Surface deterioration dependent on the crystal facets of spinel LiNi_(0.5)Mn_(1.5)O_(4) cathode active material

The spinel LiNi_(0.5)Mn_(1.5)O_(4)(LNMO)cathode active materials(CAMs)are considered a promising alternative to commercially available cathodes such as layered and polyanion oxide cathodes,primarily due to their notable safety and high energy density,particularly in their single-crystal type.Nevertheless,the industrial application of the LNMO CAMs is severely inhibited due to the interfacial deterioration and corrosion under proton-rich and high-voltage conditions.This study successfully designed and synthesized two typical types of crystal facets-exposed single-crystal LNMO CAMs.By tracking the electrochemical deterioration and chemical corrosion evolution,this study elucidates the surface degradation mechanisms and intrinsic instability of the LNMO,contingent upon their crystal facets.The(111)facet,due to its elevated surface energy,is found to be more susceptible to external attack compared to the(100)and(110)facets.Our study highlights the electrochemical corrosion stability of crystal plane engineering for spinel LNMO CAMs.

Re-delocalization of localized d-electrons in VO_(2)(R)-VS_(4)hetero-structure enables high performance of rechargeable Mg-ion batteries

Rechargeable Mg-ion batteries(MIBs)have attracted much more attentions by virtue of the high capacity from the two electrons chemistry.However,the reversible Mg^(2+)diffusion in cathode materials is restricted by the strong interactions between the high-polarized bivalent Mg^(2+)ions and anionic lattice.Herein,we design and propose a hetero-structural VO_(2)(R)-VS_(4)cathode,in which the re-delocalized d-electrons can effectively shield the polarity of Mg^(2+)ions.Theoretically,the electrons should spontaneously transfer from VS_(4)to VO_(2)(R)through the interfaces of hetero-structure due to the lower work function value of VS_(4).Furthermore,the internal electrons transfer lead to the electronic injection into VO_(2)(R)from VS_(4)and the partially broken V-V dimers,indicating the presence of lone pair electrons and charge re-delocalization.Benefiting from the shield effect of re-delocalized electrons,and the weakened attraction between cations and O/S anions enables more S^(2-)-S_(2)^(2-)redox groups to participate the electrochemical reactions and compensate the double charge of Mg^(2+)ions.Accordingly,VO_(2)(R)-VS_(4)hetero-structure exhibits a high specific capacity of 554 mA h g^(-1)at 50 mA g^(-1).It is believed that the charge re-delocalization of cathode extremely boost the Mg^(2+)ions migration for the high-capacity of MIBs.

Superior lithium storage performance in MoO_(3) by synergistic effects:Oxygen vacancies and nanostructures

Molybdenum trioxide(MoO_(3))has recently attracted wide attention as a typical conversion-type anode of Li-ion batteries(LIBs).Nevertheless,the inferior intrinsic conductivity and rapid capacity fading during charge/discharge process seriously limit large-scale commercial application of MoO_(3).Herein,the density function theory(DFT)calculations show that electron-proton co-doping preferentially bonds symmetric oxygen to form unstable HxMoO_(3).When the-OH-group in HxMoO_(3) is released into the solution in the form of H_(2)O,it is going to form MoO_(3-x)with lower binding energy.By the means of both electron-proton co-doping and high-energy nanosizing,oxygen vacancies and nanoflower structure are introduced into MoO_(3) to accelerate the ion and electronic diffusion/transport kinetics.Benefitting from the promotion of ion diffusion kinetics related to nanostructures,as well as both the augmentation of active sites and the improvement of electrical conductivity induced by oxygen vacancies,the MoO_(3-x)/nanoflower structures show excellent lithium-ion storage performance.The prepared specimen has a high lithium-ion storage capacity of 1261 mA h g^(-1)at 0.1 A g^(-1)and cyclic stability(450 cycle),remarkably higher than those of previously reported MoO_(3)-based anode materials.

