Biphasic MoO2/Mo2C-Passivated Graphite Anodes for Fast-Charging Lithium-Ion Batteries.

Lithium-ion batteries with nickel-rich layered oxide cathodes and graphite anodes have reached specific energies of 250-300 Wh kg-1 (refs. 1,2), and it is now possible to build a 90 kWh electric vehicle (EV) pack with a 300-mile cruise range. Unfortunately, using such massive batteries to alleviate range anxiety is ineffective for mainstream EV adoption owing to the limited raw resource supply and prohibitively high cost. Ten-minute fast charging enables downsizing of EV batteries for both affordability and sustainability, without causing range anxiety. However, fast charging of energy-dense batteries (more than 250 Wh kg-1 or higher than 4 mAh cm-2) remains a great challenge3,4. Here we combine a material-agnostic approach based on asymmetric temperature modulation with a thermally stable dual-salt electrolyte to achieve charging of a 265 Wh kg-1 battery to 75%(or70%) state of charge in 12(or11) minutes for more than 900(or2,000) cycles. This is equivalent to a half million mile range in which every charge is a fast charge. Further, we build a digital twin of such a battery pack to assess its cooling and safety and demonstrate that thermally modulated 4C charging only requires air convection. This offers a compact and intrinsically safe route to cell-to-pack development. The rapid thermal modulation method to yield highly active electrochemical interfaces only during fast charging has important potential to realize both stability and fast charging of next-generation materials, including anodes like silicon and lithium metal.

While the idea that fast charging batteries could be utilized in electric vehicles is enticing, current fast charging batteries face significant challenges that must be mitigated before this application is realized. Fast charging batteries currently suffer from capacity loss and degradation over time which not only affects battery life but poses a safety hazard. The current electrolyte, 1.2 M LiPF6 in 3:7 wt.% EC/EMC (Gen2), contains the salt LiPF6 that when exposed to moisture can form dangerous hydrofluoric acid and contains a carbonate-based solvent that when exposed to oxygen can ignite. In addition, batteries experience degradation over many cycles of fast charging which results in capacity fade and poor battery performance. However, previous studies have shown the potential for other electrolyte systems to mitigate these problems, specifically by using highly concentrated electrolytes1. These studies claim that using these electrolytes results in the formation of a solid electrolyte interphase (SEI) that passivates Li ions better than the Gen2 electrolyte. The SEI is a layer that forms on the anode within the battery and serves as a protective layer that allows for Li intercalation into graphite and can therefore protect against degradation. By using different electrolytes, a different SEI is formed, and different degradation mechanisms are observed. In this way, the SEI can be tuned to improve Li passivation and ionic conductivity by changing the electrolyte’s composition and concentration2. This research focuses on such alternative electrolyte systems and aims to characterize the different degradation mechanisms corresponding to each electrolyte. Favorable performance has been observed using 1.2 M LiFSI in 3:7 wt.% EC/EMC as an electrolyte. We are studying LiFSI in acetonitrile (AN) at higher concentrations than traditional Gen2 to quantify the SEI. We expect AN to form an anion derived SEI, a composition of which results in improved passivation of Li ions1. In this study, we characterize degradation of alternative electrolyte systems through x-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). Through these methods we can observe and quantify both crystalline, amorphous degradation products due to loss of Li inventory and loss of active material. XPS allows quantification of compositional changes in the SEI layer at the surface of the electrode. The SEM provides qualitative information on degradation such as visualizing lithium plating and dendrite formation. We implement quantitative XRD to measure the crystalline phases of the graphite anode, showing the degree of lithium intercalation and further quantifying degradation such as Li plating. Putting the results of these three characterization techniques together in tandem with electrochemical cycling data paints a picture of the degradation that happens on the anode of a fast-charging lithium-ion battery with respect to electrolyte composition.[1] Yamada, Y., Wang, J., Ko, S., Watanabe, E., & Yamada, A. (2019). Advances and issues in developing salt-concentrated battery electrolytes. Nature Energy. [2] Logan, E. R., & Dahn, J. R. (2020). Electrolyte Design for Fast-Charging Li-ion Batteries. Trends in Chemistry.

