Omics is a discipline that identifies and quantifies molecular processes that contribute to the form and function of living systems. Here, we translate omics to study battery systems. By employing precision analytical capabilities across chemical space, we delineate the structure, function, and evolution of interphases when cycling Li-nickel manganese oxide (NMC)811 cells at high power and high voltage with mixed-salt locally superconcentrated electrolytes. Despite differences in their make-up, top-performing electrolytes converged in their cathode–electrolyte interphase (CEI) chemistries, which were unexpectedly enriched with fluoroethers (upregulation) and depleted with LiF (downregulation). Moreover, these atypical CEIs more effectively suppressed leakage current, cathode corrosion, and cathode fracturing, extending battery life. Pouch cells (130 mAh) assembled with 50-μm-thick Li foil, semi-solid NMC811 electrodes (9 mAh cm−2), and lean electrolyte (2.2 Ah g−1) showed excellent power retention over more than 100 cycles using a realistic mission for electric vertical take-off and landing.

Anode-free sodium metal batteries are highly promising for future energy storage but suffer from much faster cycling degradation as they are sensitive to even trace levels of irreversible side reactions. This work focuses on the most practical Al foil current collectors and systematically examined the effect of nanosized carbon coating on improving the Na plating and stripping stability. We identified that the carbon-Al junction interface generated by carbon coating enabled more uniform Na deposition with lower overpotentials, delivering higher than 99.8% Faradaic efficiencies for a wide range of cycling currents between 0.5 and 3.0 mA cm-2. This performance is much better than the 96.4% efficiency observed on uncoated Al foils under the same conditions and is also confirmed under lean electrolyte and freezing electrolyte conditions and can be attributed to the stronger interfacial binding and enhanced sodiophilic properties of the carbon-aluminum junction sites. These sites not only ensure uniform Na plating but also eliminates side reactions that would otherwise cause electrolyte depletion. As a result, Na-metal free full cells assembled with a high capacity Na3V2(PO4)3 cathode delivered similar to 93% capacity retention for 100 cycles, higher than the similar to 42% of retention of uncoated Al foil.

Li–S batteries are among the most promising energy storage technologies but their commercialization faces substantial challenges, largely due to difficulties in controlling their reaction pathways under practical conditions. Here, the synthesis of strongly coupled Fe 3 O 4 and N‐doped carbon directly in flexible carbon cloth is demonstrated, as well as their novel use for hosting sulfur with outstanding performance for Li–S batteries. It is discovered that the synergistic effects of Fe 3 O 4 and N‐carbon bring strong adsorption toward lithium polysulfide, and ensure nearly complete conversion of short‐chain polysulfide to Li 2 S during discharge. The Li 2 S solids generated on these novel hosts are extremely reactive and can be readily charged back to S without a noticeable overpotential. The critical roles of Fe 3 O 4 and N‐doped carbon are studied and direct correlations are established between their surface concentration/crystallinity and the Li 2 S 4 to Li 2 S conversion capacity. This novel manipulation of polysulfide conversion allows to fabricate freestanding and flexible sulfur cathodes that deliver a specific capacity of 1316 mAh g −1 at 0.1C and stable cycling for 1000 cycles at 0.2C under a high sulfur loading of ≈4.7 mg cm −2 .

The practical deployment of lithium sulfur batteries demands stable cycling of high loading and dense sulfur cathodes under lean electrolyte conditions, which is very difficult to realize. We describe here a strategy of fabricating extremely dense sulfur cathodes, designed by integrating Mo6S8 nanoparticles as a multifunctional mediator with a Li-ion conducting binder and a high-performance Fe3O4@N-carbon sulfur host. The Mo6S8 nanoparticles have substantially faster Li-ion insertion kinetics compared with sulfur, and the produced LixMo6S8 particles have spontaneous redox reactivity with relevant polysulfide species (such as Li4Mo6S8 + Li2S4 ↔ Li3Mo6S8 + Li2S, ΔG = -84 kJ mol-1), which deliver a true redox catalytic sulfur conversion mechanism. In addition, LixMo6S8 particles strongly absorb polysulfide during battery cycling, which provides a quasi-solid sulfur conversion pathway and almost eliminated polysulfide dissolution. Such a pathway not only promotes growth of uniform Li2S that can be readily charged back with nearly no overpotential, but also mitigates the polysulfide-induced Li metal corrosion issue. The combination of these benefits enables stable and high capacity cycling of dense sulfur cathodes under a low electrolyte to sulfur ratio (4.2 μL mg-1), as demonstrated with cathodes with volumetric capacities of at least 1.3 Ah cm-3 and capacity retentions of ∼80% for 300 cycles. Furthermore, stable cycling of batteries under a practically relevant N/P ratio of 2.4 is also demonstrated.

