The most studied cathode material is LiCoO2, LiNiO2, LiMn2O4 and above, three kinds of laptop battery materials and derivatives, such LiNi0.8Co0.2O2, LiNil/3Co1/3Mnl/302 so.
LiCoO2 is the only large-scale commercialization of the cathode material, at present more than 90% of the commercialization of lithium-ion battery using LiCoO2 as the cathode material. LiCoO2 research is relatively mature, comprehensive performance excellent, but expensive, low-capacity, highly toxic, there are some security issues.
LiNiO2 lower cost, higher capacity, but the preparation of difficulties, material properties of consistency and reproducibility is poor, there are more serious security problems.
LiNil/3Co1/3Mnl/302 can be seen as LiNi02 and LiCoO2 solid solutions, the advantages of both LiNiO2 and LiCoO2 once been considered the most likely to replace the new LiCoO2 cathode material, but there are synthetic conditions are harsh (requires oxygen atmosphere ), security, poor, shortcomings, comprehensive performance could be improved; same time, because ThinkPad T60 with more expensive Co, and higher cost.
Spinel LiMn2O4 low cost, safety, good, but especially the high-temperature cycle performance cycle performance is poor, in the electrolyte have a certain solubility, poor storage performance.
The new ternary nickel-cobalt composite oxides of lithium manganese oxide (LiNil/3Co1/3Mnl/302) material focused on the LiCoO2, LiNiO2, LiMn2O4 and other materials of their respective advantages: cost and LiNil/3Co1/3Mnl/3O2 very, reversible capacity, structural stability, security, good, ranging between LiNi0.8Co0.2O2 and LiMn2O4, recycling performance, synthetic easy; but with more expensive Co, and higher cost.
Sino-high-capacity, high-power 40Y6797 lithium-ion batteries, the cathode material cost, high performance, security is very important. The LiCoO2, LiNiO2, LiMn2O4 cathode material and its derivatives still can not meet the requirements. Therefore, the research and development can be used for medium-capacity, high-power lithium-ion battery cathode materials become the new hot spots.
Orthogonal structure of olivine LiFePO4 cathode material has gradually become a new hotspot at home and abroad. Preliminary studies indicate that concentration of this new type of cathode material LiCoO2, LiNiO2, LiMn2O4 and its derivatives cathode material of their respective advantages: non-precious elements, low-cost raw materials, resources and greatly enriched; moderate operating voltage (3.4V); platform features is good, voltage is very smooth (can be comparable with the regulated power supply); theory, large capacity (170mAh / g); structural stability, security, excellent performance (O and P to a solid combination of strong covalent bond, and the material is difficult to decompose oxygen evolution); high-temperature performance and thermal stability, much better than the other known cathode material; cycle of good performance; charging smaller in size, and carbon anode materials with the volume when the effect of good; with most of the electrolyte system, good 40Y6799 compatibility, storage, good performance; non-toxic, in order to truly green materials. With LiCoO2, LiNiO2, LiMn2O4 and its derivatives compared with cathode material, LiFePO4 cathode material cost, high-temperature performance, safety has obvious advantages, is expected to become a high-capacity, high-power lithium-ion battery cathode material of choice. The industrialization of the material and wider application of lithium-ion batteries to reduce costs and improve battery safety, expansion of lithium-ion battery industry, the promotion of large-scale lithium-ion batteries, high-power technology of great significance, will make lithium-ion batteries at CUHK Capacity UPS, medium and large storage batteries, power tools, electric vehicle applications a reality.
However, lithium iron phosphate, there are two obvious shortcomings, first, the low electrical conductivity, resulting in poor high-rate charge and discharge performance, the actual specific capacity is low; second is accumulation of low density, resulting in lower volume than the capacity. These two shortcomings hinder the practical application of the material.
At present, people's research focus on solving the low conductivity of phosphoric acid or lithium in this area, and has made significant progress. Improvement measures taken are:
(1) to lithium iron phosphate particles within the mixed conductive carbon material or conductive metal particles, or to the FRU 92P1139 lithium iron phosphate particles coated conductive carbon materials to improve the electronic conductivity of materials.
(2) to lithium iron phosphate (1iPePO4) mixed with a small amount of impurities in the lattice of metal ions such as Mg2 +, Ti4 +, Zr4 +, Nb5 +, to replace part of the location of Li + wide so that lithium iron phosphate into the intrinsic semiconductor n type or p-type semiconductor, significantly increased the electronic conductivity of the material.
