Electrochemical Performance of Li-and Mn-Rich Cathodes in Full

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Electrochemical Performance of Li and Mn-rich Cathodes in Full Cells with Pre-lithiated Graphite Negative Electrodes Prasant Kumar Nayak, Tirupathi Rao Penki, Boris Markovsky, and Doron Aurbach ACS Energy Lett., Just Accepted Manuscript • DOI: 10.1021/acsenergylett.7b00007 • Publication Date (Web): 27 Jan 2017 Downloaded from http://pubs.acs.org on January 29, 2017

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ACS Energy Letters

Electrochemical Performance of Li and Mn-rich Cathodes in Full Cells with Prelithiated Graphite Negative Electrodes

Prasant Kumar Nayak, Tirupathi Rao Penki, Boris Markovsky, Doron Aurbach* Department of Chemistry, Bar-Ilan University, Ramat-Gan, 5290002, Israel *E-mail: [email protected]

Abstract Li and Mn-rich layered oxide cathodes are known to suffer from capacity fading and average discharge voltage decay upon cycling. In the present study, the improved cycling stability of a Li and Mn–rich cathode Li1.2Ni0.27Mn0.40Co0.13O2 in full cells is reported. The electrochemical

performance

of

the

Li

and

Mn-rich

cathodes

comprising

Li1.2Ni0.13Mn0.54Co0.13O2 and Li1.2Ni0.27Mn0.40Co0.13O2 was tested in Li-ion full cells with graphite as anode material at 30 oC. The full cells with Li1.2Ni0.13Mn0.54Co0.13O2 cathodes exhibited initially high capacities of about 250 mAh g1, which fades rapidly to 130 mAh g-1 after 120 cycles at C/5 rate. However, full cells comprising Li1.2Ni0.27Mn0.40Co0.13O2 cathodes exhibited an initial capacity of about 190 mAh g-1 with very stable cycle-life, i.e., about 185 mAh g-1 after 150 cycles at C/5 rate. Also, these cathodes possess higher rate capability as compared to full cells comprising Li1.2Ni0.13Mn0.54Co0.13O2 cathodes. Thus, the electrochemical performance of Li1.2Ni0.27Mn0.40Co0.13O2 cathodes in full cells with prelithiated graphite anodes is promising for practical high energy density Li-ion batteries. These results indicate the positive influence of higher Ni content in Li and Mn-rich cathodes for better electrochemical performance in practical Li-ion batteries.

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Li and Mn-rich Li1+xMn0.33+yNi0.33-zCo0.33-wO2 layered oxides cathodes are known to exhibit high specific capacities ≥ 250 mAh g-1 upon polarization to voltage higher than 4.5 V in the first cycles.1-8 These layered oxides are considered as advanced cathodes, because of their high capacities which can lead to an increase in the energy density of current Li-ion batteries and can be promoted for electric vehicles (EVs) applications. These cathodes need to be cycled to above 4.5 V in the 1st cycle in order to activate the inactive Li2MnO3 to achieve high specific capacities. However, these cathodes suffer from capacity fading, average discharge voltage decay upon cycling and poor rate performance. The electrochemical performance of these cathodes depends on their composition, morphology, valence of transition metals (Mn, Ni, Co), method of preparation, annealing temperature etc.913

Doping the basic 5 elements (Li-Mn-Ni-Co-O) systems by cations such as Na, Mg, Al, Zr,

Sn etc (i.e. replacing a few percent of Mn cations by these metal cations) were found to be useful in enhancing the cycling stability as well as in improved rate performance of these cathode materials.14-19 Recently, it was shown that substitution of Mn with Ni in these Li and Mn-rich cathodes results in a decrease in specific capacity in Li-ion half cells, but remarkably improves their electrochemical cycling stability upon cycling.20 This finding means that the fine tuning in the composition of these Li and Mn-rich Li1+xMn0.33+yNi0.33-zCo0.33-wO2 compounds, namely, optimizing the amount of nickel (yet maintaining the stoichiometry of Li and Mn above 1 and 0.33 respectively) can help in their stabilization and performance improvement. As a follow-up of that discovery,20 it is important to test these cathodes in full cells in order to ensure their better electrochemical performance and hence to validate their potential practical importance, what was not performed yet. From our previous experience on performance of full cells, we have learnt that a partial pre-lithiation of graphite electrodes is essential for testing reliably full cells comprising balanced electrodes.21 Pre-lithiation enables to have enough active Li in full cells that compensate for the loss of Li ions in irreversible


