Hydrothermal synthesis of lithium iron phosphate cathodes

High-rate LiFe0.75Mn0.25PO4/C cathode material for lithium-ion battery was prepared by oriented growth of precursor crystal plane

The emergence of the lithium-ion battery as a subject of intense research interest has propelled of high-energy-density LiFexMn1-xPO4(LFMP) becoming a prominent area of investigation. However, the material suffers from inherently low electronic conductivity due to its olivine structure, which imposes severe constraints on electron transport kinetics, thus adversely impacting both charge-discharge rates and overall electrochemical performance. We propose an innovative protocol for high-precision reaction mechanism modulation. By employing Fe3(PO4)2·8H2O with strategically enhanced (020) crystal plane exposure as a pivotal precursor, we synthesized LiFe0.75Mn0.25PO4/C cathode material featuring a shorter ion diffusion path. Comprehensive characterization coupled with electrochemical validation revealed that the resultant cathode material exhibits a smaller particle size and more uniform morphology, along with a superior rate performance and cycle stability. The discharge specific capacity is 144.1 mAh g-1 and the capacity retention reaches 96.1 % over 1000 cycles at a 1C rate. The findings demonstrate that the regulation of the growth trajectory of the precursor Fe3(PO4)2·8H2O crystal plane can markedly enhance the electronic conductivity and Li+ mobility of the cathode material, thereby optimising the electrochemical performance.

From Mining to Manufacturing: Scientific Challenges and Opportunities behind Battery Production

This Review explores the status and progress made over the past decade in the areas of raw material mining, battery materials and components scale-up, processing, and manufacturing. While substantial advancements have been achieved in understanding battery materials, the transition to large-scale manufacturing introduces scientific challenges that must be addressed from multiple perspectives. Rather than focusing on new material discoveries or incremental performance improvements, this Review focuses on the critical issues that arise in battery manufacturing and highlights the importance of cost-oriented fundamental research to bridge the knowledge gap between fundamental research and industrial production. Challenges and opportunities in integrating machine learning (ML) and artificial intelligence (AI) to digitalize the manufacturing process and eventually realize fully autonomous production are discussed. The review also emphasizes the pressing need for workforce development to meet the growing demands of the battery industry. Potential strategies are suggested for accelerating the manufacturing of current and future battery technologies, ensuring that the workforce is equipped with the necessary skills to support research, development, and large-scale production.

Investigating the Reductive Phosphatization Reaction Pathway in the Synthesis of Transition Metal Phosphates: A Case Study on Titanium Phosphates

Reductive phosphatization is an original synthesis approach to the formation of transition metal phosphates (TMPs). The approach enables the synthesis of known TMPs, but also new compounds, especially with transition metals in a low-valent state. However, to exploit the enormous potential of this synthesis method, it is necessary to identify and characterize all of the potential intermediates and final synthesis products. Here, we report on in situ synchrotron X-ray powder diffraction experiments to unravel the temperature-dependent formation pathway of TMPs using TiO2-NH4H2PO2 as an example. The pathway consists of several consecutive steps, including the melting of NH4H2PO2, which acts as a reducing agent and a reaction medium. A reduction in the ratio of TiO2 to NH4H2PO2 decelerates the reaction and causes increased impurity formation. The hypophosphite melt reduces Ti4+ in TiO2 to Ti3+, and a previously unknown compound, denoted as Ti(III)po with chemical composition (NH4)xH1-xTi(HPO4)2, is formed. In a subsequent step, (NH4)xH1-xTi(HPO4)2 reacts in a polycondensation reaction to form monoclinic NH4TiP2O7, denoted as Ti(III)p in our earlier work.

