Thin polymer electrolyte with MXene functional layer for uniform Li^(+) deposition in all-solid-state lithium battery

Solid polymer electrolyte(SPE) shows great potential for all-solid-state batteries because of the inherent safety and flexibility;however, the unfavourable Li+deposition and large thickness hamper its development and application. Herein, a laminar MXene functional layer-thin SPE layer-cathode integration(MXene-PEO-LFP) is designed and fabricated. The MXene functional layer formed by stacking rigid MXene nanosheets imparts higher compressive strength relative to PEO electrolyte layer. And the abundant negatively-charged groups on MXene functional layer effectively repel anions and attract cations to adjust the charge distribution behavior at electrolyte–anode interface. Furthermore,the functional layer with rich lithiophilic groups and outstanding electronic conductivity results in low Li nucleation overpotential and nucleation energy barrier. In consequence, the cell assembled with MXene-PEO-LFP, where the PEO electrolyte layer is only 12 μm, much thinner than most solid electrolytes, exhibits uniform, dendrite-free Li+deposition and excellent cycling stability. High capacity(142.8 mAh g-1), stable operation of 140 cycles(capacity decay per cycle, 0.065%), and low polarization potential(0.5 C) are obtained in this Li|MXene-PEO-LFP cell,which is superior to most PEO-based electrolytes under identical condition. This integrated design may provide a strategy for the large-scale application of thin polymer electrolytes in all-solid-state battery.

Lithiophilic CoF_(2)@C hollow spheres towards spatial lithium deposition for stable lithium metal batteries

Lithium metal(LM)is a promising anode for next-generation batteries due to its high theoretical capacity and low electrode potential.Nonetheless,side reactions,volume change,and unwanted lithium dendrite growth seriously limit the practical application of LM.Herein,with the aid of a hard template approach,a novel lithiophilic CoF_(2)-carbon hollow sphere(CoF_(2)@C-HS)composite material is successfully prepared via a facile in-situ fluorination and etching strategy.The lithiophilic CoF_(2) acts as nucleation sites to reduce nucleation overpotential as well as induces the spatial Li deposition and the formation of LiFrich solid electrolyte interphase(SEI),and the hollow carbon matrix can enhance the electrical conductivity and offer free space for LM deposition.Theoretical simulations reveal that the synergistic effect of lithiophilic CoF_(2) and hollow carbon matrix homogenizes the electric field distribution and Li~+flux.Benefiting from these advantages,the CoF_(2)@C-HS-modified copper substrate electrode delivers an enhanced Coulombic efficiency(CE)of 93.7%for 280 cycles at 1 mA cm^(-2)and 1 mA h cm^(-2).The symmetrical cell using CoF_(2)@C-HS can stably cycle more than 1800 h with a low voltage hysteresis of 11 mV at a current density of 0.5 MA cm^(-2)and an areal capacity of 0.5 mA h cm^(-2).Moreover,the Li@CoF_(2)@C-HS composite anode enables more than 300 stable cycles at 1 C with a capacity retention of 95%in LiFePO_(4)-based full cell and 110 stable cycles at 1 C in LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2)(NCM811)-based highvoltage full cell.This work might shed a new light on designing lithiophilic hosts to spatially confine LM deposition,realizing dendrite-free LM anodes and the practical applications of LM batteries.

Classification and mineralization of global lithium deposits and lithium extraction technologies for exogenetic lithium deposits

A reasonable classification of deposits holds great significance for identifying prospecting targets and deploying exploration. The world ’s keen demand for lithium resources has expedited the discovery of numerous novel lithium resources. Given the presence of varied classification criteria for lithium resources presently, this study further ascertained and classified the lithium resources according to their occurrence modes, obtaining 10 types and 5 subtypes of lithium deposits(resources) based on endogenetic and exogenetic factors. As indicated by surveys of Cenozoic exogenetic lithium deposits in China and abroad,the formation and distribution of the deposits are primarily determined by plate collision zones, their primary material sources are linked to the anatectic magmas in the deep oceanic crust, and they were formed primarily during the Miocene and Late Paleogene. The researchers ascertained that these deposits,especially those of the salt lake, geothermal, and volcanic deposit types, are formed by unique slightly acidic magmas, tend to migrate and accumulate toward low-lying areas, and display supernormal enrichment. However, the material sources of lithium deposits(resources) of the Neopaleozoic clay subtype and the deep brine type are yet to be further identified. Given the various types and complex origins of lithium deposits(resources), which were formed due to the interactions of multiple spheres, it is recommended that the mineralization of exogenetic lithium deposits(resources) be investigated by integrating tectono-geochemistry, paleoatmospheric circulation, and salinology. So far, industrialized lithium extraction is primarily achieved in lithium deposits of the salt lake, clay, and hard rock types. The lithium extraction employs different processes, with lithium extraction from salt lake-type lithium deposits proving the most energy-saving and cost-effective.

