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Nonspherical LiCoO 2 powders have been synthesized using a two-step drying method. The tap density of the powder obtained is 3.06 g cm −3 , which is remarkably higher than that of spherical LiCoO 2 powders ͑only 2.40 g cm −3 ͒. The LiCoO 2 powder is also characterized by X-ray diffraction ͑XRD͒ and scanning electron microscopy. The XRD analysis shows that the material has a well-ordered layered structure. Initial charge and discharge capacities of 165 and 152 mAh g −1 are obtained between 3 and 4.2 V at a current of 0.2 C rate. LiCoO 2 has been widely used as a major cathode material for lithium-ion batteries ͑LIBs͒ because it has a high operating voltage and energy density and a long cycle life. Further investigation of the cathode material, LiCoO 2 , has been widely reported [1][2][3][4][5][6] to improve its performance for a lithium-ion secondary battery. It has been well recognized that the preparation of the cathode material with a high tap density is extremely important for the manufacture of the composite electrode for commercial Li-ion cells with high-energy densities. To improve the density of LiCoO 2 powders, He et al. and Ying et al. prepared spherical Co͑OH͒ 2 and CoCO 3 powders by the "controlled crystallization method" and "uniform-phase precipitation method," respectively. 7,8 Spherical LiCoO 2 powders were then synthesized by sintering spherical Co͑OH͒ 2 or CoCO 3 powders mixed with Li 2 CO 3 at 750-850°C for 12-16 h. The obtained tap densities are as high as 2.6-2.8 g cm −3 . However, to obtain spherical hydroxide or carbonate precipitate, experimental conditions, such as pH, temperature, and mixing speed, had to be carefully controlled. Also, the preparation procedures were complex and not environmentally friendly due to the use of NH 3 ·H 2 O. Compared with those of spherical LiCoO 2 powders, the preparation procedures of nonspherical powders are much simpler, because it is not necessary to carefully control the pH and the mixing speed. The process is more environmentally favorable because there is no ammonium involved. Furthermore, the nonspherical powders have a large specific surface area and high electrochemical activation. As a result, commercially available LiCoO 2 cathode materials are usually nonspherical powders, whose tap densities are approximately 2.0-2.4 g cm −3 . Basically, the commercial LiCoO 2 are synthesized by mixing the precursor ͓nonspherical Co͑OH͒ 2 obtained by a one-step drying method or Co 3 O 4 obtained by a high-temperature treatment͔ and Li 2 CO 3 and then sintering at a high temperature. The particle size of nonspherical cobalt oxide powders obtained by the one-step drying method is not well distributed, which directly affects the physical property of LiCoO 2 , resulting in a lower tap density of the product. The low tap density of LiCoO 2 cathode materials in turn leads to a low volumetric specific capacity, which seriously limits the energy density of LIBs.8 Therefore, improving the tap density of the nonspherical powders is necessary.In this study, a method is p...

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Electromagnetic theory is used to characterize the magnetization processes in metals and alloys. The analysis shows that the free energy of a phase transformation may be reduced or enhanced by the magnetic field depending on the ratio of the permeability of the old and new phases. This means that the magnetic field can either stimulate or inhibit the nucleation process. The theory is in accord with the experimental results by others and us.