Deep Lithiation Research Articles

Ternary intermediate phase mediated high energy density and kinetically accelerated Sb-Cd electrode for liquid metal batteries

Liquid metal battery (LMB) is an attractive technology that can address the big challenge of efficient utilization of renewable energies, ascribed to its potential ultralong service lifetime, ideal cost-efficiency, and high safety. However, breaking through the energy density bottleneck remains a persistent challenge, due to the limited lithiation voltage and specific capacity of cathodes. Herein, we design a novel dual-active Sb-Cd cathode, which shows a new ternary alloying discharge mechanism with reversible formation of ternary intermediate phase LiCdSb, accompanied by a high discharge voltage of 1.0 V. Coupled with the excellent Li storage capability of Cd, the Sb80Cd20 cathode attains an attractive capacity (> 500 mAh g-1), outperforming all reported LMB cathodes. More importantly, upon deep lithiation, the conversion reaction of ternary LiCdSb to Li3Sb mediates the regeneration and dispersion of Cd melt in the cathode, which constructs in situ fast electron and lithium diffusion networks for the subsequent discharge, significantly accelerating the electrode reaction kinetics. Thus, the Sb80Cd20 electrode achieves an exceptional combination of high energy density (398.4 Wh kg-1 at 200 mA cm-2) and superior rate capability (542.5 W kg-1 at 2400 mA cm-2). Additionally, the Li||Sb-Cd battery exhibits an outstanding tolerance and self-healing ability towards thermal runaway.

Deeply Lithiated Carbonaceous Materials for Great Lithium Metal Protection in All-Solid-State Batteries.

Protection of lithium (Li) metal electrode is a core challenge for all-solid-state Li metal batteries (ASSLMBs). Carbon materials with variant structures have shown great effect of Li protection in liquid electrolytes, however, can accelerate the solid-state electrolyte (SE) decomposition owing to the high electronic conductivity, seriously limiting their application in ASSLMBs. Here, a novel strategy is proposed to tailor the carbon materials for efficient Li protection in ASSLMBs, by in situ forming a rational niobium-based Li-rich disordered rock salt (DRS) shell on the carbon materials, providing a favorable percolating Li+ diffusion network for speeding the carbon lithiation, and enabling simultaneously improved lithiophilicity and reduced electronic conductivity of the carbon structure at deep lithiation state. Using the proposed strategy, different carbon materials, such as graphitic carbon paper and carbon nanotubes, are tailored with great ability to speed the interfacial kinetics, homogenize the Li plating/stripping processes, and suppress the SE decompositions, enabling much improved performances of ASSLMBs under various conditions approaching the practical application. This strategy is expected to create a novel roadmap of Li protection for developing reliable high-energy-density ASSLMBs.

Li‐Rich Organosulfur Cathode with Boosted Kinetics for High‐Energy Lithium‐Sulfur Batteries

Organosulfur materials containing sulfur–sulfur bonds are an emerging class of high‐capacity cathodes for lithium storage. However, it remains a great challenge to achieve rapid conversion reaction kinetics at practical testing conditions of high cathode mass loading and low electrolyte utilization. In this study, a Li‐rich pyrolyzed polyacrylonitrile/selenium disulfide (pPAN/Se2S3) composite cathode is synthesized by deep lithiation to address the above challenges. The Li‐rich molecular structure significantly boosts the lithium storage kinetics by accelerating lithium diffusivity and improving electronic conductivity. Even under practical test conditions requiring a lean electrolyte (Electrolyte/sulfur ratio of 4.1 μL mg−1) and high loading (7 mg cm−2 of pPAN/Se2S3), DL‐pPAN/Se2S3 exhibits a specific capacity of 558 mAh g−1, maintaining 484 mAh g−1 at the 100th cycle with an average Coulombic efficiency of near 100%. Moreover, it provides (electro)chemically stable Li resources to offset Li consumption over charge–discharge cycles. As a result the as‐fabricated anode‐free cell shows a superior cycling stability with 90% retention of the initial capacity over 45 cycles. This study provides a novel approach for fabricating high‐energy and stable Li–SPAN cells.