In article number 1707234, NH4TFSI is presented as a functional electrolyte additive to alleviate the passivation of Li2S for Li-S batteries under lean electrolyte conditions by Yuyan Shao, Jun Liu, and co-workers. This additive enhances the dissociation of Li2S and facilitates the homogeneous formation of Li2S particles, which significantly promotes the reversibility and reaction kinetics of sulfur and extends the cycle life.

Reducing the electrolyte amount is critical for the high specific energy of lithium–sulfur (Li–S) batteries in practice. The reduced electrolyte condition (a so‐called “lean electrolyte”) raises a complex situation for sulfur redox reactions since the reactions rely on the electrolyte mediation. The insulating nature of discharge product Li2S and its uncontrollable accumulation (passivation) at the cathode interface is one of the major challenges for stable cycling of a Li–S battery under lean electrolyte condition. In this study, it is presented that the NH4TFSI additive in electrolyte solution greatly alleviates the passivation issue in Li–S batteries under lean electrolyte conditions. The ammonium additive enhances the dissociation of Li2S and largely reduces the insoluble and large Li2S particles in the sulfur cathodes, which facilitate the reversible and sustainable redox reactions of sulfur. Therefore, the cycle life of Li–S batteries under lean electrolyte conditions is significantly improved. In addition, it is found that the morphology of Li anodes is dependent on the cathode structures. An ammonium additive enables homogeneous surface of cathode and Li anode and extended cycle life.

The electrolyte is a crucial component of lithium-sulfur (Li-S) batteries, as it controls polysulfide dissolution, charge shuttling processes, and solid-electrolyte interphase (SEI) layer formation. Experimentally, the overall performance of Li-S batteries varies with choice of solvent system and Li-salt used in the electrolyte, and a lack of predictive understanding about the effects of individual electrolyte components inhibits the rational design of electrolytes for Li-S batteries. Here we analyze the role of the counteranions of common Li-salts (such as TfO-, FSI-, TFSI-, and TDI-) when dissolved in DOL/DME (1:1 by vol.) for use in Li-S batteries. The evolution of ion-ion and ion-solvent interactions due to various anions was analyzed using O-17 NMR and pulsed-field gradient (PFG) NMR and then correlated with electrochemical performance in Li-S cells. These data reveal that the formation of the passivation layer on the anode and the loss of active materials from the cathode (evidenced by polysulfide dissolution) are related to anion mobility and affinity with lithium polysulfide, respectively. For future electrolyte design, anions with lower mobility and weaker interactions with lithium polysulfides may be superior candidates for increasing the long-term stability of Li-S batteries.

High-surface-area, nanostructured carbon is widely used for encapsulating sulfur and improving the cyclic stability of Li–S batteries, but the high carbon content and low packing density limit the specific energy that can be achieved. Here we report an approach that does not rely on sulfur encapsulation. We used a low-surface-area, open carbon fibre architecture to control the nucleation and growth of the sulfur species by manipulating the carbon surface chemistry and the solvent properties, such as donor number and Li + diffusivity. Our approach facilitates the formation of large open spheres and prevents the production of an undesired insulating sulfur-containing film on the carbon surface. This mechanism leads to ~100% sulfur utilization, almost no capacity fading, over 99% coulombic efficiency and high energy density (1,835 Wh kg −1 and 2,317 Wh l −1 ). This finding offers an alternative approach for designing high-energy and low-cost Li–S batteries through controlling sulfur reaction on low-surface-area carbon.

