Polyvinylpyrrolidone-Induced Uniform Surface-Conductive Polymer

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Polyvinylpyrrolidone-Induced Uniform Surface Conductive Polymers Coating Endows Ni-Rich LiNi0.8Co0.1Mn0.1O2 with Enhanced Cyclability for Lithium-Ion Batteries Qingmeng Gan, Ning Qin, Youhuan Zhu, Zixuan Huang, Fangchang Zhang, Shuai Gu, Jiwei Xie, Kaili Zhang, Li Lu, and Zhouguang Lu ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.9b04050 • Publication Date (Web): 12 Mar 2019 Downloaded from http://pubs.acs.org on March 13, 2019

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ACS Applied Materials & Interfaces

Polyvinylpyrrolidone-Induced Uniform Surface Conductive Polymers Coating Endows Ni-Rich LiNi0.8Co0.1Mn0.1O2 with Enhanced Cyclability for Lithium-Ion Batteries Qingmeng Gan†,‡, Ning Qin†,§, Youhuan Zhu†, Zixuan Huang†, Fangchang Zhang†, Shuai Gu†, Jiwei Xie†, Kaili Zhang§, Li Lu ‡, Zhouguang Lu*† †

Department of Materials Science and Engineering, Southern University of Science and

Technology, Shenzhen 518055, China. ‡

§

Department of Mechanical Engineering, National University of Singapore, 117575, Singapore.

Department of Mechanical Engineering, City University of Hong Kong, 83 Tat Chee Avenue,

Hong Kong 999077, China.

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ABSTRACT: Ni-rich LiNi0.8Co0.1Mn0.1O2 (NCM811) cathode has attracted great interest owing to its low cost, and high capacity and energy density. Nevertheless, rapid capacity fading is the critical problem due to direct contact of NCM811 with electrolyte and hence restrain its wide applications. To prevent the direct contact, surface inert layer coating becomes a feasible strategy to tackle this problem. However, to achieve homogeneous surface coating is very challenge. Considering the bonding effect between NCM811, polyvinylpyrrolidone (PVP) and polyaniline (PANI), in this work, we use PVP as inductive agent to controllably coat uniform conductive PANI layer on NCM811 (NCM811@PANI-PVP). The coated PANI layer not only serves as a rapid channel for electron conduction, but also prohibits direct contact of electrode with the electrolyte to effectively hinder side reaction. NCM811@PANI-PVP thus exhibits excellent cyclability (88.7% after 100 cycles at 200 mA g-1) and great rate performance (152 mA h g-1 at 1000 mA g-1). In-situ X-ray diffraction and in-situ Raman are performed to investigate charge-discharge mechanism and the cyclability of NCM811@PANI-PVP upon electrochemical reaction. This surfactant modulated surface uniform coating strategy offers a new modification approach to stabilize Ni-rich cathodes materials for lithium ion batteries.

KEYWORDS: Ni-rich cathode; Surfactant inductive agent; Uniform surface coating; Conductive polymer; Excellent cyclability


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INTRODUCTION Lithium-ion batteries (LIBs) have been applied in consumable and portable electronics. However, implementation of LIBs in clean electric vehicles (energy density: 300 W h kg-1) as well as largescale energy storage has long been hindered by their low energy density and safety issue.1-3 The energy density of LIBs is partly determined by the cathode materials. Up to now, numerous cathode materials have been successfully developed, such as LiCoO2,4-5 LiFePO4,6-7 LiMn2O4,8-9 and layered Li[NixCoyMn1-x-y]O2 (NCM)10-12 compounds. Among these materials, NCM, especially LiNi0.8Co0.1Mn0.1O2 (NCM811), has been regarded as one of the most promising cathode materials because of its high specific capacity (~210 mA h g-1) as well as low cost. Nevertheless, the nature of terrible cycling stability impedes the wide application of NCM811 materials.13-15 The remaining critical problems impede the wide commercialization of NCM811 including, (i) high content residual alkali compounds (e.g., LiOH and Li2O) on the surface that will react with H2O/CO2 from the air and form LiOH/Li2CO3 layer, of which LiOH layer would react with LiPF6 from electrolyte while Li2CO3 would cause battery flatulence, (ii) irreversible structural rearrangement (especially at the surface) leading to formation a Li-deficient and highly resistive rocks-salt phase (NiO), (iii) substantial volume variation resulting in micro-strain and cracks during Li ions de/intercalation process, giving rise to unsatisfactory cyclability, and (iv) parasitic reactions between Ni4+ and electrolyte, and the oxygen removal, especially in the highly delithiated state, reducing the cyclability of NCM811.16-18 As a result of combination of above, the capacity decay of NCM811 is fast and the risk of thermal runaway is high. 3 ACS Paragon Plus Environment


Considerable efforts have been devoted to the modification the surface of NCM811 to segregate the bulk materials with electrolyte, decreasing the electrode surface reactivity with solution species.19-21 Moreover, the coating layer can release the surface phase transformations from a layered to a disordered spinel or a rock-salt structure. Metal oxides (eg., TiO2,22 ZrO2,23 and Al2O324), metal ﬂuorides (e.g., LiF25 and AlF326), and metal phosphates (e.g., Li-Mg-PO4,27 LiFePO428 and Li3PO41, 29) are generally considered as effective choice for modifying the surface of NCM811 cathode. Compared to inorganic coating materials, conducting polymers (e.g., polyaniline (PANI)) have the advantages of high electronic conductivity, brilliant environmental stability, and low cost, which could simultaneously stabilize the cycling and improve the rate capability of NCM811.30-32 However, it is still a big challenge to coat a homogeneous conducting polymer layer on the surface of NCM811 because it is lack of bonding effects between NCM811 and polymers. Polyvinylpyrrolidone (PVP), as a surfactant, has been widely used to modify the surface of metal oxides because PVP can donate a pair of electrons from the carbonyl oxygen to the metal cations, or form complicated bonds between nitrogen in the five-membered nitrogen-containing heterocycles and the metal cations.33-35 It has been reported that PVP has excellent chemical compatibility with PANI polymer because of the strong hydrogen-bond interaction between PANI polymer and PVP molecules.36-37 Therefore, it is desirable to realize uniform PANI coating on the surface of NCM811 with the pre-modification of PVP. In this work, we have achieved uniform coating of conducting PANI on the surface of NCM811 through pre-treatmenting NCM811 particles with PVP. Owing to the bonding effect between 4 ACS Paragon Plus Environment

