Pristine NCM Research Articles

The Effect of Excessive Sulfate in the Li-Ion Battery Leachate on the Properties of Resynthesized Li[Ni1/3Co1/3Mn1/3]O2.

In order to examine the effect of excessive sulfate in the leachate of spent Li-ion batteries (LIBs), LiNi1/3Co1/3Mn1/3O2 (pristine NCM) and sulfate-containing LiNi1/3Co1/3Mn1/3O2 (NCMS) are prepared by a co-precipitation method. The crystal structures, morphology, surface species, and electrochemical performances of both cathode active materials are studied by scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and charge-discharge tests. The XRD patterns and XPS results identify the presence of sulfate groups on the surface of NCMS. While pristine NCM exhibits a very dense surface in SEM images, NCMS has a relatively porous surface, which could be attributed to the sulfate impurities that hinder the growth of primary particles. The charge-discharge tests show that discharge capacities of NCMS at C-rates, which range from 0.1 to 5 C, are slightly decreased compared to pristine NCM. In dQ/dV plots, pristine NCM and NCMS have the same redox overvoltage regardless of discharge C-rates. The omnipresent sulfate due to the sulfuric acid leaching of spent LIBs has a minimal effect on resynthesized NCM cathode active materials as long as their precursors are adequately washed.

A practical Li-ion full cell with a Li-ion conductor coating cathode and graphite anode: Strong interface stability and superior electrochemical performance

LiNi0.5Co0.2Mn0.3O2 (NCM523) was coated by a lithium-ion conductor Li3PO4 layer using a pre-coating treatment and solid state method. The physicochemical characteristics were investigated by XRD, SEM, TEM and XPS. Li3PO4 coating layer maintained the crystal structure of NCM523 cathode. The cathode with 3.0 wt% Li3PO4 coating (P0.03-NCM) exhibited outstanding rate capability (169.3 mAh g−1 at 0.2 C) and cycling retention of 92.23% at 1 C after 150 cycles, whereas the pristine NCM exhibited a capacity retention of only 77.84%. The electrochemical performance of the full-cell (P0.03-NCM as the cathodes and graphite as the anodes) showed high cycle retention of 82.92% after 100 cycles. The Li3PO4 coating layer acted as a physical barrier and alleviated the degradation behaviors of NCM523. This research work provided insights for the commercial application of ternary layered cathodes.

Dual function Li-reactive coating from residual lithium on Ni-rich NCM cathode material for Lithium-ion batteries

In this study, lithium phosphate (Li3PO4) is coated on the surface of Ni-rich LiNi0.91Co0.06Mn0.03O2 cathode material to enhance its cyclability and rate performance. The process is carried-out by achieving dual benefits, reduction of residual lithium compounds by converting them into Li3PO4 coating material. The 0.1 mol.% Li3PO4 (LiP) sample exhibits a capacity retention of 82% while the pristine NCM shows only 68.1% after 100 cycles. In addition, the LiP-0.1 NCM delivers high discharge capacities (161.9 mAh g−1 at 3C, 144.3 mAh g−1 at 4C and 94.6 mAh g−1 at 5C) as compared to the pristine NCM (129.3 mAh g−1 at 3C, 67.4 mAh g−1 at 4C and 33.4 mAh g−1 at 5C) in the voltage range of 3.0–4.3 V. In addition, the irreversible phase transition has also suppressed in the coated sample which is confirmed by cyclic voltammetry. Our study suggests that Li3PO4 coating reduces the polarization and acts as protecting layer between the electrode and electrolyte that results in the superior electrochemical performance.

One-step selective recovery and cyclic utilization of valuable metals from spent lithium-ion batteries via low-temperature chlorination pyrolysis

An efficient and environmentally friendly closed loop process combing low-temperature chlorination pyrolysis with water leaching is proposed for one-step selective recovery and cyclic utilization of valuable metals from spent lithium-ion batteries (LIBs). First, the spent LiNixCoyMnzO2 (s-NCM) cathode materials are pyrolyzed with NH4Cl as a chlorination agent and the valuable metals (Ni, Co, Mn, Li) can be converted into readily soluble chloride which attribute to the release of HCl and NH3 from NH4Cl. After the s-NCM cathode materials treated via low-temperature chlorination pyrolysis at 300 °C for 30 min with NH4Cl/s-NCM mass ratio of 3:1, more than 99.9% of the valuable metals can be recovered by simple water leaching. Moreover, thermodynamic analysis show that the valuable metals can be converted to chloride while the impurity metals (Fe, Al) do not participate in the reaction at this temperature, which can achieve the one-step selective recovery of valuable metals. Therefore, the water leaching solution can be directly used to synthesize regenerated pristine NCM (r-NCM) cathode materials which exhibit excellent cycle and rate performance. In summary, one-step selective leaching and regeneration of valuable metals can be accomplished by low-temperature chlorination pyrolysis. The whole process reduces the energy consumption and the environmental pollution caused by alleviating the introduction of acidic or alkaline chemicals and realize the high-value utilization of waste resources.

