Lithium Iron Phosphate Cathode Research Articles

Glass Fiber Reinforced Epoxy-Amine Thermosets and Solvate IL: Towards New Composite Polymer Electrolytes for Lithium Battery Applications.

To effectively use (Li) lithium metal anodes, it is becoming increasingly necessary to create membranes with high lithium conductivity, electrochemical and thermal stabilities, as well as adequate mechanical properties. Composite gel polymer electrolytes (CGPE) have emerged as a promising strategy, offering improved ionic conductivity and structural performance compared to polymer electrolytes. In this study, a simple and scalable approach was developed to fabricate a crosslinked polyethylene oxide (PEO)-based membrane, comprising two different glass fiber reinforcements, in terms of morphology and thickness. The incorporation of a solvated ionic liquid into the developed membrane enhances the ionic conductivity and reduces flammability in the resulting CGPE. Galvanostatic cycling experiments demonstrate favorable performance of the composite membrane in symmetric Li cells. Furthermore, the CGPE demonstrated electrochemical stability, enabling the cell to cycle continuously for more than 700 h at a temperature of 40 °C without short circuits. When applied in a half-cell configuration with lithium iron phosphate (LFP) cathodes, the composite membrane enabled cycling at different current densities, achieving a discharge capacity of 144 mAh·g-1. Overall, the findings obtained in this work highlight the potential of crosslinked PEO-based composite membranes for high-performance Li metal anodes, with enhanced near room temperature conductivity, electrochemical stability, and cycling capability.

Electrochemical analysis on the role of disulfide bonds in polysulfide-co-polyoxide as cathode active binder for enhanced storage capacity of lithium-metal batteries

The present article is aimed at elucidation on the role of disulfide bonds in enhancement of energy storage capacity of lithium metal battery using polysulfide-co-polyoxide as cathode active binder in lithium metal batteries. Upon photocuring via ‘thiol-ene’ reaction, the resulting thioplast-co-trimethylolpropane ethoxylate triacrylate (TMPETA) co-network is flexible containing disulfide and ether oxygen moieties. Ionic conductivity of the polymer electrolyte membrane containing Thioplast-co-TMPETA network/plasticizer/lithium salt reaches the superionic conductor level of 10−3 S cm−1 at room temperature. To further improve the electrochemical performance, Thioplast-co-TMPETA co-networks were used as a binder, in lieu of polyvinylidene fluoride (PVDF), for lithium iron phosphate (LFP) cathode. Of particular interest is the achievement of a high overall specific capacity of ∼265 mAh g−1 initially which stabilizes at ∼185 mAh g−1 after 35 cycles. These values certainly exceeded the theoretical value of 170 mAh g−1 for neat LFP cathode. This capacity enhancement may be attributed to the disulfide bonds of polysulfide constituent undergoing SS bond scission followed by electron acceptor-donor interactions between sulfide radicals and Li cations. Moreover, the polysulfide-co-polyoxide binder also works as a cathode active material with a specific capacity of 122–103 mAh g−1 in the potential range of 1.0–3.0 V showing reasonable capacity retention of ∼85% and Coulombic efficiency of ∼97%.

Development of a roll-to-roll high-speed laser micro processing machine for preparing through-holed anodes and cathodes of lithium-ion batteries

Aiming to improve the battery performance of lithium-ion batteries (LIBs), modification of the cathodes and anodes of LIBs using laser beams to prepare through-holes, non-through-holes or ditches arranged in grid and line patterns has been proposed by many researchers and engineers. In this study, a laser processing system attached to rollers, which realizes this modification without large changes in the present mass-production system, was developed. The laser system apparatus comprises roll-to-roll equipment and laser equipment. The roll-to-roll equipment mainly consists of a hollow cylinder with openings on its circumferential surface. Cathode and anode electrodes for LIBs are wound around the cylinder in the longitudinal direction of the electrodes. A pulsed beam reflected from the central axis of the cylinder can continuously open a large number of through-holes in the thin electrodes. Through-holes were formed at a rate of 100 000 holes per second on lithium iron phosphate cathodes and graphite anodes with this system. The through-holed cathodes and anodes prepared with this system exhibited higher C-rate performance than nontreated cathodes and anodes.