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pyrrolidone rings of PVP and -NH- groups of PANI, PANI layer could be uniformly anchored on the surface of NCM811 (refered as NCM811@PANI-PVP). Detailed structural and chemical analysis combined with electrochemical testing suggest that the thin and uniform PANI layer could not only inhibits the cracking of the secondary particles, but also enhances the cathode-electrolyte interfacial kinetics, leading to improved cyclability of the NCM811 cathode. This controllably surfactant modulated surface uniform coating strategy offers a new modification approach to stabilize layered oxide with ultra-high nickel content used as cathodes for next-generation high energy LIBs. METHODS Material synthesis: Synthesis of NCM811 materials: Ni-rich Ni0.8Co0.1Mn0.1(OH)2 precursor was prepared via a coprecipitation. In detail, 2 M aqueous metal sulfate solution was prepared from NiSO4∙7H2O (Aladdin, analytical grade, 99%), MnSO4∙H2O (Aladdin, analytical grade, 99%), CoSO4∙7H2O (Aladdin, analytical grade, 99%) in a molar ratio of 8:1:1. Then, 2 M NaOH (Aladdin, analytical grade, 96%) solution was used to keep the pH within the range of 11.0-11.5 at 50 °C by continuous stirring (900 rpm) under a N2 atmosphere. After the coprecipitation reaction, the hydroxide precursors (Ni0.8Co0.1Mn0.1(OH)2) were collected through washing, filtering and drying. To synthesize LiNi0.8Co0.1Mn0.1O2 cathode, as-prepared Ni0.8Co0.1Mn0.1(OH)2 precursors were ground with LiOH·H2O (Aladdin, analytical grade, 99%) at a molar ratio of 1:1.03, followed by sintering at 800 oC for 15 h under an O2 atmosphere (≥99.999%).



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Coating process: The as-prepared NCM811 material (2.0 g) was added into N-methyl-2pyrrolidinone (NMP) solvent (200 mL, 3A Chemicals, analytical grade, 99.5%). Then, PVP (0.1 g, Aladdin, average Mw 24000) was dispersed into above solution under stirring for 20 min. Finally, PANI (0.5 g, Aladdin, average Mw 50000-60000, 98%) was immersed and stirred vigorously for 2 h at 50 °C. The products were collected after washing, filtering, and drying at 100 °C in a vacuum for 10 h to obtain NCM811@PANI-PVP materials. Similarly, NCM811@PANI materials were synthesized following the same way but without adding PVP.

Characterizations: The crystalline structures and lattice parameters of as-prepared materials were characterized through using X-ray diffraction (XRD) on a Rigaku X-ray diffractometer (D/Max2400, Cu Kα, λ = 1.54056 Å). X-ray Rietveld refinement was carried out through Fullprof program. The X-ray photoelectron spectroscopy (XPS) measurements were characterized on a Thermo ESCALAB 250Xi XPS spectrometer (Al Kα, 1486.6 eV). The in situ Raman spectra were obtained on a Renishaw inVia Raman spectrometer (λ = 633 nm). The FT-IR spectra were performed through using a Nicolet 6700 FT-IR spectrometer (wavenumber range: 500-2000 cm-1). The morphology and the microstructure of the materials were performed via scanning electron microscopy (SEM, TESCAN MIRA3, accelerating voltage: 20 kV) and high-resolution transmission electronmicroscopy (HRTEM, JEOL JEM-2100, 300 kV). Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) were performed at Mettler-Toledo TGA DSC 1 Stare system. 6 ACS Paragon Plus Environment

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Electrochemical measurements: To assemble cells for electrochemical testing, 2016 coin-type cells were used with Li metal as the counter electrode. Cathode electrode was composed of active material (NCM811, NCM811@PANI or NCM811@PANI-PVP), carbon black, and PVDF in a weight ratio of 80:10:10 using N-methyl-2-pyrrolidinone as solvent. The mixed slurries were doctorbladed onto an Al foil. The active mass loadings of the cathode are around 4.4-4.6 mg cm-2. The electrolyte was composed of 1 M LiPF6 in dimethyl carbonate: ethylene carbonate: ethyl methyl carbonate (1: 1: 1 by volume). Galvanostatic charge-discharge and rate tests were carried out on a Neware battery testing system (CT-3008W) within a voltage window of 2.8-4.3 V (vs. Li/Li+) at 25 °C. Cyclic voltammetry (CV) and Electrochemical impedance spectroscopy (EIS) were performed on an electrochemical workstation (BioLogic-VMP3). CV was carried out with a scan rate of 0.2 mV s-1 in the voltage range of 2.8-4.3 V. EIS analysis was performed in the frequency range of 100 kHz to 10 mHz. The galvanostatic intermittent titration technique (GITT) test was carried out by using current pulses (100 mA g-1) with a duration of 10 min and a relaxation process over 1 h.

Results and discussion Figure 1 illustrates the mechanism of PVP surfactant-induced uniform coating of PANI onto the NCM811 surface to form NCM811@PANI-PVP. As shown in Figure 1a, PANI polymers randomly distribute on the surface of NCM811 or crystallize as separate particles without pre-treating the surface of NCM811 with PVP. This phenomenon is mainly due to the absence of bonding effects 7 ACS Paragon Plus Environment


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between PANI and NCM811 particles. Interestingly, after adding PVP, a uniform and thin PANI layers was grown on the surface of NCM811 owing to the bonding effect between the PVP and PANI molecules. Firstly, because PVP donate a pair of electrons from the carbonyl oxygen to the metal cations on the surface of NCM811, or to the formation of complicated bonds between nitrogen in the five-membered nitrogen-containing heterocycles and

Figure 1. (a) Schematic illustration of the preparation of NCM811@PANI-PVP, (b) the possible reaction among NCM811, PVP and PANI, and (c) the crosslinking reaction for PANI polymers. 8 ACS Paragon Plus Environment

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the metal cations, PVP can be easily anchored on NCM811.33-35 Then, the strong hydrogen-bond interaction between pyrrolidone rings of PVP and -NH- groups of PANI leads to PANI polymers tightly absorbing on the surface of NCM811, resulting in uniform coating of PANI on the surface of NCM811 (Figure 1b). Moreover, PVP can serves as “bridge” to link NCM811 and limit the bonding amount of PANI facilitating ultra-thin and very homogeneous PANI conductive layer coating on the surface of NCM811 cathode. Finally, because of the crosslinking reaction, the outside PANI polymers can easily form uniform and thin PANI layer (Figure 1c).



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Figure 2. SEM images of NCM: (a, b and c) NCM811, (d, e and f) NCM811@PANI, (g and h) NCM811@PANI-PVP, and (i-l) corresponding selected regions of SEM images for NCM811@PANI-PVP. The corresponding EDX mapping images of (m1) Ni, (m2) Co, (m3) Mn, and (m4) N for NCM811@PANI-PVP.

Figure 3. HRTEM images: (a) NCM811 (b) NCM811@PANI , (c) NCM811@PANI-PVP, (d) TEM image of NCM811@PANI-PVP, and (e-i) corresponding selected regions of HRTEM images for NCM811@PANI-PVP.


