Electrochemical Degradation Mechanism and Thermal Behaviors of the Stored LiNi_0.5Co_0.2Mn_0.3O₂ Cathode Materials

Abstract

The degradation mechanism of the stored LiNiCoMnO (NCM523) electrode has been systematically investigated by combining physical and electrochemical tests. After stored at 55 °C and 80% relative humidity for 4 weeks, the NCM523 materials are coated with a layer of impurities containing adsorbed species, LiCO and LiOH, resulting in both the weight gains of the materials and the electrochemical performance deterioration of the electrode. The impurities generated in air will react with the electrolyte and instantly turn into Li POF and other species containing the decomposition products of electrolyte when the stored NCM523 materials are soaked into the electrolyte, causing the charge potential plateau and the impedance to ascend. For the stored NCM523 electrodes, the huge and changeable impedance deteriorates the discharge capacity in the first 10 cycles and the discharge capacity will slowly recover and stabilize within 10 cycles when charging/discharging in 0.1 or 0.2 C. The thermal stability of the stored NCM523 materials get slightly better due to the relatively lower delithiated state after charged to 4.3 V.

Surface/Interface Structure Degradation of Ni‐Rich Layered Oxide Cathodes toward Lithium‐Ion Batteries: Fundamental Mechanisms and Remedying Strategies

“…Zhao and co‐workers demonstrate that three kinds of new components grow on the surface of the NCM622 stored at 55 °C and 80% relative humidity involving the absorbed species, LiOH/Li 2 CO 3 impurities and delithiation layer (Figure b), which together take responsibility for the deterioration of its electrochemical properties. Strikingly, the nearly identical result is achieved from the investigation of NCM523 after stored at 55 °C and 80% relative humidity for 4 weeks . Consistently, the adventitious Li 2 CO 3 , which will impede ionic and electronic transport, also forms on the NCA particle surface during exposure to air through the reaction with atmospheric CO 2 .…”

“…Strikingly, the nearly identical result is achieved from the investigation of NCM523 after stored at 55 °C and 80% relative humidity for 4 weeks. [101] Consistently, the adventitious Li 2 CO 3 , which will impede ionic and electronic transport, also forms on the NCA particle surface during exposure to air through the reaction with atmospheric CO 2 . [102] Specifically, the thickness and structure of the Li 2 CO 3 layer, which enormously depends on the exposure time, temperature, and CO 2 /H 2 O partial pressures, determine the electrochemical cycle, lattice parameter, and Li composition distribution in the underlying NCA during the first charge (Figure 11c).…”

“…Undesirably, the original O3-type layered structure of the Ni-rich cathodes, particularly at the surface/interface location, are susceptible for the irreversible structure degradation resulting mainly from the unfavorable migration of TM ions (cation mixing), [86,87] continuous erosion by the hydrofluoric acid (HF) [88][89][90][91][92] and the formation of stress-induced microcracks, [39,[93][94][95][96][97] as well as the structural instability arising from the moisture. [34,[98][99][100][101][102] These phase distortions are highly detrimental to the Li + /electrons migration across the interface, and consequently lead to the performance deterioration of LIBs. In the subsection, we mainly focus on the latest progress with regard to the fundamental origins of surface/interface structure degradation under different conditions.…”

One-Spot Facile Synthesis of Single-Crystal LiNi0.5Co0.2Mn0.3O2 Cathode Materials for Li-ion Batteries

“…The low CE and rapid decrease of the capacity for the initial cycles may be caused by the parasitic reactions, which is due to the formation of a solid electrode interface (SEI) at the surface of cathode materials. 40 The cycling performances of NCM523 are comparable with the commercial materials with the morphology of the secondary particles. 41 The cycling performances of NCM523 in the voltage range from 2.0 to 4.2 V at 0.1C are presented in Figure S1.…”

Surface double coating of a LiNiaCobAl1−a−bO2(a> 0.85) cathode with TiOxand Li2CO3to apply a water-based hybrid polymer binder to Li-ion batteries

“…However, it should be also noted that Li 2 CO 3 is electrochemically insulating which may block the electronic transport of the Li 2 CO 3 -coated cathode materials and consequently leads to the capacity degradation due to the accumulation of Li 2 CO 3 in the interface between the cathode particle surface and electrolyte. 22,23 Thus, a suitable Li 2 CO 3 layer coating is desirable. In addition, as mentioned later based on our examination on the waterresistance of NCA cathode particles coated with Li 2 CO 3 layer by the CO 2 gas treatment, CO 2 gas-treated NCA samples could not exhibit full charge/discharge capacities because they suffered from a small surface damage (surface dissolution) by contacting with water owing to the uncomplete coating of the whole surface of NCA particles by the Li 2 CO 3 layer, i.e., the NCA surface coating only by the Li 2 CO 3 layer was not adequate for the present purpose.…”