Functional Passivation Interface of LiNi0.8Co0.1Mn0.1O2 toward Superior Lithium Storage

AbstractThe fast capacity/voltage fading with a low rate capability has challenged the commercialization of layer‐structured Ni‐rich cathodes in lithium‐ion batteries. In this study, an ultrathin and stable interface of LiNi0.8Mn0.1Co0.1O2 (NCM) is designed via a passivation strategy, dramatically enhancing the capacity retention and operating voltage stability of cathode at a high cut‐off voltage of 4.5 V. The rebuilt interface as a stable path for Li+ transport, would strengthen the cathode–electrolyte interface stability, and restrain the detrimental factors for cathode–electrolyte interfacial reactions, intergranular cracking and irreversible phase transformation from layered to spinel, even salt‐rock phase. The as‐optimized NCM displays a higher cyclability (i.e., 206.6 mA h g−1 at 0.25 C (50 mA g−1) with 92.0% capacity retention over 100 cycles) and a better rate capability (141.0 and 112.6 mA h g−1 at 12.5 and 25 C, respectively) than pristine NCM (205.0 mA h g−1 with 73.0% capacity retention at 0.25 C; 120.9 and 93.1 mA h g−1 at 12.5 and 25 C, respectively).

Effects of lithium tungsten oxide coating on LiNi0.90Co0.05Mn0.05O2 cathode material for lithium-ion batteries

A lithium tungsten oxide (LWO) coating layer is introduced on the surface of the Ni-rich layered LiNi0.90Co0.05Mn0.05O2 (NCM) cathode material to improve the electrochemical performance such as cycle stability and rate capability. The tungsten oxide is converted to a lithium tungsten oxide by reacting with lithium residues such as LiOH and Li2CO3 on the surface of the Ni-rich layered LiNi0.90Co0.05Mn0.05O2 cathode material. The LWO layer is successfully coated on LiNi0.90Co0.05Mn0.05O2. The 0.5 wt% LWO-coated NCM exhibits excellent rate capability and cycling retention of 84.6% after 80 cycles compared to the pristine NCM (76.6% after 80 cycles). The role of the LWO layer is summarized as improving the surface stability and rate capability of the Ni-rich layered cathode material by acting as a protective layer between the electrolyte and the active material and a lithium-ion conductor.

Electrochemical Properties of High Nickel Content Li(Ni0.7Co0.2Mn0.1)O₂ with an Alumina Thin-Coating Layer as a Cathode Material for Lithium Ion Batteries.

The cathode material, high Nickel content Ni0.7Co0.2Mn0.1 (NCM), was synthesized by coprecipitation with NH₄OH used as a complexing agent. The prepared materials are made in the formation of spherical particles of Li(Ni0.7Co0.2Mn0.1)O₂ of several micrometers in diameter. Al₂O₃ was coated by an impregnation method and its content was gradually increased to 1, 2 and 5 wt%. As a result, 1 wt% coated Al₂O₃ compared to pristine NCM exhibited 82% and 80% retention rates at 5 C and 1 wt% Al₂O₃ coated NCM recovery at 0.2 C after 5 C showed 100%. In addition, capacity retention of 1 wt% NCM+Al gently decreased in 100 cycle life characteristics, and capacity retention of 95% or more was confirmed.