Cation-deficient T-Nb2O5/graphene Hybrids synthesized via chemical oxidative etching of MXene for advanced lithium-ion capacitors

Orthorhombic niobium pentoxide (T-Nb2O5) is widely acknowledged as a fast pseudocapacitive material. Nevertheless, its application is hindered by the narrow voltage window (1–3 V vs. Li/Li+) that arises from irreversible phase transformation and sluggish kinetics during deep lithiation. Herein, we demonstrate a unique method for introducing Nb vacancies in T-Nb2O5 nanoparticles via amine-assisted oxidative etching of Nb2CTx MXene, providing extra storage sites and improving structural flexibility by introducing cationic defects. Subsequently reduced graphene oxide (rGO) is employed as substrate to disperse T-Nb2O5 nanoparticles and construct T-Nb2O5/rGO nanohybrids. Multiple characterizations and computational simulations demonstrate that the resulting T-Nb2O5/rGO hybrid anode exhibits rapid and stable multi-electron transfer lithium storage. Owing to the enrichment of Nb vacancies and nanoparticle morphology, even when voltage window of 0.01–3 V (vs. Li/Li+) is extended, T-Nb2O5 exhibits a pseudocapacitive mechanism and integrity of partial crystal structure; effectively tackling the structural collapse and sluggish kinetics of T-Nb2O5. Consequently, the T-Nb2O5/rGO anode shows a superior rate capacity (148 mAh/g at 10 A/g) and cycling stability (3000 cycles at 5 A/g). Remarkably, the assembled lithium-ion capacitors achieve a high energy density of 123.7 Wh/kg, a power density of 22.5 kW/kg, and a capacity retention of 83.6% after 20,000 cycles.

Sb@Ni6 superstructure units stabilize Li-rich layered cathode in the wide voltage window

In the practical operations of Li-ion batteries, inevitable deep charge/discharge happens locally due to the intrinsic (de)lithiation inhomogeneity at the electrode and particle level, which would damage the health of batteries and even cause the safety concern. It is essential to develop the stable cathodes operating in a wide voltage window to ensure the health and safety of Li-ion batteries. Herein, we comprehensively investigate the charge/discharge behaviors of a representative Li-rich cathode Li1.2Mn0.54Ni0.13Co0.13O2 in a wide voltage window of 1.0–4.8 V, and reveal that, deep-lithiation would drive violent TM migration and severe Li/TM mixing, thereby leading to the irreversible structural transformation from layered to spinel then to rock salt, eventually causing the fast decay in electrochemical performance. Based on these understandings, a novel Li-rich cathode Li[Li1/4Mn1/2Ni1/6Sb1/12]O2 is successfully synthesized through introducing aromatic Sb@Ni6 superstructure units in the TM layers. The introduced Sb@Ni6 superstructure units can effectively tune the local oxygen environment, suppress TM migration, and stabilize the layered framework under deep lithiation. Finally, a stable charge/discharge is achieved in 1.0–4.8 V. This work deepens the understanding into the structural stability of Li-rich cathodes in a wide voltage window, and benefits the development of high-energy-density and safe cathodes.

Anion Redox in an Amorphous Titanium Polysulfide.

Amorphous transition-metal polysulfides are promising positive electrode materials for next-generation rechargeable lithium-ion batteries because of their high theoretical capacities. In this study, sulfur anion redox during lithiation of amorphous TiS4 (a-TiS4) was investigated by using experimental and theoretical methods. It was found that a-TiS4 has a variety of sulfur valence states such as S2-, S-, and Sδ-. The S2- species became the main component in the Li4TiS4 composition, indicating that sulfur is a redox-active element up to this composition. The simulated a-TiS4 structure changed gradually by lithium accommodation to form a-Li4TiS4: S-S bonds in the disulfide units and polysulfide chains were broken. Bader charge analysis suggested that the average S valency decreased drastically. Moreover, deep lithiation of a-TiS4 provided a conversion reaction to metallic Ti and Li2S, with a high practical capacity of ∼1000 mAh g-1 when a lower cutoff voltage was applied.

Unveiling the Stress‐Buffering Mechanism of Deep Lithiated Ag Nanowires: A Polymer Segmental Motion Strategy toward Ultra‐Robust Li Metal Anodes

