Performance Of LiNi0 Research Articles

Li-Site Defects Induce Formation of Li-Rich Impurity Phases: Implications for Charge Distribution and Performance of LiNi0.5- xMxMn1.5O4 Cathodes (M = Fe and Mg; x = 0.05-0.2).

An understanding of the structural properties that allow for optimal cathode performance, and their origin, is necessary for devising advanced cathode design strategies and accelerating the commercialization of next-generation cathodes. High-voltage, Fe- and Mg-substituted LiNi0.5Mn1.5O4 cathodes offer a low-cost, cobalt-free, yet energy-dense alternative to commercial cathodes. In this work, the effect of substitution on several important structure properties is explored, including Ni/Mn ordering, charge distribution, and extrinsic defects. In the cation-disordered samples studied, a correlation is observed between increased Fe/Mg substitution, Li-site defects, and Li-rich impurity phase formation-the concentrations of which are greater for Mg-substituted samples. This is attributed to the lower formation energy of MgLi defects when compared to FeLi defects. Li-site defect-induced impurity phases consequently alter the charge distribution of the system, resulting in increased [Mn3+] with Fe/Mg substitution. In addition to impurity phases, other charge compensators are also investigated to explain the origin of Mn3+ (extrinsic defects, [Ni3+], oxygen vacancies and intrinsic off-stoichiometry), although their effects are found to be negligible.

Effect of process conditions on the performance of LiNi0.815Co0.15Al0.035O2 positive electrode material powder synthesized by hydrothermal approach

LiNi0.815Co0.15Al0.035O2 (NCA) lithium-ion battery cathode material was prepared using a hydrothermal approach. XRD and SEM analyzed the crystal parameters and powder morphology of the cathode material. The results show that the nickel cobalt precursor exhibits a petal-like morphology, and the nanoneedle primary particles are randomly distributed. Accompanied by the increase in calcination temperature and time, the peak intensity ratio of I003/I104 tends to decrease and then increase. The peak intensity ratio reached a maximum when the NCA sample calcined at 750°C for 8 h, indicating the lowest extent of Li/Ni mixing and the best electrochemical performance of the positive electrode material.

Significance of electrolyte additive molecule structure in stabilizing interphase in LiNi0.8Co0.1Mn0.1O2/artificial graphite pouch cells at high temperature

Electrolyte additives are pivotal for stable cycling of rechargeable lithium ion batteries (LIBs), which dictate the creation of the protective interphases on electrodes. Many additives have been proposed but less knowledge is available on the relationship between their molecular structure and interphase stability. This research compares three electrolyte additives with systematic changes in their cyclic ethylene sulfate structures, i.e. 1,3,2−dioxathiolane−2,2−dioxide (DTD), 4−methyl−1,3,2−dioxathiolane−2,2− dioxide (MDTD) and 4−propyl−[1,3,2] dioxathiolane−2,2−dioxide (PDTD) to investigate their effects on the performance of LiNi0.8Co0.1Mn0.1O2/artificial graphite lithium ion pouch cells at high temperature. Comprehensive characterizations reveal that all these additives exhibit similar oxidative and reductive activity, but they lead to diverse long−term cycling performance at 55 °C. The sulfate species derived from the propyl functionalized PDTD form the most effective cathode and anode interphases in preventing electrolyte decomposition and improving cycling capabilities, with capacity retention of 85 % after 900 cycles at 55 °C. Meanwhile, a super stable (3000 cycles), high−capacity (1668 mAh) pouch cell is constructed at 25 °C. This work paves a road to design electrolyte additive more efficiently for high−energy−density LIBs at elevated temperature.