Enhancing high-voltage performance of LiNi0.8Co0.1Mn0.1O2 by coating with NASICON fast ionic conductor Li1.5Al0.5Zr1.5(PO4)3

The Li1.5Al0.5Zr1.5(PO4)3-coated LiNi0.8Co0.1Mn0.1O2 cathode material has been successfully fabricated by a sol-gel method. Combined with the results of XRD, SEM, TEM and XPS, the LAZP is coated closely on the surface of NCM and forms a film with a thickness of approximately 4 nm. The LAZP coating layer can significantly facilitate the Li+-ion diffusion rate at the interface of electrolyte/electrode on the NCM particle surface, decrease the degree of Li+/Ni2+ cation mixing, and preserve the structural stability of cathode material. The NCM@LAZP-1 cathode material maintains 78.3% after 300 cycles at 1C in voltage of 2.8–4.3 V. Furthermore, at the high cutoff voltage of 4.5 V, the modified NCM@LAZP-1 cathode is discovered to realize a sustained reversible capacities of 179.3 mA h g−1, corresponding to capacity retention of 84.8% after 200 charge/discharge cycles, while the pristine NCM cathode delivers only 112.1 mA h g−1, matching with capacity retention rate of 52.3%.

Ultra-Thin AlPO4 Layer Coated LiNi0.7Co0.15Mn0.15O2 Cathodes With Enhanced High-Voltage and High-Temperature Performance for Lithium-Ion Half/Full Batteries.

Side-reactions in LiNi1−x-yCoxMnyO2 (0≤−x+y≤1) cathode materials are one kind of the problems that would deteriorate the surface structure and the electrochemical stabilities of the cathodes, especially when they are working at high cut-off voltages and high temperatures. In this study, an ultrathin (~10 nm) AlPO4 coating layer was fabricated through a two-step “feeding” process on LiNi0.7Co0.15Mn0.15O2 (NCM) cathode materials. The structure and chemical composition of the AlPO4 coating were studied by XRD, SEM, TEM, and XPS characterizations. Further electrochemical testing revealed that the AlPO4-coated LiNi0.7Co0.15Mn0.15O2 cathode exhibited enhanced electrochemical stabilities in the case of high cut-off voltage at both 25 and 55°C. In detail, the AlPO4-coated LiNi0.7Co0.15Mn0.15O2 could deliver 186.50 mAh g−1 with 81.5% capacity retention after 100 cycles at 1C over 3–4.5 V in coin cell, far higher than the 71.4% capacity retention of the pristine electrode. In prismatic full cell, the coated sample also kept 89.5% capacity retention at 25°C and 81.1% capacity retention at 55°C even after 300 cycles (2.75–4.35 V, 1C), showing better cycling stability than that of the pristine NCM. The ultrathin AlPO4 coating could not only keep the bulk structure stability from the surface degradation, but also diminishes the electrochemical resistance varies after cycles, thereby supporting the coated cathodes with enhanced electrochemical stability.

Construction nasicon-type NaTi2(PO4)3 nanoshell on the surface of P2-type Na0.67Co0.2Mn0.8O2 cathode for superior room/low-temperature sodium storage

P2-type manganese-based layered oxides are considered as promising cathode materials for sodium-ion batteries (SIBs). However, most of them suffer from sluggish kinetics and unfavorable structural stability, severely impeding their practical applications. Herein, Nasicon-type NaTi2(PO4)3 (NTP) nanoshell is coated on the surface of P2-type Na0.67Co0.2Mn0.8O2 (NCM) to boost its performance as a novel cathode for SIBs. The as-prepared NCM@NTP7 exhibits smooth electrochemical charge/discharge profiles, with a specific capacity of 70.7 mAh/g at 20C, and 86.7% capacity retained at 0.5C after 150 cycles at room temperature. Impressively, the bulk structure can be stabilized via the absolute solid-solution reaction at low temperature (-20℃), which shows 120.9 mAh/g discharge capacity at 0.2C with 92.3% retention and fast Na+ transport kinetic, wherein the D value is 16 times as large as that of pristine NCM. Our study provides a simple and efficient strategy to design and optimize promising layer-structural cathodes for SIBs.

Improving Electrochemical Performance and Structural Stability of LiNi0.6Co0.2Mn0.2O2 via Nanoscale Coating with LiTiO2

LiNi0.6Co0.2Mn0.2O2 (NCM622) has been coated with rock-salt-type LiTiO2 by ball milling and tempering to improve its electrochemical properties and structural stability. The rock-salt-type LiTiO2 was synthesized by a solvothermal method using tetrabutyl titanate as raw material. The optimal molar ratio of LiTiO2 to NCM was identified as 0.5 mol.%, and the thickness of the cladding layer was observed to be approximately 5 nm to 14 nm by high-resolution transmission electron microscopy. Compared with pristine NCM, modified samples exhibited higher capacity of 20 mAh g−1 after 200 cycles under 1C at 2.7 V to 4.3 V, corresponding to capacity retention of 88.03%, while that of pristine NCM was only 80.01%. The best LiTiO2-coated sample exhibited a superior rate capability at 5C (152.90 mAh g−1) compared with the BNCM sample (113.75 mAh g−1). The improvement in these properties occurs because the coating layer protects the NCM material from direct contact with the electrolyte, thereby reducing undesirable side reactions, which is helpful to extend the lifetime of lithium-ion batteries. These new discoveries are beneficial for the development of nickel-based cathode materials for lithium-ion batteries with stabilized structure.