Life Cycle of LiFePO4 Batteries: Production, Recycling, and Market Trends

Significant attention has focused on olivine-structured LiFePO4 (LFP) as a promising cathode active material (CAM) for lithium-ion batteries. This iron-based compound offers advantages over commonly used Co and Ni due to its lower toxicity abundance, and cost-effectiveness. Despite its current commercial use in energy storage technology, there remains a need for cost-effective production methods to create electrochemically active LiFePO4. Consequently, there is ongoing interest in developing innovative approaches for LiFePO4 production. While LFP batteries exhibit significant thermal stability, cycling performance, and environmental benefits, their growing adoption has increased battery disposal rates. Improper disposal practices for waste LFP batteries result in environmental degradation and the depletion of valuable resources. This review comprehensively examines diverse synthesis approaches for generating LFP powders, encompassing conventional methodologies alongside novel procedures. Furthermore, it conducts an in-depth assessment of the methodologies employed in recycling waste LFP batteries. Moreover, it emphasizes the importance of LFP cathode recycling and investigates pretreatment techniques to enhance understanding. Additionally, it provides valuable insights into the recycling process of used LFP batteries, aiming to raise awareness regarding the market for retired LFP batteries and advocate for the enduring sustainability of lithium-ion batteries.

A review of innovative approaches for onsite management of PFAS-impacted investigation derived waste

The historic use of aqueous film-forming foam (AFFF) has led to widespread detection of per- and polyfluoroalkyl substance (PFAS) in groundwater, soils, sediments, drinking water, wastewater, and receiving aquatic systems throughout the United States (U.S.). Prior to any remediation activities, in order to identify the PFAS-impacted source zones and select the optimum management approach, extensive site investigations need to be conducted. These site investigations have resulted in the generation of considerable amount of investigation-derived waste (IDW) which predominantly consists of well purging water and drill fluid, equipment washing residue, soil, drill cuttings, and residues from the destruction of asphalt and concrete surfaces. IDW is often impacted by varying levels of PFAS which poses a substantial challenge concerning disposal to prevent potential mobilization of PFAS, logistical complexities, and increasing requirement for storage as a result of accumulation of the associated wastes. The distinct features of IDW involve the intermittent generation of waste, substantial volume of waste produced, and the critical demand for onsite management. This article critically focuses on innovative technologies and approaches employed for onsite treatment and management of PFAS-impacted IDW. The overall objective of this study centers on developing and deploying end-of-life treatment technology systems capable of facilitating unrestricted disposal, discharge, and/or IDW reuse on-site, thereby reducing spatial footprints and mobilization time.

Many-Particle Li Ion Dynamics in LiMPO4 Olivine Phosphates (M = Mn, Fe)

LiMPO₄ (M = Mn, Fe) olivine phosphates are important materials for battery applications due to their stability, safety, and reliable recharge cycle. Despite continuous experimental and computational investigations, several aspects of these materials remain challenging, including conductivity dimensionality and how it maps onto Li pathways. In this work, we use a refined version of our finite temperature molecular dynamics "shooting" approach, originally designed to enhance Li hopping probability. We perform a comparative analysis of ion mobility in both materials, focused on many-particle effects. Therein, we identify main [010] diffusion channels, as well as means of interchannel couplings, in the form of Li lateral [001] hopping, which markedly impact the overall mobility efficiency as measured by self-diffusion coefficients. This clearly supports the need of many-particle approaches for reliable mechanistic investigations and for battery materials benchmarking due to the complex nature of the diffusion and transport mechanisms.

Will Vanadium-Based Electrode Materials Become the Future Choice for Metal-Ion Batteries?

Metal-ion batteries have emerged as promising candidates for energy storage system due to their unlimited resources and competitive price/performance ratio. Vanadium-based compounds have diverse oxidation states rendering various open-frameworks for ions storage. To date, some vanadium-based polyanionic compounds have shown great potential as high-performance electrode materials. However, there has been a growing concern regarding the cost and environmental risk of vanadium. In this Review, all links in the industry chain of vanadium-based electrodes were comprehensively summarized, starting with an analysis of the resources, applications, and price fluctuation of vanadium. The manufacturing processes of the vanadium extraction and recovery technologies were discussed. Moreover, the commercial potentials of some typical electrode materials were critically appraised. Finally, the environmental impact and sustainability of the industry chain were evaluated. This critical Review will provide a clear vision of the prospects and challenges of developing vanadium-based electrode materials.

