In situ analysis of gas evolution in liquid- and solid-electrolyte-based batteries with current and next-generation cathode materials

Abstract

The operation of combined mass spectrometry and electrochemistry setups has recently become a powerful approach for the in situ analysis of gas evolution in batteries. It allows for real-time insights and mechanistic understanding into different processes, including battery formation, operation, degradation, and behavior under stress conditions. Important information is gained on the safety and stability window as well as on the effect of protecting strategies, such as surface coatings, dopings, and electrolyte additives. This review primarily aims at summarizing recent findings on the gassing behavior in different kinds of liquid- and solid-electrolyte-based batteries, with emphasis placed on novel cathode-active materials and isotope labeling experiments, to highlight the relevance of in situ gas analysis for elucidation of reaction mechanisms. Various instrumental and experimental approaches are presented to encourage and inspire both novices and experienced scientists in the field. Graphical abstract

P2-type layered high-entropy oxides as sodium-ion cathode materials

“…Figures 8 and S4 of the supporting information show the correlation between the voltage profiles and the gas evolution rates for the most evolved gases, hydrogen (H 2 , m/z = 2) and carbon dioxide (CO 2 , m/z = 44). The origin of these gases can be inferred from the analogy with gas evolution in LIBs, where CO 2 can originate either from chemical oxidation of the electrolyte associated with the release of lattice oxygen or from electrochemical oxidation of the electrolyte (or, mainly during the first cycle, from surface carbonates) [39,[59][60][61][62]. Since the released O 2 in the case of layered oxide cathode materials for LIBs is apparently highly reactive in nature, it is rarely detected directly as molecular oxygen, but indirectly as the reaction product CO 2 [63,64].…”

Gas Generation in Lithium Cells with High-Nickel Cathodes and Localized High-Concentration Electrolytes

“…High-nickel cathodes experience runaway reactions at lower temperatures and with greater heat release, exacerbating the issue. Similarly, during typical high-voltage operation or in the event of overcharging, gases are released through the reaction of the electrolyte with the cathode. , Gas bubbles can accumulate in the cathode and inhibit the transport of lithium ions, can depressurize pouch cells and increase contact resistance, and in extreme cases can cause cell rupture.…”

“…Nail penetration tests, differential scanning calorimetry, and direct combustion have all revealed the reduced flammability of LHCE relative to the conventional carbonate electrolyte. ,, While it is intuitive to think that the stability benefits of LHCE extend to gas release, direct measurement of gas release in an LHCE has yet to be carried out. One technique for doing so is known as online electrochemical mass spectroscopy (OEMS) . OEMS uses mass spectroscopy to sample the gas inside of a cell during operation, so that both the composition and total quantity of evolved gas can be measured.…”

“…One technique for doing so is known as online electrochemical mass spectroscopy (OEMS). 6 OEMS uses mass spectroscopy to sample the gas inside of a cell during operation, so that both the composition and total quantity of evolved gas can be measured. We employ here the OEMS to compare the gas generation in cells with a highnickel cathode and an LHCE with that in cells containing a typical carbonate electrolyte, for the first time.…”

Advances and challenges in multiscale characterizations and analyses for battery materials

“…For example, in layered oxide cathodes, an irreversible phase transition to a spinel-like or disordered rock-salt phase at the surface during high voltage charging hinders the transport of Li ions, thereby increasing the impedance of the battery cell [9][10][11]. Often, irreversible oxygen (O 2 ) evolution from the cathode lattice or CO 2 evolution by electrolyte decomposition degrades the cycling stability of the battery [12,13]. In classical liquid electrolyte systems, and even more so in solid-state battery systems, the formation of unstable interphases between both cathode/electrolyte and anode/electrolyte during charging-discharging cycles is a key challenge to overcome [4,[14][15][16].…”