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The morphologies of NCM811, NCM811@PANI and NCM811@PANI-PVP are shown in Figure 2. The SEM images of pristine NCM811 show a sphere morphology (7-10 μm in diameter), which is composed of nanoparticles with sizes of 200-300 nm (Figure 2a-c). Figure S1 exhibits the nanoparticles morphology of pristine PANI polymers before crosslinking reaction. Figure 2d-f show the SEM images of the NCM811@PANI particles after coated with PANI but without pretreatment with PVP. Clearly, the NCM811@PANI particles could not be completely coated by PANI (Figure 2f). In detail, PANI particles randomly distribute on the surface of NCM811@PANI or crystallize as separate particles (Figure 2d). As shown in Figure 2j, rare random particles of PANI can be observed indicate that the PANI has been anchored on NCM811@PANI-PVP with the assistance of PVP. In detail, as shown in Figure 2h-l, the primary particles of NCM811 completely disappear and uniform PANI layers reveal that PVP can effectively induce controllable growth of PANI layer on the surface of NCM811. The EDX elemental mapping images of NCM811@PVP, NCM811@PANI and NCM811@PANI-PVP particles are shown in Figure 2m1-m4, and S2. Clearly, the distribution of Ni, Co and Mn elements are very homogeneous. Nitrogen (N) was utilized as a signature element to track the spatial distribution of PVP and PANI coating layer. The content of PVP in NCM811@PVP is ultralow and PANI unevenly distribute on the surface of NCM811@PANI, while the PANI layer uniformly coats on the surface of NCM811. In order to further prove the uniformity of the coating of PANI for NCM811@PANI-PVP, several various NCM811@PANI-PVP particles are also characterized by SEM. As shown in Figure S3 and S4, different NCM811@PANI-PVP particles exhibit similar uniform distribution of N element, 11 ACS Paragon Plus Environment


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demonstrating the complete coating of PANI on the surface of NCM811@PANI-PVP. HRTEM was used to analyze the shell layer outside the NCM811 in detail. As shown in Figure 3a-c and S5, uneven PANI polymer can be observed on the surface of NCM811@PANI, while a homogeneous layer PANI with a thickness of 5-7 nm was covering on the surface of NCM811@PANI-PVP. In

Figure 4. (a) XRD patterns of the NCM811 cathodes with and without coating. Rietveld refinements of the XRD patterns of (b) NCM811, (c) NCM811@PANI, and (d) NCM811@PANIPVP. 12 ACS Paragon Plus Environment

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detail, as shown in Figure 3d-i, various regions of HRTEM images for NCM811@PANI-PVP all exhibit a uniform and thin PANI layer, proving the completely coating of PANI with the assistance of PVP. The aforementioned results clearly demonstrate the efficacy of PVP surfactant on promoting the homogeneous coating of PANI layer in NCM811 cathode materials. XRD patterns of NCM811, NCM811@PANI, and NCM811@PANI-PVP cathode materials and the corresponding Rietveld refinements are shown in Figure 4. The XRD patterns in Figure 4a can be indexed to well-developed rhombohedral R3̅m structure (α-NaFeO2 structure) corresponding to phase-pure layered NCM811 structure.38 The lattice parameters and unit cell volumes for three samples from Rietveld refinements of the XRD patterns (Figure 4b-d) are shown in Table 1. As shown, there is only a slight difference in the lattice parameters of these three cathodes which indicates that the structure of NCM811 maintains well after surface modifications. In addition, no additional diffractions from PANI polymers could be observed in the XRD patterns of Table 1. Lattice parameters of the NCM811, NCM811@PANI and NCM811@PANI-PVP cathodes.

Materials

a-axis [Å]

b-axis [Å]

c-axis [Å]

V [Å3]

NiLi (%)

NCM811

2.87212

2.87212

14.19477

101.41

2.6

NCM811@PANI

2.87312

2.87312

14.19964

101.51

2.4

NCM811@PANI-PVP

2.87087

2.87087

14.18555

101.25

2.3



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NCM811@PANI and NCM811@PANI-PVP samples because of the amorphous state and/or low content of the PANI coating. This phenomenon shows that the surface modification with PVP and PANI did not change the structure and crystallinity of the NCM811 cathode materials.

The successful coating of PANI layer on NCM811 was further demonstrated through FT-IR spectra as shown in Figure 5a. The peaks at 803 and 1109 cm-1 can be assigned to the in-plane and out of-plane bending deformation of the aromatic C-H bonds in 1,4-disubstituted aromatic ring, while the peaks located at 1229 and 1293 cm-1 should be ascribed to the stretching peaks of C-N for quinoid and benzenoid ring.39 In addition, the peak at 1473 cm-1 can be ascribed to C=C stretching deformation of benzenoid ring, while the peak at 1592 cm-1 can be ascribed to the C=N stretching vibration of quinoid ring in PANI.39-40 According to the survey XPS spectrum (Figure 5b), the signals of O 1s, Ni 2p, Co 2p and Mn 2p can be observed. While the specific N 1s peak can be only found in the NCM811@PANI and NCM811@PANI-PVP samples. In detail, the N 1s spectra of NCM811@PANI and NCM811@PANI-PVP are deconvoluted into two peaks at ~399.3 and 400.4 eV, which can be assigned to the C-N and -NH- bonds, respectively (Figure 5c).39-41 As a contrast, no peaks of N 1s can be observed in the pristine NCM811 suggesting the absence of PANI. High-resolution Ni 2p XPS spectra exhibits six peaks at 855.6/873.0 eV, 857.1/875.1 eV and 862.0/879.9 eV are assigned to Ni2+, Ni3+, and satellite peaks (Figure S6a). The Co and Mn spectra exhibit 2p3/2/2p1/2 peaks at 779.8/794.8 eV and 642.5/654.9 eV, corresponding to Co3+ and Mn4+ in NCM811, NCM811@PANI and NCM811@PANI-PVP, respectively (Figure S6b and c).41-42 14 ACS Paragon Plus Environment

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According to the results of XPS, the stoichiometric ratio of Ni : Co : Mn in three samples are all nearly 8 : 1 : 1, further demonstrating the as-prepared Ni-rich cathodes are LiNi0.8Co0.1Mn0.1O2. From TGA curves, the contents of PANI in NCM811@PANI and NCM811@PANI-PVP are 4.9%

Figure 5. (a) FTIR spectra of PANI, NCM811 and NCM811@PANI-PVP. (b) XPS surveys of NCM811, NCM811@PANI and NCM811@PANI-PVP. (c) High-resolution N 1s XPS spectra of NCM811, NCM811@PANI and NCM811@PANI-PVP. (d) TGA curves of NCM811@PANI and NCM811@PANI-PVP in air.



