Carbon Fluoride Research Articles

Direct regeneration of LiFePO4 cathode by inherent impurities in spent lithium-ion batteries

The direct regeneration method, recognized for its cost-effectiveness, has garnered considerable attentions in the field of battery recycling. In this study, a novel direct regeneration strategy is proposed to repair spent LiFePO4 (S-LFP) cathodes without the need for impurity removal. Instead, the residual conductive carbon and polyvinylidene fluoride (PVDF) in S-LFP are employed as inherent reductive agents. Systematic characterization and analysis reveal that the failure of S-LFP primarily originates from a substantial loss of Li+ and the conversion of LiFePO4 to FePO4. Meanwhile, it is demonstrated that both residual conductive carbon and PVDF play positive roles in promoting the regeneration of S-LFP through distinct mechanisms. As a result, the regenerated LFP exhibits significant recovery in crystal structure and chemical composition as compared to S-LFP, which leads to notably improved lithium storage performance. Furthermore, to further enhance the lithium storage property, a specific amount of glucose (10 %) is introduced during the regeneration of S-LFP, yielding a regenerated product that performs comparably to commercial LFP. Clearly, our approach, in contrast to traditional regeneration methods, maximizes the utilization of residual impurities within S-LFP, resulting in effective regeneration of S-LFP, thereby proving both informative and cost-effective.

Enable Rechargeable Carbon Fluoride Batteries with Unprecedented High Rate and Long Life by Oxygen Doping and Electrolyte Formulation.

Here, a rechargeable carbon fluoride battery is demonstrated with unprecedented high rate and long life by oxygen doping and electrolyte formulation. The introductions of Mn2+-O catalyst and porous structure during the oxidation process of CFx cathode can promote the splitting of Li-F during charging. By further modulating the electrolyte with triphenylantimony chloride (TSbCl) as anion acceptor and CsF as product modulator, the more readily dissociable CsLiF2 product instead of LiF is preferentially formed, and the TSbCl-salt protection interface is constructed to confine Li-F based products and reduce fluoride loss at cathode side. These effects endow Li-CFx batteries with durable reversible conversion reaction (for at least 600 cycles), ultrahigh rate performance (e.g., 364 mAhg-1 at 20 Ag-1) and low charging plateau voltage down to 3.2V. The cathode exhibits the maximum power density of 38342Wkg-1 and energy density of 1012Whkg-1. Furthermore, this Li-CFx system demonstrates the promising prospects for applications in view of its low temperature operation (e.g., 280 mAhg-1 at -20°C), low self-discharge ability, large-scale pouch cell fabrication and high cathode loading (5-6mgcm-2), enabling it to move beyond previous role as primary battery and into new role as fast-charging rechargeable battery with high energy density.

A self fire-extinguishing and high rate lithium-fluorinated carbon battery realized by ethoxy (pentafluoro) cyclotriphosphazene electrolyte additive design

The lithium/carbon fluoride (Li/CFx) battery has attracted significant attention due to its highest energy density among all commercially available lithium primary batteries. However, its high energy density also poses a significant risk during thermal runaway events, and its poor electrochemical performance at high discharge current densities limits its application in high-power devices. In this study, we propose a flame-retardant and interface-affinity enhancing electrolyte additive, ethoxy (pentafluoro) cyclotriphosphazene (PFPN), to regulate the electrolyte in Li/CFx batteries. The PFPN molecules participate in the lithium solvation shell, and its fluorine groups shows better affinity with the carbon fluoride cathode compared to traditional carbonate electrolytes. Furthermore, as a bulky molecule, PFPN reduces the desolvation energy of Li+ ions after participating in lithium ion coordination, making it easier for Li+ ions to be utilized at the carbon fluoride cathode, significantly enhancing the battery's rate performance. In a carbonate electrolyte containing 16 % PFPN additive (1 M LiBF4/EC+DMC, volume ratio 1:1), the CFx cathode delivers 277 % higher capacity at a current density of 1 A g−1 compared to a CFx cathode without the additive. Additionally, due to the ability of PFPN to produce fluorine and phosphorus radicals at high temperatures that interrupt the combustion chain reaction, the electrolyte can achieve up to 10 instances of zero-second self-extinguishing, reducing the battery self-extinguishing time by 90 %. This study is the first to investigate the safety and flame-retardant electrolyte design of carbon fluoride batteries, providing a method to improve the power performance and safety of Li/CFx batteries at the same time.

