Enhanced Electrolyte Transport and Kinetics Mitigate Graphite Exfoliation and Li Plating in Fast‐Charging Li‐Ion Batteries

Abstract

Despite significant progress in energy retention, lithium‐ion batteries (LIBs) face untenable reductions in cycle life under extreme fast‐charging (XFC) conditions, which primarily originate from a variety of kinetic limitations between the graphite anode and the electrolyte. Through quantitative Li+ loss accounting and comprehensive materials analyses, it is directly observed that the operation of LIB pouch cells at 4 C||C/3 (charging||discharging) results in Li plating, disadvantageous solid‐electrolyte‐interphase formation, and solvent co‐intercalation leading to interstitial decomposition within graphite layers. It is found that these failure modes originate from the insufficient properties of conventional electrolytes, where employing a designed ester‐based electrolyte improved the capacity retention of these cells from 55.9% to 88.2% after 500 cycles when operated at the aforementioned conditions. These metrics are the result of effective mitigation of the aforementioned failure modes due to superior Li+ transport and desolvation characteristics demonstrated through both experimental and computational characterization. This work reveals the vital nature of electrolyte design to XFC performance.

Accurate Calculation of Solid-State Li+ Diffusion Coefficient and Kinetic Activation Energies for an Artificial Graphite Anode

“…7 Under extremely fast charging conditions, LIBs face inevitable reductions in cycle life and generate internal short circuits or thermal runaway safety issues due to lithium precipitation plating on the surface of the anode, which primarily originates from kinetic limitations of the electrode electrochemical process. 8,9 The rate-determining steps of the electrode kinetics process are highly dependent on the particle size, interface characteristics, and electrode configuration. Weng et al 10 proposed that when the graphite particle size is less than 10 μm, the interfacial Li + diffusion and electrode transportation are the main rate-determining steps.…”

Co-Intercalation-Free Graphite Anode Enabled by an Additive Regulated Interphase in an Ether-Based Electrolyte for Low-Temperature Lithium-Ion Batteries

“…Lithium-ion batteries (LIBs) based on Li-ion intercalation and deintercalation between graphite anode and metal oxide cathode obtained tremendous success in various portable electronic devices and electric vehicles . Nonetheless, the further promotion of LIBs in large-scale energy storage devices is trapped by the sluggish electrochemical kinetics of graphite anode, especially at low-temperature and fast-charging conditions, which will lead to a sharp decline in capacity and serious polarization of Li-ion intercalation/deintercalation process. − To make matters worse, the Li metal deposition and dendrite growth caused by the high polarization also cause safety concerns for the batteries. − In general, the electrochemical reaction kinetics of graphite anode in LIBs are mainly related to three processes: (1) the migration of lithium ions in a bulk electrolyte, (2) the charge transfer process on the surface of Gr anode, including the desolvation and the following transport of Li ions through the solid electrolyte interphase (SEI), and (3) the diffusion of Li ions in the Gr anode. ,, It can be seen that electrolyte plays crucial roles in regulating the kinetics of the Gr anode, as it not only directly affects the transport of Li ions but also determines the desolvation process, as well as the composition of SEI. − Traditional carbonate electrolytes usually involve ethylene carbonate as an indispensable main solvent as it can not only form a stable SEI to avoid solvent co-intercalation into the graphite layer but also provide sufficient ion dissociation capacity. , However, the high melting point and strong binding force of EC also hinder the transportation of Li ions at a low temperature. , Therefore, developing advanced electrolytes with high ionic conductivity, low viscosity and melting point, weak solvation ability, and good film-forming properties is urgent for LIBs. , …”

Accelerating High-Rate Li-Ion Storage in Graphite via a Thin-Layer Coating of Atomic Mo–NC

“…Li dendrites formed outside of Gr can penetrate the solid electrolyte interface (SEI), increase the irreversible capacity, and even pierce through the separator, which ultimately induces dangerous short circuits and thermal runaway. 9 Many strategies have been developed to address the above problems, including structural engineering and porosity management for a shortened Li + transport pathway, 10,11 electrolyte regulation for optimal Li + −solvent interaction, 12−14 interface engineering for stable SEI formation, 15 lowered desolvation barriers, 16,17 and fast charge transfer. 18,19 Among them, the interface constructed by graphite/SEI/solvent is of utter importance because it involves several key steps during Li insertion and extraction processes, including Li + desolvation, 20, 21 Li + migration through SEI, 22 charge transfer at Gr edges, 23 Li + diffusion into Gr, 24 etc.…”

“…To meet their ever-growing demands, it is urgent to advance LIBs with higher energy and power and, more importantly, greater safety. , Various types of graphite (Gr) materials are currently being used as anodes for manufacturing commercial LIBs due to their merits of high Li-ion-storage energy density, good insertion/extraction reversibility, nontoxicity, high safety, and low costs. − However, the LIB field is currently facing a major drawback with the Gr anode, as unwanted Li dendrite formation can occur outside of the Gr anode instead of Li + insertion into the graphite interlayer if the battery is charged at high rates. , This is primarily due to the slow Li + intercalation kinetics of Gr. Li dendrites formed outside of Gr can penetrate the solid electrolyte interface (SEI), increase the irreversible capacity, and even pierce through the separator, which ultimately induces dangerous short circuits and thermal runaway …”