Impact of Surface Layer Formation during Cycling on the Thermal Stability of the LiNi_0.8Co_0.1Mn_0.1O₂ Cathode

Abstract

In this study, the effects of charge/discharge cycling on the thermal stability of LiNi 0.8 Co 0.1 Mn 0.1 O 2 , a high-Ni cathode material, are systematically investigated. X-ray diffraction measurements show that there is almost no change in the bulk structure of the cathode after cycling. However, X-ray absorption fine structure measurements indicate that Ni in the surface layer is reduced and stable rock-salt structures are formed. Differential scanning calorimetry (DSC) measurements show that the heat generation at the lowest temperature, which can trigger thermal runaway in batteries that use high-Ni cathodes, decreases significantly with the formation of rock-salt structures on the active material surface. This finding indicates that the rocksalt layer on the surface enhances the thermal stability of a high-Ni cathode. The change in the total heat generation with degradation, indicated by DSC measurements, is similar to that in the K-edge of Ni (i.e., the Ni valency), suggesting a strong correlation between the heat generation and crystal structure changes during cycling.

Challenges and opportunities using Ni-rich layered oxide cathodes in Li-ion rechargeable batteries: the case of nickel cobalt manganese oxides

“…178 The formation of the rock-salt layer on the surface of NCM811 is reported to enhance the thermal stability of an NCM cathode with high Ni contents. 179 The change in the total heat generation with degradation suggests a strong correlation between the heat generation and crystal structure changes during cycling, as indicated by differential scanning calorimetry (DSC) measurements and XAS measurements. Studies focusing on the thermal stability of layered NCM materials envisaged the correlation between the thermal stability and its electrochemical performance.…”

Synergistic Effect of Bis(2,2,2-trifluoroethyl) Carbonate and Succinonitrile in Suppressing the Dissolution of Nickel for Performance Improvement of Nickel-Rich Lithium Metal Batteries

“…7 To improve battery specific energy and power density of highvoltage LIBs, nickel-rich layered transition metal (TM) oxide cathode materials have been the top priority both in academic research and commercial exploitation, such as Li-Ni 1−x−y Co x Mn y O 2 (NCM) and LiNi 1−x−y Co x Al y O 2 (NCA). 8,9 It has been confirmed that increasing the nickel content in the cathode can help increase battery capacity. 10 However, higher nickel content in the cathode would lead to a decrease in cycle life and thermal stability as a result of Ni 2+ and Ni 3+ ion dissolution accelerated by the nonstoichiometric Li 1−x Ni 1+x O 2 crystal structure in the electrolyte during the charging process.…”

“…Lithium-ion batteries (LIBs) have been extensively used in our daily life due to their high energy density and long life. − Despite the great success of industrialization, the booming power demands of energy storage capability in consumer markets still urgently push forward the progress of battery energy density and durability, especially in particular application fields. , The energy storage performance of LIBs depends on the collaborative property of key components including cathode, anode, electrolyte, and separator . To improve battery specific energy and power density of high-voltage LIBs, nickel-rich layered transition metal (TM) oxide cathode materials have been the top priority both in academic research and commercial exploitation, such as LiNi 1– x – y Co x Mn y O 2 (NCM) and LiNi 1– x – y Co x Al y O 2 (NCA). , It has been confirmed that increasing the nickel content in the cathode can help increase battery capacity . However, higher nickel content in the cathode would lead to a decrease in cycle life and thermal stability as a result of Ni 2+ and Ni 3+ ion dissolution accelerated by the nonstoichiometric Li 1– x Ni 1+ x O 2 crystal structure in the electrolyte during the charging process.…”

Thermoresponsive Electrolytes for Safe Lithium‐Metal Batteries

“…The chemical crosstalk between the oxidative gas and the electrolytes/reductive anode (especially Li-metal anode), generates tremendous heat and eventually leads to the thermal safety risks of working batteries. [13][14][15] (4) Internal short circuit is another major heat resource of batteries during thermal safety risks. [16,17] Both the cathode and anode directly contact each other due to the failure of separator, leading to the enormous and uncontrolled short-circuit current and the massive joule heat.…”