Enhancing Li-S battery performance via functional polymer binders for polysulfide inhibition

The commercialization of lithium-sulfur(Li-S)batteries faces several challenges,including poor conductivity,unexpected volume expansion,and continuous sulfur loss from the cathode due to redox shuttling.In this study,we introduce a novel polymer via a simple cross-linking between poly(ether-thioureas)(PETU)and poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate)(PEDOT:PSS)as a bifunctio nal binder for Li-S batteries(devotes as"PPTU").Compared to polyvinylidene fluoride(PVDF),as-prepared PPTU exhibits significantly higher electrical conductivity,facilitating electrochemical reactions.Additionally,PPTU demonstrates effective adsorption of lithium polysulfides,leading to improved cycling stability by suppressing the shuttling effect.We investigate this behavior by monitoring morphological changes at the cell interface using synchrotron X-ray tomography.Cells with PPTU binders exhibit remarkable rate performance,desired reversibility,and excellent cycling stability even under stringent bending and twisting conditions.Our work represents promising progress in functional polymer binder development for Li-S batteries.

Synergetic Control of Li^(+)Transport Ability and Solid Electrolyte Interphase by Boron-Rich Hexagonal Skeleton Structured All-Solid-State Polymer Electrolyte

High Li^(+)transference number electrolytes have long been understood to provide attractive candidates for realizing uniform deposition of Li^(+).However,such electrolytes with immobilized anions would result in incomplete solid electrolyte interphase(SEI)formation on the Li anode because it suffers from the absence of appropriate inorganic components entirely derived from anions decomposition.Herein,a boron-rich hexagonal polymer structured all-solid-state polymer electrolyte(BSPE+10%LiBOB)with regulated intermolecular interaction is proposed to trade off a high Li^(+)transference number against stable SEI properties.The Li^(+)transference number of the as-prepared electrolyte is increased from 0.23 to 0.83 owing to the boron-rich cross-linker(BC)addition.More intriguingly,for the first time,the experiments combined with theoretical calculation results reveal that BOB^(-)anions have stronger interaction with B atoms in polymer chain than TFSI^(-),which significantly induce the TFSI^(-)decomposition and consequently increase the amount of LiF and Li3N in the SEI layer.Eventually,a LiFePO_(4)|BSPE+10%LiBOBlLi cell retains 96.7%after 400 cycles while the cell without BC-resisted electrolyte only retains 40.8%.BSPE+10%LiBOB also facilitates stable electrochemical cycling of solid-state Li-S cells.This study blazes a new trail in controlling the Li^(+)transport ability and SEI properties,synergistically.

Unveiling and Alleviating Chemical“Crosstalk”of Succinonitrile Molecules in Hierarchical Electrolyte for High-Voltage Solid-State Lithium Metal Batteries

Succinonitrile-based plastic crystal electrolytes have emerged for high-energy-density Li metal batteries in terms of their superior ambient ionic conductivity,low flammability,and benign compatibility with high voltage cathode,but are hampered by inherent instabilities toward Li anodes.Constructing hierarchical solid electrolytes structure is a fundamental approach to protect Li anode from succinonitrile attacks,with succinonitrile-based oxidation-resistance layer facing high voltage cathode and reduction-tolerant layer contacting Li anode.However,free succinonitrile molecules in succinonitrile-based electrolyte layer can diffuse across the electrolyte/electrolyte interface and further reach Li anode surface during the battery cycle.This chemical“crosstalk”cause reduction-tolerant electrolyte layer to fail to protect the Li anode from the attacks of free succinonitrile molecules.Nano Li_(6.4)La_(3)Zr_(1.4)Ta_(0.6)O_(12)is introduced creatively into succinonitrile-based electrolyte layer.By taking advantage of the complexation between La atoms in Li_(6.4)La_(3)Zr_(1.4)Ta_(0.6)O_(12)and N atoms in succinonitrile,the free succinonitrile molecules are successfully immobilized in succinonitrile-based electrolyte layer.The resulting low resistance and highly durable solid electrolyte interphase and cathode electrolyte interphase endow NCM622||Li batteries with remarkable cycle stability.Our research provides a new idea for the real application of plastic crystal electrolytes in high voltage solid-state lithium metal batteries.

