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1. In situ formation of a multicomponent inorganic-rich SEI layer provides a fast charging and high specific energy Li-metal battery

   https://doi.org/10.1039/C9TA05063A  

   Sun, Ho-Hyun ; Dolocan, Andrei ; Weeks, Jason A. ; Rodriguez, Rodrigo ; Heller, Adam ; Mullins, C. Buddie ( July 2019 , Journal of Materials Chemistry A)

   The performance of the rechargeable Li metal battery anode is limited by the poor ionic conductivity and poor mechanical properties of its solid-electrolyte interphase (SEI) layer. To overcome this, a 3 : 1 v/v ethyl methyl carbonate (EMC) : fluoroethylene carbonate (FEC) containing 0.8 M lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and 0.2 M lithium difluoro(oxalate)borate (LiDFOB) dual-salts with 0.05 M lithium hexafluorophosphate (LiPF 6 ) was tested to promote the formation of a multitude of SEI-beneficial species. The resulting SEI layer was rich in LiF, Li 2 CO 3 , oligomeric and glass borates, Li 3 N, and Li 2 S, which enhanced its role as a protective yet Li + conductive film, stabilizing the lithium metal anode and minimizing dead lithium build-up. With a stable SEI, a Li/Li[Ni 0.59 Co 0.2 Mn 0.2 Al 0.01 ]O 2 Li-metal battery (LMB) retains 75% of its 177 mA h g −1 specific discharge capacity for 500 hours at a coulombic efficiency of greater than 99.3% at the fast charge–discharge rate of 1.8 mA cm −2 .
2. In situ synthesis and in operando NMR studies of a high-performance Ni ₅ P ₄ -nanosheet anode

   https://doi.org/10.1039/C8TA05433A  

   Feng, Xuyong ; Tang, Mingxue ; O'Neill, Sean ; Hu, Yan-Yan ( November 2018 , Journal of Materials Chemistry A)

   Nickel phosphide (Ni 5 P 4 ) nanosheets are synthesized using in situ chemical vapor deposition of P on Ni foam. The thickness of the as-synthesized Ni 5 P 4 film is determined to be ∼5 nm, using atomic force microscopy (AFM). The small thickness shortens the diffusion path of Li ions and results in fast ion transport. In addition, the 2D Ni 5 P 4 nanosheets seamlessly connect to the Ni foam, which facilitates electron transfer between Ni 5 P 4 and the Ni current collector. Therefore, the binder/carbon free-nickel supported Ni 5 P 4 shows fast rate performance as an anode for lithium-ion batteries (LIBs). The specific capacity of 2D Ni 5 P 4 is obtained as 600 mA h g −1 at a cycling rate of 0.1C, approaching the theoretical capacity of 768 mA h g −1 . Even at a rate of 0.5C, the capacity remains as 450 mA h g −1 over 100 cycles. A capacity >100 mA h g −1 is retained at a very high rate of 20C. Ni 5 P 4 also exhibits a low voltage of ∼0.5 V with respect to Li metal, which makes it a suitable negative electrode formore »LIBs. In operando 31 P NMR and 7 Li NMR are employed to probe the lithiation and de-lithiation mechanisms upon electrochemical cycling.« less
3. A dual-role electrolyte additive for simultaneous polysulfide shuttle inhibition and redox mediation in sulfur batteries

   https://doi.org/10.1039/D1TA03425A  

   Rafie, Ayda ; Pai, Rahul ; Kalra, Vibha ( December 2021 , Journal of Materials Chemistry A)