Premature deposition of lithium polysulfide in lithium-sulfur batteries

Lithium-sulfur(Li-S)batteries have attracted extensive attention due to ultrahigh theoretical energy density of 2600 Wh kg^(-1).Liquid-solid deposition from dissolved lithium polysulfides(LiPSs)to solid lithium sulfide(Li_(2)S)largely determines the actual battery performances.Herein,a premature liquidsolid deposition process of LiPSs is revealed at higher thermodynamic potential than Li_(2)S deposition in Li-S batteries.The premature solid deposit exhibits higher chemical state and hemispherical morphology in comparison with Li_(2)S,and the premature deposition process is slower in kinetics and higher in deposition dimension.Accordingly,a supersaturation deposition mechanism is proposed to rationalize the above findings based on thermodynamic simulation.This work demonstrates a unique premature liquid-solid deposition process of Li-S batteries.

Spatial Control of Lithium Deposition by Controlling the Lithiophilicity with Copper(Ⅰ)Oxide Boundaries

Spatial control of lithium deposition is the most important issue in lithium-metal batteries because of the considerable control of lithium dendrite suppression via the uniform distribution of Li^(+)flux.Although seed materials are crucial for the behavior of lithium deposition,in-depth studies on their physical and chemical control have not been conducted.Here,we describe a new design of seed structure comprising a wrinkled Cu/graphene substrate surrounded by copper(Ⅰ)oxide(Cu_(2)O)on a graphene grain boundary over a large area,which is fabricated by the oxidation of the Cu surface via graphene boundary defects by using chemical vapor deposition(CVD).Scanning and transmission electron microscopy results reveal that Cu_(2)O on the graphene boundary can render a preferential reaction with lithium during the first deposition and assist in the uniform deposition of lithium by preventing the agglomeration of lithium clusters during the second deposition.This two-step process is attributed to the degree of selectivity due to the difference in lithium affinity,which allows long-term electrochemical stability and a high rate capability via boundary effects.This study highlights the significance of the boundary effect,which can open new avenues for the formation of a large family of seed structures in lithium-metal batteries.

Genesis of the Jiajika superlarge lithium deposit,Sichuan,China:constraints from He–Ar–H–O isotopes

The Jiajika granitic-and pegmatite-type lithium deposit,which is in the Songpan-Garze Orogenic Belt in western Sichuan Province,China,is the largest in Asia.Previous studies have examined the geochemistry and mineralogy of pegmatites and their parental source rocks to determine the genesis of the deposit.However,the evolution of magmatic-hydrothermal fluids has received limited attention.We analyzed He–Ar–H–O isotopes to decipher the ore-fluid nature and identify the contribution of fluids to mineralization in the late stage of crystallization differentiation.In the Jiajika ore field,two-mica granites,pegmatites(including common pegmatites and spodumene pegmatites),metasandstones,and schists are the dominant rock types exposed.Common pegmatites derived from early differentiation of the two-mica granitic magmas before they evolved into spodumene pegmatites during the late stage of the magmatic evolution.Common pegmatites have~3He/~4He ratios that vary from 0.18 to 4.68 Ra(mean1.62 Ra),and their~(40)Ar/~(36)Ar ratios range from 426.70 to 1408.06(mean 761.81);spodumene pegmatites have~3He/~4He ratios that vary from 0.18 to 2.66 Ra(mean 0.87Ra)and their~(40)Ar/~(36)Ar ratios range from 402.13 to 1907.34(mean 801.65).These data indicate that the hydrothermal fluids were shown a mixture of crust-and mantle-derived materials,and the proportion of crustderived materials in spodumene pegmatites increases significantly in the late stage of the magmatic evolution.Theδ~(18)OH_(2)O–VSMOWvalues of common pegmatites range from 6.2‰to 10.9‰,with a mean value of 8.6‰,andδDV–SMOWvalues vary from-110‰to-72‰,with a mean o f-85‰.Theδ~(18)OH_(2)O–VSMOWvalues of spodumene pegmatites range from 5.3‰to 13.2‰,with a mean of 9.1‰,andδDV–SMOWvalues vary from-115‰to-77‰,with a mean of-91‰.These data suggest that the ore-forming fluids came from primary magmatic water gradually mixing with more meteoric water in the late stage of the magmatic evolution.Based on the He–Ar–H–O and other existing data,we propose that the oreforming metals are mainly derived from the upper continental crust with a minor contribution from the mantle,and the fluid exsolution and addition of meteoric water during the formation of pegmatite contributed to the formation of the Jiajika superlarge lithium deposit.

