Lithium-Ion Charged Polymer Channels Flattening Lithium Metal Anode

The concentration difference in the near-surface region of lithium metal is the main cause of lithium dendrite growth.Resolving this issue will be key to achieving high-performance lithium metal batteries(LMBs).Herein,we construct a lithium nitrate(LiNO_(3))-implanted electroactiveβphase polyvinylidene fluoride-co-hexafluoropropylene(PVDF-HFP)crystalline polymorph layer(PHL).The electronegatively charged polymer chains attain lithium ions on the surface to form lithium-ion charged channels.These channels act as reservoirs to sustainably release Li ions to recompense the ionic flux of electrolytes,decreasing the growth of lithium dendrites.The stretched molecular channels can also accelerate the transport of Li ions.The combined effects enable a high Coulombic efficiency of 97.0%for 250 cycles in lithium(Li)||copper(Cu)cell and a stable symmetric plating/stripping behavior over 2000 h at 3 mA cm^(-2)with ultrahigh Li utilization of 50%.Furthermore,the full cell coupled with PHL-Cu@Li anode and Li Fe PO_(4) cathode exhibits long-term cycle stability with high-capacity retention of 95.9%after 900 cycles.Impressively,the full cell paired with LiNi_(0.87)Co_(0.1)Mn_(0.03)O_(2)maintains a discharge capacity of 170.0 mAh g^(-1)with a capacity retention of 84.3%after 100 cycles even under harsh condition of ultralow N/P ratio of 0.83.This facile strategy will widen the potential application of LiNO_(3)in ester-based electrolyte for practical high-voltage LMBs.

Seismic monitoring of sub-seafloor fluid processes in the Haima cold seep area using an Ocean Bottom Seismometer (OBS)

The use of ocean bottom seismometers provides an effective means of studying the process and the dynamic of cold seeps by continuously recording micro-events produced by sub-seafloor fluid migration.We deployed a four-component Ocean Bottom Seismometer(OBS)at an active site of the Haima cold seep from 6 November to 19 November in 2021.Here,we present the results of this short-term OBS monitoring.We first examine the OBS record manually to distinguish(by their distinctive seismographic signatures)four types of events:shipping noises,vibrations from our remotely operated vehicle(ROV)operations,local earthquakes,and short duration events(SDEs).Only the SDEs are further discussed in this work.Such SDEs are similar to those observed in other sea areas and are interpreted to be correlated with sub-seafloor fluid migration.In the OBS data collected during the 14-day monitoring period.We identify five SDEs.Compared to the SDE occurrence rate observed in other cold seep regions,five events is rather low,from which it could be inferred that fluid migration,and subsequent gas seepage,is not very active at the Haima site.This conclusion agrees with multi-beam and chemical observations at that site.Our observations thus provide further constraint on the seepage activity in this location.This is the first time that cold seep-related SDEs have been identified in the South China Sea,expanding the list of sea areas where SDEs are now linked to cold seep fluid migration.

Revealing alkali metal ions transport mechanism in the atomic channels of Au@a-MnO_(2)

Understanding alkali metal ions’(e.g.,Li^(+)/Na^(+)/K^(+))transport mechanism is challenging but critical to improving the performance of alkali metal batteries.Herein using a-MnO_(2)nanowires as cathodes,the transport kinetics of Li^(+)/Na^(+)/K^(+)in the 2×2 channels of a-MnO_(2)with a growth direction of[001]is revealed.We show that ion radius plays a decisive role in determining the ion transport and electrochemistry.Regardless of the ion radii,Li^(+)/Na^(+)/K^(+)can all go through the 2×2 channels of a-MnO_(2),generating large stress and causing channel merging or opening.However,smaller ions such as Li^(+)and Na^(+)cannot only transport along the[001]direction but also migrate along the<110>direction to the nanowire surface;for large ion such as K^(+),diffusion along the<110>direction is prohibited.The different ion transport behavior has grand consequences in the electrochemistry of metal oxygen batteries(MOBs).For Li-O_(2)battery,Li^(+)transports uniformly to the nanowire surface,forming a uniform layer of oxide;Na^(+)also transports to the nanowire surface but may be clogged locally due to its larger radius,therefore sporadic pearl-like oxides form on the nanowire surface;K^(+)cannot transport to the nanowire surface due to its large radius,instead,it breaks the nanowire locally,causing local deposition of potassium oxides.The study provides atomic scale understanding of the alkali metal ion transport mechanism which may be harnessed to improve the performance of MOBs.