Electrochemical modeling and simulation of the improved high-rate discharging performance of through-holed LiNi1/3Mn1/3Co1/3O2 cathodes prepared with a picosecond pulsed laser for lithium-ion batteries

In previous papers, we reported that the through-holing of lithium iron phosphate cathodes for lithium-ion batteries with a picosecond pulsed laser efficiently improved the high-rate performance. The enhancement of the Li+ ion transfer was caused by the increase in the pathway of the Li+ ions to/from the lithium metal oxide LiNi1/3Mn1/3Co1/3O2 (NMC) particle surfaces through the sidewall in the through-holes, and this potentially caused the improvement in the high-rate performance. To clarify our deduction, the structural parameters that caused similar experimental results and calculated values were determined by changing the structural parameters of the NMC layer in the through-holed cathodes. The consideration of the structural parameter distribution around a through-hole lead to an agreement between the experimental data and calculated values. From the structural parameters determined, the through-holed structure had negative factors caused by laser irradiation and disrupted the electronically conductive paths within the NMC layer. However, the high-rate performance improvement could be achieved due to the increased area accessible to lithium ions in the through-holes.

Microsized Silicon/Carbon Composite Anodes through In Situ Polymerization of Phenolic Resin onto Silicon Microparticles for High-Performance Lithium-Ion Batteries

Silicon (Si) has been gradually explored as a next-generation anode material to replace traditional graphite anodes in lithium-ion batteries (LIBs) due to its high specific capacity (3579 mAh g–1 at room temperature). In terms of cost and tap density, silicon microparticles (SiMPs) are more advantageous than silicon nanoparticles (SiNPs) in high energy density LIBs, but they are also plagued by the more serious volume effect. Here, we design a silicon/carbon (Si/C) composite anode through the in situ polymerization of phenolic resin (PF) onto SiMPs, and after pyrolysis, SiMPs are tightly coated with pyrolytic carbon layers. When applied in LIBs, the composite anodes (μSi@PF) exhibit excellent cycling performance (1283 mAh g–1 after 400 cycles at 2 A g–1) and rate performance (a reversible capacity of about 1000 mAh g–1 at 8 A g–1). The full cell with lithium iron phosphate cathodes and μSi@PF anodes can maintain 87.7% capacity retention after 100 cycles. The great electrochemical performance can be ascribed to the rational structure design of μSi@PF in which PF pyrolytic carbon as a shell around SiMPs can accommodate the volume change of SiMPs during cycling and reduce the internal impedance. This is the first attempt to construct Si/C composites by in situ polymerizing PF resin onto SiMPs, and the great performance of Si/C anode provides a reference for the practical application of SiMPs.

Solvent-free lithium iron phosphate cathode fabrication with fibrillation of polytetrafluoroethylene

Fabricating electrode for lithium-ion batteries (LiBs) with solvent-free (SF) procedure can save energy and improve electrochemical performance simultaneously. Polymer fibrillation is one of the most promising SF procedures due to its feasibility for upscale production. The hardness of lithium iron phosphate (LFP) impedes its SF fabrication with polytetrafluoroethylene (PTFE) fibrillation. In this study, we successfully expanded PTFE fibrillation for SF LFP electrode fabrication with the help of carbon nanotubes (CNTs). CNTs increase the conductivity of electrode, and act as matrix for LFP particles to ensure relative displacement to further fibrillate PTFE to form self-supporting electrode film when the dry mixture was hot rolled. The SF LFP/hard carbon full cells were fabricated and demonstrated comparable electrochemical performance to slurry casting (SC) fabricated LFP electrode. The initial coulombic efficiency (ICE) of full cell increased to more than 95% after prelithiation.

Versatile solid polymer electrolytes from clickable poly(glycidyl propargyl ether) for lithium metal batteries

