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Devendrasinh Darbar
Department of Electrical and Computer Engineering, Tennessee Technological University, Cookeville, TN 38505, USA

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Journal article
Published: 02 June 2021 in Electrochem
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In this work, we report a sol-gel synthesis-based Zn-doped Na0.6Fe0.5Mn0.5O2 (NFM) cathode and understand the effect of Zn doping on the crystal structure and electrochemical performances such as discharge capacity and rate capability. Detailed X-Ray diffraction (XRD) pattern analysis indicated a decrease in the Na-layer thickness with Zn doping. Small amount of Zn2+ dopant (i.e., 2 at.%) slightly improved cycling stability, reversibility, and rate performances at higher discharge current rates. For example, at 1 C-rate (1 C = 260 mAh/g), the Zn2+-doped cathode retained a stable reversible capacity of 72 mAh/g, which was ~16% greater than that of NFM (62 mAh/g) and showed a minor improvement in the capacity retention of 60% compared to 55% for the pristine NFM after 65 cycles. Slight improvement in the electrochemical performance for the Zn-doped cathode can be attributed to a better structural stability, which prevented the initial phase transition and showed the presence of electrochemical active Fe3+/4+ even after 10 cycles compared to NFM.

ACS Style

Devendrasinh Darbar; M. Reddy; Indranil Bhattacharya. Understanding the Effect of Zn Doping on Stability of Cobalt-Free P2-Na0.60Fe0.5Mn0.5O2 Cathode for Sodium Ion Batteries. Electrochem 2021, 2, 323 -334.

AMA Style

Devendrasinh Darbar, M. Reddy, Indranil Bhattacharya. Understanding the Effect of Zn Doping on Stability of Cobalt-Free P2-Na0.60Fe0.5Mn0.5O2 Cathode for Sodium Ion Batteries. Electrochem. 2021; 2 (2):323-334.

Chicago/Turabian Style

Devendrasinh Darbar; M. Reddy; Indranil Bhattacharya. 2021. "Understanding the Effect of Zn Doping on Stability of Cobalt-Free P2-Na0.60Fe0.5Mn0.5O2 Cathode for Sodium Ion Batteries." Electrochem 2, no. 2: 323-334.

Journal article
Published: 17 March 2021 in Electrochimica Acta
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Here, we report a wet synthesis-based titanium doping strategy to improve the structural stability and electrochemical performances, such as cycling stability and rate capability, of P2-type Na0.67Fe0.5Mn0.5O2 layered oxide cathodes. Through Ti4+ doping aimed at replacing some of the Mn and Fe atoms in the crystal structure, effective mitigation of the Jahn Teller distortion caused by active Mn3+ before charging and Fe4+ after charging was achieved. X-ray diffraction (XRD), Raman spectroscopy, Electrochemical Impedance Spectroscopy (EIS) and Mössbauer spectroscopy were used to investigate the effects of the Ti4+ dopant before and after cycling. It was observed that Ti4+ doping increased the Na layer thickness, minimized the lattice volume strain, showed better structural stability, minimally decreased Fe migration to the Na layer, and lowered charge transfer resistance in these P2-type cathodes. Overall, our reported synthesis methodology and electrochemical characterizations highlight the feasibility of Ti doping in sodium layered oxide P2-type cathodes.

ACS Style

Devendrasinh Darbar; Nitin Muralidharan; Raphaël P. Hermann; Jagjit Nanda; Indranil Bhattacharya. Evaluation of electrochemical performance and redox activity of Fe in Ti doped layered P2-Na0.67Mn0.5Fe0.5O2 cathode for sodium ion batteries. Electrochimica Acta 2021, 380, 138156 .

AMA Style

Devendrasinh Darbar, Nitin Muralidharan, Raphaël P. Hermann, Jagjit Nanda, Indranil Bhattacharya. Evaluation of electrochemical performance and redox activity of Fe in Ti doped layered P2-Na0.67Mn0.5Fe0.5O2 cathode for sodium ion batteries. Electrochimica Acta. 2021; 380 ():138156.

Chicago/Turabian Style

Devendrasinh Darbar; Nitin Muralidharan; Raphaël P. Hermann; Jagjit Nanda; Indranil Bhattacharya. 2021. "Evaluation of electrochemical performance and redox activity of Fe in Ti doped layered P2-Na0.67Mn0.5Fe0.5O2 cathode for sodium ion batteries." Electrochimica Acta 380, no. : 138156.

Research article
Published: 02 March 2020 in Nano Letters
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Structural transformations near surfaces of solid-state materials underpin functional mechanisms of a broad range of applications including catalysis, memory, and energy storage. It has been a long-standing notion that the outmost free surfaces, accompanied by broken translational symmetry and altered atomic configurations, are usually the birthplace for structural transformations. Here, in a layered oxide cathode for Li-ion batteries, we for the first time observe the incipient state of the well documented layered-to-spinel-like structural transformation, which is surprisingly initiated from subsurface layer, rather than the very surface. Coupling atomic level scanning transmission electron microscopy imaging with electron energy loss spectroscopy, we discover that the reconstructed subsurfaces, featuring a mix of discrete patches of layered and spinel-like structures, are associated with selective atomic species partition and consequent nanoscale non-uniform composition gradient distribution at the subsurface. Our findings provide fundamental insights on atomic-scale mechanisms of structural transformation in layered cathodes.

ACS Style

Linze Li; Ethan C. Self; Devendrasinh Darbar; Lianfeng Zou; Indranil Bhattacharya; Donghai Wang; Jagjit Nanda; Chongmin Wang. Hidden Subsurface Reconstruction and Its Atomic Origins in Layered Oxide Cathodes. Nano Letters 2020, 20, 2756 -2762.

