Electrochemical Performance Of LiNi0 Research Articles

Stabilization of crystal and interfacial structure of Ni-rich cathode material by vanadium-doping

Stable structure and interface of nickel-rich metal oxides is crucial for practical application of next generation lithium-ion batteries with high energy density. Bulk doping is the promising strategy to improve the structural and interfacial stability of the materials. Herein, we report the impact of vanadium-doping on the structure and electrochemical performance of LiNi0.88Co0.09Al0.03O2 (NCA88). Vanadium doped in high oxidation state (+5) would lead to alteration of the crystal lattice and Li+/Ni2+ cation mixing. Those are the main factors determining the cycling and rate capability of the materials. With optimization of vanadium-doping, the preservation of the integrity of the secondary particles of the materials, the enhancement of the diffusion of Li+ ions, and alleviation of the side reactions of the electrolyte can be efficiently achieved. As a result, NCA88 doped with vanadium of 1.5 mol % can provide superior cycling stability with capacity retention of 84.3% after 250 cycles at 2C, and rate capability with capacity retention of 65.5% at 10C, as compared to the corresponding values of 58.6% and 55% for the pristine counterpart, respectively. The results might be helpful to the selection of dopants in the design of the nickel-rich materials.

The effect of dual-doping on the electrochemical performance of LiNi0.5Mn1.5O4 and its application in full‐cell lithium‐ion batteries

Dual improvement on electrochemical kinetics and lifespan of LiNi0.5Mn1.5O4 (LNMO) cathode material is of great significance for realizing high-power and durable lithium-ion batteries (LIBs). To achieve this goal, the Mg2+−Cr3+ co-doping LNMO microspheres were prepared via the coprecipitation route. FTIR, Raman spectra and magnetic susceptibility verify that both the Mg2+ and Cr3+ doping are beneficial for the formation of disordered Fd3m phase leading to the improvement of electronic conductivity and decrease in electrochemical polarization and the charge transfer resistance (Rct). Meanwhile, the doping also reduces the content of Mn3+ in LNMO which can diminish the dissolution of Mn3+ resulting in the enhancement of cycling life. As a result, the Mg2+−Cr3+ co-doping sample (MC-LNMO) exhibits an improved electrochemical performance (EP). A discharge capacity (DC) of 110.7 mAh/g at 10C can be obtained for MC-LNMO which is higher than that of pure LNMO (only 53 mAh/g) and after 200 cycles the capacity fade is only 4.6% at 25 °C. To further evaluate the MC-LNMO electrode for practical application, in this study, the full cells were also fabricated using the MC-LNMO as cathode and Li4Ti5O12 (LTO) as anode. In the combination, the full device exhibits high energy density (ED) and long cycle life due to the large difference in the working potential of LNMO (4.7 V) and LTO (1.55 V) and their excellent lifespan. These findings provide a simple and scalable method to boost the EP of LNMO, which can be used to fabricate high-quality LIBs.

Unraveling the crystallinity on battery performances of chlorine-rich argyrodite electrolytes

Chlorine-rich argyrodite Li 5.5 PS 4.5 Cl 1.5 presents great potential for the application of solid-state batteries (SSBs) due to the high ionic conductivity and relatively low cost. However, the effect of crystallinity for Li 5.5 PS 4.5 Cl 1.5 on the electrochemical performances of related solid-state batteries is unclear. Herein, the electrochemical performances of LiNi 0.8 Mn 0.1 Co 0.1 O 2 /SE/Li–In SSBs with crystalline and glass-ceramic Li 5.5 PS 4.5 Cl 1.5 ( c - and gc -LPSC) electrolytes are carefully investigated. Electrochemical tests show that SSBs using c -LPSC electrolytes deliver higher capacities and better rate performances than that of gc -LPSC electrolytes at different operating temperatures due to the higher Li-ion conductivity of the former. Moreover, the optimized solid-state battery delivers an initial discharge capacity of 120.2 mAhg -1 at 5C and maintains 64% of the capacity after 3500 cycles under room temperature. At an elevated temperature (60 °C), a much higher discharge capacity of 145.5 mAh g -1 is achieved and 80.8% of the capacity is sustained after 500 cycles. This work unravels the influence of the crystallinity of argyrodite electrolytes on the intrinsic properties, providing a guiding significance for the construction of high-performance solid-state batteries. • The influence of crystallinity of Li 5.5 PS 4.5 Cl 1.5 on battery performances is revealed. • Glass-ceramic Li 5.5 PS 4.5 Cl 1.5 affords superior electrochemical and mechanical stability . • Crystalline Li 5.5 PS 4.5 Cl 1.5 contributes to better capacity and rate performances. • Constructed SSB shows outstanding performance at −20 °C.

