Suppress Li Dendrite Research Articles

Improving the electrochemical performance of lithium-sulfur batteries by interface modification with a bifunctional electrolyte additive

Lithium-sulfur (Li-S) batteries with sulfur cathode and lithium anode are considered as a promising candidate in the next generation of high specific energy secondary batteries. However, the scalable application of Li-S batteries is limited by the unstable electrode/electrolyte interfaces. Herein, a novel bifunctional electrolyte additive, trifluoromethane sulfonamide (TFMSA), is introduced to stabilize both electrode/electrolyte interfaces to enhance the electrochemical performance of Li-S batteries. The TFMSA molecule can not only alleviate the passivation of the sulfur cathode surface, but also suppress Li dendrites growth and prevent the lithium anode from the corrosion of polysulfides. As a result, the assembled Li-S battery with TFMSA-containing electrolyte displays excellent long-cycle performance and rate capability. Moreover, the Li||Li symmetric cell using TFMSA electrolyte can stably cycle for 1200 h at 1 mA cm−2 and 1 mAh cm−2. The Li-S pouch cell with TFMSA also exhibits outstanding performance, indicating the prospect of practical application. This work sheds light on an innovative idea for interface modification via an electrolyte additive to overcome the inherent issues of Li-S batteries.

Constructing stable lithium interfaces via coordination of fluorinated ether and liquid crystal for room-temperature solid-state lithium metal batteries

The poor compatibility of the electrodes/solid-state electrolytes (SSEs) interfaces of rechargeable room-temperature solid-state lithium metal batteries (RTSSLMBs) limit their rapid development and commercialization. Herein, fluorinated ether as a block and liquid crystal 4,4′'-Azoxyanisole as an additive are firstly used to fabricate robust SSEs for RTSSLMBs. A combination of in-situ polymerization and the construction of stable interfaces is employed to obtain excellent cycling performance in LMBs. We propose the mechanism of regulating the lithium anode interfaces by 4,4′'-Azoxyanisole with high anchoring strength in SSEs. Liquid crystal with high anchoring strength ensures the smooth electrodeposition of lithium metal, and fluorinated ether provides rich LiF for SEI, which is beneficial to inhibit the growth of lithium dendrite. The electrochemical test shows that symmetrical lithium batteries maintain steadily operation over 3500 h. Further, the novel 3D fiber-network SPEs exhibit high ionic conductivity of 0.13 mS/cm at room temperature, a wide electrochemical stability window of 4.9 V, a high lithium-ion transference number of 0.42, and better mechanical strength (Young's modulus of 6.3 GPa). As a consequence, superior cycling stability is demonstraced in Li/LiFePO4 batteries at ambient temperature. In addition, the reaction mechanism is verified by density functional theory calculations and various electrochemical characterizations. This new and universal strategy may be a new route to suppress Li dendrites, it will be helpful for the commercialization and application of RTSSLMBs.

High-performance lithium metal battery realized by regulating Li+ flux distribution on artificial-solid-electrolyte-interphase functionalized 3D carbon framework-Li anode

Lithium dendrite issue is the key problem that hampers the practical applications of lithium metal batteries. Regulating Li+ flux distribution on Li anode can effectively tune the Li dendrite growth. Here, we report a novel Li anode composited with artificial-solid electrolyte interphase (A-SEI) functionalized 3D carbon framework seamless bonding Li foil (A-3DCF@Li) that can tune Li+ flux distribution. The synergetic effect among 3D structure, A-SEI, and LiCx in A-3DCF@Li can regulate Li+ flux on Li surface, suppressing Li dendrite growth and boosting the electrochemical performance of lithium metal battery using LiNi0·83Co0.11Mn0.06O2 as cathode materials. The experimental results and theoretical calculation prove the above statement. The work developed here shed light on the development of high-performance lithium metal anode.

A Two-Parameter Space to Tune Solid Electrolytes for Lithium Dendrite Constriction.