Reversible storage of tetraethyl ammonium cation in CFx-based cathode

Carbon fluorides (CFx) are considered as the potential cation storage materials in alkali metal-based battery systems because of the high theoretical specific capacity (865 mAh g-1 when x = 1). However, the reversibility of cathode reaction is seriously disturbed by the strong metal-fluorine interactions among the electrode products (e.g., LiF). By contrast, the relatively weak N-F bond makes the CFx-based battery system using quaternary ammonium cation (QAA+) a promising alternate, but the electrode mechanism between CFx and QAA+is little understood yet. In this work, tetraethylammonium cation (TEA+) is employed as the charge carrier using the electrolyte solution of sulfolane (SL) for CFx cathode. The CF0.56 electrode exports 710 mAh g-1 during the initial TEA+-CF reaction, and the electrode product (TEAF) can be decomposed under elevated potential that yields amorphous carbon fluoride and a reversible capacity of ∼300 mAh g-1 can be reached in the subsequent galvanostatic charge-discharge cycles. The TEAF product is non-crystallizable that exists in a sticky form on the surface of electrode, which contributes to an improved electrode structural stability while also leads to an unsatisfactory performance of the amorphous carbon fluoride with large number of superficial active sites. The electrode mechanism and the mechanical property of electrode interface are discussed in depth by in-situ Raman and electrochemical quartz crystal microbalance (EQCM) methods.

Design and Reaction Mechanism of Rechargeable Lithium-Carbon Fluoride Battery.

Recharging primary batteries is of great importance for increasing the energy density of energy storage systems to power electric aircraft and beyond. Carbon fluoride (CFx) cathodes are characterized by high specific capacity and energy density (865 mAh g-1 and 2180 Wh kg-1, respectively). Preventing the crystallization of LiF with an intermediate and lowering the energy barrier from LiF to CFx is expected to render the Li/CFx battery reversible. In this study, taking the advantage of a high-voltage-stable all-fluorinated electrolyte containing the boron-based anion receptor tris(trimethylsilyl)borate (TMSB), a rechargeable Li/CFx battery was realized with a reversible capacity of 465.9 mAh g-1 and an energy density of 1183.9 Wh kg-1, approximately 53% of that in the first discharge. After the first discharge, the charge-discharge profile featured rechargeable characteristics. In situ X-ray diffraction, ex situ soft X-ray absorption spectroscopy, pair distribution function analysis, and other measurements confirmed the generation and decomposition of Li-F and C-F bonds during cycling. Density functional theory calculations and nuclear magnetic resonance spectroscopy confirmed that TMSB serves as an anion carrier through the generation of a [TMSB-F]- complex, facilitating the conversion reactions during cycling. This study demonstrated a facile and low-cost approach for realizing high-energy-density, reversible Li/CFx batteries.

The Role of Surface Oxygen in Eliminating Fluorine Impurities and Relithiation Towards Direct Cathode Recycling

