqueous rechargeable ammonium-ion batteries(AIBs)have drew considerable attention because of their capacity for high rates,low cost,and high safety.However,developing desired electrodes requiring stable structure in the aqueous fast ammoniation/de-ammoniation becomes urgent.Herein,an ammonium ion full battery using Cu_(3)[Fe(CN)_(6)]_(2)(CuHCF)acting to be a cathode and barium vanadate(BVO)acting to be an anode is described.Its excellent electrochemical behavior of Prussian blue analogs and the perfectly matched lattice structure of NH_(4)^(+)is expected.And the open structure of vanadium compounds satisfies the fast ammoniation/de-ammoniation of NH4+is also achieved.As a result of these synergistic effects,the BVO//CuHCF full cell retains 80.5 percent of its capacity following 1000 cycling.These achievements provide new ideas for developing low-cost and long-life AIBs.

3D uniform nitrogen-doped carbon skeleton for ultra-stable sodium metal anode

Sodium metal batteries are arousing extensive interest owing to their high energy density,low cost and wide resource.However,the practical development of sodium metal batteries is inherently plagued by the severe volume expansion and the dendrite growth of sodium metal anode during long cycles under high current density.Herein,a simple electrospinning method is applied to construct the uniformly nitrogen-doped porous carbon fiber skeleton and used as three-dimensional(3D)current collector for sodium metal anode,which has high specific surface area(1,098 m^2/g)and strong binding to sodium metal.As a result,nitrogen-doped carbon fiber current collector shows a low sodium deposition overpotential and a highly stable cyclability for 3,500 h with a high coulombic effciency of 99.9%at 2 mA/cm^2 and 2 mAh/cm^2.Moreover,the full cells using carbon coated sodium vanadium phosphate as cathode and sodium pre-plated nitrogen-doped carbon fiber skeleton as hybrid anode can stably cycle for 300 times.These results illustrate an effective strategy to construct a 3D uniformly nitrogen-doped carbon skeleton based sodium metal hybrid anode without the formation of dendrites,which provide a prospect for further development and research of high performance sodium metal batteries.

High-capacity Li-rich Mn-based Cathodes for Lithium-ion Batteries

Layered Li-rich Mn-based oxides are promising cathode materials for Li-ion batteries due to their high capacity and high operation voltage.However,their commercial applications are hindered by irreversible capacity loss in the first charge-discharge process,voltage decay during cycling,inefficient cyclability and rate capability.Many attempts have been performed to solve such issues,including the mechanism study and strategies to improve the electrochemical performance.This article provides a brief review and future perspective on the main challenges of the high-capacity Li-rich Mn-based cathodes for Li-ion batteries.

Molten Salt Derived Graphene-Like Carbon Nanosheets Wrapped SiO_(x)/Carbon Submicrospheres with Enhanced Lithium Storage

There is no doubt that SiO_(x) and carbon composite is one of the promising anode materials for lithium-ion batteries owing to its high capacity and rational cycling stability.Herein,we report a sol-gel synthesis followed by molten salt carbonization route to fabricate graphene-like carbon nanosheet wrapped SiO_(x)/C submicrospheres(SiO_(x)/C@2D-C).The in-situ generated carbon nanosheets under molten salt condition can further improve the electroconductivity,restrain the volumetric expansion and guarantee the structural integrity of the electrode.As a result,the as-obtained SiO_(x)/C@2D-C delivers a discharge capacity of 559 mAh·g^(-1) at 0.5 A·g^(-1) after 200 cycles and 548 mAh·g^(-1) at 1.0 A·g^(-1) even after 1000 cycles.The full cell assembled with SiO_(x)/C@2D-C as anode and commercial LiFeP0_(4) as cathode can achieve an energy density of 200 Wh·kg^(-1) and maintain a capacity of 66.7% after 100 cycles with a working potential of 2.8 V.The approach is simple and cost effective,which is promising for mass production of SiO_(x)-based materials for high energy LIBs.

