Sulfurized Polyacrylonitrile Cathode Research Articles

Practical SPAN||Li cells enabled by insitu polymerized electrolyte

Sulfurized polyacrylonitrile (SPAN) is a promising cathode material for long-life lithium-sulfur batteries (LSBs) due to its enhanced electronic conductivity as well as the eliminated shuttle effect. However, the uncontrollable lithium dendrite issue as well as slow kinetics of thick electrodes still hinders its practical application. Herein, an in situ polymerized electrolyte (PGE) based on vinyl carbonate and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) is designed and prepared to enhance the plating/stripping stability of the metal lithium while ensuring the cathode/electrolyte interfacial ion transportation. The optimized electrolyte, PGE-D, shows a satisfying ionic conductivity of 0.46 mS/cm at 25 °C; in the meantime, the polymer matrix hinders the diffusion of TFSI− anion and results in a high Li+ transference number (tLi+) of 0.73. Benefiting from the high affinity of the flowable PGE precursor to the thick SPAN cathode as well as enhanced lithium compatibility, the Li||SPAN battery with high areal loading of 14.1 mg/cm2 exhibits a high reversible specific capacity of 556.5 mAh/g and retains 76.3% of its capacity after 90 cycles.

Lightweight Electrolyte Design for Li/Sulfurized Polyacrylonitrile (SPAN) Batteries.

Sulfurized polyacrylonitrile (SPAN) recently emergesas a promising cathode for high-energy lithium (Li) metal batteries owing to its high capacity, extended cycle life, and liberty from costly transition metals. As the high capacities of both Li metal and SPAN lead to relatively small electrode weights, the weight and specific energy density of Li/SPAN batteries are particularly sensitive to electrolyte weight, highlighting the importance of minimizing electrolyte density. Besides, the large volume changes of Li metal anode and SPAN cathode require inorganic-rich interphases that can guarantee intactness and protectivity throughout long cycles. This work addresses these crucial aspects with an electrolyte design where lightweight dibutyl ether (DBE) is used as adiluent for concentrated lithium bis(fluorosulfonyl)imide(LiFSI)-triethyl phosphate (TEP) solution. The designed electrolyte (d = 1.04g mL-1) is 40%-50% lighter than conventional localized high-concentration electrolytes (LHCEs), leading to 12%-20% extra energy density at the cell level. Besides, the use of DBE introduces substantial solvent-diluent affinity, resulting in a unique solvation structure with strengthened capability to form favorable anion-derived inorganic-rich interphases, minimize electrolyte consumption, and improve cell cyclability. The electrolyte also exhibits low volatility and offers good protection to both Li metal anode and SPAN cathode under thermal abuse.

Flexible CNT-Interpenetrating Hierarchically Porous Sulfurized Polyacrylonitrile (CIHP-SPAN) Electrodes for High-Rate Lithium-Sulfur (Li-S) Batteries.

Sulfurized polyacrylonitrile (SPAN) is a promising cathode material for lithium-sulfur batteries owing to its reversible solid-solid conversion for high-energy-density batteries. However, the sluggish reaction kinetics of SPAN cathodes significantly limit their output capacity, especially at high cycling rates. Herein, a CNT-interpenetrating hierarchically porous SPAN electrode is developed by a simple phase-separation method. Flexible self-supporting SPAN cathodes with fast electron/ion pathways are synthesized without additional binders, and exceptional high-rate cycling performances are obtained even with substantial sulfur loading. For batteries assembled with this special cathode, an impressive initial discharge capacity of 1090 mAh g-1 and a retained capacity of 800 mAh g-1 are obtained after 1000 cycles at 1 C with a sulfur loading of 1.5 mg cm-2. Furthermore, by incorporating V2O5 anchored carbon fiber as an interlayer with adsorption and catalysis function, a high initial capacity of 614.8 mAh g-1 and a notable sustained capacity of 500 mAh g-1 after 500 cycles at 5 C are achieved, with an ultralow decay rate of 0.037% per cycle with a sulfur loading of 1.5 mg cm-2. The feasible construction of flexible SPAN electrodes with enhanced cycling performance enlists the current processing as a promising strategy for novel high-rate lithium-sulfur batteries and other emerging battery electrodes.

