Solid-state Li Metal Batteries Research Articles

Quasi-solid-state electrolytes - strategy towards stabilising Li|inorganic solid electrolyte interfaces in solid-state Li metal batteries

Solid-state batteries (SSBs) based on inorganic solid electrolytes (ISEs) are considered promising candidates for enhancing the energy density and the safety of next-generation rechargeable lithium batteries. However, their practical application is frequently hampered by the high resistance arising at the Li metal anode/ISE interface. Herein, a review of the conventional solid-state electrolytes (SSEs) the recent research on quasi-solid-state battery (QSSB) approaches to overcome the issues of the state-of-the-art SSBs is reported. The feasibility of ionic liquid (IL)-based interlayers to improve ISE/Li metal wetting and enhance charge transfer at solid electrolyte interfaces with both positive and lithium metal electrodes is presented together with a novel generation of IL-containing quasi-solid-state-electrolytes (QSSEs), offering favourable features. The opportunities and challenges of QSSE for the development of high energy and high safety quasi-solid-state lithium metal batteries (QSSLMBs) are also discussed.

A self-healing polymerized-ionic-liquid-based polymer electrolyte enables a long lifespan and dendrite-free solid-state Li metal batteries at room temperature.

The implementation of high-safety Li metal batteries (LMBs) needs more stable and safer electrolytes. The solid-state electrolytes (SSEs) with their advantageous properties stand out for this purpose. However, low Li/electrolyte interfacial instability and uncontrolled Li dendrites growth trigger unceasing breakage of the solid electrolyte interphase (SEI), leading to fast capacity degradation. In response to these shortcomings, a new type of polymer electrolyte with self-healing capacity is introduced by grafting ionic liquid chain units into the backbones of polymers, which inherits the chemical inertness against the Li anode, allowing high Li+ transport, wide electrochemical window, and self-healing traits. Benefiting from the strong external H-bonding interactions, the obtained polymer electrolyte can spontaneously reconstruct dendrite-induced defects and fatigue crack growth at the Li/electrolyte interface, and, in turn, help tailor Li deposition. Owing to the resilient Li/electrolyte interface and dendrite-free Li plating, the equipped Li|LFP batteries display a high initial specific capacity of 134.7 mA h g-1, rendering a capacity retention of 91.2% after 206 cycles at room temperature. The new polymer electrolyte will undoubtedly bring inspiration for developing practical LMBs with highly improved safety and interfacial stability.

The role of grain boundaries in solid-state Li-metal batteries

Despite the potential advantages promised by solid-state batteries, the success of solid-state electrolytes has not yet been fully realised. This is due in part to the lower ionic conductivity of solid electrolytes. In many solid superionic conductors, grain boundaries are found to be ionically resistive and hence contribute to this lower ionic conductivity. Additionally, in spite of the hope that solid electrolytes would inhibit lithium filaments, in most scenarios their growth is still observed, and in some polycrystalline systems this is suggested to occur along grain boundaries. It is apparent that grain boundaries affect the performance of solid-state electrolytes, however a deeper understanding is lacking. In this perspective, the current theories relating to grain boundaries in solid-state electrolytes are explored, as well as addressing some of the challenges which arise when trying to investigate their role. Glasses are presented as a possible solution to reduce the effect of grain boundaries in electrolytes. Future research directions are suggested which will aid in both understanding the role of grain boundaries, and diminishing their contribution in cases where they are detrimental.

Tension-Induced Cavitation in Li-Metal Stripping.

