Ultralong Lifespan for High-Voltage LiCoO₂ Enabled by In Situ Reconstruction of an Atomic Layer Deposition Coating Layer

Abstract

Although the rapid development of electrical energy storage devices has slowed down environmental pollution, their largescale application has posed huge challenges to battery-related mineral resources; thus, extending the lifespan of high-voltage lithium cobalt oxide (LCO) is of great importance. Surface oxide coating is considered as the most common low-cost modification method for addressing unstable cycling performance. However, studies have shown that the oxide layer would further react with an electrolyte, while the investigation on the corresponding component evolution is lacking. Herein, a typical example utilizing the above reaction to realize surface reconstruction is presented. Applying atomic layer deposition (ALD), originally, an ultrathin Al 2 O 3 layer is coated on the LCO surface; however, this coating layer has undergone reconstruction after reacting with electrolyte decomposition products during the cycling. Compared with simple coating, the in situ formed Li 3 AlF 6 layer has a tighter binding to the LCO surface while possessing good Li + conductivity and electrochemical stability. In addition, the unique properties of the ALD technology allow us to achieve ultrathin (1 nm) and conformal coating, which is beneficial for electronic conductivity and cycling stability. Furthermore, the surface phase transition layer stripping failure mechanism has first been revealed to explain the loss of Co and O, while the reconstructed Li 3 AlF 6 effectively suppresses the surface stripping. Thus, excellent high-voltage performance has been realized (an 89% capacity retention after 1000 cycles at 4.5 V and an 88% capacity retention after 200 cycles at 4.6 V). This work casts a new understanding on the surface reconstruction of the oxide coating layer, which is also significant for other electrode materials' modification.

Realizing Holistic Charging–Discharging for Dendrite-Free Lithium Metal Anodes via Constructing Three-Dimensional Li+ Conductive Networks

“…As a fundamental substrate, commercial bare NF was picked out with a statistically average pore diameter of 182 μm (Figure S1). Ascribed to the unique advantages of ALD, , a 15 μm thick ionic conductor LPO layer had been coated on every monomer of NF uniformly (Figure S2). The SEM images of the top and cross-sectional morphology in LPNF are shown in Figure b,c, respectively.…”

Insights into Influencing Electrode Calendering on the Battery Performance

“…Lithium cobalt oxide (LiCoO 2 , LCO) was a popular CAM due to its high tap density, high ionic conductivity, high discharge plateau voltage, and high theoretical capacity. [197,198] To enable the high voltages of LCO, however, the material will be subjected to voltages beyond 4.2 V, where it can undergo side reactions and loss of Co and O, leading to particle breakage and ultimately limiting the long-term cycling stability. [198] In a study by Fa and Fedwik, [199] LCO cathodes were subjected to calendering, and showed that the specific capacity could be improved by compaction with 27 MPa and further improved with compaction at 54 MPa.…”

“…[197,198] To enable the high voltages of LCO, however, the material will be subjected to voltages beyond 4.2 V, where it can undergo side reactions and loss of Co and O, leading to particle breakage and ultimately limiting the long-term cycling stability. [198] In a study by Fa and Fedwik, [199] LCO cathodes were subjected to calendering, and showed that the specific capacity could be improved by compaction with 27 MPa and further improved with compaction at 54 MPa. An improvement in the C-rate capability was also observed.…”

“…Lithium cobalt oxide (LiCoO 2 , LCO) was a popular CAM due to its high tap density, high ionic conductivity, high discharge plateau voltage, and high theoretical capacity. [ 197,198 ] To enable the high voltages of LCO, however, the material will be subjected to voltages beyond 4.2 V, where it can undergo side reactions and loss of Co and O, leading to particle breakage and ultimately limiting the long‐term cycling stability. [ 198 ]…”

Constructing a Stabilized Cathode Electrolyte Interphase for High-Voltage LiCoO2 Batteries via the Phenylmaleic Anhydride Additive

“…Huang et al revealed that Mg-pillared LiCoO 2 , substituting the Octa-3a site in the Li slab by Mg 2+ , benefited to eliminate CEI overgrowth and enhance cycling stability within the voltage window of 3.0–4.6 V . Besides, the design of the functional electrolyte with appropriate additives is convenient and cost-effective, which holds great potential for commercial applications without a large-scale change of production conditions. ,− Electrolyte additives with specially designed functional groups could approach the inner Helmholtz layer and in situ participate in forming a uniform and stabilized CEI film on the surface of LCO, which blocks the reactions at the electrode/electrolyte interface. ,− For instance, Ruan et al adopted 5-acetylthiophene-2-carbonitrile (ATCN) to in situ construct a stable CEI film with low impedance, increasing the capacity retention of Li||LCO batteries from 53 to 91% after 200 cycles at a charge cutoff of 4.5 V . Anhydride-type additives have also been widely concerned and applied in LIBs, such as Li||LiNi 0.9 Co 0.05 Mn 0.05 O 2 and Li||LiNi 0.5 Mn 1.5 O 4 batteries (as summarized in Table S1), which however have rarely been well-investigated for LCO batteries at a high charge cutoff voltage of, e.g., 4.65 V until now.…”