To date, commercial LIB cells are mostly based on graphite as anode material. During the first inter­calation of lithium into graphite, the electrolyte gets reduced at the anode, forming a nm-thick surface layer, the so-called solid electrolyte interphase (SEI). The SEI stops further electrolyte reduction, but as it consumes lithium during its formation, there is a loss of active lithium inventory, which causes the irreversible capacity loss during the first cycle of an LIB.[1] Neutron depth profiling (NDP) is a non-destructive technique and a suitable tool to measure lithium concentrations as a function of depth.[2,3] When irradiating the sample with a cold neutron beam, 6Li nuclides emit charged particles after neutron capture. The residual energy and the signal rate of the emitted 3H particles are correlated to depth and amount of lithium, respectively. Thus, SEI growth and lithium (de-)intercalation in graphite anodes can be studied up to a depth of ca. 30 µm. So far, in-situ NDP measurements in LIBs have been limited to thin solid-state cells or to cells with sub-mm thick anodes.[4,5] Here, we present operando NDP data for the first charge/discharge cycle of a 14 mm thick graphite anode (4 mm particles) vs. a capacitively over­sized LiFePO4 cathode, using a custom-designed coin-cell casing with 0.5 mm diameter holes which are sealed with a 7.5 µm-thick Kapton® window. Fig. 1 shows the voltage profile during cycling, demonstrating that the operando cell yields the expected first-cycle discharge capacity of 350 mAh/ggraphite. The higher irreversible capacity of ca. 98 mAh/g (ca. 22%) compared to conventional graphite used in commercial cells (ca. 10%) is due to the very high BET area of ca. 14 m2/g of the 4 µm sized graphite particles. Fig. 2 shows the NDP signals at three different states-of-charge (SOC): i) for the pristine graphite anode (0 h, black line), reflecting the lithium-containing electrolyte (1 M LiPF6 in EC/EMC 3:7 v:v) within the electrode pores; ii) for 100% SOC at the end of the first charge (16 h, red line); and, iii) at the end of the first discharge at again 0% SOC (32 h, blue line). The difference between the red and the blue line indicates that ca. ¼ of the active lithium has been consumed irreversibly for the SEI formation, in good agreement with the electrochemical data.

As the most advanced energy storage devices, lithium ion batteries (LIBs) have captured a great deal of attention and have been developed swiftly during the past decades. However, the improved fast-charging performance is more urgent than ever for time-saving and convenience, which is generally limited by the graphite anode. Recent studies have revealed that the fast-charging performance of graphite anodes is highly dictated by the properties of the electrolyte. Therefore, the investigations on fast-charging graphite based on designs of electrolytes are summarized from two aspects: solid electrolyte interphase (SEI) structures and solvated lithium ion structures. Finally, challenges and prospects for further research toward fast-charging graphite anodes are proposed.

Fast-charging lithium-ion batteries (LIBs) have been severely hampered by the slow development of their electrolytes. Herein, we demonstrate that the size effect of solvent sheath would pose a great effect on the fast-charging performance of LIBs. Three similar ethers, including diethyl ether (DEE), dipropyl ether (DPE), and dibutyl ether (DBE), were mixed with 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (TTE) and lithium bis(fluorosulfonyl)imide (1 M) to form an electrolyte for fast-charging LIBs, respectively. The results showed that it is more difficult to form ternary graphite intercalation compounds (GICs) in the electrolyte with a larger solvation sheath. The DEE electrolyte can form stable GICs and generate an inner LiF-rich solid electrolyte interphase (SEI), lowering the diffusion barrier of Li+. Therefore, the graphite anode powered by the DEE electrolyte can maintain a capacity of 190 mAh g-1 at 4 C after 500 cycles. This kind of size effect of solvation sheath is also applicable to lithium metal batteries.

Suppressing dendritic metallic Li formation on graphite anode under battery fast charging

The initial Coulombic efficiency (ICE) of lithium-ion batteries, quantifying the irreversible Li+ loss during the first cycle, is critical for determining practical energy density. Many electrode materials exhibit substandard ICEs (<90%) due to excessive formation of solid electrolyte interphase (SEI). Traditional strategies modifying SEI formation mainly focus on the generating process but often consume extra Li+ and yield limited improvements. Here, a strategy is introduced that targets the terminating process of SEI formation, usually impeded by interfacial parasitic reactions, to achieve ICEs exceeding 90%. Using TiO2 as a model electrode, it is demonstrated that equivalent chemical fluorination suppresses the parasitic reaction between phosphorus pentafluoride (PF₅) and surface hydroxyl groups (─OH), early terminating SEI formation. Interfacial analysis and theoretical simulations reveal that this approach reduces organic SEI formation while preserving the beneficial LiF-rich inner SEI layer. As a result, the fluorinated TiO2 anode exhibits an ICE of 92.1%, significantly higher than the 74.1% of pristine TiO2, without compromising other electrochemical performance metrics. Pouch cell tests confirm the practical applicability of the method. This work provides deep insights into mechanisms of terminating SEI formation and opens a new pathway for optimizing the battery performances through inherent SEI manipulation.

