Bhaskar, A.

Ehrenberg, H.

Eichel, R.A.

Jakes, P.

Nikolowski, K.

Yavuz, M.

Yavuz, N.K.

Yavuz, N. K.

Eichel, R. A.

KITopen

KIT – University of the State of Baden-Wuerttemberg and National Research Center of the Helmholtz Association Comparison of LiNi0.5Mn1.5O4 and LiNi0.5-2xRuxMn1.5O4 Spinel Materials as High Voltage Cathodes for Lithium-ion Batteries Nilüfer Kızıltaş Yavuz[a], Aiswarya Bhaskar[a], Murat Yavuz[a, b], Kristian Nikolowski[a, b], Peter Jakes[c],           Rüdiger-A. Eichel[c], Helmut Ehrenberg[a, b] [a]Karlsruhe Institute of Technology (KIT), Institute for Applied Materials (IAM)-Energy Storage Systems (ESS) [b]Helmholtz Institute of Ulm (HIU) Electrochemical Energy Storage, Karlsruhe Institute of Technology (KIT),  Herman-von-Helmholtz Platz 1, 76344 Eggenstein-Leopoldshafen, Germany [c]Forschungszentrum Jülich, Institute of Energy and Climate Research, Fundamental Electrochemistry (IEK-9) Wilhelm-Johnen Straße, D-52425 Jülich, Germany  Experimental Details Synthesis:  LiNi0.5Mn1.5O4 and LiNi0.4Ru0.05Mn1.5O4 materials were synthesized by citric acid-asisted sol-gel method. Metal acetate precursors were dissolved in a citric acid and Ethylene glycol (1:4) mixture by heating at 90oC. Later the solution was heated up to 180oC to evaporate the excess ethylene glycol from the mixture. The obtained gel was precalcined at 400oC for 5 h to remove the carbon. The precursor is then preannealed at 600oC for 24h and post annealed at 800oC and 1000oC to get the final products. Characterization:  Ex situ and in situ X-ray diffraction experiments were carried out at the High Resolution Powder Diffraction beamline (P02.1) at PETRA-III, DESY, using synchrotron radiation with an energy of 60 keV (λ=0.207260 Å). The morphology of the particles was studied with Zeiss Supra 55 SEM (Scanning Electron Microscope) with primary energy of 15 keV and in-lens detector. Electrochemical Experiments:  The cathode mixture was prepared by mixing 80% (w/w) of the active material with 10% (w/w) of Super C 65 carbon (TIMCAL) and 10% (w/w) of polyvinylidene fluoride (PVdF) binder. The mixture was coated on Aluminium foil, dried, punched out and pressed to obtain electrodes of 1.2 cm diameter. The obtained electrodes were electrochemically characterized with a VMP3 potentiostat. References  [1] A. Bhaskar, N. N. Bramnik, A. Senyshyn, H. Fuess, H. Ehrenberg, J. Electrochem. Soc., 157 (6), A689-A695, 2010  [2] H. Wang, H. Xia, M. O. Lai, L. Lu, Electrochem. Commun., 11, 1539-1542, 2009  [3] Q. Zhong, A. Bonakdarpour, J.R. Dahn, J., Electrochem. Soc., 144,205, 1997  [4] H. Matsumoto, D. Murakami, T. Shimura, S.I. Hashimoto, H. Iwahara, J. Electroceram., 7, 107–111, 2001  [5] H. Wang, T. A. Tan, P. Yang, M. O. Lai, L. Lu, J. Phys. Chem. C, 115, 6102–6110, 2011  Conclusion  LiNi0.5Mn1.5O4  contains small amounts of LixNi1-xO4 impurity which has been vanished after Ru-doping.   The thickness (mass loading) of the cathode materials on Al-foil plays an important role especially at high C-rate.   