2.5μm-Thick Ultrastrong Asymmetric Separator for Stable Lithium Metal Batteries

Lithium metal batteries(LMBs)are considered the ideal choice for high volumetric energy density lithium-ion batteries,but uncontrolled lithium deposition poses a significant challenge to the stability of such devices.In this paper,we introduce a 2.5μm-thick asymmetric and ultrastrong separator,which can induce tissue-like lithium deposits.The asymmetric separator,denoted by utPE@Cu_(2)O,was prepared by selective synthesis of Cu_(2)O nanoparticles on one of the outer surfaces of a nanofibrous(diameter~10 nm)ultrastrong ultrahigh molecular weight polyethylene(UHMWPE)membrane.Microscopic analysis shows that the lithium deposits have tissue-like morphology,resulting in the symmetric lithium cells assembled using utPE@Cu_(2)O with symmetric Cu_(2)O coating exhibiting stable performance for over 2000 h of cycling.This work demonstrates the feasibility of a facile approach ultrathin separators for the deployment of lithium metal batteries,providing a pathway towards enhanced battery performance and safety.

Insight into demand-driven preparation of single-atomic mediators for lithium–sulfur batteries

Lithium-sulfur(Li-S) batteries have attracted considerable attention as one of the most appealing energy storage systems.Strenuous efforts have been devoted to tackling the tremendous challenges,mainly pertaining to the severe shuttle effect,sluggish redox kinetics and lithium dendritic growth.Single-atomic mediators as promising candidates exhibit impressive performance in addressing these intractable issues.Related research often utilizes a trial-and-error approach,proposing solutions to fabricate single-atomic materials with diversified features.However,comprehensive review articles especially targeting demand-driven preparation are still in a nascent stage.Inspired by these considerations,this review summarizes the design of single-atomic mediators based on the application case-studies in LiS batteries and other metal-sulfur systems.Emerging preparation routes represented by chemical vapor deposition technology are introduced in a demand-oriented classification.Finally,future research directions are proposed to foster the advancement of single-atomic mediators in Li-S realm.

Preparation and electrochemical lithium storage performance of porous silicon microsphere composite with metal modification and carbon coating

This work adopts a multi⁃step etching⁃heat treatment strategy to prepare porous silicon microsphere com⁃posite with Sb⁃Sn surface modification and carbon coating(pSi/Sb⁃Sn@C),using industrial grade SiAl alloy micro⁃spheres as a precursor.pSi/Sb⁃Sn@C had a 3D structure with bimetallic(Sb⁃Sn)modified porous silicon micro⁃spheres(pSi/Sb⁃Sn)as the core and carbon coating as the shell.Carbon shells can improve the electronic conductivi⁃ty and mechanical stability of porous silicon microspheres,which is beneficial for obtaining a stable solid electrolyte interface(SEI)film.The 3D porous core promotes the diffusion of lithium ions,increases the intercalation/delithia⁃tion active sites,and buffers the volume expansion during the intercalation process.The introduction of active met⁃als(Sb⁃Sn)can improve the conductivity of the composite and contribute to a certain amount of lithium storage ca⁃pacity.Due to its unique composition and microstructure,pSi/Sb⁃Sn@C showed a reversible capacity of 1247.4 mAh·g^(-1) after 300 charge/discharge cycles at a current density of 1.0 A·g^(-1),demonstrating excellent rate lithium storage performance and enhanced electrochemical cycling stability.