Designing stable Li metal and supporting solid structures (SSS) is of fundamental importance in rechargeable Li-metal batteries. Yet, the stripping kinetics of Li metal and its mechanical effect on the supporting solids (including solid electrolyte interface) remain mysterious to date. Here, through nanoscale in situ observations of a solid-state Li-metal battery in an electron microscope, two distinct cavitation-mediated Li stripping modes controlled by the ratio of the SSS thickness (t) to the Li deposit's radius (r) are discovered. A quantitative criterion is established to understand the damage tolerance of SSS on the Li-metal stripping pathways. For mechanically unstable SSS (t/r< 0.21), the stripping proceeds via tension-induced multisite cavitation accompanied by severe SSS buckling and necking, ultimately leading to Li "trapping" or "dead Li" formation; for mechanically stable SSS (t/r> 0.21), the Li metal undergoes nearly planar stripping from the root via single cavitation, showing negligible buckling. This work proves the existence of an electronically conductive precursor film coated on the interior of solid electrolytes that however can be mechanically damaged, and it is of potential importance to the design of delicate Li-metal supporting structures to high-performance solid-state Li-metal batteries.

Electrode structure enabling dendrite inhibition for high cycle stability quasi-solid-state lithium metal batteries

Lithium (Li) metal batteries (LMBs) are widely regarded as the ultimate choice for the next generation of high-energy–density batteries. However, the uncontrollable growth of Li dendrites formed by inhomogeneous deposition seriously hinders its commercialization. Although many studies have achieved significant results in inhibiting the formation of Li dendrites, it is still impossible to eradicate them completely. Therefore, regulating the deposition behavior, such as the growth direction of unevenly deposited Li, is preferable to unilaterally suppressing them in some cases. Here we report a structured anode that can confine the deposited Li within holes and tune it to become vertical-up/horizontal-centripetal mixed growth mode by optimizing the electric field/Li+ concentration gradient. The Li+ adsorbed by the poly(amic acid) (PAA) insulating layer coated on the anode surface can form the Li+ concentration gradient pointing to the center of the hole. Combined with the special electric field formed by the hole structure, it is favorable for the Li+ to move into the vertically arrayed holes and simultaneously deposit on the bottom and walls. Furthermore, both in-situ and ex-situ observations confirm that the growth mode is changed and the Li deposition morphology is denser, which can greatly delay capacity fading and prolong cycle life in both liquid and quasi-solid-state LMBs. All the results show that the novel anode provides a new perspective for deep research into solid-state LMBs.

Preparation and performances of gallium-doped LLZO electrolyte with high ionic conductivity by rapid ultra-high-temperature sintering

Garnet-type Li7La3Zr2O12 (LLZO) is a promising solid-state electrolyte (SSE) for next generation lithium batteries due to its high Li+ conductivity and stability against lithium metal, especially the Li7−3xGaxLa3Zr2O12 (Ga-LLZO) is most valuable because of its high ionic conductivity (> 1 ×10−3 S cm−1). However, it is difficult to prepare high-quality Ga-LLZO by the traditional air ambient sintering. Herein, we develop a simple and efficient rapid ultra-high-temperature sintering (RUHTS) method to prepare high-conductivity Ga-LLZO ceramic SSE. It has been found that the as-prepared Ga-LLZO ceramic SSE with the composition of Li6.25Ga0.25La3Zr2O12 exhibits high relative density of 99%, good ionic conductivity of 1.48 × 10−3 S cm−1 and large critical current density of 0.5 mA cm−2 after sintering at 1200 °C for 2 min. In addition, the Ga-LLZO SSE shows good electrochemical stability and interfacial compatibility against Li metal. The assembled Li-Li symmetric cell represents a small interfacial impedance of 37 Ω cm2. In the same time, the Li/Ga-LLZO/LE+LMNCO full battery has a total impedance of 205 Ω cm2, and can deliver a first discharge capacity of 235.1 mAh g−1 at 0.5 C, and the capacity retention rate is 88.3% after 100 cycles. This indicates that the as-prepared Ga-LLZO has good application prospect in the Li-metal solid-state batteries (LMSSBs). Moreover, this method does not require the use of mother powder during preparation process, which will effectively reduce the waste of raw materials, save manufacture costs and be beneficial to quantity production of Ga-LLZO ceramic electrolyte.