Li dendrite penetration, and associated microcrack propagation, at high current densities is one main challenge to the stable cycling of solid-state batteries. The interfacial decomposition reaction between Li dendrite and a solid electrolyte was recently used to suppress Li dendrite penetration through a novel effect of “dynamic stability”. Here we use a two-parameter space to classify electrolytes and propose that the effect may require the electrolyte to occupy a certain region in the space, with the principle of delicately balancing the two property metrics of a sufficient decomposition energy with the Li metal and a low critical mechanical modulus. Furthermore, in our computational prediction prepared using a combination of high-throughput computation and machine learning, we show that the positions of electrolytes in such a space can be controlled by the chemical composition of the electrolyte; the compositions can also be attained by experimental synthesis using core–shell microstructures. The designed electrolytes following this principle further demonstrate stable long cycling from 10 000 to 20 000 cycles at high current densities of 8.6–30 mA/cm2 in solid-state batteries, while in contrast the control electrolyte with a nonideal position in the two-parameter space showed a capacity decay that was faster by at least an order of magnitude due to Li dendrite penetration.

Mechanically Resilient Graphene Assembly Microspheres with Interlocked N‐Doped Graphene Nanostructures Grown In Situ for Highly Stable Lithium Metal Anodes

AbstractLi metal is considered the most attractive anode material for high‐energy Li batteries. However, the uncontrollable growth of Li dendrites and severe volume changes during Li plating and stripping inhibit the practical application of Li metal anodes. Herein, a synergistic strategy is developed not only to suppress Li dendrite growth but also to withstand repeated volume changes during long‐term cycling. Specifically, mechanically resilient graphene assembly microspheres with interlocked Ni/N‐doped lithiophilic graphene nanostructures grown in situ are developed as stable 3D graphene hosts for Li‐metal anodes. Importantly, the approach provides a novel strategy to control radial distribution of lithiophilic Ni nanocatalysts in the graphene assembly. These 3D graphene hosts can repeatedly guide the uniform deposition of Li owing to the high lithiophilicity of Ni nanocatalysts and the N‐doped graphene nanostructures. Furthermore, graphene nanoshell forms in situ between the graphene layers in the inner part of the graphene assembly, creating strong contacts between rGO layers and providing the 3D graphene host with high structural integrity. Notably, the approach emphasizes mechanical resilience of the 3D graphene host, which retains its initial morphology after repeated Li plating/stripping cycles. Consequently, the 3D graphene host maintains a highly stable coulombic efficiency of 99% over 500 cycles.

Uniform Lithium Deposition Induced by Double Lithiophobic Sandwich Structure for Stable Lithium Metal Anode

AbstractThe uncontrollable dendrite growth and complex interfacial reactions are still challenging issues hindering the practical applications of lithium (Li) metal anode. A variety of materials are widely studied to regulate the surface properties of Li metal anode except for the lithiophobic materials. This study shows that a double lithiophobic sandwich structure can induce uniform Li deposition to suppress Li dendrite growth at the nucleating stage. A hexagonal boron nitride (h‐BN) particle layer on Cu foil (h‐BN@Cu) is prepared as the research target to intensely explore the fundamental role of the lithiophobic h‐BN layer on the diffusion and nucleation behavior of Li on the Cu surface. The h‐BN layer makes the h‐BN@Cu interface possess lower adsorption energy and more substantial charge transfer, leading to the “h‐BN‐Li‐Cu” sandwich deposition mode. Theoretical calculations, in situ monitoring, and experimental tests confirm the relevance between uniform Li deposition and the h‐BN@Cu interface structure. The h‐BN@Cu anode enables a significantly improved lifespan (over 550 h) compared to the Cu anode and enhanced cycling stability when assembled in whole cells with LiFePO4 (LFP) cathode. This discovery provides a new insight into h‐BN and other lithiophobic materials as a protective layer to improve the Li deposition behavior.