A Synergistic Effect of Na+ and Al3+ Dual Doping on Electrochemical Performance and Structural Stability of LiNi0.88Co0.08Mn0.04O2 Cathodes for Li-Ion Batteries.

The synergistic effect of Na+/Al3+ dual doping is investigated to improve the structural stability and electrochemical performance of LiNi0.88Co0.08Mn0.04O2 cathodes for Li-ion batteries. Rietveld refinement and density functional theory calculations confirm that Na+/Al3+ dual doping changes the lattice parameters of LiNi0.88Co0.08Mn0.04O2. The changes in the lattice parameters and degree of cation mixing can be alleviated by maintaining the thickness of the LiO6 slab because the energy of Al-O bonds is higher than that of transition metal (TM)-O bonds. Moreover, Na is an abundant and inexpensive metal, and unlike Al3+, Na+ can be doped into the Li slab. The ionic radius of Na+ (1.02 Å) is larger than that of Li+ (0.76 Å); therefore, when Na+ is inserted into Li sites, the Li slab expands, indicating that Na+ serves as a pillar ion for the Li diffusion pathway. Upon dual doping of the Li and TM sites of Ni-rich Ni0.88Co0.08Mn0.04O2 (NCM) with Na+ and Al3+, respectively, the lattice structure of the obtained NNCMA is more ideal than those of bare NCM and Li+- and Na+-doped NCM (NNCM and NCMA, respectively). This suggests that NNCMA with an ideal lattice structure presents several advantages, namely, excellent structural stability, a low degree of cation mixing, and favorable Li-ion diffusion. Consequently, the rate capability of NNCMA (83.67%, 3 C/0.2 C), which presents favorable Li-ion diffusion because of the expanded Li sites, is higher than those of bare NCM (78.68%), NNCM (81.15%), and NCMA (83.18%). The Rietveld refinement, differential capacity analysis, and galvanostatic intermittent titration technique results indicate that NNCMA exhibits low polarization, favorable Li-ion diffusion, and a low degree of cation mixing; moreover, its phase transition is hindered. Consequently, NNCMA demonstrates a higher capacity retention (84%) than bare NCM (79%), NNCM (82%), and NCMA (82%) after 50 cycles at 1 C. This study provides insight into the fabrication of Ni-rich NCMs with excellent electrochemical performance.

Effect of Moo3 Coating on the Electrochemical Performance of Lini0.8co0.1mn0.1o2 Cathode for High-Energy Lithium-Ion Batteries

Effect of Moo3 Coating on the Electrochemical Performance of Lini0.8co0.1mn0.1o2 Cathode for High-Energy Lithium-Ion Batteries

Influence of Sol-Gel Reaction Temperature on the Morphology and Electrochemical Performance of Lini0.5mn1.5o4 Cathode Materials for Li-Ion Batteries

Influence of Sol-Gel Reaction Temperature on the Morphology and Electrochemical Performance of Lini0.5mn1.5o4 Cathode Materials for Li-Ion Batteries

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.

From coating to doping: Effect of post-annealing temperature on the alumina coating of LiNi0.5Mn1.5O4 cathode material

Spinel LiNi0.5Mn1.5O4 is considered as one of the most promising cathode materials due to high working voltage and high energy density. However, the fast capacity degradation, mainly induced by the instability of electrode/electrolyte interface and bulk structure, heavily prevents its commercial application. To alleviate above two issues, LiNi0.5Mn1.5O4 material was first coated with Al(OH)3 via double hydrolysis reactions between NaAlO2 and AlCl3·6H2O, where the corrosion of LiNi0.5Mn1.5O4 material is avoided by controlling the feeding sequence, and the uniform coating of Al(OH)3 on particle surface is achieved by controlling the feeding rate. The Al(OH)3-coated LiNi0.5Mn1.5O4 material was post-annealed at different temperatures, and the effects of different post-annealing temperatures on the structure, morphology and electrochemical performance of LiNi0.5Mn1.5O4 material were systematically investigated. It is found that the LiNi0.5Mn1.5O4 material after post-annealing treatment at 600 ​°C exhibits the optimal rate and cycling performances, which can be mainly attributed to the synergistic effect of Al2O3 surface coating and doping. The uniform and thin Al2O3 coating layer can avoid the direct contact of electrode with electrolyte, capture corrosive HF and increase oxygen vacancy on particle surface, while Al3+ doping can eliminate LixNi1-xO impurity phase, reduce Mn3+ content, strengthen the spinel structure and make Li+ ions diffusion easier, thus leading to the simultaneous improvement of interfacial and structural stability of LiNi0.5Mn1.5O4 material.

