Lithium Residues Research Articles

In-situ grown Li-Ti-O layer derived by atomic layer deposition to improve the Li storage performance of Li2TiSiO5 anode materials

Li2TiSiO5 (LTSO) fibers coated by an in-situ grown Li-Ti-O layer are synthesized through ALD and post thermal treatment. Due to the ALD coating technique, precise thickness control and conformal coating layer can be realized. Through post-heating treatment, the ALD-coated TiOx layer can react with lithium residues in the host materials, forming the Li-Ti-O coating layer. Benefiting from the Li-ion conductive feature of the Li-Ti-O phase, Li-Ti-O coated LTSO fibers exhibit a high reversible capacity of 229 mA h g−1 at a current density of 0.5 A g−1 after 400 cycles in the potential range of 0.1–3 V (vs. Li+/Li). Even at a high current density of 5 A g−1, a reversible capacity of 154 mA h g−1 can be achieved. Electrochemical impedance spectra (EIS) demonstrate that the Li-Ti-O coated LTSO fibers have an apparent chemical Li-ion diffusion coefficient of 1.43 × 10−15 cm2 s−1 and decreased charge transfer resistance compared to that of pristine LTSO fibers, leading to faster Li-ion transfer kinetics and improved electrochemical performances.

Facile synthesis of Li2MoO4 coated LiNi1/3Co1/3Mn1/3O2 composite as a novel cathode for high-temperature lithium batteries

High-temperature lithium battery system operated between 150 and 300 °C is highly desirable to be applied in oil/gas and geothermal explorations. However, the development of cathode material for high-temperature lithium batteries is relatively sluggish. In this study, LiNi1/3Co1/3Mn1/3O2 (NCM) is coated with Li2MoO4 by a facile solid-state reaction between MoO3 and surface lithium residue and the resulting composite is applied in high-temperature lithium batteries as a novel cathode material. Such a strategy can not only remove lithium residue components, but also facilitate lithium-ion transport in NCM through the resulting Li2MoO4 coating layer. At 200 °C, the discharge capacity and rate capacity of Li2MoO4 coated NCM are dramatically improved compared to the pristine one. At 300 °C, the electrochemical performance of 4m-NCM is better than other samples, and each sample exhibits better electrochemical performances than it is at 200 °C due to the enhanced kinetics in high temperature.

Surface in-situ reconstruction of LiNi0.8Co0.1Mn0.1O2 cathode materials interacting with antimony compounds and the electrochemical performances

Interfacial stability is regarded as one of the greatest challenges in the commercialization of Ni-rich layered cathode materials for lithium battery. Surface modification can solve these issues to obtain superior electrochemical performances. Herein, LiNi0.8Co0.1Mn0.1O2 (NCM811) cathode surface is reconstructed by a simple solid-state method using antimony oxides as modified agents. The modified mechanisms study show that the antimony oxides (Sb2O5) can react with the surface lithium residues effectively and partial surface lattice lithium on the NCM811 surface to further construct the LiSbO3/Li–Sb–Me–O (Me = Ni, Co, Mn) mixed coating layers. The uniform coating layer is mainly ascribed to the droplet spreading behaviors of the low smelting antimony oxides. The electrochemical measurements show that the Sb-modified NCM811 electrodes deliver 90.27% (180 mA g−1) and 96.07% (1440 mA g−1) capacity retentions over 3.0–4.3 V after 200 cycles, respectively, which are higher than 77.40 and 74.75% of the bare NCM811. The enhanced electrochemical performances are mainly benefitted to the enhanced the lithium transportation, the suppressed impedances increase and the more stable crystal structure.