A layered multifunctional framework based on polyacrylonitrile and MOF derivatives for stable lithium metal anode

Composite Li metal anodes based on three-dimensional(3D) porous frameworks have been considered as an effective material for achieving stable Li metal batteries with high energy density.However,uneven Li deposition behavior still occurs at the top of 3D frameworks owing to the local accumulation of Li ions.To promote uniform Li deposition without top dendrite growth,herein,a layered multifunctional framework based on oxidation-treated polyacrylonitrile(OPAN) and metal-organic framework(MOF) derivatives was proposed for rationally regulating the distribution of Li ions flux,nucleation sites,and electrical conductivity.Profiting from these merits,the OPAN/carbon nano fiber-MOF(CMOF) composite framework demonstrated a reversible Li plating/stripping behavior for 500 cycles with a stable Coulombic efficiency of around 99.0% at the current density of 2 mA/cm~2.Besides,such a Li composite anode exhibited a superior cycle lifespan of over 1300 h under a low polarized voltage of 18 mV in symmetrical cells.When the Li composite anode was paired with LiFePO_(4)(LFP) cathode,the obtained full cell exhibited a stable cycling over 500 cycles.Moreover,the COMSOL Multiphysics simulation was conducted to reveal the effects on homogeneous Li ions distribution derived from the above-mentioned OPAN/CMOF framework and electrical insulation/conduction design.These electrochemical and simulated results shed light on the difficulties of designing stable and safe Li metal anode via optimizing the 3D frameworks.

The Metallogenetic Regularities of Lithium Deposits in China

Lithium resources support the development of high-technology industries. China has abundant lithium resources which are mainly distributed in Tibet, Qinghai, Sichuan and Jiangxi. Salt lakes in China have significant lithium reserves, but lithium is mainly produced from hard rock lithium deposits because the extraction from salt lakes requires further improvements. The hard rock lithium deposits mainly occur in granitic pegmatite in the Altay region of Xinjiang and the Jiajika deposit in western Sichuan Province; they mainly formed in the Mesozoic and occurred in a relatively stable stage during orogenic processes. On the basis of the information from 151 lithium deposits or spots, 14 lithium metallogenic series were identified, and granitic pegmatite, granite, and sedimentary types were considered to be the main prediction types of lithium resources. Twelve lithium mineralization belts were divided and a series of maps showing the lithium metallogenetic regularity in China were drawn. We conclude that the hard rock and brine type of lithium resources possibly have a similar lithium source related to magmatism. The mctallogenic features of the lithium in China were related with the distinct history of tectonic-magmatic activity in China. This study benefits the assessment of, and prospecting for, lithium resources in China.

Fluid Characteristics and Evolution of the Zhawulong Granitic Pegmatite Lithium Deposit in the Ganzi-Songpan Region, Southwestern China

The Zhawulong granitic pegmatite lithium deposit is located in the Ganzi-Songpan orogenic belt.Fluid inclusions in spodumene and coexisting quartz were studied to understand the cooling path and evolution of fluid within albite–spodumene pegmatite.There are three distinguishable types of fluid inclusions:crystal-rich,CO2–NaCl–H2 O,and NaCl–H2 O.At more than 500°C and 350~480 MPa,crystal-rich fluid inclusions were captured during the pegmatitic magma-hydrothermal transition stage,characterized by a dense hydrous alkali borosilicate fluid with a carbonate component.Between 412°C and 278°C,CO2–Na Cl–H2 Ofluid inclusions developed in spodumene(I)and quartz(II)with a low salinity(3.3–11.9 wt%NaCl equivalent)and a high volatile content,which represent the boundary between the transition stage and the hydrothermal stage.The subsequentNaCl–H2 Ofluid inclusions from the hydrothermal stage,between 189°C and 302°C,have a low salinity(1.1–13.9 wt%NaCl equivalent).The various types of fluid inclusions reveal the P–T conditions of pegmatite formation,which marks the transition process from magmatic to hydrothermal.The oreforming fluids from the Zhawulong deposit have many of the same characteristics as those from the Jiajika lithium deposit.The ore-forming fluid provided not only materials for crystallization of rare metal minerals,such as spodumene and beryl,but also the ideal conditions forthe growth of ore minerals.Therefore,this area has favorable conditions for lithium enrichment and excellent prospecting potential.

Mechanism of Capacity Fading Caused by Mn(Ⅱ)Deposition on Anodes for Spinel Lithium Manganese Oxide Cell

The capacity fade of spinel lithium manganese oxide in lithium-ion batteries is a bottleneck challenge for the large-scale application.The traditional opinion is that Mn（Ⅱ） ions in the anode are reduced to the metallic manganese that helps for catalyzing electrolyte decomposition.This could poison and damage the solid electrolyte interface（SEI） film,leading to the the capacity fade in Li-ion batteries.We propose a new mechanism that Mn（Ⅱ） deposites at the anode hinders and/or blocks the intercalation/de-intercalation of lithium ions,which leads to the capacity fade in Li-ion batteries.Based on the new mechanism assumption,a kind of new structure with core-shell characteristic is designed to inhabit manganese ion dissolution,thus improving electrochemical cycle performance of the cell.By the way,this mechanism hypothesis is also supported by the results of these experiments.The LiMn2-xTixO4 shell layer enhances cathode resistance to corrosion attack and effectively suppresses dissolution of Mn,then improves battery cycle performance with LiMn_2O_4 cathode,even at high rate and elevated temperature.