Selective and uniform Li-ion boosting polymer electrolytes for dendrite-less quasi-solid-state batteries

Solid-state Li-metal batteries (LMBs) are attracting extensive attention owing to their exceptionally high energy density. Solid electrolytes play a vital role in the practical application of LMBs due to their nonflammable nature and interfacial stability with Li metal, but they ordinarily have a low ionic conductivity and dimensional stability. Here, a selective Li+ conductive solid-state electrolyte (SLCSE) that comprises a highly conductive yet mechanically robust, anion-immobilized (CMA) polymer matrix synthesized by soft-rigid coupled ether-abundant epoxy monomers and branched polyamine, is reported. Rationally incorporated rigid benzene-ring constituents in the CMA matrix not only enhance mechanical strength but also boost Li+ transportation by suppressing crystallinity. The semi-interpenetrating network of the CMA matrix and polyvinylidene fluoride-co-hexafluoropropylene displays synergistic Li+ acceleration behavior by promoting the dissociation and diffusion of Li+ while immobilizing anions, which is elucidated via molecular dynamics simulations. The SLCSE exhibits a high ionic conductivity (3.4 mS cm−1) with a high Li+ transference number (0.77), and SLCSE-based LMBs (Li/SLCSE/LiCoO2 cell) show a high discharge capacity of 146 mAh g−1 (0.2 C) and 126 mAh g−1 (3 C). Furthermore, they show exceptional long cycle stability (90% capacity retention after 500 cycles at 0.5 C), representing remarkable Li dendrite suppression capability.

Enabling an electron/ion conductive composite lithium anode for solid-state lithium-metal batteries with garnet electrolyte

• A composite lithium anode with continuous electron/ion dual-conductive networks is engineered on the surface of garnet-type ceramic electrolyte. • The solid-state Li-symmetric cells exhibit a low interfacial resistance of <2.0 Ω cm 2 , a high critical current density of 1.1 mA cm −2 and a long lifespan of >3500 h. • The LiFePO4-based solid-state batteries can deliver high specific capacity of 161.7 mAh g −1 at 25 °C, with good cycle and rate performance. The use of Li anode is critical for the energy density of solid-state Li-metal batteries (SSLMBs) to surpass that of lithium-ion batteries. However, the practical applications are hampered by the large interfacial resistance and poor physical contact at the solid-state interface, as well as dendrite issues and volume changes of Li anode. Here, a composite lithium anode with continuous electron/ion conductive networks is fabricated, which shows a significant improvement in wettability towards garnet-type Li6.4La3Zr1.4Ta0.6O12 electrolytes. The intimate interface and its high charge-transfer kinetics of composite Li anode endows the symmetric cell a small overpotential (45 mV) at 0.3 cm −2 , ultra-low interfacial resistance (∼ 2.0 Ω cm 2 ), high critical current density (1.1 mA cm −2 ), and outstanding cycling performance (>3000 hours at 0.1 mA cm −2 ) at 25 °C. The SSLMB paired with LiFePO 4 delivers a high discharge specific capacity of 161.7 mAh g −1 at 0.1 C, good cycle performance of 100 cycles with capacity retention of 80%. Moreover, the NMC811-based SSLMB can also realize a high capacity of 219.5 mAh g −1 , superior rate capability and cyclic stability. This work lays the foundation to develop composite Li anodes for practical applications of SSLMBs with high performance.

Influence of the operating temperature on the ageing and interfaces of double layer polymer electrolyte solid state Li metal batteries

Influence of the operating temperature on the ageing and interfaces of double layer polymer electrolyte solid state Li metal batteries

Mechano-electrochemical coupling in flexible all-solid-state lithium metal batteries

Bending and stretching are critical mechanical behaviors affecting the electrochemical performance of flexible batteries in wearable electronic devices. Herein, a mechano-electrochemical model is developed for solid-state Li metal batteries under bending deformation. It is found that bending alters ion transport and electric potential in solid polymer electrolytes, and its influence relies on the bending direction. By means of the curvature and coupling coefficient, a phase map is constructed for the critical current density that leads to ion depletion at the Li metal-electrolyte interface. In addition, a positive curvature helps to decrease the overpotential for electrochemical reactions on the Li metal electrode. Though the direct influence of bending on electrochemical kinetics is limited, the bending deformation could substantially increase the stress and cause potential mechanical failure of electrodes and electrode-electrolyte interfaces, thereby degrading electrochemical performance.