Lithium-ion batteries are the technology of choice for a broad range of applications due to their performance and long-term stability. The solid electrolyte interphase (SEI) is the key to merge these properties because it enables the combination of low-voltage anodes such as graphite with high performance liquid electrolytes. Direct contact between these phases results in continuous reduction of electrolyte solvent and salt. However, these reduction reactions produce solid SEI particles which quickly form a thin film during the first charge of a pristine graphite electrode. This thin film separates electrode and electrolyte, reducing the rate of electrolyte reduction considerably. However, this reaction is never absolutely suppressed and long-term SEI growth remains the biggest contributor to capacity fade in lithium-ion batteries. Our model describes the long-term evolution of a porous SEI [1]. It extends the approach of previous models [2,3] which describe SEI thickness evolution using a single rate-limiting transport mechanism. In this way, they avoid specifying reaction kinetics because the reaction rate equals the incoming throughput of SEI precursors. We instead consider all potentially rate-limiting transport mechanisms, namely electron conduction and solvent diffusion. These mechanisms transport SEI precursors through the film and its pores, as shown in figure 1. This allows us to trace the evolution of the SEI volume fraction in a spatially resolved way, see figure 2. The first model considers a single representative SEI formation reaction and predicts continuous growth of a porous SEI. Electron conduction drives film growth and thickness evolves with the square-root of time. We show that replacing electron conduction with alternative plausible mechanisms suggested in literature (such as diffusion of neutral lithium interstitials through the SEI [4]) leads to qualitatively similar results. Adding a second SEI formation reaction leads to the formation of a dual-layer SEI. The properties of the additional layer depend on the type of the second reaction, i.e., solvent reduction or reduction of SEI compounds. Furthermore, we predict an equilibrium relation between the thickness of the inner layer and the total SEI thickness. Different SEI profiles generated in our model are studied with impedance simulations of graphite anodes. All predictions above are observable with suitable experimental techniques, such as neutron reflectometry, and can be used for model validation. SEI porosity is an output of our model, when SEI growth is limited by electron conduction. However, structural constraints potentially impose a larger porosity onto the system. Our model can smoothly transition to the other rate-limiting transport mechanism which is solvent diffusion by considering these constraints. This enables us to systematically compare SEI formed by qualitatively different mechanisms. [1] Single, F., Horstmann, B., & Latz, A. (2016). Phys. Chem. Chem. Phys., 18, 17810–17814. doi:10.1039/C6CP02816K [2] Pinson, M. B., & Bazant, M. Z. (2012). Journal of the Electrochemical Society, 160(2), A243–A250. doi:10.1149/2.044302jes [3] Christensen, J., & Newman, J. (2004). Journal of The Electrochemical Society, 151(11), A1977. doi:10.1149/1.1804812 [4] Shi, S., Lu, P., Liu, Z., Qi, Y., Hector, L. G., Li, H., & Harris, S. J. (2012). Journal of the American Chemical Society, 134(37), 15476–15487. doi:10.1021/ja305366r Figure 1

Extreme fast charging (XFC) of lithium-ion batteries (LIBs) in 10 minutes is one of the main goals of the US Advanced Battery Consortium for low-cost, fast-charged electric vehicles by 2023. However, existing LIBs cannot achieve these XFC goals without significant capacity fade over cycling due to complex XFC degradation modes. One of the key XFC failure mechanisms is dead Li plating on the graphite anode. While numerous methods have detected Li plating, they lack three-dimensional non-invasive visualization of dead Li on graphite anodes in full cells during battery cycling. Herein, we demonstrate the viability of high-resolution (spatial resolution: 10–15 μm) neutron micro-computed tomography (μCT) for in-situ characterization of dead Li on graphite anodes (thickness: ~130 μm) in full cells containing NMC cathode, that were cycled at 1C and 6C.