AbstractThe severe volume expansion and uncontrolled mechanical stress restrict the high‐areal‐capacity Li storage in the alloy‐type or metallic anodes. Hitherto, most of the mitigation coating strategies are still based on the “trial‐and‐error” attempts, without the quantitative elucidation of the stress‐relaxation mechanism. This article herein constructs a prototypical coating model based on the Si‐O bonding, with the virtual and experimental screening of various structural parameters (for instance, the thickness, elasticity and cross‐linking density), for the deep lithiation of the Ag nanowires (AgNWs) framework. The operando X‐ray diffraction analysis and density functional theory calculations show that γ2(Li10Ag3) exhibits the highest Li affinity to induce the piled‐up deposits till 10 mA h cm–2; while the molecular dynamics simulations depict the optimal stress‐buffering pattern of the segmental motion in polydimethylsiloxane (PDMS) coating layer. As pairing the integrated anode of the AgNWs@PDMS slurries that casted on the AlOx modified polyethylene separator with the NMC‐811 cathode (12.5 mg cm–2), the constructed single‐layer pouch cell can balance the robust cyclability even at the mechanical deformations. This study demonstrates a tentative inverse design strategy to realize the stress‐buffering purpose upon the priori defining of the structural properties.

Improved Mass Loading of Si Electrodes in Li Ion Batteries with Si Swarf/Graphite Sheet Composites

The theoretical capacity of Si anodes (3578 mAh/g) is ~10 times as high as that of graphite anodes (372 mAh/g). Large volume changes of Si anodes during lithiation and delithiation result in peeling-off of Si and decreases in lithiation and delithiation capacities.Flake-shaped Si swarf is dispersed and wrapped by graphite sheets by sonication in N-methylpyrrolidone (NMP) and filtering the solution. The lateral size and thickness of Si swarf are in the range of 3 nm~2 μm and 2~40 nm, respectively. Graphite sheets are fabricated by sonication of expanded graphite in NMP. The lateral size and thickness of graphite sheets are in the range of 0.5~13 μm and 1~13 nm, respectively.Si/graphite sheet composites, C-coated Si swarf fabricated under ethylene atmosphere or pristine Si swarf with the theoretical capacities of 3044 mAh/g, 3287 mAh/g or 3578 mAh/g, respectively, is mixed with Ketjen black, cross-linked poly(acrylic acid) (CLPA) and poly(vinyl alcohol) (PVA) with the weight ratio of 60:20:10:10. CR2032-type coin cells are assembled with a Si electrode, a Li foil, a polyethylene separator, and 1 M LiPF6 EC/DEC (1:1 vol) electrolyte with 10 wt% fluoroethylene carbonate (FEC). The cells are cycled in the cell voltage range between 0.01 and 1.5 V during 300 cycles.The delithiation capacity of the Si/graphite sheet composite electrodes at the 300th cycle increases 14%, compared to the C-coated Si electrode. The decrease in the delithiation capacity is suppressed by graphite sheets after 180 cycles.TEM and cross section SEM images of the Si/graphite sheet composite electrodes show dispersed Si nanopowder between ultrathin graphite sheets even after the 300th cycle. In the case of the C-coated Si electrode, Si fuses after the 300th cycle.The delithiation limitation at 1200 mAh/g after deep lithiation improves the cyclability of the Si electrodes. The Si/graphite sheet composite electrode keeps the delithiation capacity of 1200 mAh/g until the 901th cycle, while the C-coated Si electrodes until the 660th cycle.The electrochemical impedance spectroscopy indicates low internal resistances for the Si/graphite sheet composite electrode. The series resistances for Si/graphite sheet composite electrode after the 6th and 300th cycles are a half and two-thirds of those for the C-coated Si electrode, respectively. The charge transfer resistance after the 300th cycle for the Si/graphite sheet composite electrode is two-thirds of that for the C-coated Si electrodes.The theoretical areal capacity is increased from 2 mAh/cm2 to 6 and 10 mA/cm2. Lithiation periods at the constant voltage of 0.01 V are 60 min for the thick Si/GS electrode without delithiation limitation and the C-coated Si electrode with delithiation limitation, 75 min for the C-coated Si electrode without delithiation limitation, and 90 min for the Si/graphite electrodes with delithiation limitation. The Si/graphite sheet composite electrodes show higher delithiation capacities than those of the C-coated Si electrodes. The delithiation capacity of the Si/graphite sheet composite electrode at the theoretical capacity of 6 mAh/cm2 decreases from 4.9 mAh/cm2 to 1.6 mAh/cm2 during 100 cycles. Delithiation limitation at 1200 mAh/g keeps the delithiation capacity of 4 mA/cm2 at the current density of 5 mA/cm2 and the theoretical capacity of 10 mAh/cm2 for more than 75 cycles.J. Electrochem. Soc. 168 (2021) 020521.

