Principal Factors of Carbon Conductive Agents that Contribute to the Gas Formation in High-Voltage Cathode Systems

Abstract

The interfacial reactions, especially the gas evolution, between carbon conductive agents and the electrolyte at the positive electrode in high-voltage batteries (potentials over 4.5 V) have been investigated. The amount of gas generated was quantified for various conductive agents: acetylene black (AB), furnace black, specially customized AB, and graphite (GR). The experiments revealed that in the high-voltage system, the specific gas evolution was induced by both the cathode active material and the conductive agent, with the carbon conductive agents resulting in the generation of 8 to 15 times more gas than the cathode active material LiNi 0.5 Mn 1.5 O 4 (LNMO) itself. The high-voltage properties of the carbon conductive agents, such as the anion intercalation and self-discharging properties, were evaluated for each carbon electrode. The results implied the existence of a local battery composed of the conductive agent and LNMO; this redox couple appears to play a key role in the gas evolution.

Enabling high areal capacity for Co-free high voltage spinel materials in next-generation Li-ion batteries

“…The Coulombic efficiency on each cycle of the CA-3 electrode is also higher than the other two. It is worth noting that among all three conductive agents, CA-3 exhibits the smallest specific surface area, which can help to suppress side reactions during the high-voltage region [38]. Therefore, CA-3 was chosen for the rest of the study due to the best compatibility with LNMO materials.…”

Dynamic behaviour of interphases and its implication on high-energy-density cathode materials in lithium-ion batteries

“…Further, the passivation effect of the carbon-driven CEI in simple LiPF 6 /EC-DEC solutions is far from ideal. The anodic instability of conductive carbon, including PF 5 − intercalation 30 44 45 and direct oxidation 31 at voltages approaching 5 V vs Li/Li + , also becomes detrimental to cyclability. Modifications on the electrolyte can produce more robust CEIs 4 28 29 , but the detailed functioning mechanisms of these changes are not well understood.…”

Understanding the Conductive Carbon Additive on Electrode/Electrolyte Interface Formation in Lithium-Ion Batteries via in situ Scanning Electrochemical Microscopy

“…The passivation role of carbon black for the Ni-rich electrodes has been considered between 3.0V and 4.5V, suggesting that the organic complexes generated on carbon migrate across the active material's surface to suppress the unwanted interfacial reactions to certain extent (Li et al, 2017a). In addition, the dynamic evolution of interface by the mass transfer between carbon black and active material was observed (Li and Manthiram, 2019); However, the passivation effect of conductive carbon lose stability at extreme potentials (>4.5 V), which is mainly due to (de)intercalation of anions, irreversible electrolyte oxidation and degradation of conductive carbon (Zheng et al, 2013;Li et al, 2014;Qi et al, 2014;Kajiyama et al, 2015;Metzger et al, 2015;Younesi et al, 2015;He et al, 2016;Scipioni et al, 2016).…”

“…The interface formation process was examined in the lowpotential and high-potential regions, with the EEI termed as solid electrolyte interface (SEI) and cathode electrolyte interface (CEI), respectively. The electrode was prepared with the commonly used conductive carbon additive Super P and binder polyvinylidene fluoride (PVDF) without any active material (Zheng et al, 2013;Li et al, 2014;Qi et al, 2014;Kajiyama et al, 2015;Metzger et al, 2015;Younesi et al, 2015). The dynamic evolution of the interfaces was observed with in situ Scanning Electrochemical Microscopy (SECM).…”