Anchoring polysulfide with artificial solid electrolyte interphase for dendrite-free and low N/P ratio Li-S batteries

Lithium sulfur batteries are regarded as a promising candidate for high-energy-density energy storage devices.However,the lithium metal anode in lithium-sulfur batteries encounters the problem of lithium dendrites and lithium metal consumption caused by polysulfide corrosion.Herein we design a dualfunction PMMA/PPC/LiNO3composite as an artificial solid electrolyte interphase(PMCN-SEI)to protect Li metal anode.This SEI offers multiple sites of C=O for polysulfide anchoring to constrain corrosion of Li metal anode.The lithiated polymer group and Li3N in PMCN-SEI can homogenize lithium-ion deposition behavior to achieve a dendrite-free anode.As a result,the PMCN-SEI protected Li metal anode enables the Li||Li symmetric batteries to maintain over 300 cycles(1300 h)at a capacity of 5 m Ah cm^(-2),corresponding to a cumulative capacity of 3.25 Ah cm^(-2).Moreover,Li-S batteries assembled with 20μm of Li metal anode(N/P=1.67)still deliver an initial capacity of 1166 m A h g-1at 0.5C.Hence,introducing polycarbonate polymer/inorganic composite SEI on Li provides a new solution for achieving the high energy density of Li-S batteries.

20μm Li metal modified with phosphate rich polymer-inorganic interphase applied in commercial carbonate electrolyte

Li metal batteries are supposed to reach real application in order to fulfill the high-energy density requirement of energy storage system.Unfortunately,the commonly used carbonate electrolyte react with pristine Li,which result in short lifetime of lithium metal battery.To alleviate the side reactions of Li metal with liquid electrolyte,here we propose a phosphate rich polymer-inorganic layer as an interphase.Due to the inert properties of lithium phosphate derived from LiPO_(2)F_(2)and poly-ether,the side-reaction of carbonate solvent are prevented.As a result,lithium metal anode sustains for 800 cycles in symmetrical cell test under 1 m A cm^(-2).Even under strict condition(20μm Li,capacity ratio N/P=2.3,electrolyte/active material=3μL mg^(-1)),coin cell test still runs stable for 150 cycles with high Coulombic efficiency.Furthermore,both LiFePO_(4)and LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2)pouch cell under 5μL m A^(-1)h^(-1)condition also exhibit good stability at 0.5 C and 2 C rate.With this approach,high-energy and high-power Li metal batteries are approaching to real application in the near future.

A Self-Healing and Nonflammable Cross-Linked Network Polymer Electrolyte with the Combination of Hydrogen Bonds and Dynamic Disulfide Bonds for Lithium Metal Batteries

The self-healing solid polymer electrolytes(SHSPEs)can spontaneously eliminate mechanical damages or micro-cracks generated during the assembly or operation of lithium-ion batteries(LIBs),significantly improving cycling performance and extending service life of LIBs.Here,we report a novel cross-linked network SHSPE(PDDP)containing hydrogen bonds and dynamic disulfide bonds with excellent self-healing properties and nonflammability.The combination of hydrogen bonding between urea groups and the metathesis reaction of dynamic disulfide bonds endows PDDP with rapid self-healing capacity at 28°C without external stimulation.Furthermore,the addition of 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide(EMIMTFSI)improves the ionic conductivity(1.13×10^(−4)S cm^(−1)at 28°C)and non-flammability of PDDP.The assembled Li/PDDP/LiFePO_(4)cell exhibits excellent cycling performance with a discharge capacity of 137 mA h g^(−1)after 300 cycles at 0.2 C.More importantly,the self-healed PDDP can recover almost the same ionic conductivity and cycling performance as the original PDDP.