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side reactions during the first cycles, before passivation of the graphite electrodes is fully developed. In the present study, the electrochemical performance of Li and Mn-rich cathodes such as Li1.2Ni0.13Mn0.54Co0.13O2 and Li1.2Ni0.27Mn0.40Co0.13O2 was tested in Li-ion full cells with pre-lithiated graphite as an anode material. We show herein that Li1.2Ni0.27Mn0.40Co0.13O2 exhibited lower capacity, compared to Li1.2Ni0.13Mn0.54Co0.13O2 as was observed in half cells testing (vs. Li metal anodes).20 However, the gain in stability due to the higher presence of Ni was impressive. The charge-discharge cycling of full cells comprising Li1.2Ni0.13Mn0.54Co0.13O2 and Li1.2Ni0.27Mn0.40Co0.13O2 cathodes with pre-lithiated graphite anodes was tested at 25 mA g-1 (C/10) rate for initial 2 cycles followed by subsequent cycling at C/5 rate. The voltage profiles of the 1st charge-discharge cycle are shown in Fig. 1a. Two plateaus are observed during the charge for both full cells. The first plateau below 4.4 V corresponds to the extraction of Li+ ions from the active LiMO2 phase. The long plateau above 4.4 V for both cathode materials corresponds to the activation of the Li2MnO3 component, which involves extraction of Li+ ions and oxygen release. The first total charging specific capacities were found to be 342 and 320 mAh g-1 for Li1.2Ni0.13Mn0.54Co0.13O2 and Li1.2Ni0.27Mn0.40Co0.13O2 cathodes, respectively. The first discharge capacities were found to be 272 and 199 mAh g-1 for Li1.2Ni0.13Mn0.54Co0.13O2 and Li1.2Ni0.27Mn0.40Co0.13O2, respectively, when cycled at C/10 rate (25 mA g-1). Thus, a higher specific discharge capacity was obtained for Li1.2Ni0.13Mn0.54Co0.13O2. This can be due to the redox activity of higher Mn content at low potential around 3.0 V in Li1.2Ni0.13Mn0.54Co0.13O2. The cycling stability of these two cathodes was tested at C/5 from the 3rd cycle, which is shown in Fig. 1b and 1c. It can be seen that although Li1.2Ni0.13Mn0.54Co0.13O2 exhibited initial high capacities, the capacity gradually decreased upon cycling and a specific capacity of about 130 mAh g-1 was obtained after 120


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cycles, thus retaining about 54 % of the initial capacity. This is usually observed in case of Li and Mn-rich cathodes due to a structural layered-to-spinel transformation upon cycling to 4.8

(b)

4.8

(a)

Potential / V

4.4 1st cycle

4.4 (i) Li1.2Ni0.13Mn0.54Co0.13O2 / graphite

4.0

(ii) Li1.2Ni0.27Mn0.40Co0.13O2 / graphite

3.2 2.8 2.4 2.0 0

40

80

120

160

200

240

280

320

3rd 50th 100th

4.0 3.6 3.2 2.8 2.4

3.6

Potential / V

Cell potential / V

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

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360

-1

Specific capacity / mAh g

2.0 4.8 4.4 4.0 3.6 3.2 2.8 2.4 2.0

(c) 3rd 50th 100th

0

40

80 120 160 200 240 -1 Specific capacity / mAh g

280

Fig. 1 (a) Voltage profiles measured during the first galvanostatic charge-discharge cycle of full cells comprising Li1.2Ni0.13Mn0.54Co0.13O2 and Li1.2Ni0.27Mn0.40Co0.13O2 as indicated and pre-lithiated graphite at C/10 rate. (b, c) Voltage profiles of subsequent galvanostatic chargeand discharge cycles of full cells comprising Li1.2Ni0.13Mn0.54Co0.13O2 Li1.2Ni0.27Mn0.40Co0.13O2 (respectively) and pre-lithiated graphite anodes at C/5 rate after initial two cycles at C/10 rate. The electrolyte solutions comprised EC-DMC (1:1) and 1M LiPF6. potentials above 4.5 V,7,8 which is a major drawback in commercialization of these cathodes in Li-ion batteries. On the other hand, Li1.2Ni0.27Mn0.40Co0.13O2 exhibited a stable capacity of about 200 mAh g-1 for 100 cycles, which then decreased to a value of 185 mAh g-1 after 150 cycles, thus retaining about 92 % of its maximum capacity. The structural layered-to-spinel transformation can be more associated with Mn migration upon cycling in these Li and Mnrich cathodes. Thereby, partial substitution of Mn with Ni helps in partial suppressing the layered-to-spinel transformation and results in an improvement in their electrochemical performance. The specific capacities and energy density per gram of cathode materials in the cells were plotted against cycle number, as shown in Fig. 2. The full cells comprising 4 ACS Paragon Plus Environment