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and 4.6%, respectively (Figure 5d). The low contents of PANI outside the NCM811 means that capacity contribution from PANI can be ignored. As for DSC tests, the onset temperature of NCM811 and NCM811@PANI-PVP are ~258.2 oC (Figure S6d). However, the main exothermic reaction of NCM811@PANI-PVP mainly locates at 278.8 oC, which is a bit higher than that of NCM811 (273.5 oC), suggesting the great thermal stability of NCM811@PANI-PVP. CV curves of the three samples were tested at 0.2 mV s-1 within the voltage range between 2.8 and 4.3 V to investigate the delithiation-lithiation process. The initial CV curves of three cathodes are distinctive to the following CV curves, which is mainly assigned to the formation of solid electrolyte interface (SEI) layer as well as activated process during the initial lithiation process (Figure 6a and S7).43-45 During delithiation-lithiation process, the three NCM811 cathodes, similar to LiNiO2 and other Ni-rich NCM811 cathodes, experience a series of phase transitions, assigning to three pairs of redox peaks: hexagonal and monoclinic (H1 ↔ M), monoclinic and hexagonal (M ↔ H2), as well as hexagonal and hexagonal (H2 ↔ H3). As shown, the intensity of the H1 ↔ M oxidation peaks for the NCM811 and NCM811@PANI cathodes drop obviously during the initial five cycles, suggesting terrible irreversibility of the H1 ↔ M phase transition. Nevertheless, the shape and peak intensity of CV curves for NCM811@PANI-PVP cathode retains very well (Figure 6a), demonstrating excellent cyclability of the NCM811@PANI-PVP cathode due to homogeneous surface coating of conductive PANI layer.19, 46-47


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Rate capabilities of NCM811@PANI-PVP, NCM811@PANI and NCM811 were also tested from 20 to 1000 mA g-1 to further evaluate the effectiveness of PVP modified uniform PANI coating. The charge-discharge profiles of three samples under various current densities are exhibited in Figure 6b and S8. Obviously, through the charge-discharge profiles of NCM811@PANI and NCM811 cathodes at virous rates, it is clear that NCM811 materials with incomplete or without PANI layer exhibit serious working voltage drop as the rates increasing (Figure S8), while NCM811@PANI-PVP exhibits very limited drop in working voltage even at a high rate of 1000 mA g-1 (Figure 6c). As shown in Figure 5c, NCM811@PANI-PVP cathode exhibits higher capacities at different rates. Especially, NCM811@PANI-PVP cathode displays the highest capacity of 152 mA h g-1 at a high rate of 1000 mA g-1, which is much superior to those of NCM811@PANI (124 mA h g-1) and NCM811 (111 mA h g-1). The greatly improved rate capability of NCM811@PANI-PVP is assigned to Li ions fast-diffusion channel from the outside uniform PANI layer, which would be proved by GITT tests. To further reveal the function of uniform PANI layer, the cycling stability of the as-prepared three samples are compared in Figure 6d. Before cycling at 200 mA g-1, all three cathodes were first charging-discharging at a low rate of 20 mA g-1 for 5 cycles to make a thorough activation of the active samples. As shown in Figure 6d, NCM811@PANI-PVP exhibits the highest capacity retention of 88.7% compared to NCM811@PANI (80.1%) and NCM811 (66.3%). The higher capacity retention of NCM811@PANI-PVP and NCM811@PANI mainly comes from the protection effect of the outside PANI layer, which can effectively prohibit the active materials from eroded 17 ACS Paragon Plus Environment


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by hydrofluoric acid (from electrolyte: LiPF6 → PF5 + LiF, PF5 + H2O → POF3 + HF) and can provide a physical barrier to suppress side reactions during charge-discharge process.1, 48 Moreover, PANI layer plays a key role in relieving the volume contraction/expansion of the host material

Figure 6. (a) CV curves in the initial five cycles for NCM811@PANI-PVP, (b) the charge/discharge voltage profiles of the NCM811@PANI-PVP under different current densities, (c) rate performance of NCM811, NCM811@PANI and NCM811@PANI-PVP, and (d) comparison of the cycling performance of NCM811, NCM811@PANI and NCM811@PANI-PVP at 200 mA g-1. 18 ACS Paragon Plus Environment

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upon cycling. Remarkably, the capacity retention of NCM811@PANI-PVP is much better than that of NCM811@PANI owing to the completely coating PANI layer outside the NCM811@PANI-PVP under the induction of PVP. The corresponding charge-discharge profiles of three cathodes are exhibited in Figure S9. The first discharge-charge capacities of NCM811@PANI-PVP, NCM811@PANI and NCM811 are 202/216, 185/203 and 198/219, respectively. The initial coulombic efficiencies of NCM811@PANI-PVP, NCM811@PANI and NCM811 are 93.5%, 91.1% and 90.4%, respectively. The higher coulombic efficiency for NCM811@PANI-PVP can be assigned to the completely coating PANI layer, which could effectively restrain the direct contact at the interface of electrode/electrolyte, and thus reducing the loss of first irreversible capacity. During 100 cycles, the charge-discharge profiles of NCM811@PANI-PVP can still maintain well, while those for NCM811@PANI and NCM811 destroy seriously, demonstrating the excellent cycling stability of NCM811@PANI-PVP.

EIS results were fitted through utilizing the equivalent circuit (Figure S10), and the corresponding fitting results are summarized in Figure 7d and Table S1. Before testing, the electrodes were charged to 4.3 V at 100 mA g-1. As shown in Figure 7a-d, the surface-film resistance (Rsf) of the three cathodes accounts for a small portion of the total resistance during cycling. Hence, the continuous increase of charge-transfer resistance (Rct) can be considered as the dominant reason for the capacity fading of three materials.49-53 As shown in Figure 7d, NCM811 and NCM811@PANI cathodes exhibit a fast increase of Rct upon cycling. At the 100th cycle, the 19 ACS Paragon Plus Environment


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Rct values of NCM811 and NCM811@PANI are 333 and 234 Ω, respectively, which are much higher than that for that of NCM811@PANI-PVP (183 Ω), suggesting that the particle cracking and solidliquid side reaction for NCM811@PANI-PVP be well restrained by the outside uniform PANI layer. The stabilized structure of NCM811@PANI-PVP was also demonstrated from the SEM images after 50 cycles. As shown in Figure S11, the morphologies of both NCM811 and NCM811@PANI exhibit cracked particles from the whole spheres. As for NCM811@PANI-PVP, the intact spherical morphology proving that uniform and compact PANI layer can effectively restrain cracking. Indeed, the corresponding TEM image of NCM811@PANI-PVP still displays obvious amorphous PANI layer outside the NCM811@PANI-PVP, proving the stability of PANI layer upon chargingdischarging process (Figure S12). GITT test was utilized to investigate the diffusion coefficients of Li ions for three samples following the Fick’s second law (the detailed was described in the Supporting Information).54-55 Figure S13a-c exhibit the GITT curves of NCM811, NCM811@PANI and NCM811@PANI-PVP upon initial lithiation- delithiation process, respectively. The calculation results of diffusion coeffcients for three cathodes are shown in Figure 7e and f. During the delithiation-lithiation process, NCM811@PANI-PVP exhibits much higher diffusion coeffcients, demonstrating that the outside PANI layer can facilite the diffusion of Li ions. This result can strongly explain the superior rate capability of NCM811@PANI-PVP above. In-situ XRD was utilized to reveal the reaction mechanism and structural stability of NCM811@PANI-PVP upon lithiation-delithiation process. In situ XRD patterns show the detailed evolutions of the (003), (101), and (104) diffraction peaks of the rhombohedral (R3̅m) 20 ACS Paragon Plus Environment

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Figure 7. Nyquist plots of electrochemical impedances measured at 4.3 V (charged state) of NCM811, NCM811@PANI and NCM811@PANI-PVP at the (a) 1st, (b) 30th and (c) 100th. (d) Comparison of the surface film and charge transfer resistances as a function of the number of cycles. Diffusion coefficients calculated from GITT potential profiles as a function of potential during (e) delithiation, and (f) lithiation.