In situ TEM investigation of hexagonal WO3 irreversible transformation to Li2WO4

Lithium-ion migration at the WO3/electrolyte interface is governed by the phase transformation mechanism by which metastable states are replaced from one phase to another. Herein, an in situ single nanowire-based cell is constructed to investigate the dynamic phase transformation and morphology evolution of h-WO3 nanowire in real-time during its deep lithiation. One of the most significant features of h-WO3 lithiation is the irreversible transformation from h-WO3 to Li2WO4. There are a large number of deep ion-trapping sites composed of 4 O atoms in Li2WO4 crystal structure, that is, inserted lithium ions are irreversibly bound in these traps and nearly cannot be deintercalated. A mechanism on irreversible WO3-to-Li2WO4 transformation in deep lithiation reaction is demonstrated. With the aid of in situ transmission electron microscopy, we controllably triggered lithium-ion migration at the WO3/electrolyte interface and directly visualized the nanoscale lithium-ion migration as a stop motion movie.

Solid-electrolyte interphase formation process on Li2TiSiO5 anode in LiPF6-based carbonate electrolyte

Electrolyte decomposition in lithium-ion batteries results in the formation of a solid-electrolyte interphase (SEI), and this layer plays an essential role in determining the stability and cyclability of the battery. Besides electrolyte, electrode also affects the SEI products. In this work, the SEI formation processes on Li2TiSiO5 electrode is investigated and compared with nickel electrode using ex situ X-ray photoelectron spectroscopy. Li2TiSiO5 is a recently discovered Li-ion battery anode that works at an optimum voltage (~0.28 V vs. Li+/Li) but suffers from low coulombic efficiency. The electrolyte selected is 1 M LiPF6 in ethylene carbonate:diethyl carbonate:dimethyl carbonate (1:1:1, volumetric). The SEI layer formed on the surface of Li2TiSiO5 is shown to consist of lithium carbonate (Li2CO3), lithium alkyl carbonates (ROCOOLi), and lithium fluoride (LiF), with Li2CO3 being the dominant component. Small amounts of ROCOOLi and LiF are mostly formed in the deep lithiation stages. The SEI layer formed on nickel electrode, in comparison, only contains inorganic Li2CO3. These results suggest that Li2TiSiO5 either catalyzes or participates in the SEI formation reaction. A proper coating or a change in composition of Li2TiSiO5 can modify the property of SEI.

2D Fe2O3 nanosheets with bi-continuous pores inherited from Fe-MOF precursors: an advanced anode material for Li-ion half/full batteries

Two-dimensional (2D) materials are appealing for energy storage devices due to their intriguing chemical and physical properties. Herein, a promising anode material for both half/full cells is well prepared by constructing bi-continuous porous structure in Fe2O3 nanosheets (bp-Fe2O3) through a target construction method. Notably, the obtained bp-Fe2O3 exhibits a unique wrinkled layer structure composed by ultrasmall Fe2O3 nanoparticles, which can well shorten the charge diffusion pathway. Furthermore, the wrinkled layer structure and the presence of pores in the bp-Fe2O3 sample are able to accommodate the volume variation during deep lithiation–delithiation processes, and enable electrolyte easy penetration to the whole electrode, thus significantly improving the electrochemical performance. Benefiting from the favorable electrode framing together with fast lithiation dynamics, the prepared bp-Fe2O3 exhibits considerably better electrochemical performance in half/full cells for lithium ion batteries (LIBs), as well as superior low temperature (low-T) performance. In detail, when cycled at 1.5 A g−1, 2D bp-Fe2O3 electrode displays a reversible capacity up to 818.7 mAh g−1 for 350 cycles. Even at a stern temperature of 0 °C and −25 °C, the as-prepared bp-Fe2O3 still presents a capacity of 840.3 and 635.6 mAh g−1 at 0.5 A g−1, respectively, suggesting the normal operation of LIBs under low temperature condition. More competitively, the full cell fabricated by bp-Fe2O3 anode and LiFePO4 cathode gives excellent electrochemical performance (421.2 mAh g−1 after 80 cycles at 0.1 A g−1) between 0.4 and 3.4 V and high energy density of 247.03 Wh kg−1.

Scalable Engineering of Bulk Porous Si Anodes for High Initial Efficiency and High-Areal-Capacity Lithium-Ion Batteries.