Enhanced electrochemical performance of LiNi0.8Co0.15Al0.05O2 cathode by reducing lithium residue with low-temperature fluorination treatment

LiNi0.8Co0.15Al0.05O2 is considered as a representative layer-structured cathode material. Decreasing residual lithium (LiOH and Li2CO3) on its surface is the main challenge to improve cycling performance for commercial application. In this study, a dry and low-temperature fluorination (350 °C) method was proposed to modify LiNi0.8Co0.15Al0.05O2 cathode. The effects of fluorine content on the microstructure, surface composition and electrochemical properties of the cathode were extensively studied. The results showed that fluorination had multi-functions: (i) decreasing the lithium residues and generating amorphous LiF coating layer on the particle surface, (ii) restraining the diffusion of metal ions conveyed in the electrolyte, particularly at high temperature, (iii) retarding the increase of charge transfer impedance, and (iv) maintaining the structural stability of electrode during extended cycles. Electrochemical test results indicated that the sample fluorinated with 1.0 mol% F exhibited excellent cycling performance with the capacity retention of 93.9% after 100 cycles at 1 C, showing dramatical improvement compared with that of the pristine cathode (86.2%). This designed low-temperature dry fluorination process is expected to be practically applicable in other nickel-rich cathodes.

Dual functions of residue Li-reactive coating with C4H6CoO4 on high-performance LiNiO2 cathode material

Involving more nickel proportion in Ni-rich cathodes, edging to LiNiO2, is an inevitable trend to satisfy the demand of high energy density in lithium-ion batteries, but an inducement for the severer formation of undesirable lithium residues. To overcome the consequent degradation behaviors, a LiCoO2@Co3O4 complex coating layer is successfully realized on the surface of LiNiO2 via a facile wet-chemical method taking advantage of the Li-reactive ability of Co3O4. As a result, the 0.4 wt.% Co modified material exhibits competitively enhanced cyclic performance with 178.1 mAh g−1 after 50 cycles at 1 C, 11% higher than the pristine one in retention rate. Even at higher rates and temperature, it shows better electrochemical stability as well. The superior electrochemical properties of LiCoO2@Co3O4 coated LiNiO2 is ascribed to the dual-function of the coating method, where Co3O4 is formed during heat treatment and simultaneously reacted with surface lithium residues to generate LiCoO2. In combination of bulk and surface characterization, the significant effects of the coating layer on stabilizing material interface and strengthening the kinetic characteristics for LiNiO2 cathode materials are investigated and elucidated in detail.

Enhanced Electrochemical Performance of LiNi0.8Co0.15Al0.05O2 Cathode Material via Li2TiO3 Nanoparticles Coating

A Li2TiO3 modified LiNi0.8Co0.15Al0.05O2 cathode material is prepared by a novel coating method of Li2TiO3 nanoparticles. Compared with a coated material prepared by synchronous lithiation, this coated material shows an unchanged LiNi0.8Co0.15Al0.05O2 bulk structure and a dramatically reduced lithium residue amount on the surface. As a result, the electrochemical performance of this coated material is improved markedly, especially for the cycling stability at an elevated temperature (60°C), at which the capacity retention after 200 cycles at a rate of 1 C is 91.32%. The performance enhancement for this coated material can be mainly contributed to the less formation of a solid electrolyte interphase (SEI) layer and a lower degree of structural changes during cycling.

Improved electrochemical performances of LiNi0.6Co0.2Mn0.2O2 cathode material by reducing lithium residues with the coating of Prussian blue

Reducing the lithium residues on the surface of LiNi0.6Co0.2Mn0.2O2 (NCM) cathode is one of the most main challenges in Li-ion battery research. To address this task, a surface coating of Prussian blue (PB) of metal-organic framework is applied to NCM cathode to solve this intractable problem via a simple dry-coating method. The transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) results show that the uniform smooth coating can provide a protective shell to block H2O and CO2 absorption from the air, suppressing lithium residues formed on the surface. The color change experiment between PB and Li residuals illustrates PB can react directly with surface residual lithium species. As a result, the amount of residual lithium, such as LiOH and Li2CO3, is significantly reduced. The 0.5 wt% PB-modified NCM delivers a high discharge capacity retention of 81% after 500 cycles at 1 C discharge rate and exhibits a superior storage property after storing in air for 14 days. Furthermore, electrochemical impedance spectroscopy (EIS) confirms that the PB-NCM could hinder the impedance increase during cycling. These results clearly indicate that the PB coating layer contributes to the reduction of lithium residues and the creation of thinner cathode-electrolyte interface, improving structural stability and cycling performance of NCM.

