High Density Lithium Cobalt Oxide for Rechargeable Batteries

Abstract

The disclosure relates to positive electrode material used for Li-ion batteries, a precursor and process used for preparing such materials, and Li-ion battery using such material in its positive electrode. The disclosure describes a higher density LiCoO₂ positive elecdtrode material for lithium secondary batteries, with a specific surface area (BET) below 0.2 m²/g, and a volumetric median particle size (d50) of more than 15 μm. This product has improved specific capacity and rate-capability. Other embodiments of the disclosure are an aggregated Co(OH)₂, which is used as a precursor, the electrode mix and the battery manufactured using above-mentioned LiCoO₂.

Description

CROSS REFERENCE[0001]This application is a divisional of U.S. patent application Ser. No. 12 / 665,428, filed Apr. 1, 2010, which is a national stage application of PCT / EP2008 / 004629, filed Jun. 10, 2008, which claims priority to European Patent Application No. 07012781.6, filed Jun. 29, 2007, and to European Patent Application No. 07023548.6, filed Dec. 5, 2007. This application also claims the benefit of U.S. Provisional Application No. 60 / 929,614, filed Jul. 5, 2007.BACKGROUND[0002]The invention relates to positive electrode material used for Li-ion batteries, a precursor and process used for preparing such materials, and Li-ion battery using such material in its positive electrode.[0003]Compared to Ni—Cd and Ni-MH rechargeable batteries, Li-ion batteries boast an enhanced energy density, mainly due to their higher 3.6 V working voltage. Since their commercialization in 1991 by SONY, Li-ion batteries have seen their volumetric energy density increase continuously. In 1995, the capa...

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Benefits of technology

[0038]Another objective of the invention is to provide Li-ion batteries with increased energy density and rate capability. With the product mentioned in the first embodiment, the capacity and rate capability of a cell with certain volume can be increased. Therefore the energy density and rate capability can be improved.

Problems solved by technology

However, in some cases, a high tap density does not guarantee a high electrode density.

However, because of its small primary particle size, and possibly because of voids in the secondary particles, the obtained electrode density is not correspondingly high.

The released O2 easily reacts with organic solvent in the battery electrolyte, resulting in fire or explosion of the battery.

However, the examples clearly show that the inventor did not succeed in manufacturing a lithium cobalt (magnesium) oxide powder having both of: a d50 of more than 15 μm, and a specific surface area (BET) of less than 0.2 m2 / g.

Unfortunately, current LiCoO2 with large primary particle size shows relatively poor rate capability, as shown in JP3394364 and by Chen Yan-bin et al.

Such poor rate capability is considered to be related to the longer Li diffusion path for material with larger primary particle size when Li is removed or reinserted during charge or discharge.

However, current large particle size powders show sub-optimal capacity and rate capability because of the significant Li-excess in their structure.

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