We present three new graft copolymers for the application as solid polymer electrolytes (SPEs) in solvent-free, all solid-state lithium metal batteries (LMBs), based on the clickable poly (glycidyl propargyl ether) platform. These fully amorphous polymers consist of an all-ether polymer backbone and different additional Li+-coordinating oxo-functionalities - diester, carbonate and phosphate ester - in the attached sidechain. We aim to address the fundamental question on the influence of Li+-coordination in such doubly functionalized systems having competing Li+-coordination functional groups. We prepared polymer nanocomposite SPEs based on these novel polymers mixed with a highly-dissociating lithium salt (LiTFSI) and TiO2 nanofillers, which improve the electrolyte-electrode compatibility. We perform an extensive and comparative investigation in terms of physicochemical and electrochemical properties including ionic conductivity, lithium transference number, lithium plating and stripping as well as the fabrication and cycling of LMBs utilizing lithium iron phosphate (LFP) cathodes. Thermal characterization is coupled with temperature-dependent ionic conductivity measurements and detailed IR spectroscopy to understand the mechanistic properties and selectivity of the Li+ coordination and conduction. Two of the nanocomposite SPEs show efficient battery cycling with initial capacities of ca. 150 mAh g−1 and a capacity retention of ca. 70–80 % after 100 cycles.

Improvement of electrochemical properties of lithium iron phosphate cathode by rare earth oxides modification

LiFePO4 cathode material has sluggish Li-ion diffusivity, which largely depends on surface modification to accelerate its slow kinetic process. Metal oxides, such as Al2O3, are promising coating materials to improve the capacity retention of the cathode materials in lithium-ion batteries, but their improvement on the diffusion rate of Li-ion is limited. In order to obtain the lithium iron phosphate cathode material with excellent rate and cyclic stability, this paper uses the advantages of La2O3 which has both good stability and low lithium ion diffusion barrier to prepare LiFePO4/C@La2O3 by a simple and easy operation method. The cathode of LiFePO4/C@La2O3 shows high lithium ion diffusivity of 1.4982 × 10−13 and decreased interface impedance by calculating the Li+ diffusion coefficient and measuring conductivity. Furthermore, the LiFePO4/C@La2O3 exhibits excellent rate capacibility (126 mAh g−1 at 10 C within 2.4–4.2 V) and long-cycle stability (96.5% capacity retention at 1 C after 500 cycles). These results indicate that further research on these oxide coating materials can enlarge the applicability of these materials.

Synthesis and electrochemical behavior of K+ and Mn2+ co-doped LiFePO4/C as a cathode material for lithium-ion batteries and the mechanism of modification

Mn and K co-doped lithium iron phosphate (LFP) cathode materials are obtained by an expedient solvothermal method. The contributions of the two doped elements to the LFP are discussed in detail by density functional theory (DFT) calculations and several characterizations. The presence of Mn improves the energy band and diffusion kinetics, while the stabilized structure and the widened diffusion channel are attributed to K. Benefiting from the expanded ion channels and stable structure that resulting from the doping treatment, the LFP cathode exhibits a remarkable capacity of 145 mAh·g−1 at 5 C and demonstrates a 96% retention rate after 400 cycles. In particular, the interaction between the two doping elements, which is less mentioned in other literature is discussed by building a failure model of the control group. The samples co-doped with K and Mn (KLMFP) showed better electrochemical performance than the other groups in cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and charge–discharge cycling tests.

An enhanced interface between garnet solid electrolyte and lithium through multifunctional lithium titanate anode-additive for solid-state lithium batteries

Garnet-structured solid-state electrolytes are getting considerable attention due to their high figure of merit over other inorganic solid-state electrolytes. The high lithium-ion conductivity and exceptional stability with metallic lithium over a wide voltage window open the door for the practical realization of an all-solid-state battery. However, the lithiophobic nature of garnet solid electrolytes creates huge interface resistance, which restricts achieving high critical current density. Herein a multifunctional composite anode containing lithium metal and lithium titanate (Li4Ti5O12) is introduced to tackle the interface challenges with the garnet solid electrolyte. The partial reduction of titanium in the composite enhances the electronic conductivity of the anode, and the intrinsic structural advantages of lithium titanate are expected to accommodate volume change as well. The prepared symmetric cell with the composite anode is found to have a minimal areal-specific resistance of 27 Ω cm2, while that of the pristine lithium anode is 249 Ω cm2. The cell has also run with a better critical current density (0.35 mA cm−2) than the pristine lithium (0.15 mA cm−2). A full cell study with a lithium iron phosphate cathode offers a capacity of 145 mAh g−1 at 0.2 C and runs for 100 cycles at 1 C with minimum capacity loss.