Full-chain enhanced ion transport toward stable lithium metal anodes

The dendrite growth that results from the slow electrode process kinetics prevents the lithium(Li) metal anode from being used in practical applications. Here, full-chain enhanced ion transport for stabilizing Li metal anodes is proposed. Experimental and theoretical studies confirm that full-chain enhanced ion transport(electrocrystallization, mass transport in the electrolyte and diffusion in solid electrolyte interphase) under magnetoelectrochemistry contributes to a homogeneous, dense, and dendrite-free morphology. Specifically, the enhanced electrocrystallization behavior promotes the Li nucleation;the enhanced mass transport in the electrolyte alleviates the ion concentration gradient at the electrode surface, which helps to inhibit dendrite growth;and the enhanced diffusion in the solid electrolyte interphase further homogenizes the Li deposition behavior, obtaining regular and uniform Li particles.Consequently, the Li metal anode has exceptional cycling stability in both symmetric and full cells,and the pouch cell performs long cycles(170 cycles) in practice evaluation. This work advances fundamental knowledge of the magneto-dendrite effect and offers a new perspective on stabilizing metal anodes.

Accordion Frameworks Enable Free-Standing,High Si Content Anode for Li-ion Batteries

Implementing high-performance silicon(Si)anode in actual processing and application is highly desirable for next-generation,high-energy Li-ion batteries.However,high content of inactive matrix(including conductive agent and binder)is often indispensable in order to ensure local conductivity and suppress pulverization tendency of Si particles,which thus cause great capacity loss based on the mass of whole electrode.Here,we designed an accordion-structured,high-performance electrode with high Si content up to 95%.Si nanoparticles were well anchored into the interlayer spacings of accordion-like graphene arrays,and free-standing electrode was prepared via a simple filtration process without any binder.Conductive accordion framework ensures strong confinement effect of Si nanoparticles and also provides direct,non-tortuous channels for fast electrochemical reaction kinetics.As a consequence,the accordion Si electrodes exhibit ultrahigh,electrode-based capacities up to 3149 mAh g^(-1)(under Si content of 91%),as well as long-term stability.Also,the accordion electrode can bear extreme condition of over-lithiation and maintains stable in full-cell test.This design provides a significant stride in high Si content toward realistic,high-performance electrodes.

A self-healing liquid metal anode for lithium-ion batteries

The gallium-based liquid metal as one of the self-healing materials has gained wide attention, especially in the energy storage system. However, volume expansion with the ‘‘liquid-solid-liquid”transformation process still leads to un-controlled electrode failure, which stimulates the irreversibility of liquid metal and hinders their self-healing effect as the anode for lithium-ion batteries. Herein, the polypyrrole(PPy) with highly conductive and adhesive features is first introduced to fasten the liquid metal nanoparticles(gallium-tin alloy, EGaSn) in the integrated electrode and applied as the anode for lithium-ion batteries. A tightly PPy wrapped EGaSn nanoparticles structure is formed during the in-situ polymerization synthesis process, which effectively avoids the detachment of solid alloyed products. Based on the features of PPy, polyacrylic acid is added to facilitate strengthening the integrity of the electrode by constructing the hydrogen bond. The ‘‘dual-insurance” design endows the EGaSn to exhibit superior electrochemical kinetics and an astonishing self-healing effect. As a result, the customized anode displays superior cycling stability(499.8 mAh g^(-1) after 500 cycles at 1.0 A g^(-1))and rate capability(350 mAh g^(-1) at 2.0 A g^(-1)).This work enriches the electrode engineering technology of liquid metal nanoparticles and opens up a new way to customize the self-healing anode for lithium-ion batteries.

A multifunctional electrolyte with highly-coordinated solvation structure-in-nonsolvent for rechargeable lithium batteries

Rechargeable lithium-based battery is hailed as next-generation high-energy-density battery systems.However, growth of lithium dendrites, shuttle effect of lithium polysulfides intermediates and unstable interphase of high-voltage intercalation-type cathodes largely prevent their practical deployment.Herein, to fully conquer the three challenges via one strategy, a novel electrolyte with highlycoordinated solvation structure-in-nonsolvent is designed. On account of the particular electrolyte structure, the shuttle effect is completely suppressed by quasi-solid conversion of S species in Li-S batteries,with a stable cycle performance even at lean electrolyte(5μL mg^(-1)). Simultaneously, in-situ-formed highly-fluorinated interphases can not only lower Li+diffusion barrier to ensure uniform nucleation of Li but also improve stability of NCM cathodes, which enable excellent capacity retention of Lik LiNi(0.5)Co(0.2)Mn(0.3)O2 batteries under conditions toward practical applications(high loading of 2.7 m Ah cm^(-2) and lean electrolyte of 5 m L Ah^(-1)). Besides, the electrolyte is also nonflammable. This electrolyte structure offers useful guidelines for the design of novel organic electrolytes for practical lithium-based batteries.