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Li1.2Ni0.13Mn0.54Co0.13O2 cathodes exhibited a specific capacity of about 240 mAh g-1 when cycled at C/5 rate, which decreased to a value of 130 mAh g-1 after 120 cycles. However, the full cells of Li1.2Ni0.27Mn0.40Co0.13O2 cathodes exhibited a specific capacity of about 200 mAh g-1, which decreased to a value of 185 mAh g-1 after 150 cycles, showing their remarkable electrochemical cycling stability. It is essential to compare the energy density of both types of full

cells

during

prolonged

cycling.

The

energy

density

of

full

cells

with

S p e c ific c a p a c ity / m A h g -1

Li1.2Ni0.13Mn0.54Co0.13O2 cathodes gradually decreased upon cycling from 485 to 228 Wh kg-1

S p e c ific e n e rg y / W h k g -1

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360 320

(a)

280

C/10 for initial 2 cycles

240

C/5 rate

200 (ii)

160 (i)

120

(b)

500 400 300

(ii)

200 100

(i) 0

20

40

60

80

100 120 140 160

Cycle number Fig. 2 (a) Capacity vs. cycle number measured during galvanostatic cycling and (b) specific energy density of full cells comprising (i) Li1.2Ni0.13Mn0.54Co0.13O2 and (ii) Li1.2Ni0.27Mn0.40Co0.13O2 cathodes and pre-lithiated graphite at C/5 rate after cycling at C/10 rate for 1st two cycles. EC-DMC (1:1) 1M LiPF6 solutions. The specific capacity was calculated per gram of cathode material and energy density was calculated per gram of cathode and anode materials in the cells. The precision level in these experiments is around 95%.


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due to decrease in their specific capacity with cycle number. However, the full cells comprising Li1.2Ni0.27Mn0.40Co0.13O2 cathodes exhibited remarkable stability in energy density (from 371 to 320 Wh kg-1) due to their stable capacity during cycling. Thus, it is interesting to note that although full cells of Li1.2Ni0.13Mn0.54Co0.13O2 cathodes exhibited initially high capacity and high energy density than those containing Li1.2Ni0.27Mn0.40Co0.13O2 cathodes, their capacity as well as energy density decreases upon cycling. Hence, the higher Ni content in the cathodes enables to stabilize full cells upon prolonged cycling. This stabilization effect is very similar to what was observed in half cells testing,20 what proves that the cathodes’ properties dominate the stability of the full cells which we explored in this work. Based on previous studies, we can suggest that substitution of Mn with Ni in these Li and Mn rich cathodes materials results in an increase in the oxidation state of Ni from 2+ to 3+. It is known that changing the oxidation state of Ni from 2+ to 3+ in these Li and Mn rich cathode materials can decrease their specific capacity, but enhances the cycling stability.11 The rate capabilities of these full cells were tested at different current densities starting from low (C/10) to high current densities (4 C). 5 cycles were measured at each rate and then the cells were returned back to cycling at low current densities. The results of these kinetic measurements are shown in Fig. 3. It can be seen that full cells comprising Li1.2Ni0.13Mn0.54Co0.13O2 exhibited higher capacities at low currents than those of Li1.2Ni0.27Mn0.40Co0.13O2. However, upon increasing the current densities, the specific capacity of cells containing Li1.2Ni0.13Mn0.54Co0.13O2 cathodes decreased pronouncedly. In turn, at high current densities, e.g., 2C and 4C rates, full cells comprising Li1.2Ni0.27Mn0.40Co0.13O2 cathodes exhibited higher specific capacities as compared to those containing Li1.2Ni0.13Mn0.54Co0.13O2 cathodes. Thus, full cells with Li1.2Ni0.27Mn0.40Co0.13O2 cathodes and pre-lithiated graphite anodes exhibited better rate capability as compared to those with Li1.2Ni0.13Mn0.54Co0.13O2 cathodes. Thus, higher content of Ni in these cathode


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materials has a positive impact on their rate capability as well. These comparative studies, including our previous work,20 show that the cathodes are the rate determining components in the full cells we explored.