LiF引发选择性锂化提升硅碳负极可逆容量

Si@SiO_(x)/C复合负极具有较高比容量,被认为是锂离子电池实际工业应用中最有前途的负极材料.然而,由于硅的严重体积形变,复合负极的循环稳定性依然面临巨大挑战.本工作通过释放负极冗余容量中高度可逆的锂储存能力,提高了复合负极的循环稳定性.基于LiF与不同活性材料之间的界面分离能差,我们针对复合负极提出了一种LiF引发的选择性锂化策略.LiF在Si@SiO_(x)上发生再沉积并富集,分离LiC_(x)和Li_(15)Si_(4)的形成电位,进而促进锂离子在石墨中的存储(未修饰前复合负极中石墨的容量未被充分利用).因此,在不牺牲比容量的前提下,全电池获得了更好的倍率性能和循环性能.超高面容量(NCA/S450,4.9 mA h cm^(-2))的全电池经300次循环后,容量保持率从66.1%显著提高到94.2%.选择性锂化策略在实际工业应用中更加可行,不需要改变现有的电池制造工艺.本研究为长循环寿命硅/石墨复合负极的开发开辟了新途径.

Facile preparation of unique three-dimensional(3D)α-MnCh/MWCNTs macroporous hybrid as the high-performance cathode of rechargeable Li-O2 batteries

Un doubtedly,there remai ns an urge nt prerequisite to achieve sign ifica nt adva nces in both the specific capacity and cyclability of Li-O2 batteries for their practical application.In this work,a series of unique three-dimensional(3D)α-MnO2/MWCNTs hybrids are successfully prepared using a facile lyophilization method and investigated as the cathode of Li-O2 batteries.Thereinto,cross-1 inkedα-MnO2/MWCNTs nano composites are first syn thesized via a modified chemical route.Results dem on strate that MnO2 nano rods in the nano composites have a length of 100-400 nm and a diameter ranging from 5 to 10 nm,and more attractively,the as-lyophilized 3D MnO2/MWCNTs hybrids is uniquely constructed with large amounts of interconnected macroporous channels.The U-O2 battery with the 3D macroporous hybrid cathode that has a mass percentage of 50%ofα-MnO2 delivers a high discharge specific capacity of 8,643 mAh·g^-1 at 100 mA·g^-1,and main tains over 90 cycles before the discharge voltage drops to 2.0 V un der a controlled specific capacity of 1,000 mAh·g^-1.It is observed that when being recharged,the product of toroidal Li2O2 particles disappears and electrode surfaces are well recovered,thus confirming a good reversibility.The excellent performanee of Li-O2 battery with the 3Dα-MnO2/MWCNTs macroporous hybrid cathode is ascribed to a syn ergistic com bination betwee n the unique macroporous architecture and highly efficient bi-fun ctionalα-MnO2/MWCNTs electrocatalyst.

Lithium-ion modified cellulose as a water-soluble binder for Li-O2 battery

An environment-friendly,water-soluble,and cellulose based binder(lithium carboxymethyl cellulose,CMC-Li)was successfully synthesized by using Li+to replace Na+in the commercial sodium carboxymethyl cellulose(CMC-Na).Li-O2 batteries based on the CMC-Li binder present enhanced discharge specific capacities(11151 mAh/g at 100 mA/g)and a superior cycling stability(100 cycles at 200 mA/g)compared with those based on the CMC-Na binder.The enhanced performance may originate from the electrochemical stability of the CMC-Li binder and the ion-conductive nature of CMC-Li,which promotes the diffusion of Li+in the cathode and consequently retards the increase of charge transfer resistance of the cathode during cycling.The results show that the water-soluble CMC-Li binder can be a green substitute for poly(vinylidene fluoride)(PVDF)binder based on organic solvent in the lithium oxygen batteries(LOBs).

A Generalization of Implicit Ore-condition for Hamiltonicity of k-connected Graphs

In 2005,Flandrin et al.proved that if G is a k-connected graph of order n and V(G)=X1∪X2∪···∪Xk such that d(x)+d(y)≥n for each pair of nonadjacent vertices x,y∈Xi and each i with i=1,2,···,k,then G is hamiltonian.In order to get more sufficient conditions for hamiltonicity of graphs,Zhu,Li and Deng proposed the definitions of two kinds of implicit degree of a vertex v,denoted by id1(v)and id2(v),respectively.In this paper,we are going to prove that if G is a k-connected graph of order n and V(G)=X1∪X2∪···∪Xk such that id2(x)+id2(y)≥n for each pair of nonadjacent vertices x,y∈Xi and each i with i=1,2,···,k,then G is hamiltonian.