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In the pursuit of urgently-needed, energy dense solid-state batteries for electric vehicle and portable electronics applications, halide solid electrolytes offer a promising path forward with exceptional compatibility against high-voltage oxide electrodes, tunable ionic conductivities, and facile processing. For this family of compounds, synthesis protocols strongly affect cation site disorder and modulate Li+ mobility. In this work, we reveal the presence of a high concentration of stacking faults in the superionic conductor Li3YCl6 and demonstrate a method of controlling its Li+ conductivity by tuning the defect concentration with synthesis and heat treatments at select temperatures. Leveraging complementary insights from variable temperature synchrotron X-ray diffraction, neutron diffraction, cryogenic transmission electron microscopy, solid-state nuclear magnetic resonance, density functional theory, and electrochemical impedance spectroscopy, we identify the nature of planar defects and the role of nonstoichiometry in lowering Li+ migration barriers and increasing Li site connectivity in mechanochemically-synthesized Li3YCl6. We harness paramagnetic relaxation enhancement to enable 89Y solid-state NMR, and directly contrast the Y cation site disorder resulting from different preparation methods, demonstrating a potent tool for other researchers studying Y-containing compositions. With heat treatments at temperatures as low as 333 K (60{\deg}C), we decrease the concentration of planar defects, demonstrating a simple method for tuning the Li+ conductivity. Findings from this work are expected to be generalizable to other halide solid electrolyte candidates and provide an improved understanding of defect-enabled Li+ conduction in this class of Li-ion conductors.

In this study, the relationship between structure, cation disorder and Na-ion conduction properties is elucidated in a series of Na3−xY1−xZrxCl6 solid electrolytes.

Summary Conventional Li-ion cathode materials are dominated by well-ordered structures, in which Li and transition metals occupy distinct crystallographic sites. We show in this paper that profoundly new degrees of freedom for the optimization of electrochemical properties may be accessed if controllable cation disorder is introduced. In a class of high-capacity spinel-type cathode materials, we identify cation to anion ratio in synthesis as a key parameter for tuning the structure continuously from a well-ordered spinel, through a partially ordered spinel, to rocksalt. We find that the varying degree of cation disorder modifies the voltage profile, rate capability, and charge-compensation mechanism in a rational and predictable way. Our results indicate that spinel-type order is most beneficial for achieving high-rate performance as long as the cooperative 8a to 16c phase transition is suppressed, while more rocksalt-like disorder facilitates O redox, which can increase capacity. Our findings reveal an important tuning handle for achieving high energy and power in the vast space of partially ordered cathode materials.

The most promising solid electrolytes for all-solid-state Li batteries are oxide and sulfide ceramics. Current ceramic solid electrolytes are brittle and lack the toughness to withstand the mechanical stresses of repeated charge and discharge cycles. Solid electrolytes are susceptible to crack propagation due to dendrite growth from Li metal anodes and to debonding processes at the cathode/electrolyte interface due to cyclic variations in the cathode lattice parameters. In this perspective, we argue that solutions to the mechanics challenges of all-solid-state batteries can be borrowed from the aerospace industry, which successfully overcame similar hurdles in the development of thermal barrier coatings of superalloy turbine blades. Their solution was to exploit ferroelastic and transformation toughening mechanisms to develop ceramics that can withstand cyclic stresses due to large variations in temperature. This perspective describes fundamental materials design principles with which to search for solid electrolytes that are ferroelastically toughened., Comment: 8 pages, 8 figures

Disordered rocksalt (DRX) cathodes have attracted interest due to their high capacity and compositional flexibility (e.g., Co-free chemistries). However, the sloping voltage profile and gradual capacity fade during cycling have hindered the widespread adoption of these materials. Simulations predict that fluorine substitution in DRX cathodes will improve their capacity, rate performance, and cyclability. In this study, we use a fluidized bed reactor to fluorinate a model Li-rich DRX composition (Li1.15Ni0.375Ti0.375Mo0.1O2, NTMO) to investigate how fluorine content impacts the cathode's structure and electrochemical performance. Instead of substituting O with F to form oxyfluoride phases, direct fluorination of DRX cathodes leads to the formation of LiF surface films, which improves the specific energy and capacity retention. This study demonstrates the feasibility of direct fluorination to improve the electrochemical performance of high-voltage cathodes by tuning the material's surface chemistry.