Proof-of-Concept study of ion-exchange method for the recycling of LiFePO4 cathode

Recycling spent lithium iron phosphate (LFP) cathodes in an economically sustainable way remains a great challenge due to their low-value elemental composition. Thus, both low-cost technology together with a high-value product are critical for the recovery of the LFP materials. In this study, the commercially mature ion-exchange (IX) method was explored to recover Li from LFP material for the first time. The feasibility of Li-H and Li-K IX reactions using strong and weak acid cation exchange resins was systematically investigated from the thermodynamic and kinetic perspectives. Different organic and inorganic acids were explored to obtain the feeding solution. The IX efficiency was greatly affected by the pH of the feeding solutions. Oxalic acid leaching solution with mild pH value and low iron impurity were determined to be the optimal feeding solution for IX reaction. The kinetics of IX and regeneration reaction were fast, and the resins can be reused several times without loss of IX capacity. Along with the P element remaining in the leaching solution, the Li-K IX reaction delivered a potential product of multi-elemental fertilizer. This simple and economical technology provides a practical recycling strategy for the spent LFP batteries.

Na‐Rich Na3V2(PO4)3 Cathodes for Long Cycling Rechargeable Sodium Full Cells

AbstractNASICON‐type sodium vanadium phosphate (Na3V2(PO4)3, or NVP) cathode materials have great potential for fast charging and long cycling sodium‐ion batteries (SIBs) similar to lithium iron phosphate (LiFePO4, or LFP) cathode materials used in lithium‐ion batteries (LIBs). However, the cycle life and energy density in the full cell using NVP materials need to be significantly improved. This paper investigates the degradation mechanisms of NVP‐based SIBs and identifies the Na loss from the cathode to the anode solid electrolyte interphase (SEI) reactions as the main cause of capacity degradation. A new Na‐rich NVP cathode (e.g., Na4V2(PO4)3, or Na4VP) is developed to address the Na loss problem. Conventional NVP can be easily transformed into the Na4VP by a facile and fast chemical solution treatment (30 s). Na‐free‐anode Na4VP and hard carbon‐Na4VP full cells are assembled to evaluate the electrochemical properties of the Na‐rich NVP cathode. The Na4VP cathode provides excess Na to compensate for the Na loss, resulting much longer cycle life in the full cells (>400 cycles) and a high specific energy and power density. Good low‐temperature performance is also observed.

Development Status and Trend of Lithium Ion Cathode Materials

Driven by carbon peaking and carbon neutrality goals and market demand, China’s new energy vehicles have entered a stage of rapid development, which has led to significant changes in the industry of power battery cathode materials and its market pattern. This paper introduces the classification, advantages and disadvantages, and application scenarios of lithium ion cathode materials and focuses on the market status and industrial pattern of lithium iron phosphate cathode materials and ternary cathode materials before discussing the future industrial development trend.

A perspective on the recovery mechanisms of spent lithium iron phosphate cathode materials in different oxidation environments

Oxidative extraction has become an economically viable option for recycling lithium (Li) from spent lithium iron phosphate (LiFePO4) batteries. In this study, the releases behaviour of Li from spent LiFePO4 batteries under different oxidizing conditions was investigated with sodium hypochlorite (NaClO) as the solid oxidant. We revealed that, due to the intervention of graphitic carbon, the generated species of Li in mechanochemical oxidation (NaClO:LiFePO4 at a molar ratio of 2:1, 5 min, and 600 rpm) was lithium carbonate (Li2CO3). The graphite layer provided a channel for the conversion of Li species released by mechanochemical oxidation. While in hydrometallurgical oxidation (NaClO:LiFePO4 at a molar ratio of 2:1 and 12.5 min), the presence of hydrogen species led to the formation of lithium chloride (LiCl). Moreover, life cycle assessment (LCA) demonstrated that for recycling 1.0 kg of spent LiFePO4 batteries, mechanochemical and hydrometallurgical oxidation could reduce carbon footprints by 2.81 kg CO2 eq and 2.88 kg CO2 eq, respectively. Our results indicate that the oxidative environment determines the release pathway of Li from the spent LiFePO4 cathode material, thereby regulating the product forms of Li and environmental impacts. This study can provide key technical guidance for Li recycling from spent LiFePO4 batteries.

Investigating the Cyclability and Stability at the Interfaces of Composite Solid Electrolytes in Li Metal Batteries.