Effects of Cathode Loadings on the Performance of the LiNi0.8Mn0.1Co0.1O2 Cathode in Lithium Batteries

LiNixMnyCozO2 (NMCs, x + y + z = 1) represent one promising cathode material for next-generation lithium-ion batteries (LIBs) and beyond, due to their high specific capacity and low cost.1-3 The current commercialized batteries tend to utilize high loadings of cathode materials and thin Li anodes for producing higher energy densities. However, a systematic study on the effects of cathode loadings is missing. To this end, we recently conducted a comparative study on the effects of different cathode loadings on the performance of LiNi0.8Mn0.1Co0.1O2 (NMC811). The NMC811 loading ranges from 2 – 14 mg/cm2. The resultant Li||NMC811 cells were tested for their capacity retention and sustainable capacity at different C-rates. Our study revealed that the cathode loadings have remarkably affected the cell performance. With increasing NMC811 loadings, the cells are more liable to fade in their capacity, due to a faster growth of solid electrolyte interface (SEI) on NMC811 particles and thereby a more sluggish Li-ion transportation. We also noticed that the Li anode side had remarkable effects on the Li||NMC811 cells. Particularly, we demonstrated that a polymeric surface coating via molecular layer deposition could protect the Li anode from degradation and thereby sustain Li||NMC811 cells for a better performance. Therefore, we concluded that the performance of the Li||NMC811 cells suffers from the issues of both the NMC811cathode and Li anode. It is significant to address their issues simultaneously for high performance.

Effect of pre-lithiation amounts on the performance of LiNi0.8Co0.1Mn0.1O2||SiOx/Graphite pouch cell

Pre-lithiation technology is essential to improve the initial coulombic efficiency (ICE) and cycling stability of high SiOx content cells. Different amounts of pre-lithiation significantly affect the electrochemical performance of cells. In this study, three groups of LiNi0.8Co0.1Mn0.1O2 || SiOx/Graphite pouch cells (SiOx, 45 wt%) with different pre-lithiation amounts are fabricated using an electrochemical pre-lithium method. The effects of pre-lithiation amounts on the capacity and cycling stability are comprehensively investigated by non-destructive tests and post-mortem analysis. The results show that increasing the amounts of pre-lithiation can substantially improve the capacity of the cells, but may also accelerate their aging. Further studies reveal that the cycling stability of SiOx/Graphite anode is strongly affected by the amounts of pre-lithiation, whereas the effect on the cathode is negligible. Moreover, titration gas chromatography (TGC) experiments are used to quantify the lithium loss in SiOx/Graphite anode. The accelerated formation of SEI and trapped lithiated active materials as well as lithium dendrites caused by over-lithiation at SiOx/Graphite anode are responsible for the rapid degradation of pouch cells with high pre-lithiation amounts. This work demonstrates the complex relationship between pre-lithiation amounts and electrochemical performance, which needs to be carefully measured in SiOx-based cells.

Enhanced cyclic performance of O2-type Mn-based layered oxide via Al doping for lithium-ion battery

The layered lithium nickel manganese oxide Li y Ni x Mn 1−x O 2 cathode materials with O2 structure exhibit good cyclic stability owing to their special arrangement of oxygen layers. However, the O2-type oxides generally present limited discharge capacity because of Li + ions defects in the lithium layer (as in Li y Ni x Mn 1−x O 2 , y < 1). Herein, an O2-type layered lithium nickel manganese oxide LiNi 0.33 Mn 0.65 Al 0.02 O 2 with high capacity and good capacity retention is obtained by introducing lithium and aluminum into the transition metal layer. The results of structural characterization and performance tests show that the optimal amount of Li + and Al 3+ in the transition metal layer effectively inhibits the disordered migration of transition metal ions and increases the electrochemical stability. The LiNi 0.33 Mn 0.65 Al 0.02 O 2 cathode delivers an initial discharge capacity of 153 mAh g −1 and the capacity only attenuates 13% after 100 cycles at the current density of 200 mA g −1 , which are higher than that of undoped oxide LiNi 0.33 Mn 0.67 O 2 . • O2-type Mn-based oxides with Li and Al in transition metal layer were synthesized. • Al doping amount has important effect on the performance of LiNi 0.33 Mn 0.67−x Al x O 2 . • LiNi 0.33 Mn 0.65 Al 0.02 O 2 has high stability and high initial capacity at 200 mA g −1 .