High-performance PVDF-HFP based gel polymer electrolyte with a safe solvent in Li metal polymer battery

Poly(vinylidenefluoride-co-hexafluoropropylene)(PVDF-HFP)based gel polymer electrolytes are widely studied owing to their electrochemical stability and high dielectric constant.However,most gel polymer electrolytes show unsatisfied safety and interface compatibility due to excessive absorption of volatile and flammable liquid solvents.Herein,by using a safe solvent(N-methyl-2-pyrrolidone)with higher boiling(203℃)and flash points(95℃),we initiatively fabricate a flexible PVDF-HFP based gel polymer electrolyte.The obtained gel polymer electrolyte demonstrates a high ionic conductivity of 7.24×10^−4 S cm−1,an electrochemical window of 5.2 V,and a high lithium transference number of 0.57.As a result,the synthesized polymer electrolyte exhibits a capacity retention of 70%after 500 cycles at 0.5 C,and a discharge capacity of 86 mAh g−1 even at a high current rate of 10 C for LiFePO4 based Li metal batteries.Moreover,a stable Li plating/stripping for more than 500 h is achieved under 0.1 mAh at both room temperature and 70℃.Our results indicate that the PVDF-HFP polymer electrolyte is promising for manufacturing safe and high-performance Li metal polymer batteries.

“Polymer-in-ceramic” based poly(ε-caprolactone)/ceramic composite electrolyte for all-solid-state batteries

Inspired by the concept of "polymer-in-ceramic",a composite poly(ε-caprolactone)(PCL)/ceramic containing LiTFSI is prepared and investigated as a solid electrolyte for all-solid-state batteries.The composite with the optimum concentration of 45 wt% LiTFSI and 75 wt% Li1.5Al0.5Ge1.5(PO4)3(LAGP,NASICON-type structure) exhibits a high ionic conductivity(σi=0.17 mS cm-1) at 30℃,a transference number of 0.30,and is stable up to 5.0 V.The composite electrolyte is a flexible and self-standing membrane.Solid-state LiFePO4//Li batteries with this composite electrolyte demonstrate excellent cycling stability with high discharge capacity of 157 mA h g-1,high capacity retention of 96% and coulombic efficiency of 98.5% after 130 cycles at 30℃ and 0.1 C rate.These electrochemical properties are better than other PCL-based allsolid-lithium batteries,and validate the concept of "polymer-in-ceramic" by avoiding the drawback of lower conductivity in prior "polymer-in-ceramic" electrolyte at high concentration of the ceramic.

MoO2 nanoparticles/carbon textiles cathode for high performance flexible Li-O2 battery

Conventional Li-O2 battery is hardly considered as a next-generation flexible electronics thus far,since it is inflexible,bulk,and limited by the absence of the adjustable cell configuration.Here,we report a binder-free and flexible electrode of x wt%MoO2 NPs/CTs(x=6,16,and 28).A cell with 16 wt% MoO2 NPs/CTs displays a good cyclability over 240 cycles with a low overpotential of 0.33 V on the 1st cycle at a constant current density of 0.2 mA cm-2,a considerable rate performance,a superior reversibility associated with the desired formation and degradation of Li2O2,and a high electrochemical stability even under stringent bending and twisting conditions.Our work represents a promising progress in the material development and architecture design of O2 electrode for flexible Li-O2 batteries.

Hierarchical N-doped carbon nanocages/carbon textiles as a flexible O2 electrode for Li–O2 batteries

The conventional Li–O2 battery(LOB)has hardly been considered as a next-generation flexible electronics thus far,since it is bulk,inflexible and limited by the absence of an adjustable cell configuration.Here,we present a flexible Li–O2 cell using N-doped carbon nanocages grown onto the carbon textiles(NCNs/CTs)as a self-standing and binder-free O2 electrode.The highly flexible NCNs/CTs exhibits an excellent mechanic durability,a promising catalytic activity towards the ORR and OER,a considerable cyclability of more than 70 cycles with an overpotential of 0.36 V on the 1 stcycle at a constant current density of 0.2 m A/cm2,a good rate capability,a superior reversibility with formation and decomposition of desired Li2 O2,and a highly electrochemical stability even under stringent bending and twisting conditions.Our work represents a promising progress in the material development and architecture design of O2 electrode for flexible LOBs.

