Valence Effects of Fe Impurity for Recovered LiNi_0.6Co_0.2Mn_0.2O₂ Cathode Materials

Abstract

Iron impurities are generally included in the obtained leaching liquor solution during the hydrometallurgical recycling method of spent lithium-ion batteries (LIBs) due to the usage of iron in battery casings and machinery parts of recycling equipment, which would definitely affect the physical and electrochemical features of the recovered active materials. In this work, the effects of iron impurity with different valence states (Fe2+ and Fe3+) and gradient concentrations (0.2, 1.0, and 5.0 at. %) for the obtained LiNi0.6Co0.2Mn0.2O2 (NCM622) cathodes are fully studied. It is found that Fe3+ impurity could easily lower the tap density and average size of NCM622 particles and even introduce some impurity phases in the NCM622 structure at high concentration (5.0 at. %), leading to much lower specific capacity, worse rate capability, and cycling performance of the Fe3+-based NCM622 cathode. On contrast, with certain concentrations of Fe2+ impurity (0.2 and 1.0 at. %), the NCM622 cathode material exhibits comparable and much better electrochemical properties compared with the virgin NCM622 materials. Based on these results, the valence of Fe impurity should be considered and controlled as well as its concentration during the recycling process design for spent LIBs.

Toward practical lithium-ion battery recycling: adding value, tackling circularity and recycling-oriented design

“…Al, Cu and Fe are well-controlled, although these impurities can be beneficial in boosting electrochemical performance as a dopant. [155][156][157][158][159] For example in low dopant quantities, Fe improves cycle stability of LiNi 1/3 Mn 1/3 Co 1/3 Fe 0.01 O 2 , most likely via suppressing active material dissolution. However at high dopant quantity, cation mixing among Fe 3+ /Ni 2+ /Li + results in poor rate performance, and a decreased discharge capacity.…”

Organic Electrolytes Recycling From Spent Lithium‐Ion Batteries

“…So far, there are three major recycling methods that have been fully studied, including hydrometallurgy, pyrometallurgy, and direct recycling methods, among which the first two processes have been applied in industrial scale while the last one is still in lab scale. [ 19 , 20 ] Due to high amount of valuable Li, Co, and Ni metals contained in cathode including lithium cobalt oxide (LiCoO 2 , LCO) and lithium nickel manganese cobalt oxide (LiNi x Co y Mn 1– x–y O 2 , NCM), all the recycling methods are mainly focused on the recovery of cathode materials in spent LIBs, especially the current industrial technologies. [ 21 , 22 , 23 ] Other components, such as the graphite, binders, separators, organic electrolytes, and additives, are always burnt or abandoned in slag, which leads to huge emission of greenhouse gases and dust, causing serious environmental pollution.…”

The Effects of Phosphate Impurity on Recovered LiNi0.6Co0.2Mn0.2O2 Cathode Material via a Hydrometallurgy Method

“…The possible impurities in leaching solution can be categorized into three groups: cations, insoluble particles, and anions. Cation impurities such as Al 3+ , , Fe 3+ , and Cu 2+ , have drawn extensive attention in the past. Based on our previous work, insoluble carbon is determined to be a negative factor in hydrometallurgical recycling .…”