Effect of precursor structure transformation on synthesis and performance of LiNi0.5Co0.2Mn0.3O2 cathode material

The precursor has great influences on electrochemical performance of LiNi1-x-yCoxMnyO2 cathode materials. However, the effect of precursor structure transformation on the synthesis and electrochemical performance of LiNi1-x-yCoxMnyO2 is rarely mentioned. In this paper, Ni0.5Co0.2Mn0.3(OH)2 and different-temperature-preheated Ni0.5Co0.2Mn0.3(OH)2 were synthesized to prepare LiNi0.5Co0.2Mn0.3O2. The results show that Ni0.5Co0.2Mn0.3(OH)2 precursor transform into spinel-type solid solution (Ni0.5Co0.2Mn0.3)3O4 after preheating, and the contents of Ni3+, Co3+ and Mn4+ increase significantly. Comparative analyses reveal that the precursor structure change has no obvious effects on the crystal structure and surface morphology of the prepared LiNi0.5Co0.2Mn0.3O2. But the preheated precursors can reduce the undesirable lithium loss due to lithium volatilization in the high-temperature sintering process, leading to excess lithium ions enter into transition metal ions layer. Lithium excess can affect the amount of Ni3+, lattice parameters and residual lithium compounds on the particle surface, which in turn lead to different electrochemical behaviors of the prepared LiNi0.5Co0.2Mn0.3O2.

Influence of sintering temperatures on microstructure and electrochemical performances of LiNi0.93Co0.04Al0.03O2 cathode for high energy lithium ion batteries

In this study, we present a method for synthesizing Ni-rich LiNi0.93Co0.04Al0.03O2 (NCA) with a high-energy cathode material by the solid-phase method. The sintering temperature plays a very important role in the electrochemical performance of the LiNi0.93Co0.04Al0.03O2 since it affects the crystallinity and structural stability. Therefore, various sintering temperatures (660 °C/690 °C/720 °C/750 °C/780 °C/810 °C) are studied to get optimum electrochemical performances. The electrochemical performance of LiNi0.93Co0.04Al0.03O2 sintered at 720 °C shows the highest discharge capacity of 217.48 mAh g−1 with excellent Coulombic efficiency of 87.84% at 0.1 C. Moreover, the LiNi0.93Co0.04Al0.03O2 sintered at 720 °C exhibits excellent rate-capability (181.1 mAh g−1 at 2.0 C) as well as superior cycle stability (95.4% after 80 cycles at 0.5 C). This is because optimized sintering temperature leads to good structural stability with low cation disorder and residual lithium content.

Methylboronic Acid Mida Ester (Adm) as an Effective Additive in Electrolyte to Improve Cathode Electrolyte Interlayer Performance of Lini0.8co0.15al0.05o2 Electrode

Methylboronic Acid Mida Ester (Adm) as an Effective Additive in Electrolyte to Improve Cathode Electrolyte Interlayer Performance of Lini0.8co0.15al0.05o2 Electrode

Modifying the Cathode–Electrolyte Interphase by Sulfone-Based Additive to Enhance the Electrochemical Performance of LiNi0.5Mn1.5O4

Modifying the Cathode–Electrolyte Interphase by Sulfone-Based Additive to Enhance the Electrochemical Performance of LiNi_0.5Mn_1.5O₄

Elevated Electrochemical Performance of LiNi0.1Mg0.1Co0.8O₂ and LiFePO₄ Cathodes with Tris(2,2,2-trifluoroethyl) Phosphite as an Efficient Electrolyte Additive.

