Tunable Interaction between Metal‐Organic Frameworks and Electroactive Components in Lithium–Sulfur Batteries: Status and Perspectives

Abstract

lithium-ion batteries (LIBs) have proven an unprecedented success in portable electronics, electric vehicles, grid storage, etc., which make a great difference in our lives. Hence, the 2019 Nobel Prize in Chemistry was awarded to John B. Goodenough, M. Stanley Whittingham, and Akira Yoshino for their revolutionary work in the field of LIBs. [1] The current LIBs technology is based on insertion-compound anode and cathode materials. As shown in Figure 1, the capacities of the insertion-oxide cathodes have reached the limit of ≈250 mAh g −1 , and that of the graphite anode is also limited to ≈370 mAh g −1 . However, the limited capacities are unable to satisfy the ever-growing need for gravimetric and volumetric energy density. It is required topic to develop next generation energy technology. Targeting the goal, researchers have their sights set on alternative electrode materials. On the anode side, based on conversion reactions while accommodating more ions and electrons are becoming promising options. [2] Approaching mature silicon/ carbon anode elevates anode capacity well. [3] And lithium metal anode are also booming. [4] On the cathode side, multi-electron conversion reaction represented by sulfur and oxygen electrode can offer capacities exceed that of conventional insertion cathodes, such as, LiCoO 2 and LiMn 2 O 4 , by an order of magnitude (>1500 mAh g −1 ). Since 2009, lithium-sulfur (Li-S) batteries have received increasing attention and are considered as one of the most promising candidates for next-generation rechargeable batteries after the development of high-performance Li-S batteries by CMK-3 as host. [5] Sulfur, as one of the most abundant elements on earth, is an electrochemically active material that can accept two electrons per atom at ≈2.1 V (vs. Li + /Li). [6] As a result, sulfur cathode materials have high theoretical capacity of 1675 mAh g −1 , and Li-S batteries have theoretical energy density of ≈2600 Wh kg −1 . [7] However, the issues including low conductivity of S and Li 2 S, shuttle effect, large volumetric expansion, and unstable lithium metal anode have to face. [8] Up to now, intensive efforts in component regulation and structure engineering electrode materials have been focused on solving these issues.Sulfur cathodes with high sulfur content (>90 wt%), [9] excellent cycling life (>3000 cycles), [10] as well as, high operating Lithium-sulfur (Li-S) batteries, with high theoretical energy density, promise to be the optimal candidate of next-generation energy-storage. Rapid development in materials has made a major step forward in Li-S batteries. However, a big gap in cycle life and efficiency for practical applications still remains. Reasonable design of materials/electrodes a is significant aspect that must be addressed. The rising metal-organic frameworks (MOFs) are a new class of crystalline porous organic-inorganic hybrid materials. Abundant inorganic nodes and designable organic linkers allow tailored pore chemistry at a molecular-scale, which enables tunable interaction w...

Copolymerization of Sulfur Chains with Vinyl Functionalized Metal−Organic Framework for Accelerating Redox Kinetics in Lithium−Sulfur Batteries

“…However, to the best of our knowledge, it remains challenging for developing workable LSBs based on MOFs hosts especially at high sulfur loadings and under lean electrolyte systems. [45] Herein, LSB with a higher sulfur loading cathode of 5.6 mg cm -2 was assembled. It can be seen in Figure 4e, the high sulfur loading LSB exhibits a greatly improved initial areal capacity of 4.25 mAh cm −2 , 150% higher than that of the traditional MOF/S cathode.…”

CoFe Alloy-Decorated Interlayer with a Synergistic Catalytic Effect Improves the Electrochemical Kinetics of Polysulfide Conversion

“…Lithium-ion batteries (LIBs) are approaching their theoretical ceiling, but they still cannot fulfill the high energy density requirement from electric vehicles . Therefore, researchers started paying attention to lithium–sulfur (Li–S) batteries with a theoretical energy density of 2600 Wh kg –1 , several times of LIBs. − Another advantage of Li–S batteries is the naturally abundant, cost-effective, and eco-friendly feature of the sulfur cathode, benefiting the commercialization of Li–S batteries. Despite these prominent merits, some problems preventing the commercialization of Li–S batteries still exist. − First, the insulating nature of the discharge product Li 2 S 2 /Li 2 S and the charge product sulfur greatly hinders electron transfer, leading to a discounted capacity and poor rate performance.…”

Lightweight Shield to Stabilize Li Metal Anodes at High Current Rates

“…Furthermore, surface modification of lithium anodes has been confirmed by researchers as an efficient method to stabilize the lithium metal anode. , Owing to a number of beneficial functions of metal–organic frameworks (MOFs), such as homogenizing Li + flux, compacting lithium deposition, and increasing Li + transport efficiency in electrolytes, an open-architecture metal–organic framework (OA-MOF) with stereoscopic lithiophilic sites was demonstrated to act as a dynamical SEI, a well-designed MOF-coated functional polypropylene, and functional glass fiber (GF) with MOFs as a separator for LMBs, respectively. , The polar groups grafted with organic ligands in the MOF generate abundant polar bonds, including O–H and M–O, improving adhesive interactions with Li + , which facilitates a well-distributed Li-ionic flow, decreases the lithium nucleation barrier, and promotes uniform deposition during Li deposition during cycling. Moreover, MOFs can regulate the transfer process of Li-ion and maximize the driving force of ion transportation, achieving smooth lithium deposition. − We also demonstrate that the MOF-based three-dimensional (3D) porous interfacial layer acts as a robust shield to physically suppress lithium dendrite growth and exploit its high-polarity structure to homogenize Li-ion concentration for Li deposition, thereby alleviating the formation of excessive SEI . However, the fabrication of a MOF layer on lithium metals to utilize its advantages is still a problem.…”