   In Li–S batteries, the insulating nature of sulfur and Li 2 S causes enormous challenges, such as high polarization and low active material utilization. The nucleation of the solid discharge product, Li 2 S, during the discharge cycle, and the activation of Li 2 S in the subsequent charge cycle, cause a potential challenge that needs to be overcome. Moreover, the shuttling of soluble lithium polysulfide intermediate species results in active material loss and early capacity fade. In this study, we have used thiourea as an electrolyte additive and showed that it serves as both a redox mediator to overcome the Li 2 S activation energy barrier and a shuttle inhibitor to mitigate the notorious polysulfide shuttling via the investigation of thiourea redox activity, shuttle current measurements and study of Li 2 S activation. The steady-state shuttle current of the Li–S battery shows a 6-fold drop when 0.02 M thiourea is added to the standard electrolyte. Moreover, by adding thiourea, the charge plateau for the first cycle of the Li 2 S based cathodes shifts from 3.5 V (standard ether electrolyte) to 2.5 V (with 0.2 M thiourea). Using this additive, the capacity of the Li–S battery stabilizes at ∼839more »mA h g −1 after 5 cycles and remains stable over 700 cycles with a low capacity decay rate of 0.025% per cycle, a tremendous improvement compared to the reference battery that retains only ∼350 mA h g −1 after 300 cycles. In the end, to demonstrate the practical and broad applicability of thiourea in overcoming sulfur-battery challenges and in eliminating the need for complex electrode design, we study two additional battery systems – lithium metal-free cells with a graphite anode and Li 2 S cathode, and Li–S cells with simple slurry-based cathodes fabricated via blending commercial carbon black/S and a binder. We believe that this study manifests the advantages of redox active electrolyte additives to overcome several bottlenecks in the Li–S battery field.« less
4. (Digital Presentation) Accelerating the Conversion Process of Polysulfides in High Mass Loading Sulfur Cathode for the Longevity Li-S Battery

   https://doi.org/10.1149/MA2022-012383mtgabs  

   Zhang, Yuxuan ; Kivevele, Thomas ; Song, Han Wook ; Lee, Sunghwan ( July 2022 , ECS Meeting Abstracts)