The significant role of Tris(2,2,2-trifluoroethyl) phosphite (TTFP) as an efficient additive during cycling of the layered nanostructured LiNi0.1Mg0.1Co0.8O₂ and olivine LiFePO₄ cathode materials in EC/DMC and 1M LiPF6 electrolyte for Li-ion battery are extensively investigated in this work. The electrochemical characterization techniques such as cyclic voltammetry, galvanostatic charge/discharge, and electrochemical impedance spectroscopy show that TTFP improves cycling stability and reduces the irreversible capacity of LiNi0.1Mg0.1Co0.8O₂ and LiFePO₄ electrodes. Also, the presence of TTFP in electrolyte solution reduces the impedance in LiNi0.1Mg0.1Co0.8O₂ and LiFePO₄ cathode materials at room temperature. A family of Nyquist plots was obtained from LiNi0.1Mg0.1Co0.8O₂ and LiFePO₄ electrodes for various potentials during the course of charging. The addition of TTFP in the electrolyte reduces the surface impedance of lithiated LiNi0.1Mg0.1Co0.8O₂ and LiFePO₄ which can be attributed to the reaction of the additive on the electrode's surface. Also, the presence of the additive TTFP in LiNi0.1Mg0.1Co0.8O₂ and LiFePO₄ cell enhances the lithium diffusion rate and improves the electronic conductivity of the cathode material.

Analysis on the effect of external press force on the performance of LiNi0.8Co0.1Mn0.1O2/Graphite large pouch cells

In application, lithium-ion pouch-format cells undergo expansion during cycling. To ensure the structure integrity of battery pack, preload force and fixed space were performed during pack assembly. In this paper, the swelling force of LiNi0.8Co0.1Mn0.1O2(NCM811)/Graphite large pouch cells is investigated as a function of the different preload force, state of charge (SOC), cycle number and graphite electrode kinds. The swelling force shows a significant dependency on the state of charge, but not follow linear characteristics due to NCM811’s volume extraction at high SOC. The higher SOC, the higher swelling force. 1500–1700 N is increasing from 50% to 100% SOC under 3000 N preload force. Three cells with different electrode design were cycled 1000 times, and each design with different preload force (1000, 3000 and 5000 N). The cell with 3000 N preload force shows better capacity retention for all electrode cells, the capacity retention of three different electrode cell is 93.7%, 90.9% and 91.2%, respectively. The corresponding swelling force increase fast at initial 300 cycles due to multi-factors. After 300 cycles, the swelling force increasing shows linear characteristics. After 1000 cycles, the cell with natural graphite (NG) has much larger swelling force than the cell with artificial graphite (AG), 9030 vs. 6370 N under 3000 N preload force. The functional binder polyacrylic acid (PAA) with -COOH unit and mixed with carboxymethylcellulose sodium (CMC) can form cross-link net at the graphite surface, supplying higher adhesive strength and restraining the electrode expansion. The adhesive strength increased from 7.2 to 20 N/m, corresponding the anode thickness expansion ratio from 25% reduced to 15%. The swelling force reduced from 9030 N to 6930 N, near to the cell with AG+SBR design. Delta voltage (∆V) and average discharge voltage evolution during cycling were also investigated of the different electrode cells. From the study, it can be useful for mechanical design, battery management of module and pack which can be beneficial for long life, safety and reliability of electric vehicle (EV) products.

Tris(trimethylsilyl) phosphite (TMSPi) as an electrolyte additive for LiNi0.5Co0.2Mn0.3O2 cathode materials at elevated voltage and temperature

Electrolyte additive tris(trimethylsilyl) phosphite (TMSPi) was used to promote the electrochemical performances of LiNi[Formula: see text]Co[Formula: see text]Mn[Formula: see text]O2 (NCM523) at elevated voltage (4.5 V) and temperature (55[Formula: see text]C). The NCM523 in 2.0 wt.% TMSPi-added electrolyte exhibited a much higher capacity (166.8 mAh/g) than that in the baseline electrolyte (118.3 mAh/g) after 100 cycles under 4.5 V at 30[Formula: see text]C. Simultaneously, the NCM523 with 2.0 wt.% TMSPi showed superior rate capability compared to that without TMSPi. Besides, after 100 cycles at 55[Formula: see text]C under 4.5 V, the discharge capacity retention reached 87.4% for the cell with 2.0 wt.% TMSPi, however, only 24.4% of initial discharge capacity was left for the cell with the baseline electrolyte. A series of analyses (TEM, XPS and EIS) confirmed that TMSPi-derived solid electrolyte interphase (SEI) stabilized the electrode/electrolyte interface and hindered the increase of interface impedance, resulting in obviously enhanced electrochemical performances of NCM523 cathode materials under elevated voltage and/or temperature.

