Two Anode Materials for Li ion Batteries with different ...

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2 rue Henri Dunant - 94320 Thiais - France [email protected]. Aurelien ..... Rouviere, "Silicon nanowires as negative electrode for lithium-ion microbatteries" ...
Two Anode Materials for Li ion Batteries with different reaction mechanisms : silicon nanowires and ruthenium nitride thin film

Barbara La"ik, Jean-Pierre Pereira-Ramos

Jean-Fran90is Pierson

Groupe d'Electrochimie et Spectroscopie des MATeriaux ICMPE - UMR UPEC-CNRS

2 rue Henri Dunant - 94320

Institut Jean Lamour - Departement CP2S UMR Universite de Lorraine - CNRS

7182

Parc de Saurupt - CS

Thiais - France

7198 50840 - 54011 Nancy cedex - France

[email protected]

Lucie Leveau, Costel Sorin Cojocaru Aurelien Gohier

Laboratoire de Physique des Interfaces et des Couches

Renault SAS - DREAMIDETA/SEE

1,

Avenue du Golf

- 78288

Minces - Ecole Polytechnique, Route de Saclay

Guyancourt - France

- 91128 Palaiseau Cedex - France

Abstract - Research carried out in our laboratory is devoted to

main drawback is the large volume expansion associated with

new materials of electrodes for lithium ion batteries.

lithium insertion that limits their ability to cycle.

This

presentation focuses on anodic materials, especially on two examples,

silicon

electrochemical

and

ruthenium

properties

and

nitride.

In

structural

both

cases,

evolutions

are

correlated in order to optimize performances in terms of specific capacity, cyclability and rate capability.

Keywords-lithium batteries; anode material; silicon nanowires; ruthenium nitride; thin films

work

et

by

our

laboratory,

Spectroscopie

des

the

Groupe

MATeriaux,

are

dedicated to research of new electrode materials for lithium batteries, whether positive or negative. New materials are synthesized, characterized structurally and electrochemically, in order to highlight their reactivity versus lithium correlate

their electrochemical

performances

to

and

structural

modifications during charge and discharge processes. This approach

enables

the

optimization

of

the

compound

preparation, the composite electrode composition and the electrochemical conditions of cycling. These electrode materials can operate according to different reaction mechanisms during charge and discharge versus lithium.

The

fust

generation

of

commercial

lithium-ion

batteries has been developed around materials that involve lithium

ion intercalation.

Their

crystallographic

structure

allows the reversible Li+ insertion without major structural changes. The insertion reaction demonstrates low capacity, with a maximum of

1

silicon,

and secondly

to a conversion material,

II.

ALLOYING

The ability of silicon to form Li-rich alloys (up to Li,sSi4 at

electron transferred per transition metal.

Alternative mechanisms, alloying and conversion reactions discovered in the year 2000

[1],

3580

mAh g")

makes it one of the best candidates to replace commercial

INTRODUCTION

conducted

d'Electrochimie

material,

ruthenium nitride.

room temperature, i.e. a specific capacity of

I. The

We propose to describe, in this presentation, part of our

work on the negative electrode dedicated one hand to Li-alloy

present the main advantage of

leading to higher electrochemical capacity. However, their

graphite anode and to reach higher energies. The concomitant huge volume variation

(�300%)

with the alloying process is

however detrimental to the durability of silicon electrodes since

it induces mechanical stress that can cause pulverization of the

material and break of electrical conductivity. ID nanometric

structures, like silicon nanowires (SiNWs), have been proposed

by Cui and our group in

2007-2008 [2-3],

to improve the

battery cycle life thanks to better accommodation of volume expansion

than

bulk

silicon.

Moreover,

they

have

the

advantage of being directly grown on the current collector,

preventing the use of any binder or conducting additives that lower the specific capacity of the electrode.

The SiNWs are synthesized by chemical vapor deposition (CVD) according to the vapor-liquid-solid

(VLS)

growth

mechanism in SiH4 diluted in H2 in the temperature range of

520-580°C (Figure 1).

Depending on processes and synthesis conditions, SiNWs present various sizes with a length range

10-500

nm.

�10

/lm and diameter in the

So we have demonstrated that samples with

different diameter distributions could be obtained by tuning the initial gold thin film thickness

[4].