Introduction A solid-electrolyte interphase (SEI) is known to play a significant role on safety and durability of lithium ion batteries (LIBs). Here, the chemical composition of SEI has been usually determined with an ex-situ X-ray photoelectron spectroscopic analysis technique. However, there are few reports on the structural properties of SEI, such as thickness and density, and their variation with cyclic charge and discharge reactions, because of the difficulty for observing SEI with an in-situ manner. This means that we will never reach deep understanding of “alive” SEI and its formation mechanism through the work on “dead” SEI with ex-situ analytical techniques. Therefore, we have started to use neutron reflectivity (NR), as NR is a powerful technique for estimating thickness and density of an interface between solid and liquid. Furthermore, since the interfacial reaction is expected to occur within a few nanometer-thickness from the initial boundary between electrode and electrolyte, we naturally need a NR technique with more precise spatial resolution for such purpose than the past NRs. Fortunately, Japan Proton Accelerator Research Complex (J-PARC) is one of the most intense spallation neutron source, leading to the highest depth resolution of NR in the world. Here, we report the first operando measurement of the SEI formation during the initial charge, i.e. lithiation reaction in the carbon electrode of LIB using a combination of in situ NR and electrochemical analyses [1]. Experimental As an electrode for NR measurements, a carbon/titanium multi-layer film was deposited on a silicon substrate by a magnetron sputtering technique (Fig. 1). Here, the titanium layer is necessary to increase adhesive force between the carbon electrode and Si substrate. In a special electrochemical cell for in-situ NR measurements, the carbon/titanium film was a working electrode, a lithium foil was a counter electrode, 1 mol/L LiPF6 in a 1:1 (v/v) ratio of ethylene carbonate and diethyl carbonate was an electrolyte, and a microporous polyethylene membrane was a separator. Cyclic voltammetry (CV) was performed at a slow sweep rate of 0.2 mV/s between 3.3 and 0.05 V. In situ NR measurements were performed during the repeated charge and discharge, i.e. lithiation and delithiation cycles on the surface profile analysis reflectometer (SOFIA) at BL16 of Materials and Life Science Experimental Facility (MLF) in J-PARC (Proposal No.2015B0016). The NR spectrum was measured as a function of the momentum transfer, Qz = (4π/λ)sin θ, in the Qz range between 0.1 and about 0.45 nm-1. The obtained NR spectra were fitted with Motofit based on a Parratt formalism [2] [3]. Results and Discussion After the CV measurement, the morphology of the carbon surface was clearly changed as expected. Fig. 2 shows a color map of the reflectivity profiles in the Qz and time plane for the 1st and 2nd charge and discharge cycles in order to demonstrate the overall data for the present NR measurements. NR is found to drastically change at potentials between 1.5 and 0.05 V corresponding to the lithiation reaction, and between 0.05 and 2.5 V corresponding to the delithiation reaction. The change in NR along the Qz axis naturally reflects the formation and variation of SEI. Fig. 3 shows the Scattering length density (SLD) as a function of depth and time. The data were obtained by fitting the NR spectra with a four-layer model. The change in thickness of carbon electrode indicates the volumetric change induced by the lithiation and delithiation reactions into and from carbon. The decrease in SLD of carbon also supports the lithiation reaction into carbon, because Li exhibits a negative coherent scattering length. More correctly, as potential decreases from 1.5 to 0.05 V, the width of the carbon film increases from 67 to 83 nm. On the contrary, the boundary between electrode and electrolyte clearly changes with potential, indicating the formation of SEI. That is, as potential decreases from 1.0 V, SLD increases from 2.4 to 3.2 (x 10-4) nm-2, while the thickness increases from 18 to 36 nm at potential = 0.05 V during the initial lithiation reaction. This clearly demonstrates the growth of SEI during the lithiation reaction. Consequently, with NR measurements in the most intense neutron source, we have successfully observed the formation and growth of SEI at the boundary of the carbon electrode and liquid electrolyte during electrochemical charge and discharge reactions. Such measurements will provide an insight how to improve the performance of LIBs.

