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Acid treatment process for preparing cathode material of a rechargeable lithium ion battery and product obtained by it. Disclosure Number: IPCOM000249174D
Publication Date: 2017-Feb-08

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Acid treatment process for preparing cathode material of a rechargeable lithium ion battery and product obtained by it.

This disclosure relates to a process applied during the preparation of cathode materials for rechargeable lithium battery.  More particularly, this process aims to cut down lithium carbonate content of cathode active materials and employs an acid solution treatment to realize this purpose.

In view of the scarcity of fossil fuels and in order to reduce greenhouse gas emissions to fight global warming, eco-friendly and fuel-efficient technologies are highly demanded and are necessary in automotive applications. The use of rechargeable lithium ion batteries is one of the most promising and available solutions, due to their relatively high energy density, fast recharge capability and high discharge power. The main application of rechargeable lithium ion batteries in the automobile industry focuses on hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs) and electric vehicles (EVs). From HEVs to EVs, the degrees of hybridization and electrification increase, at the same time the requirement of batteries having a high energy density rises, while the demand for high power output decreases. Next generation rechargeable lithium batteries are expected to have an improved energy density. Previously the majority of rechargeable lithium batteries used LiCoO2 (LCO) as cathode material. However, for vehicle applications LiCoO2 is not sustainable anymore due to limited cobalt resources – as already today about 30% of the earth’s available cobalt is used for batteries, according to the Cobalt Development Institute. The scarce cobalt resources cannot satisfy the large demand in the automotive market of cathode material at a reasonable cost. Today, a potential alternative for LiCoO2 is the so-called NCM cathode material. An example of NCM material is “523” cathode materials, generally referring to Li1+xM1‑xO2,with M= Ni0.5Co0.2Mn0.3,or “622” with M=Ni0.6Co0.2Mn0.2. The NCM cathode materials contain less cobalt, since it is replaced by nickel and manganese that are cheaper than cobalt and that are relatively more abundant. Additionally, the energy density of some NCM cathode materials meets or even exceeds that of LiCoO2.

An NCM cathode material can roughly be understood as a solid state solution of LiCoO2, LiNi0.5Mn0.5O2 and LiNiO2. In LiNi0.5Mn0.5O2 Ni is divalent and in LiNiO2 Ni is trivalent. At 4.3 V the nominal capacity for LiCoO2 and LiNi0.5Mn0.5O2 is about 160 mAh/g, against 220 mAh/g for LiNiO2. The reversible capacity of any NCM compound can be roughly estimated from these given capacities. For example NCM“622” can be understood as 0.2 LiCoO2 + 0.4 LiNi0.5Mn0.5O2 + 0.4 LiNiO2. Thus the expected capacity equals 0.4 x 160 + 0.6 x 220 = 184 mAh/g. Similarly 811 can be understood as 0.1 LiCoO2 + 0.2 LiNi0.5Mn0.5O2 + 0.7 LiNiO2, yielding 202 mAh/g. The fraction of 3-valent Ni is called “Ni excess”...