In Situ Observation of Lithium Dendrite of Different Graphite Electrodes

Lithium-ion batteries (LIBs) have some serious safety problems, such as lithium dendrite formation during charging/discharging cycles that may cause internal short-circuiting, fires, and even explosions. A new double-scale in situ experimental setup, which can record all phenomena during the electrochemical testing, was developed. Lithium dendrite growth behavior of commercial LIBs during small-current-density charging at room temperature was observed in situ. The formation, growth, and dissolution of lithium dendrites, and dead lithium residue were all observed and recorded using this new experimental test system. A detailed model of lithium electrodeposition and dissolution processes was proposed.

High-voltage electrochemical performance of LiNi0.5Co0.2Mn0.3O2 cathode material via the synergetic modification of the Zr/Ti elements

The stabilities of the host and interfacial structure for layered LiNixCoyMn1-x-yO2 cathode materials are critical for their electrochemical properties, especially at high voltage. This study reports the synergetic effect of the Zr and Ti elements on the LiNi0.5Co0.2Mn0.3O2 cathode material (NCM523). The as-obtained Zr/Ti modified LiNi0.5Co0.2Mn0.3O2 cathode material shows the excellent electrochemical performance at high voltage. It delivers 167.3 mAh·g−1 at 1 C over 3.0–4.4 V corresponding 94.20% capacity retention after 200 cycles. Moreover, the rate capability of Zr/Ti co-modified NCM523 at 16 C (3.0–4.4 V) rises to 139.4 mAh·g−1 and corresponding capacity retention (vs. 0.5 C) is 79.57%. In addition, its capacity retention reaches to 91.71% after 100 cycles at 1 C rate even at 3.0–4.6 V. Such superior electrochemical performances are ascribed to the Zr doping and Ti modification. The synergetic modifications of the Zr/Ti elements not only stabilize the crystal structure, but also absorb the lithium residues to form mixed Li4Ti5O12/Li2TiO3 coating layers, which strengthen the stability of the interfacial structure and the kinetic characteristics of the cathode materials.

Enhanced electrochemical performance of LiNi0.8Co0.1Mn0.1O2 cathode materials via Li4P2O7 surface modification for Li-ion batteries

The performance of LiNi0.8Co0.1Mn0.1O2 cathode materials has been significantly improved by Li4P2O7 surface modification. Some electrochemical tests are carried out to investigate the relevant performances of LiH2PO4-coated LiNi0.8Co0.1Mn0.1O2, such as inductively coupled plasma test (ICP), scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). The results indicate that LiNi0.8Co0.1Mn0.1O2 is clad with a layer of average thickness about 30–40 nm. And the alkalinity on the surface of the modified materials has declined dramatically after titration measurement. The effect of surface modification can be credited to the two main factors: On the one hand, the weak acidity of LiH2PO4 neutralizes the lithium residues (LiOH/Li2CO3) on the surface of LiNi0.8Co0.1Mn0.1O2 cathode materials; on the other hand, LiH2PO4 continues to decompose and react with the unneutralized lithium residues to generate a coating layer of Li4P2O7 during the annealing process, which can prevent the active materials from contacting with the electrolyte directly and act as an outstanding Li+ conductor, thus inhibiting the interface reaction and improving the cycle performance as well as the rate properties of the host materials.

Improving the electrochemical performance of Li-rich Li1.2Ni0.2Mn0.6O2 by using Ni-Mn oxide surface modification

The surface lithium residues on Li-rich layered cathode materials xLi2MnO3·(1-x)LiMO2 (M = Mn, Co, Ni, etc.) are harmful to their electrochemical properties. In this work, the surface lithium residues of Li-rich Li1.2Ni0.2Mn0.6O2 (LNMO) are identified as Li2CO3 and LiOH by Fourier transform IR for the first time. To overcome this issue, Ni/Mn acetates are used to react with the surface lithium residues to form a LiNi0.5Mn1.5O4 spinel coating layer on LNMO particles. Compared with the bare LNMO sample, the 1 wt% LiNi0.5Mn1.5O4 coated LNMO shows improved long-term cycling stability and rate capability both at room temperature and 55°C. The coated one delivers an initial discharge capacity of 236 mAh g−1 with 99.6% capacity retention after 100 cycles at 0.5 C, while it is only 230 mAh g−1 with 91% capacity retention for the bare LNMO. After the surface modification, the rate capacity increases from 155 mAh g−1 to 180 mAh g−1 at 5 C at room temperature while the energy efficiency is improved from 78% to 85%.