Malonatophosphate as an SEI- and CEI-forming additive that outperforms malonatoborate for thermally robust lithium-ion batteries

Lithium-ion batteries (LIBs) are electrochemical devices for energy storage used in portable electronics due to their high energy density, lightweight and flexible design. However, improvements in safety, cost and energy and power density to meet the requirements of automotive industry and large scale storage technology for the wide application of LIBs on these fields.[1, 2] The battery performance is affected by surface layers formed on the electrodes. In particular, the solid electrolyte interphase (SEI) is a protecting surface film formed on the negative electrode in organic-based electrolytes. It consists of inorganic and organic species resulting from electrolyte decomposition.[3, 4] This electron insulating layer allows the transport of lithium ions and it has an impact on the irreversible charge loss, rate capability, cyclability and safety.[3] Therefore, it is essential to understand the processes that occur at the electrode/electrolyte interfaces and the nature of the surface film to improve the efficiency and develop longer-life LIBs. ZnFe2O4 (ZFO) is a non-toxic and cheap material of great interest as anode for LIBs with a high specific theoretical capacity ca. 1000 mAhg-1 due to a conversion-alloying reaction that involves the intake of 9 Li+.[5] An environmental friendly method to encapsulate ZFO nanoparticles within a carbon matrix has been described to avoid the aggregation of particles and loss of electronic conductivity that leads to capacity fading.[5] This work presents in situ Raman measurements of carbon-coated ZnFe2O4(ZFO-C) material during the first discharge/charge cycle.[6] The Raman spectrum of ZFO-C electrode at the open-circuit potential (OCP) only shows the D and G bands characteristic of carbon materials. These peaks weaken during the discharge step suggesting that the lithiation also occurs in the carbon coating. The signal of the D and G bands is recovered at the end of the charge step. The absence of peaks related to ZFO material indicates that the carbon coating remains mechanically intact after the first discharge/charge cycle. New Raman bands are observed within a potential region that coincides with SEI layer formation. These bands have been assigned to poly(ethylene)oxide species and organic lithium alkyl carbonates from electrolyte side reactions. The detection of SEI compounds by conventional Raman microscopy may be the result of “temporary surface enhancement Raman effect” from Zn nanoparticles formed during the conversion reaction of ZnFe2O4 in a similar potential region as SEI formation. The observation of these polymeric species formed on the carbon coating is comparable to shell isolated nanoparticle Raman spectroscopy (SHINERS) reported by Tian and co-workers.[7]

Given concerns about the low earth abundance of lithium (Li) in Li-ion batteries, there is growing interest in developing a beyond-Li materials basis for rechargeable batteries. Divalent batteries based on calcium (Ca) are a compelling alternative due to the ~2000-fold higher concentration of Ca in the earth’s crust, along with attractive theoretical metrics (2073 mAh/cm3, 1337 mAh/g, -2.87 V vs. SHE) if Ca is used as a metallic anode. When most common battery electrolytes come into contact with Ca, however, a passivating solid electrolyte interphase (SEI) forms that prevents Ca2+ transport,[1] and only a handful of electrolytes have been discovered that allow for reversible Ca plating/stripping to any degree. Ca(BH4)2 in tetrahydrofuran (THF) is one of the more widely-tested electrolytes and a current benchmark given its highest-to-date cycling Coulombic efficiency (CE) of ~95%.[2] Yet, there is limited understanding of the reactions forming the SEI and the resulting degree of SEI stability, which impedes further understanding into this electrolyte’s function. To begin to address these knowledge gaps, this study employs gas chromatography (GC) analysis to track gas evolution markers of SEI formation in Ca(BH4)2/THF across a range of cell conditions and timescales.Both H2 and linear hydrocarbon (RH) gases are detected as the major evolved gas species, with the former predominantly evolving from reaction between Ca(BH4)2 and residual water, and RH products evolving from reaction between Ca and THF. RH evolution is found to be dynamic for cells at rest, with distinct timescales attributed to initial and extended SEI formation and spanning several days. When cells are polarized during Ca plating, RH evolution arrests after a certain plated capacity is reached, signaling the formation of a protective yet functional SEI that continues to be permissive to Ca plating to higher capacities. Yet, this SEI is metastable, as further chemical changes are observed when polarization is relaxed. Given the significant role of water in contributing to H2 evolution, we further systematically investigate the impact of water on SEI formation dynamics and composition. Increased water content is observed to mainly shorten SEI formation timescales, but its impact diminishes over extended cycling, and the SEI composition ultimately remains largely independent of initial water content. This work probes the highly-dynamic reactions between Ca, Ca(BH4)2/THF, and residual water, improving understanding into both the fundamentals of this electrolyte system and the unique methodologies required for its study. While H2 evolution presents severe challenges to the practical implementation of any borohydride-based electrolyte, addition of small amounts of Ca(BH4)2 to other Ca electrolyte systems, if compatible, may offer longer term benefits to the chemical stability of a battery, given the salt’s ability to scavenge trace water and accelerate early SEI formation to passivate the anode at a shorter timescale.[1] Aurbach, D., Skaletsky, R. & Gofer, Y. The Electrochemical Behavior of Calcium Electrodes in a Few Organic Electrolytes. Journal of The Electrochemical Society 138, 3536-3545 (1991).[2] Wang, D. et al. Plating and stripping calcium in an organic electrolyte. Nature Materials 17, 16 (2017).