The lithium-sulfur (Li-S) battery is a very promising candidate for the next generation of energy storage systems required for electrical vehicles and grid energy storage applications due to its very high theoretical specific energy (2500Whkg−1). However, low Coulombic efficiency (CE) during repeated Li metal plating/stripping has severely limited the practical application of rechargeable Li-S batteries. In this work, a new electrolyte system based on a high concentration of LiNO3 in diglyme (G2) solvent is developed which enables an exceptionally high CE for Li metal plating/stripping and thus high stability of the Li anode in the sulfur-containing electrolyte. The tailoring of electrolyte properties for the Li anode has proven to be a highly successful strategy for improving the capacity retention and cycle life of Li-S batteries. This electrolyte provides a CE of greater than 99% for over 200 cycles of Li plating/stripping. In contrast, the Li anode cycles for less than 35 cycles (with a high CE) in the state-of-the-art 1M LiTFSI + 0.3M LiNO3 in 1,3-dioxolane:1,2-dimethoxyethane (DOL:DME) electrolyte under the same conditions. The stable Li anode enabled by the new electrolyte may accelerate the applications of high energy density Li-S batteries in both electrical vehicles and large-scale grid energy storage markets.

With a theoretical specific energy of 2500 W h kg-1 and energy density of 2800 W h L-1, the Li-S battery system is believed to provide the step-up in energy density necessary for lithium-based battery technologies to expand from portable electronics to transportation and grid-storage applications.1 However, the growth of dendrites during repeated Li plating/stripping and the low coulombic efficiency (CE) of these processes have limited application of rechargeable Li metal batteries.2 For example, a 300% excess amount of lithium often used in these batteries would directly result in halving the theoretical specific energy of the Li/S cells. In this presentation, the design of new electrolyte systems which enable high CE of lithium metal plating/stripping and high stability in the sulfur environment will be discussed. Tailoring of electrolyte properties for the lithium negative electrode has proven to be a successful strategy for improving the capacity retention and cycle life of Li-S full cells. This also enables lower electrolyte/sulfur mass ratios to be used and a lower excess of lithium metal; ultimately increasing the energy density of the system. A new class of electrolytes based on a high concentration of selected lithium salts in pure diethylene glycol dimethyl ether (diglyme) solvent provides a CE for lithium plating/stripping of greater than 99% for over 200 cycles and greater than 95% for over 500 cycles (Figure 1). In contrast, lithium metal cycles for less than 40 cycles at high CE in the standard 1 M LiTFSI + 2wt% LiNO3 in DOL:DME electrolyte. To realize the benefits of sulfur cathodes over intercalation cathodes currently using in Li-ion cells, high loading (high capacity) cathodes need to be used. In Figure 2a, a Cu||Li cell is cycled with the new diglyme-based electrolyte to a capacity of 6 mAh/cm2 at a current density of 0.6 mA/cm2 (C/10). Even at this high capacity, lithium is cycling with >99% CE. Lithium symmetrical cells were also cycled at a current density of 0.5 mA/cm2 to 5 mAh/cm2 (Figure 2b). In this case, the increase in polarization was used a metric to determine the practical cycle life of Li metal in the different electrolytes. No polarization is observed for the diglyme-based electrolyte after 2200 hours in the Li||Li cell. The inexpensive sulfur cathode paired with a low excess of lithium metal and the low-cost salt/solvent system may accelerate the applications of high energy density Li-S batteries in both electrical vehicles and large-scale grid energy storage markets. References 1. A. Manthiram, Y. Fu, S.-H. Chung, C. Zu, Y.-S. Su, Chem. Rev. 2014, 114, 11751-11787. 2. W. Li, H. Yao, K. Yan, G. Zheng, Z. Liang, Y.-M. Chiang, Y. Cui, Nature Comm. 2015, 6, 7436. Figure 1

Polysulfides Resulting from Competitive Salt and Solvent Interactions Nav Nidhi Rajput,*,†,⊥ Vijayakumar Murugesan,‡,⊥ Yongwoo Shin,† Kee Sung Han,‡,⊥ Kah Chun Lau, Junzheng Chen,‡ Jun Liu,‡,⊥ Larry A. Curtiss, Karl T. Mueller,‡,⊥ and Kristin A. Persson*,†,⊥ †Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States ‡Pacific Northwest National Laboratory, Richland, Washington 99352, United States Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439, United States Department of Physics and Astronomy, California State University, Northridge, California 91330, United States Joint Center for Energy Storage Research (JCESR), Lemont, Illinois 60439, United States