The amount of Mn3+ ions increases with the increase in annealing temperature because of the oxygen loss from the crystal lattice.  The samples synthesized at 1000oC  have better capacity retention than the ones synthesized at 800oC after 300 cycles (LiNi0.5Mn1.5O4 has 79,5% and Ru-doped has 83%).  Ru-doped sample synthesized at 1000oC exhibits a higher capacity than the undoped sample even though a larger 4 V electrochemical activity is observed which corresponds to the existence of Mn3+.    An intermediate phase (2nd main phase (𝐹𝑑3𝑚)) appears at ~4.7 V for both materials annealed at 1000oC, on both charging & discharging processes where Ni2+/ Ni4+ electrochemical reaction takes place [1]. Introduction The spinel LiNi0.5Mn1.5O4 cathode shows impressive electrochemical performance like large reversible capacity at a high operating voltage around 4.7 V which makes it a promising and suitable cathode material for high energy battery applications [1]. Moreover, in this material all the Mn ions are expected to be in its tetravalent form. Nevertheless, electrochemical performance at high rates still needs to be improved to meet the required power density [1-2]. In the ideal LiNi0.5Mn1.5O4 spinel, no Mn ions exist in its trivalent state, which is well-known as Jahn-Teller ion causing structural instability. However, usually a small amount of Mn3+ remains in the compound as a result of oxygen deficiency after the high temperature synthesis process [3].  It has been reported that the 4d orbitals with a larger radius of the second row transition metal ions (e.g. Ru4+) overlapping with the 2p orbitals of oxygen favors wider conduction bands leading to better electrical conductivity [4]. Also the ionic radii of Ru4+ (0.62 Å) and Ni2+ (0.69 Å) are similar which allows the Ru4+ cation to substitute Ni2+. It has been reported that the doping of Ru improves the rate capability and also the high-rate cycling stability of LiNi0.5Mn1.5O4 [2, 5]. In the present work, LiNi0.5Mn1.5O4 and Ru-doped LiNi0.5-2xRuxMn1.5O4 (x=0.05), synthesized via Pechini method using metal acetate precursors have been investigated.  Energy Storage Systems (ESS) LiNi0.5Mn1.5O4-800oC LiNi0.5Mn1.5O4-1000oC 2 4 6 8 10 12 14   Intensity (arb. units)LiNi0.5Mn1.5O4_800oC Yobs Ycalc Yobs-Ycalc Bragg positiona = 8.1724(1)Å  ~1% LixNi1-xO 2 4 6 8 10 12 14  Intensity (arb. units)LiNi0.5Mn1.5O4_1000oC Yobs Ycalc Yobs-Ycalc Bragg positiona = 8.1789(1)Å  ~5% LixNi1-xO  Results: Powder  Characterization  LiNi0.4Ru0.05Mn1.5O4-800oC LiNi0.4Ru0.05Mn1.5O4-1000oC 2 4 6 8 10 12 14  Intensity (arb. units) Yobs Ycalc Yobs-Ycalc Bragg positionLiNi0.4Ru0.05Mn1.5O4_800oCa = 8.18314(4)Å 2 4 6 8 10 12 14    Intensity (arb. units)LiNi0.4Ru0.05Mn1.5O4_1000oC Yobs Ycalc Yobs-Ycalc Bragg position a = 8.18885(4) Å LiNi0.5Mn1.5O4 800oC 1000oC LiNi0.4 Ru0.05Mn1.5O4 800oC 1000oC   The amount of impurity phase (LixNi1-xO) increases with increasing  synthesis temperature for LiNi0.5Mn1.5O4 which vanishes after Ru-doping for both temperatures.   