Tunable and Robust Phosphite-Derived Surface Film to Protect Lithium-Rich Cathodes in Lithium-Ion Batteries

Abstract

A thin, uniform, and highly stable protective layer tailored using tris(trimethylsilyl) phosphite (TMSP) with a high tendency to donate electrons is formed on the Li-rich layered cathode, Li1.17Ni0.17Mn0.5Co0.17O2. This approach inhibits severe electrolyte decomposition at high operating voltages during cycling and dramatically improves the interfacial stability of the cathode. The TMSP additive in the LiPF6-based electrolyte is found to preferentially eliminate HF, which promotes the dissolution of metal ions from the cathode. Our investigation revealed that the TMSP-derived surface layer can overcome the significant capacity fading of the Li-rich cathode by structural instability ascribed to an irreversible phase transformation from layered to spinel-like structures. Moreover, the superior rate capability of the Li-rich cathode is achieved because the TMSP-originated surface layer allows facile charge transport at high C rates for the lithiation process.

Prescribing Functional Additives for Treating the Poor Performances of High‐Voltage (5 V‐class) LiNi0.5Mn1.5O4/MCMB Li‐Ion Batteries

“…The addition of TMSP and PCS binary functional additives does work to change the surface morphology of long-term cycled LiNi 0.5 Mn 1.5 O 4 and MCMB electrodes (typical scanning electron microscopy (SEM) images in Figures S4-S7, Supporting Information). [35,[48][49][50][51][52][53] It is well known cycle, with a) BE and b) BE + binary functional additives (1 wt% TMSP + 1 wt% PCS) at 1 C rate, respectively. [35,[48][49][50][51][52][53] It is well known cycle, with a) BE and b) BE + binary functional additives (1 wt% TMSP + 1 wt% PCS) at 1 C rate, respectively.…”

“…[8,[31][32][33][34][35][36][37][38][39][40][43][44][45][46][47] To develop new functional additives for electrolyte, molecular orbital (MO) calculation is used as a first screening method. [35,[48][49][50][51][52][53] With a higher HOMO energy relative to carbonate solvents, TMSP easily undergoes electrochemi cal oxidations and promotes the formation of a protective SEI layer on the surface of high-voltage cathode materials (such as LiNi 0.5 Mn 1.5 O 4 , LiNi 0.5 Co 0.2 Mn 0.3 O 2 , overlithiated layered oxide). Specifically speaking, functional additives with a higher HOMO energy than carbonate solvents will be preferentially oxidized to modify the cathode SEI layer, while those with a lower LUMO energy than carbonate solvents will be preferentially reduced to modify the anode SEI layer.…”

A Novel Strategy to Suppress Capacity and Voltage Fading of Li‐ and Mn‐Rich Layered Oxide Cathode Material for Lithium‐Ion Batteries

“…It is generally accepted that the structure instability of the LMRO cathode material is one of the intrinsic reasons of its fast capacity and voltage fading. [25] Presently, several strategies have been proposed to suppress the capacity and voltage fading of LMRO cathode material. [22] On the other hand, the capacity fading is also caused by the dissolution of metal elements into the electrolyte.…”

“…[15][16][17] The phase transformation from layered to spinel structure gives rise to the crystal instability when the LMRO cathode is charged to 4.8 V. [18][19][20][21] The gradual growth of spinel phase during cycling brings about the appearance of a 3.0 V plateau resulting in the voltage fading and then consequently leading to the capacity fading. [25] Presently, several strategies have been proposed to suppress the capacity and voltage fading of LMRO cathode material. [23,24] Zheng et al [8] believe that the loss of MnO and NiO results in the capacity loss of the Li[Li 0.2 Ni 0.2 Mn 0.6 ]O 2 electrode because of the formation of spinel phase and subsequent fragmentation and deactivation of transition metal ions.…”

Utilizing Co2+/Co3+ Redox Couple in P2‐Layered Na0.66Co0.22Mn0.44Ti0.34O2 Cathode for Sodium‐Ion Batteries

“…P2‐Na 0.67 MnO 2 can deliver a high capacity of 175 mAh g −1 , but suffers from poor cycle stability during sodiation/desodiation due to the presence of Jahn–Teller active Mn 3+ ,29 which is a serious problem for practical implementation of such materials 30, 31. In addition, the existence of Mn 3+ may produce Mn 2+ ions due to disproportionation reaction, which favor to dissolve into the carbonate‐based electrolytes 32, 33. To address these issues, using other transition metals, such as cobalt, nickel to substitute the Mn ions in layered Na x MnO 2 , has been investigated 29, 30, 31.…”