Multiscale strain alleviation of Ni-rich cathode guided by in situ environmental transmission electron microscopy during the solid-state synthesis

Ni-rich layered oxides are one of the most promising cathode materials for Li-ion batteries due to their high energy density.However,the chemomechanical breakdown and capacity degradation associated with the anisotropic lattice evolution during lithiation/delithiation hinders its practical application.Herein,by utilizing the in situ environmental transmission electron microscopy(ETEM),we provide a real time nanoscale characterization of high temperature solid-state synthesis of LiNi_(0.8)CO_(0.1)Mn_(0.1)O_(2)(NCM811) cathode,and unprecedentedly reveal the strain/stress formation and morphological evolution mechanism of primary/second ary particles,as well as their influence on electrochemical performance.We show that stress inhomogeneity during solid-state synthesis will lead to both primary/secondary particle pulverization and new grain boundary initiation,which are detrimental to cathode cycling stability and rate performance.Aiming to alleviate this multiscale strain during solid-state synthesis,we introduced a calcination scheme that effectively relieves the stress during the synthesis,thus mitigating the primary/secondary particle crack and the detrimental grain boundaries formation,which in turn improves the cathode structural integrity and Li-ion transport kinetics for long-life and high-rate electrochemical performance.This work remarkably advances the fundamental understanding on mechanochemical properties of transition metal oxide cathode with solid-state synthesis and provides a unified guide for optimization the Ni-rich oxide cathode.

In situ Observation of Li Deposition-Induced Cracking in Garnet Solid Electrolytes

Lithium(Li)penetration through solid electrolytes(SEs)induces short circuits in Li solid-state batteries(SSBs),which is a critical issue that hinders the development of high energy density SSBs.While cracking in ceramic SEs has been often shown to accompany Li penetration,the interplay between Li deposition and cracking remains elusive.Here,we constructed a mesoscale SSB inside a focused ion beam-scanning electron microscope(FIB-SEM)for in situ observation of Li deposition-induced cracking in SEs at nanometer resolution.Our results revealed that Li propagated predominantly along transgranular cracks in a garnet Li_(6.4)La_(3)Zr_(1.4)Ta_(0.6)O_(12)(LLZTO).Cracks appeared to initiate from the interior of LLZTO beneath the electrode surface and then propagated by curving toward the LLZTO surface.The resulting bowl-shaped cracks resemble those from hydraulic fracture caused by high fluid pressure on the surface of internal cracks,suggesting that the Li deposition-induced pressure is the major driving force of crack initiation and propagation.The high pressure generated by Li deposition is further supported by in situ observation of the flow of filled Li between the crack flanks,causing crack widening and propagation.This work unveils the dynamic interplay between Li deposition and cracking in SEs and provides insight into the mitigation of Li dendrite penetration in SSBs.

The proximity between hydroxyl and single atom determines the catalytic reactivity of Rh1/CeO_(2) single-atom catalysts

