Electrochemical Performance Of LiFePO4 Cathode Research Articles

In-situ growth of LiFePO4 with interconnected pores supported on carbon nanotubes via tavorite-olivine phase transition

Lithium iron phosphate (LiFePO4) has gained significant attention as a promising cathode material for lithium-ion batteries due to its excellent stability and safety characteristics. However, its relatively low electrical conductivity restricts its practical application in high-power devices. In this study, we propose a novel approach to improve the electrochemical performance of LiFePO4 cathodes by introducing carbon nanotubes (CNT) through an in-situ growth process. Firstly, CNT serve as nucleation sites for the growth of FePO4, which subsequently attaches and grows in situ on CNT, resulting in the precipitation of CNT/FePO4. Subsequently, pre-lithiation is performed to synthesize CNT/LiFePO4OH, which ensures efficient mass transfer and uniform reaction achieved by wet chemical lithiation process. Eventually,The improved lattice perfection of CNT/LiFePO4 is obtained through the tavorite-olivine phase transition at a low crystallization temperature, allowing for more favorable ion diffusion pathways. Furthermore, in conjunction with the uniform incorporation of CNT to enhance the overall conductivity of the composite, the presence of intrinsically interwoven pores entwined amidst a bedrock of LFP nanoparticles is unveiled. These intricately connected pores function as conduits, promoting the seamless diffusion of electrolyte across the composite structure. This, in turn, augments the interfacial engagement between the cathode and electrolyte, propelling a surge in electrochemical reactivity and harnessing a heightened level of electrochemical efficacy, thereby amplifying the overall electrochemical performance and efficiency. Electrochemical tests demonstrate that the CNT/LiFePO4 cathodes exhibit significantly prominent rate capability with 143.0 mAh g-1 at a rate of 20C, and remarkable cycling stability with a retention rate of ∼97.0% under 1000 cycles at 1C. The in-situ growth of CNT/LiFePO4 offers a simple and scalable approach for the modification of LiFePO4 cathodes, enabling the practical utilization of this promising material in high-performance lithium-ion batteries.

The effect of sulfonated copolymer as a binder on the electrochemical performance of LiFePO4 cathode for lithium-ion batteries

In today's market, lithium-ion batteries are proving to be the most promising and effective rechargeable batteries. In the development of active materials with high energy density for batteries, the design of binders is a bottleneck technology, which produces an interconnected electrode structure. In this study, for developing lithium-ion batteries with high efficiency, the sulfonated copolymer was employed as an effective binder. In order to improve the performance of poly(vinylidene fluoride) (PVDF) as a binder for lithium-ion batteries (LIBs), sulfonated PVDF copolymer was prepared in this study using the atom transfer radical polymerization (ATRP) process. The influence of sulfonated PVDF binder on the electrochemical performances of LIBs was assessed using charge and discharge measurements, cycling performance up to 300 cycles, cycling voltammetry (CV), and electrochemical impedance spectroscopy (EIS) analysis. The investigation indicated decreased concentration polarization and improved lithiation and delithiation kinetics at high number of charge/discharge cycles for LiFePO4 electrodes with sulfonated PVDF binders. The discharge capacity after 300 cycles was 90 mAh g−1 with a capacity retention of 100% at 1C. As a result, the copolymer synthesized in this paper can be utilized to design next-generation polymer binders for high-efficiency LIBs.

Effect of argon sputtering pressure on the electrochemical performance of LiFePO4 cathode

The development of a novel small-scale electrical power source technology is essential in the design of microelectronic devices. In this sense, this study presents the optimization of the sputtering deposition parameters to grow a LiFePO4 cathode, a candidate material for the development of solid-state lithium batteries. Specifically, it was evaluated the effect of argon deposition pressure on the electrochemical properties of LiFePO4 cathode. By combining X-ray photoelectron spectroscopy with electrochemical characterization methods, it was revealed that argon deposition pressure modulated the degree of the re-sputtering effects. In addition, it was found that high argon deposition pressure leads to the growth of LiFePO4 films with oxygen and phosphor deficiency. The absence of these atoms caused the decrease in the LiFePO4 electrochemical activity. Conversely, deposition parameters based on low argon sputtering pressure significantly reduced the degree of the re-sputtering effects, which in turn favored the growth of stoichiometric LiFePO4 films with an enhanced electrochemical activity.