A bifunctional composite artificial solid electrolyte interphase for high stable solid-state lithium batteries

Poor interfacial compatibility between lithium (Li) metal anode and solid electrolyte is the main obstacle for solid-state Li metal batteries. To address which prefabricating an artificial solid electrolyte interphase (SEI) film on the surface of lithium anode is an effective strategy. Here, a bifunctional composite artificial SEI film with high ionic conductivity and interface compatibility is provided via in-situ forming poly-1,3-dioxolane (PDOL)/reduced graphene oxide (rGO) composite film on the surface of Li metal. The flexible high-ionic conductive PDOL improves the physical contact between the solid electrolyte and Li metal anode, and the rigid rGO effectively promotes the uniform plating of lithium ion (Li+) and suppresses the growth of Li dendrites. This rigid/flexible composite artificial SEI film not only boosts the interfacial transport of Li+, but also improves the interfacial compatibility between Li metal anode and solid electrolyte. Matching with PDOL solid electrolyte, the composite SEI film helps the Li symmetric cells to cycle stably for more than 350 h at a high current density of 0.3 mA/cm2 and an areal capacity of 0.3 mAh/cm2. Compared with the discharge specific capacity of pure Li metal anode, the discharge specific capacity of the assembled NCM622/PDOL & rGO-Li cell is increased by 17.5% at 2 C. This bifunctional composite SEI film provides a new idea for the surface modification of lithium metal anode.

The void formation behaviors in working solid-state Li metal batteries.

The fundamental understanding of the elusive evolution behavior of the buried solid-solid interfaces is the major barrier to exploring solid-state electrochemical devices. Here, we uncover the interfacial void evolution principles in solid-state batteries, build a solid-state void nucleation and growth model, and make an analogy with the bubble formation in liquid phases. In solid-state lithium metal batteries, the lithium stripping-induced interfacial void formation determines the morphological instabilities that result in battery failure. The void-induced contact loss processes are quantified in a phase diagram under wide current densities ranging from 1.0 to 10.0 milliamperes per square centimeter by rational electrochemistry calculations. The in situ-visualized morphological evolutions reveal the microscopic features of void defects under different stripping circumstances. The electrochemical-morphological relationship helps to elucidate the current density- and areal capacity-dependent void nucleation and growth mechanisms, which affords fresh insights on understanding and designing solid-solid interfaces for advanced solid-state batteries.

Enable high reversibility of Fe/Cu based fluoride conversion batteries via interfacial gas release and detergency of garnet electrolytes

Garnet-type Ta-doped Li7La3Zr2O12 (LLZTO) electrolyte suffers from unstable chemical passivation under air exposure, responsible for the poor interfacial wettability and conductivity with Li metal. Instead of conventional methods to remove surface contaminants by mechanical polishing, acid etching and high temperature reduction, herein we propose a simple strategy of interfacial gas release and detergency to smartly convert Li2CO3 passivation layer into ion-conductive Li3PO4 domains at mild temperature (∼200 ℃). The in-situ formation of PH3 vapor and its phosphorization enables a dramatic decrease of Li/garnet interfacial resistance down to 2 Ω cm2 at room temperature (RT). The improved interfacial wettability and conductivity endow the symmetric cells with ultra-stable galvanostatic cycling over 1500 h and high critical current density of 2.6 mA/cm2. The high coulombic efficiency of Li plating enables a high reversibility of solid-state NCM811/Li cells even under a low N/P ratio (∼4) and high cut-off voltage of 4.5 V at RT. The prototype of fluoride-garnet solid-state batteries are successfully driven as rechargeable system (rather than widely known primary battery) with high conversion capacity (400 ∼ 500 mAh/g) and high-rate performance (251.2 mAh/g at 3 C). This interface infiltration-detergency approach provides a practical solution to the achievement of high-energy solid-state Li metal batteries.