Current design rules for ion conducting polymers suggest that fast segmental dynamics and high solvation site density are important for high performance. In a family of imidazole side chain grafted siloxane polymer electrolytes containing LiTFSI, we conclude that while the presence of imidazole solvation sites promotes solubilization of Li+ containing salts, it is not necessary to substitute every monomer in the polymer design. Rather, optimization of Li+ conductivity relies on a balance between imidazole presence and the ability of the chains to rearrange locally to facilitate transport. Lowering the imidazole content in the ethane-imidazole series leads to a 10-fold increase in conductivity, while conductivity decreases for the phenyl-imidazole series due to differences in steric bulk. Normalizing conductivity by Tg reveals a threshold ligand density above which increased solvation sites do not improve conductivity, but below which the conduction gradually decreases. NMR spectroscopy shows the high temperature Li+ transport number increases slightly with increasing grafting density, from around 0.17 to 0.24. NMR T1ρ relaxation reveals that the Li+ ions are present in two environments with distinct dynamics within the polymer, matching X-ray scattering and PFG results which suggest ion aggregation exists in these polymers. These results emphasize the importance of local re-arrangements in facilitating ion transport at low solvation site density, confirming the role of dynamic percolation, and suggest that an optimum ligand density exists for improved charge transport.

Sodium (Na)-ion batteries are the most explored 'beyond-Li' battery systems, yet their energy densities are still largely limited by the positive electrode material. Na3FeF6 is a promising Earth-abundant containing electrode and operates through a conversion-type charge-discharge reaction associated with a high theoretical capacity (336 mA h g-1). In practice, however, only a third of this capacity is achieved during electrochemical cycling. In this study, we demonstrate a new rapid and environmentally-friendly assisted-microwave method for the preparation of Na3FeF6. A comprehensive understanding of charge-discharge processes and of the reactivity of the cycled electrode samples is achieved using a combination of electrochemical tests, synchrotron X-ray diffraction, 57Fe Mossbauer spectroscopy, X-ray photoelectron spectroscopy, magnetometry, and 23Na/19F solid-state nuclear magnetic resonance (NMR) complemented with first principles calculations of NMR properties. We find that the primary performance limitation of the Na3FeF6 electrode is the sluggish kinetics of the conversion reaction, while the methods employed for materials synthesis and electrode preparation do not have a significant impact on the conversion efficiency and reversibility. Our work confirms that Na3FeF6 undergoes conversion into NaF and Fe(s) nanoparticles. The latter are found to be prone to oxidation prior to ex situ measurements, thus necessitating a robust analysis of the stable phases (here, NaF) formed upon conversion.

Author(s): Zhong, P; Cai, Z; Zhang, Y; Giovine, R; Ouyang, B; Zeng, G; Chen, Y; Clement, R; Lun, Z; Ceder, G | Abstract: Using both computations and experiments, we demonstrate that the performance of Li-excess cation-disordered rocksalt cathodes can be improved by Mg substitution. Mg reduces the amount of Li in the compound that is strongly bound to F and thereby increases the capacity. This enables the use of fluorination as a tool to improve stability of the compounds without significant loss of capacity. Mg emerged as the most optimal substitution element from a systematic computational study aimed at identifying inactive doping elements with a strong enough bonding strength to fluorine to displace Li from the F environments. Our results also show that capacity can be traded for cycle life depending on whether Mg is substituted for Li or for the redox metal. This design strategy should be considered in fluorinated cathodes, which will facilitate the design of optimized disordered rocksalt oxyfluoride cathodes.

High-entropy (HE) ceramics, by analogy with HE metallic alloys, are an emerging class of solid solutions composed of a large number of species. These materials offer the benefit of large compositional flexibility and can be used in a wide variety of applications, including thermoelectrics, catalysts, superionic conductors and battery electrodes. We show here that the HE concept can lead to very substantial improvements in performance in battery cathodes. Among lithium-ion cathodes, cation-disordered rocksalt (DRX)-type materials are an ideal platform within which to design HE materials because of their demonstrated chemical flexibility. By comparing a group of DRX cathodes containing two, four or six transition metal (TM) species, we show that short-range order systematically decreases, whereas energy density and rate capability systematically increase, as more TM cation species are mixed together, despite the total metal content remaining fixed. A DRX cathode with six TM species achieves 307 mAh g−1 (955 Wh kg−1) at a low rate (20 mA g−1), and retains more than 170 mAh g−1 when cycling at a high rate of 2,000 mA g−1. To facilitate further design in this HE DRX space, we also present a compatibility analysis of 23 different TM ions, and successfully synthesize a phase-pure HE DRX compound containing 12 TM species as a proof of concept. High-entropy ceramics are solid solutions offering compositional flexibility and wide variety of applicability. High-entropy concepts are shown to lead to substantial performance improvement in cation-disordered rocksalt-type cathodes for Li-ion batteries.