Advanced Ultralow‐Concentration Electrolyte for Wide‐Temperature and High‐Voltage Li‐Metal Batteries

AbstractHigh‐voltage Li‐metal batteries (LMBs) are regarded as next‐generation high‐energy‐density storage devices to apply to extensive fields such as electric vehicles, space explorations, subsea operations, and grid‐scale storages. Unfortunately, their practical applications are restricted by some defects of commercial carbonate electrolytes including flammability, low oxidation stability, narrow temperature operation window, and Li dendrites growth. Herein, a novel ultralow‐concentration electrolyte (ULCE, 0.1 m) is fabricated by dissolving lithium difluoro(oxalato)borate in N‐methyl‐N‐methoxyethyl‐pyrrolidinium bis(trifluoromethylsulfonyl)imide ([MEMP][TFSI]) ionic liquid and 1,1,2,2‐tetrafluoroethyl‐2,2,3,3‐tetrafluoropropylether. This advanced ULCE exhibits impressive merits including low cost, non‐flammability, wide operation temperature (−100 to +70 °C), and high electrochemical window (5.75 V). Meanwhile, it helps to suppress Li dendrite growth due to the combined effect of the cation shielding by MEMP+ cations and robust solid electrolyte interphase formed by the preferential decomposition of DFOB− and TFSI− anions. The LiNi0.6Co0.2Mn0.2O2 (NCM622)/Li cell with ULCE shows outstanding performance under a high voltage of 4.5 V and a wide temperature range from −60 to 70 °C. This work provides a distinctive sight to design advanced electrolyte for lower cost, safe, and wide‐temperature high‐energy‐density LMBs.

Covalent Organic Framework as an Efficient Protection Layer for a Stable Lithium‐Metal Anode

AbstractLithium (Li) metal shows great potential for achieving high‐energy‐density rechargeable batteries. However, the practical applications of Li‐metal batteries are still challenged by the formation of Li dendrites and unstable solid‐electrolyte interphase (SEI) on metallic Li. Herein, a thin covalent organic framework layer is in situ fabricated on Li (COF‐Li) to suppress Li dendrite growth and mitigate the side reaction on the Li anode. The COF has a periodic and uniform porosity, allowing for selectively sieving Li ions and guiding a uniform Li deposition. As a result, the COF‐Li exhibits a non‐dendrite morphology during repeated Li plating/stripping and demonstrates a remarkable cycle life over 13 200 h with an extremely low overpotential of only 16 mV at a high current density of 10 mA cm−2 and a high areal capacity of 10 mAh cm−2.

Covalent Organic Framework as an Efficient Protection Layer for a Stable Lithium-Metal Anode.

Lithium (Li) metal shows great potential for achieving high-energy-density rechargeable batteries. However, the practical applications of Li-metal batteries are still challenged by the formation of Li dendrites and unstable solid-electrolyte interphase (SEI) on metallic Li. Herein, a thin covalent organic framework layer is in situ fabricated on Li (COF-Li) to suppress Li dendrite growth and mitigate the side reaction on the Li anode. The COF has a periodic and uniform porosity, allowing for selectively sieving Li ions and guiding a uniform Li deposition. As a result, the COF-Li exhibits a non-dendrite morphology during repeated Li plating/stripping and demonstrates a remarkable cycle life over 13 200 h with an extremely low overpotential of only 16 mV at a high current density of 10 mA cm-2 and a high areal capacity of 10 mAh cm-2 .

Heterostructure ZnSe-CoSe2 embedded with yolk-shell conductive dodecahedral as Two-in-one hosts for cathode and anode protection of Lithium–Sulfur full batteries

Simultaneously realizing the cathode and anode protection is critical for developing practical lithium sulfur (Li-S) batteries. Currently, many efforts have been devoted to solving problems related to either shuttle effect on sulfur cathode or dendrite growth on lithium anode. However, dual side protection is rarely reported. Herein, we rationally designed and synthesized yolk-shell nitrogen doped carbon frameworks embedded with heterostructures ZnSe-CoSe2 (ZnSe-CoSe2@NC), working as “two-in-one” hosts for both the sulfur cathode and lithium anode protection. As an anode host, the in situ formed Li2Se phase contributes to the Li+ transfer. Co and Zn guides a homogenous growth of Li within the 3D framework, thus effectively suppressing Li dendrite growth. Meanwhile, the heterostructure ZnSe-CoSe2 endows the cathode host with superior electronic conductivity, strong polysulfide chemisorption and efficient catalytic activity for polysulfide redox when compared with single metal selenides. Combined with these advantages, this Li-S full cell exhibits ultralong cycle life over 1000 cycles at 2 C. Even with a high sulfur loading (6.08 mg cm−2) and lean electrolyte (4.1 µL mg−1), the full cell achieves a high areal capacity of 4.16 mA h cm−2 after 100 cycles at 0.2 C. This work not only provides a new approach for the structure design of Li-S full battery, but also improves the utilization of active electrode materials.