Microwave-reduced graphene oxide wrapped NCM layered oxide as a cathode material for Li-ion batteries

Abstract Nanocrystalline Li(Ni1/3Co1/3Mn1/3)O2 (NCM layered oxide) was synthesized through the solution combustion route to use as the cathode material in the Li-ion battery. Reduced graphene oxide (RGO) was employed as the additive to improve electrochemical performance of the battery. Graphene oxide was reduced by microwave irradiation. The RGO was wrapped around the NCM when added in different weight fractions to fabricate nanocomposite mixtures for use as the cathode of the LIB. The initial charge//discharge capacities of NCM and NCM–5 wt.% RGO were measured at a rate of 0.05C in the voltage window of 2.5–4.3 V at room temperature and showed values 198.1//167.6 mAh/g and 209.2//186.6 mAh/g, respectively. The capacity retention of the optimum graphene-containing cathode during the cycling testing at different C rates increased to 99.6% as compared to that of pristine NCM cathode being 94.7%. Impedance spectroscopy studies revealed that graphene additive caused a decrease in the charge transfer resistance and an increase in the Li-ion diffusion coefficient.

Li2TiO3 and Li2ZrO3 co-modification LiNi0.8Co0.1Mn0.1O2 cathode material with improved high-voltage cycling performance for lithium-ion batteries

LiNi0.8Co0.1Mn0.1O2 (NCM) materials with surface modification by Li2TiO3 (LTO), Li2ZrO3 (LZO) and Li2TiO3-Li2ZrO3 (LTZO) coatings are successfully synthesized via a simple wet chemical method and proper heat-treatment process. The crystal structure, surface morphology, valence states and electrochemical properties of different modified NCM materials are investigated by the means of X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The NCM co-modified by Li2TiO3 and Li2ZrO3 composite coatings (LTZO@NCM) shows remarkable improvements in cycling performance and rate capability, the discharge capacity is 190.36 mAh g−1 with high capacity retention of 92.64% at 0.2C after 100 cycles between 2.75 and 4.4 V, compared to 174.83 mAh g−1 with the capacity retention of 87.20% for pristine NCM. Even at a high current density of 1 C, LTZO@NCM still maintains a high discharge capacity of 149.77 mAh g−1 cycled at high cut-off voltage of 4.4 V, with a capacity retention rate of 83.04% at 150th cycle, while bare NCM only delivers 123.92 mAh g−1 with capacity retention of 68.86%. The enhanced electrochemical performance can be ascribed to the modified effect of LTZO nano-coating layer on the NCM surface. LTZO nano-coating layer can not only effectively protect NCM particles, avoid the occurrence of side reaction, but also provide a better Li+ transport channels, improve lithium ion diffusion rate and enhance the structure stability and electrochemical performances of NCM material.

Study of LiNi0.6Co0.2Mn0.2O2 Coated with Li2ZrO3 Nanolayers in All-Solid-State Lithium Ion Batteries

The Li2ZrO3 nanolayer was coated over LiNi0.6Co0.2Mn0.2O2 cathode material (NCM) to produce all-solid-state lithium ion batteries and their enhanced electrochemical properties were determined. To relieve interfacial resistance resulting from insufficient contact, a Li2ZrO3 nanolayer is a suitable cathode coating agent because it can block corrosive species and decrease contact loss, along with elimination of the space-charge layer. All-solid-state cells using Li2ZrO3-coated NCM material showed higher capacity than pristine NCM. X-ray diffraction patterns showed the same peak separations and lattice parameters as pristine material. Scanning electron microscopy and transmission electron microscopy images obtained with electron dispersive spectroscopy mapping confirmed homogeneous coating with a uniformly thick Li2ZrO3 layer of around 5 nm. X-ray photoelectron spectroscopy revealed that the surface of NCM had two different O1s peaks, with a Zr–O peak, and Ni, Co, Mn, and Zr peaks. Electrochemical studies on pristine and Li2ZrO3-coated NCM materials were conducted using electrochemical impedance spectroscopy with galvanostatic cycle performances by constructing an all-solid-state cell. The impedance spectra showed relieved interfacial resistance with low polarization as coating agent was added. Notably, the 4 wt.% Li2ZrO3-coated NCM exhibited capacity retention of 81% at a current density of 0.12 mA/cm2 after 30 cycles, while that of the pristine cell hadunstable cycle performance and a low capacity retention of 69 percent. Thus, the Li2ZrO3-coated NCM material exhibited potential for all-solid-state batteries requiring high power or stable application.

