Local Electric‐Field‐Driven Fast Li Diffusion Kinetics at the Piezoelectric LiTaO₃ Modified Li‐Rich Cathode–Electrolyte Interphase

Abstract

HEVs (PHEVs), besides the traditional applications in portable devices. To build the next generation LIBs with higher performances, high energy density materials are urgently pursued worldwide. [1][2][3] Lithium-rich (Li-rich) materials, with the specific capacity over 260 mAh g −1 and energy density up to ≈1000 Wh kg −1 , [4] have attracted great interest in the past decades. It is reported that Li-rich materials are composed of two phases of Li 2 MnO 3 (C 2/m ) and LiMO 2 (R m 3 ) (M = Ni, Co, Mn, etc.). [5][6][7][8][9] Despite the above advantages, several concerns including structural instability and the resulted voltage degradation, as well as the poor diffusion kinetics at the interface have become the bottlenecks of Li-rich materials. [9][10][11][12][13] In this regard, multifarious modification approaches, such as doping and surface coating, have been intensively investigated. [14][15][16] Particularly, Li + diffusion at the cathode-electrolyte interphase (CEI) is widely regarded as the rate determining step in LIBs. [17][18][19] From this viewpoint, metal fluorides (FeF 3 , [20] MOF, [21,22] AlF 3 , [23,24] etc.), metal oxides (MgO, [25] Al 2 O 3 , [26,27] etc.), metal phosphates (AlPO 4 , [28] LaPO 4 , [29] Li 3 PO 4 , [30] FePO 4 /Li 3 PO 4 , [31] Li-Mn-PO 4 , [32] etc.), and those with similar structure of Li-rich Li 2 MnO 3 (Li 2 SiO 3 [33,34] and Li 2 SnO 3 , [35] ) have been widely applied to modify the surface of bulk Li-rich materials. Recently, fast lithium-ion conductors (LiVO 3 , [36] Li 2 ZrO 3 , [37] Li-La-Ti-O, [38,39] LiPON, [40] etc.) have also been proposed to decorate the surface of Li-rich cathodes to enhance the apparent diffusion coefficients. All the aforesaid surface modification materials, unexceptionally, have been proved to be effective in both stabilizing the structure and facilitating the Li + kinetics. Nevertheless, in general, the decoration layers themselves seem rather "passive" in promoting Li + diffusion. Assuming they are Li + conductive (e.g., solid electrolyte materials), fast Li + diffusion channels will be provided besides the general separation effect (in suppressing side reactions and inevitable TM dissolution). As for Li + insulators (e.g., metal fluorides), only the benefit of physical barriers could be exploited. Therefore, a more "initiative" function interface is imperative to be built to more effectively promote the Li + transport at the electrode-electrolyte interphase.It is noteworthy that piezoelectric material, as an important category in the energy-conversion community, works on the As one of the most promising cathodes for next-generation lithium ion batteries (LIBs), Li-rich materials have been extensively investigated for their high energy densities. However, the practical application of Li-rich cathodes is extremely retarded by the sluggish electrode-electrolyte interface kinetics and structure instability. In this context, piezoelectric LiTaO 3 is employed to functionalize the surface of Li 1.2 Ni 0.17 Mn 0.56 Co 0.07 O 2 (LNMCO), aiming to boost t...

Rational Design of a Piezoelectric BaTiO3 Nanodot Surface‐Modified LiNi0.6Co0.2Mn0.2O2 Cathode Material for High‐Rate Lithium‐Ion Batteries

“…For the BTO modified samples, the increased rate capability is attributed to the generated built-in electric field pointing to the inner direction of the cathode material will act in promoting the diffusion of lithium-ions among the nickel-rich cathode, BTO nanodots, and the electrolyte phase interface, especially during the discharging process. [26,27] Figure S4 shows the comparison of the cycle performance among pristine NCM622 and various BTO contents modified NCM622 at C. The 0.5 wt.% BTO sample delivers 171 mAh g À 1 discharge capacity and the capacity retention is as high as 89 % after 100 cycles, and 0.25 %-NCM622@BTO has a discharge capacity of 163 mAh g À 1 (capacity retention rate of 88 %), which is better than 162 mAh g À 1 and 86 % capacity retention of pristine NCM622. For 1 %-NCM622@BTO, an excessively thick coating layer is formed on the surface of NCM622, which hinders the diffusion of lithium-ions and results in a substantial decrease with a discharge specific capacity of 147 mAh g À 1 .…”

“…[26] Si et al have constructed a piezoelectric LiTaO 3 coating layer between Li-rich cathode and the electrolyte interface, which can not only be used as an "initiative" accelerator to promote Li + diffusion kinetics, but also reinforces the Li-rich cathode structure. [27] Hence, BaTiO 3 (BTO) material combing the physical characteristics of piezoelectricity and ferroelectricity is regarded as an alternative material for the modification of LIBs.…”

Surface Modification of Li‐Rich Mn‐Based Layered Oxide Cathodes: Challenges, Materials, Methods, and Characterization

“…[57d] Spectroscopic studies clearly identified decomposition of alkyl carbonates and LiPF 6 on LMLO electrodes and formation of polymeric decomposition products. [77,78] In general, all of the above-described undesirable surface reactions can be significantly inhibited by coating as a pretreatment or by in situ surface modification using electrolyte solutions which contain functional additives. [77] For example, Si et al prepared LiTaO 3 -coated LMLO with stabilized electrode-electrolyte solution interface by surface films that enable fast interfacial Li ion transport.…”

“…[77] For example, Si et al prepared LiTaO 3 -coated LMLO with stabilized electrode-electrolyte solution interface by surface films that enable fast interfacial Li ion transport. [78] Xiao et al [82] and Nayak et al [79] used lithium bis(oxalato)borate (LiBOB) as an effective additive in solutions that form protecting surface films. Schematic mechanisms for the protective effect of surface films are shown in Figure 3b.…”

Electroanalytical Sensor for Diabetic Foot Ulcer Monitoring with Integrated Electronics for Connected Health Application

“…This can be attributed to the high surface area of nanofibers which promotes enhanced interfacial electron transfer facilitated by strong local electric field gradient [49,50]. However, R ct gradually increased upon tyrosinase immobilization on the nanofibers (C/α-MnO 2 /tyrosinase); which can be attributed to the insulating nature of the enzyme thereby passivating the electrode surface [24].…”