A cleverly designed asymmetrical composite electrolyte via in-situ polymerization for high-performance, dendrite-free solid state lithium metal battery

In-situ polymerized gel polymer electrolytes have been considered as the most promising alternative to liquid electrolyte owing to their high ionic conductivity, improved safety, simple and environmentally friendly manufacturing process, and good interfacial compatibility with electrodes. However, their poor mechanical properties are not able to prevent the Li dendrites growth in batteries. Inspired by the composite electrolytes, an asymmetrical gel electrolyte (A-PGCE) consisting of cellulose membrane-supported gel electrolyte and LLZTO-rich layer on one side is fabricated by a facile one-step in-situ polymerization method. The well-designed A-PGCE not only exhibits excellent properties such as superior flexibility, good thermal stability and wide electrochemical window (5.13 V), but also possesses high ionic conductivity (1.25 × 10-3 S cm−1) and Li+ transference number (0.57). Furthermore, the introduced LLZTO-rich layer demonstrates excellent ability in guiding uniform Li+ deposition and suppressing Li dendrite growth, which enables the symmetrical Li-Li cells with such electrolyte to run stably for over 1750 h at 0.1 mA cm−2 and 450 h at 0.2 mA cm−2. Benefiting from these advantages of A-PGCE, the assembled Li metal battery with high-voltage LiCoO2 (LCO) cathode shows high initial capacity of 157.6 mAh g−1 in the cutoff voltage of 4.3 V, and the capacity retention is 90.7% after 200 cycles at 0.2C, indicating a superior cyclic stability. The cleverly designed asymmetrical A-PGCE shows great potential in boosting the development of lithium metal batteries with high energy density and safety.

Studies on the inhibition of lithium dendrite formation in sulfide solid electrolytes doped with LiX (X = Br, I)

A promising method to increase the energy density of all-solid-state batteries (ASSBs) featuring lithium ions as carriers is to employ Li metal as the anode. However, this has been accompanied by safety problems like flammable accidents associated with lithium dendrites originating from reactions with the solid electrolyte, leading to reduced battery performance. To overcome this issue toward the commercialization of ASSBs, various approaches have been proposed by many researchers. Among the suggested solutions, the use of lithium-halide-doped Li3PS4, to suppress lithium dendrite formation, has attracted attention. LiI-doped Li3PS4 has shown the highest lithium dendrite growth suppression among lithium-halide-doped systems, but the reason for this is unclear. Thus, we attempted to clarify the cause of this suppression by comparing LiBr-doped Li3PS4 with LiI-doped Li3PS4. Investigation using various methods such as electrochemical evaluation, X-ray absorption spectroscopy, X-ray computed tomography, and pair distribution function analysis revealed that two factors affect the suppression of Li dendrite growth: the suppression of the current density distribution by improving the ionic conductivity and the stable interfacial layer. This is the main reason LiI-doped Li3PS4 shows excellent Li dendrite suppression.