Despite the fact that much work has been dedicated to finding the ideal additive for composite solid electrolytes (CSEs) for lithium-based solid-state batteries, little is known about the properties of a CSE that enable stable cycling with a lithium metal anode. In this work, we use three CSEs based on lithium nitride (Li3N), a fast lithium-ion conductor, and lithium hydroxide (LiOH) to investigate the properties and interfacial interactions that impact the cyclability of CSEs. We present a method for stabilizing Li3N with a shell of LiOH, and we incorporate Li3N, core-shell particles, and LiOH into CSEs using polyethylene oxide (PEO) and lithium bis(trifluoromethanesulfonyl)imide. Through improved interfacial chemistry, CSEs with core-shell particles have superior electrochemical cycling performance compared to those with unprotected Li3N in symmetric Li-Li cells. This CSE features a high ionic conductivity of 0.66 mS cm-1 at 60 °C, a high critical current density of 1.2 mA cm-2, and a wide voltage window of 0-5.1 V. Full cells with the core-shell CSE and lithium iron phosphate cathodes exhibit stable cycling and high reversible specific capacities in cells as high as 2.5 mAh cm-2. We report that the improved ionic conductivity and amorphous PEO content have a limited effect on the solid-state electrolyte performance, while improving the electrolyte-Li metal anode interface is key to cycling longevity.

Effective stripping and reutilization of LiFePO4 cathode waste from retired lithium ion batteries

The recycling of retired lithium ion batteries (LIBs) plays a vital role in alleviating the energy crisis and preventing secondary pollution. However, the unstable properties of waste materials greatly restricts the reuse of recycled materials in the industrial energy domain. Herein, we applied water as stripping solvent to effectively dispose of lithium iron phosphate (LiFePO4) cathode scrap. The results showed that the stripping rate of cathode scrap could reach more than 92%, and the recycling did not give rise to any impact on the structure of the cathode material under optimized condition. The molar ratios of elements were signed as n (Li): n (Fe): n (P) = 5 : 4.6: 4.95 by inductively coupled plasma emission spectroscopy (ICP-OES) and energy disperse spectroscopy (EDS). The Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) showed that the PVDF was completely invisible after sintering. The LiFePO4 materials calcined at different temperature for 10 h under argon atmosphere showed excellent constant current charge-discharge performance and good cycle life, which reflected the stability of the olivine structure. The LiFePO4 cathode material directly calcined at 650 °C for 10 h exhibited the best charge-discharge specific capacity with a high Coulombic efficiency of 99.2%. Cyclic voltammetry (CV) tests showed that the re-sintered LiFePO4 material had a less redox polarized potential compared with the retired LiFePO4 material. The non-structure-damaging recycling mode also provides a green and effective direction for the recovery and recyclability of retired LiFePO4.

(Fe, Ni)-ZIF-8 derived sp2-C-rich carbon as surface coating for enhancing commercial LiFePO4 performance

LiFePO4 is the widely accepted high-performance cathode material for lithium-ion batteries with good economy and safety. Carbon encapsulation is the ordinary way to overcome its weakness of poor conductivity. In this work, nitrogen-doped carbon coating was created by growing FeNi-ZIF-8 on the lithium iron phosphate surface and then calcining at high temperature. This network structure of nitrogen-doped carbon surrounding the lithium iron phosphate is rich in both sp2-C and defectives, which promote the ions and electron conductivity throughout nanoparticles to enhance the rate performance and cycling stability of the lithium iron phosphate cathode. The results show that the synthesized LFP@NC(FeNi) composites provide a capacity of 166.6 mAh g−1 at 0.1C and 72.9 mAh g−1 at 10C, respectively. The capacity retention rate of 500 cycles at 5C is about 94.2%. The high-rate performance and cycle stability fulfill the requirements of rechargeable lithium batteries.

Parameter Study on the Recycling of LFP Cathode Material Using Hydrometallurgical Methods

The need to recover critical elements from lithium-ion batteries is undisputed. The further development of cathode materials and the move towards cheaper alternatives make it necessary to adapt the corresponding hydrometallurgical recycling processes. In the best case, however, a process is so flexibly structured and designed that it can be used for a variety of cathode materials with different compositions. The leaching of nickel manganese cobalt oxide with sulfuric acid and a reducing agent has already been demonstrated and optimized in previous research work. Based on these data, an evaluation of the process as well as a parameter study for lithium iron phosphate cathode material, which has recently been used with increasing frequency but has a significantly lower valuable metal content, was carried out within the scope of this publication. By using the synergy effects that occur, an optimized parameter combination for the leaching of the critical element lithium could be found and further critical factors identified.