In Situ Observation of Lithium Dendrite of Different Graphite Electrodes

Lithium-ion batteries (LIBs) have some serious safety problems, such as lithium dendrite formation during charging/discharging cycles that may cause internal short-circuiting, fires, and even explosions. A new double-scale in situ experimental setup, which can record all phenomena during the electrochemical testing, was developed. Lithium dendrite growth behavior of commercial LIBs during small-current-density charging at room temperature was observed in situ. The formation, growth, and dissolution of lithium dendrites, and dead lithium residue were all observed and recorded using this new experimental test system. A detailed model of lithium electrodeposition and dissolution processes was proposed. The electrode structures were determined by X-ray diffraction (XRD). The surface morphologies were examined by scanning electron microscopy (SEM). The texture and surface morphology of the graphite active layer affected lithium dendrite initiation as well as its growth processes.

Enhancing Electrochemical Performance of LiNi0.6Co0.2Mn0.2O2 by Lithium-ion Conductor Surface Modification

A novel surface modification strategy that could convert lithium residues on the Ni-rich material surface into a lithium ion conductor coating layer was investigated. Various analysis techniques, such as high resolution transmission electron microscopy (HRTEM), energy dispersive X-ray spectrometer (EDS) and X-ray photoelectron spectroscopy (XPS), were used to confirm the formation of an amorphous lithium lanthanum titanate (LLTO) coating layer with a thickness below 10nm. 1 mol% LLTO modified LiNi0.6Co0.2Mn0.2O2 exhibits the optimized electrochemical performance, with 87.2% capacity retention after 200 cycles at 0.5C, and excellent rate performance compared with that of the pristine LiNi0.6Co0.2Mn0.2O2. The cycling performance at higher charging voltage (4.5V) and storage characteristics against moisture and air are also improved significantly after LLTO modification. The enhanced electrochemical performance could be attributed to the high ionic conductivity of LLTO and the uniformity of the coating layer. It can not only suppress the interfacial resistance increasing, but also stabilize the crystal structure of the cathode material during charge-discharge cycling.

Alleviating Surface Degradation of Nickel-Rich Layered Oxide Cathode Material by Encapsulating with Nanoscale Li-Ions/Electrons Superionic Conductors Hybrid Membrane for Advanced Li-Ion Batteries.

Nickel-rich layered oxide cathode materials for advanced lithium-ion batteries have received much attention recently because of their high specific capacities and significant reduction of cost. However, these cathodes are facing a fundamental challenge of loss in performance as a result of surface lithium residue, side reactions with the electrolyte and structure rearrangement upon long-term cycling. Herein, by capturing the lithium residue on the surface of LiNi0.8Co0.1Mn0.1O2 (NCM) cathode material as Li source, we propose a hybrid coating strategy incorporating lithium ions conductor LixAlO2 with superconductor LixTi2O4 to overcome those obstinate issues. By taking full advantage of this unique hybrid nanomembrane coating architecture, both the lithium ion diffusion ability and electronic conductivity of LiNi0.8Co0.1Mn0.1O2 cathode material are improved, resulting in remarkably enhanced electrochemical performances during high voltage operation, including good cycle performance, high reversible capacity, and excellent rate capability. A high initial discharge capacity of 227 mAh g-1 at 4.4 V cutoff voltage with Coulombic efficiency of 87.3%, and reversible capacity of 200 mAh g-1 with 98% capacity retention after 100 cycles at a current density of 0.5 C can be attained. The improved electrochemical performance can be attributed to the synergetic contribution from the removal of lithium residues and the unique hybrid nanomembrane coating architecture. Most importantly, this surface modification technique could save some cost, simplify the technical procedure, and show great potential to optimize battery performance, apply in a large scale and extend to all nickel-rich cathode material.