Preparation of LiNi0.5Co0.2Mn0.3O2 by freeze-drying method

LiNi 0.5 Co 0.2 Mn 0.3 O 2 cathode materials have many advantages such as excellent safety performance and huge specific capacity. The advantages have attracted attention from industry and academia. At present, solid-phase method and co-precipitation method were widely used, but there were some drawbacks during the manufacturing process, occasioning the broke cycle performance. In this paper, the effects of freeze-drying method, solid-phase method, and co-precipitation method on the electrochemical performance of LiNi 0.5 Co 0.2 Mn 0.3 O 2 cathode materials were studied. Compared with the other samples, the LiNi 0.5 Co 0.2 Mn 0.3 O 2 cathode materials prepared via freeze-drying method exhibited the best electrochemical performance in the half-cell testing. After 100 cycles at 0.1 C, the discharge specific capacity was 151.89 mAh g −1 , which was 34.1 mAh g −1 higher than that of solid-phase method. The capacity retention rate was 84.17%. It also showed excellent electrochemical performance at 5 C. The first discharge specific capacity was 149.56 mAh g −1 and the capacity retention rate was 84.17%. The experimental results showed that freeze-drying method could effectively improve the electrochemical performance. LiNi0.5Co 0.2 Mn 0.3 O 2 cathode materials with the unique cubic-like structures were prepared by freeze-drying method. It is noted that electrochemical performance of the cathode material prepared via this method was significantly better than traditional method.

An integrated surface coating strategy to enhance the electrochemical performance of nickel-rich layered cathodes

High-nickel layered oxides, LiNixCoyMnzO2 (0.6 ≤ x < 1), are promising cathode materials for producing batteries with high energy density and working voltage, while their poor cycling performance severely limits their commercial applications. Herein, an integrated surface coating/doping strategy is developed to significantly improve the structural stability and electrochemical performance of LiNi0.88Co0.06Mn0.06O2. The titanium ions from a thin TiNb2O7 coating layer diffuse inward during the high-temperature sintering process and a uniform protective layer forms on the surface of the secondary particles of the material. This protective layer suppresses side reactions, and the Ti4+ doping increases the thickness of the lithium layer and reduces the lithium/nickel mixing, thereby enhancing the diffusion of lithium ions in bulk electrode. The capacity retention of modified material after 200 cycles at 1 C is greatly improved from 59.8% of the pristine material to 87.2%. First-principles calculations confirm the interaction affinity of the TiNb2O7 coating on the layered LiNi0.88Co0.06Mn0.06O2 with Ti ion migration in the interlayer region. Moreover, the enhanced oxygen release energy and electronic conductivity benefiting from Ti4+ doping promote the cycling stability of the integrated cathode. The surface engineering strategy proposed herein is generally effective for the electrochemical improvement of nickel-rich ternary cathode materials.

Investigation on the structure and electrochemical performance of LiNi0.8Co0.1Mn0.1O2 modified with Sn