-1

350

Specific capacity / mAh g

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300

C/10 C/5

250

C/10 C/2

200

(i) (ii)

1C 2C

150

4C

100 0

5

10

15 20 25 Cycle number

30

35

Fig. 3 Rate capability tests of full cells comprising (i) Li1.2Ni0.13Mn0.54Co0.13O2 and (ii) Li1.2Ni0.27Mn0.40Co0.13O2 and pre-lithiated graphite anodes at various increasing rates and finally ending at the initial low rate (C/10). EC-DMC (1:1) 1M LiPF6 solutions. The precision level in these experiments is estimated as 95%.

Electrochemical impedance spectra were recorded for the full cells we studied, at an equilibrium potential of 3.8 V during charge after 10 cycles. Based on extensive experience of impedance measurements of these types of systems (all kinds of composite electrodes, anodes, cathodes and cells), such measurements reflect the steady state behavior of these cells, after all electrodes’ surface processes that form passivation, ended. The potential chosen for comparison is very suitable, because it reflects major red-ox activities of these cathodes. Typical Nyquist plots of full cells with the 2 cathodes are presented in figure 4. Since the negative electrodes comprise lithiated graphite and they are similar in all the cells, the difference in impedance measured herein can be ascribed to the difference in the


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impedance properties of the cathodes. The Nyquist plots of both types of cells (with the two electrodes) exhibit two semicircles at high and medium frequency followed by a linear response at low frequency region. The first semicircle is usually assigned to surface film resistance whereas the 2nd semicircle is usually assigned to charge-transfer processes in the electrode/electrolyte solution interface and in the bulk of the active mass. The comparison between the spectra in figure 4 is surprising, showing considerably lower impedance for cells containing the Li1.2Ni0.27Mn0.40Co0.13O2 cathodes. Both semicircles in the spectra of cells containing this cathode are smaller compared to that of cells containing the cathode with the higher Mn content. As we explained many times before, a quantitative analysis of impedance spectra of composite electrodes of the type we describe herein and assignment of spectral features to relevant time constants of processes that the electrodes undergo is impossible. However, qualitative analysis and comparison among impedance spectra of these electrodes as a function of composition and conditions can be meaningful and important. The impedance spectra of the cathodes containing higher amount of nickel are significantly smaller, as demonstrated in figure 4. It is important to note that the effect of lower impedance relevant to all the frequency domains (high, low, medium). From these results we can conclude that increasing the amount of Ni on the account of Mn in these compounds change both their surface and bulk properties. An understanding of the effect of Ni level on the surface and bulk response of these materials requires more structural work which is beyond the scope of this paper. These impedance responses correlate very well with all other parameters. Lower specific capacity but impressive cycling stability and improved rate capability together with much lower overall impedance result from the fine tuning in the composition of these materials, as was demonstrated herein. Highly interesting is the surface effect of the content of nickel in these compounds. Usually, Ni rich Li[MnNiCo]O2 cathode materials exhibit higher surface reactivity in standard electrolyte solutions based on alkyl


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carbonates and LiPF6 compared to Mn rich lithiated transition metal oxides cathodes. This higher surface reactivity is expressed in higher impedance and lower rate capability. Here we examine Li and Mn rich Li1+x[MnNiCo]1-xO2 cathode materials and we find that increasing the content of Ni (yet, within a general stoichiometry of Li and Mn rich material) decreases the surface impedance, increases the stability and rate capability. These findings emphasize the complexity of these materials and their electrochemical response. In fact, the lower surface impedance we measured herein with the cathodes containing more Ni, may reflect structural effects near the surface that enhance charge transfer kinetics, rather than surface interactions of the cathode materials with solution species. The effect of the fine tuning we describe herein, promotes further rigorous structural analysis of these materials as a function of cycling (beyond the scope of this paper).