Indeed, gold acts as a

catalyst. The film previously deposited on the substrate, forms

small Au-clusters when is heated above the catalyst-Si eutectic

978-1-4799-7336-1/14/$31.00 ©2014 IEEE

melting temperature. Then the SiH4 flow is introduced in the chamber and silicon precipitates between the substrate and the gold clusters. As long as the silane flow is maintained, the silicon precipitation occurs leading to a nanowire of which diameter is controlled by the gold cluster size. In this way, three gold thin films with different thicknesses, namely 3 nm,

The objective is to allow limited swelling of the silicon, by limiting either the depth of lithiation, or the depth of delithiation, or the delithiation cut-off voltage as depicted in Figure 3. Extended optimized cycling experiments are performed leading to significant improvements of capacity retention at 900 mAh g-' , with more than 1800 cycles at C/5 rate and more than 350 cycles at Ie. Furthermore, we prove that combining these optimized cycling conditions with the use of an electrolyte additive can further enhance the capacity retention, with more than 2000 cycles at 900 mAh g-' at lC

80 � 0 E

0>

'iii 3

60

.�

(;j :; E :J ()

20

nanowire diameter I nm

rate. Figure 2. Histograms of cumulative weight of silicon nanowires as a function of the initial gold thin film thickness (black 3 nm; white 10 nm; gray 30 nm).

10 nm and 30 nm were deposited. As presented in Figure 2, this parameter clearly impacts on the SiNWs diameter distribution of the sample. 80wt Si% correspond to nanowires with diameter respectively thinner than 65 nm, 210 nm and 490

2.0 1.8

- 20mV-2V(a)

lm i ited lithiation - 2 V (b) -- 20mV- lm i t i ed delt i ha i to i n .. ...... limited It i ha i to i n - 0,8 V (d) --

1.6

run .

1.4

Figure I.

SEM images of SiNWs sample obtained by CYD-YLS at 550°C

;J

(e)

1.2

+

The electrochemical behavior of such SiNWs sample shows an attractive working potential window. Well-defined voltage plateaus are obtained and a low polarization leads to a narrow potential window between 0.1 and 0.45 V vs. Li+/Li. The effect of SiNWs diameter on cycling performances and rate capability are especially investigated and we show the best results are obtained with the smallest diameters. For instance, at ClIO rate, values of 3500, 2700 and 2400 mAh g-' are respectively obtained in the second Iithiation process for 65, 210 and 490 run Moreover, The sample with smallest diameter values exhibits the best rate capability and can sustain high rates up to 5 C with interesting capacities of 2500, 1500 and 500 mAh g-' at C, 2. 5 C and 5 C respectively. .

Besides, an extensive investigation of the influence of different cycling conditions of these samples is carried out. A comparative study of the cycling parameters is performed in order to improve the capacity retention of SiNWs electrode [5].

;J



1.0

>

0.8

""

0.6 0.4 0.2 0.0 0

500

1000

1500

2000

2500

3000

QI mAh g.l

Figure 3. TIIustration of the adopted cycling strategies: a) tandard cycling between 20 mY and 2 Y; strategy b) Iithiation-Iimited (900 mAh g") cycling with delithiation to 2Y; strategy c) delithiationlimited (900 mAh g") cycling with lithiation to 20 mY; and strategy d) lithiation-limited (900 mAh g") cycling with reduced delithiation cut-off voltage of 0.8 Y

Further studies are currently underway. They focus in particular on the synthesis of hybrid materials with new

architectures based on silicon and carbon. In that case the use of these two different materials aims to capitalize the respective electrochemical and physical properties of each component, namely the attractive electrochemical performance of silicon versus lithium and the carbon properties like more efficient electron transport pathways. We develop vertically aligned carbon nanotubes decorated with silicon particles (VA­ CNTs/Si) arrays with minimized diameter size, 5 and 10 nm respectively [6]. Such an architecture is found to sustain very high C rates without any significant polarization and without structural damaging. Cycling at 10 C leads to a recovered capacity of 800 mAh g-I, i.e. still two times the capacity of graphite. The key factors for good cycling properties are the perfect adhesion between CNTs directly connected to the current collector and silicon particles thus facilitating electron and lithium ion transport pathway and limiting the diffusion process occurring in conventional electrodes. Our results suggest the VA-CNTs/Si are effective for overcoming the effects of volume expansion-contraction and represent a promising direction for use in practical cells. III.

CONVERSION REACTION

As already mentioned, materials that can undergo conversion reactions are fully reduced to metallic state, involving multiple electrons and then delivering remarkably high capacity values. Since it has been proved that conversion reactions could moreover lead to high reversibility and cycling ability, great attention has been given to metal nitrides as prospective anode. Many binary metal nitrides, in thin film form, have already been presented in literature because they are likely to replace metallic lithium in thin-film lithium-ion micro-batteries. To our knowledge, ruthenium nitride has never been studied for this negative material application and yet it has a high theoretical specific mass capacity about 700 mAh il. Its behavior has been investigated in this respect [7-8].

·�:y \t.J.1 � ·I .