Nano-Si has been long-hampered in its use for practical lithium battery anodes due to its intrinsic high surface area. To improve the Coulombic efficiency and areal mass loading, we extend the starting materials from nano-Si to photovoltaic waste Si powders (∼1.5 μm). Unique morphology design and interfacial engineering are designed to overcome the particle fracture of micrometer Si. First, we develop a Cu-assisted chemical wet-etching method to prepare micrometer-size bulk-porous Si (MBPS), which provides interconnected porous space to accommodate volume expansion. In addition, a monolithic, multicore, interacting MBPS/carbonized polyacrylonitrile (c-PAN) electrode with strong interfacial Si-N-C is designed to improve the interparticle electrical conductivity during volume expansion and shrinkage. Furthermore, intermediate Si nanocrystals are well-maintained during the lithiation of MBPS, which facilitates the reversibility of lithiation-delithiation process. As a result, the MBPS/c-PAN electrodes exhibit a reversible specific capacity of 2126 mAh g-1 with a high initial Coulombic efficiency of 92%. Moreover, even after increasing the capacity loading to 3.4 mAh cm-2, the well-designed electrode shows a capacity retention of 94% in the first 50 cycles at a current density of 0.2 A g-1 with deep lithiation and delithiation processes between 0.005 and 2.5 V.

Employment of ultra-thin carbon layer-coated porous tin oxide as anode in lithium-ion capacitor

A porous SnO2 electrode with an ultra-thin 2-nm-thick coating of carbon (SnO2@C) was prepared by a hydrothermal method. The thin carbon layer acted as a relaxant layer alleviating the stress of the volume expansion of the SnO2 active material during intercalation/de-intercalation of lithium ions. The pre-lithiated SnO2@C was employed as an anode material for a non-aqueous lithium-ion capacitor (LIC) using commercial activated carbon (YP-80F) as the cathode. Different states of discharge of the pre-lithiated SnO2@C anode were characterized. At different lithiation degrees, phase transformation and morphology changes of the SnO2 active material affected the electrochemical performance of the LIC system. Shallow lithiation provided insufficient lithium ions to the activated carbon cathode, yielding poor specific energy. Excessively deep lithiation risked severe crack formation on the surfaces of the SnO2 particles, affecting the electrochemical performance at high current densities. Other parameters, including the negative-to-positive electrode mass balance and cut-off voltage control, were also studied regarding their effects on performance. The fabricated LIC (SnO2@C/Activated carbon) delivered a maximum energy of 130 W h kg−1 and a maximum specific power of 6900 W kg−1.

Low-Cost and High-Performance Anode in Li Ion Batteries with Si Nanopowder Fabricated from Swarf