The local structure of the metal single-atom site is closely related to the catalytic activity of metal single-atom catalysts(SACs).However,constructing SACs with homogeneous metal active sites is a challenge due to the surface heterogeneity of the conventional support.Herein,we prepared two Rh1/CeO_(2)SACs(0.5Rh1/r-CeO_(2)and 0.5Rh1/c-CeO_(2),respectively)using two shaped CeO_(2)(rod and cube)exposing different facets,i.e.,CeO_(2)(111)and CeO_(2)(100).In CO oxidation reaction,the T100 of 0.5Rh1/r-CeO_(2)SACs is 120°C,while the T100 of 0.5Rh1/c-CeO_(2)SACs is as high as 200°C.Via in-situ CO diffuse reflectance infrared Fourier transform spectroscopy(CO-DRIFTS),we found that the proximity between OH group and Rh single atom on the plane surface plays an important role in the catalytic activity of Rh1/CeO_(2)SAC system in CO oxidation.The Rh single atom trapped at the CeO_(2)(111)crystal surface forms the Rh1(OH)adjacent species,which is not found on the CeO_(2)(100)crystal surface at room temperature.Furthermore,during CO oxidation,the OH group far from Rh single atom on the 0.5Rh1/c-CeO_(2)disappears and forms Rh1(OH)adjacent species when the temperature is above 150°C.The formation of Rh1(OH)adjacentCO intermediate in the reaction is pivotal for the excellent catalytic activity,which explains the difference in the catalytic activity of Rh single atoms on two different CeO_(2)planes.The formed Rh1(OH)adjacent-O-Ce structure exhibits good stability in the reducing atmosphere,maintaining the Rh atomic dispersion after CO oxidation even when pre-reduced at high temperature of 500°C.Density functional theory(DFT)calculations validate the unique activity and reaction path of the intermediate Rh1(OH)adjacentCO species formed.This work demonstrates that the proximity between metal single atom and hydroxyl can determine the formation of active intermediates to affect the catalytic performances in catalysis.

Converting intercalation-type cathode in spent lithium-ion batteries into conversion-type cathode

The widespread applications of lithium-ion batteries(LIBs)generate tons of spent LIBs.Therefore,recycling LIBs is of paramount importance in protecting the environment and saving the resources.Current commercialized LIBs mostly adopt layered oxides such as LiCoO_(2)(LCO)or LiNi_(x)Co_(y)Mn_(1-x-y)O_(2)(NMC)as the cathode materials.Converting the intercalation-type spent oxides into conversion-type cathodes(such as metal fluorides(MFs))offers a valid recycling strategy and provides substantially improved energy densities for LIBs.Herein,two typical Co-based cathodes,LCO and LiNi_(0.6)Co_(0.2)Mn_(0.2)O_(2)(NMC622),in spent LIBs were successfully converted to CoF_(2) and(Ni_(x)Co_(y)Mn_(z))F_(2) cathodes by a reduction and fluorination technique.The as converted CoF_(2) and(Ni_(x)Co_(y)Mn_(z))F_(2) delivered cell energy densities of 650 and 700 Wh/kg,respectively.Advanced atomic-level electron microscopy revealed that the used LCO and NMC622 were converted to highly phase pure Co metal and Ni_(0.6)Co_(0.2)Mn_(0.2) alloys in the used graphite-assisted reduction roasting,simultaneously producing the important product of Li_(2)CO_(3) using only environment friendly solvent.Our study provided a versatile strategy to convert the intercalation-type Co-based cathode in the spent LIBs into conversion-type MFs cathodes,which offers a new avenue to recycle the spent LIBs and substantially increase the energy densities of next generation LIBs.

In situ TEM visualization of Ag catalysis in Li-O_(2)nanobatteries

Lithium-oxygen(Li-O_(2))batteries have been considered as an ideal solution to solving the global energy crisis.Silver(Ag)and Agbased catalyst have been extensively studied due to their high catalytic activities in Li-O_(2)batteries.However,it remains a challenge to track the catalytic mechanism during the charge/discharge process.Here,a nanoscale processing method was used to assemble a Li-O_(2)nanobattery in an aberration-corrected environmental transmission electron microscope(ETEM),where a single Ag nanowire(NW)was used as catalyst for O_(2)electrode.A visualization of the lithium ion insertion process during the electrochemical reactions was achieved in this nanobattery.Numerous Ag nanoparticles(NPs)were observed on the surface of the Ag NW,which were covered by the discharge product Li2O_(2).By simultaneously studying the evolution of the interface and the phase transformation,it can be concluded that these Ag NPs wrapped around Ag NW acted as catalyst during the subsequent charge/discharge reaction.Based on these studies,Ag NPs decorated on porous carbon were synthesized,it can simultaneously improve the cycling stability(100 cycles)and the maximum specific capacity(17,371 mAh·g^(−1)at a current density of 100 mA·g^(−1))in a coin cell Li-O_(2)battery.This study suggests that nanoscale Ag may be a promising catalyst for Li-O_(2)battery.