Recycling materials back to supply chain not only mitigates the shortage of critical materials such as the metals of Li, Ni, Co, etc, but also protects global environment. Direct recycling of lithium nickel manganese cobalt oxides (NMC) mainly relies on a relithiation process based on purified spent NMC cathode materials. How to efficiently get rid of chemically bonded surface impurities on spent NMC and obtain a clean surface is critical for relithiation. One of the unavoidable impurities is fluorine, which exists in the form of either carbon fluoride (CFx) or metal fluoride (M-F) and can be eliminated by either thermal treatment or hydrothermal procedure under alkaline environments depending on the state of the F.1,2 Generally the hydrothermal method needs relative high temperature (> 200 °C ) and long reaction time (> 16 hours) due to the slow kinetics. A redox mediator such as H2O2, ethanol or ethylene glycol has been reported to be effective to lower the temperature and pressure for relithiation of recycled NMC111 and NMC622, which was pretreated with N-Methyl-2-pyrrolidone solvent.3 However the mechanism is still not fully understood.This work combines material characterizations and electrochemistry and density functional theory (DFT) calculations to study the role of surface oxygen in eliminating fluorine species on recycled NMC532 cathode material. The recycled NMC532 powders were separated from graphite by froth flotation method and there were significant amount of fluorine impurity species on the surface confirmed by XPS. Initial trial of the addition of small amount of H2O2 additive to LiOH aqueous solution during the hydrothermal process was able to decrease the reaction time significantly to fully eliminate both CFx and M-F species compared to the reaction without H2O2. Further calcination steps with the addition of 5% excessive lithium source using LiOH successfully recovered the recycled NMC532 and the half coin cell using the rejuvenated cathode materials shows a discharge capacity of 154 mAh/g at 0.2 C within 2.7 to 4.2 V voltage range. DFT calculations was conducted on a NMC (012) surface and both lithium hydroxide and sodium hydroxide were selected to understand the role of OH- group and surface oxygen species. The kinetics study was conducted with transition state theory4 and the activation energy barriers were calculated by climbing image nudged elastic band (cNEB) method.5,6 The removal of surface F- takes place with the displacement of F- with OH- (*-(M)F(s) +XOH(s) à XF(s) + *-(M)OH(s), X= Li, Na). F- displacement reactions require more than one basic molecule per F- removal with the formation of either LiF or NaF, which is soluble in water and can be removed by a filtration process. Depending on the surface ‘foreign’ oxygen species, the reaction can either go with a hydroxide pathway or a peroxide pathway, with the latter involving the formation of a peroxide intermediate with a ‘foreign’ oxygen atom leading to much smaller barrier energy compared to that in the hydroxide pathway. On a delithiated surface, the barrier energy for F- removal is predicted to be higher than pristine surfaces as the delithiated surface is less reactive to bind ‘foreign’ oxygen. This is consistent with the experimental results in which the additive of H2O2 can provide ‘foreign’ oxygen atoms and favors peroxide pathway leading to shorter time to remove surface fluorine. Additionally, the reaction with NaOH has a lower barrier than that with LiOH for the removal of fluoride species. Future work will investigate alternative additives as well as fluorine surface-bulk transfer which potentially happen if small amount of fluorine residues exist during calcination step.

Kinetic, gas emission, reaction pathway and interaction mechanism analysis during oxidative pyrolysis of aluminium electrolysis waste with beech wood

The oxidative pyrolysis kinetic, gas emission, reaction pathway and interaction mechanism during oxidative pyrolysis of spent cathode carbon block (SCCB) and beech wood (BW) were investigated via the thermogravimetry combined with Fourier transform infrared spectrometer (TG-FTIR) analysis. The hemicellulose, cellulose, and lignin in BW and the carbon materials and fluoride in SCCB were determined as the main five components based on thermogravimetric experiment. Compared with pure SCCB, the addition of BW increased the comprehensive oxidative pyrolysis index. Furthermore, the total of 44 kinetic parameters were obtained by the Shuffled Complex Evolution (SCE) method, which were used to further forecast the mass loss of the above five main components. The evolved gases were detected by FTIR, and the results indicated that the main gases for BW/SCCB oxidative pyrolysis were CO2, which corresponded to the oxidation of cellulose, lignin and carbon materials. Small amounts of phenols, alcohols, ethers, ketones, aldehydes, carboxylic acids, CO, aromatics, alkene were attributed to the thermal decomposition of hemicellulose and cellulose. Pyrolysis of cellulose and lignin produced small quantities of hydrocarbons. HF was formed by the thermal decomposition of fluoride. Eventually, the reaction pathway was proposed and the possible interaction mechanism was analyzed during the oxidative pyrolysis of BW/SCCB blends.

Embedded sensors for in situ measuring and safety warning in lithium carbon fluorides batteries

Lithium/carbon fluoride (Li/CFx) batteries are highly favored for ultra-high specific energy systems due to their attractive features. However, the significant heat generation poses serious risks including thermal runaway, illustrating the critical need of real-time monitoring during battery operation. Currently, fewer studies have focused on the development of sensors for Li/CFx batteries, especially on the compatibility with embedded sensors. Here, two types of embedded sensors are employed to achieve detection and safety warning. The internal temperature of the Li/CFx battery rises by 8.42 °C at a current rate of 0.1C. Additionally, the embedded atmospheric pressure sensors provide a safety warning with a safety threshold of 0.43 kPa/cm2 before the first destructive venting. Consequently, this nondestructive detection and warning can significantly enhance the safety measures for Li/CFx batteries.