20

30

,

50

40 26/0

modification of the shape in accordance with a conversion process. Subsequent cycles roughly look the same as a reversible process takes place. Available capacities during the first and second cycles are close to the theoretical one: higher during the first discharge because of the extra electron consumption related to the Solid Electrolyte Interphase formation (SEI), quite lower during the second discharge. RuN thin films are directly deposited on stainless steel current collectors by reactive magnetron sputtering of a metallic ruthenium target (50 mm in diameter and 3 mm thick) in various argon/nitrogen mixtures or in pure nitrogen. The deposition conditions yields a film growth rate of 250 nm h·l. We have demonstrated that for thicknesses measured by tactile profilometry and varying from 250 to 850 nm, a linear relationship exists between the mass and the deposited film thickness. This means that the deposit is not affected by the substrate nature and that the deposited compound is homogeneous with a density close to 6.8 g cm·3• As commonly encountered for reactively sputtered transition metal nitrides, RuN films exhibit a columnar microstructure (Figure 4 inset). XRD analysis clearly shows that the RuN films grow with a strong preferred orientation in the [Ill] direction (Figure 4). We demonstrate that such sample is able to cycle more than 70 cycles between 20 mV and 3 V with a stabilized capacity of about 350 mAh g-I. It is possible to access to higher capacity using thicker samples (Figure 6). The linear relationship observed on the graph (to the right) means that the entire deposited material is active, the electrochemical processes are the same whatever the thickness, without any limitation of lithium diffusion or electron tranfer.

Figure 5. Cyclic voltammogramms measured at 50 IlV.S·1 and galvanostatic discharge/charge curves measured at C/2 ( 1 17 mA.g-l) of 250 nm-thick thin film between 0.02 V and 3 V (first cycle: full red line; second cycle: dashed blue line)

60

(Cu K ) 0.

Figure 4. Experimental X-ray diffractogram (Cu Kx radiation) of a RuN film. SEM image of a cross-section highlighting the columnar microstructure.

Electrochemical properties versus lithium have been evaluated. First and second cycles, both in cyclic voltammetry and galvanostatic cycling (Figure 5) exhibit a huge

-0075

EfVvs. l(lLi

Figure 6. (a) Galvanostatic discharge/charge first (full lines) and second (dashed lines) cycles of 250 nm, 450 nm, 650 nm and 850 nm-thick thin films

measured at C/2 ( 1 17 mAg-I) between 0.02 V and 3 V. (b) Corresponding discharge/charge capacities versus film thickness.

Applying higher current densities is possible without drastic decrease of the capacity (320 mAh g-' and 260 mAh g-' respectively for 2C and 5C) and without any consecutive material damage . Further studies are currently underway. They focus in particular on the structural evolution of the electrode upon cycling. Complementary analysis are carried out by XRD, SEM, TEM, SAED, EELs and XPS and should led us to propose a detailed conversion mechanism for ruthenium nitride_ REFERENCES [I]

P. Poizot, S. Laruelle, S. Grugeon, L. Dupont and J-M. Tarascon, " Nano-sized transition-metaloxides as negative-electrode materials for lithium-ion batteries", Nature, vol. 407 Issue 6803 pp. 496-499 September 2000

[2]

C.K. Chan, H. Peng, G. Liu, K. Mcllwrath, X.F. Zhang, R.A. Huggins and Y.Cui, "High-performance lithium battery anodes using silicon nanowires" Nature Nanotechnology vol. 3 pp. 31-35 Janvier 2008.

[3]

B. Lark, L. Eude, J.-P. Pereira-Ramos, C.S. Cojocaru, D. Pribat and E. Rouviere, "Silicon nanowires as negative electrode for lithium-ion microbatteries" Electrochimica Acta, vol. 53 pp. 5528-5532 July 2008.

[4]

A Gohier, B. Lark, J-P. Pereira-Ramos, C.S. Cojocaru, P. Tran Van, "Influence of the diameter distribution on the rate capability of silicon nanowires for lithium-ion batteries anodes", Journal of Power Sources, vol. 203 pp. 135-139. April 2012

[5]

L. Leveau, B. Lark, J-P. Pereira-Ramos, C. S. Cojocaru, A. Gohier P. Tran-Van, "Cycling strategies for optimizing silicon nanowires performance as negative electrode for lithium-ion battery", unpublished.

[6]

A Gohier, B. Lark, K-H. Kim, J-L. Maurice, C.S. Cojocaru, J-P. Pereira-Ramos, P. Tran Van, "High-rate capability silicon decorated vertically aligned carbon nanotubes for Li-ion batteries", Advanced Materials, vol. 24, Issue 19 pp. 2592-2597 May 2012.

[7]

S. Bouhtiyya, R. Lucio Porto, B. Lark, P. Boulet, F. Capon, J-P. Pereira­ Ramos, T. Brousse, J-F. Pierson, "Application of sputtered ruthenium nitride thin films as electrode material for energy storage devices", Scripta Materialia, Vol. 68, pp. 659-662 May 2013

[8]

B. Lark, S. Bourg, J-P. Pereira-Ramos " J-F. Pierson, "Electrochemical reaction of lithium with ruthenium nitride thin film", unpublished.