Energy-Efficient Synthesis of Surface-Modified LiCoO2 for Better Performance at Higher Voltage, Higher Rate through Suppression of Transition Metal Dissolution, and Li-Vacancy Ordering in the Monoclinic Phase

The necessity for a 300-mile driving range with 60–70 kWh of energy at the battery pack level has steered LIB research toward high-energy-density-based cathode materials. Because of its larger theoretical capacity (274 mAh g-1) compared to lithium iron phosphate and lithium manganese oxide-based cathodes, layered oxide cathodes have the potential to attain higher energy density LIBs. Despite its greater cost, LCO still has a higher demand (>21%) than any other cathode material. The current research on LiCoO2 (LCO) as a cathode is centered on its surface protection which allows for the extraction of more than half of the Li. Several techniques have been investigated to protect the LCO surface from direct contact with the liquid electrolyte while retaining structural integrity at higher cut-off voltages (≥4.5 V). The LiCo0.5Mn1.5O4 (LCMO) coating material is utilized here, which has a spinel structure and allows for three-dimensional (3D) lithium diffusion. Microwave-assisted heating was used for the synthesis of surface-modified LCO material. During synthesis, some Mn3+ diffused into the bulk of LCO, increasing its lattice parameter and allowing Li-ion kinetics in LCO to function at a faster cycling rate for longer cycle life. The modified LCO is subjected to a higher rate (3C) for longer cycle life with ~57.3 % capacity retention after 500 cycles. Here, a novel understanding of higher rate capability (at 3C, 5C, and 10C current rates) and stability at the higher cut-off voltage for modified LCO has been proposed. Entropy measurements were used to evaluate the arrangement of Li-ion and vacancy in the LCO lattice at different states of charge to investigate the stability of coated LCO at the higher voltage. The full cell and 15 mAh pouch-type cell were also fabricated with Si as an anode for its commercial scalability.

Mechanisms of Lithium-Ion Transport in Solid-State Electrolyte and Cathode Materials Prepared By PVD

Conventional liquid-state lithium-ion batteries are currently limited in their energy density, lifetime, thermal stability, and safety. The design of viable solid-state batteries shows promise to improve upon the shortcomings of liquid cells. Removal of organic electrolytes increases the lifetime while making these batteries more environmentally friendly and safe. Solid-state batteries also have the potential to demonstrate higher energy density and provide ultrafast charging. However, these desirable properties require significant efforts to uncover and utilize the chemical, morphological, and electrochemical properties of solid-state electrolytes and cathode nanocomposites. This study addresses physical vapor deposition (PVD) technology for design of solid-state material architectures with the properties needed to create high-performance electrochemical cells. The PVD process allows cathodes and electrolytes to be deposited as dense films, thereby increasing their energy density and electrochemical performance. Furthermore, this process results in excellent adhesion between dissimilar materials allowing for increased electrical and ionic conductivity. This work uses lithium oxyhalide electrolytes and eco-friendly lithium iron phosphate cathodes, which were both deposited in vacuum using radio frequency power and magnetron sputtering sources. A co-deposition technique was used to successfully deposit thin film layers of cathode, electrolyte, cathode/electrolyte mixture, and carbon thin films in a single process. Electrochemical cells with different functional layers deposited by PVD (~7 mm) were compared to the cells with commercial LFP cathodes (~32 mm thick). The electrochemical cells created by PVD showed lower charge transfer resistances and high electrochemical stability at ultra-high (10C) charging rates. Significant improvements in performance are expected to continue as the process is improved in terms of ionic and electronic transport at cathode-electrolyte interfaces. The authors acknowledge financial support from the DOD Navy SBIR Phase II project (N68335-18-C-0021), the NSF IUCRC program for supporting the “Center for solid-state electric power storage” (#2052631), and the South Dakota “Governor’s Research Center for electrochemical energy storage”. Figure 1