Crystal Structures of Two Titanium Phosphate-Based Proton Conductors: Ab Initio Structure Solution and Materials Properties

Transition-metal phosphates show a wide range of chemical compositions, variations of the valence states, and crystal structures. They are commercially used as solid-state catalysts, cathode materials in rechargeable batteries, or potential candidates for proton-exchange membranes in fuel cells. Here, we report on the successful ab initio structure determination of two novel titanium pyrophosphates, Ti(III)p and Ti(IV)p, from powder X-ray diffraction (PXRD) data. The low-symmetry space groups P2₁/c for Ti(III)p and P1̅ for Ti(IV)p required the combination of spectroscopic and diffraction techniques for structure determination. In Ti(III)p, trivalent titanium ions occupy the center of TiO₆ polyhedra, coordinated by five pyrophosphate groups, one of them as a bidentate ligand. This secondary coordination causes the formation of one-dimensional six-membered ring channels with a diameter d_max of 3.93(2) Å, which is stabilized by NH₄⁺ ions. Annealing Ti(III)p in inert atmospheres results in the formation of a new compound, denoted as Ti(IV)p. The structure of this compound shows a similar three-dimensional framework consisting of [PO₄]^3– tetrahedra and Ti^IV+O₆ octahedra and an empty one-dimensional channel with a diameter d_max of 5.07(1) Å. The in situ PXRD of the transformation of Ti(III)p to Ti(IV)p reveals a two-step mechanism, i.e., the decomposition of NH₄⁺ ions in a first step and subsequent structure relaxation. The specific proton conductivity and activation energy of the proton migration of Ti(III)p, governed by the Grotthus mechanism, belong to the highest and lowest, respectively, ever reported for this class of materials, which reveals its potential application in electrochemical devices like fuel cells and water electrolyzers in the intermediate temperature range.

The crystal structures of two novel transition-metal phosphates were solved via the combination of spectroscopic and diffraction methods. The reaction mechanism of the transformation of the structures was studied in situ. Additionally, the proton conductivity of the compounds was analyzed.

Low-frequency vibrational spectroscopy: a new tool for revealing crystalline magnetic structures in iron phosphate crystals

In this report, the strong-dependence of low-frequency (terahertz) vibrational dynamics on weak and long-range forces in crystals is leveraged to determine the bulk magnetic configuration of iron phosphate - a promising material for cathodes in lithium ion batteries. We demonstrate that terahertz time-domain spectroscopy - coupled with quantum mechanical simulations - can discern between various spin configurations in FePO₄. Furthermore, the results of this work unambiguously show that the well-accepted space group symmetry for FePO₄ is incorrect, and the low-frequency spectroscopic measurements provide a clearer picture of the correct structure over the gold-standard of X-ray diffraction. This work opens the door for characterizing, predicting, and interpreting crystalline magnetic ordering using low-frequency vibrational spectroscopy.

Hydrothermally synthesized nanostructured LiMnxFe1-xPO4 (x = 0-0.3) cathode materials with enhanced properties for lithium-ion batteries

Nanostructured cathode materials based on Mn-doped olivine LiMn_xFe_1−xPO₄ (x = 0, 0.1, 0.2, and 0.3) were successfully synthesized via a hydrothermal route. The field-emission scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) analyzed results indicated that the synthesized LiMn_xFe_1−xPO₄ (x = 0, 0.1, 0.2, and 0.3) samples possessed a sphere-like nanostructure and a relatively homogeneous size distribution in the range of 100–200 nm. Electrochemical experiments and analysis showed that the Mn doping increased the redox potential and boosted the capacity. While the undoped olivine (LiFePO₄) had a capacity of 169 mAh g⁻¹ with a slight reduction (10%) in the initial capacity after 50 cycles (150 mAh g⁻¹), the Mn-doped olivine samples (LiMn_xFe_1−xPO₄) demonstrated reliable cycling tests with negligible capacity loss, reaching 151, 147, and 157 mAh g⁻¹ for x = 0.1, 0.2, and 0.3, respectively. The results from electrochemical impedance spectroscopy (EIS) accompanied by the galvanostatic intermittent titration technique (GITT) have resulted that the Mn substitution for Fe promoted the charge transfer process and hence the rapid Li transport. These findings indicate that the LiMn_xFe_1−xPO₄ nanostructures are promising cathode materials for lithium ion battery applications.

