New Insight on Graphite Anode Degradation Induced by Li‐Plating

Abstract

Since the first lithium-ion batteries (LIBs) commercialized by Sony Corporation in 1991, they are being considered as the most suitable technology for electric vehicles and stationary energy storage systems. [1][2][3][4] Most of commercial LIBs are based on graphite anode due to their high energy density (high capacity of 372 mAh g −1 and low de-/lithiation potential around 0.1 V vs Li/Li + ), [5] long cycle life, low cost and environmental friendliness. [4,[6][7][8][9][10][11] With the motive to accelerate worldwide market adoption of electrical vehicles and provide better user experience, it is an inevitable trend to develop fast charging technology. However, the graphite is still a barrier that hampers high-rate performance of commercial LIBs. [6,9] During charge process, Li ions migrate to the anode and are desired to be inserted into the layered structure of graphite, but Li ions can also be directly reduced to metallic Li under high overpotential, which generally occurs at high charging rates or low temperatures, resulting in rapid decay of electrochemical performances and thermal safety concerns. [12][13][14] In order to address these problems, extensive efforts have been engaged, [14][15][16][17][18][19] but the mechanism of capacity decay of graphite after Li-plating is still unclear. In this work, we aim to describe the mechanism of lithium evolution from intercalated ions in graphite to Li metal plating on graphite particle surfaces by over-lithiation cycle test, in-situ XRD, and titration gas chromatography (TGC). We deteriorate the conditions of lithium plating on graphite and find the Li insertion/deintercalation machnism vanish fast in graphite particles. Our results demonstrate that the graphite intercalation compounds (GICs: LiC 12 , LiC 6 e.g.) gradually become inactive and wrapped by dead lithium or side reaction sediments, and the intercalated Li-ions cannot be stripped from GICs. The isolation of GICs particles leads to fast graphite loss. This insertion/deintercalation vanishing process will be accelerated at low temperature and high rates. The new insight on graphite anode degradation induced by Li-plating can be used to guide the design of advanced materials and electrodes to achieve extreme fast charging. Results and Discussion The Electrochemical Performance of Graphite|Li During Over-Lithiation ProcessThe morphologies of graphite particles are characterized by SEM and TEM, as shown in the inset of Figure 1a and Figure S1. The particles

Decline Mechanism of Graphite/Lithium Metal Hybrid Anode and Its Stabilization by Inorganic-Rich Solid Electrolyte Interface

“…From a materials perspective, strategic use of the empty spaces inside and between the particles of graphite is considered to be able to accommodate lithium metal and obtain a hybrid anode with high CE. ,, Given that graphite occupies a considerable volume and mass in the hybrid anode, its capacity contribution cannot be ignored. Although previous studies suggested that the structure and capacity retention ability of graphite may be compromised in hybrid anodes with long-term cycling, further direct evidence and comprehensive analysis are needed. ,, …”

“…Although previous studies suggested that the structure and capacity retention ability of graphite may be compromised in hybrid anodes with long-term cycling, further direct evidence and comprehensive analysis are needed. 20,25,26 In this contribution, we conducted in situ characterization of graphite during lithium metal plating and stripping. In the presence of lithium metal coating, the phase-transition process of graphite is hysteretic and mixed, and lithium ions cannot complete the reversible intercalation process under the "dead lithium" and SEI layers.…”

Pattern Investigation and Quantitative Analysis of Lithium Plating under Subzero Operation of Lithium-Ion Batteries

“…Lithium-ion batteries (LIBs) are widely used in electronics, public transportation, and energy storage based on their high energy and power density, long cycle life, and environmental friendliness. − However, Li plating can easily lead to potential safety hazards, which is a problem that cannot be ignored. , Li plating occurs when lithium ions (Li + ) are reduced to metallic Li on the surface of the graphite anode during the charging process of the battery, which prevents normal intercalation. , Usually, poor battery balance, such as mismatched anode–cathode ratio (N/P) or manufacturing defects, and abuse of operating conditions, such as high C rate charging or low-temperature charging, will lead to Li plating. − Li plating can lead to a reduction in the battery capacity and the formation of strong Li dendrites, which can puncture the separator and cause a short circuit, resulting in thermal runaway or even explosion. , Therefore, prevention of Li plating is essential for the safety and performance of LIBs.…”

Silicon Graphite Composite Anode Degradation: Effects of Silicon Ratio, Current Density, and Temperature

“…[7][8][9] In addition, as lithium is excessively deposited on the graphite surface, problems such as faster consumption of active lithium, cell short circuits, and fire due to dendrites may occur. [10][11][12][13][14][15][16] To achieve high energy density and stability, the composite electrode based on Si and graphite has been developed and utilized. Compared with pure Si, the mixture of graphite and Si shows higher electrical conductivity because the graphite surrounding Si compensates for the poor conductivity of Si.…”

“…[ 7–9 ] In addition, as lithium is excessively deposited on the graphite surface, problems such as faster consumption of active lithium, cell short circuits, and fire due to dendrites may occur. [ 10–16 ]…”