LiNi0.8Co0.1Mn0.1O2 phase upon lithiation-delithiation process (Figure 8a and b). The strong peak at 44.74o is ascribed to the diffraction peaks of Al foil. (003) and (101) peaks reflect the changes in the length of the c and a axes of NCM811@PANI-PVP unit cell, respectively. During delithiation process, (003) peak shifts to lower angles as potential increasing, assigning to the expanding lattice parameter “c”. This process is mainly ascribed to the enhanced repulsion between the oxygen layers, because of the weaker screening effect of depleted Li layers, meaning Li ions are 21 ACS Paragon Plus Environment


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deintercalated.56-57 In addition, besides the main (003) peak which indicates the presence of H1 structure, as the voltage increasing, a short plateau during charging at 4.2 V can be observed, indicating a two-phase mixture of H2 and H3. Based on the literature reported by Chandan group, when the voltage further increases above 4.22 V, within the range of 4.22-4.30 V, (003) peak shifts back to higher angles. This “unusual” behavior of (003) peak is mainly assigned to the formation of obvious H2 phase.57 Through comparison, this phenomenon is inconspicuous for NCM811@PANI-PVP, indicating that the outside PANI layer can effectively inhibit the phase transition during charge-discharge process and thus improving the stability of NCM811@PANIPVP. Meanwhile, (101) peak shifts continuously to higher angles, suggesting that a parameter contract during this stage of the charge due to the oxidation of transition metal ions, which have smaller ionic radius when their oxidation state enhances.38 As for (104) peak, the intensity become weak and shifts to higher angles gradually. This phenomenon is ascribed to the appearance of vacancies due to the deintercalation of Li ions in lithium layer and then Ni2+ occupies these sites. During the following discharge process, the positions and intensity of these peaks can largely reverse to their original state, demonstrating the great cycling stability of NCM811@PANI-PVP. Figure 8c exhibits the in situ Raman of NCM811@PANI-PVP in the range of 100-800 cm-1 at 20th charge-discharge process. According to the previous paper, the peak at 510 cm-1 is assigned to Eg band, while the peak at 525-550 cm-1 can be ascribed to A1g band.58-59 During the charging process, the fast disappearance of the A1g band can be assigned to the effects of changes in local symmetry, which is caused by Li ions deintercalation, on the v(MO6, M=Ni, Co and Mn) vibration mode. 22 ACS Paragon Plus Environment

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Figure 8. (a) In situ XRD, (b) the corresponding contour plot of diffraction patterns for (003), (101), and (104) reﬂections and (c) in situ Raman spectra of NCM811@PANI-PVP during 20th 23 ACS Paragon Plus Environment


charge-discharge at a rate of 200 mA g-1. The right spectra in (a) and (b) show the corresponding zoom-in parts for the (003), (101) and (104) peaks. The right spectra in (c) shows the zoom-in part of the Raman spectra in the range of 460-580 cm-1.

However, Eg band still exists but with a little shift to lower wavelength during charging process, which may be ascribed to two O atoms vibrate in the opposite directions parallel to the decreasing number of Li ions.57 As for discharging process, the indengsity and positions of the peaks return to their original conditions, suggesting the reversibility of reaction. Some peaks of in situ Raman are complex which still need massive effort to explain. However, through utilizing in situ XRD and in situ Raman, it can be concluded that, upon Li ions extraction/insertion, NCM811@PANIPVP cathode experiences reversible structural transformations of their initial hexagonal phase H1 to phase H2 and to coexisting phases H1+H2.

Conclusions In summary, a uniform and thin PANI conductive layer was successfully coated on the NCM 811 surface through the bonding effect between PVP and PANI molecules. Detailed structural and chemical analyses show that the uniformly coated PANI layer can efficiently inhibit the cracking of the secondary particles, suppress the sidereaction between electrode and electrolyte, and facilitate the cathode-electrolyte interfacial kinetics, thus resulting in improved electrochemical perforance of NCM811@PANI-PVP. The in-situ XRD and in-situ Raman results further confirm the crystal structure stability of NCM811@PANI-PVP during Li ions extraction and insertion 24 ACS Paragon Plus Environment

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process. Therefore, the NCM811@PANI-PVP electrode show much better rate capability as well as superior long-term cyclability (Capacity retention of 88.7% after 100 cycles at 200 mA g-1) compared to uncoated and unevenly coated samples. The strategy of surfactant induced precisely surface coating utilized in this work opens a novel avenue for surface modifications to improve the cycling stability of next generation advanced high energy battery materials.

ASSOCIATED CONTENT

Supporting Information Available: High-resolution XPS spectra; CV curves; electrochemical performance tests; equivalent circuit; cycled SEM and TEM images; GITT potential profiles; impedance parameters of the fitting equivalent circuit. This material is available free of charge via the Internet at http:// pubs.acs.org.

AUTHOR INFORMATION

Corresponding Author

*E-mails: [email protected] (Zhouguang Lu) Notes

The authors declare no competing financial interest.



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Acknowledgments This work was financially supported by the Basic Research Project of the Science and Technology Innovation Commission of Shenzhen (No. JCYJ20170412153139454), the Guangdong Innovative and Entrepreneurial Research Team Program (No. 2016ZT06G587), and the National Natural Science Foundation of China (No. 21875097, and No. 21671096).

REFERENCES

(1)

Yan, P.; Zheng, J.; Liu, J.; Wang, B.; Cheng, X.; Zhang, Y.; Sun, X.; Wang, C.; Zhang, J.G. Tailoring Grain Boundary Structures and Chemistry of Ni-rich Layered Cathodes for Enhanced Cycle Stability of Lithium-Ion batteries. Nat. Energy 2018, 3, 600-605.

(2)

Sun, Y.-K.; Myung, S.-T.; Park, B.-C.; Prakash, J.; Belharouak, I.; Amine, K. High-Energy Cathode Material for Long-Life and Safe Lithium Batteries. Nat. Mater. 2009, 8, 320-324.