High-rate performance of LiNi0.5Mn1.45Al0.05O4 cathode material for lithium-ion batteries

High-rate performance of LiNi0.5Mn1.45Al0.05O4 cathode material for lithium-ion batteries

Comprehensive Insight into the Probability of Cyclotriphosphazene Derivatives as the Functional Electrolyte Additives in Lithium-Ion Batteries: Which Is Better and Why?

Enhancing the flame retardancy of electrolytes and the quality of interface films is of great significance to improve the safety performance of lithium-ion batteries (LIBs). In this work, the effects of (ethoxy)pentafluorocyclotriphosphazene (PFPN), hexafluorocyclotriphosphazene (FPPN), and pentafluoro(phenoxy)cyclotriphosphazene (HFPN) as flame-retardant additives in the functional electrolyte on the performances of LiNi0.6Mn0.2Co0.2O2 (NCM622)/graphite pouch cells are comprehensively investigated. It is indicated that the contents of PFPN, FPPN, and HFPN, respectively, reach 5, 8, and 8% to achieve the purpose of flame retardancy in the 1 M LiPF6/EC + EMC (EC/EMC = 1:2 in weight) system. When the cells without and with PFPN, FPPN, and HFPN additives are, respectively, charge–discharged in the voltage range of 3.0–4.4 V at 1C, their capacity retentions are 36.1, 60.7, 74.7, and 73.8% after 150 cycles. The interface analysis and theoretical calculation show that PFPN, FPPN, and HFPN can facilitate the formation of stable interface films on two electrodes and subsequently improve the battery performance. The addition of cyclotriphosphazene flame retardant in the electrolyte ultimately improves the safety of NCM622/graphite pouch cells without sacrificing electrochemical performance. The as-prepared additive-containing electrolyte exhibits promising prospects in the application, and the evaluation method is also useful to develop the functional electrolyte with flame retardant and film-forming properties.

Enhanced Electrochemical Performance of Nickel-Rich Cathode Materials by Surface Modification with Al2O3–ZrO2 for Lithium Ion Batteries

Al2O3–ZrO2 was coated on the surface of nickel-rich cathode materials by the sol–gel method to improve its electrochemical performance. The nanometer-thick Al2O3–ZrO2 coating layer refrains the side reaction between the electrolyte and the electrode, thus preventing the collapse of LiNi[Formula: see text]Co[Formula: see text]Mn[Formula: see text]O2 layered structure and protecting the stability of the material. The electrochemical test shows that LiNi[Formula: see text]Co[Formula: see text]Mn[Formula: see text]O2 coated with Al2O3–ZrO2 has good cycle and rate performance. Under the cut-off voltage of 2.8–4.5[Formula: see text]V, LiNi[Formula: see text]Co[Formula: see text]Mn[Formula: see text]O2 coated with Al2O3–ZrO2 delivered an initial capacity which was 166.7[Formula: see text]mAh[Formula: see text]g[Formula: see text]at 1C (200[Formula: see text]mAh[Formula: see text]g[Formula: see text] rate, and the capacity retention rate was 77.7% after 200 cycles. The pristine LiNi[Formula: see text]Co[Formula: see text]Mn[Formula: see text]O2 delivered an initial capacity which was 166.4[Formula: see text]mAh[Formula: see text]g[Formula: see text] at 1C rate, and the capacity retention rate was 51.7% after 200 cycles. The EIS and CV provided the enhanced electrochemical performance of LiNi[Formula: see text]Co[Formula: see text]Mn[Formula: see text]O2 coated with Al2O3–ZrO2 which was due to accelerating Li[Formula: see text] diffusion of nickel-rich materials and electrolytes.