Sodium–Sulfur Cells with a Sulfurized Polyacrylonitrile Cathode and a Localized High Concentration Electrolyte with Toluene as a Nonfluorinated Diluent

AbstractRoom‐temperature sodium–sulfur (Na–S) batteries are recognized as promising candidates for next‐generation scalable energy storage systems due to their high energy density and cost‐effectiveness. However, several challenges persist, including the shuttle effect of polysulfide and the compatibility of sodium metal with electrolytes. Herein, the study presents a novel type of localized high‐concentration electrolyte (LHCE), utilizing a cost‐effective, low‐density nonfluorinated diluent, toluene, in contrast to the conventional fluorinated diluents. Based on density functional theory calculations and sodium stripping/plating behavior, toluene demonstrates better reduction stability than other aromatic solvents with different substitutions. Also, compared to the 1,2,2‐tetrafluoroethyl‐2,2,3,3‐tetrafluoropropyl‐ether (TTE) diluent, toluene exhibits enhanced compatibility with sodium metal. Furthermore, it modifies the solvation structure by favoring anion‐dominated species, which contributes to the formation of a robust inorganic‐rich solid‐electrolyte interphase (SEI) with better Na‐ion transport. Consequently, Na–S cells featuring sulfurized polyacrylonitrile (SPAN) cathode with the developed LHCE exhibit good cycling stability with high capacity. The work presents a promising strategy for developing low‐cost practical Na–S batteries.

New insights into the reaction mechanism of sulfurized polyacrylonitrile cathode material for Li–S batteries

Sulfurized polyacrylonitrile (SPAN) is a prospective cathode candidate for Li–S batteries due to capable of solving polysulfides dissolution and shuttle effect and presenting stable electrochemical performance. Despite the extensive research conducted on the synthetic conditions and pathways for SPAN modification, details of the molecular structure of SPAN and electrochemical reaction mechanism of SPAN electrode remain controversial. Herein, the formation of conjugate aromatic radical and new C–S bond during discharge process is proposed for the first time. During charge process, the S atom prioritize to combine with C radical on the aromatic ring, resulting in avoiding the generation of polysulfides over long cycles, which potentially account for the remarkable cycling stability observed in the SPAN cathode. This study offers novel insights into the underlying reaction mechanisms, thereby providing valuable guidance for further development of sulfurized cathode materials applied in advanced Li–S battery.

A ZIF-8-enhanced PVDF/PEO blending polymer gel membrane for quasi-solid-state Na-S batteries with long cycling lifespan

Ambient-temperature sodium-sulfur (Na-S) battery with high energy density and low cost has been considered as the promising energy density system. However, its commercial application is limited by the rapid capacity decay of the sulfur electrode and the instability of sodium dendrites with the safety issues. Herein, a ZIF-8 enhanced PVDF/PEO blending polymer gel membrane (PPZ) is reported for stable and safe quasi-solid-state Na-S battery with sulfurized polyacrylonitrile (SPAN) cathode and Na metal anode. The optimized gel polymer membrane with the dense framework exhibited the rapid Na+ migration, superior mechanical property with the tensile strength of 16.5 MPa and the elongation-at-break of 171 %, which is conductive to regulate the Na+ ion flux with the uniform Na plating and prevent the dendritic growth. The assembled symmetric Na/PPZ-GPE/Na cell delivered the stable cycling for 250 h with almost constant voltage hysteresis of 150 mV. Benefited from the superior interfacial stability between PPZ-GPE and Na as well as PPZ-GPE and SPAN, the SPAN/PPZ-GPE/Na cell exhibited the high capacity of 1585.4 mA h g−1 with the capacity retain of 97 % of third cycle after 465 cycles. This work offers exemplary electrolyte design that concurrently and effectively tackles the problems in Na-S battery and presents an excellent quasi-solid sodium-sulfur battery with the high capacity and long cycling.

A locally solvent-tethered polymer electrolyte for long-life lithium metal batteries

Solid polymer electrolytes exhibit enhanced Li+ conductivity when plasticized with highly dielectric solvents such as N,N-dimethylformamide (DMF). However, the application of DMF-containing electrolytes in solid-state batteries is hindered by poor cycle life caused by continuous DMF degradation at the anode surface and the resulting unstable solid-electrolyte interphase. Here we report a composite polymer electrolyte with a rationally designed Hofmann-DMF coordination complex to address this issue. DMF is engineered on Hofmann frameworks as tethered ligands to construct a locally DMF-rich interface which promotes Li+ conduction through a ligand-assisted transport mechanism. A high ionic conductivity of 6.5 × 10−4 S cm−1 is achieved at room temperature. We demonstrate that the composite electrolyte effectively reduces the free shuttling and subsequent decomposition of DMF. The locally solvent-tethered electrolyte cycles stably for over 6000 h at 0.1 mA cm−2 in Li | |Li symmetric cell. When paired with sulfurized polyacrylonitrile cathodes, the full cell exhibits a prolonged cycle life of 1000 cycles at 1 C. This work will facilitate the development of practical polymer-based electrolytes with high ionic conductivity and long cycle life.