The particles are not  well shaped  for both materials (LiNi0.5Mn1.5O4  and LiNi0.4Ru0.05Mn1.5O4) synthesized at 800oC but  the materials synthesized at 1000oC have higher crystallinity. Results: Electrochemical Investigations 0 5 10 15 20 25 300102030405060708090100110120130140150Charging with C/2 LiNi0.5Mn1.5O4@800oC_120 µm LiNi0.5Mn1.5O4@1000oC_120 µm LiNi0.4Ru0.05Mn1.5O4@800oC_120 µm LiNi0.4Ru0.05Mn1.5O4@1000oC_120 µmC/220C10C5CCC/2   discharge capacity [mAh/g]cycle number0 5 10 15 20 25 300102030405060708090100110120130140150 LiNi0.5Mn1.5O4@800oC_300 µm LiNi0.5Mn1.5O4@1000oC_300 µm LiNi0.4Ru0.05Mn1.5O4@800oC_300 µm LiNi0.4Ru0.05Mn1.5O4@1000oC_300 µm  discharge capacity [mAh/g]cycle numberC/2 C 5C 10C 20C C/2Charging with C/2120 µm wet thickness (1,891 mg/cm2) 300 µm wet thickness (4,452 mg/cm2)   The electrode mass loadings effect the capacity especially at high C-rates for LiNi0.4Ru0.05Mn1.5O4  and  LiNi0.5Mn1.5O4 materials,  synthesized at both  800oC and  1000oC. Results: In situ diffraction experiments 0 25 50 75 100 125 150 175 200 225 250 275 3000102030405060708090100110120130140150 LiNi0.5Mn1.5O4 @1000oC LiNi0.4Ru0.05Mn1.5O4 @800oC LiNi0.5Mn1.5O4 @800oC  LiNi0.4Ru0.05Mn1.5O4 @1000oCdischarge capacity [mAh/g]Charging&Discharging  with C/2cycle number  Even though  LiNi0.4Ru0.05Mn1.5O4  @1000oC  (blue curve) has larger 4V electrochemical activity  than LiNi0.5Mn1.5O4 @ 1000oC (red curve)  which corresponds to the Mn3+/Mn4+electrochemical reaction, it has better capacity and cycling stability.  0 20 40 60 80 100 120 1403,43,53,63,73,83,94,04,14,24,34,44,54,64,74,84,95,03rd discharge LiNi0.5Mn1.5O4 @800oC LiNi0.5Mn1.5O4 @1000oC LiNi0.4Ru0.05Mn1.5O4 @800oC LiNi0.4Ru0.05Mn1.5O4 @1000oCEwe vs. Li/Li+[V]Discharge capacity [mAh g-1]0 2 4 6 8 10 12 1401000020000300004000050000600007000080000900004,0 4,5 5,0 5,5 6,0 6,5 7,0 7,5 8,0 8,5 9,0 9,5 10,0region 4.7Vregion 4.7VLiNi0.5Mn1.5O4@1000oC  intensity(a.u)initial3.5Vdischarging5Vcharging3V     Al  Al  Al  Al 1st cycle of LiNi0.5Mn1.5O4 @1000oC at C/2 rate   1st cycle of LiNi0.4Ru0.05Mn1.5O4 @1000oC at C/2 rate  0 2 4 6 8 10 12 1401000020000300004000050000600007000080000900004,0 4,5 5,0 5,5 6,0 6,5 7,0 7,5 8,0 8,5 9,0 9,5 10,0LiNi0.4Ru0.05Mn1.5O4@1000oC3.5V3V5Vregion 4.7Vregion 4.7V  initialchargingdischargingintensity (a.u)   Al  Al  Al  Al 0,0 0,2 0,4 0,6 0,8 1,07,967,988,008,028,048,068,088,108,128,148,168,188,202nd main phase1st main phasetwo main phases charging discharging  one main phase charging discharginga-parameter/Åx (Li)0,0 0,2 0,4 0,6 0,8 1,07,967,988,008,028,048,068,088,108,128,148,168,188,20   a-parameter/Å2nd main phase1st main phasetwo main phases charging dischargingx (Li)one main phase charging discharging LiNi0.4Ru0.05Mn1.5O4 @1000oC  LiNi0.5Mn1.5O4 @1000oC 

Comparison of LiNi₀̣₅Mn₁̣₅O₄ and LiNi₀̣₅₋₂ₓRuₓMn₁̣₅O₄ spinel materials as high voltage cathodes for lithium-ion batteries

https://publikationen.bibliothek.kit.edu/220091850/3816308

Comparison of LiNi₀̣₅Mn₁̣₅O₄ and LiNi₀̣₅₋₂ₓRuₓMn₁̣₅O₄ spinel materials as high voltage cathodes for lithium-ion batteries

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