Improving the electrochemical performance of LiFePO4 cathode with novel water-soluble binders

To maintain the integrity of electrodes via conductive binders plays a critical role for Li-ion batteries. In this letter, polyaspartic acid (PASP) was synthesized and used as a novel water-soluble binder for an LiFePO4 (LFP) cathode. At a 1 C current density, this LiFePO4 cathode had a discharge specific capacity of 152 mAh g−1 and retained close to 100% of the initial specific capacity after 40 cycles. Furthermore, this LiFePO4 cathode also maintained a high specific capacity of 122 mAh g−1 at 5C rate. The results of electrochemical impedance spectroscopy and scanning electron microscopy indicated that the layer of PASP that was coated on the LFP electrode, which maintained the integrity of the conductive network and reduced the Li + diffusion path length of the LFP electrode. Based on these properties, PASP could be a prospective binder for LFP cathodes.

Facile synthesis of S-doped LiFePO4@N/S-doped carbon core–shell structured composites for lithium-ion batteries

Heteroatom-doped carbon can significantly improve the electrochemical performance of LiFePO4 cathodes, but it is limited by the complex preparation process and expensive dopants. A self-assembled S-doped LiFePO4@N/S-doped C core–shell structured composites were synthesized by a convenient solvothermal method are reported. The structure and the electrochemical performance of the composites were characterized. In the S-doped LiFePO4@N/S-doped C composites, the glucose-derived carbon microspheres were attached by LiFePO4/C particles to form secondary particles in the core–shell structure. The thioacetamide regulated the morphology of LiFePO4/C particles and provided N and S atoms to dope the composites. The S-doped LiFePO4@N/S-doped C composites delivered specific discharge capacities of 157.81 mAh g−1 at 0.1 C and 121.26 mAh g−1 at 5 C, and capacity retention of 99.88% after 100 charge/discharge cycles. The excellent electrochemical performance of the S-doped LiFePO4@N/S-doped C composites can be attributed to the synergism of thioacetamide and glucose.

Porous Activated Carbon Prepared from Highland Barley Straw by Phosphoric Acid Activation as a Conductive Agent for Improving Electrochemical Performance of LiFePO4 Cathodes

Porous Activated Carbon Prepared from Highland Barley Straw by Phosphoric Acid Activation as a Conductive Agent for Improving Electrochemical Performance of LiFePO4 Cathodes

Understanding the Influence of Nanocarbon Conducting Modes on the Rate Performance of Lifepo4 Cathode in Lithium Ion Batteries

We report on an efficient and practical conducting mode built up by ternary conductive additive for boosting the electrochemical performance of LiFePO4 cathode in lithium ion batteries. The influence on the conductivity, rate capability as well as the continuous conductive paths of the resulting electrode is investigated. Carbon nanotubes (CNTs) with long-range electronic conduction are ultimately homogeneously dispersed (mono-dispersed) in electrode slurry, which connect the short-range conductive regions together formed by graphene sheets. Importantly, CNTs could provide more open channels for electrons and ions transportation, compared with the blocking function of graphene sheets. Herein, it is found that low contents of graphene sheet are unable to build up continuous conductive networks thus causing degraded rate capability compared with higher contents of them. Low-content graphene regions are then bridged by mono-dispersed CNTs to construct a complete conductive network, enable the hybrids having both an improved electrically conductivity and an electrons/ions open channels. Furthermore, combining a small number of carbon black as supplementary conducive point, an efficient and practical conducting mode called plane-to-line-to-point is demonstrated. Such conducting mode can construct both short-range/long-range electronic conduction and open ions channels, while also having conductive points all over the uncovered area of LiFePO4 cathode.