Lithium-excess cation-disordered rocksalt oxides (DRXs) are a new class of high energy Li-ion cathode materials. A DRX cathode can deliver an exceptionally high capacity of >250 mA h g–1, implying ...

The rapid market growth of rechargeable batteries requires electrode materials that combine high power and energy and are made from earth-abundant elements. Here we show that combining a partial spinel-like cation order and substantial lithium excess enables both dense and fast energy storage. Cation overstoichiometry and the resulting partial order is used to eliminate the phase transitions typical of ordered spinels and enable a larger practical capacity, while lithium excess is synergistically used with fluorine substitution to create a high lithium mobility. With this strategy, we achieved specific energies greater than 1,100 Wh kg–1 and discharge rates up to 20 A g–1. Remarkably, the cathode materials thus obtained from inexpensive manganese present a rare case wherein an excellent rate capability coexists with a reversible oxygen redox activity. Our work shows the potential for designing cathode materials in the vast space between fully ordered and disordered compounds. There is an intensive search for high-performance cathode materials for rechargeable batteries. Here the authors report that oxyfluorides with partial spinel-like cation order, made from earth-abundant elements, display both exceptionally high energy and power.

Author(s): Schauser, Nicole S; Nikolaev, Andrei; Richardson, Peter M; Xie, Shuyi; Johnson, Keith; Susca, Ethan M; Wang, Hengbin; Seshadri, Ram; ClA©ment, RaphaA«le J.; Read de Alaniz, Javier; Segalman, Rachel A

Natrium super ionic conductor (NASICON) compounds form a rich and highly chemically tunable family of crystalline materials that are of widespread interest because they include exemplars with high ionic conductivity, low thermal expansion, and redox tunability. This makes them suitable candidates for applications ranging from solid-state batteries to nuclear waste storage materials. The key to an understanding of these properties, including the origins of effective cation transport and low, anisotropic (and sometimes negative) thermal expansion, lies in the lattice dynamics associated with specific details of the crystal structure. Here we closely examine the prototypical NASICON compound, NaZr

Funder: Powder Diffraction at the Australian Synchrotron, Funder: Australian Nuclear Science and Technology Organization, Funder: Engineering Physical Sciences Research Council, Funder: National Productivity Interest Fund, Funder: Center for Functional Nanomaterials, Funder: Brookhaven National Laboratory; Id: http://dx.doi.org/10.13039/100006231, Activation of oxygen redox represents a promising strategy to enhance the energy density of positive electrode materials in both lithium and sodium‐ion batteries. However, the large voltage hysteresis associated with oxidation of oxygen anions during the first charge represents a significant challenge. Here, P3‐type Na0.67Li0.2Mn0.8O2 is reinvestigated and a ribbon superlattice is identified for the first time in P3‐type materials. The ribbon superstructure is maintained over cycling with very minor unit cell volume changes in the bulk while Li ions migrate reversibly between the transition metal and Na layers at the atomic scale. In addition, a range of spectroscopic techniques reveal that a strongly hybridized Mn 3d–O 2p favors ligand‐to‐metal charge transfer, also described as a reductive coupling mechanism, to stabilize reversible oxygen redox. By preparing materials under three different synthetic conditions, the degree of ordering between Li and Mn is varied. The sample with the maximum cation ordering delivers the largest capacity regardless of the voltage windows applied. These findings highlight the importance of cationic ordering in the transition metal layers, which can be tuned by synthetic control to enhance anionic redox and hence energy density in rechargeable batteries.