SPAN secondary particles enabled high energy density Lithium-Sulfur battery

High-areal-capacity electrodes and lean electrolyte are practical approaches for batteries to enhance their energy density, while it’s challenge for the lithium-sulfur batteries using nano-sized sulfurized polyacrylonitrile (SPAN) cathodes due to the sluggish charge transportation. Here, a spray-drying (SD) technique for mass production of micron-sized SPAN secondary particles (PC-SPAN) with composite coating is proposed. The composite involves polydopamine (PDA), polyacrylic acid (PAA) and polyvinyl alcohol (PVA) that physiochemically crosslinking. The rich catecholamine, hydroxyl and carboxyl groups not only construct strong and flexible adhesion among the SPAN primary particles to keep the electrode integrity, but also render built-in ion passage within the secondary particles to allow the electrode working under lean electrolyte condition. Consequently, PC-SPAN electrode with a high areal loading of 8.4 mg cm−2 delivers a higher specific capacity of 547.4 mAh g−1 at 0.3C when that of SPAN is less than 400.0 mAh g−1. In the meantime, prototype Li-SPAN battery with high energy density of 530.2 Wh kg−1 is achieved using PC-SPAN electrode with an areal capacity of 19.1 mAh cm−2 and low electrolyte/SPAN ratio of 0.93 μL mg−1, which demonstrates the feasibility of this strategy toward applicable high energy LSBs.

Stable sodium metal anode enabled by interfacial room‐temperature liquid metal engineering for high‐performance sodium–sulfur batteries with carbonate‐based electrolyte

AbstractSodium (Na) metal is a competitive anode for next‐generation energy storage applications in view of its low cost and high‐energy density. However, the uncontrolled side reactions, unstable solid electrolyte interphase (SEI) and dendrite growth at the electrode/electrolyte interfaces impede the practical application of Na metal as anode. Herein, a heterogeneous Na‐based alloys interfacial protective layer is constructed in situ on the surface of Na foil by self‐diffusion of liquid metal at room temperature, named “HAIP Na.” The interfacial Na‐based alloys layer with good electrolyte wettability and strong sodiophilicity, and assisted in the construction of NaF‐rich SEI. By means of direct visualization and theoretical simulation, we verify that the interfacial Na‐based alloys layer enabling uniform Na+ flux deposition and suppressing the dendrite growth. As a result, in the carbonate‐based electrolyte, the HAIP Na||HAIP Na symmetric cells exhibit a remarkably enhanced cycling life for more than 650 h with a capacity of 1 mAh cm−2 at a current density of 1 mA cm−2. When the HAIP Na anode is paired with sulfurized polyacrylonitrile (SPAN) cathode, the SPAN||HAIP Na full cells demonstrate excellent rate performance and cycling stability.

Tailoring Solvation Solvent in Localized High-Concentration Electrolytes for Lithium||Sulfurized Polyacrylonitrile.

Sulfurized polyacrylonitrile (SPAN) is a promising cathode material for lithium-sulfur (Li-S) batteries due to its significantly reduced polysulfide (PS) dissolution compared to that of elemental S cathodes. Although conventional carbonate-based electrolytes are stable with SPAN electrodes, they are unstable with Li metal anodes. Recently, localized high-concentration electrolytes (LHCEs) have been developed to improve the stability of Li anodes. Here, we report a new strategy to further improve the performance of Li||SPAN batteries by replacing the conventional solvating solvent 1,2-dimethoxyethane (DME) in LHCEs with a new solvating solvent, 1,2-diethoxyethane (DEE). The new optimal DEE-LHCE exhibits less reactivity against Li2S2, alleviates PS dissolution, forms a better cathode-electrolyte interphase layer on the SPAN cathode, and enhances SPAN structural reversibility even at elevated temperatures (45 °C). Compared to DME-LHCE, DEE-LHCE with the same salt and diluent leads to better performance in Li||SPAN batteries (with 82.9% capacity retention after 300 cycles at 45 °C), preservation of the SPAN cathode structure, and suppression of volume change of the Li metal anode. A similar strategy on tailoring the solvating solvents in LHCEs can also be used in other rechargeable batteries to improve their electrochemical performances.