AMA Style

Linze Li, Ethan C. Self, Devendrasinh Darbar, Lianfeng Zou, Indranil Bhattacharya, Donghai Wang, Jagjit Nanda, Chongmin Wang. Hidden Subsurface Reconstruction and Its Atomic Origins in Layered Oxide Cathodes. Nano Letters. 2020; 20 (4):2756-2762.

Chicago/Turabian Style

Linze Li; Ethan C. Self; Devendrasinh Darbar; Lianfeng Zou; Indranil Bhattacharya; Donghai Wang; Jagjit Nanda; Chongmin Wang. 2020. "Hidden Subsurface Reconstruction and Its Atomic Origins in Layered Oxide Cathodes." Nano Letters 20, no. 4: 2756-2762.

Research article
Published: 24 September 2019 in ACS Energy Letters
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Cobalt-free layered oxides have emerged as promising candidates for next-generation cathodes for lithium-ion batteries. However, implementation of these materials has been hindered by their low rate capability, structural instability, and rapid capacity decay during cycling. Recent studies have shown that introducing cation dopants into layered oxides can strongly improve their electrochemical properties, but the underlying atomic-scale mechanisms remain elusive. In this work, we use a combination of atomic-resolution scanning transmission electron microscopy and first principle calculations to reveal the microscopic origin of enhanced electrochemical properties in LiNi0.5Mn0.5O2 doped with ∼1 at % Mo. Our results indicate that the Mo dopant hinders Li+/Ni2+ cation mixing and suppresses detrimental phase transformations near the particle surface and at intragranular grain boundaries, which enhances the cathode’s reversible capacity and cycling stability. Overall, this work provides important insights on how cation doping affects the structure and electrochemical properties of layered oxide cathodes.

ACS Style

Linze Li; Jianguo Yu; Devendrasinh Darbar; Ethan C. Self; Donghai Wang; Jagjit Nanda; Indranil Bhattacharya; Chongmin Wang. Atomic-Scale Mechanisms of Enhanced Electrochemical Properties of Mo-Doped Co-Free Layered Oxide Cathodes for Lithium-Ion Batteries. ACS Energy Letters 2019, 4, 2540 -2546.

AMA Style

Linze Li, Jianguo Yu, Devendrasinh Darbar, Ethan C. Self, Donghai Wang, Jagjit Nanda, Indranil Bhattacharya, Chongmin Wang. Atomic-Scale Mechanisms of Enhanced Electrochemical Properties of Mo-Doped Co-Free Layered Oxide Cathodes for Lithium-Ion Batteries. ACS Energy Letters. 2019; 4 (10):2540-2546.

Chicago/Turabian Style

Linze Li; Jianguo Yu; Devendrasinh Darbar; Ethan C. Self; Donghai Wang; Jagjit Nanda; Indranil Bhattacharya; Chongmin Wang. 2019. "Atomic-Scale Mechanisms of Enhanced Electrochemical Properties of Mo-Doped Co-Free Layered Oxide Cathodes for Lithium-Ion Batteries." ACS Energy Letters 4, no. 10: 2540-2546.

Journal article
Published: 01 April 2018 in Ceramics International
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ACS Style

Devendrasinh Darbar; M.R. Anilkumar; Vijayaraghavan Rajagopalan; Indranil Bhattacharya; Hendry Izaac Elim; T. Ramakrishnappa; F.I. Ezema; Rajan Jose; M.V. Reddy. Studies on spinel cobaltites, MCo2O4 (M = Mn, Zn, Fe, Ni and Co) and their functional properties. Ceramics International 2018, 44, 4630 -4639.

AMA Style

Devendrasinh Darbar, M.R. Anilkumar, Vijayaraghavan Rajagopalan, Indranil Bhattacharya, Hendry Izaac Elim, T. Ramakrishnappa, F.I. Ezema, Rajan Jose, M.V. Reddy. Studies on spinel cobaltites, MCo2O4 (M = Mn, Zn, Fe, Ni and Co) and their functional properties. Ceramics International. 2018; 44 (5):4630-4639.

Chicago/Turabian Style

Devendrasinh Darbar; M.R. Anilkumar; Vijayaraghavan Rajagopalan; Indranil Bhattacharya; Hendry Izaac Elim; T. Ramakrishnappa; F.I. Ezema; Rajan Jose; M.V. Reddy. 2018. "Studies on spinel cobaltites, MCo2O4 (M = Mn, Zn, Fe, Ni and Co) and their functional properties." Ceramics International 44, no. 5: 4630-4639.

Journal article
Published: 01 January 2016 in Materials Research Bulletin
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ACS Style

Devendrasinh Darbar; M.V. Reddy; S. Sundarrajan; R. Pattabiraman; S. Ramakrishna; B.V.R. Chowdari. Anodic electrochemical performances of MgCo 2 O 4 synthesized by oxalate decomposition method and electrospinning technique for Li-ion battery application. Materials Research Bulletin 2016, 73, 369 -376.

AMA Style

Devendrasinh Darbar, M.V. Reddy, S. Sundarrajan, R. Pattabiraman, S. Ramakrishna, B.V.R. Chowdari. Anodic electrochemical performances of MgCo 2 O 4 synthesized by oxalate decomposition method and electrospinning technique for Li-ion battery application. Materials Research Bulletin. 2016; 73 ():369-376.

Chicago/Turabian Style

Devendrasinh Darbar; M.V. Reddy; S. Sundarrajan; R. Pattabiraman; S. Ramakrishna; B.V.R. Chowdari. 2016. "Anodic electrochemical performances of MgCo 2 O 4 synthesized by oxalate decomposition method and electrospinning technique for Li-ion battery application." Materials Research Bulletin 73, no. : 369-376.