From the initial high pressure L C O (compaction 4. 1, fully charged 4. 1V, 145mAh/g capacity), developed to the first generation of high-voltage LCO (fully charged 4.2V, 155mAh/g capacity) on the IPhone4, and to the second generation of high-voltage LCO (applied to the IPhone5). 1.65 mAh/g capacity above), and the third generation high-voltage LCO system (4.4V full power, close to 1.75 mAh/g capacity) that is being developed and perfected. Although the charging upper limit voltage is only increased by 0. 1V at a time, few domestic cathode material manufacturers have accumulated and made progress in the technology behind it.
The modification of 4.2V in the first stage is relatively easy, and the principle is mainly doping modification. Three or four years ago, foreign companies were industrialized. In the second stage, the process of 4.3/4.4V is more difficult, which requires the combination of bulk doping and surface coating, so the concept of "insulated cathode" has been developed, and a few large companies in the world have realized industrialization.
The metamorphic elements of high-pressure LCO are mainly Mg, Al, Ti, Zr, etc., which are basically published, but the action mechanism of different elements is different. The key of high-end LCO technology lies in what elements are doped, how and how much. Similarly, the difficulty of surface coating lies in what kind of coating is selected first, and then what kind of coating method is adopted and how many coatings are used. Dry doping and coating are the mainstream at present, but some companies carry out wet modification in the precursor stage. According to different doping and coating requirements, optimizing temperature, sintering process and surface reprocessing process are the core technologies of high pressure LCO production. Manufacturers need to choose the appropriate technology route according to their own technology accumulation and economic situation.
The cathode material used for IPad4 lithium battery is different from that used for IPone5. IPhone uses high-pressure LCO with a particle size of 20 microns, and IPad uses a mixture of high-pressure LCO and NMC532 with a particle size of 10 micron (the mixing ratio is 6: 4). Why are the materials of IPhone5 and IPad4 different? The high on/off voltage of mobile phones and the pursuit of high energy density make high-end LCO an inevitable choice for IPhone5. The profit margin of IPad is not as high as that of IPhone, so you can choose lower-cost mixed materials, and you can also use NMC to release higher capacity while reducing the shutdown voltage, killing two birds with one stone.
The actual energy density of IPad4 and IPone5 lithium batteries is almost 230wh/Kg, which is precisely because IPad reduces the shutdown voltage and can make full use of the capacity of NMC in a lower voltage range. LCO and NMC are not simply physically mixed, but briefly sintered at a lower temperature (600 ~ 700℃) after mixing. Due to the mutual diffusion of elements, the gas production of NMC in mixed materials is suppressed to some extent, the storage life at high temperature is also improved, and the safety of LCO is also improved, which can be attributed to synergistic effect. Therefore, it is not difficult to understand that the IPad4 uses the upper limit charging voltage of 4.35V V. ..
The patent of high-voltage LCO was applied by FMC company in Canada, but FMC did not actually produce LCO, but transferred the patent ownership to Umicore in Belgium, and then indirectly licensed it to several companies in the world. No company in China has purchased a license for the use of FMC patents, and no related patents have been published. Due to intellectual property considerations, Apple has designated materials for several lithium battery manufacturers, and domestic cathode material manufacturers are basically excluded from Apple's supply chain. Of course, the domestic smart phone and tablet industry has developed rapidly in the past two years. If it is only the domestic market and there is no export, there is still room for domestic high-voltage LCO. Whether the high-end LCO can develop in China depends on whether the domestic smart phone and tablet industry can really compete with Apple and Samsung.