Progress toward durable and energy-dense lithium-ion batteries has been hindered by instabilities at electrolyte-electrode interfaces, leading to poor cycling stability, and by safety concerns associated with energy-dense lithium metal anodes. Solid polymeric electrolytes (SPEs) can help mitigate these issues; however, the SPE conductivity is limited by sluggish polymer segmental dynamics. We overcome this limitation via zwitterionic SPEs that self-assemble into superionically conductive domains, permitting decoupling of ion motion and polymer segmental rearrangement. Although crystalline domains are conventionally detrimental to ion conduction in SPEs, we demonstrate that semicrystalline polymer electrolytes with labile ion-ion interactions and tailored ion sizes exhibit excellent lithium conductivity (1.6 mS/cm) and selectivity (t + ≈ 0.6-0.8). This new design paradigm for SPEs allows for simultaneous optimization of previously orthogonal properties, including conductivity, Li selectivity, mechanics, and processability.

Summary Mn-based Li-excess cation-disordered rocksalt (DRX) oxyfluorides are promising candidates for next-generation rechargeable battery cathodes owing to their large energy densities, the earth abundance, and low cost of Mn. In this work, we synthesized and electrochemically tested four representative compositions in the Li-Mn-O-F DRX chemical space with various Li and F content. While all compositions achieve higher than 200 mAh g−1 initial capacity and good cyclability, we show that the Li-site distribution plays a more important role than the metal-redox capacity in determining the initial capacity, whereas the metal-redox capacity is more closely related to the cyclability of the materials. We apply these insights and generate a capacity map of the Li-Mn-O-F chemical space, LixMn2-xO2-yFy (1.167 ≤ x ≤ 1.333, 0 ≤ y ≤ 0.667), which predicts both accessible Li capacity and Mn-redox capacity. This map allows the design of compounds that balance high capacity with good cyclability.

For lithium-ion rechargeable batteries to meet society's ever-growing demands in electrical energy storage, e.g. for the electrification of transportation, for portable electronics and for grid storage applications, novel electrode materials with a large charge storage capacity and a high energy density are needed. Over the last five years, several experimental and theoretical studies have demonstrated the feasibility of disordered rocksalt (DRX) cathodes, that is, lithium transition metal oxide cathodes with a crystalline rocksalt structure but with a disordered arrangement of lithium and transition metal on the cation lattice. We provide here an overview of the current understanding of DRX materials, in terms of their structural and compositional characteristics, as well as their electrochemical properties. We also present important considerations for the design of high performance DRX cathodes and suggest future research directions. Because no specific order is needed, DRX compounds can be composed of a wide variety of transition metal species, which can create long-term benefits for the lithium battery industry by making it less reliant on scarce and expensive raw materials. While some DRX compositions can simply be synthesized at high temperature to induce thermal cation disorder, other compositions require mechanochemical methods to induce a disordered arrangement of cation species. Cation disorder leads to unique lithium transport properties, small volume changes during charge–discharge cycling and sloping electrochemical profiles. Fluorine substitution for oxygen and the incorporation of high-valent d0 transition metals in the bulk DRX structure are two strategies used to increase the lithium content in the material, improve lithium percolation and to keep the valence of redox-active metal species low so that high transition metal redox capacity can be obtained. Short-range cation order, which is affected by thermal treatment, metal composition and fluorine substitution, has a significant impact on electrochemical performance. Moreover, fluorine substitution for oxygen improves long-term capacity retention by significantly reducing anion-based charge compensation mechanisms during charge. Fluorinated DRXs have recently demonstrated reversible capacities >300 mA h g−1 and extremely high energy densities approaching 1000 W h kg−1, holding promise for a nearly two-fold increase in the energy density of commercial lithium-ion batteries.

In cation-disordered rocksalt Li-ion cathode materials, an excess of Li with respect to the transition metal content is necessary for the creation of percolating pathways for Li transport. Because of the lower amount of redox-active transition metal, a substantial part of the charge transfer must occur via less reversible oxygen redox. Fluorination can be used to minimize this dependence on oxygen redox by increasing the amount of low-valent transition metal in the compound, but it adds complexity to materials design. Here, we investigate the feasibility of using computationally constructed phase diagrams to facilitate the search for optimal oxyfluorides. We use the phase diagram of LiF–Li3NbO4–NiO to identify Li1.13Ni0.57Nb0.3O1.75F0.25 and Li1.19Ni0.59Nb0.22O1.46F0.54 as two promising compositions and demonstrate that they can be successfully synthesized. These compounds exhibit significantly reduced hysteresis and higher energy density than the previously reported Li1.3Ni0.27Nb0.43O2 compound in this s...