Boosting Cathode Activity and Anode Stability of Lithium-Sulfur Batteries with Vigorous Iodic Species Triggered by Nitrate.

Lithium-sulfur (Li-S) battery with a sulfurized polyacrylonitrile cathode is a promising alternative to Li-ion systems. However, the sluggish charge transfer of cathode and accumulation of inactive Li on anode remain persistent challenges. An advanced electrolyte additive with function towards both cathode and anode holds great promise to address these issues. Herein, we present a new strategy to boost sulfur activity and rejuvenate dead Li simultaneously. In the polar electrolyte containing I2-LiNO3 additives, I3 -/IO3 - are triggered significantly by the reaction between NO3 - and I- ions. The I3 -/IO3 - are reactive to insulated Li2S product of cathode and inactive Li on anode, thus accelerating the conversion reaction of sulfur and recovering Li sources back to battery cycling. The in situ/ex situ spectroscopic and morphologic monitoring reveal the crucial role of iodine in promoting Li2S dissociation and inhibiting dendritic Li growth. With the modified electrolyte, the symmetric Li||Li cells deliver a lifespan of 4000 h with an overpotential less than 12 mV at 0.5 mA cm-2. For Li-S cells, 100 % capacity retention up to thousands of cycles and enhanced rate capability are available. This work demonstrates a feasible strategy on electrolyte engineering for practical applications of Li-S batteries.

Boosting Cathode Activity and Anode Stability of Lithium–Sulfur Batteries with Vigorous Iodic Species Triggered by Nitrate

AbstractLithium–sulfur (Li−S) battery with a sulfurized polyacrylonitrile cathode is a promising alternative to Li‐ion systems. However, the sluggish charge transfer of cathode and accumulation of inactive Li on anode remain persistent challenges. An advanced electrolyte additive with function towards both cathode and anode holds great promise to address these issues. Herein, we present a new strategy to boost sulfur activity and rejuvenate dead Li simultaneously. In the polar electrolyte containing I2−LiNO3 additives, I3−/IO3− are triggered significantly by the reaction between NO3− and I− ions. The I3−/IO3− are reactive to insulated Li2S product of cathode and inactive Li on anode, thus accelerating the conversion reaction of sulfur and recovering Li sources back to battery cycling. The in situ/ex situ spectroscopic and morphologic monitoring reveal the crucial role of iodine in promoting Li2S dissociation and inhibiting dendritic Li growth. With the modified electrolyte, the symmetric Li||Li cells deliver a lifespan of 4000 h with an overpotential less than 12 mV at 0.5 mA cm−2. For Li−S cells, 100 % capacity retention up to thousands of cycles and enhanced rate capability are available. This work demonstrates a feasible strategy on electrolyte engineering for practical applications of Li−S batteries.

Electrolyte optimization for sodium-sulfur batteries

Due to high theoretical capacity, low cost, and high energy density, sodium-sulfur (Na-S) batteries are attractive for next-generation grid-level storage systems. However, the polysulfide shuttle leads to a rapid capacity loss in sodium-sulfur batteries with elemental sulfur as the cathode material. Most previous studies have focused on nanoengineering methods for creating stable Na anodes and S cathodes. A proven strategy to mitigate the shuttle effect is to covalently bond elemental sulfur to a polymeric backbone and use it as the active ingredient instead of elemental sulfur. In this regard, we synthesized sulfurized polyacrylonitrile (SPAN) cathodes. In addition to the electrodes, electrolyte selection is crucial for sodium sulfur batteries with long cycle life, high energy densities, and rate capabilities. Thus, we explored various electrolyte compositions; specifically organic solvents such as propylene carbonate (PC), dioxolane (DOL), dimethoxyethane, and diglyme (DIG) were mixed in different proportions to create electrolyte solvents with both ethers and carbonates to promote the formation of bilateral solid electrolyte interphase (SEI). This bilateral SEI strategy has been employed to prevent polysulfide shuttle and dendrite growth in lithium-sulfur batteries. Sodium bis(trifluoromethanesulfonyl)imide (NaTFSI) was chosen as the electrolyte salt. The prepared coin cells were tested for rate capability and capacity retention, and the results have been analyzed. High initial discharge capacity of ∼740 mAh g−1 with ∼66% capacity retention over 100 cycles was observed for 0.8M NaTFSI in PC50DOL50 (v/v). The cell with 0.8M NaTFSI in PC50DIG50 has exhibited strong capacity retention of 74.60% with excellent Coulombic efficiency of 99%. Molecular dynamics (MD) simulations were carried out to further understand these results.