Concerted ionic-electronic conductivity enables high-rate capability Li-metal solid-state batteries

Enabling the fast charge and discharge of Li-metal solid-state batteries paves the way towards their deployment in electro-mobility applications, which require high-energy and power with safety guaranteed. Solid-state batteries using polyethylene oxide as the polymer matrix are appealing candidates although currently limited to relatively slow rate capability arising from high solid-solid interfacial resistance and sluggish lithium-ion mobility at the solid electrolyte. In this work, the engineering design and optimization of composite electrodes with multi-walled carbon nanotubes lead to high performance Li metal solid-state cells, showing a high-capacity retention at rates up to 4C. The electrode formulations including the elongated architectures exhibit a concerted ionic-electronic diffusion in the catholyte polymer enabling fast Li-ion transport, enhancing the electronic percolation and increasing the interfacial reaction kinetics and exchange current density. The solid-state battery with LiFePO4 electrode shows an unprecedented capacity retention of 92% during 800 cycles at 2C. The promising performance at high-rates of this approach is also extended to electrodes with a high-voltage active material.

Analyzing void formation and rewetting of thin in situ-formed Li anodes on LLZO

•The stripping behavior of thin Li was correlated with current density and thickness •Two regimes of thin Li stripping behavior were identified •The effect of Li void formation during unstable stripping is not fully recovered •De-wetted Li/solid electrolyte interfaces can be reestablished by a thermal treatment The transition from laboratory-scale thick Li-metal anodes (>500 μm) to thin (∼10–30 μm) Li anodes is necessary for the successful implementation of Li-metal solid-state batteries (LMSSBs). However, the mechanical deformation of Li along an interface depends on its thickness, making it essential to understand the interface mechanics between thin Li layers and solid electrolytes. We investigate the stripping behavior of thin Li electrodes that are formed using in situ plated (anode-free) Li on Li7La3Zr2O12 garnet-type solid electrolytes. We demonstrate that the accessible discharge capacity increases as current density decreases and the Li anode thickness increases. It is shown that two different mechanisms restrict the stripping of thin Li electrodes, depending on the current density. We demonstrate that de-wetted Li/LLZO interfaces during stripping can be reestablished using a thermal treatment. This approach could be integrated into future charging protocols, and the findings provide insight into LMSSB design, implementation, and operation. The transition from laboratory-scale thick Li-metal anodes (>500 μm) to thin (∼10–30 μm) Li anodes is necessary for the successful implementation of Li-metal solid-state batteries (LMSSBs). However, the mechanical deformation of Li along an interface depends on its thickness, making it essential to understand the interface mechanics between thin Li layers and solid electrolytes. We investigate the stripping behavior of thin Li electrodes that are formed using in situ plated (anode-free) Li on Li7La3Zr2O12 garnet-type solid electrolytes. We demonstrate that the accessible discharge capacity increases as current density decreases and the Li anode thickness increases. It is shown that two different mechanisms restrict the stripping of thin Li electrodes, depending on the current density. We demonstrate that de-wetted Li/LLZO interfaces during stripping can be reestablished using a thermal treatment. This approach could be integrated into future charging protocols, and the findings provide insight into LMSSB design, implementation, and operation.

Electro-Chemo-Mechanical Failure of Solid Electrolytes Induced by Growth of Internal Lithium Filaments.