Si nanopowder has been applied to an anode material with a high theoretical capacity of 3578 mAh/g, i.e., ~10 times higher than that for currently used graphite. High-cost Si nanomaterials have been used for suppression of peeling-off of Si in fundamental researches [1,2]. In the present study, Si nanopowder is fabricated from Si swarf by use of ball milling and beads milling methods.Si swarf is an industrial waste generated during slicing Si ingot to produce Si wafers for solar cells. The weight of Si swarf is almost the same as that of the Si wafers. Si nanopowder possesses flake-like shape consisting of two largely different sizes, i.e., several hundred nm and less than 30 nm.Si swarf was milled in acetone using the ball milling method. Fabricated Si nanopowder was annealed at 1000°C under hydrogen atmosphere, followed by annealing at 1000°C under ethylene atmosphere to coat Si nanopowder with a ∼10 nm carbon layer. C-coated Si nanopowder, Ketjen Black, carboxymethylcellulose ammonium and poly(vinyl alcohol) were mixed with the weight ratio of 50:25:20:5. A working electrode was fabricated by coating copper foil with this mixture, and dried at 120°C under vacuum. A Si working electrode, a lithium foil as a counter electrode, and a polyethylene separator were packed in a coin cell (CR 2032-type) with 1 M LiPF6 in a mixture of ethylene carbonate and diethyl carbonate (1:1 by volume). The cells were cycled in the cell voltage range between 0.01 and 1.5 V. The lithiation and delithiation current densities were set at 180 mA/g for the 1st~5th cycles and at 1800 mA/g for the subsequent 6th~300th cycles.Addition of 10wt% FEC to the electrolytic solution gave the delithiation capacity of ~1600 mAh/g at the 100th cycles because of formation of a thin solid electrolyte interphase which prevented cracking of Si by suppressing the Si volume change [3]. Without FEC, the delithiation capacity decreased from the 40th cycle. C-coating at the C/Si weight ratio of ~0.1 greatly suppressed crack formation because Si was lithiated homogeneously by formation of electric passes and frameworks with high density of active materials are formed [3]. Without C-coating, the delithiation capacity decreased to 200 mAh/g at the 20th cycle.Limitation of the delithiation capacity at 1500 mAh/g after deep lithiation at 0.01 V gave the delithiation capacity of 1480 mAh/g at the 300th cycle. On the other hand, the delithiation capacity at the 300th cycle decreased to 950 and 860 mAh/g for no capacity limitation and limitation of the lithiation capacity at 1500 mAh/g after deep delithiation at 1.5 V, respectively [4].Lithiation and delithiation curves can be divided to 9 regions from their slopes. These regions can be categorized to 5 regions by the reaction mechanism as reported previously [4].The overvoltage at each region boundary for the limitation of the delithiation capacity was less than that for the limitation of the lithiation capacity. This result indicates better interparticle contacts for the limitation of the delithiation capacity than that for the limitation of the lithiation capacity. From the reaction mechanism reported previously [5-9], it is known that an c-Li15Si4 layer is formed during a few cycles on the Si surface and is present through during the lithiation and delithiation cycles. Because this phase is more stable than a-Li15Si4, the delethiation proceeds from the inner a-LixSi (0<x3.75) phase, which causes only slight change of the Si size for the limitation of the delithiation capacity case. However, for the limitation of the lithiation capacity, only a-LixSi (0<x<3.75) and a-Si are present, leading to pealing-off of Si due to the large Si volume change. For no capacity limitation, the overvoltage during delithiation was close to that for the limitation of the delithiation capacity, while the overvoltage during lithiation was close to that for the limitation of the lithiation capacity. This result indicates that a part of the interparticle contacts is restored during deep lithiation and destroyed during deep delithiation. [1] X.H. Liu et al., ACS Nano 6, 1522 (2012).[2] Y. Ru et al., RSC Adv. 4, 71 (2014).[3] T. Matsumoto et al., J. Alloys Compd. 720, 529 (2017).[4] K. Kimura et al., J. Electrochem. Soc. 164, A995 (2017).[5] M.R. Zamfir et al., J. Mater. Chem. A 1, 9566 (2013).[6] L. Liu et al., Sci. Rep. 4, 3863 (2013).[7] X.H. Liu et al., Nano Lett. 11, 2251 (2011).[8] J. Li et al., J. Electrochem. Soc. 154, A156 (2007).[9] N. Aoki et al., ChemElectroChem. 3, 959 (2016). Figure 1

Cycling Behavior of Silicon-Containing Graphite Electrodes, Part B: Effect of the Silicon Source

Silicon (Si) is a promising candidate to enhance the specific charge of graphite electrode, but there is no consensus in the literature on its cycling mechanism. Our aim in this study was to understand Si electrochemical behavior in commercially viable graphite/Si electrodes. From the comparison of three types of commercial Si particles with a producer-declared particle sizes of 30–50 nm, 70–130, and 100 nm, respectively, we identified the presence of micrometric Si agglomerates and the Si micro- and mesoporosity as the main physical properties affecting the cycling performance. Moreover, ex situ SEM, XRD, and Raman investigations allowed us to understand the lithiation/delithiation mechanism for each type of Si particles. For nanoscale Si particles, the entire Si particle is utilized, resulting in high specific charge, and the stress induced by the formation of Li15Si4 alloy upon deep lithiation is well managed within the Si mesoporosity. This leads to reversible cycling behavior and, thus, to good cycli...

Porous Coconut Shell Carbon Offering High Retention and Deep Lithiation of Sulfur for Lithium-Sulfur Batteries.

Retaining soluble polysulfides in the sulfur cathodes and allowing for deep redox are essential to develop high-performance lithium-sulfur batteries. The versatile textures and physicochemical characteristics of abundant biomass offer a great opportunity to prepare biochar materials that can enhance the performance of Li-S batteries in sustainable mode. Here, we exploit micro-/mesoporous coconut shell carbon (CSC) with high specific surface areas as a sulfur host for Li-S batteries. The sulfur-infiltrated CSC materials show superior discharge-charge capacity, cycling stability, and high rate capability. High discharge capacities of 1599 and 1500 mA h g-1 were achieved at current rates of 0.5 and 2.0 C, respectively. A high reversible capacity of 517 mA h g-1 was retained at 2.0 C even after 400 cycles. The results demonstrate a high retention and a deep lithiation of the CSC-confined sulfur. The success of this strategy provides insights into seeking high-performance biochar materials for Li-S batteries from abundant bioresources.