Improvement of the electrochemical properties of Li/CFx primary batteries induced by Nitrogen plasma treatment from silica and carbon fluoride

Improvement of the electrochemical properties of Li/CFx primary batteries induced by Nitrogen plasma treatment from silica and carbon fluoride

Reconciling electrolyte donicity and polarity for lithium carbon fluoride batteries

For nonaqueous electrolytes designed for carbon fluoride batteries, a higher donicity is beneficial for stabilizing positively charged carbon atoms, while a moderate polarity is favorable for detaching negatively charged fluorine atoms.

Molecular aggregation state and electrochemical performance of mesophase pitch fluoride

Lithium/carbon fluoride batteries utilizing carbon fluoride as the cathode material have the highest energy density among primary batteries. However, the demanding synthesis conditions for carbon fluoride result in high-production costs, which hinders the widespread adoption of lithium/carbon fluoride batteries. Mesophase pitch fluoride, which exhibits microstructures similar to those of carbon fluoride, has the potential to be used as a low-cost cathode material. In this study, a facile low-temperature fluorination method was employed to synthesize a mesophase pitch fluoride with a high F/C ratio. Solvent-induced dipolar coupling was employed to segregate the mesophase pitch fluoride selectively into two distinct aggregated states with varying structures. When employed as a cathode material for lithium primary batteries, the ordered microcrystalline structure of the mesophase pitch fluoride exhibited a discharge capacity of 743 mA h g−1. Furthermore, it exhibited electrochemical behaviors that were distinguishable from those of conventional carbon fluoride materials. This study introduces a novel research perspective for exploring the viability of low-cost fluorinated pitches in the energy storage domain.

Electrolyte Engineering Empowers Li||CFx Batteries to Achieve High Energy Density and Low Self‐Discharge at Harsh Conditions

AbstractGiven its exceptional theoretical energy density (over 2000 Wh kg−1), lithium||carbon fluoride (Li||CFx) battery has garnered global attention. N‐methylpyrrolidone (NMP)‐based electrolyte is regarded as one promising candidate for tremendously enhancing the energy density of Li||CFx battery, provided self‐discharge challenges can be resolved. This study successfully achieves a low self‐discharge (LSD) and desirable electrochemical performance in Li||CFx batteries at high temperatures by utilizing NMP as the solvent and incorporating additional ingredients, including vinylene carbonate additive, as well as the dual‐salt systems formed by LiBF4 with three different Li salts, namely lithium bis(oxalato)borate, lithium difluoro(oxalato)borate, and LiNO3. The experimental results unfold that the proposed methods not only minimize aluminum current collector corrosion, but also effectively passivate the Li metal anode. Among them, LiNO3 exhibits the most pronounced effect that achieves an energy density of ≈2400 Wh kg−1 at a current density of 10 mA g−1 at 30 °C, nearly 0% capacity‐fade rate after 300 h of storage at 60 °C, and the capability to maintain a stable open‐circuit voltage over 4000 h. This work provides a distinctive perspective on how to realize both high energy density and LSD rates at high temperature of Li||CFx battery.

S, N co-doped carbon material functionalized catalytic membrane for efficient peroxymonosulfate activation and continuous refractory pollutants flow-treatment

Peroxymonosulfate (PMS) coupled with membrane technology shows great potential for refractory pollutants treatment. A simple method was developed to construct a highly efficient catalytic system consisting of S, N co-doped porous carbon (SNC) and polyvinylidene fluoride (PVDF) catalytic membrane. The degradation efficiency of tetracycline hydrochloride achieved a minimum of 91 %. The introduction of N and S dopants improved the defect density of the catalytic membrane, with graphite-N promoting PMS activation to generate 1O2, and thiophene S might be consumed or converted into oxidation-S as an active site during TC degradation. Loading SNC onto the PVDF membrane significantly enhanced its anti-pollution performance. The SNC/PVDF active catalytic membrane exhibited excellent degradation performance for various pollutants, maintaining an efficiency of approximately 80 % even after continuous degradation for 360 min. This work presents a novel catalytic membrane design that offers a promising approach to effectively treat refractory pollutants in wastewater.