Ni-rich layered cathode materials are promising cathode materials for lithium-ion batteries with high energy density. To reveal the influence of Sn-coating and doping on the structure and electrochemical performances of Ni-rich layered cathode materials, LiNi0.8Co0.1Mn0.1O2, LiNi0.8Co0.1Mn0.1O2@xLi2SnO3 and LiNi0.8−xCo0.1Mn0.1SnxO2 (x = 0.02 and 0.04) are designed and synthesized. The effect of lithium-tin-oxide coating and Sn-doping on the structural and electrochemical behavior of Ni-rich cathode material are compared and investigated. Compared with the bare LiNi0.8Co0.1Mn0.1O2 cathode material, both LiNi0.8Co0.1Mn0.1O2@xLi2SnO3 and Sn-doped LiNi0.8−xCo0.1Mn0.1SnxO2 (x = 0.02 and 0.04) samples exhibit better electrochemical performances. The capacity retention for Li2SnO3-coated and Sn-doped materials after 270 cycles at 0.5C can reach as high as 93.7 and 96.6%, respectively. Besides, improved rate capabilities and thermal stability are also obtained for Li2SnO3-coated and Sn-doped materials. The superior electrochemical performances and enhanced thermal stability of Li2SnO3 coated samples are mainly ascribed to the higher interfacial stability and those of Sn-doped materials may be mainly due to higher structural stability and lower polarization than those of the bare LiNi0.8Co0.1Mn0.1O2 cathode material. These results indicate that the introduction of Sn ions, especially Sn doping, may be an effective strategy to improve the performance of Ni-rich layered cathode materials.

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.

Understanding the Role of Various Dopant Metals (Sb, Sn, Ga, Ge, and V) in the Structural and Electrochemical Performances of LiNi0.5Co0.2Mn0.3O2

Ni-rich layered oxides have been widely applied commercially due to their high energy density and capacity. However, there are still some drawbacks of capacity fading, O2 release, and Li/Ni exchange. Cation doping has been proven to be one of the most promising strategies to improve the electrochemical performances of Ni-rich layered oxides. Herein, density functional theory (DFT) calculations have been performed to investigate the effects of doping various cations (Sb5+, Sn4+, Ga3+, Ge4+, and V5+) on the structural stability and electrochemical performances of LiNi0.5Co0.2Mn0.3O2 (NCM523). The theoretical results show that Sb, Sn, Ga, Ge, and V doping can reduce the oxidation state of Ni ions. Moreover, doping with these metals can inhibit O2 release and Li/Ni exchange, which improves the safety, capacity retention, and rate capacity. Furthermore, Ga and Ge doping can improve the stability of partially deintercalated states, suppress lattice distortion, and increase the intercalation voltage. In conclusion, Ga and Ge doping is an effective strategy to optimize the electrochemical performances of NCM523.

Influence of Calendering on the Electrochemical Performance of LiNi0.9Mn0.05Al0.05O2 Cathodes in Lithium-Ion Cells.

Electrode calendering is a necessary process used in industry to improve the volumetric capacity of lithium-ion batteries. However, calendering high-nickel cathodes leads to electrode particle pulverization, raising concerns of a reduced cycle life due to parasitic side reactions. We present here an investigation of the impact of calendering on the morphology and electrochemical performance of the cobalt-free layered oxide cathode LiNi0.9Mn0.05Al0.05O2 (NMA-90). We find that secondary particle pulverization and fusion simultaneously occur at sufficiently high pressures. The initial surface area of the cathode is shown to increase with the degree of calendering, despite the higher likelihood of secondary particle fusion. Long-term cycling of full coin cells assembled with the NMA-90 cathode and the graphite anode indicates that cells with higher degrees of cathode calendering exhibit lower capacity fade compared to uncalendered cathodes. Hybrid pulse-power tests demonstrate that the usable capacity range of cells with calendered cathodes far exceeds those with uncalendered cells after long-term cycling. The improved capacity retention and pulse-power performance are attributed to the enhanced mechanical properties of the electrode after calendering that prevents loss of the primary particle contact during long-term cycling. We find that calendering high-nickel NMA-90 to industrially relevant densities does not have a detrimental effect on capacity fade, marking an important step toward commercial adoption.

Improved preparation efficiency and electrochemical performance of LiNi0.8Co0.15Al0.05O2 cathode material by oxalic acid and freeze-drying

Improved preparation efficiency and electrochemical performance of LiNi0.8Co0.15Al0.05O2 cathode material by oxalic acid and freeze-drying

Effect of solution wash on the electrochemical performance of LiNi0.8Co0.1Mn0.1O2 cathode materials