(3)

Gan, Q.; Zhao, K.; He, Z.; Liu, S.; Li, A., Zeolitic Imidazolate Framework-8-Derived NDoped Porous Carbon Coated Olive-Shaped FeOx Nanoparticles for Lithium Storage. J. Power Sources 2018, 384, 187-195.

(4)

Lecce, D. D.; Andreotti, P.; Boni, M.; Gasparro, G.; Rizzati, G.; Hwang, J. Y.; Sun, Y. K.; Hassoun, J. Multiwalled Carbon Nanotubes Anode in Lithium-Ion Battery with LiCoO2, Li[Ni1/3Co1/3Mn1/3]O2 and LiFe1/4Mn1/2Co1/4PO4 Cathodes. ACS Sustain. Chem. Eng. 2018, 6, 3225-3232. 26 ACS Paragon Plus Environment

Page 27 of 46 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(5)

Zhang, W.; Richter, F. H.; Culver, S. P.; Leichtweiß, T.; Lozano, J. G.; Dietrich, C.; Bruce, P. G.; Zeier, W. G.; Janek, J. Degradation Mechanisms at the Li10GeP2S12/LiCoO2 Cathode Interface in an All-Solid-State Lithium Ion Battery. ACS Appl. Mater. Inter. 2018, 10, 22226-22236.

(6)

Yun, G. Z.; Du, Y.; Jia, C.; Zhou, M.; Li, F.; Wang, X.; Wang, Q. Unleashing the Power and Energy of LiFePO4-Based Redox Flow Lithium Battery with a Bifunctional Redox Mediator. J. Am. Chem. Soc. 2017, 139, 6286-6289.

(7)

Wang, X.; Feng, Z.; Huang, J.; Deng, W.; Li, X.; Zhang, H.; Wen, Z. Graphene-Decorated Carbon-Coated LiFePO4 Nanospheres as A High-Performance Cathode Material for Lithium-Ion Batteries. Carbon 2018, 127, 149-157.

(8)

Saat, G.; Balci, F. M.; Alsaç, E. P.; Karadas, F.; Dag, Ö. J. S. Mesoporous Thin Films: Molten Salt Assisted Self‐Assembly: Synthesis of Mesoporous LiCoO2 and LiMn2O4 Thin Films and Investigation of Electrocatalytic Water Oxidation Performance of Lithium Cobaltate. Small 2018, 14, 1870003.

(9)

Ben, L.; Yu, H.; Chen, B.; Chen, Y.; Gong, Y.; Yang, X.; Gu, L.; Huang, X. Unusual Spinel-to-Layered Transformation in LiMn2O4 Cathode Explained by Electrochemical and Thermal Stability Investigation. ACS Appl. Mater. Inter. 2017, 9, 35463-35475.



Page 28 of 46

(10) Shi, J. L.; Qi, R.; Zhang, X. D.; Wang, P. F.; Fu, W. G.; Yin, Y. X.; Xu, J.; Wan, L. J.; Guo, Y. G. High-Thermal- and Air-Stability Cathode Material with ConcentrationGradient Buffer for Li-Ion Batteries. ACS Appl. Mater. Inter. 2017, 9, 42829-42835.

(11) Shi, J. L.; Xiao, D. D.; Ge, M.; Yu, X.; Chu, Y.; Huang, X.; Zhang, X. D.; Yin, Y. X.; Yang, X. Q.; Guo, Y. G.; Gu, L.; Wan, L. J. High-Capacity Cathode Material with High Voltage for Li-Ion Batteries. Adv. Mater. 2018, 30, 1705575.

(12) Wang, L.-P.; Zhang, X.-D.; Wang, T.-S.; Yin, Y.-X.; Shi, J.-L.; Wang, C.-R.; Guo, Y.-G. Ameliorating the Interfacial Problems of Cathode and Solid-State Electrolytes by Interface Modification of Functional Polymers. Adv. Energy Mater. 2018, 8, 1801528.

(13) Kim, U. H.; Jun, D. W.; Park, K. J.; Zhang, Q.; Kaghazchi, P.; Aurbach, D.; Major, D. T.; Goobes, G.; Dixit, M.; Leifer, N.; Wang, C. M.; Yan, P.; Ahn, D.; Kim, K. H.; Yoon, C. S.; Sun, Y. K. Pushing the Limit of Layered Transition Metal Oxide Cathodes for HighEnergy Density Rechargeable Li Ion Batteries. Energ. Environ. Sci. 2018, 11, 1271-1279.

(14) Su, Y.; Chen, G.; Chen, L.; Li, W.; Zhang, Q.; Yang, Z.; Lu, Y.; Bao, L.; Tan, J.; Chen, R. Exposing the {010} Planes by Oriented Self-Assembly with Nanosheets To Improve the Electrochemical Performances of Ni-Rich Li[Ni0.8Co0.1Mn0.1]O2 Microspheres. ACS Appl. Mater. Inter. 2018, 10, 6407-6414.


Page 29 of 46 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(15) Manthiram, A.; Knight, J. C.; Myung, S.-T.; Oh, S.-M.; Sun, Y.-K. Nickel-Rich and Lithium-Rich Layered Oxide Cathodes: Progress and Perspectives. Adv. Energy Mater. 2016, 6, 1501010.

(16) Lee, Y. S.; Shin, W. K.; Kannan, A. G.; Koo, S. M.; Kim, D. W. Improvement of the Cycling Performance and Thermal Stability of Lithium-Ion Cells by Double-Layer Coating of Cathode Materials with Al2O3 Nanoparticles and Conductive Polymer. ACS Appl. Mater. Inter. 2015, 7, 13944-13951.

(17) Zheng, J.; Yan, P.; Estevez, L.; Wang, C.; Zhang, J.-G. Effect of Calcination Temperature on the Electrochemical Properties of Nickel-Rich LiNi0.76Mn0.14Co0.10O2 cathodes for lithium-ion batteries. Nano Energy 2018, 49, 538-548

(18) Zhao, J.; Zhang, W.; Huq, A.; Misture, S. T.; Zhang, B.; Guo, S.; Wu, L.; Zhu, Y.; Chen, Z.; Amine, K.; Pan, F.; Bai, J.; Wang, F. In Situ Probing and Synthetic Control of Cationic Ordering in Ni-Rich Layered Oxide Cathodes. Adv. Energy Mater. 2017, 7, 1601266.

(19) Wu, Z.; Han, X.; Zheng, J.; Wei, Y.; Qiao, R.; Shen, F.; Dai, J.; Hu, L.; Xu, K.; Lin, Y.; Yang, W.; Pan, F. Depolarized and Fully Active Cathode Based on Li(Ni0.5Co0.2Mn0.3)O2 Embedded in Carbon Nanotube Network for Advanced Batteries. Nano Lett. 2014, 14, 4700-4706.



