The patent describes Methods of preparing electrodes for use in rechargeable battery using two lithiation steps, including a first lithiation step is conducted at higher temperatures than the second lithiation step. The patent relates to rechargeable battery systems, and more specifically, to methods for manufacturing nickel-cobalt-aluminum (NCA) electrodes for such systems, as well as to the manufacture of rechargeable battery cells and, more specifically, to the formation of rechargeable battery cells after assembly and testing.
Rechargeable batteries are an integral component of energy-storage systems for electric vehicles and for grid storage. Many rechargeable battery systems rely on lithium compounds for one or both electrodes. In such systems, electrodes made from lithium compounds are used as an integral part of the battery system.
Standard methods of making electrodes for inclusion in rechargeable battery systems include a standard NCA lithiation process and a standard single crystal NMC lithiation process. This has several disadvantages that lead to the production of materials with poorer electrochemical properties.
Tesla developed its methods of making electrodes for inclusion in rechargeable battery system. The patent reads:
"This disclosure includes methods of preparing electrode materials for use in rechargeable batteries. The present method allows for single crystal NCA materials to be produced without impurities which lead to“ dead mass "in electrodes. A mixture of NCA (OH) 2 and LiOHeThO is prepared with a Li: OM ratio less than 1.0. It should be noted that the Li: OM ratio is the ratio of the amount of lithium in the lithiated material to the amount of other metals in the lithiated material. This mixture is first heated to a temperature large enough to allow for single crystal growth. Because the Li: OM ratio is less than 1.0, the formation of L15 AIO4 is avoided. However, because the Li: OM ratio is less than 1.0, the product is Lii-z (Nii -x-yCoxAly) i + z02 with z> 0. Such materials have poor electrochemical properties unless z is very near zero. In a second heating a small amount of excess Li, q, is added so that: q> z the second heating is chosen to be lower than that of the first heating so that the Li: OM ratio in the final product approaches 1.0 and that no L15AIO4 is created. In such a way, impurity-free single crystal NCA can be created.
Methods disclosed include include a first lithiation step, one a lithium and an other metal component are present in a first lithium / other metal ratio of less than 1.0 and are sintered at a temperature between 800 and 950 ° C for a time period between 1 and 24 hours to obtain a first lithiated material. The method further includes a second lithiation step, one a lithium and a other metal component are present in a second lithium / other metal ratio and further along the first lithiated electrode material is sintered with additional LiOHTLO at between 650 and 760 ° C for a time period between 1 and 24 hours to obtain a second lithiated material."
A method of preparing an electrode for use in rechargeable batteries, the method comprising the steps of:
FIG. 5 illustrates the percentage of nickel in the lithium layer (determined by x-ray profile refinement using the Rietveld method) after the second lithiation reactions for the first lithiation reaction at 875°C with a Li/OM ratio of 0.95, and subsequent second lithiation reactions, and the result of a first lithiation reaction at 850°C with a Li/OM ratio of 0.975 and subsequent second lithiation reactions. It is desired to have the percentage of Ni in the lithium layer as small as possible.
New electrodes are likely to allow Tesla to achieve a better energy density than NMC batteries.
The company's progress in creating a 1 million-mile battery is highly visible. Tesla, who has been developing his batteries for several years, and recently began testing (the company has already tested the prototype of the cell as part of the secret project Roadrunner), is likely to present something amazing at Battery Day, which is due to take place in the near future.
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