Preparation of High‐Power Lithium Fluoride Carbon Battery via Microstructural Modulation of Ketjen Black

Ketjen black fluoride (KBF‐2) material, a novel carbon fluoride cathode nanomaterial, is fabricated through a pregrinding treatment followed by a fluorination process for lithium primary batteries. The ketjen black material as the carbon precursors provides a 3D spherical structure with a high‐specific surface area. In addition, the pregrinding treatment results in several cracks in the spherical KBF‐2 particles. The effects of cracks on the fluorine content ratio under the same fluorination process conditions, diffusion coefficient of lithium ions, rate performance, and power density performance are investigated. At an extremely high current density of 4.5 A g−1(at a 6 C rate), the discharge capacity retention is 52.09%, which is a breakthrough for the series of fluoride cathode materials. Moreover, the KBF‐2 cathode is evaluated in a 10 Ah KBF‐2/Li primary pouch cell and demonstrated a high gravimetric energy density of 573.70 Wh kg−1 at a 0.5 C rate, and the discharge duration time reached 624 s under a constant specific power of 1,500 W kg−1. These factors contribute to the remarkable energy density performance and power output stability, particularly at high current densities.

Electrochemical impedance spectroscopy analysis for lithium carbon fluorides primary battery

The impedance response of Li/CFx pouch cells are measured within a frequency range of 0.1 Hz-100 kHz using a three-electrode cell, which allows to separate the processes of cathode and anode. The measured impedance is interpreted with an equivalent circuit. The impedances are measured at various state of charge (SoC) and after storage at different temperature, indicating that lithium anode dominates the impedance of the whole pouch cell. The frequency value of the onset between the semicircle and the sloped line is an effective parameter to distinguish the electrochemical behavior of Li/CFx pouch cell, especially the power characteristic. These results show that electrochemical impedance spectroscopy is a potential nondestructive method to investigate primary batteries, and suggest that the stability lithium anode is important during storage.

Insights of the Ultralow Wear and Low Friction of Carbon Fiber Reinforced PTFE in Inert Trace Moisture Environment

Ultralow wear rates and low friction have been observed for carbon fiber reinforced PTFE (CF/PTFE) when sliding against steel or cast iron in dry gas environments. Although the strong environmental sensitivity of this tribosystem is well known, the origin of the outstanding tribological performance in dry gas remains unanswered. Some researchers attribute the low friction and wear to the formation of carbon-rich surfaces in the absence of oxygen and moisture in the environment. However, low friction between carbon surfaces is generally dependent on moisture. In this paper, extensive analyzes are conducted on the tribofilms formed on the CF/PTFE surface and the steel counterface after sliding in a high-purity nitrogen environment. TEM analysis of a cross-section of the tribofilm on the steel surface reveals that the sliding surface consists mainly of iron (II) fluoride and not carbon, even though a significant amount of carbon was observed near the surface. XPS and TEM analysis further revealed that the tribofilm formed on the worn composite surface consisted of nanoparticle agglomerates, anchored to the PTFE matrix and to each other by carbon with turbostratic structure. Turbostratic carbon also formed an ultrathin and surface-oriented superficial layer on top of the agglomerates. Governing mechanisms of the low friction and wear of the CF/PTFE—steel tribosystem were investigated by complementary tribotests with pure graphite samples and MD simulations of the identified surfaces. These indicated that the low friction between the carbon and iron fluoride in the tribofilms is due to poor adhesion between the distinctly different surfaces.Graphical

Impact of Disorder and Defects on Bond Energies in Highly Fluorinated Graphene

Fluorinated graphite materials are of interest for an assortment of applications and can be synthesized under a variety of synthetic conditions from many different types of carbon. Due to such variations, structural disorders in the form of defects and polymorphism are often present. Here, we investigate the impact of local structural variations on the C–F bond dissociation energies (BDEs) in carbon-based fluoride materials using density functional theory (DFT) computational methods. Employing fluorographene (FG) cluster models, we determine the impact of different C–F bonding configurations in the core of each platelet on the equilibrium BDEs for each C–F bond. The introduction of structural disorder decreases the first C–F BDE by approximately 1 eV compared to the canonical arrangement of axial C–F bonds ordered as in a network of cyclohexane “chairs”. Variability of calculated BDEs among the different polymorphs decreases upon subsequent F removal. Common structural tendencies of the adiabatic defluorination pathways for each polymorph are identified. Our analysis suggests that at F/C ratios near 1.0, disorder in the local structure can play a significant role in the energetics of the initial carbon fluoride defluorination and that the influence of this configurational disorder diminishes with decreasing F/C ratios.