Influence of organic additive on the electrochemical performance of LiFePO4 cathode in an aqueous electrolyte solution

The effect of the organic additive ethylene glycol (EtG) in 1 M Li2SO4 aqueous electrolyte on the electrochemical performance of the LiFePO4 cathode material in aqueous rechargeable batteries is investigated at various content (wt.%) of 0, 5, 10, 20, and 40 in this study. The suitable content of EtG is 5%, which greatly enhances the cycling stability (121 mAh g−1) and low surface resistance (75 Ohm) of the LiFePO4 electrode at 1 C rate after repeated charge and discharge cycling. Moreover, the EtG additive in the aqueous electrolyte solution forms a compact and uniform solid interface electrolyte (SEI) layer on the surface of LiFePO4 particles, suggesting fast lithium ion transport with low resistance compared to a sample without EtG additive. The SEI layer formed on the electrode surface is investigated using X-ray photoelectron spectroscopy. Furthermore, the SEI layer prevents the formation of side reaction components in aqueous electrolyte solutions. We can assume that the SEI layer, which has lower resistivity and high ionic conductivity, can play an important role in enhancing high specific capacities and has excellent rate capabilities.

A versatile nitrogen-doped carbon coating strategy to improve the electrochemical performance of LiFePO4 cathodes for lithium-ion batteries

To improve the structural stability and electrochemical performance of a LiFePO4 cathode, a nitrogen-doped carbon (N-C) coating strategy is exploited using a simple spray-drying method with dopamine as an N-C coating source. Transmission electron microscopy shows a uniform N-C coating layer on the surface of the LiFePO4 spheres. The introduction of the N-C layer can improve the electrical conductivity and structural stability of the electrode, which results in N-C@LiFePO4 spherical cathode materials with excellent electrochemical properties. The 5% N-C@LiFePO4 spherical composite delivers a specific discharge capacity of 156 mAh g−1, with a capacity retention rate of 86% after 150 cycles at 0.1C. More importantly, because the nitrogen-doped carbon coating can significantly improve the electrochemical performance of the electrode material through excellent electron conductivity, a remarkable rate performance can be achieved by virtue of the thin N-C coated layer, which is superior to that of uncoated LiFePO4. The results from electrochemical impedance spectroscopy further verify that 5% N-C@LiFePO4 has an excellent Li+ conductivity and low charge transfer resistance. This efficient and scalable strategy offers a facile approach to develop high performance LiFePO4-based cathode materials for large-scale lithium-ion storage systems.

Attachment of redox active molecules on the carbon additive and its effect on the cycling performance of LiFePO4 electrodes

The bis(1,10-phenanthroline)-5-amino-1,10-phenanthroline iron (II) complex (Fe2+[Phen]2[Phen-NH2]) was synthesized and characterized before covalent attachment to the surface of acetylene black carbon via diazonium chemistry. The metal complex was characterized by UV–visible spectroscopy and elemental analysis. Elemental analysis revealed a low grafting yield of approximately 3 wt%. Cycling voltammetry of modified-carbon electrode showed an apparent redox potential of 4.1 V (vs. Li) characteristic of the iron complex. The voltammetric charge associated to the redox peak corresponded to approximately 3.3 wt% of grafted groups, in agreement with the value estimated by elemental analysis. The electrochemical performance of LiFePO4 cathodes using modified and unmodified acetylene black carbons as conducting additive were compared through galvanostatic cycling and electrochemical impedance spectroscopy measurements. At a 5C rate, the electrode made with the modified carbon delivered a specific capacity of about 60 mAh.g−1 in comparison to only 25 mAh.g−1 for the composite with unmodified conductive additive. Charge/discharge cycling experiments over 200 cycles at C/2.5 revealed a capacity fade of about 0.2 and 0.14% per cycle for the LiFePO4 electrodes made with the unmodified and modified carbons, respectively. Furthermore, the charge-transfer resistance of LiFePO4 electrode using the grafted-carbon is significantly smaller (150 Ω) than the unmodified acetylene black (300 Ω).

Comparative study on the electrochemical performance of LiFePO4 cathodes fabricated by low temperature 3D printing, direct ink writing and conventional roller coating process