   Conventional lithium-ion batteries are unable to meet the increasing demands for high-energy storage systems, because of their limited theoretical capacity. 1 In recent years, intensive attention has been paid to enhancing battery energy storage capability to satisfy the increasing energy demand in modern society and reduce the average energy capacity cost. Among the candidates for next generation high energy storage systems, the lithium sulfur battery is especially attractive because of its high theoretical specific energy (around 2600 W h kg-1) and potential cost reduction. In addition, sulfur is a cost effective and environmentally friendly material due to its abundance and low-toxicity. 2 Despite all of these advantages, the practical application of lithium sulfur batteries to date has been hindered by a series of obstacles, including low active material loading, poor cycle life, and sluggish sulfur conversion kinetics. 3 Achieving high mass loading cathode in the traditional 2D planar thick electrode has been challenged. The high distorsion of the traditional planar thick electrodes for ion/electron transfer leads to the limited utilization of active materials and high resistance, which eventually results in restricted energy density and accelerated electrode failure. 4 Furthermore, of the electrolyte to pores in the cathode and utilization ratiomore »of active materials. Catalysts such as MnO 2 and Co dopants were employed to accelerate the sulfur conversion reaction during the charge and discharge process. 5 However, catalysts based on transition metals suffer from poor electronic conductivity. Other catalysts such as transition metal dopants are also limited due to the increased process complexities. . In addition, the severe shuttle effects in Li-S batteries may lead to fast failures of the battery. Constructing a protection layer on the separator for limiting the transmission of soluble polysulfides is considered an effective way to eliminate the shuttle phenomenon. However, the soluble sulfides still can largely dissolve around the cathode side causing the sluggish reaction condition for sulfur conversion. 5 To mitigate the issues above, herein we demonstrate a novel sulfur electrode design strategy enabled by additive manufacturing and oxidative vapor deposition (oCVD). Specifically, the electrode is strategically designed into a hierarchal hollow structure via stereolithography technique to increase sulfur usage. The active material concentration loaded to the battery cathode is controlled precisely during 3D printing by adjusting the number of printed layers. Owing to its freedom in geometry and structure, the suggested design is expected to improve the Li ions and electron transport rate considerably, and hence, the battery power density. The printed cathode is sintered at 700 °C at N 2 atmosphere to achieve carbonization of the cathode during which intrinsic carbon defects (e.g., pentagon carbon) as catalytic defect sites are in-situ generated on the cathode. The intrinsic carbon defects equipped with adequate electronic conductivity. The sintered 3D cathode is then transferred to the oCVD chamber for depositing a thin PEDOT layer as a protection layer to restrict dissolutions of sulfur compounds in the cathode. Density functional theory calculation reveals the electronic state variance between the structures with and without defects, the structure with defects demonstrates the higher kinetic condition for sulfur conversion. To further identify the favorable reaction dynamic process, the in-situ XRD is used to characterize the transformation between soluble and insoluble polysulfides, which is the main barrier in the charge and discharge process of Li-S batteries. The results show the oCVD coated 3D printed sulfur cathode exhibits a much higher kinetic process for sulfur conversion, which benefits from the highly tailored hierarchal hollow structure and the defects engineering on the cathode. Further, the oCVD coated 3D printed sulfur cathode also demonstrates higher stability during long cycling enabled by the oCVD PEDOT protection layer, which is verified by an absorption energy calculation of polysulfides at PEDOT. Such modeling and analysis help to elucidate the fundamental mechanisms that govern cathode performance and degradation in Li-S batteries. The current study also provides design strategies for the sulfur cathode as well as selection approaches to novel battery systems. References: Bhargav, A., (2020). Lithium-Sulfur Batteries: Attaining the Critical Metrics. Joule 4 , 285-291. Chung, S.-H., (2018). Progress on the Critical Parameters for Lithium–Sulfur Batteries to be Practically Viable. Advanced Functional Materials 28 , 1801188. Peng, H.-J.,(2017). Review on High-Loading and High-Energy Lithium–Sulfur Batteries. Advanced Energy Materials 7 , 1700260. Chu, T., (2021). 3D printing‐enabled advanced electrode architecture design. Carbon Energy 3 , 424-439. Shi, Z., (2021). Defect Engineering for Expediting Li–S Chemistry: Strategies, Mechanisms, and Perspectives. Advanced Energy Materials 11 . Figure 1« less
5. Low-cobalt active cathode materials for high-performance lithium-ion batteries: synthesis and performance enhancement methods

   https://doi.org/10.1039/d2ta08251a  

   Mallick, Sourav ; Patel, Arjun ; Sun, Xiao-Guang ; Paranthaman, Mariappan Parans ; Mou, Mingyao ; Mugumya, Jethrine H. ; Jiang, Mo ; Rasche, Michael L. ; Lopez, Herman ; Gupta, Ram B. ( February 2023 , Journal of Materials Chemistry A)

   Cost-effective production of low cobalt Li-ion battery (LIB) cathode materials is of great importance to the electric vehicle (EV) industry to achieve a zero-carbon economy. Among the various low cobalt cathodes, Ni-rich lithium nickel cobalt manganese oxide (NCM/NMC)-based layered materials are commonly used in EVs and are attracting more attention of the scientific community due to their high specific capacity and energy density. Various synthesis routes are already established to produce Ni-rich NCM cathodes with uniform particle size distribution and high tap density. Continuous production of highly pure Ni-rich cathode materials with uniformity in inter/intra-particle compositional distribution is critically required. On the other hand, cation mixing, particle cracking, and parasitic side reactions at higher voltage and temperature are some of the primary challenges of working with Ni-rich NCM cathodes. During the past five years, several advanced modification strategies such as coating, doping, core–shell, gradient structure and single crystal growth have been explored to improve the NCM cathode performance in terms of specific capacity, rate-capability and cycling stability. The scientific advancements in the field of Ni-rich NCM cathodes in terms of manufacturing processes, material challenges, modification techniques, and also the future research direction of LIB research are critically reviewed in thismore »article.« less