Growth of lithium (Li) filaments within solid electrolytes, leading to mechanical degradation of the electrolyte and even short circuit of the cell under high current density, is a great barrier to commercialization of solid-state Li-metal batteries. Understanding of this electro-chemo-mechanical phenomenon is hindered by the challenge of tracking local fields inside the solid electrolyte. Here, a multiphysics simulation aiming to investigate evolution of the mechanical failure of the solid electrolyte induced by the internal growth of Li is reported. Visualization of local stress, damage, and crack propagation within the solid electrolyte enables examination of factors dominating the degradation process, including the geometry, number, and size of Li filaments and voids in theelectrolyte. Relative damage induced by locally high stress is found to preferentially occur in the region of the electrolyte/Li interface having great fluctuations. A high number density of Li filaments or voids triggers integration of damage and crack networks by enhanced propagation. This model is built on coupling of mechanical and electrochemical processes for internal plating of Li, revealing evolution of multiphysical fields that can barely be captured by the state-of-the-art experimental techniques. Understanding mechanical degradation of solid electrolytes with the presence of Li filaments paves the way to design advanced solid electrolytes for future solid-state Li-metal batteries.

Distinct functional Janus interfaces for dendrite-free Li1.3Al0.3Ti1.7(PO4)3-based lithium metal batteries

The NASICON-type Li1.3Al0.3Ti1.7(PO4)3 (LATP) ceramic electrolyte shows promise for high-energy-density solid-state Li metal batteries (SSLMBs), but its incompatibility and poor interfacial contact with cathode/anode electrode still is a bottleneck problem of the commercial development. Herein, the compatible and effective solid-state electrolyte is devised by coating LATP pellet with distinct functional polymers dependent on respective interface necessities. Specifically, the poly (vinylene carbonate) (PVCA) + tetraethylene glycol dimethyl ether (TEGDME) protective layer is introduced into LATP/LiFePO4 interface via simple in-situ polymerization method, and the polyvinylidene fluoride hexafluoropropylene (PVDF-HFP) + TEGDME protective layer is coated to the LATP surface facing Li anode. We demonstrate that the PVCA layer on the cathode side is closely attached to LiFePO4 along with reduced impedance at LATP/LiFePO4 interface, the PVDF-HFP layer on the anode side protects LATP from being reduced, and TEGDME improves the electrochemical stability window (ESW) and ionic conductivity of the protective layers. Such Janus LATP electrolyte endows SSLMBs with extremely small interfacial impedance (188 Ω), excellent cycling stability (∼ 90% after 300 cycles) and dendritic-free Li anode (3000 h stable cycling) at 60 °C. This study implies that this double-protected interface modification strategy is brilliant in constructing high-performance and dendritic-free SSLMBs for future application.

Cryo‐EM Studies of Atomic‐Scale Structures of Interfaces in Garnet‐Type Electrolyte Based Solid‐State Batteries

AbstractHigh interfacial impedance is a major obstacle in the application of solid‐state Li metal batteries (SSLMBs). Understanding the atomic‐scale structure of the interfaces in SSLMBs is thus critical to their practical implementations. However, due to the beam sensitivity of battery materials, such information is not accessible by conventional electron microscopy (EM). Herein, by using cryogenic‐EM (cryo‐EM), the atomic‐scale structures of interfaces in garnet electrolyte based SSLMBs are revealed. A LiF‐rich interlayer exhibiting intimate contacts with both Li and LLZTO is shown, thus rendering uniform Li+ transport across the interface in turn inhibiting Li dendrite growth. Consequently, the Li symmetric cell based on the LiF‐rich interlayer exhibits a high critical current density of 3.2 mA cm−2 and a long lifespan over 1800 cycles at 1 mA cm−2. Moreover, a full cell with a LiNi0.88Co0.1Al0.02O2 cathode at a high mass loading ≈12 mg cm−2 reached over 400 cycles at 1.2 mA cm−2, which represents a major progress in the performance of the garnet‐type SSLMBs. This study provides atomic‐scale understanding of interfaces in SSLMBs and an effective strategy to design dendrite‐free SSLMBs for practical applications.