(3) to the incorporation of lithium iron phosphate impurities such as Mn2 +, Fe2 + to replace a part of the position, increasing the lattice parameters of lithium iron phosphate to improve lithium ion conductivity of the material.
(4) using sol-gel method, liquid phase synthesis method, and other new technology, reducing the grain size of the lithium iron phosphate, and even synthesis of nano-lithium iron phosphate as much as possible to shorten the distance the spread of Li +, the apparent enhanced the material The lithium ion conductivity and material utilization.
However, the accumulation of low-density FRU 92P1141 lithium iron phosphate has been the shortcomings of people's neglect and avoid, has not yet been resolved, impede the practical application of the material. Theoretical density of lithium cobalt oxide for the 5.1g/cm3, commodity drilling the tap density of lithium is generally 2.0-2.4g/cm3; while the theoretical density of lithium iron phosphate is only 3.6g/cm3, in itself than lithium cobalt oxide be much lower. To enhance conductivity, it is mixed with conductive carbon materials, but also significantly reduce the packing density of the material, making the general carbon-doped lithium iron phosphate of the tap density is only 1.0-1.2g/cm3. Such a low packing density makes the volume ratio of lithium iron phosphate capacity is much lower than that of lithium cobalt oxide, made from the battery size will be very large, not only devoid of virtue, and difficult to apply to the actual.
Therefore, improving the packing density of lithium iron phosphate and volume than the capacity of lithium iron phosphate Practical decisive. Powder particle morphology, particle size and its distribution directly affect the packing density of the material. For example, Ni (OH) 2 is used for nickel-hydrogen batteries and nickel-cadmium battery cathode material. Previously, people used sheet of Ni (OH) 2, the tap density is only 1.5-1.6g/cm3;
Currently used spherical Ni (OH) 2 of the tap density of up to 2.2-2.3g/cm3; spherical Ni (OH) 2 has largely replaced the sheet of Ni (OH) 2, significantly FRU 92P1137 improved nickel-metal hydride batteries and nickel - cadmium battery energy density. The reference laboratory of high-density spherical Ni (OH) 2 of the research results, the successful development of lithium-ion battery cathode material for high-density spherical series, including the LiCoO2, liMn2O4, LiNi0.8Co0.2O2, LiNil/3Co1/3Mnl/3O2 so. One LiCoO2, LiNi0.8Co0.2O2 the tap density, can be 2,9 g/cm3, much higher than the commercialization of such material. Research and practical applications show that not only has the accumulation of spherical high-density products, the volume ratio of the outstanding advantages of large capacity, etc., but also has excellent mobility, dispersion and processability * can be very beneficial to production of cathode materials with * pulp and the electrode film of the coating, to improve the quality of electrodes; Furthermore, compared with irregular particles, the rules easier for coating the surface of spherical particles complete, uniform, solid layer of modification, the spherical surface modification products and more hope to further improve the overall performance.
On this basis, we propose: Ball of a 02K6651 lithium-ion battery cathode materials development. Reported at home and abroad. LiFePO4 cathode material are formed by irregular particles, the packing density of powder materials and energy and lower density. Therefore, this project seeks to spherical particles of LiFePO4 material by spherical particles to increase the packing density of the material and the volume ratio of capacity; on this basis, to play a spherical surface, coated materials, easy-to-edge, and further through the surface of spherical particles modified to improve overall performance materials. In the spherical particles of LiFePO4 materials and surface modification process, the full reference, absorption, taking advantage of people in improving the conductivity of lithium iron phosphate has made outstanding achievements; the final preparation of a spherical, high bulk density, high-volume ratio capacity, high conductivity of LiFePO4 cathode material, so that it can use in medium to large capacity, high-power lithium-ion batteries, to promote the industrialization of the material.
At present, research using divalent or trivalent ferric iron salts, phosphoric acid or phosphates, ammonia as raw materials, by controlling the synthesis of high-density 02K6928 spherical crystallization technique iron phosphate precursor, and then with the lithium source, carbon source of mixed heat treatment, through the carbothermal reduction synthesis of high-density spherical carbon-doped lithium iron phosphate. The lithium iron phosphate powder material dispersed by a single spherical particle composition, particle size 5-10um, Bulk density (tap density up to "-1.8g/cm3), good fluidity and processability of good performance, the reversible capacity 140MLNg.
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