Page 30 of 46

(20) Ju, S. H.; Kang, I. S.; Lee, Y. S.; Shin, W. K.; Kim, S.; Shin, K.; Kim, D. W. Improvement of the Cycling Performance of LiNi0.6Co0.2Mn0.2O2 Cathode Active Materials by A DualConductive Polymer Coating. ACS Appl. Mater. Inter. 2014, 6, 2546-2552.

(21) Armstrong, G.; Armstrong, A. R.; Bruce, P. G.; Reale, P.; Scrosati, B. TiO2(B) Nanowires as an Improved Anode Material for Lithium-Ion Batteries Containing LiFePO4 or LiNi0.5Mn1.5O4 Cathodes and a Polymer Electrolyte. Adv. Mater. 2006, 18, 2597-2600.

(22) Zhang, X.; Belharouak, I.; Li, L.; Lei, Y.; Elam, J. W.; Nie, A.; Chen, X.; Yassar, R. S.; Axelbaum, R. L. Structural and Electrochemical Study of Al2O3 and TiO2 Coated Li1.2Ni0.13Mn0.54Co0.13O2 Cathode Material Using ALD. Adv. Energy Mater. 2013, 3, 12991307.

(23) Baggetto, L.; Dudney, N. J.; Veith, G. M. Surface Chemistry of Metal Oxide Coated Llithium Manganese Nickel Oxide Thin Film Cathodes Studied by XPS. Electrochim. Acta 2013, 90, 135-147.

(24) Wang, J.; Du, C.; Yan, C.; He, X.; Song, B.; Yin, G.; Zuo, P.; Cheng, X. Al2O3 Coated Concentration-Gradient Li[Ni0.73Co0.12Mn0.15]O2 Cathode Material by Freeze Drying for Long-Life Lithium Ion Batteries. Electrochim. Acta 2015, 174, 1185-1191.


Page 31 of 46 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(25) Zhao, T.; Li, L.; Chen, R.; Wu, H.; Zhang, X.; Chen, S.; Xie, M.; Wu, F.; Lu, J.; Amine, K. Design of Surface Protective Layer of LiF/FeF3 Nanoparticles in Li-Rich Cathode for High-Capacity Li-Ion Batteries. Nano Energy 2015, 15, 164-176.

(26) Xie, J.; Sendek, A. D.; Cubuk, E. D.; Zhang, X.; Lu, Z.; Gong, Y.; Wu, T.; Shi, F.; Liu, W.; Reed, E. J.; Cui. Y. Atomic Layer Deposition of Stable LiAlF4 Lithium Ion Conductive Interfacial Layer for Stable Cathode Cycling. ACS Nano 2017, 11, 7019-7027.

(27) Liu, W.; Oh, P.; Liu, X.; Myeong, S.; Cho, W.; Cho, J. Countering Voltage Decay and Capacity Fading of Lithium-Rich Cathode Material at 60 °C by Hybrid Surface Protection Layers. Adv. Energy Mater. 2015, 5, 1500274.

(28) Zheng, F.; Yang, C.; Xiong, X.; Xiong, J.; Hu, R.; Chen, Y.; Liu, M. Nanoscale Surface Modification of Lithium-Rich Layered-Oxide Composite Cathodes for Suppressing Voltage Fade. Angew. Chem. Int. Ed. Engl. 2015, 54, 13058-13062.

(29) Jo, C.-H.; Cho, D.-H.; Noh, H.-J.; Yashiro, H.; Sun, Y.-K.; Myung, S. T. An Effective Method to Reduce Residual Lithium Compounds on Ni-Rich Li[Ni0.6Co0.2Mn0.2]O2 Active Material Using A Phosphoric Acid Derived Li3PO4 Nanolayer. Nano Res. 2014, 8, 14641479.



Page 32 of 46

(30) Jeong, J. M.; Choi, B. G.; Lee, S. C.; Lee, K. G.; Chang, S. J.; Han, Y. K.; Lee, Y. B.; Lee, H. U.; Kwon, S.; Lee, G.; Lee, C. S.; Huh, Y. S. Hierarchical Hollow Spheres of Fe2O3@Polyaniline for Lithium Ion Battery Anodes. Adv. Mater. 2013, 25, 6250-6255.

(31) Yang, L.; Wang, S.; Mao, J.; Deng, J.; Gao, Q.; Tang, Y.; Schmidt, O. G. Hierarchical MoS2/Polyaniline Nanowires with Excellent Electrochemical Performance for Lithium-Ion batteries. Adv. Mater. 2013, 25, 1180-1184.

(32) Wang, G.; Peng, J.; Zhang, L.; Zhang, J.; Dai, B.; Zhu, M.; Xia, L.; Yu, F. TwoDimensional SnS2@PANI Nanoplates with High Capacity and Excellent Stability for Lithium-Ion Batteries. J. Mater. Chem. A 2015, 3, 3659-3666.

(33) Qian, X.-f.; Yin, J.; Feng, S.; Liu, S.-h.; Zhu, Z.-k. Preparation and Characterization of Polyvinylpyrrolidone Films Containing Silver Sulfide Nanoparticles. J. Mater. Chem. 2001, 11, 2504-2506.

(34) Lim, S.; Cho, J. PVP-Functionalized Nanometre Scale metal Oxide Coatings for Cathode Materials: Successful Application to LiMn2O4 Spinel Nanoparticles. Chem. Commun. 2008, 37, 4472-4474.

(35) Fu, G.; Ma, L.; Gan, M.; Zhang, X.; Jin, M.; Lei, Y.; Yang, P.; Yan, M. Fabrication of 3D Spongia-Shaped

Polyaniline/MoS2

Nanospheres

Composite

Assisted

by


Page 33 of 46 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Polyvinylpyrrolidone (PVP) for High-Performance Supercapacitors. Synthetic Met. 2017, 224, 36-45.

(36) Meng, Q.; Zhang, W.; Hu, M.; Jiang, J. Mesocrystalline Coordination Polymer as A Promising Cathode for Sodium-Ion Batteries. Chem. Commun. 2015, 52, 1957-1960.

(37) Fu, G.; Ma, L.; Gan, M.; Zhang, X.; Jin, M.; Lei, Y.; Yang, P.; Yan, M. Fabrication of 3D Spongia-Shaped

Polyaniline/MoS2

Nanospheres

Composite

Assisted

by

Polyvinylpyrrolidone (PVP) for High-Performance Supercapacitors. Synthetic Met. 2017, 224, 36-45.

(38) Lee, W.; Muhammad, S.; Kim, T.; Kim, H.; Lee, E.; Jeong, M.; Son, S.; Ryou, J.-H.; Yoon, W.-S. New Insight into Ni-Rich Layered Structure for Next-Generation Li Rechargeable Batteries. Adv. Energy Mater. 2018, 8, 1701788.

(39) Gan, Q.; Zhao, K.; He, Z.; Liu, S.; Li, A. Zeolitic Imidazolate Framework-8-Derived NDoped Porous Carbon Coated Olive-Shaped FeOx Nanoparticles Enabling Superior Electrochemical Performance for Lithium Storage. J. Power Source 2018, 384, 187-195.