Atomically dispersed Zn-Co-N-C catalyst boosting efficient and robust oxygen reduction catalysis in acid via stabilizing Co-N bonds

Transition metal supported N-doped carbon(M-N-C)catalysts for oxygen reduction reaction(ORR)are viewed as the promising candidate to replace Pt-group metal(PGM)for proton exchange membrane fuel cells(PEMFCs).However,the stability of M-N-C is extremely challenging due to the demetalation,H_(2)O_(2)attack,etc.in the strongly oxidative conditions of PEMFCs.In this study,we demonstrate the universal effect of Zn on promoting the stability of atomically dispersed M-Nx/C(M=Co,Fe,Mn)catalysts and the enhancement mechanism is unveiled for the first time.The best-performing dual-metal-site Zn-Co-N-C catalyst exhibits a high half-wave potential(E1/2)value of 0.81 V vs.reversible hydrogen electrode(RHE)in acid and outstanding durability with no activity decay after 15,000 accelerated degradation test(ADT)cycles at 60℃,surpassing most reported Co-based PGM-free catalysts in acid media.For comparison,the Co-N-C in the absence of Zn suffers from a rapid degradation after ADT due to the demetalation and higher H_(2)O_(2)yield.X-ray adsorption spectroscopy(XAS)and density functional theory(DFT)calculations suggest the more negative formation energy(by 1.2 eV)and increased charge transfer of Zn-Co dual-site structure compared to Co-N-C could strength the Co-N bonds against the demetalation and the optimized d-band center accounts for the improved ORR kinetics.

Boosting the energy density of sulfide-based all-solid-state batteries at low temperatures by charging to high voltages up to 6 V

Sulfide electrolyte-based all-solid-state batteries(ASSBs)are potential next generation energy storage technology due to the high ionic conductivity of sulfide electrolytes and potentially improved energy density and safety.However,the performance of ASSBs at/below subzero temperatures has not been explored systematically.Herein,low temperature(LT)performance of LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2)(NCM811)|Li_(9.54)Si_(1.74)P_(1.44)S11.7Cl_(0.3)(LiSPSCl)|Li_(4)Ti_(5)O_(12)(LTO)ASSBs was investigated.By charging the ASSB to 6 V at−40℃,a capacity of 100.7 mAh∙g^(−1)at 20 mA∙g^(−1)was achieved,which is much higher than that charged to 4.3 V(4.6 mAh∙g^(−1))at−40℃.Moreover,atomic resolution microscopy revealed that the NCM811 remained almost intact even after being charged to 6 V.In contrast,NCM811 was entirely destructed when charged to 6 V at room temperature.The sharp difference arises from the large internal charge transfer resistance at LT which requires high voltage to overcome.Nevertheless,such high voltage is not harmful to the active material but beneficial to extracting most energy out of the ASSBs at LT.We also demonstrated that thinner electrolyte is favorable for LT operation of ASSBs due to the reduced ion transfer distance.This work provides new strategies to boost the capacity and energy density of sulfide-based ASSBs at LT for dedicated LT applications.

Tailoring lithium concentration in alloy anodes for long cycling and high areal capacity in sulfide-based all solid-state batteries

Lithium–indium(Li-In)alloys are important anode materials for sulfide-based all-solid-state batteries(ASSBs),but how different Li concentrations in the alloy anodes impact the electrochemical performance of ASSBs remains unexplored.This paper systematically investigates the impact that different Li concentrations in Li-In anodes have on the performance of ASSBs.We show that In with 1 wt%Li(LiIn-1)exhibits the best performance for ASSBs among all the tested Li-In anodes.In essence,LiIn-1 not only provides sufficient Li to compensate for first-cycle capacity loss in the anode but also facilitates the formation of a LiIn alloy phase that has the best charge transfer kinetics among all the Li_(x) In alloy phases.The ASSB with a LiIn-1 anode and a LiNi_(0.8)Mn_(0.1)Co_(0.1)O_(2) cathode reached 3400 cycles at an initial capacity of 125 mAh/g.Remarkably,ASSBs with a high cathode active material(CAM)loading of 36 mg/cm 2 delivered a high areal capacity of 4.05 mAh/cm^(2) at high current density(4.8 mA/cm^(2)),with a capacity retention of 92% after 740 cycles.At an ultra-high CAM loading of 55.3 mg/cm^(2),the ASSB achieved a stable areal capacity of 8.4 mAh/cm^(2) at current density of 1.7 mA/cm 2.These results bring us one step closer to the practical application of ASSBs.