Hydrothermal Alkaline Treatment for Destruction of Per- and Polyfluoroalkyl Substances in Aqueous Film-Forming Foam

The widespread use of aqueous film-forming foam (AFFF) for firefighting activities (e.g., fire training to extinguish fuel-based fires at aircraft facilities) has led to extensive groundwater and soil contamination by per- and polyfluoroalkyl substances (PFASs) that are highly recalcitrant to destruction using conventional treatment technologies. This study reports on the hydrothermal alkaline treatment of diverse PFASs present in AFFFs. Quantitative and semiquantitative high-resolution mass spectrometry analyses of PFASs demonstrate a rapid degradation of all 109 PFASs identified in two AFFFs (sulfonate- and fluorotelomer-based formulations) in water amended with an alkali (e.g., 1-5 M NaOH) at near-critical temperature and pressure (350 °C, 16.5 MPa). This includes per- and polyfluoroalkyl acids and a range of acid precursors. Most PFASs were degraded to nondetectable levels within 15 min, and the most recalcitrant perfluoroalkyl sulfonates were degraded within 30 min when treated with 5 M NaOH. ¹⁹F NMR spectroscopic analysis and fluoride ion analysis confirm the near-complete defluorination of PFASs in both dilute and concentrated AFFF mixtures, and no stable volatile organofluorine species were detected in reactor headspace gases by the gas chromatography-mass spectrometry analysis. These findings indicate a significant potential for application of hydrothermal treatment technologies to manage PFAS waste streams, including on-site treatment of unused AFFF chemical stockpiles, investigation-derived wastes, and concentrated source zone materials.

Understanding the sodium ion transport properties, deintercalation mechanism, and phase evolution of a Na2Mn2Si2O7 cathode by atomistic simulation

Molecular dynamics (MD) together with the first principles method (DFT) reveal that Na+ is capable of migrating three dimensionally in a Na2Mn2Si2O7 cathode material. Migration along the a-axis and c-axis have the same mechanism, that is, alternating between the Na1 and Na2 route with a similar local environment and distance. Long-distance hopping between two Na2 atoms or between Na1 and Na2 atoms is crucial for continuous migration along the b-axis. Also, the anti-site phenomenon is identified, and it facilitates the migration of the Na ions. Four intermediate phases are determined according to the formation energy curve and, as a result, the voltage profile is predicted accurately. The state of charge (SOC) dependency of the Na+ energy shows that the mobility of Na+ is highly inhibited in the fully discharged state. Upon the deintercalation of sodium ions, Na+ is activated immediately. A maximal DNa+ value of 3.6 × 10-9 cm2 s-1 and a low energy barrier of ca. 0.26 eV at the deintercalation level of x = 0.25 are observed. Because of the scarcity of Na+, DNa+ experiences a sharp decrease at the end of deintercalation. Despite the low level of Na+ mobility in the range of 0.25 < x < 1, Na2Mn2Si2O7 is still a potential cathode material for use in sodium ion batteries (SIBs).

Ultrasound assisted wet media milling synthesis of nanofiber-cage LiFePO4/C

To meet the objectives of the Intergovernmental Panel on Climate Change nations are adopting policies to encourage consumers to purchase electric vehicles. Electrification of the automobile industry reduces greenhouse gases but active metals for the cathode-LiCoO₂ and LiNiO₂-are toxic and represent an environmental challenge at the end of their lifetime. LiFePO₄ (LFP) is an attractive alternative that is non-toxic, thermally stable, and durable but with a moderate theoretical capacity and a low electrical conductivity. Commercial technologies to synthesize LFP are energy-intensive, produce waste that incurs cost, and involve multiple process steps. Here we synthesize LFP precursor with lignin and cellulose in a sonicated grinding chamber of a wet media mill. This approach represents a paradigm shift that introduces mechanochemistry as a motive force to react iron oxalate and lithium hydrogen phosphate at ambient temperature. Ultrasound-assisted wet media milling increases carbon dispersion and reduces the particle size simultaneously. The ultrasound is generated by a 20 kHz,500 W automatic tuning ultrasound probe. The maximum discharge rate of the LFP synthesized this way was achieved with cellulose as a carbon source, after 9 h milling, at 70% ultrasound amplitude. After 2.5 h of milling, the particle size remained constant but the crystal size continued to drop and reached 29 nm. Glucose created plate-like particles, and cellulose and lignin produced spindle-shaped particles. Long mill times and high ultrasound amplitude generate smoother particle surfaces and the powder densifies after a spray drying step.