Improving the electrochemical performance of Ni-rich cathode material LiNi0.815Co0.15Al0.035O2 by removing the lithium residues and forming Li3PO4 coating layer

Ni-rich cathode materials always suffer from surface lithium residues mainly caused by the reduction of Ni3+ to Ni2+ when exposing to moisture, and severe side reactions between organic electrolyte and highly active Ni4+ when fully charged. An appropriate amount of NH4H2PO4 is firstly coated on the hydroxide precursor Ni0.815Co0.15Al0.035(OH)2 before mixing with Li2CO3. The NH4H2PO4 can react with the lithium residues and form a uniform Li3PO4 coating layer. X-ray diffraction, scanning electron microscopy, field emission transmission electron microscopy and element mapping are employed to investigate the Li3PO4 coating layer. Electrochemical measurements results show that the cycle stability of the synthesized LiNi0.815Co0.15Al0.035O2 both at room temperature and 55 °C has been significantly improved. Its thermal stability has also been greatly enhanced.

Improved High Voltage Electrochemical Properties and Thermal Stability of LiNi0.6Co0.2Mn0.2 By Li3PO4 Surface Modification

LiCoO2 is the most commercialized in lithium ion batteries (LIBs) for portable electronics because of its high volumetric energy density compared to the other commercialized cathode materials. However, low specific capacity (145 mAh/g @ 4.3 V cut-off) hinders its application to emerging technologies, such as power tool and plug-in hybrid electric vehicles. As a result, layered Ni-rich LiNixCoyMn1 - x - yO2 materials have attracted much attention as promising alternative cathode materials because of their high capacity and relatively low cost. However, Ni-rich layered cathode materials suffer from structural instability by direct contact with electrolyte at high voltage (>4.3V), resulting in poor cyclability, rate capability and thermal instability. To solve these problems, a lot of researches have been carried out to coat the surface of layered cathode materials using oxide or phosphate, such as TiO2, Al2O3, and Li3PO4. Among these coating materials, Li3PO4 has attracted a great attention as coating material due to its high ionic conductivity and thermal stability due to strong P=O bonding. Recently, Zhao et al., reported on the Li3PO4 coating on LiFePO4 cathode material, but they used Li3PO4 nano particle as a coating material, resulting in non-uniform coating. Also, Xiong et el, tried to coat the Li3PO4 on LiNi0.8Co0.1Mn0.1O2 cathode material using the reaction between (NH4)2HPO4 and lithium residues, but the Li3PO4 coating layer is not confirmed. In this study, we report on the synthesis of Li3PO4-coated LiNi0.6Co0.2Mn0.2O2 using a citric acid assisted sol-gel method in which nm-thick Li3PO4 layer was uniformly coated on the LiNi0.6Co0.2Mn0.2O2. It exhibited improved cyclability at high voltage (4.7V) and rate capability than those of bare LiNi0.6Co0.2Mn0.2O2. In addition, Li3PO4-coated LiNi0.6Co0.2Mn0.2O2showed improved thermal stability at elevated temperature. More details on the synthetic procedure, electrochemical and physical properties will be presented at the meeting.

Multifunctional modification of Li[Ni0.5Co0.2Mn0.3]O2 with NH4VO3 as a high performance cathode material for lithium ion batteries

Li[Ni0.5Co0.2Mn0.3]O2 material was treated with NH4VO3 at 400 °C for 3 h Li3VO4 coating layer was formed during the calcination by using lithium residues on the material surface as raw materials. XRD results showed the NH4VO3 modified material had less Li+/Ni2+ cation mixing degree and confirmed some vanadium doped into the crystal lattice. Electrochemical studies indicated the modified material exhibited excellent lithium ion diffusion coefficient, superior cycle performance and improved rate capability compared with those of the bare material. The NH4VO3 modified sample maintains 156.7 mA h g−1 with 87.8% capacity retention after 100 high-voltage cycles (with 4.6 V charge cut-off) at 1 C. While, for the bare sample, the value is only 131.3 mA h g−1 with 75.5% capacity retention. The enhanced electrochemical performance can be ascribed to the removal of lithium residues, the doping of vanadium ion and the lithium ion conductive Li3VO4 coating layer. On the basis of these results, Li3VO4 coated Li[Ni0.5Co0.2Mn0.3]O2, prepared by the direct reaction with NH4VO3, can be used as a promising cathode material for Li-ion batteries.

