Study of styrene butadiene rubber and sodium methyl cellulose as binder for negative electrodes in lithium-ion batteries

doi:10.1016/j.jpowsour.2006.03.073

Journal of Power Sources

Volume 161, Issue 1, 20 October 2006, Pages 617-622

https://doi.org/10.1016/j.jpowsour.2006.03.073 Get rights and content

Abstract

Graphite and nano-silicon-based negative electrodes in lithium-ion batteries with low binder content were evaluated. The effectiveness of styrene butadiene rubber (SBR) and various types of cellulose containing electrodes were compared to standard electrodes containing PVdF as binder. The cycling performance of lithium-based half cells in EC:DMC (1:1), 1 M LiPF₆ shows that styrene butadiene rubber (SBR), sodium carboxymethyl cellulose (Na-CMC), or both combined have a similar bonding ability as conventional poly(vinylidene fluoride) (PVdF). However, using Na-CMC the irreversible charge capacity in the first cycle decreased in comparison with electrodes containing PVdF binder. Nano-Si electrode containing 1% SBR/1% Na-CMC as binder show the same cycle stability as an identical electrode containing 10% PVdF binder.

Introduction

Lithium-ion batteries are becoming more and more important in the world market of energy devices, with respect to their energy density, which is amongst the highest for any known secondary battery system (up to more than 150 Wh kg⁻¹). For large size applications such as in EV or HEV, both higher energy density and low-cost materials are required. In order to enhance the performances of lithium-ion batteries, researchers and battery-manufacturers are trying to create new electrode materials, new electrolytes, and new additives. However, battery efficiency is strongly dependent on the electrode engineering [1], [2], [3]. An important approach to improve the behaviour of lithium-ion batteries is the optimisation of the binder used for the electrode preparation, which should meet various requirements. The role of binders becomes increasingly important in terms of energy density of the whole battery. It is desirable to reduce the binder content, whilst at the same time maintaining the required properties and functionality of the electrode. Beyond its chemical and electrochemical stability in electrode/electrolyte interactions, the binder has to survive the large repeated dimensional changes of the electrode during the cycling of the cell. In commercial lithium-ion batteries, poly(vinylidene fluoride) (PVdF) has been used as binder for both the negative and positive electrodes because of its good electrochemical stability and high adhesion to the electrode materials and current collectors [3].

An interesting approach to improve the energy density of the negative electrodes for their use in lithium-ion batteries is the mixing of active materials with only small amounts of binder materials [4], [5], [6]. Especially appealing would be to lower the content of a binder for a nano-silicon-based electrode [7]. The main disadvantage of all alloy-based electrodes is the huge volume change which occurs upon the insertion/deinsertion of the lithium into and from alloying the host material. The volume change of both silicon and tin-based alloy electrodes is around 200–300% [8]. This leads to pronounced mechanical fatigue upon prolonged cycling, as the particles break-up and become non-contacted. Capacity loss and cycle life of, e.g. composite silicon-based electrodes is known to depend on many variables, including the amount of Si in the electrode formulation, binder properties, and electrode engineering [9], [10]. Most of the published work on binders deals with the testing of new binder materials and their interactions with the active materials and the electrolyte [11]. It was also shown that the binder amount and electrode engineering had influence on the electrochemical performance of tested electrodes [12]. In this paper, the role of styrene butadiene block co-polymer (SBR) and sodium carboxy methylcellulose (Na-CMC) as binders for TIMREX^® SFG synthetic graphite and nano-silicon-based negative electrodes has been investigated and analysed in order to improve the electrodes, their capacity and cycle life. Note that SBR possesses higher flexibility, stronger binding force, and higher heat resistance than the widely used PVdF [10]. Moreover, Na-CMC and SBR are soluble in environmental friendly solvents such as water [13] and ethylacetate, respectively, which is of importance for the future electrode production.

In this work, test electrodes were prepared combining various kinds of binders: PVdF, SBR, Na-CMC, mixtures of SBR and Na-CMC, ethyl cellulose, and methyl cellulose. The electrochemical performances of the obtained electrode composites, with different binder contents were tested and compared. In order to get a direct view on the effect of the binders on the SEI-film formation and cycling process, scanning electron microscopy (SEM) analyses of cycled and uncycled electrodes were performed.

Section snippets

Experimental

TIMREX^® SFG (TIMCAL SA, Bodio, Switzerland) graphite powders and Si-based electrode materials were used as negative electrode. Two TIMREX^® SFG graphites with different particle size (SFG6 and SFG44 having d₉₀ values of 6 and 44 μm, respectively) were used as received [14]. The silicon composite material was prepared by direct mixing of nano-scale silicon (Degussa, Marl, Germany) with graphite TIMREX^® KS6 and carbon black SP (TIMCAL SA, Bodio, Switzerland). The idea of such electrode preparation

Results and discussion

In our previous work, we reported the very stable cycling of SFG44 graphite electrodes using PVdF as a binder [16]. Typically, a reversible charge capacity of about 360 m Ag⁻¹ and a coulombic efficiency of 93% is obtained in the first galvanostatic charge/discharge cycle for the SFG44 negative electrode material at a specific current of 10 m Ag⁻¹ in the EC:DMC (1:1), 1 M LiPF₆ electrolyte. During the second and subsequent cycles, the cycling efficiency increases rapidly from 99 to 99.9%. In Fig. 1,

Conclusion

We have shown that SBR and Na-CMC either alone, or in combination, show a similar bonding ability as the conventional PVdF binder, and that negative electrodes bonded by these binders have nearly the same cycleability. However, using Na-CMC as binder the irreversible charge losses in the first cycle of SFG graphites are lower than for PVdF as binder. Low fading and low irreversible capacity losses upon the cycling for the SFG6 graphite electrode were attributed to the very low particle size of

Acknowledgements

The authors would like to express their gratitude to Dr. Michael E. Spahr (TIMCAL SA, Bodio, Switzerland) for the donation of the graphite samples, Selectchemie AG (Zürich, Switzerland) for the donation of methyl cellulose and ethyl cellulose samples, Dow Chemicals (Dow Chemicals, Horgen, Switzerland) for the donation of the SBR sample and Mr. Laurence J. Hardwick for the editing of this article.

References (17)

M. Broussely
J. Power Sources
(1999)
A.N. Jansen et al.
J. Power Sources
(1999)
J. Drofenik et al.
Electrochim. Acta
(2003)
J.O. Besenhard et al.
J. Power Sources
(1997)
M. Yoshio et al.
J. Power Sources
(2006)
M. Wachtler et al.
J. Electroanal. Chem.
(2001)
J.H. Lee et al.
J. Power Sources
(2005)
H. Buqa et al.
J. Power Sources
(2005)

There are more references available in the full text version of this article.

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Short communicationStudy of styrene butadiene rubber and sodium methyl cellulose as binder for negative electrodes in lithium-ion batteries

Abstract

Introduction

Section snippets

Experimental

Results and discussion

Conclusion

Acknowledgements

J. Power Sources

J. Power Sources

Electrochim. Acta

J. Power Sources

J. Power Sources

J. Electroanal. Chem.

J. Power Sources

J. Power Sources

Short communication
Study of styrene butadiene rubber and sodium methyl cellulose as binder for negative electrodes in lithium-ion batteries