Morphological Control of Nanostructured V2O5 by Deep Eutectic Solvents

Herein, we show a facile surfactant-free synthetic platform for the synthesis of nanostructured vanadium pentoxide (V₂O₅) using reline as a green and eco-friendly deep eutectic solvent. This new approach overcomes the dependence of the current synthetic methods on shape directing agents such as surfactants with potential detrimental effects on the final applications. Excellent morphological control is achieved by simply varying the water ratio in the reaction leading to the selective formation of V₂O₅ 3D microbeads, 2D nanosheets, and 1D randomly arranged nanofleece. Using electrospray ionization mass spectroscopy (ESI-MS), we demonstrate that alkyl amine based ionic species are formed during the reline/water solvothermal treatment and that these play a key role in the resulting material morphology with templating and exfoliating properties. This work enables fundamental understanding of the activity-morphology relationship of vanadium oxide materials in catalysis, sensing applications, energy conversion, and energy storage as we prove the effect of surfactant-free V₂O₅ structuring on battery performance as cathode materials. Nanostructured V₂O₅ cathodes showed a faster charge-discharge response than the counterpart bulk-V₂O₅ electrode with V₂O₅ 2D nanosheet presenting the highest improvement of the rate performance in galvanostatic charge-discharge tests.

A new strategy to hydrothermally synthesize olivine phosphates

A new strategy based on the P excess reaction system is innovated to hydrothermally synthesize olivine phosphates (LiMPO4), and even unoptimized samples still show competitive electrochemical performance. Meanwhile, it is found that the presence of NH4+ in the P excess reaction system is detrimental to the efficient hydrothermal synthesis of LiMPO4.

Sputtered Porous Li-Fe-P-O Film Cathodes Prepared by Radio Frequency Sputtering for Li-ion Microbatteries

The increasing demands from micro-power applications call for the development of the electrode materials for Li-ion microbatteries using thin-film technology. Porous Olivine-type LiFePO₄ (LFP) and NASICON-type Li₃Fe₂(PO₄)₃ have been successfully fabricated by radio frequency (RF) sputtering and post-annealing treatments of LFP thin films. The microstructures of the LFP films were characterized by X-ray diffraction and scanning electron microscopy. The electrochemical performances of the LFP films were evaluated by cyclic voltammetry and galvanostatic charge-discharge measurements. The deposited and annealed thin film electrodes were tested as cathodes for Li-ion microbatteries. It was found that the electrochemical performance of the deposited films depends strongly on the annealing temperature. The films annealed at 500 °C showed an operating voltage of the porous LFP film about 3.45 V vs. Li/Li⁺ with an areal capacity of 17.9 µAh cm^-2 µm^-1 at C/5 rate after 100 cycles. Porous NASICON-type Li₃Fe₂(PO₄)₃ obtained after annealing at 700 °C delivers the most stable capacity of 22.1 µAh cm^-2 µm^-1 over 100 cycles at C/5 rate, with an operating voltage of 2.8 V vs. Li/Li⁺. The post-annealing treatment of sputtered LFP at 700 °C showed a drastic increase in the electrochemical reactivity of the thin film cathodes vs. Li⁺, leading to areal capacity ~9 times higher than as-deposited film (~27 vs. ~3 µAh cm^-2 µm^-1) at C/10 rate.