High-Ni cathode material improved with Zr for stable cycling of Li-ion rechargeable batteries.

The Zr solvent solution method, which allows primary and secondary particles of LiNi0.90Co0.05Mn0.05O2 (NCM) to be uniformly doped with Zr and simultaneously to be coated with an Li2ZrO3 layer, is introduced in this paper. For Zr doped NCM, which is formed using the Zr solvent solution method (L-NCM), most of the pinholes inside the precursor disappear owing to the diffusion of the Zr dopant solution compared with Zr-doped NCM, which is formed using the dry solid mixing method from the (Ni0.90Co0.05Mn0.05)(OH)2 precursor and the Zr source (S-NCM), and Li2ZrO3 is formed at the pinhole sites. The mechanical strength of the powder is enhanced by the removal of the pinholes by the formation of Li2ZrO3 resulting from diffusion of the solvent during the mixing process, which provides protection from cracking. The coating layer functions as a protective layer during the washing process for removing the residual Li. The electrochemical performance is improved by the synergetic effects of suitable coatings and the enhanced structural stability. The capacity-retentions for 2032 coin cells are 86.08%, 92.12%, and 96.85% at the 50th cycle for pristine NCM, S-NCM, and L-NCM, respectively. The superiority of the liquid mixing method is demonstrated for 18 650 full cells. In the 300th cycle in the voltage range of 2.8–4.35 V, the capacity-retentions for S-NCM and L-NCM are 77.72% and 81.95%, respectively.

Enhanced rate performance and high current cycle stability of LiNi0.8Co0.1Mn0.1O2 by sodium doping

Sodium ions have been successfully doped into LiNi0.8Co0.1Mn0.1O2 (NCM811) by solid phase method. The influences of Na doping on the electrochemical properties of the electrode at high current intensities were studied. The experimental results show that 3% Na modified LiNi0.8Co0.1Mn0.1O2 has superior rate performance and cycling behavior due to the cation mixing is suppressed and the structural stability is enhanced by Na doping. The capacity retention of Li0.97Na0.03Ni0.8Co0.1Mn0.1O2 is 64.33% after 100th cycles at 10 C (1 C = 200 mA · g–1) in the potential range from 2.8 V to 4.3 V, which is greatly higher than the pristine NCM (only 35.01%). Li0.97Na0.03Ni0.8Co0.1Mn0.1O2 also shows excellent rate performance of 140.5 mAh · g–1 at 10 C, and the discharge capacity of 3% Na-NCM is higher than that of the pristine NCM when the current intensity is returned from 10 C to 0.5 C. The analysis of the cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) measurements confirm that the Na doping plays an important role in inhibiting the electrochemical polarization of LiNi0.8Co0.1Mn0.1O2 and improving the diffusion of lithium ions.

Facile and efficient fabrication of Li3PO4-coated Ni-rich cathode for high-performance lithium-ion battery

Owing to their low cost and high theoretical specific capacity, layered Ni-rich materials are extensively investigated as promising cathode materials for lithium-ion batteries. However, most Ni-rich materials do not exhibit superior cycle and rate capabilities at a high voltage or after exposure to air. In this study, Li3PO4-coated LiNi0.8Co0.1Mn0.1O2 (NCM@LPO) is developed using a simple one-pot sol–gel method by immersing NCM powder in a hydrophobic solution. Unlike the commonly used wet-coating method, the Li3PO4 coating layer is produced in situ on the NCM surface via precipitation reaction between polyphosphoric acid and residual Li compounds without additional re-heating. The Li-conductive Li3PO4 shield diminishes the electrode–electrolyte contact and suppresses the side reactions. Thus, the NCM@LPO sample shows a high capacity retention rate of 88.4% after 100 cycles at 1 C and an excellent capacity of 148.8 mAh g−1 at 10 C. Furthermore, the capacity retention rate of NCM@LPO sample is still as high as 84.6% after 100 cycles at 1 C after exposed in air for 7 days, which is much higher than that of the pristine NCM. The facile and efficient approach can be used to boost the cycle stability and inhibit the air sensitivity of other Ni-based cathode materials.