Highly uniform lithiated nafion thin coating on separator as an artificial SEI layer of lithium metal anode toward suppressed dendrite growth

A lithiated Nafion (Li+-Nafion) thin coating on lithium (Li) metal anode has been evidenced to be capable of inhibiting Li dendrite growth. However, shortcomings of Li metal such as poor stability in air and high reactivity with water bring inconvenience in the coating preparation. To address this issue, a highly uniform Li+-Nafion thin layer coated commercial polypropylene (PP) separator is fabricated via an ultrasonic spray method. In cells, the Li+-Nafion thin coating faces and contacts with Li metal anode to act as an artificial solid electrolyte interphase (SEI) layer of the anode. The addition of N,N-Dimethylformamide in sprayed aqueous Li+-Nafion solution is crucial for the highly uniform deposition of Li+-Nafion thin coating with a thickness of 0.8 μm due to the improved wettability of the sprayed Li+-Niafion solution with the PP separator. The uniform Li+-Nafion thin coating significantly increases the Li+ transference number (tLi+) of the PP separator from 0.34 to 0.76. The improved tLi+ and the high uniformity of the Li+-Nafion thin coating enable the coated PP separator to suppress Li dendrite growth, and consequently to promote the cycle performance of lithium-sulfur cells. This work proposes an implantation approach for artificial SEI layers employed in Li metal batteries.

Highly Fluorinated Al-Centered Lithium Salt Boosting the Interfacial Compatibility of Li-Metal Batteries

Formulating electrolytes is very powerful in protecting lithium (Li) anode from severe Li dendrites growth and pulverization. Herein, by a simple one-step and one-pot method, we innovatively synthesize a highly fluorinated (8-CF3) aluminum (Al)-centered lithium salt of lithium perfluoropinacolatoaluminate (LiFPA). The as-formulated LiFPA-based electrolytes enable practical Li/LiCoO2 (areal capacity 1.98 mAh cm–2) and Li/LiNi0.6Co0.2Mn0.2O2 (areal capacity 3.5 mAh cm–2) Li metal batteries (LMBs) with good cycling stability. On the one hand, LiFPA salt can reduce electrolyte surface tension, improve electrolyte wettability, and ultimately suppress Li dendrites growth. On the other hand, the LiFPA salt will facilitate the formation of a protective passivating interphase layer on both electrodes. Our work states the importance of synthesizing of lithium salts with good interfacial compatibility for high performance LMBs.

An Ion‐Dipole‐Reinforced Polyether Electrolyte with Ion‐Solvation Cages Enabling High–Voltage‐Tolerant and Ion‐Conductive Solid‐State Lithium Metal Batteries (Adv. Funct. Mater. 5/2022)

High-Performance Polymer Electrolytes In article number 2107764, Xinran Wang, Ying Bai, Chuan Wu, and co-workers develop a hyperbranched polyether electrolyte for solid-state Li metal batteries. The existing ion-solvation structures allow for fast Li+ migration (1.26 × 10−4 S cm−1, 25 °C), a wide stable voltage window (up to 4.6 V), and Li dendrite suppression, overcoming the insufficiencies encountered by polymer electrolytes. The ion-dipole-reinforced solid electrolyte yields sustainable Li stripping/platting and interfacial stability, thus enabling high cycle stability and capacity retention in NCM811|Li solid-state cells.

Regulating lithium deposition behavior by electrokinetic effects in a high-zeta-potential h-BN/zinc-lithium alloy for high-performance lithium metal anodes

A high-zeta-potential h-BN-doped LiZn alloy promotes strong electrokinetic effects to significantly improve Li-ion transport kinetics, which can effectively suppress Li dendrite growth and enable stable Li metal anodes under harsh conditions.

Mechanism of Lithium Dendrites Formation and Suppression Strategies in Li Metal Batteries

This paper describes and summarizes the modifying progress established on Li metal anode in recent years. With the increasing demand for high-capacity batteries, Li-ion batteries, one of the most commercialized batteries, can no longer meet the demand. Thus, the high-energy-density lithium metal battery using lithium metal as anode is widely researched due to the lowest electrochemical potential (-3.04 V) of lithium and ultimate theoretical capacity (3860 mAh/g). However, the Li dendrites formation becomes the main obstacle for the commercialization as it will trigger thermal runaway and short circuit. In this paper, the growth process of Li dendrites was discussed, and various modifying solutions based on electrolytes, Li alloy and current collectors to suppress Li dendrites were summarized.

Engineering and characterization of interphases for lithium metal anodes.