Sodium (Na)-ion batteries are the most explored 'beyond-Li' battery systems, yet their energy densities are still largely limited by the positive electrode material. Na

This chapter gives a general introduction to NMR interactions in solids. More details on paramagnetic interactions of NMR, often dominating the spectra of paramagnetic solids, are then presented. A brief introduction to the first-principles calculations for NMR spectra of paramagnetic solids is also provided, which play an important role in spectral assignments.

Rechargeable solid-state sodium-ion batteries (SSSBs) hold great promise for safer and more energy-dense energy storage. However, the poor electrochemical stability between current sulfide-based solid electrolytes and high-voltage oxide cathodes has limited their long-term cycling performance and practicality. Here, we report the discovery of the ion conductor Na3-xY1-xZrxCl6 (NYZC) that is both electrochemically stable (up to 3.8 V vs. Na/Na+) and chemically compatible with oxide cathodes. Its high ionic conductivity of 6.6 × 10−5 S cm−1 at ambient temperature, several orders of magnitude higher than oxide coatings, is attributed to abundant Na vacancies and cooperative MCl6 rotation, resulting in an extremely low interfacial impedance. A SSSB comprising a NaCrO2 + NYZC composite cathode, Na3PS4 electrolyte, and Na-Sn anode exhibits an exceptional first-cycle Coulombic efficiency of 97.1% at room temperature and can cycle over 1000 cycles with 89.3% capacity retention at 40 °C. These findings highlight the immense potential of halides for SSSB applications., Rechargeable solid-state sodium-ion batteries hold great promise for safer and more energy-dense energy storage. Here, the authors show a new sodium-based halide, Na3-xY1-xZrxCl6, for sodium-all-solid-state batteries with enhanced ionic conductivity and long-term cycling stability.

Rechargeable batteries generate current through the transfer of electrons between paramagnetic and/or metallic electrode materials. Electron spin probes, such as electron paramagnetic resonance (EP...

Rechargeable solid-state sodium-ion batteries (SSSBs) hold great promise for safer and more energy-dense energy storage. However, the poor electrochemical stability between current sulfide-based solid electrolytes and high-voltage oxide cathodes has limited their long-term cycling performance and practicality. Here, we report the discovery of Na3-xY1-xZrxCl6 (NYZC) as an ion conductor that is both electrochemically stable (up to 3.8 V vs. Na/Na+) and chemically compatible with oxide cathodes. Its high ionic conductivity of 6.6 x 10-5 S cm-1 at ambient temperature, several orders of magnitude higher than oxide coatings, is attributed to abundant Na vacancies and cooperative MCl6 rotation, resulting in an extremely low interfacial impedance. A SSSB comprising a NaCrO2+NYZC composite cathode, Na3PS4 electrolyte, and Na-Sn anode exhibits an exceptional first-cycle Coulombic efficiency of 97.1% at room temperature and can cycle over 1000 cycles with 89.3% capacity retention at 40°C. These findings highlight the immense potential of halide ion conductors for SSSB applications.

The complete 31P NMR chemical shift tensors for 22 inorganic phosphates obtained from ab initio computation are found to correspond closely to experimentally obtained parameters. Further improvement was found when structures determined by diffraction were geometry optimized. Besides aiding in spectral assignment, the cases where correspondence is significantly improved upon geometry optimization point to the crystal structures requiring correction.

Fluorine substitution for oxygen in cation-disordered lithium-excess transition metal oxides (Li1+xTM1–xO2) used as lithium-ion cathodes was recently demonstrated to improve the reversibility of the processes taking place on charge and discharge by reducing the amount of oxygen loss on charge and preventing major structural rearrangements at high voltage. Yet, little is understood about how fluorine incorporates the oxide structure and impacts its electrochemical properties. Here, we use a combination of experimental (solid-state nuclear magnetic resonance (NMR) spectroscopy) and theoretical techniques (density functional theory (DFT) calculations and Monte Carlo simulations) to investigate the evolution of the local structure around fluorine and lithium and the oxidation state of redox-active nickel during charge and discharge of the Li1.15Ni0.45Ti0.3Mo0.1O1.85F0.15 (LNF15) cathode. We show that fluorine doping introduces short-range order in as-synthesized LNF15 by incorporating in lithium-rich sites wi...