Solution wash is a key procedure in the recycling of cathode materials for lithium-ion batteries. It is well-known that Ni-rich ternary cathode material LiNi0.8Co0.1Mn0.1O2 (NCM-811) is sensitive to water, triggering the Li+/H+ exchange and increasing the cation disorder, which ultimately leads to a large capacity loss during the battery cycling. In this study, we investigated the structural/surface chemical stability as well as the capacity loss for NCM-811 ternary cathodes after washing in five different environmentally friendly and commercially available solutions (i.e., ethanol, methanol, sodium chloride aqueous solution, sodium hydroxide aqueous solution, and deionized water). It is discovered that the capacity decay rate during cycling is closely related to the Li+ ion loss after solution wash, the more the Li+ ion loss, the quicker the capacity decay during cycling. Among all the solution-washed samples, ethanol-washed samples show minimal Li+ ion loss and the best capacity retention. Where the Li+ ion loss is only 2%, and the specific capacity after 200 cycles is 2.6 times higher as compared to the water-washed counterparts. This study paves the way towards the practical applications of ethanol in the commercial recycling of NCM-based cathodes.

An effective modification strategy enhancing the structure stability and electrochemical performance of LiNi0.5Co0.2Mn0.3O2 cathode material for lithium-ion batteries

LiNixCoyMn1−x-yO2 (NCM) (x ≥ 0.5) have received more and more attention due to high energy density, which have been widely utilized in the fields of mobile electronic equipment and new energy vehicles. Nevertheless, these materials suffer severe capacity attenuation and inferior rate performance, hindering their commercialization. In this work, we design an effective strategy: co-modification of Nb doping and LiBO2 coating (NB-NCM) to stabilize the internal structure, reduce cation mixing, alleviate external side reactions and improve electrochemical performance. Material characterizations and electrochemical measurements were operated to comprehensively value the effect of co-modification on the structure, topography and electrochemical properties of NCM materials. As a result, Nb is doped into the bulk of the material and the surface of particle is uniformly coated with LiBO2. In addition, for the NB-NCM electrode, the discharge capacity retained 90.90% at 0.5 C rate after 50 cycles, which proves that co-modification is an effective method to stabilize structure and enhance electrochemical performance.

Salt and Solvent effect on physicochemical properties and species organisation of Lithium fluorosulfonyl imide (FSI and TFSI) based electrolytes for Li-ion battery: Consequence on cyclability of LiNi0.8Co0.15Al0.05 (NCA) cathode

Herein we present a comparative study of the physicochemical and thermal properties of four electrolytes formulated with LiTFSI, LiFSI in binary (3EC/7EMC) and ternary (EC/PC/3DMC) mixture of solvents, as a function of salt concentration and temperature. By modeling the change on viscosity, ionic conductivity, with Arrhenius, Eyring and Jones-Dole-Kaminsky equations, we established the determinants parameters which influence the organization of solutions, in order to understand their consequences on electrochemical performances of LiNi0.8Co0.15Al0.05 (NCA) as cathode in Li-ion battery. Results shown that (3EC/7EMC + LiTFSI) present a double solvation sphere of Li+ and weak ionic association consequently it is poorly suited to the activation and cycling of NCA. While (EC/PC/3DMC + LiFSI) benefits from both a single sphere of solvation and strong ion-ion and ion-solvent interactions, making the polarization of the interfaces in this electrolyte suitable to the Li+ diffusion and to low interface resistances. These results demonstrate that the electrolyte properties such as viscosity, conductivity and thermal stability depend on several factors. Those related to species in solutions (solvents and salt ions), and those related to operating conditions such as temperature and concentration. All these parameters impact the ionic dissociation and solvation. This study shows the close-link between the organization of species in solutions, the physicochemical and thermal properties, and their impact on electrochemical performances in a Li-ion battery.

Electrochemical performances of LiNi0.83Co0.12Mn0.05O2 by dual doping of Mg and Ti

LiNi0.83Co0.12Mn0.05O2 (NCM83) is considered as a potential cathode material owing to its high energy density and low cost, yet the discharge capacity decays rapidly with the cycles. Dual doping of Mg and Ti is used to improve electrochemical stability. MgxTixMn1-2x(OH)2+x is uniformly coated on the surface of precursor particles by co-precipitation method, and MgxTixMn1-2x diffuses evenly during the sintering process. Mg and Ti successfully enter into the crystal lattice of NCM83. The cells are cycled in 2.8–4.5 V at 1C for 200 cycles. The specific capacity of NCM83 is 192.1 mAh g−1, and the capacity retention is 61.8% after 200 cycles. The cyclability can be significantly enhanced by dual doping of Mg and Ti, which can maintain 84.3% capacity under the same condition.