-120 (i) Li1.2Ni0.13Mn0.54Co0.13O2/graphite (ii) Li1.2Ni0.27Mn0.40Co0.13O2/graphite

-100

-80 Z" / Ω

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-60

-40

(i)

(ii) -20

0 0

20

40

60 Z' / Ω

80

100

120

Fig. 4 Nyquist plots of full cells comprising (i) Li1.2Ni0.13Mn0.54Co0.13O2 and (ii) Li1.2Ni0.27Mn0.40Co0.13O2 cathodes and pre-lithiated graphite anodes measured at an equilibrium potential of 3.8 V during charge after cycling for 10 cycles. EC-DMC (1:1) 1M LiPF6 solutions.


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Conclusions The electrochemical performance of cathodes comprising Li and Mn-rich Li1.2Ni0.13Mn0.54Co0.13O2 and Li1.2Ni0.27Mn0.40Co0.13O2 has been tested in Li-ion full cells with pre-lithiated graphite anodes. Working with such anodes enables to fabricate balanced cells and to ensure that the cells do not suffer from capacity fading mechanism arising from loss of active Li ions in the cells due to side reactions. Pre-lithiation of graphite anodes can be fully adjusted to prevent undesirable Li metal deposition and to provide the exact amount of excess of Li in the cells, which are required for the passivation processes (beyond the scope of this paper). The full cells comprising Li1.2Ni0.27Mn0.40Co0.13O2 cathodes exhibited initial specific capacities of about 190 mAh g-1, which is lower as compared to those of Li1.2Ni0.13Mn0.54Co0.13O2. However, these full cells exhibited better cycling stability as compared to full cells with Li1.2Ni0.13Mn0.54Co0.13O2 cathodes. A stable energy density of about 320 Wh Kg-1 (calculated based on the active electrodes in the cells) could be achieved with

cells

containing

Li1.2Ni0.27Mn0.40Co0.13O2

cathodes.

Also,

full

cells

with

Li1.2Ni0.27Mn0.40Co0.13O2 cathodes exhibited higher rate capability as compared to those containing Li1.2Ni0.13Mn0.54Co0.13O2 cathodes. This kinetic advantage is clearly supported by their lower overall impedance. As the negative electrodes (graphite) are similar in all the experiments reported herein, the better stability and the higher rate capability of full cells can be ascribed to the promising properties of Li1.2Ni0.27Mn0.40Co0.13O2 cathodes. These results emphasize the complexity of these materials, showing how a fine tuning of their composition affects pronouncedly their performance. This work indicates that Li and Mn-rich cathodes can be employed successfully in practical Li-ion batteries by optimizing their composition.


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Experimental The cathodes were fabricated following a similar procedure as reported recently by us20. The slurry for the anodes was prepared by mixing 85 wt% of graphite powder (Hitachi, SMG-ET1-20), 5 wt% of carbon black, and 10 wt% of PVdF. The electrodes were prepared by casting the slurries onto Cu foils current collectors by using a doctor-blade technique and then drying at 80 ◦C for overnight. Then the electrode fabrication processing for anodes was similar to that of the cathodes. The full cells consisted of Li and Mn-rich cathodes and prelithiated graphite as anode materials (instead of Li). The loading level of cathodes was 3.4 mg (2.21

mg/cm2)

for

Li1.2Ni0.13Mn0.54Co0.13O2

and

3.6

mg

(2.34

mg/cm2)

for

Li1.2Ni0.27Mn0.4Co0.13O2. For graphite anode, the loading was 3 mg (1.95 mg/cm2). The area of the electrodes in the coin type cells was around 1.54 cm2. The electrochemical performance was tested using coin-type cells 2325 (NRC, Canada) assembled in an argonfilled dry glove box (MBraun). The graphite electrodes were assembled with Li as the counter electrode in the coin cells in order to lithiate them in ethylene carbonate-dimethyl carbonate (EC-DMC) (1:1)/1M LiPF6 solutions (battery grade) electrolyte and porous polypropylene (Celgard) as separator. The cells are charged from the open circuit potential of 3.0 V to 0.02 V vs. Li and then discharged to 1.0 V for completing 1 cycle. Then for lithiation of graphite electrodes, the cells were charged to 0.02 V vs. Li. The graphite electrodes were recovered by disassembling the coin cells. Then full cells were assembled with Li and Mnrich cathodes and these pre-lithiated graphite electrodes using ethylene carbonate-dimethyl carbonate (EC-DMC) (1:1)/1M LiPF6 solutions (battery grade) electrolyte and porous polypropylene (Celgard) as separator. The galvanostatic charge-discharge cycling of full Liion cells was performed in the potential range of 2.0-4.7 V for 1st two cycles at C/10 rate followed by cycling in 2.0-4.6 V at C/5 rate using a computerized multi-channel battery