Improved Electrochemical Performances and Thermal Stability of LiNi0.6Co0.2Mn0.2 by Li3PO4 coating

LiCoO2 is the most commercialized in lithium ion batteries (LIBs) for portable electronics because of its high volumetric energy density compared to the other commercialized cathode materials. However, low specific capacity (145 mAh/g @ 4.3 V cut-off) hinders its application to emerging technologies, such as power tool and plug-in hybrid electric vehicles. As a result, layered Ni-rich LiNixCoyMn1 - x - yO2 materials have attracted much attention as promising alternative cathode materials because of their high capacity and relatively low cost. However, Ni-rich layered cathode materials suffer from structural instability by direct contact with electrolyte at high voltage (>4.3V), resulting in poor cyclability, rate capability and thermal instability. To solve these problems, a lot of researches have been carried out to coat the surface of layered cathode materials using oxide or phosphate, such as TiO2, Al2O3, and Li3PO4. Among these coating materials, Li3PO4 has attracted a great attention as coating material due to its high ionic conductivity and thermal stability due to strong P=O bonding. Recently, Zhao et al., reported on the Li3PO4 coating on LiFePO4 cathode material, but they used Li3PO4 nano particle as a coating material, resulting in non-uniform coating. Also, Xiong et el, tried to coat the Li3PO4 on LiNi0.8Co0.1Mn0.1O2 cathode material using the reaction between (NH4)2HPO4 and lithium residues, but the Li3PO4 coating layer is not confirmed. In this study, we report on the synthesis of Li3PO4-coated LiNi0.6Co0.2Mn0.2O2 using a citric acid assisted sol-gel method in which nm-thick Li3PO4 layer was uniformly coated on the LiNi0.6Co0.2Mn0.2O2. It exhibited improved cyclability at high voltage (4.7V) and rate capability than those of bare LiNi0.6Co0.2Mn0.2O2. In addition, Li3PO4-coated LiNi0.6Co0.2Mn0.2O2 showed improved thermal stability at elevated temperature. More details on the synthetic procedure, electrochemical and physical properties will be presented at the meeting.

Characterization and electrochemical performance of lithium-active titanium dioxide inlaid LiNi0.5Co0.2Mn0.3O2 material prepared by lithium residue-assisted method

The lithium residues are consumed as raw materials to in-situ synthesize the LiTiO2-inlaid LiNi0.5Co0.2Mn0.3O2 composites. The effects of various LiTiO2 contents on the morphology, structure, and electrochemical properties of LiNi0.5Co0.2Mn0.3O2 materials are investigated in detail. Energy dispersive spectrometer mapping, high-resolution transmission electron microscopy and fast Fourier transform analysis confirm that the spherical particles of LiNi0.5Co0.2Mn0.3O2 are completely coated by crystalline LiTiO2 phase; X-ray diffraction, cross-section SEM and corresponding EDS results indicate that Ti ions are also doped into the bulk LiNi0.5Co0.2Mn0.3O2 with gradient distribution. Electrochemical tests show that the LiTiO2-inlaid samples exhibit excellent reversible capacity, enhanced cyclability, superior lithium diffusion coefficient and rate properties. Specially, the 3mol% LiTiO2 inlaid sample maintains 153.7mAhg−1 with 94.4% capacity retention after 100cycles between 2.7–4.4V at 1C, take 30% advantage than that of the pristine one (118.2mAhg−1). This improvement can be attributed to the removal of lithium residues and suitable LiTiO2 inlaying. The absence of lithium residue is helpful to retard the decomposition of LiPF6. While, suitable LiTiO2 inlaying can protect the bulk from directly contacting the electrolyte, buffer the volume change of core and shell during cycles, increase the surface electronic conductivity and offer a 3D path for Li+ diffusion from the bulk to interface.

A hydrolysis-hydrothermal route for the synthesis of ultrathin LiAlO2-inlaid LiNi0.5Co0.2Mn0.3O2 as a high-performance cathode material for lithium ion batteries

Lithium residues on the surface of LiNi0.5Co0.2Mn0.3O2 have been removed as raw materials to synthesize LiAlO2-inlaid LiNi0.5Co0.2Mn0.3O2 cathode materials in situ for lithium ion batteries.