Electrodes for lithium-ion batteries can be fabricated in many ways including conventional roller coating and 3D printing. Roller coating is a standardized process in current lithium-ion battery industry, while 3D printing has been used to fabricate three-dimensional (3D) unconventional electrodes with tailored geometries. Our previous study proposed a low temperature 3D printing process to fabricate highly-porous LiFePO4 (LFP) electrodes. However, there still lack a study on the comparison of electrochemical performance of LFP electrodes fabricated via the three different fabrication processes including low temperature direct writing-based 3D printing (LTDW), room temperature direct ink writing (DIW) and roller coating process. In this study, we fabricated LFP cathodes using these three fabrication processes from LFP inks with different solid contents. By varying the solid content, LFP electrodes with different geometries (including width and thickness), morphologies and porous microstructures were obtained via LTDW and DIW. Mercury porosimetry was performed to examine the differences of the three types of LFP electrodes in porous microstructures. Electrochemical performance including charge/discharge, rate performance, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) of the three types of electrodes were measured and compared. Results showed that electrode fabrication processes have important effects on the electrochemical performance of LFP electrodes depending on the ink solid content. LTDW-fabricated electrodes had the best performance at high solid content (≥0.467 g/mL) and conventional roller coated electrodes performed better at low solid content (≤0.356 g/mL). Relationships between ink solid content, fabrication process, resulting porous microstructures and electrochemical performance were discussed. Finally, an optimal specific capacity of ∼82 mAh.g-1 @ 10C was achieved at a solid content of 0.467 g/mL by LTDW process.

A theoretical study of different carbon coatings effect on the depolarization effect and electrochemical performance of LiFePO4 cathode

In this work, three categories of advanced carbon materials coated on current collector are investigated. The results indicate that carbon coating has a positive influence on the depolarization effect and electrochemical performance of LiFePO4 cathode, different carbon coatings have drastically different influences, high rates in particular. The depolarization effect and rate performance show the following order: Graphene nanosheets (GNs)>Carbon nanotubes (CNTs)>Activated carbons (ACs), and the differences of rate capacities among them become more and more obvious with increasing rates. Especially for 5C, the discharge capacities values are 122mAhg−1, 114.8mAhg−1, 106.8mAhg−1 and 49.2mAhg−1 for LFP-GNs-Al, LFP-CNTs-Al, LFP-ACs-Al and LFP-Al, respectively. The enhancement is attributed to the carbon coating acting as a transport system of electron between cathode materials and current collector, resulting in reducing the contact impedance within the electrodes, thus providing a favorable balance between fast ion diffusion and increased electron transport.

Improvement of the electrochemical performance of LiFePO4 cathode by Y-doping

Abstract

Enhanced electrochemical performance of LiFePO4 cathode with synergistic modification of Na3V2(PO4)3 and carbon network

A high performance 9LiFePO4–Na3V2(PO4)3/C composite is successfully prepared by a sol–gel technique followed by subsequent carbonthermal reduction process. The structure and performance of 9LiFePO4–Na3V2(PO4)3/C composite have been investigated by XRD, SEM, TEM, EDS, CV and EIS. The result shows that the Na3V2(PO4)3 acting as ionic conductor improves the lithium ion transmission rate, while a thin amorphous carbon layer on the surface of nanoparticles and interfacial structure between the two phase enhances the electronic transmission rate of the composite. The synergistic effect of continual conductive carbon network and Na3V2(PO4)3 phase facilitates the diffusion of lithium ion and electron, ensures the stability of the LiFePO4 nanoparticles by limiting the direct contact of LiFePO4 particle with the electrolyte and ultimately improve the rate capability and long-cycling life of the material. The 9LiFePO4–Na3V2(PO4)3/C composite delivers discharge capacities of 151.2, 144.9 and 118.1mAhg−1 at 1.0, 2.0, 5.0 C, respectively, with high capacity retention up to 88.2% after 2000cycles at 2.0 C, exhibiting good electrochemical performance compared with that of the pristine one.

Enhanced electrochemical performance of LiFePO4 cathode with carbon-TiO2 hybrid coating

In this paper, hydrothermal method was conducted to synthesize LiFePO4 raw material. Carbon and TiO2 hybrid coating was prepared on the surface of LiFePO4 through sol–gel method, the tiny TiO2 particles were dispersed homogeneously on the surface and its size is about 2–4 nm. The rate performance testing proved that appropriate content TiO2 in the hybrid coating could obviously improve the rate performance of LiFePO4. The samples with 0.2 wt% (nominal) TiO2 particles in the hybrid coating owned the optimal rate performance at 0.5C, 1C, 3C and 5C, respectively. The reason was that TiO2 particles enlarged the interface in coating layer. This hybrid structure can provide more reaction sites for Li+ ion insertion/extraction. Another advantage of this carbon and TiO2 hybrid coating is that it does not need to strictly limit the content of carbon in the coating, which is very useful for scale production of carbon coating process for LiFePO4.