(40) Cao, Y.; Qi, X.; Hu, K.; Wang, Y.; Gan, Z.; Li, Y.; Hu, G.; Peng, Z.; Du, K. Conductive Polymers Encapsulation to Enhance Electrochemical Performance of Ni-Rich Cathode Materials for Li-Ion Batteries. ACS Appl. Mater. Inter. 2018, 10, 18270-18280.



Page 34 of 46

(41) Lin, C.; Zhang, Y.; Chen, L.; Lei, Y.; Ou, J.; Guo, Y.; Yuan, H.; Xiao, D. Hydrogen Peroxide Assisted Synthesis of LiNi1/3Co1/3Mn1/3O2 as High-Performance Cathode for Lithium-Ion Batteries. J. Power Sources 2015, 280, 263-271.

(42) Shi, S.; Wang, T.; Cao, M.; Wang, J.; Zhao, M.; Yang, G. Rapid Self-Assembly Spherical Li1.2Mn0.56Ni0.16Co0.08O2 with Improved Performances by Microwave Hydrothermal Method as Cathode for Lithium-Ion Batteries. ACS Appl. Mater. Inter. 2016, 8, 1147611487.

(43) Liu, W.; Li, X.; Xiong, D.; Hao, Y.; Li, J.; Kou, H.; Yan, B.; Li, D.; Lu, S.; Koo, A.; Adair, K.; Sun, X. Significantly Improving Cycling Performance of Cathodes in Lithium Ion Batteries: The Effect of Al2O3 and LiAlO2 Coatings on LiNi0.6Co0.2Mn0.2O2. Nano Energy 2018, 44, 111-120.

(44) Zhang, X. D.; Shi, J. L.; Liang, J. Y.; Yin, Y. X.; Zhang, J. N.; Yu, X. Q.; Guo, Y. G. Suppressing Surface Lattice Oxygen Release of Li-Rich Cathode Materials via Heterostructured Spinel Li4Mn5O12 Coating. Adv. Mater. 2018, 30, 1801751.

(45) Liang, J. Y.; Zeng, X. X.; Zhang, X. D.; Wang, P. F.; Ma, J. Y.; Yin, Y. X.; Wu, X. W.; Guo, Y. G.; Wan, L. J. Mitigating Interfacial Potential Drop of Cathode-Solid Electrolyte via Ionic Conductor Layer To Enhance Interface Dynamics for Solid Batteries. J. Am. Chem. Soc. 2018, 140, 6767-6770. 34 ACS Paragon Plus Environment

Page 35 of 46 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(46) Jan, S. S.; Nurgul, S.; Shi, X.; Xia, H.; Pang, H. Improvement of Electrochemical Performance of LiNi0.8Co0.1Mn0.1O2 Cathode Material by Graphene Nanosheets Modification. Electrochim. Acta 2014, 149, 86-93.

(47) Xia, Y.; Zheng, J.; Wang, C.; Gu, M. Designing Principle for Ni-Rich Cathode Materials with High Energy Density for Practical Applications. Nano Energy 2018, 49, 434-452.

(48) Oh, P.; Oh, S. M.; Li, W.; Myeong, S.; Cho, J.; Manthiram, A. High-Performance Heterostructured Cathodes for Lithium-Ion Batteries with a Ni-Rich Layered Oxide Core and a Li-Rich Layered Oxide Shell. Adv. Sci. 2016, 3, 1600184.

(49) Gan, Q.; He, H.; Zhao, K.; He, Z.; Liu, S.; Yang, S. Plasma-Induced Oxygen Vacancies in Urchin-Like Anatase Titania Coated by Carbon for Excellent Sodium-Ion Battery Anodes. ACS Appl. Mater. Inter. 2018, 10, 7031-7042.

(50) He, H.; Gan, Q.; Wang, H.; Xu, G.; Zhang, X.; Huang, D.; Fu, F.; Tang, Y.; Aminec, K.; Shao, M. Structure-Dependent Performance of TiO2/C as Anode Material for Na-Ion Batteries. Nano energy 2018, 44, 217-227.

(51) He, H.; Huang, D.; Pang, W.; Sun, D.; Wang, Q.; Tang, Y.; Ji, X.; Guo, Z.; Wang, H. Plasma-Induced Amorphous Shell and Deep Cation-Site S Doping Endow TiO2 with Extraordinary Sodium Storage Performance. Adv. Mater. 2018, 30, 1801013.



Page 36 of 46

(52) Wu, S.; Zhu, Y.; Huo, Y.; Luo, Y.; Zhang, L.; Wan, Y.; Nan, B.; Cao, L.; Wang, Z.; Li, M.; Yang, M.; Cheng, H.; Lu, Z. Bimetallic Organic Frameworks Derived CuNi/Carbon Nanocomposites as Efficient Electrocatalysts for Oxygen Reduction Reaction. Sci. China Mater. 2017, 60, 654-663.

(53) Wu, S.; Wang, W.; Li, M.; Cao, L.; Lyu, F.; Yang, M.; Wang, Z.; Shi, Y.; Nan, B.; Yu, S.; Sun, Z.; Liu, Y.; Lu, Z. Highly Durable Organic Electrode for Sodium-Ion Batteries via A Stabilized α-C Radical Intermediate. Nat. Commun. 2016, 7, 13318.

(54) Jian, Z.; Xing, Z.; Bommier, C.; Li, Z.; Ji, X. Hard Carbon Microspheres: Potassium‐Ion Anode Versus Sodium‐Ion Anode. Adv. Energy Mater. 2016, 6, 1501874.

(55) Cao, B.; Zhang, Q.; Liu, H.; Xu, B.; Zhang, S.; Zhou, T.; Mao, J.; Pang, W. K.; Guo, Z.; Li, A.; Zhou, J.; Chen, X.; Song, H. Graphitic Carbon Nanocage as a Stable and High Power Anode for Potassium-Ion Batteries. Adv. Energy Mater. 2018, 8, 1801149.

(56) Villevieille, C.; Lanz, P.; Bünzli, C.; Novák, P. Bulk and Surface Analyses of Ageing of A 5V-NCM Positive Electrode Material for Lithium-Ion Batteries. J. Mater. Chem. A 2014, 2, 6488-6493.

(57) Ghanty, C.; Markovsky, B.; Erickson, E. M.; Talianker, M.; Haik, O.; Tal-Yossef, Y.; Mor, A.; Aurbach, D.; Lampert, J.; Volkov, A.; Shin, J.-Y.; Garsuch, A.; Chesneau, F. F.; Erk, C. Li+-Ion Extraction/Insertion of Ni-Rich Li1+x(NiyCozMnz)wO2 (0.005

Polyvinylpyrrolidone-Induced Uniform Surface-Conductive Polymer

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