Regulating electrodeposition behavior through enhanced mass transfer for stable lithium metal anodes

Electrode process kinetics is a key part that determines the morphology of metal electrodeposition.However,the liquid-phase mass transfer process and its effect on lithium(Li)metal electrodeposition are still poorly understood.Herein,the effect of mass transfer on the electrodeposition behavior of Li metal is explored.Experiments and COMSOL Multiphysics simulations reveal that the enhanced mass transfer,which is induced by ultrasonic wave,can homogenize the ion flow on the surface of electrode to obtain uniform Li nucleation.Meanwhile,the rapid mass transfer of Li^(+)provides sufficient cations around the germinated Li to avoid preferential growth of Li in a specific direction.Based on the simultaneous regulation of nucleation and growth behavior,a smooth and compact Li deposits can be achieved,which exhibit a small polarization voltage during repeated Li plating/striping and a considerably enhanced cyclability.This work enriches the fundamental understanding of Li electrodeposition without dendrite structure and affords fresh guidance to develop dendrite-free metal anodes for metal-based batteries.

Understanding the Coffee ring Effect on Self-discharge Behavior of Printed micro-Supercapacitors

Printed micro-supercapacitor exhibits its flexibility in geometry design and integration,showing unprecedented potential in powering the internet of things and portable devices.However,the printing process brings undesired processing defects(e.g.,coffee ring effect),resulting in severe self-discharge of the printed micro-supercapacitors.The impact of such problems on device performance is poorly understood,limiting further development of microsupercapacitors.Herein,by analyzing the self-discharge behavior of fully printed micro-supercapacitors,the severe self-discharge problem is accelerated by the ohmic leakage caused by the coffee ring effect on an ultrathin polymer electrolyte.Based on this understanding,the coffee ring effect was successfully eradicated by introducing graphene oxide in the polymer electrolyte,achieving a decline of 99%in the self-discharge rate.Moreover,the micro-supercapacitors with uniformly printed polymer electrolyte present 7.64 F cm^(-3)volumetric capacitance(14.37 mF cm^(-2)areal capacitance),exhibiting about 50%increase compared to the one without graphene oxide addition.This work provides a new insight to understand the relationship between processing defects and device performance,which will help improve the performance and promote the application of printed micro-supercapacitors.

Growing curly graphene layer boosts hard carbon with superior sodium-ion storage

Benefiting from the distinctive ordering degree and local microstructure characteristics,hard carbon(HC)is considered as the most promising anode for sodium-ion batteries(SIBs).Unfortunately,the low initial Coulombic efficiency(ICE)and limited reversible capacity severely impede its extensive application.Here,a homogeneous curly graphene(CG)layer with a micropore structure on HC is designed and executed by a simple chemical vapor deposition method(without catalysts).CG not only improves the electronic/ionic conductivity of the hard carbon but also effectively shields its surface defects,enhancing its ICE.In particular,due to the spontaneous curling structural characteristics of CG sheets(CGs),the micropores(≤2 nm)formed provide additional active sites,increasing its capacity.When used as a sodium-ion battery anode,the HC-CG composite anode displayed an outstanding reversible capacity of 358 mAh·g^(-1),superior ICE of 88.6%,remarkable rate performance of 145.8 mAh·g^(-1)at 5 A·g^(-1),and long cycling life after 1000 cycles with 88.6%at 1 A·g^(-1).This work provides a simple defect/microstructure turning strategy for hard carbon anodes and deepens the understanding of Na+storage behavior in the plateau region,especially on the pore-filling mechanism by forming quasi-metallic clusters.