In rechargeable Li-S batteries, the uncontrollable passivation of electrodes by highly insulating Li2S limits sulfur utilization, increases polarization, and decreases cycling stability. Dissolving Li2S in organic electrolyte is a facile solution to maintain the active reaction interface between electrolyte and sulfur cathode, and thus address the above issues. Herein, ammonium salts are demonstrated as effective additives to promote the dissolution of Li2S to 1.25 M in DMSO solvent at room temperature. NMR measurements show that the strong hydrogen binding effect of N-H groups plays a critical role in dissolving Li2S by forming complex ligands with S2- anions coupled with the solvent's solvating surrounding. Ammonium additives in electrolyte can also significantly improve the oxidation kinetics of Li2S, and therefore enable the direct use of Li2S as cathode material in Li-S battery system in the future. This provides a new approach to manage the solubility of lithium sulfides through cation coordination with sulfide anion.

Li-S batteries have been extensively studied using rigid carbon as the host for sulfur encapsulation, but improving the properties with a reduced electrolyte amount remains a significant challenge. This is critical for achieving high energy density. Here, we developed a soft PEO10LiTFSI polymer swellable gel as a nanoscale reservoir to trap the polysulfides under lean electrolyte conditions. The PEO10LiTFSI gel immobilizes the electrolyte and confines polysulfides within the ion conducting phase. The Li-S cell with a much lower electrolyte to sulfur ratio (E/S) of 4 gE/gS (3.3 mLE/gS) could deliver a capacity of 1200 mA h/g, 4.6 mA h/cm2, and good cycle life. The accumulation of polysulfide reduction products, such as Li2S, on the cathode, is identified as the potential mechanism for capacity fading under lean electrolyte conditions.

This work describes the synthesis of Chevrel phase Mo6S8 nanocubes and its application as the anode material for rechargeable Zn-ion batteries. Mo6S8 can host Zn(2+) ions reversibly in both aqueous and nonaqueous electrolytes with specific capacities around 90 mAh/g, and exhibited remarkable intercalation kinetics and cyclic stability. In addition, we assembled full cells by integrating Mo6S8 anodes with zinc-polyiodide (I(-)/I3(-))-based catholytes, and demonstrated that such full cells were also able to deliver outstanding rate performance and cyclic stability. This first demonstration of a zinc-intercalating anode could inspire the design of advanced Zn-ion batteries.

Fast capacity fading due to polysulfide dissolution is a significant challenge for Li-S batteries. Porous carbon is widely studied for physically trapping polysulfide species. Here, we report a different chemical approach through suppressing polysulide dissolution using lithium 2-trifluoromethyl-4,5-dicyanoimidazole (LiTDI) as a supporting salt in electrolytes. The electrolyte to sulfur ratio(E/S) is carefully controlled and the results show that under the optimized E/S ratio the cycling stability of the lithium sulfur cell is improved in the LiTDI supported electrolyte. The Combined experimental and simulation results reveal the dissolution mechanism of lithium polysulfides and suggest that the dominating disproportionation product of Li 2 S 8 is Li 2 S 4 in the LiTDI electrolyte due to a coordination between Li + and TDI anion, rather than separated Li 2 S 3 and Li 2 S 5 as in the LiTFSI electrolyte. The Li 2 S 4 would continuously form a Li 4 S 8 dimer and precipitate out. Detailed DFT calculation and Li NMR results suggest lithium ion cation has a higher solvation level in the TDI based electrolyte. Furthermore, the Li-S cells with LiTDI based electrolyte with optimized sulfur to electrolyte ratio was firstly applied into a high loading cathode and achieve a stable cycling. The use of the electrolyte with the LiTDI salt (with polysulfide and LiNO 3 additives) enables a cell with a high sulfur loading (3 mg-S cm -2 ) to deliver a 1.67 mAh cm -2 areal capacity after 300 stable cycles at a high current (2.4 mA cm -2 ) density. The fading of Li metal anode is also suppressed. Figure 1 Capacity retention of cells with (a) 1M LiTFSI and (b) 1M LiTDI in DOL/DME electrolytes (no additives) with different sulfur to electrolyte (S/E) ratios at a C/5 rate. 1C = 1675 mA g -1 of S and the cathode was prepared with 64 wt% S (i.e., S 8 ), 16 wt% MWCNTs, 10 wt% Super P carbon additive and 10 wt% PVDF binder. Figure 1