The structural, electronic, and optical properties of organic–inorganic mixed halide perovskites CH_3NH_3Pb(I_(1-y)X_y)_3(X = Cl, Br)

Methylammmonium lead iodide perovskites（CH3NH3PbI3） have received wide attention due to their superior optoelectronic properties. We performed first-principles calculations to investigate the structural, electronic, and optical properties of mixed halide perovskites CH3NH3Pb（I（1-y）Xy）3（X = Cl, Br; y = 0, 0.33, 0.67）. Our results reveal the reduction of the lattice constants and dielectric constants and enhancement of band gaps with increasing doping concentration of Cl-/Br-at I-. Electronic structure calculations indicate that the valance band maximum（VBM） is mainly governed by the halide p orbitals and Pb 6 s orbitals, Pb 6 p orbitals contribute the conduction band minimum（CBM） and doping does not change the direct semiconductor material. The organic cation [CH3NH3]~＋does not take part in the formation of the band and only one electron donates to the considered materials. The increasing trends of the band gap with Cl content from y = 0（0.793 eV） to y = 0.33（0.953 eV） then to y = 0.67（1.126 eV）. The optical absorption of the considered structures in the visible spectrum range is decreased but after doping the stability of the material is improving.

PRS:Predication-Based Replica Selection Algorithm for Key-Value Stores

The tail latency of end-user requests,which directly impacts the user experience and the revenue,is highly related to its corresponding numerous accesses in key-value stores.The replica selection algorithm is crucial to cut the tail latency of these key-value accesses.Recently,the C3 algorithm,which creatively piggybacks the queue-size of waiting keys from replica servers for the replica selection at clients,is proposed in NSDI 2015.Although C3 improves the tail latency a lot,it suffers from the timeliness issue on the feedback information,which directly influences the replica selection.In this paper,we analysis the evaluation of queuesize of waiting keys of C3,and some findings of queue-size variation were made.It motivate us to propose the Prediction-Based Replica Selection(PRS)algorithm,which predicts the queue-size at replica servers under the poor timeliness condition,instead of utilizing the exponentially weighted moving average of the state piggybacked queue-size as in C3.Consequently,PRS can obtain more accurate queue-size at clients than C3,and thus outperforms C3 in terms of cutting the tail latency.Simulation results confirm the advantage of PRS over C3.

Multilayer polyethylene separator with enhanced thermal properties for safe lithium-ion batteries Author links open overlay panel

The separator plays an important part in battery safety and performance.Polyolefin separators are widely used in commercial Lithium-ion batteries(LIBs),owing to their excellent properties,but they suffer from serious thermal shrinkage and poor electrolyte wettability.Thus,a multilayer separator(ASPESA)is developed by coating two thin layers of low-density polyethylene(LDPE)and Al_(2)O_(3)on both sides of a polyethylene membrane using a facile and environmentally friendly casting technique.The ASPESA separator demonstrates a shutdown function at 120℃and shows enhanced thermal stability under 185℃,with a small thermal shrinkage of 1%.Meanwhile,the LDPE and Al_(2)O_(3)layers can improve the electrolyte wettability and electrolyte uptake(407.23%).The multilayer ASPESA separator delivers an excellent cycle performance in LiFePO_(4)||Li cells with a discharge capacity of 144.5 mAh g^(-1)after 900 cycles,with a high-capacity retention of 98.9%(compared to the 5th cycle).Therefore,the multilayer ASPESA separator has great utilization potential as a high-safety separator in LIBs.