High-Performance Sulfurized Polyacrylonitrile Cathode by Using MXene as a Conductive and Catalytic Binder for Room-Temperature Na/S Batteries.

Sulfurized polyacrylonitrile (PAN@S) is a promising cathode material for room-temperature Na/S batteries but suffers from low conductivity and insufficient electrochemical activity, resulting in unsatisfactory actual capacity and rate performance. Herein, Ti3C2Tx MXene nanosheets are used as a conductive and catalytic binder to establish the PAN@S electrode, wherein MXene constructs a highly conductive framework for fast charge transport and provides high catalytic effect to improve the active material utilization and accelerate the redox kinetics significantly. Therefore, the PAN@S electrode bonded by MXene shows an electronic conductivity of 5.05 S cm-1, 4 orders of magnitude higher than the conventional electrodes bonded by the insulative polymer binders, and much decreased activation energy barrier and resistance. Consequently, the PAN@S electrode displays superior performance in terms of high capacity (697.3 mAh g-1 at 200 mA g-1), unparalleled rate capability (189.0 mAh g-1 at 20 A g-1), and excellent high-rate cycling performance (a capacity decay rate of ∼0.04% per cycle during 1000 cycles at 5 A g-1). This work provides a high-performance electrode for room-temperature Na/S batteries and shows the promising potential of conductive and catalytic MXene binders in boosting the performance of active materials.

Interfacial Electrochemical Lithiation and Dissolution Mechanisms at a Sulfurized Polyacrylonitrile Cathode Surface.

Advances in sulfurized-polyacrylonitrile (SPAN)-based cathode materials promise safer and more efficient lithium-sulfur (Li-S) battery performance. To elucidate electrolyte-cathode interfacial electrochemistry and polysulfide (PS) dissolution, we emulate discharge SPAN reactions via ab initio molecular dynamics (AIMD) simulations. Plausible structures and their lithiation profiles are cross-validated via Raman/IR spectroscopy and density functional theory (DFT). Lithium bis(fluorosulfonyl)imide (LiFSI) plays versatile roles in the Li-SPAN cell electrochemistry, primarily as the major source in forming the cathode-electrolyte interphase (CEI), further verified via X-ray photoelectron spectroscopy and AIMD. Besides being a charge carrier and CEI composer, LiFSI mediates the PS generation processes in SPAN electrochemical lithiation. Analysis of AIMD trajectories during progressive lithiation reveals that, compared to carbonates, ether solvents enable stronger solvation and chemical stabilization for both salt and SPAN structures. Differentiated CEI formation and electrochemical lithiation decomposition pathways and products are profoundly associated with the intrinsic nature of lithium bonding with oxygen and sulfur.

A Novel Sodium–Potassium Anode Supported by Fluorinated Aluminum Foam

Sodium–potassium (NaK) liquid alloy is a promising candidate for use as an anode material in sodium batteries because of its fluidity, which effectively suppresses the growth of sodium or potassium dendrites. However, the poor wettability of NaK alloy on conventional metal substrates is unfavorable for cell fabrication due to its strong surface tension. In this paper, low-density and low-cost fluorinated aluminum foam is used as a substrate support material for NaK liquid alloy. By combining low-surface-tension NaKC with fluorinated aluminum foam, we obtain a uniformly distributed and structurally stable electrode material. The composite electrode has a cycling stability of more than 3000 h in a symmetrical cell. Furthermore, when coupled with a sulfurized polyacrylonitrile cathode in carbonate electrolyte, it maintains excellent stability even after 800 cycles, with 72% of capacity retention.

Realizing sulfurized polyacrylonitrile cathode in ether-based electrolyte

The sulfurized polyacrylonitrile (SPAN) cathode presents an excellent potential for achieving high energy density in lithium-sulfur batteries (LSBs). However, this cathode can only operate efficiently in the presence of a lithium metal anode (LMA)-unfriendly carbonic ester-based electrolyte. The challenge lies in enabling the SPAN cathode to function effectively with an LMA-friendly ether-based electrolyte. In this study, we have successfully designed a custom ether-based electrolyte by dissolving LiNO3 in diethylene glycol dimethyl ether, supplemented with a few Li bisfluorosulfonimide additives. As anticipated, this specially formulated electrolyte exhibits remarkable compatibility with both LMA and the SPAN cathode. The resulting Li|SPAN cell exhibits impressive performance, achieving a high capacity of 1430 and 1066 mAh g−1 at 0.5 and 6 C, respectively, and maintaining long-term stability with 80 % capacity retention after 1000 cycles at 2 C. Our findings demonstrate that this designed ether-based electrolyte plays a pivotal role in facilitating the formation of a stable and highly conductive interfacial layer between both the anode and cathode, leading to enhanced LSB performance.