Silicon is one of the promising anode materials for next-generation all-solid-state batteries (ASSBs). With a high theoretical capacity of 3590 mAh∙g−1, it is an alloy-type anode active material (AAM) that is both non-toxic and widely available in nature.1 However, its practical application is hindered by severe volume changes taking place during cycling and the formation of an unstable solid-electrolyte interphase (SEI). These issues lead to mechanical degradation, loss of contact, and poor long-term cycling stability, thus novel approaches are needed. Silicon is often used combined with argyrodite solid electrolytes which have good ionic partial conductivity (σion ≈ 10−3 S cm−1) and their softness facilitates the adaptation to volume changes taking place during cycling.2 Silicon nitrides (SiN x ) are promising AAMs that could overcome these limitations. By forming silicon clusters in a matrix phase consisting of silicon, lithium, and nitrogen, SiN x offers enhanced chemical stability, potentially mitigating the volume expansion and SEI instability.3 However, the electrochemical investigation of SiN x in ASSBs remains in its early stages, with the matrix formation in the first cycle impacting the initial Coulomb efficiency (ICE).This work investigates the electrochemical performances of SiN x in ASSBs and the parameters affecting capacity decay during cycling. The electrochemical test performed (e.g., long-term cycling and c-rate tests) revealed the enhanced performance of SiN x -based anodes. We investigate the role of SEI and its formation in contact with an argyrodite solid electrolyte. Further analytical methods (e.g., FIB-SEM and EDX) are performed to examine the impact of the nitrogen incorporation. References 1 Huo, H.; Janek, J. Silicon as Emerging Anode in Solid-State Batteries. ACS Energy Lett. 2022, 7 (11), 4005–4016. DOI:10.1021/acsenergylett.2c01950. 2 Zheng, F.; Kotobuki, M.; Song, S.; Lai, M. O.; Lu, L. Review on Solid Electrolytes for All-Solid-State Lithium-Ion Batteries. Journal of Power Sources 2018, 389, 198–213. DOI:10.1016/j.jpowsour.2018.04.022. 3 Kilian, S. O.; Wankmiller, B.; Sybrecht, A. M.; Twellmann, J.; Hansen, M. R.; Wiggers, H. Active Buffer Matrix in Nanoparticle-Based Silicon-Rich Silicon Nitride Anodes Enables High Stability and Fast Charging of Lithium-Ion Batteries. Advanced Materials Interfaces 2022, 9 (26), 2201389. DOI:10.1002/admi.202201389.

Nowadays, due to rapid development in technology, regardless of automobile industry, portable devices and energy storage system, the requirement of energy density, capacity and operating voltage becomes higher and higher. Traditionally, graphite anode with low capacity is limited to develop advanced lithium ion battery(LIB) and is hard to achieve the high-tech product specification; therefore, battery industries have started to focus on silicon-carbon composite materials in substitution. However, it also faces its limitation to achieve energy density of 700 Wh L-1. Using lithium metal as the anode material seems to be the only route to achieve 1000 Wh L-1 due to its extremely high capacity (3860 mAh g-1), lightness (0.59 g cm-3), and low reduction potential (-3.04 V). Consequently, more and more battery experts and researchers have devoted themselves to lithium metal battery (LMB) research. Nevertheless, lithium as active metal easily reacts with electrolyte producing poor solid electrolyte interphase (SEI) with high internal resistance leading to low coulombic efficiency and short cycle life. During charge and discharge process, lithium plating and stripping leads to non-even deposition. As a further matter, under extreme environment, such as high current density and charge density, dendritic dendrite easily forms resulting in safety issue including failure of separator and short circuit. Based on the above issues, lithium metal battery could be hardly commercialized. Therefore, battery design should be aimed at lithium metal anode instead of traditional LIB anode. First of all, innovative electrolyte system which benefits the formation of highly-stable SEI should be established. Secondly, the artificial SEI on lithium anode is served as the first line of defense against dendrite due to excellent mechanical strength and elasticity. Finally, it is important to develop a structured anode for improving lithiophilic property, uniform electric field and solving volume expansion issue.