In situ observation of cracking and self-healing of solid electrolyte interphases during lithium deposition

The growth of lithium(Li)whiskers is detrimental to Li batteries.However,it remains a challenge to directly track Li whisker growth.Here we report in situ observations of electrochemically induced Li deposition under a CO_(2) atmosphere inside an environmental transmission electron microscope.We find that the morphology of individual Li deposits is strongly influenced by the competing processes of cracking and self-healing of the solid electrolyte interphase(SEI).When cracking overwhelms self-healing,the directional growth of Li whiskers predominates.In contrast,when self-healing dominates over cracking,the isotropic growth of round Li particles prevails.The Li deposition rate and SEI constituent can be tuned to control the Li morphologies.We reveal a new“weak-spot”mode of Li dendrite growth,which is attributed to the operation of the Bardeen-Herring growth mechanism in the whisker’s cross section.This work has implications for the control of Li dendrite growth in Li batteries.

In-situ imaging the electrochemical reactions of Li-CO_(2) nanobatteries at high temperatures in an aberration corrected environmental transmission electron microscope

Rechargeable lithium-carbon dioxide(Li-CO_(2))batteries have attracted much attention due to their high theoretical energy densities and capture of C0_(2).However,the electrochemical reaction mechanisms of rechargeable Lo-CO_(2) batteries,particularly the decomposition mechanisms of the discharge product Li_(2)CO_(3) are still unclear,impeding their practical applications.Exploring electrochemistry of Li_(2)CO_(3) is critical for improving the performance of Li-C0_(2) batteries.Herein,in-situ environmental transmission electron microscopy(ETEM)technique was used to study electrochemistry of Li_(2)CO_(3) in Li-C0_(2) batteries during discharge and charge processes.During discharge,Li_(2)CO_(3) was nucleated and accumulated on the surface of the cathode media such as carbon nanotubes(CNTs)and Ag nanowires(Ag NWs),but it was hard to decompose during charging at room temperature.To promote the decomposition of Li2C03,the charge reactions were conducted at high temperatures,during which Li_(2)CO_(3) was decomposed to lithium with release of gases.Density functional theory(DFT)calculations revealed that the synergistic effect of temperature and biasing facilitates the decomposition of Li_(2)CO_(3).This study not only provides a fundamental understanding to the high temperature Li-C0_(2) nanobatteries,but also offers a valid technique,i.e.,discharging/charging at high temperatures,to improve the cyclability of Li-CO_(2) batteries for energy storage applications.

In situ observation of electrochemical Ostwald ripening during sodium deposition

Sodium(Na)metal batteries(SMBs)using Na anode are potential“beyond lithium”electrochemical technology for future energy storage applications.However,uncontrollable Na dendrite growth has plagued the application of SMBs.Understanding Na deposition mechanisms,particularly the early stage of Na deposition kinetics,is critical to enable the SMBs.In this context,we conducted in situ observations of the early stage of electrochemical Na deposition.We revealed an important electrochemical Ostwald ripening(EOR)phenomenon which dictated the early stage of Na deposition.Namely,small Na nanocrystals were nucleated randomly,which then grew.During growth,smaller Na nanocrystals were contained by bigger ones via EOR.We observed two types of EOR with one involving only electrochemical reaction driven by electrochemical potential difference between bigger and smaller nanocrystals;while the other being dominated by mass transport governed by surface energy minimization.The results provide new understanding to the Na deposition mechanism,which may be useful for the development of SMB for energy storage applications.