Metal/LiF/Li₂O Nanocomposite for Battery Cathode Prelithiation: Trade-off between Capacity and Stability

Abstract

Lithium-ion batteries (LIBs) are currently dominating the portable electronics market and supplying power for electric vehicles and grid-level storage. However, lithium loss in the formation cycle at the anode side reduces the energy density of state-of-the-art LIBs with carbon anode materials. This situation will be even more severe for future LIBs using high-capacity Si-based anode materials. In this study, a transition metal-based nanocomposite with built-in lithium source was synthesized, featuring Fe nanodomains with a size of ∼5 nm uniformly dispersed in a hybrid Li2O and LiF matrix with intimate contact between them. The Fe/LiF/Li2O nanocomposite released a high Li-ion capacity of 550 mA h/g based on a multielectron inverse conversion reaction during the first-cycle charge process and exhibited better ambient stability than the counterpart with a pure Li2O matrix and also a lower lithium-extraction voltage and faster reaction kinetics than the counterpart with a pure LiF matrix. Serving as an additive to various cathodes (e.g., LiCoO2, LiFePO4, and LiNi1‑x‑y Co x Mn y O2), the Fe/LiF/Li2O nanocomposite showed excellent lithium compensation effect. Using 4.8 wt % Fe/LiF/Li2O additive based on the total mass of the electrodes, a LiNi0.8Co0.1Mn0.1O2|SiO-graphite full cell with a high cathode mass loading of 20 mg/cm2 exhibited a high reversible capacity of 2.9 mA h/cm2 at 0.5 C after 100 cycles which is a 15% increase in comparison to the counterpart without the prelithiation additive. After the Fe/LiF/Li2O nanocomposite was immersed into the electrolyte and rested for 72 h, the content of iron metal in the electrolyte was negligible, indicating that this prelithiation additive was stable in the electrolyte and would not cause any side reactions, such as the shuttle of iron ions during cycling. The high “donor” Li-ion capacity, good ambient stability, and its compatibility with existing cathode materials and battery fabrication processes make the Fe/LiF/Li2O nanocomposite a promising cathode prelithiation additive to offset the initial lithium loss and improve the energy density of LIBs.

Prelithiation/Presodiation Techniques for Advanced Electrochemical Energy Storage Systems: Concepts, Applications, and Perspectives

“…Additionally, the multicomponent Fe/LiF/Li 2 O nanocomposite has been designed and utilized for cathode prelithiation, which could release a high Li‐ion capacity of 550 mAh g −1 based on a multielectron inverse conversion reaction during the first‐cycle charge process. [ 131 ] Serving as an additive to various cathodes (e.g., LiCoO 2 , LiFePO 4 , and LiNi 1− x − y Co x Mn y O 2 ), the Fe/LiF/Li 2 O nanocomposite displays outstanding lithium compensation effect. A conformal Li 2 O/Co nanoshell (≈20 nm) on LiCoO 2 particles was prepared by in situ chemical formation, which could be selected as a high‐capacity built‐in prelithiation reagent to compensate this initial lithium loss.…”

Synthesis, Modification, and Lithium‐Storage Properties of Spinel LiNi0.5Mn1.5O4

“…By introducing an external lithium source to make up for the irreversible lithium loss during the first charge and discharge, batteries can exhibit a higher reversible capacity. Du J et al [135] . synthesized Fe/LiF/Li 2 O nanocomposite as a cathode pre‐lithium material, which had a good lithium ion compensation effect.…”

Promises and Challenges of the Practical Implementation of Prelithiation in Lithium‐Ion Batteries

“…Metal/LiF/Li 2 O nanocomposites were successfully introduced into LiNi 0.8 Co 0.1 Mn 0.1 O 2 cathode using slurry approach in ambient condition with low humidity (<20%). [ 39 ]…”

“…[ 37,65 ] Very recently, a M/Li 2 O/LiF nanocomposite with metal in a hybrid Li 2 O and LiF matrix delivered a high donable lithium ion capacity of 550 mAh g −1 . [ 39 ] While the employment of cathode prelithiation additives has to be introduced during slurry mixing and fabrication, introducing extra active Li into each particle of active materials provides an alternative approach. Overlithiation of cathode materials represents a new research direction, which not only brings in extra active lithium for lithium compensation, but also avoids the potential harsh battery fabrication condition that regular battery prelithiation requires.…”

“…All gravimetric capacities were extracted from the related literatures. [ 8,24,27,37–39,56,58–60,63–66,69,71,98 ]…”