High-Energy and High-Power Primary Li-CFx Batteries Enabled by the Combined Effects of the Binder and the Electrolyte

Several effective methods have been developed recently to demonstrate simultaneous high energy and high power density in Lithium - carbon fluoride (Li-CFx) batteries. These methods can achieve as high as a 1000 Wh/kg energy density at a 60–70 kW/kg power density (40–50 C rate) in coin cells and a 750 Wh/kg energy density at a 12.5 kW/kg power density (20 C rate) in pouch cells. This performance is made possible by an ingenious nano-architecture design, controlled porosity, boron doping, and electrolyte additives. In the present study, we show that a similarly great performance, a 931 Wh/kg energy density at a 59 kW/kg power density, can be achieved by using a polyacrylonitrile binder and a LiBF4 electrolyte in Li-graphite fluoride coin cells. We also demonstrate that the observed effect is the result of the right combination of the binder and the electrolyte. We propose that the mechanistic origin of the observed phenomena is an electro-catalytic effect of the polyacrylonitrile binder. While our proposed method has a competitive performance, it also offers a simple implementation and a scalable production of high-energy and high-power primary Li-CFx cells.

Fluorinated microporous carbon spheres for Li/CFx batteries with high volumetric energy density

Carbon fluorides (CFx) have the highest theoretical energy density among current cathode materials for lithium primary battery. Although fluorinated graphite (FG) has been successfully commercialized, its energy density is difficult to meet the continuously increasing demand. In this study, porous carbon spheres are prepared as starting materials to obtain a new type of CFx compound with improved electrochemical performance. The fluorinated microporous carbon spheres (FMCSs) with a high fluorinated degree achieve a comparable specific capacity as that of the commercial FG. The spherical morphology and hierarchically porous structure prompt the diffusion of Li+ and the reaction with fluorinated active sites. The FMCSs fluorinated at 250 °C deliver a specific capacity of 955 mAh g−1 and a maximum energy density of 2428 Wh kg−1, and could operate stably at discharge rate as high as 10C. Unlike nanostructured CFx, the desirable true density of FMCSs enable their practical applications without sacrificing the volumetric energy density. Therefore, the assembled pouch cell using FMCSs as the cathode material exhibits superior electrochemical performance. In particular, the alleviated volume expansion and heat release further promoted the applicability of FMCSs and strengthen their capability as a favorable alternative to commercial FG.

Size-tunable graphitized carbon spheres for water defluoridation

We fabricated non-catalytic carbon spheres with controllable dimensions (diameter 0.3–1.5 µm) by chemical vapour deposition at 1273 K using C2H2 (carbon source) and N2 (dilutant) gas precursors. By varying the flow rates of precursor gases, spherical or pseudo-spherical morphologies with chain-like hierarchical structures are discerned. The X-ray diffraction data show hexagonally graphitized networks. The mechanism of carbon sphere formation is not yet fully resolved largely due to the ambiguity associated with the nucleation step, viz. pentagon or heptagon route. According to molecular dynamics calculations, the formation of carbon pentagons is energetically more favorable than heptagons. Pentagon structures seem to form by closing Fjord regions of the graphitized network as evidenced in IR bands at 635 cm−1 and 796 cm−1. The X-ray photon spectroscopic (XPS) measurements show adventitious oxygen on the carbon sphere’s surface sites with -COOH and -C-CO groups. The -COOH and -C-CO groups are polar; hence, the carbon spheres’ surface sites readily hydroxylate (where ≡GOHδ represents surface sites with a fractional charge). The carbon sphere synthesized under C2H2N2 = 56 gas flow ratio (viz., CS3) shows the highest fluoride removal capacity, viz., 0.095 ± 0.01 mmol.m2-. The comparable zeta potential values observed between the carbon spheres and fluoride laden carbon spheres point to an anion exchange of surface hydroxyl ions for F- sorption. In agreement with the XPS data, the broad IR band at 3440 cm−1 due to H-bonded surface hydroxyl stretching vibrations has resolved into three discrete bands, e.g., 3640, 3752, and 3738 cm−1, which evidenced fluoride adsorption. Compared to activated carbon, the retention of fluoride on carbon spheres is over 60 times higher, which shows its potential in water treatment in removing fluoride.