Lithium metal is a very promising anode material for achieving high energy density for next generation battery systems due to its low redox potential and high theoretical specific capacity of 3860 mA h g−1. However, dendrite formation and low coulombic efficiency during cycling greatly hindered its practical applications. The formation of a stable solid electrolyte interphase (SEI) on the lithium metal anode (LMA) holds the key to resolving these problems. A lot of techniques such as electrolyte modification, electrolyte additive introduction, and artificial SEI layer coating have been developed to form a stable SEI with capability to facilitate fast Li+ transportation and to suppress Li dendrite formation and undesired side reactions. It is well accepted that the chemical and physical properties of the SEI on the LMA are closely related to the kinetics of Li+ transport across the electrolyte–electrode interface and Li deposition behavior, which in turn affect the overall performance of the cell. Unfortunately, the chemical and structural complexity of the SEI makes it the least understood component of the battery cell. Recently various advanced in situ and ex situ characterization techniques have been developed to study the SEI and the results are quite interesting. Therefore, an overview about these new findings and development of SEI engineering and characterization is quite valuable to the battery research community. In this perspective, different strategies of SEI engineering are summarized, including electrolyte modification, electrolyte additive application, and artificial SEI construction. In addition, various advanced characterization techniques for investigating the SEI formation mechanism are discussed, including in situ visualization of the lithium deposition behavior, the quantification of inactive lithium, and using X-rays, neutrons and electrons as probing beams for both imaging and spectroscopy techniques with typical examples.

Fe3N@N-doped graphene as a lithiophilic interlayer for highly stable lithium metal batteries

Lithium (Li) metal anode is of great importance for high-energy rechargeable batteries owing to its ultrahigh theoretical capacity. However, the Li dendrite growth during the repetitive charge/discharge process will impale the separator resulting in short-circuiting and serious safety issues. To effectively suppress Li dendrite growth, for the first time we present a novel lithiophilic interlayer on commercial PP separator, which is constructed by Fe3N nanoparticles embedded and wrapped in N-doped graphene nanosheets (Fe3N@NG). The Fe3N@NG functionalized separator displays excellent electrolyte wettability, high Li ionic conductivity and ion transference number, which function synergistically to suppress Li dendrite growth. Meanwhile, the DFT calculation demonstrates that there exists a stronger interaction between Li atoms and Fe3N@NG, which can provide the deposition sites, resulting in uniform and compact Li plating. Above ameliorating merits accompany an ultra-long-life of 2300 h at 5 mA cm−2 for the Li//Li symmetric cells with Fe3N@NG functionalized separators. Moreover, the Li//LFePO4 full cell delivers superior long-term cyclic stability and ultralow capacity decay rate of 0.08%/cycle even at 2C. This work provides an innovative strategy to rationally design and new insights towards functional lithiophilic interlayer to efficiently suppress Li dendrite growth for Li metal batteries.

Tuning Interface Lithiophobicity for Lithium Metal Solid-State Batteries

Solid-state lithium batteries (SSLBs) using garnet electrolytes potentially have a higher energy density and are safer than liquid organic electrolyte Li-ion batteries. However, SSLBs face challenges of Li dendrite and high interface resistance. In this work, we overcome both challenges by doping strontium (Sr) into lithium anodes. Different from all previous metal/metal oxide coating on garnet or Li alloy anodes that form lithiophilic interlayer, Li–Sr/SrO-doped Li2O are enriched on the interface forming a lithiophilic/lithiophobic bifunctional layer. The interlayer reduces the interfacial resistance and also suppresses lithium dendrite. The stability of the lithiophobic SrO-doped Li2O against Li prevents reducing the garnet and suppresses Li dendrite, which distinguishes it from all reported alloy electron-conducting interlayers. The optimized Li–Sr|garnet|Li–Sr symmetric cell achieves a critical current density of 1.3 mA/cm2 and can be cycled for 1,000 cycles under 0.5 mA/cm2 at room temperature. The bifunctional lithiophilic/lithiophobic interlayer provides a new strategy for high-performance garnet solid-state lithium batteries.