Understanding and quantifying capacity loss in storage aging of Ah-level Li metal pouch cells

Promoting industry applications of high-energy Li metal batteries(LMBs)is of vital importance for accelerating the electrification and decarbonization of our society.Unfortunately,the time-dependent storage aging of Ah-level Li metal pouch cells,a ubiquitous but crucial practical indicator,has not yet been revealed.Herein,we first report the storage behaviors and multilateral synergistic aging mechanism of Ah-level NCM811jjLi pouch cells during the 120-day long-term storage under various conditions.Contrary to the conventional belief of Li-ion batteries with graphite intercalation anodes,the significant available capacity loss of 32.8%on average originates from the major electrolyte-sensitive anode corrosion and partial superimposed cathode degradation,and the irreversible capacity loss of 13.3%is essentially attributed to the unrecoverable interface/structure deterioration of NCM with further hindrance of the aged Li.Moreover,principles of alleviating aging have been proposed.This work bridges academia and industry and enriches the fundamental epistemology of storage aging of LMBs,shedding light on realistic applications of high-energy batteries.

Radiation effects on lithium metal batteries

The radiation tolerance of energy storage batteries is a crucial index for universe exploration or nuclear rescue work,but there is no thorough investigation of Li metal batteries.Here,we systematically explore the energy storage behavior of Li metal batteries under gamma rays.Degradation of the performance of Li metal batteries under gamma radiation is linked to the active materials of the cathode,electrolyte,binder,and electrode interface.Specifically,gamma radiation triggers cation mixing in the cathode active material,which results in poor polarization and capacity.

Chemically stable polypyrrole-modified liquid metal nanoparticles with the promising photothermal conversion capability

The gallium-based eutectic alloy has gained particular attention in various fields due to its natural features of metallic fluids at room temperature.However,these alloy nanoparticles are extremely susceptible to be oxidized accompanied by de-alloying during the preparation,storage,and application.Here,with the assistance of the macromolecular stabilizer and dopant,sodium dodecylbenzene sulfonate(SDBS),we demonstrate a stable polypyrrole(PPy)layer acts as a protected“armor”on the surface of liquid metal(i.e.,gallium-tin,EGaSn).SDBS enables the EGa Sn to keep well dispersion and protects dispersed EGaSn from being durative oxidized before PPy coating.Furthermore,PPy greatly inhibits the oxidation of EGaSn owing to the strong interface interaction between the lone pair electrons around the N atoms of Py rings and the Ga3+orbit of EGaSn.Consequently,the fabricated EGaSn nanoparticles possess the features of smaller particle size,superior uniform distribution,and stronger antioxidant capacity.The prepared EGaSn@PPy composite exhibits superior stability even after storing in an aqueous solution for up to 100 days.As a proof-of-concept application,the EGaSn@PPy composite displays remarkable photothermal performance with an enhanced photothermal conversion efficiency.This work provides a novel surface engineering strategy to ameliorate liquid metal for photothermal therapy applications.

Fast decomposition of Li_(2)CO_(3)/C actuated by singleatom catalysts for Li-CO_(2) batteries

Lithium carbon dioxide(Li-CO_(2))batteries deliver a theoretical energy density of 1876 W h kg^(-1) in terms of effective utilization of greenhouse gases.This battery system is considered to be an encouraging electrochemical energy storage device and a promising alternative to Li-ion batteries.However,the main drawback of Li-CO_(2) batteries is their accumulative discharge product of Li_(2)CO_(3)/C,which leads to large overpotential and poor cycling performance.Thus,specific and efficient catalysts must be explored to enhance the decomposition of Li_(2)CO_(3)/C.Single-atom catalysts(SACs)are regarded as promising heterogeneous catalysts owing to their maximized utilization of metal atoms and strong interfacial electronic interactions.Herein,single-metal atoms of Fe,Co,and Ni uniformly anchored on N-doped reduced graphene oxide(rGO),designated as Fe_(1)/N-rGO,Co1/N-rGO,and Ni_(1)/N-r GO,respectively,are designed and fabricated to investigate their catalytic activity toward the decomposition of Li_(2)CO_(3)/C.Among them,Fe_(1)/N-rGO delivers a high discharge capacity of 16,835 mA h g^(-1) at 100 mA g^(-1) and maintains stability for more than 170 cycles with a discharge voltage of 2.30 V at 400 mA g^(-1).Therefore,this catalysts are overwhelmingly superior to other types.This work reveals the advances of SACs in Li-CO_(2) batteries and offers an effective method for realizing high-performance Li-CO_(2) batteries.