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testing instrument from Arbin Inc. The rate capability tests were carried out at different currents starting from low rate (C/10) to high rate (4C) for 5 cycles at each rate and then completing the cycling at low rate (C/10). Electrochemical impedance spectra (EIS) of full cells were recorded at an equilibrium potential of 3.8 V during charge with an amplitude of 5 mV in the frequency range of 100 kHz-0.01 Hz, using a Solartron model SI 1287 electrochemical interface and an 1255 HF Frequency Response Analyzer.

Acknowledgement This work was partially supported by the Israel Science Foundation (ISF) as part of the INREP project and also by the Israel Ministry of Science and Technology in the framework of the Israel-India bi-national collaboration program.


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References (1) Thackeray, M. M.; Kang, S. H.; Johnson, C. S.; Vaughey, J. T.; Hackney, S. A. Comments on the Structural Complexity of Lithium-rich Li1+xM1-xO2 Electrodes (M=Mn, Ni, Co) for Lithium Layered Cathode Materials Li[NixLi(1/3-2x/3)Mn(2/3-x/3)]O2 for Lithium-ion Batteries. Electrochem. Comm. 2006, 8, 1531-1538. (2) Lu, Z.; MacNeil, D. D.; Dahn, J. R. Layered Cathode Materials Li[NixLi(1/3-2x/3)Mn(2/3x/3)]O2 for Lithium-Ion Batteries. Electrochem. Solid-State Lett. 2001, 4, A191-A194. (3) Yu, H.; Zhou, H. High-Energy Cathode Materials (Li2MnO3-LiMO2) for Lithium-ion Batteries. J. Phys. Chem. Lett. 2013, 4, 1268-1280. (4) Armstrong, A. R.; Holzapfel, M.; Novak, P.; Johnson, C. S.; Kang, S. H.; Thackeray, M. M.; Bruce, P. G. Demonstrating Oxygen Loss and Associated Structural Reorganization in the Lithium Battery Cathode Li[Ni0.2Li0.2Mn0.6]O2. J. Am. Chem. Soc. 2006, 128, 8694-8698. (5) Johnson, C. S.; Li, N.; Lefief, C.; Vaughey, J. T.; Thackeray, M. M. Synthesis, Characterization and Electrochemistry of Lithium Battery Electrodes: xLi2MnO3·(1x)LiMn0.333Ni0.333Co0.333O2 (0 ≤ x ≤ 0.7), Chem. Mater. 2008, 20, 6095-6106. (6) Thackeray, M. M.; Kang, S.H.; Johnson, C.S.; Vaughey, J. T.; Benedek, R.; Hackney, S.A. Li2MnO3-Stabilized LiMO2 (M = Mn, Ni, Co) Electrodes for Lithium-ion Batteries J. Mater. Chem. 2007, 17, 3112-3125. (7) Gu, M.; Belharouak, I.; Zheng, J.; Wu, H.; Xiao, J.; Genc, A.; Amine, K.; Thevuthasan, S.; Baer, D. R.; Zhang, J.-G.; et al. Formation of the Spinel Phase in the Layered Composite Cathode Used in Li-Ion Batteries, ACS Nano, 2013, 7, 760-767. (8) Nayak, P. K.; Grinblat, J.; Levi, M.; Markovsky, B.; Aurbach, D. Structural and Electrochemical Evidence of Layered to Spinel Phase Transformation of Li and Mn Rich Layered Cathode Materials of the Formulae xLi[Li1/3Mn2/3]O2.(1-x)LiMn1/3Ni1/3Co1/3O2 (x = 0.2, 0.4, 0.6) upon Cycling. J. Electrochem. Soc. 2014, 161, A1534-A1547. (9) Jarvis, K. A.; Wang, C.-C.; Manthiram, A.; Ferreira, P. J. The Role of Composition in the Atomic Structure, Oxygen Loss, and Capacity of Layered Li–Mn–Ni Oxide Cathodes. J. Mater. Chem. A, 2014, 2, 1353 –1362. (10) Nayak, P.K.; Grinblat, J.; Levi, M.; Aurbach, D. Electrochemical and Structural Characterization of Carbon Coated Li1.2Mn0.56Ni0.16Co0.08O2 and Li1.2Mn0.6Ni0.2O2 as Cathode Materials for Li-ion Batteries. Electrochim. Acta, 2014, 137, 546-556. (11) Knight, J. C.; Manthiram, A. Effect of Nickel Oxidation State on the Structural and Electrochemical Characteristics of Lithium-rich Layered Oxide Cathodes. J. Mater. Chem. A, 2015, 3, 22199–22207. (12) Verde, M. G.; Liu, H.; Carroll, K. J.; Baggetto, L.; Veith, G. M.; Meng, Y. S. Effect of Morphology and Manganese Valence on the Voltage Fade and Capacity Retention of Li[Li2/12Ni3/12Mn7/12]O2. ACS Appl. Mater. Interfaces, 2014, 6, 18868−18877. (13) Fu, F.; Wang, Q.; Deng, Y. -P.; Shen, C. -H.; Peng, X. -X.; Huang, L.; Sun, S. -G. Effect of Synthetic Routes on the Rate Performance of Li-rich Layered Li1.2Mn0.56Ni0.12Co0.12O2. J. Mater. Chem. A, 2015, 3, 5197 –5203. 13 ACS Paragon Plus Environment