New Data on Lithium Isotopic Geochemistry of the No. X03 Lithium Vein in the Jiajika Super-Large Lithium Deposit, Sichuan, China

Objective The No.X03 lithium pegmatite vein in the Jiajika lithium deposit in western Sichuan is a newly discovered super-large vein which contains an identified reserves of643,100 tons Li2O.Lithium has two stable isotopes(~6Li and^7Li),and^6Li is a key raw material for nuclear fusion.Significant fractionation of lithium isotopes is almost nonexistent during partial melting。

Geological characteristics,metallogenic regularity,and research progress of lithium deposits in China

China is rich in abundant lithium resources characterized by considerable reserves and a concentrated distribution of metallogenic zones or belts,with proven reserves of 4046.8×10^(3) t(calculated based on Li_(2)O)by 2021.China is also a big consumer of lithium.By 2019,China’s lithium consumption in the battery sector alone had reached 99×10^(3) t,with an average annual growth rate of nearly 26%.China has become the world’s largest importer of lithium resources,showing a severely unbalanced relationship between supply and demand for lithium resources.Therefore,there is an urgent need for the prospecting,exploitation,and study of lithium resources in China.This study collected,organized,and summarized the data on the major lithium deposits in China,analyzed and compared the spatial-temporal distribution patterns,geological characteristics,and metallogenic regularity of these lithium deposits,and summarized the prospecting and research achievements over the last decade.The major lithium deposits in China are distributed in provinces and regions such as Qinghai,Jiangxi,Sichuan,Tibet,and Xinjiang.These deposits are mostly small in scale.According to different genetic types,this study divided lithium deposits into granitic pegmatite type,granite type,saline lake brine type,underground brine type,and sedimentary type,as well as new types including hot spring type and magmatic-hydrothermal type,and summarized the characteristics and key metallogenic factors of these different types of deposits.Sixteen metallogenic prospect areas of lithium deposits were delineated according to the deposit types and the distribution patterns of metallogenic belts.The paper introduced the research progress in major metallogenic models and lithium extraction techniques made over the past decade.Based on the comprehensive analysis of the prospecting potential of lithium deposits,the authors concluded that the future prospecting of lithium resources in China should focus on lithium metallogenic belts,the deep and peripheral areas of currently determined large-scale pegmatite-type lithium deposits,geophysical-geochemical anomalous areas with mineralization clues,and areas with developed large-scale low-grade associated granite-type and sedimentary lithium resources.The study aims to serve as a guide for the future prospecting of lithium deposits in China.

Driving lithium to deposit inside structured lithium metal anodes:A phase field model

Lithium metal anode is one of the most important anode materials for next-generation high-specificenergy secondary batteries.Structured lithium metal anodes have received extensive attention in the development of practical lithium metal batteries.Methods of driving lithium metal to deposit inside the pores of structured lithium metal anodes have always been one of the most concerned issues,especially for highly conductive frameworks.An electrochemical phase field theory with galvanostatic lithium plating process is employed in this work,the mechanism that illustrates the preference of lithium metal to deposit at the top of the framework structure has been revealed,and through the simulation analysis of various regulating strategies,the strategies that can efficiently drive lithium to deposit inside structured pores are summarized.This work presents the theoretical calculation and analysis methods that can be used for the rational design of lithium metal batteries.

Artificial solid electrolyte interphase based on polyacrylonitrile for homogenous and dendrite-free deposition of lithium metal

High chemical reactivity, large volume changes, and uncontrollable lithium dendrite growth have always been the key problems of lithium metal anodes.Coating has been demonstrated as an effective strategy to protect the lithium metal.In this work, the effects of polyacrylonitrile(PAN)-based coatings on electrodeposited lithium have been studied.Our results show that a PAN coating layer provides uniform and dendrite-free lithium deposition as well as better cycling performance with carbonate electrolyte.Notably, heat treatment of the PAN coating layer promotes the formation of larger deposit particle size and higher coulombic efficiency(85%).The compact coating layer of heat-treated PAN with a large Young modulus(82.7 GPa) may provide stable protection for the active lithium.Improved homogeneity of morphology and mechanical properties of heat-treated PAN contribute to the larger deposit particles.This work provides new feasibility to optimize the polymer coating through rational modification of polymers.