Uniform-dispersed ZnS quantum dots loading on graphene as a promising anode for potassium-ion batteries

The potassium-ion batteries(PIBs)have become the promising energy storage devices due to their relatively moderate cost and plenteous potassium resources.Whereas,the main drawback of PIBs is unsatisfacto ry electrochemical perfo rmance induced by the larger ionic radius of potassium ion.Herein,we report a well-designed,uniform-dispersed,and morphology-controllable zinc sulfide(ZnS)quantum dots loading on graphene as an anode in the PIBs.The directed uniform dispersion of the in-situ growing ZnS quantum dots(~2.8 nm in size)on graphene can mitigate the volume effect during the insertionextraction process and shorten the migration path of potassium ions.As a result,the battery exhibits superior cycling stability(350.4 mAh/g over 200 cycles at 0.1 A/g)and rate performance(98.8 mAh/g at2.0 A/g).We believe the design of active material with quantum dot-minimized size provides a novel route into PIBs and contributes to eliminating the major electrode failure issues of the system.

Self-ball milling strategy to construct high-entropy oxide coated LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2) with enhanced electrochemical performance

High-entropy oxides(HEOs)are a new class of emerging materials with fascinating properties(such as structural stability,tensile strength,and corrosion resistance).High-entropy oxide coated Ni-rich cathode materials have great potential to improve the electrochemical performance.Here,we present a facile self-ball milling method to obtain(La_(0.2)Nd_(0.2)Sm_(0.2)Eu_(0.2)Gd_(0.2))_(2)Zr_(2)O_(7)(HEO)coated LiNi_(0.8)Co_(_(0.1))Mn_(_(0.1))O_(2)(NCM811).The HEO coating endows NCM811 with a stable surface,reduces the contact with the external environment(air and electrolyte),and inhibits side reactions between cathode and electrolyte.These favorable effects,especially when the coating amount is 5 wt%,result in a significant reduction of the battery polarization and an increase in the capacity retention from 57.3%(NCM811)to 74.2%(5HEO-NCM811)after 300 cycles at 1 C(1 C=200 mA·h·g^(−1)).Moreover,the morphology and spectroscopy analysis after the cycles confirmed the inhibitory effect of the HEO coating on electrolyte decomposition,which is important for the cycle life.Surprisingly,HEO coating reduces the viscosity of slurry by 37%–38%and significantly improves the flowability of the slurry with high solid content.This strategy confirms the feasibility of HEO-modified Ni-rich cathode materials and provides a new idea for the design of high-performance cathode materials for Li-ion batteries.

A multiphase sodium vanadium phosphate cathode material for high-rate sodium-ion batteries

The unsatisfactory rate capability and poor cycling stability at high rate of sodium-ion batteries(SIBs) have impeded their practical applications. Herein, a Na_(3)V_(2)(PO_(4))_(3)/Na_(3)V_(3)(PO_(4))_(4) multiphase cathode materials for high-rate and long cycling SIBs was successfully synthesized by regulation the stoichiometric ratio of raw materials. The combined experiment and simulation results show that the multiphase materials consisted of NASICON structural phase Na3V2(PO4)3 and layered structure phase Na_(3)V_(3)(PO_(4))_(4), possess abundant phase boundaries. Electrochemical experiments demonstrate that the multiphase materials maintain a remarkable reversible capacity of 69.0 mA h g^(-1) even at an ultrahigh current density of 100 C with a high capacity retention of 81.25 % even after 10,000 cycles. Na_(3)V_(2)(PO_(4))_(3)/Na_(3)V_(3)(PO_(4))_(4) electrode exhibits a higher working voltage, superior rate capability and better cycling stability than Na_(3)V_(2)(PO_(4))_(3) electrode, which indicates that the introduction of second phase can be an effective strategy for the development of novel cathode materials for SIBs.