Elsevier

Journal of Power Sources

Volume 91, Issue 2, December 2000, Pages 86-91
Journal of Power Sources

State of the art of commercial Li ion batteries

https://doi.org/10.1016/S0378-7753(00)00458-4Get rights and content

Abstract

A number of criterial specific parameters of the electrodes in five commercial Li ion batteries of leading producers are derived on the basis of the recently published data by Johnson and White [B.A. Johnson, R.E. White, J. Power Sources 70 (1998) 48]. The impact of these parameters on the cycling performance of the cells is analyzed. It is shown that in spite of the similarities in the type of the electrode, electrolyte and separator materials, there are considerable differences in the capacity, masses, apparent densities and material balance ratio. For example the A&T cell with the smallest masses of its active electrode materials and lowest apparent densities of the electrodes has achieved the largest cell capacity, highest rate capability and cycling stability. This is accomplished thanks to the high quality of its electrode materials' novel electrode design with double current collectors for each electrode and largest material balance ratio. The above and other examples in the paper reveal the complexity of interactions between the criterial parameters of the electrodes and indicate that an improvement in the cell performance requires not only investigations but creativity as well.

Introduction

The introduction of the Sony rechargeable Li ion battery in 1991 marks the beginning of a period of development of a new generation of small-size high-energy sources. The lithium metal-free batteries with carbonaceous anodes, lithiated oxides of transition metals of the 3d group as cathodes, as well as ethylene carbonate-based electrolytes are characterized not only with high energy density, high rate capability, long cycle life, but what is most important is its large degree of safety. All these distinctions of the new batteries and the rapidly increasing demand of small batteries by the portable telecommunication and computer market led to an unprecedented increase in their production. Presently, more than 10 Japanese, American, European and Asian companies are fabricating annually tens of millions.

The recently published detailed description by Johnson and White [1] of the materials, design, physical properties, electrochemical parameters and cycling performance of five commercially available Li ion cells revealed many similarities between them, e.g., same cathode material (LiCoO2), similar anode materials (graphite or coke), similar electrolytes based on LiPF6 and ethylene carbonate, same current collector foils, similar separator materials, same jelly roll configuration and same size.

Nonetheless, there are quite many differences in some of the physical parameters and the performance characteristics of the cells with respect to capacity, rate capability, cycling stability accumulated capacity and cell resistance. It would be of interest both for the cell designers and the scientists involved in the investigation of electrode materials to elucidate as far as possible the effect of some of the physical and electrochemical characteristics of the electrodes and of the cell design on these performance parameters.

Based on the data disclosed in Ref. [1], a number of specific physical and electrochemical relationships are derived in this paper which exerts more influence on the cell performance than others. Their knowledge could be helpful in the efforts for the optimization of the batteries and the materials they use.

Table 1 presents the most significant physical characteristics of the cells as disclosed in Ref. [1], as well as some additional parameters derived from them such as packaging density, material balance ratio, volume of electrode materials, loading, apparent density of electrodes and their porosity. In the estimation of the average values of these characteristics (where reasonable) the bracketed values are omitted either because of the different design as in the A&T cell or of different size, as in Matsushita. Some extreme values are also omitted. The masses of the electrodes comprise the active and conductive materials and binders. The volumes of the electrodes comprise the volumes of the same materials plus that of the pores. The masses of the pure active materials m+ and m are estimated from those of the electrode materials assuming that the relative active mass content is 85% for the positive and 95% for the negative. In all cells, the same current collectors are used: 25 μm Al foil for the positive and 18 μm Cu foil for the negative. In four of the cells, the electrode material is applied on both sides of the foils, whereas in the A&T cell, there are two foils for each electrode with the electrode material applied on one side only. The loading is calculated by dividing the mass of the active material by its geometric area. The electrode volumes are obtained by multiplying the electrode thickness by its geometric area divided by two except for that of the A&T cell, where the area shown is not divided. Four of the cells are of the 18650 size that indicates their diameter is 18 mm and length is 65 mm. Only the Matsushita cell is of the 17500 size, i.e., 17 mm in diameter and 50 mm long. The packaging density is estimated according to Eq. (4). Table 2 describes the cycling conditions of the cells. Here, the gravimetric capacities are with respect to the mass of the pure active material only. The charging voltage limit is 4.2 V and the discharge cut-off voltage is 2.5 V for all cells. Table 3 gives the performance characteristics of the electrodes and the cells. The specific capacities and energies of the cells are with respect to total cell mass or volume, which is 11.35 cm3 for the Matsushita cell and 16.54 cm3 for the four other cells.

It is noteworthy that the data reported by Johnson and White [1] are based on the results obtained from testing of 85 cells of the five manufacturers.

Section snippets

Effect of packaging density and porosity

The gravimetric discharge capacity, qd, of each of the electrodes, determined at the given cycling conditions is equal toqd=ηqr,Ah/gwhere η is the utilization coefficient, called further utilization for brevity, and qr is the reversible discharge capacity determined at sufficiently low rates (to avoid the influence of diffusion hindrances) and in a voltage range providing simultaneously large capacity, stable cyclability and safety of the cell. The value of η is dependent on many other factors

References (5)

  • B.A Johnson et al.

    J. Power Sources

    (1998)
  • R Moshtev et al.

    J. Power Sources

    (1999)
There are more references available in the full text version of this article.

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