The Sand equation and its enormous practical relevance for solid-state lithium metal batteries

In this work, different Li salt concentrations and ionic conductivities of poly(ethylene oxide)-based solid polymer electrolytes (PEO-based SPEs) are correlated with the performance of LiNi0.6Mn0.2Co0.2O2 (NMC622)||Li full cells. While the SPEs with different salt concentrations behave similarly in NMC622||Li cells at 60 °C, their influence on the specific capacities is significant at 40 °C. Below a distinct salt concentration, i.e. > 20:1 (EO:Li), a sudden blocking-type polarization appears, indicatable by an almost vertical voltage profile, both in full and in Li||Li symmetric cells. The corresponding time and current density for this polarization-type is shown to mathematically fit with the Sand equation, which subsequently allows calculation of DLi+. According this relation, lack of Li+ in the electrolyte close to the electrode surface can be concluded to be the origin of this polarization, but is shown to appear only for “kinetically limiting” conditions e.g. above a threshold current density, above a threshold SPE thickness and/or below a threshold salt concentration (ionic conductivity), i.e. at mass transfer limiting conditions. With the support of this relation, maximal applicable current densities and/or SPE thicknesses can be calculated and predicted for SPEs.

The effect of drying methods on the structure and performance of LiNi0.5Co0.2Mn0.3O2 cathode material for lithium-ion batteries

In this paper, we investigate the effect of drying methods (freeze drying method and vacuum drying method) assisting a solvothermal method on the morphology, structure and electrochemical properties of LiNi0.5Co0.2Mn0.3O2 cathode material (which are named FD-NCM and VD-NCM respectively) for lithium-ion batteries. X-ray diffraction (XRD) results demonstrated that FD-NCM exhibited a lower degree of cation mixing and a better layered hexagonal structure than VD-NCM. The FD-NCM sample presented a uniform and homogeneous surface morphology with a higher BET surface area (20.08 m2 g−1), as confirmed by scanning electron microscopy (SEM). In addition, the FD-NCM material exhibited better electrochemical performance than the VD-NCM material. Specifically, the discharge capacities of FD-NCM were 155.8, 153.5, 146.8, 141.1, 129.3, and 111.0 mAh g−1, corresponding to the rates of 0.1C, 0.2C, 0.5C, 1C, 2C and 5C, respectively, with the capacity retention maintained at 88.80% at 0.5 C after 50 cycles, which preceded that of the VD-NCM sample (82.46%). According to electrochemical impedance spectroscopy (EIS) analysis, the charge-transfer resistance (Rct) of FD-NCM material increased from 75.31 Ω to 80.42 Ω, much smaller than that of VD-NCM from 93.85 Ω to 119.60 Ω, which demonstrated that the uniform morphology plays an important role in cathode materials for lithium ion batteries.

Improving electrochemical performances of LiNi0.5Mn1.5O4 by Fe2O3 coating with Prussian blue as precursor

LiNi0.5Mn1.5O4 (LNMO) cathodes always suffer from severe capacity fading because of the oxidization of electrolyte and the dissolution of transition metal. Surface modification has been widely recognized as one of the most effective approaches. Herein, a uniform Fe2O3 layer was coated on LNMO via a simple solid-state method with Prussian blue as precursor. The SEM, TEM, XPS, and XRD results show that the Fe2O3 layer was effectively coated on the surface of LNMO. Fe2O3 layer not only increased the specific capacity of Li/LNMO@Fe2O3–0.65% (more than 120 mAh g−1, 2 C) but also improved the capacity retention (more than 90% after 300 cycles at 25 °C). While those of LNMO are about 94 mAh g−1 and 74%, respectively. These are owing to the successful suppression of side reactions and the dissolution of Mn and Ni. Therefore, this long-term cycling coated material is a promising candidate for high-energy lithium-ion batteries.

Study on Preparation and Performance of LiNi0.8Co0.1Mn0.1O2 as cathode materials for lithium ion batteries

Study on Preparation and Performance of LiNi0.8Co0.1Mn0.1O2 as cathode materials for lithium ion batteries