Resolution of Lithium Deposition versus Intercalation of Graphite Anodes in Lithium Ion Batteries: An In Situ Electron Paramagnetic Resonance Study

Abstract

In situ electrochemical electron paramagnetic resonance (EPR) spectroscopy is used to understand the mixed lithiation/deposition behavior on graphite anodes during the charging process. The conductivity, degree of lithiation, and the deposition process of the graphite are reflected by the EPR spectroscopic quality factor, the spin density, and the EPR spectral change, respectively. Classical over‐charging (normally associated with potentials ≤0 V vs. Li+/Li) are not required for Li metal deposition onto the graphite anode: Li deposition initiates at ca. +0.04 V (vs. Li+/Li) when the scan rate is lowered to 0.04 mV s−1. The inhibition of Li deposition by vinylene carbonate (VC) additive is highlighted by the EPR results during cycling, attributed to a more mechanically flexible and polymeric SEI layer with higher ionic conductivity. A safe cut‐off potential limit of +0.05 V for the anode is suggested for high rate cycling, confirmed by the EPR response over prolonged cycling.

Room-Temperature Quantitative Quantum Sensing of Lithium Ions with a Radical-Embedded Metal–Organic Framework

“…These observations point toward radical–Li + hyperfine interaction, indicating close contact between Li + in the MgHOTP pores and the negatively charged atomic sites of the delocalized radicals as a result of Coulombic attraction. This hypothesis is corroborated by previous computational and crystallographic studies on alkali metal complexes with HHTP and catecholate derivatives. − …”

“Pulverization–Reaggregation”-induced in situ pore expansion in carbon for fast potassium storage

“…The Lorentz line of CNSs is centered at 3508 G with g-value ¼ 2.0027, corresponding to the unpaired electrons on p-conjugated carbon atoms. 37,38 The signicantly enhanced peak intensity from 500 to 1100 C indicates the increased concentration of carbon defects, which is ascribed to the etching effect in the carbon matrix of in situ pulverization-reaggregation of basic magnesium carbonate. The mechanism of C-defect generation in carbon is shown at the bottom of to produce more C defects due to the reaggregation of MgO nanoparticles.…”

An overview of solid-state electron paramagnetic resonance spectroscopy for artificial fuel reactions

“…EPR techniques have proven successful in studying battery systems via both in situ and operando setups, 34 which is unsurprising given that the paramagnetic metals that serve as anodes have long been studied by EPR. 24 , 35 , 36 , 37 , 38 , 39 , 40 Since EPR can be used to study the coordination environment of paramagnetic atoms, it can be used as a measure of the porosity of alkali metal deposits in batteries that contribute to battery degradation 35 , 36 , 37 or how Li interacts with electrode materials. 39 , 40 Transition metal oxidation states common in electrode materials are also good targets for EPR, and paramagnetic species have been reported for Ru-, 41 V-, 42 , 43 Co-, 44 , 45 Mo-, 46 Mn/Ni-, 47 , 48 , 49 , 50 , 51 and Cu-containing 52 , 53 electrodes.…”

“… 24 , 35 , 36 , 37 , 38 , 39 , 40 Since EPR can be used to study the coordination environment of paramagnetic atoms, it can be used as a measure of the porosity of alkali metal deposits in batteries that contribute to battery degradation 35 , 36 , 37 or how Li interacts with electrode materials. 39 , 40 Transition metal oxidation states common in electrode materials are also good targets for EPR, and paramagnetic species have been reported for Ru-, 41 V-, 42 , 43 Co-, 44 , 45 Mo-, 46 Mn/Ni-, 47 , 48 , 49 , 50 , 51 and Cu-containing 52 , 53 electrodes. EPR can also be used to examine the dissolution of transition metal components of battery electrodes during operating conditions.…”