Dendrite‑Free and Stable Lithium Metal Battery Achieved by a Model of Stepwise Lithium Deposition and Stripping

The uncontrolled formation of lithium(Li)dendrites and the unnecessary consumption of electrolyte during the Li plating/stripping process have been major obstacles in developing safe and stable Li metal batteries.Herein,we report a cucumber-like lithiophilic composite skeleton(CLCS)fabricated through a facile oxidationimmersion-reduction method.The stepwise Li deposition and stripping,determined using in situ Raman spectra during the galvanostatic Li charging/discharging process,promote the formation of a dendrite-free Li metal anode.Furthermore,numerous pyridinic N,pyrrolic N,and CuxN sites with excellent lithiophilicity work synergistically to distribute Li ions and suppress the formation of Li dendrites.Owing to these advantages,cells based on CLCS exhibit a high Coulombic efficiency of 97.3%for 700 cycles and an improved lifespan of 2000 h for symmetric cells.The full cells assembled with LiFePO_(4)(LFP),SeS_(2) cathodes and CLCS@Li anodes demonstrate high capacities of 110.1 mAh g^(−1) after 600 cycles at 0.2 A g^(−1) in CLCS@Li|LFP and 491.8 mAh g^(−1) after 500 cycles at 1 A g^(−1) in CLCS@Li|SeS2.The unique design of CLCS may accelerate the application of Li metal anodes in commercial Li metal batteries.

High-performance LiNi_(0.8)Mn_(0.1)Co_(0.1)O_(2) cathode by nanoscale lithium sulfide coating via atomic layer deposition

The commercialization of nickel-rich LiNi_(0.8)Mn_(0.1)Co_(0.1)O_(2)(NMC811) has been hindered by its continuous loss of practical capacity and reduction in average working voltage.To address these issues,surface modification has been well-recognized as an effective strategy.Different from the coatings reported in literature to date,in this work,we for the first time report a sulfide coating,amorphous Li_(2)S via atomic layer deposition (ALD).Our study revealed that the conformal nano-Li_(2)S coating shows exceptional protection over the NMC811 cathodes,accounting for the dramatically boosted capacity retention from~11.6%to~71%and the evidently mitigated voltage reduction from 0.39 to 0.18 V after 500 charge–discharge cycles.In addition,the Li_(2)S coating remarkably improved the rate capability of the NMC811 cathode.Our investigation further revealed that all these beneficial effects of the ALD-deposited nano-Li_(2)S coating lie in the following aspects:(i) maintain the mechanical integrity of the NMC811 electrode:(ii) stabilize the NMC electrode/electrolyte interface:and (iii) suppress the irreversible phase transition of NMC structure.Particularly,this study also has revealed that the nano-Li_(2)S coating has played some unique role not associated with traditional non-sulfide coatings such as oxides.In this regard,we disclosed that the Li_(2)S layer has reacted with the released O_(2) from the NMC lattices,and thereby has dramatically mitigated electrolyte oxidation and electrode corrosion.Thus,this study is significant and has demonstrated that sulfides may be an important class of coating materials to tackle the issues of NMCs and other layered cathodes in lithium batteries.

Fabrication of multi-shell coated silicon nanoparticles via in-situ electroless deposition as high performance anodes for lithium ion batteries

Si-based materials have been extensively studied because of their high theoretical capacity,low working potential,and abundant reserves,but serious initial irreversible capacity loss and poor cyclic performance resulting from large volume change of Si during lithiation and delithiation processes restrict their widespread application.Herein,we report the preparation of multi-shell coated Si(DS-Si)nanocomposites by in-situ electroless deposition method using Si granules as the active materials and copper sulfate as Cu sources.The ratio of Si and Cu was readily tuned by varying the concentration of copper sulfate.The multi-shell(Cu@CuxSi/SiO2)coating on Si surface promotes the formation of robust and dense SEI films and the transportation of electron.Thus,the obtained DS-Si composites exhibit an initial coulombic efficiency of 86.2%,a capacity of 1636 mAh g^-1 after 100 discharge-charge cycles at 840 mA g^-1,and an average charge capacity of 1493 mAh g^-1 at 4200 mA g^-1.This study provides a low-cost and large-scale approach to the preparation of nanostructured Si-metal composites anodes with good electrochemical performance for lithium ion batteries.