ALD derived Fe3+- doping toward high performance P2–Na0.75Ni0.2Co0.2Mn0.6O2 cathode material for sodium ion batteries

The structural instability and sluggish kinetic process of the pristine Na0.75Ni0.2Co0.2Mn0.6O2 (NCM) occurring at a high working voltage result in obvious capacity loss. In this study, Fe3+ doping onto the surface of the P2-type Na0.75Ni0.2Co0.2Mn0.6O2 (NCM) was fulfilled via post-annealing atomic layer deposition (ALD) derived Fe2O3 layer. It indicates that the modified NCM cathode materials exhibit better crystal structure stability and electrochemical behavior than the pristine NCM at wide voltage windows of 2.4–4.5 V and 2.4–4.7 V vs. Na/Na+. Furthermore, the ALD-30C-annealing material shows a higher initial capacity of 107 mA h g−1 at 0.1C (20 mA g−1), and it can reach a reversible capacity of 78 mA h g−1 and Coulombic efficiency of 96.6% after 100 cycles at the cutoff voltage of 4.5 V. Amazingly, combined with reduced graphene oxide (rGO) as an anode material, the ALD-30C-annealing cathode material exhibits notable full cell performance with the specific energy density of 160 Wh kg−1 at the high voltage widows of 2.4–4.5 V after 100 cycles. The designed strategy in this work may be one of the most promising perspectives toward the high performance cathode materials for SIBs.

Superior Stability Secured by a Four-Phase Cathode Electrolyte Interface on a Ni-Rich Cathode for Lithium Ion Batteries.

A multifunctional coating with high ionic and electronic conductivity is constructed on the surface of LiNi0.8Co0.1Mn0.1O2 (NCM) to boost the battery stability upon cycling and during storage as well. Phosphoric acid reacts with residual lithium species on the pristine NCM to form a Li3PO4 coating with extra carbon nanotubes (CNTs) penetrating through, which shows high ionic and electronic conductivity. NCM, Li3PO4, CNTs, and the electrolyte jointly form a four-phase cathode electrolyte interface, which plays a key role in the great enhancement of capacity retention, from 50.3% for pristine NCM to 84.8% for the modified one after 500 cycles at 0.5C at room temperature. The modified NCM also delivers superior electrochemical performances at a high cut-off voltage (4.5 V), high temperature (55 °C), and high rate (10C). Furthermore, it can deliver 154.2 mA h g-1 at the 500th cycle after exposed to air with high humidity for 2 weeks. These results demonstrate that the well-constructed multifunctional coating can remarkably enhance the chemical and electrochemical performances of NCM. The improved cycling, storage, and rate performance are attributed to the four-phase cathode electrolyte interface delivering high electron and ionic conductivity and securing the cathode against attack. This work broadens the horizon for constructing effective electrode/electrolyte interfaces for electrochemical energy storage and conversion.

Enhancement of the Electrochemical Performance of LiNi1/3Co1/3Mn1/3O2 Cathode Material by Double-Layer Coating with Graphene Oxide and SnO2 for Lithium-Ion Batteries

The graphene oxide-coated SnO2-Li1/3Co1/3Mn1/3O2 (GO-SnO2-NCM) cathode material was successfully synthesized via a facile wet chemical method. The pristine NCM and GO-SnO2-NCM were characterized by X-ray diffraction, scanning electron microscopy, energy-dispersive spectroscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy. The results showed that the double-coating layer did not destroy the NCM crystal structure, with multiple nano-SnO2 particles and GO uniformly covering the NCM surface. Electrochemical tests indicated that GO-SnO2-NCM exhibited excellent cycling performance, with 90.7% capacity retention at 1 C after 100 cycles, which was higher than 74.3% for the pristine NCM at the same cycle. The rate capability showed that the double-coating layer enhanced surface electronic–ionic transport. Electrochemical impedance spectroscopy results confirmed that the GO-SnO2-coating layer effectively suppressed the increased electrode polarization and charge transfer resistance during cycling.