Lithium LiCoO

Figure 52. Discharge characteristics of some lithium-nickel oxides and LiCoO, (current density 0.25 mA cm2).

The high cost and toxicity of cobalt compounds has prompted a search for alternative materials that intercalate lithium ions. Examples of these are LiMn204 [iv], LiCoo.2Nio.8O2. LiNio.5Mni.504 [v], LiNio.5Mno.5O2 [vi], LiFeP04 [vii], Lix VO [viii], and LixMrVOz (M = Ca, Cu) [ix], etc. 

Fig. 1. Schematic illustration for a rechargeable lithium ion battery with LiCoO, cathode, graphite anode and nonaqueous electrolyte.

The obtained curves were similar to those reported in hterature [15]. This indicates that all solid state LiCoO electrode functions as cathode of rechargeable lithium ion battery at relatively high discharge and charge rates. The thickness of... 

The contribution of electric field to lithium transport has been considered by a few authors. Pyun et al argued on the basis of the Armand s model for the intercalation electrode that lithium deintercalation from the LiCoO composite electrode was retarded by the electric field due to the formation of an electron-depleted space charge layer beneath the electrode/electrolyte interface. Nichina et al. estimated the chemical diffusivity of lithium in the LiCo02 film electrode from the current-time relation derived from the Nemst-Planck equation for combined lithium migration and diffusion within the electrode. 

The main cathode material, LiCoO, in the lithium-ion battery has been improved in terms of rate capability and capacity. The rate capability is improved by the control of particle morphology, and high capacity is achieved by increased charge voltage while overcoming safety problem. ... 

Two types of solid solution are known in the cathode material of the lithium-ion battery. One type is that two end members are electroactive, such as LiCo Ni 02, which is a solid solution composed of LiCo02 LiNiO. The other type has one electroactive material in two end members, such as LiNi02 Li2Mn03 solid solution. LiCoO, LiNiQ Mn O, LiCrO, LiMnO and LiFeO are electroactive end members on the other hand, Li MnOg, Li2Ti03 and LiAlO are electrochemically... 

By the way, LiCoO has been used mainly as the cathode material in the lithium-ion battery for mobile phones because of high-energy density. However, the rapid rise in price for the lack of the cobalt resources has promoted the hybridization between the cobalt-based material and the manganese-based material with the spinel structure. Further, it has been confirmed that this hybrid material can have the same energy density as that of the conventional one, so the hybrid-type batteries came onto the market since 2004. It is expected that the share of this type of battery will expand further in the future. 

The battery characteristics, capacities, densities, shapes of the charge/discharge curves, and problems of typical cathode materials, which are used or developed for the lithium-ion battery, are listed in Table 2.1. The LiCoO has more than a 90% share in the market of cathode material for the lithium-ion battery, which is applied to cellular phones and portable computers. It has been used since this battery was developed. Manganese-based materials have a share of residual several percent. 

It is considered to be important to control the atomic ratio of Li/Co in the production of LiCoOj. One of the features of this product is that its ratio is generally less than one. The cathode slurry is prepared by dispersing the conductor and electroactive LiCoOj in the N-methyl-pyrroMone solution containing polyvinylidene fluoride (PVDF). It is unavoidable that some water is contaminated into the slurry. When the unreacted lithium in LiCoO remains as Li O, it reacts with water in the slurry, and the cathode slurry becomes basic. The cathode slurry changes to a gel state in such basic media as a result, the cathode slurry cannot be painted onto the aluminum collector. Therefore, conventional raw LiCoO is washed with warm water in order to prevent gel formation of the cathode slurry. In an example of the product supplied by a company, the pH of 10 wt% LiCoO aqueous dispersion is adjusted to 9.5-11.0. The recommended pH is less than 10.5. This manufacturer supplies LiCoOj with Li/Co < 1, so there is a possibility for making the unreacted lithium salt in the product close to 0. It can be considered that the washing process of raw LiCoOj would be removed for cost reduction. 

A comparison of the transmission electron microscopy (TEM) images between the Al O - and AlPO -coated LiCoO particles is shown in Fig. 10.6. In both cases, the aluminum or phosphorus elements are distributed over the LiCoO surfaces. The possible formation of a solid solution from a reaction between the coating materials and lithium (or even cobalt) during the heat treatment is not ruled out. 

An excess amount of lithium (1.02 mol) was used to compensate for the loss of lithium during firing. The resultant powders showed a Brunauer-Emmett-Teller (BET) surface area of 1 mVg. The process for AlPO coating on the cathode is identical to the LiCoO described above. 

Ohzuku et al. and Amatucci et al. reported that delithiated Li NiOj to x 0 maintained the R3m structure without a monocUnic distortion at a low lithium content, which is unlike LiCoO. Similarly, the XRD patterns of Li Nij jCOj, Mn jO show that its structure at jc 0 (at 4.8 V) remains as R3m. ... 

Development of LiCoO Used for Rechargeable Lithium-Ion Battery... 

The battery characteristic deteriorates when the rechargeable lithium-ion battery is contaminated with water. Naturally, it is desired that the water content in LiCoO used as the positive electrode-active material be controlled below a certain value. Moreover, currently a further decrease in the water content level is demanded by our customers. Although it may be considered that there is no problan because there is a process to make a slurry of the positive electrode-active material and to dry it, it is known that the water in LiCoO consists of both physical adsorption and chemisorptions. Because the water, which has been chemically adsorbed, cannot be removed during this drying temperature, it is important to stop the inclusion of moisture from the manufacturing process. 

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