Cointercalation-Free Ether-Based Deep Eutectic Electrolyte for All-Climate Battery

Lithium-ion batteries(LIBs)with ether-based electrolytes usually provide low cell performance when matched with the graphite(Gr)anodes due to cointercalation of Li+-solvent.Herein,a novel deep eutectic ether electrolyte with polyethylene glycol dimethyl ether(PEGDME)featuring low flammability and high safety is developed,and fluoroethylene carbonate(FEC)is adopted to mitigate the cointercalation phenomenon.Unlike the common effect of FEC’s role in the first solvation shell,our results reveal that FEC molecules affect the Li+-PEGDME insertion behavior through FECPEGDME intramolecular interaction.As a result,a high discharge capacity of 450 mA h g^(−1)is achieved in Li||Gr/SiO_(x)cells at 50℃,and 370 mA h g^(−1)can be realized,even at−20℃(three times higher than commercial carbonate electrolyte).Moreover,Gr/SiO_(x)||LiNi_(0.6)Co_(0.2)Mn_(0.2O2)full cells maintain good capacity retention in both coin cell and pouch cell configurations over a wide temperature range.Our work deciphers the role of FEC as an additive and proposes new electrolyte optimization strategies to achieve high-performance all-climate LIBs.

In-situ polymerized carbonate induced by Li-Ga alloy as novel artificial interphase on Li metal anode

Li metal is considered an ideal anode material because of its high theoretical capacity and low electrode potential.However,the practical usage of Li metal as an anode is severely limited because of inevitable parasitic side reactions with electrolyte and dendrites formation.At present,single-component artificial solid electrolyte interphase cannot simultaneously meet the multiple functions of promoting ion conduction,guiding lithium ion deposition,inhibiting dendrite growth,and reducing interface side reactions.Therefore,multi-component design on Li metal surface is widely investigated to achieve long-term cycling.Herein,we report a Li_(2)Ga-carbonate polymer interphase layer to solve volume changes,Li dendrites formation and side-reactions.As a result,the Li symmetric cell can be stabilized at 3.0 m A/cm^(2)in carbonate electrolyte with limited volume of 20μL.Coupled with 13.6 mg/cm^(2)(loading of 2 mAh/cm^(2))LiFePO_(4)cathode,discharge capacity retains at 90%for over 150 cycles under limited electrolyte conditions.With such an alloy-polymer interphase layer,higher energy density Li metal batteries become prominent in the near future.

AgTFSI Pretreated Li Anode in LiI-Mediated Li-O_(2)Battery:Enabling Lithiophilic Solid Electrolyte Interphase Generation to Suppress the Redox Shuttling

Although lithium iodide(LiI)as a redox mediator(RM)can decrease the overpotential in Li-O_(2)batteries,the stability of the Li anode is still one critical issue due to the redox shuttling.Here,we firstly present a novel approach for generating Ag and LiTFSI enriched Li anode(designated as ALE@Li anode)via a spontaneous substitution between pure Li and bis(trifluoromethanesulfonyl)imide silver,in a LiI-participated Li-O_(2)cell.It can induce the generation of a lithiophilic solid electrolyte interphase(SEI)enriched with Ag,F,and N species(e.g.,Ag_(2)O,Li-Ag alloy,LiF,and Li_(3)N)during cell operation,which contributes to promoting the electrochemical performance through the shuttling inhibition.Compared to a cell with a bare Li anode,the one with as-prepared ALE@Li anode shows an enhanced cyclability,a considerable rate capability,and a good reversibility.In addition,a synchrotron X-ray computed tomography technique is employed to investigate the inhibition mechanism for shuttling effect by monitoring the morphological evolution on the cell interfaces.Therefore,this work highlights the deliberate design in the modified Li anode in an easy-to-operate and cost-effective way as well as providing guidance for the construction of artificial SEI layers to suppress the redox shuttling of RMs in Li-O_(2)batteries.