There is an urgent need for low-cost, resource-friendly, high-energy-density cathode materials for lithium-ion batteries to satisfy the rapidly increasing need for electrical energy storage. To replace the nickel and cobalt, which are limited resources and are associated with safety problems, in current lithium-ion batteries, high-capacity cathodes based on manganese would be particularly desirable owing to the low cost and high abundance of the metal, and the intrinsic stability of the Mn4+ oxidation state. Here we present a strategy of combining high-valent cations and the partial substitution of fluorine for oxygen in a disordered-rocksalt structure to incorporate the reversible Mn2+/Mn4+ double redox couple into lithium-excess cathode materials. The lithium-rich cathodes thus produced have high capacity and energy density. The use of the Mn2+/Mn4+ redox reduces oxygen redox activity, thereby stabilizing the materials, and opens up new opportunities for the design of high-performance manganese-rich cathodes for advanced lithium-ion batteries.

The discovery of facile Li transport in disordered, Li-excess rocksalt materials has opened a vast new chemical space for the development of high energy density, low cost Li-ion cathodes. We develop a strategy for obtaining optimized compositions within this class of materials, exhibiting high capacity and energy density as well as good reversibility, by using a combination of low-valence transition metal redox and a high-valence redox active charge compensator, as well as fluorine substitution for oxygen. Furthermore, we identify a new constraint on high-performance compositions by demonstrating the necessity of excess Li capacity as a means of counteracting high-voltage tetrahedral Li formation, Li-binding by fluorine and the associated irreversibility. Specifically, we demonstrate that 10–12% of Li capacity is lost due to tetrahedral Li formation, and 0.4–0.8 Li per F dopant is made inaccessible at moderate voltages due to Li–F binding. We demonstrate the success of this strategy by realizing a series of high-performance disordered oxyfluoride cathode materials based on Mn2+/4+ and V4+/5+ redox.

To design a synthesis route for energy storage materials, the phase diagram is a useful starting point. However, non-equilibrium intermediates often appear during synthesis—which are difficult to anticipate and often persist as impurities in the final reaction product. In addition, intermediate phases may template the morphology of particles. Thus, being able to rationalize and predict which metastable intermediates form during solid-state reactions is crucial towards developing rational frameworks in which to create predictive ceramic synthesis approaches. Guided by real-time in situ synchrotron observations of materials formation, we develop a new theory to model the reactions between ceramic precursors to form NaxMO2 layered oxides (M = Co, Mn), which are important cathode materials for Na-batteries. These layered oxides form in two polytypes: a two-layer (P2) stacking, and a three-layer (O3 or P3) stacking. Even though phase diagrams determine that P2 is the stable phase at Na0.66CoO2 composition, synthesis using a nominal 0.33 Na2O2 + CoO precursor mixture is observed to first form the O3-NaCoO2. The reaction then proceeds sequentially through non-equilibrium O3’and P3 phases, with the equilibrium P2-Na0.66CoO2 only obtained after long time at high temperature. This raises the fundamental question—how do thermodynamic driving forces and kinetic mechanisms conspire to create phases that are not thermodynamic stable, and why can some phases, which are thermodynamically favored at all temperatures, only be formed after long times at high temperature? We show that the first phase to form from the precursors is actually the compound which consumes the most reaction energy, irrespective of whether this compound is at the target stoichiometry. After this initial compound forms, a combination of fast topotactic reactions and slow nucleation and growth processes slowly bring the system to the equilibrium phase. Based on this insight we can now predict how different precursors change the reaction pathway, driving the crystallization pathway through different intermediates. As an example, we show how P2-Na0.66MnO2 can be formed through very different reaction pathways by changing the precursors. This rationalization of the first phase to form creates a valuable design handle by which reaction paths can be tailored to go through, or circumvent, specific non-equilibrium intermediates. Our combined computational and experimental approach offers a predictive framework for the synthesis design of new energy materials.

Author(s): Ghosh, Subham; Barman, Nabadyuti; Gonzalez-Correa, Eliovardo; Mazumder, Madhulika; Zaveri, Aryan; Giovine, Raynald; Manche, Alexis; Pati, Swapan K; Clement, Raphaele J; Senguttuvan, Premkumar