ACS Energy Letters

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(14) Ates, M. N.; Jia, Q.; Shah, A.; Busnaina, A.; Mukerjee, S.; Abraham, K. M. Mitigation of Layered to Spinel Conversion of a Li-Rich Layered Metal Oxide Cathode Material for LiIon Batteries, J. Electrochem. Soc., 2014, 161, A290-A301. (15) Yu, R.; Wang, X.; Fu, Y.; Wang, L.; Cai, S.; Liu, M.; Lu, B.; Wang, G.; Wang, D.; Ren, Q.; et al. Effect of Magnesium Doping on Properties of Lithium-rich Layered Oxide Cathodes Based on a One-step Co-precipitation Strategy, J. Mater. Chem. A, 2016, 4, 4941– 4951. (16) Nayak, P. K.; Grinblat, J.; Levi, M.; Levi, E.; Kim, S.; Choi, J. W.; Aurbach, D. Al Doping for Mitigating the Capacity Fading and Voltage Decay of Layered Li and Mn-Rich Cathodes for Li-Ion Batteries, Adv. Energy Mater. 2016, 6, 1502398-1502411. (17) Wang, C.-C.; Lin, Y.-C.; Chou, P.-H.; Mitigation of Layer to Spinel Conversion of a Lithium-rich Layered Oxide Cathode by Substitution of Al in a Lithium ion Battery. RSC Adv., 2015, 5, 68919–68928. (18) Ma, Z.; Huang, J.; Quan, J.; Mei, L.; Guo, J.; Li, D.; Improved Electrochemical Performances of Layered Lithium Rich Oxide 0.6Li[Li1/3Mn2/3]O2·0.4LiMn5/12Ni5/12Co1/6O2 by Zr Doping, RSC Adv., 2016, 6, 20522–20531. (19) Qiao, Q.-Q.; Qin, L.; Li, G.-R.; Wang, Y.-L.; Gao, X.-P. Sn-stabilized Li-rich Layered Li(Li0.17Ni0.25Mn0.58)O2 Oxide as a Cathode for Advanced Lithium-ion Batteries. J. Mater. Chem. A, 2015, 3, 17627–17634. (20) Nayak, P. K.; Grinblat, J.; Levi, E.; Penki, T. R.; Levi, M.; Sun, Y- K.; Markovsky, B.; Aurbach, D. Remarkably Improved Electrochemical Performance of Li And Mn-Rich Cathodes on Substitution Of Mn With Ni. ACS Appl. Mater. Interfaces, 2016, (in press, DOI: 10.1021/acsami.6b07959). (21) Llave, E. dela; Borgel, V.; Park, K.-J.; Hwang, J.-Y.; Sun, Y.-K.; Hartmann, P.; Chesneau, F. -F.; Aurbach, D. Comparison between Na-Ion and Li-Ion Cells: Understanding the Critical Role of the Cathodes Stability and the Anodes Pretreatment on the Cells Behavior. ACS Appl. Mater. Interfaces, 2016, 8, 1867−1875.


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Electrochemical Performance of Li-and Mn-Rich Cathodes in Full

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