Enhanced electrochemical performance of LiFePO4 cathode with the addition of fluoroethylene carbonate in electrolyte

The effect of the fluoroethylene carbonate (FEC) addition in electrolyte on LiFePO4 cathode performance was investigated in low-temperature electrolyte LiPF6/EC/PC/EMC (0.14/0.18/0.68). Cyclic voltammetry, electrochemical impedance spectroscopy, and charge/discharge tests were conducted in this work. In the presence of FEC, the polarization of LiFePO4 electrode decreased both at room and low temperatures. Meanwhile, the exchange current density increased. The rate capability of LiFePO4 electrode was greatly enhanced as well. The morphology of the solid electrolyte interphase (SEI) on LiFePO4 surface was modified with the addition of FEC as confirmed by scanning electron microscopy measurement. A compact film with small impedance was formed on LiFePO4 surface compared to the case of FEC-free. The compositions of the film were analyzed by X-ray photoelectron spectroscopic measurement. The contents of Li x PO y F z , LiF, and the carbonate species generated from solvents decomposition were reduced. The modified SEI promoted the migration of lithium ion through the electrode/electrolyte interphase and enhanced the electrochemical performance of the cathode.

Enhanced electrochemical performance of LiFePO4 cathode with in-situ chemical vapor deposition synthesized carbon nanotubes as conductor

In this paper, carbon nanotubes (CNTs) are added in order to investigate their influence on the electronic conductivity of LiFePO4 cathode. CNTs/LiFePO4 composites are prepared by in-situ chemical vapor deposition method and the traditional mechanical mixture method respectively in order to investigate the influence of CNTs as an additive on the electrochemical performance of LiFePO4 cathode. The particle morphology and electrochemical performances of the CNTs/LiFePO4 composites are characterized and compared with commercial cathodes, LiFePO4 mixed with carbon black. The in-situ synthesized CNTs/LiFePO4 composite by chemical vapor deposition method maintains full retaining ratio after 100 cycles at 1C and 94.5% retention after 20 cycles at 10C, which precede the CNTs/LiFePO4 composite fabricated by the mechanical mixture method as well as the commercial cathode. The enhanced electrochemical performance is due to the excellent interface bonding between LiFePO4 and CNT in in-situ synthesized CNTs/LiFePO4 composites. The interface benefits the electronic conductivity of the composites, as well as the polarization reduction.

The Comparison of Carbon Conductive Additives with Different Dimensions on the Electrochemical Performance of LiFePO4 Cathode

The Comparison of Carbon Conductive Additives with Different Dimensions on the Electrochemical Performance of LiFePO4 Cathode

Influence of carbon coating porosity on the electrochemical performance of LiFePO4 cathode

Electrochemical performance of LiFePO4/C should be strongly dependent on the carbon coating structure for core-shell nanocomposites. In this work two types of LiFePO4/C composites with the same carbon coating thickness were prepared using a sol–gel technique, enabling direct comparison of the influence of carbon coating porosity on the performance of LiFePO4/C cathodes. It was found that the material with a distribution of dual mesopores delivers better electrochemical performance than the one with a narrow pore size distribution.

The effect of Cr doping on Li ion diffusion inLiFePO4 from first principles investigations and Monte Carlo simulations

Using the adiabatic trajectory method, the migration energy barriers for the migration ofLi ions and Cr ions along the one-dimensional diffusion pathway in pure and Cr dopedLiFePO4 are obtained from first principles calculations. The results show that while Li ions candiffuse along the diffusion pathway easily, Cr ions do not easily diffuse away from theirinitial positions. This means that the heavy Cr ions will block the one-dimensionaldiffusion pathway of the material. Monte Carlo simulations are performed to evaluatethe influences of the blocking behaviours on the electrochemical performance ofLiFePO4 cathode material for Li ion secondary batteries. The results show that the evaluatedcapacity is highly sensitive to the amount of the dopant, the size of the super-cell beingused for simulation (particle size of the powder cathode material) and the Monte Carlosteps for statistics (charge–discharge current density).