Electrochemical-Mechanical Coupling at Li Metal / Solid Electrolyte Interfaces and the Safety of Li Metal Solid-State Batteries

Using Li and Na metal with a solid electrolyte in high-energy and safe batteries for consumer applications is of great interest, but our understanding of the behavior of this interface, as well as the expected safety of high-energy cells built with Li or Na metal and a solid electrolyte, requires improvement. In this talk I will describe (1) our work in both modeling and measuring electrochemical-mechanical coupling at a Li or Na metal / solid electrolyte interface, as well as (2) modeling and experimental work on Li metal solid state battery safety.The electrochemical-mechanical coupling topic (1) will focus on the influence on the current distribution of expected mechanical loadings at a metal/solid electrolyte influence, taking into account the expected plastic deformation of the metal electrode. We find that the mechanical boundary conditions, and inclusion of plastic deformation of a metal electrode such as Na or Li, strongly influences the resulting impact on the interfacial current distribution. Our approach and recent experimental work for parameterizing and validating electrochemical-mechanical coupling will also be presented. Here, we focus on interfacial characterization and methods to study thin films of solid state battery materials under well-defined mechanical loads.The solid-state battery topic (2) will focus on a quantitative understanding of temperature rise in Li metal solid state batteries, based on the thermochemistry of the reactions that occur upon heating due to an external source (e.g., an oven test) or an internal short. Previously reported differential scanning calorimetry experiments as well as those we collect provide heat flows vs. temperature for the reactions among cell components (e.g., Li metal, cathode powder, solid electrolyte, cathode binder and conductive additive, current collectors). This data serves as a basis for modeling temperature rise in large-format cells. We find that oxygen release from metal oxide cathodes that reacts with molten Li in the cell can drive significant temperature rise, and discuss methods to improve the safety of Li metal solid state batteries.

(Electrodeposition Division Early Career Investigator Award) Understanding and Controlling Electrodeposition of Li in Solid Electrolytes

The successful integration of Li metal anode with solid electrolytes seems to be a must for a high-energy-density solid-state battery. However, Li dendrites tend to form in solid electrolytes during Li plating. The formation of dendrites has been observed in solid electrolytes with various crystal structures from glass, glass-ceramic, poly-crystalline to single-crystalline materials, but the mechanism of such an unexpected dendrite growth remains elusive. In this presentation, I will introduce our understandings of lithium dendrite formation in solid electrolytes based on operando neutron depth profiling characterizations. The results highlight the important role of electronic conduction in solid electrolytes in the formation of isolated Li dendrites in solid electrolytes. I will then present our recent results in understanding the intrinsic value, voltage dependence, and charge carrier of electronic transport in typical lithium solid electrolytes. Lastly, I will introduce corresponding strategies to suppress dendrite formation in solid-state Li metal batteries. Reference s : [1] F. Han, A. S. Westover, J. Yue, X. Fan, F. Wang, M. Chi, D. N. Leonard, N. J. Dudney, H. Wang, C. Wang, Nature Energy, 4 (2019) 187.[2] F. Han, J. Yue, X. Zhu, C. Wang, Advanced Energy Materials, 8 (2018) 1703644.[3] F. Han, J. Yue, C. Chen, N. Zhao, X. Fan, Z. Ma, T. Gao, F. Wang, X. Guo, C. Wang, Joule, 2 (2018) 497.[4] X. Fan, X. Ji, F. Han, J. Yue, J. Chen, L. Chen, T. Deng, J. Jiang, C. Wang, Science Advances, 4 (2018) eaau9245.[5] R. Xu, F. Han, X. Fan, J. Tu, C. Wang, Nano Energy, 53 (2018) 958.[6] Y. Huang, B. Shao, F. Han, Current Opinions in Electrochemistry, 33 (2022) 100933.[7] Y. Huang, B. Shao, F. Han, Journal of Materials Chemistry A, 10 (2022) 12350.[8] F. Han, Y. Zhu, X. He, Y. Mo, C. Wang, Advanced Energy Materials, 6 (2016) 1501590.[9] F. Han, T. Gao, Y. Zhu, K. J. Gaskell, C. Wang, Advanced Materials, 27 (2015) 3473.