Study of Li Metal Deposition in Lithium Ion Battery during Low-Temperature Cycle Using In Situ Solid-State⁷Li Nuclear Magnetic Resonance

Abstract

The influences of temperature and cell operation conditions on Li metal deposition in lithium ion batteries were studied by in-situ solid-state 7 Li nuclear magnetic resonance (NMR) spectroscopy. The rates of Li metal deposition during the low-temperature cycle with two charge-discharge operation modes, i.e., continuous current and pulse current, were estimated for temperatures of 5, 0, and −5 • C. Close values of activation energies were obtained for the capacity fading rate and the Li metal deposition rate, suggesting that Li metal deposition is the main cause of capacity fading in low-temperature cycles. The amounts of Li stored in the negative electrode and Li metal deposited during the low-temperature cycle were estimated and are discussed to understand the capacity fading mechanism. The pulse current mode cycle did not lead to any Li metal deposition at low temperatures. Lithium ion batteries (LIBs) are superior energy storage devices from the viewpoint of energy density, wide range of cell voltages derived from a variety of electrode materials, and further possibility of energy density improvement by developing innovative electrode materials.1,2 LIBs have been widely used in portable applications, and their use is extending to electric vehicles (EVs) and hybrid electric vehicles (HEVs). However, these EV applications require high energy densities to realize long driving distances, a long battery life to preserve the performance of vehicles during their lifecycle, and cost reduction. The temperature performance of LIBs also influences the vehicle performance, especially the limitation of low-temperature regeneration.3,4 This prevents full usage of LIB performance. LIBs are degraded by damage to the active material at high temperatures and by Li metal deposition at low temperatures.5-8 Moreover, the safety of LIBs is worsened by Li metal deposition.9,10 Thus, understanding the behavior of Li metal deposition at low temperatures is crucial for optimizing charging protocols and assuring safe and durable use of LIBs.Li metal deposition has been studied using optical microscopy and scanning electron microscopy with specially designed electrochemical cells at ambient temperature, which has allowed observation of the growth of dendritic Li deposition and estimation of the volume during operation.11-13 However, those cells were open structures that did not consider actual cell circumstances, such as the limited volume of electrolyte and the cell pressure, which restrains the movement of Li ions. Li metal deposition has also been evaluated by weighing the electrode and measuring the nuclear magnetic resonance (NMR) of a commercial 18650 battery after cycling.14-16 However, these studies are post molten analysis with disassembling the cell and affected the results by sample preparation.17 Furthermore, deposited Li metal sometimes intercalates into graphite, thus missing the chance to acquire a true sample. 16 We developed an in-situ solid-state 7 Li NMR method using a small laminated full cell composed of actual ele...

Fast charging of lithium-ion batteries at all temperatures

“…For baseline cells, the logarithm of aging rate vs. 1/T can be fitted with a linear line, confirming that the aging rate of conventional LiBs follows Arrhenius law (12). The activation energy is estimated to be −1.37 eV, which is within the range reported in the literature (29). We note that the aging rate of the LPF cell at 0°C was brought down by two orders of magnitude compared with the baseline conventional cell, and became close to that of the baseline cell at room temperature, indicating a paradigm shift of the relationship between aging rate and ambient temperature.…”

Operando NMR of NMC811/Graphite Lithium-Ion Batteries: Structure, Dynamics, and Lithium Metal Deposition

“…[18][19][20] Fewer applications have been made to Li metal deposition on graphite at low temperature: Wandt et al have reported operando measurements using electron paramagnetic resonance 21 and Arai et al employed in situ NMR at room temperature to detect deposited Li metal after low-temperature cycling. 22 To the best of our knowledge no operando NMR of Li metal deposition on graphite in full-cells at low temperatures has been reported so far.…”

“…Additionally, Li metal can lose electrical contact to the anode during discharge and remain inactive in the cell as so-called “dead lithium”. Magnetic resonance techniques are valuable tools for investigating Li metal deposition, and in situ and operando NMR measurements have been instrumental in studying this process in Li metal batteries. − Fewer applications have been made to Li metal deposition on graphite at low temperature: Wandt et al have reported operando measurements using electron paramagnetic resonance and Arai et al employed in situ NMR at room temperature to detect deposited Li metal after low-temperature cycling . To the best of our knowledge no operando NMR of Li metal deposition on graphite in full-cells at low temperatures has been reported so far.…”

Application of Magnetic Resonance Techniques to the In Situ Characterization of Li-Ion Batteries: A Review

“…Therefore, this effect was attributed to absorption of deposited Li into the carbon of negative electrodes. Furthermore, the influence of temperature and battery operating conditions on Li metal deposition was investigated using the same cell setup [75]. Similar activation energies were obtained for the Li metal deposition rate and cell capacity fading rate, suggesting that Li metal deposition is the main cause of capacity fading during low-temperature cycling.…”