Li-ion cells

A-T Battery Co. is a joint venture between Asahi and Toshiba, to produce Li ion batteries. Fuji Electric and Fuji Film, Hitachi-Maxell (Li-thionyl cells, and now also Li ion cells), Japan Storage Battery Co. (prismatic cells), and Matsushita Battery Co. cover most systems. Mitsubishi Electric, Mitsui, and Sanyo are major producers of the Li - Mn02 system. Sony Energy... 

Practically every battery system uses carbon in one form or another. The purity, morphology and physical form are very important factors in its effective use in all these applications. Its use in lithium-ion batteries (Li-Ion), fuel cells and other battery systems has been reviewed previously [1 -8]. Two recent applications in alkaline cells and Li-Ion cells will be discussed in more detail. Table 1 contains a partial listing of the use of carbon materials in batteries that stretch across a wide spectrum of battery technologies and materials. Materials stretch from bituminous materials used to seal carbon-zinc and lead acid batteries to synthetic graphites used as active materials in lithium ion cells. 

The proper mixing of the graphite with the Mn02 is critical for high rate performance. It is necessary to put work into the mix to uniformly coat the manganese dioxide particles with a thin layer of graphite. This provides a low resistance path from the manganese to the cell terminals to minimize the internal resistance of the cell. A similar effect can be expected if used in cathode formulations for Li-Ion cells. 

The Li-Ion system was developed to eliminate problems of lithium metal deposition. On charge, lithium metal electrodes deposit moss-like or dendrite-like metallic lithium on the surface of the metal anode. Once such metallic lithium is deposited, the battery is vulnerable to internal shorting, which may cause dangerous thermal run away. The use of carbonaceous material as the anode active material can completely prevent such dangerous phenomenon. Carbon materials can intercalate lithium into their structure (up to LiCe). The intercalation reaction is very reversible and the intercalated carbons have a potential about 50mV from the lithium metal potential. As a result, no lithium metal is found in the Li-Ion cell. The electrochemical reactions at the surface insert the lithium atoms formed at the electrode surface directly into the carbon anode matrix (Li insertion). There is no lithium metal, only lithium ions in the cell (this is the reason why Li-Ion batteries are named). Therefore, carbonaceous material is the key material for Li-Ion batteries. Carbonaceous anode materials are the key to their ever-increasing capacity. No other proposed anode material has proven to perform as well. The carbon materials have demonstrated lower initial irreversible capacities, higher cycle-ability and faster mobility of Li in the solid phase. 

The reaction at the anode in Li-Ion cells is given in Equation 1. During charge the lithium ions approach the surface of the carbon where they accept an electron and enter the lattice. On discharge, the opposite reaction occurs. The electrochemical reaction is thought to occur on the edge planes and not the basal plane of the carbon/graphite particles. 

Lithium-ion (shuttle-cock, rocking-chair, swing) battery is widely considered as the most advanced power source for consumer electronics and is regarded as the most promising battery technology for a variety of other applications, such as electric vehicles, medicine and space exploration. One of the most critical factors in designing successful Li-ion cell is the choice of... 

As the end-user in the NATO SfP project Carbons as materials for the electrochemical storage of energy Central Laboratory of Batteries and Cells does research and development works on the application of novel carbonaceous materials to the Li-ion technology. The general idea of these works is to build prototypes of cylindrical Li-ion cells on the basis of materials produced in the cooperating laboratories. The aim of this paper is to examine the applicability of selected commercial and non-commercial carbon materials (with special attention devoted to boron-doped carbons) to the construction of a practical cylindrical Li-ion cells. 

Figure 3. Discharge capacities for he first ten cycles for the Li-ion cell SL-20 anode. The inset discharge curve for the first cycle.

Commercial and non-commercial carbons were tested for their applicability as anode of lithium-ion battery. It was found that Superior Graphite Co s materials are characterized both by high reversible capacities and low irreversible capacities and thus can be regarded as good candidates for practical full cells. Cylindrical AA-size Li-ion cells manufactured using laboratory techniques on the basis of SL-20 anode had initial capacities over 500 mAh (volumetric energy density ca. 240 Wh/dm3). Boron-doped carbon... 

SEM images indicate that both graphite samples have very similar morphologies. Negative electrode laminates with active materials of SL-20 and SLC-1015 were then prepared using similar compositions. These laminates were then used to prepare negative electrodes that were inserted into Li-ion cells having similar cathodes and electrolyte materials. 

Elidrissi MML., Corrector JI., Tirado JL., C. Perez V. SnHP04 a promising precursor for active material as negative electrode in Li-ion cells Electrochimica Acta 2001 47 489-93. 

High-power Li-ion cells with a LiNio.8Coo.15Alo.05O2 cathode, a synthetic graphite anode, 1.2 M LiPF6 + ethylene carbonate + ethyl-methyl carbonate (EC/EMC) electrolyte, and a Celgard 2300 separator, were... 

The samples were collected from the cathodes 2.5 cm away from the current collector tab, washed in pure dimethyl carbonate (DMC), and soaked in DMC for 30 minutes after removal from Li-ion cells inside an argon-filled glove box. This procedure removed electrolyte salt from the electrode to prevent its reaction with air and moisture. An integrated Raman microscope system Labram made by ISA Groupe Horiba was used to analyze and map the cathode surface structure and composition. The excitation source was an internal He-Ne (632 nm) 10 mW laser. The power of the laser beam was adjusted to 0.1 mW with neutral filters of various optical densities. The size of the laser beam at the sample was 1.2 pm. 

What do I mean by taking out everything superfluous That could mean any external circuitry not directly linked to the core functionality (such as current limits, OVPs, crowbars, OTPs, etc.). But it can mean much more. For example, a few days ago I walked into the lab to talk to a junior colleague of mine. He happened to be looking at some minor issue on a small DC-DC converter board in front of him. ft was meant for a Li-ion cell input, and set for IV output. Suddenly, he started looking really puzzled. Why is the input... 

Figure 20. Construction of (A) cylindrical, (B) prismatic, and (C) polymer Li ion cells. (Reprinted with permission from a brochure by Sony Corporation).

Sheem KY, Lee YH, Lim HS. High-density positive electrodes containing carbon nanotubes for use in Li-ion cells. J Power Sources 2006 158 1425-1430. 

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