Strategy for High-Energy Li-S Battery Coupling with a Li Metal Anode and a Sulfurized Polyacrylonitrile Cathode.

Among lithium-sulfur (Li-S) battery materials, sulfurized polyacrylonitrile (SPAN) has attracted substantial attention as a cathode material owing to its potential to bypass the problematic polysulfide formation and shuttling effect. Carbonate-based electrolytes have been eschewed compared with ether-based electrolytes because of their poor compatibility with Li metal anodes. In this work, we design and study an electrolyte comprising 0.8 M of lithium bis(trifluoromethanesulfonyl)imide, 0.2 M of lithium difluoro(oxalate)borate, and 0.05 M of lithium hexafluorophosphate in ethyl methyl carbonate/fluoroethylene carbonate = 3:1 v/v solution in the Li-S battery coupled with a Li metal anode and SPAN cathode. The well-designed carbonate-based electrolyte effectively stabilizes both electrodes, delivering high Coulombic efficiencies with stable cyclability. Studies using operando optical microscopy and atomic force microscopy demonstrate that dense, uniform Li deposition is promoted to suppress dendrite growth even at a high current density. Operando Raman spectroscopy reveals a reversible Li+ storage behavior in the SPAN structure through the cleavage of disulfide bonds and their redimerization during lithiation and delithiation. As a result, the proposed Li-S battery delivers an overall capacity retention of 73.5% over 1000 cycles, with high Coulombic efficiencies over 99.9%.

Reversible Solid-Solid Conversion of Sulfurized Polyacrylonitrile Cathodes in Lithium-Sulfur Batteries by Weakly Solvating Ether Electrolytes.

Despite carbonate electrolytes exhibiting good stability to sulfurized polyacrylonitrile (SPAN), their chemical incompatibility with lithium (Li) metal anode leads to poor electrochemical performance of Li||SPAN full cells. While the SPAN employs conventional ether electrolytes that suffer from the shuttle effect, leading to rapid capacity fading. Here, we tailor a dilute electrolyte based on a low solvating power ether solvent that is both compatible with SPAN and Li metal. Unlike conventional ether electrolytes, the weakly solvating ether electrolyte enables SPAN to undergo reversibly "solid-solid" conversion. It features an anion-rich solvation structure that allows for the formation of a robust cathode electrolyte interphase on the SPAN, effectively blocking the dissolution of polysulfides into the bulk electrolyte and avoiding the shuttle effect. What's more, the unique electrolyte chemistry endowed Li ions with fast electroplating kinetics and induced high reversibility Li deposition/stripping process from 25 °C to -40 °C. Based on tailored electrolyte, Li||SPAN full cells matched with high loading SPAN cathodes (≈3.6 mAh cm-2 ) and 50 μm Li foil can operate stably over a wide range of temperatures. Additionally, Li||SPAN pouch cell under lean electrolyte and 5 % excess Li conditions can continuously operate stably for over a month.

Composite Lithium Metal Structure to Mitigate Pulverization and Enable Long‐Life Batteries

AbstractIn lithium metal batteries, non‐uniform stripping of lithium results in pit formation, which promotes subsequent non‐uniform, dendritic deposition. This viscous cycle leads to pulverization of lithium which promotes cell shorting or capacity degradation, symptoms further exaggerated by high electrode areal loading and lean electrolytes. To address this challenge, a composite lithium metal anode is engineered that contains uniformly distributed, nanometer‐sized carbon particles. This composite lithium is shown to strip more uniformly since the growth of non‐uniform pits is intercepted by the carbon particles. This mechanism is corroborated by a continuum electrochemical model. Subsequent lithium deposition on carbon particles is also found to be more uniform than on the surface with irregular pits. Notably, the pulverization rate of composite lithium is 26 times slower than that of commercial lithium. Moreover, in a Li‐S battery with sulfurized polyacrylonitrile cathode, the use of the composite anode extends the cycle life by three times when the areal capacity is 8 mAh cm−2. The approach of using an engineered lithium composite structure to address challenges during both stripping and plating can inform future designs of lithium metal anodes for high areal capacity operations.