Conversion-type reactions based battery chemistry presents a great promise for next-generation energy storage. It is based on using the chemical reaction (also called chemical transformation) of the working ion to store energy, different than intercalation-type reactions as used in today’s Li-ion batteries. Good examples include Li-S, Li-O2, and broadly speaking metal electrodes (Li, Mg, Zn, etc.). Interfaces generally play a more crucial role in these battery chemistry systems because of the complexity of this type of reaction even though each of the systems has its unique characteristics. This not only includes electrode/electrolyte interfaces, but also the interfaces within the electrode materials. Here, we use two examples of battery chemistry to demonstrate how the manipulation of interfaces can promote the conversion-type reactions for energy storage: Mg chemistry and Li-S chemistry. In Mg battery chemistry, due to the divalent nature of Mg2+, the ion transport kinetics in solid host materials is limited. Therefore, the development of Mg battery has been limited by poor performance of electrode materials. We have developed two conversion-type electrode materials with improved Mg2+ storage performance: SnSb alloys for anode1 , 2 and V2O5 nanoclusters for cathode.3 More importantly, our experimental and theoretical modeling reveal that the interfaces between the multicomponent phases generated during repeated magnesiation–demagnesiation is responsible for the improved performance of SnSb; a surface-controlled reaction of Mg2+ and V2O5, denoted as a molecular energy storage mechanism, improves the reaction kinetics which increases the rates and capability. In Li-S battery chemistry, control of solution chemistry and nucleation of polysulfides (on cathode host surface) is crucial for improved capacity and cycling stability. We have demonstrated that, through tuning the solubility of polysulfides in electrolytes, an improved cycling stability is achieved. The controlled nucleation of polysulfides on carbon nanofiber surface leads to the formation of a unique porous microsphere structure of Li2S. This unique porous Li2S microsphere enables a close to 100% utilization of S (specific capacity >1600mAh/gS); it also decreases the passivation of cathode. This opens up a new avenue for Li-S R&D of using low surface area carbon host materials, thus a great potential for high pack density and low electrolyte/sulfur ratio in Li-S cells. In this talk, we will present our understanding on these interface-related conversion-type reactions and recent progress of material innovation that improves device performance. New electrode architecture engineering will also be discussed. 1. Y. W. Cheng, Y. Y. Shao, L. R. Parent, M. L. Sushko, G. S. Li, P. V. Sushko, N. D. Browning, C. M. Wang and J. Liu, Adv. Mater., 2015, 27, 6598-6505. 2. L. R. Parent, Y. W. Cheng, P. V. Sushko, Y. Y. Shao, J. Liu, C. M. Wang and N. D. Browning, Nano Lett., 2015, 15, 1177-1182. 3. Y. W. Cheng, Y. Y. Shao, V. Raju, X. L. Ji, B. L. Mehdi, K. S. Han, M. H. Engelhard, G. S. Li, N. D. Browning, K. T. Mueller and J. Liu, Advanced Functional Materials, 10.1002/adfm.201505501, 2016.

With the significant progress made in the development of cathodes in lithium‐sulfur (Li‐S) batteries, the stability of Li metal anodes becomes a more urgent challenge in these batteries. Here the systematic investigation of the stability of the anode/electrolyte interface in Li‐S batteries with concentrated electrolytes containing various lithium salts is reported. It is found that Li‐S batteries using LiTFSI‐based electrolytes are more stable than those using LiFSI‐based electrolytes. The decreased stability is because the N–S bond in the FSI − anion is fairly weak and the scission of this bond leads to the formation of lithium sulfate (LiSO x ) in the presence of polysulfide species. In contrast, in the LiTFSI‐based electrolyte, the lithium metal anode tends to react with polysulfide to form lithium sulfide (LiS x ), which is more reversible than LiSO x formed in the LiFSI‐based electrolyte. This fundamental difference in the bond strength of the salt anions in the presence of polysulfide species leads to a large difference in the stability of the anode‐electrolyte interface and performance of the Li‐S batteries with electrolytes composed of these salts. Therefore, anion selection is one of the key parameters in the search for new electrolytes for stable operation of Li‐S batteries.