Insight in the degradation of polyquinone-based cathode material in lithium-organic battery under cycling

Electrochemical lithiation of organic polyquinone-based cathode material can occur irreversibly leading thus to a rapid deterioration of the battery performance. Carefully controlled degree of lithium intercalation within the defined charge/ discharge potential window provides a stable battery operation within 170 cycles with 100% coulombic efficiency. DFT calculations revealed that deep lithiation results in a strong conformational reorganization of the polymer domains leading to repeatable expansion and shrinkage of the electroactive material and a rapid loss of the cathode integrity.

Scalable Study on Nanostructured Carbon – Sulfur Composite Electrodes for High Energy Lithium Sulfur (Li-S) Battery

Sulfur is a promising cathode material for lithium sulfur batteries due to its high theoretical capacity (1675 mAh/g). Sulfur cathodes generally suffers from fast capacity degradation and poor Coulombic efficiency originated from the dissolution of intermediate discharge products (polysulfides, Li2S) in the electrolyte. The polysulfide dissolution causes loss of active sulfur and suppresses its deep lithiation, which becomes especially severe during slow charge−discharge processes and deteriorates electrochemical performances at low cycling rates. To enhance the electrochemical performance of sulfur, carbon black as conductive material has been dispersed in sulfur. Here we report a scalable study on nanostructured carbon-sulfur (S1-x Cx where x=.25, .35 &.40 etc.) composites as a cathode fabricated by ball-milling technique for lithium sulfur batteries. The characterization of these nanostructured composites have been performed by X-ray diffraction (XRD), scanning electron microscopy (SEM) and RAMAN spectroscopy. The electrochemical performance of C-sulfur composite cathodes have been found to be enhanced and stable at deep charge-discharge.

Scalable Study on Nanostructured Carbon –Sulfur Composite Electrodes for High Energy Lithium Sulfur (Li-S) Battery

Sulfur is a promising cathode material for lithium sulfur batteries due to its high theoretical capacity (1675 mAh/g). Sulfur cathodes generally suffers from fast capacity degradation and poor Coulombic efficiency originated from the dissolution of intermediate discharge products (polysulfides, Li2S) in the electrolyte. The polysulfide dissolution causes loss of active sulfur and suppresses its deep lithiation, which becomes especially severe during slow charge−discharge processes and deteriorates the electrochemical performances at low cycling rates. Here we report a scalable study on nanostructured carbon-sulfur (S1-x Cx where x=.50,& .40 etc.) composites as a cathode fabricated by ballmiling technique for lithium sulfur battery. To enhance the electrochemical performance of lithium- sulfur battery, carbon black as a conductive material has been dispersed in sulfur. The initial characterization of these nanostructured composites have been performed by XRD, SEM and RAMAN spectroscopy. For electrochemical performance coin cells have been fabricated and are under testing for charge/discharge charcteristics by SOLATRON. Figure 1

Improvement of Cyclability of Li-Ion Batteries Using C-Coated Si Nanopowder Electrode Fabricated from Si Swarf with Limitation of Delithiation Capacity

We have fabricated Si nanopowder from Si swarf using the simple ball milling method, and applied to Li-ion battery electrodes. Limitation of the delithiation capacity after deep lithiation at 0.01 V is the most effective to achieve a constant high capacity for long cycles. The delithiation capacity keeps constant at 1500 mAh/g until the 290th cycle, and it slightly decreases to 1480 mAh/g at the 300th cycle. However, without limitation of the lithiation and delithiation capacities in the voltage range between 1.5 and 0.01 V, the delithiation capacity monotonically decreases with the cycle number, and it becomes 950 mAh/g at the 300th cycle. With limitation of the lithiation capacity at 1500 mAh/g after deep delithiation at 1.5 V, the delithiation capacity keeps 1470 mAh/g until the 137th cycle, and then decreases monotonically with the cycles to 860 mAh/g at the 300th cycle. With limitation of the delithiation capacity, the overvoltage estimated from the lithiation and delithiation curves is the lowest, and peeling-off of Si nanopowder from the Si electrode is suppressed because of limited size changes of Si nanopowder during lithiation and delithiation of Si nanopowder.