Reactivity of Succinic Anhydride at Lithium and Graphite Electrodes

Abstract

Succinic anhydride (SA) is an useful electrolyte additive for high voltage cathodes but has also a negative impact on graphite (Gr) or Li anodes. For this reason, the Li/electrolyte and Gr/electrolyte interfaces were investigated at 20 • C and 45 • C using half or symmetrical cells. When SA is added at 1% by weight to the electrolyte (alkylcarbonate mixture + LiPF 6 ), an increase in the Li/Li cell impedance at 20 • C occurs owing to the formation of a resistive solid electrolyte interphase (SEI), composed of an inorganic inner layer and an organic outer layer, whereas at 45 • C or in absence of SA, the interphase is more inorganic in nature. The reversible capacity of graphite, cycled in Gr/Li half-cells in the presence of SA, is very low at 20 • C but almost ten times larger at 45 • C. Cycling symmetrical Gr/Gr cells at 45 • C indicates that Gr capacity is lower in the presence of SA in connection with the presence of an organic and polymer rich SEI. GC-MS analysis of the electrolyte after cycling shows that ethylene glycol bis-(alkylcarbonate) derivatives disappear when SA is present, owing to the ability of SA to react with lithium alkoxides to yield oligopolyester. Lithium ion batteries (LIBs) are a reliable way to store electric energy, with high gravimetric and volumetric energy density, which allows their application in nomad systems including electric and/or hybrid vehicles. However, electric vehicles range is unsuitable for most of the consumers and, therefore, energy density should be improved. In the past twenty years, many researches have been performed on electrode materials and electrolytes with the aim to enhance battery performance. Use of 5V class positive electrodes (cathodes) is a convenient way to increase LIBs energy density. It explains the development of promising "high voltage" materials like Li 3 V 2 (PO 4 ) 3 , 1 Li 2 CoPO 4 F 2 or the LiNi 0.5 Mn 1.5 O 4 (LNMO) 3 spinel. Nevertheless, the use of new cathodes operating at high voltage leads to the degradation of the battery electrolyte, usually based on a mixture of cyclic and linear alkylcarbonates containing LiPF 6 as salt and functional additives. Unfortunately, standard electrolytes are oxidized on 5 V cathodes and this significantly limits the battery cycling life. From the first cycles, electrolyte components degrade forming by-products, which in turn, can interact with electrodes surface. As an example, a passive layer is formed on graphite (Gr)/electrolyte interface at the first charge. This layer, known as the Solid Electrolyte Interphase (SEI), has a strong impact on the LIBs performances. Electrolyte formulation influences the chemical nature and structure of the SEI. With the aim to improve SEI quality and stability, SEI-forming additives like vinylene carbonate (VC) are generally added to the electrolyte in low amount (less than 5% by weight). These additives are designed to generate a protective passive layer on the active material surface preventing continuous electrolyte decomposition reactions.Whereas additives can be ...

Impact of Silicon/Graphite Composite Electrode Porosity on the Cycle Life of 18650 Lithium-Ion Cell

“…38 The other contributions between 531 and 532.5 eV were related to the SEI organic degradation products. 37,39 Li 1s spectra confirmed the observations spotted on C 1s and O 1s peaks. The lower binding energy peak was related to Li oxides while the other peaks located at ∼54.3 and ∼55.6 eV can be related to Li involved in the SEI (Li carbonates or polyolefins).…”

“…The electrode A-30aF exhibited a peak at ∼282.5 eV, which could be related to the presence of trapped lithium in the graphite part of the active material, which did not appear in the spectrum of A-40aF. The other peaks located at 284.8 and 285.9 eV and 287.5 eV were associated with organic degradation products such as RO–CO 2 –Li or polyolefins and typical of SEI formed on such electrode materials. , Another major difference concerned the high-energy peak in the C 1s spectra: it was related to the presence of Li carbonates. , The O 1s spectrum of the electrode A-30aF exhibited a high-intensity low-energy peak at ∼528.5 eV, which was present on the electrode A-40aF though with a much lower intensity: this peak is evidence of the presence of some Li oxides at the surface of the electrode material . The other contributions between 531 and 532.5 eV were related to the SEI organic degradation products. , Li 1s spectra confirmed the observations spotted on C 1s and O 1s peaks.…”

“…The other peaks located at 284.8 and 285.9 eV and 287.5 eV were associated with organic degradation products such as RO−CO 2 −Li or polyolefins and typical of SEI formed on such electrode materials. 36,37 Another major difference concerned the high-energy peak in the C 1s spectra: it was related to the presence of Li carbonates. 36,37 The O 1s of the electrode A-30aF exhibited a highintensity low-energy peak at ∼528.5 eV, which was present on the electrode A-40aF though with a much lower intensity: this peak is evidence of the presence of some Li oxides at the surface of the electrode material.…”

“…36,37 Another major difference concerned the high-energy peak in the C 1s spectra: it was related to the presence of Li carbonates. 36,37 The O 1s of the electrode A-30aF exhibited a highintensity low-energy peak at ∼528.5 eV, which was present on the electrode A-40aF though with a much lower intensity: this peak is evidence of the presence of some Li oxides at the surface of the electrode material. 38 The other contributions between 531 and 532.5 eV were related to the SEI organic degradation products.…”

Synergistic Dual‐Additive Electrolyte for Interphase Modification to Boost Cyclability of Layered Cathode for Sodium Ion Batteries

“…The increase in OCO containing species is most likely the decomposition product of SA via open‐ring reaction on the cathode surface. [ 14 ] Moreover, from the O 1s spectra, it is obvious the CEI formed in the electrolyte with FEC‐SA shows higher proportion of CO to CO than that with FEC, which is probably due to the open ring reaction of SA forming a OCO containing species (possibly RCOONa). [ 8d,15 ]…”