30 Years of Lithium-Ion Batteries

Over the past 30 years, significant commercial and academic progress has been made on Li-based battery technologies. From the early Li-metal anode iterations to the current commercial Li-ion batteries (LIBs), the story of the Li-based battery is full of breakthroughs and back tracing steps. This review will discuss the main roles of material science in the development of LIBs. As LIB research progresses and the materials of interest change, different emphases on the different subdisciplines of material science are placed. Early works on LIBs focus more on solid state physics whereas near the end of the 20th century, researchers began to focus more on the morphological aspects (surface coating, porosity, size, and shape) of electrode materials. While it is easy to point out which specific cathode and anode materials are currently good candidates for the next-generation of batteries, it is difficult to explain exactly why those are chosen. In this review, for the reader a complete developmental story of LIB should be clearly drawn, along with an explanation of the reasons responsible for the various technological shifts. The review will end with a statement of caution for the current modern battery research along with a brief discussion on beyond lithium-ion battery chemistries.

Porous NASICON-Type Li3Fe2(PO4)3 Thin Film Deposited by RF Sputtering as Cathode Material for Li-Ion Microbatteries

We report the electrochemical performance of porous NASICON-type Li3Fe2(PO4)3 thin films to be used as a cathode for Li-ion microbatteries. Crystalline porous NASICON-type Li3Fe2(PO4)3 layers were obtained by radio frequency sputtering with an annealing treatment. The thin films were characterized by XRD, SEM, and electrochemical techniques. The chronoamperometry experiments showed that a discharge capacity of 88 mAhg(-1) (23 μAhcm(-2)) is attained for the first cycle at C/10 to reach 65 mAhg(-1) (17 μAhcm(-2)) after 10 cycles with a good stability over 40 cycles.

In-depth mesocrystal formation analysis of microwave-assisted synthesis of LiMnPO4 nanostructures in organic solution

Formation of LiMnPO₄ mesocrystals via self-assembled subunits employing microwave-assisted synthesis in rac-1-phenylethanol.

Supersaturation-induced hydrothermal formation of α-CaSO4·0.5H2O whiskers

Supersaturation-induced fast transformation from CaSO₄·2H₂O to α-CaSO₄·0.5H₂O was observed and the process followed the dissolution–precipitation and homogeneous nucleation mechanism according to classical nucleation theory.

Porous micro-spherical LiFePO4/CNT nanocomposite for high-performance Li-ion battery cathode material

Although many routes have been developed that can efficiently improve the electrochemical performance of LiFePO₄ cathodes, few of them meet the urgent industrial requirements of large-scale production, low cost and excellent performance.

Facile synthesis of nanostructured LiMnPO4 as a high-performance cathode material with long cycle life and superior rate capability

Nano-LiMnPO₄/C exhibits superior rate capability and long cycling stability, sustaining stable cycling over 500 cycles at 10C.

Li3V2(PO4)3 particles embedded in porous N-doped carbon as high-rate and long-life cathode material for Li-ion batteries

The porous N-doped carbon stabilized Li₃V₂(PO₄)₃ particles are obtained by using a modified sol–gel method, and the composite exhibits a high discharge capacity of 114.7 mA h g⁻¹ at 1 C in the voltage range of 3–4.3 V after 600 cycles.

Application of biogenic iron phosphate for lithium-ion batteries

Biogenic iron(ii) phosphate and microbially derived lithium iron phosphate spherical microparticles consisting of nanosheets produced by iron-reducing bacteria were investigated for application in lithium-ion batteries.

Rational design of atomic-layer-deposited LiFePO4 as a high-performance cathode for lithium-ion batteries

Atomic layer deposition is successfully applied to synthesize lithium iron phosphate in a layer-by-layer manner by using self-limiting surface reactions. The lithium iron phosphate exhibits high power density, excellent rate capability, and ultra-long lifetime, showing great potential for vehicular lithium batteries and 3D all-solid-state microbatteries.

Architectures of tavorite LiFe(PO4)(OH)(0.5)F(0.5) hierarchical microspheres and their lithium storage properties

Tavorite LiFe(PO4)(OH)0.5F0.5 microspheres with different morphologies were prepared by a facile solvothermal route, and were further investigated as cathode materials for Li-ion batteries. We highly expect that this research can provide a useful fundamental understanding of the shape-dependent electrochemical performance of tavorite electrode materials.