Papers by Keyword: LiFePO₄

Abstract: LiFe(P,Si)O₄ is a material that belong to parent compound of LiFePO₄ widely known as cathode material for lithium-ion battery (LIB). Previous study reports that electrochemical performance of LiFePO₄ can be improved by silicon (Si) substitution to the phosphorus (P) site. The sample was obtained via a solid-state synthesis route with the amount of Si doping to the P site is ∼3%. The electrochemical performance of silicon substituted LiFePO₄ has been widely studied in other report whilst the magnetic properties is still less explored. Here we investigate the magnetic properties of LiFe(P,Si)O₄ using superconducting quantum interference device (SQUID) and muon spin relaxation (µSR). The two measurements display a good agreement result showing two anomalies at the temperature of ∼27 K and ∼52 K that represent the Neel Temperature (Τ_N) of Li₂FeSiO₄ and LiFePO₄, respectively. The presence of Li₂FeSiO₄ that is also a candidate of cathode of LIB has been confirmed by X-ray Diffraction (XRD). Based on the current study, there is no alteration of Τ_N on LiFePO₄ phase due to Si doping.

Abstract: Lithium iron phosphate (LiFePO₄) batteries have received much attention because they can provide higher power density with abundant raw materials, better safety, low toxicity, and high thermal stability. In general, the production of LiFePO₄ cathodes uses polyvinylidene fluoride (PVDF) as a binder and N-methyl-2-pyrrolidone (NMP) as a solvent. These components are expensive, toxic, and can adversely affect the environment. Therefore, to address these shortcomings, the solvent and binder were replaced in this study. The solvent in the current study is water. The water soluble binders employed in this study are carboxymethyl cellulose (CMC) and styrene-butadiene rubber (SBR). Suitable electrode formulations were investigated to obtain high performance cylindrical Li-ion batteries. As a result, a formulation with a ratio of LiFePO₄:AB:KS6:SBR:CMC equal to 90:3:3:2.677:1.333 was used. It has a high specific discharge capacity, 120 mAh/g. This NMP-based cathode can yield about 145 mAh/g, which is slightly higher than a water-based LiFePO₄ cathode.

Abstract: Lathe waste is one of the wastes products of metal processing in the metal-turning industry. The most content of lathe waste is a ferrous (Fe) metal, which, if disposed of into the environment, can cause environmental pollution. Fe metal from lathe waste can be used as a Fe precursor in LiFePO₄ synthesis. The extraction of Fe from the lathe waste can be done by the leaching method using acid as the leaching agent. The recovered compounds have great potential to be used as Fe precursors for the LiFePO₄ synthesis. The selection of leaching agent was based on considerations of the price, the effectiveness of Fe extraction, and the advanced recovery process from Fe extraction. The LiFePO₄ synthesis process can be carried out using co-precipitation, hydrothermal, and sol-gel. LiFePO₄ material characterization was carried out to test the yield of the material produced. Synthesized materials were done to test the characteristics by Scanning Electron Microscopy (SEM) and X-Ray Diffractometer (XRD) analysis. SEM analysis aims to describe the shape and particle size of the material in three dimensions. Meanwhile, XRD analysis aims to characterize the material's crystal structure and crystal size by using the Lattice Parameter value. The electrochemical test aims to test electrochemistry to test the capacity of charge/discharge, efficiency, and lithium-ion batteries' stability. The resulting battery capacity from the three methods is close to the theoretical capacity of LiFePO₄, which is 170 mAh/g.

Abstract: Lithium ion batteries with LiFePO₄ cathode have become the focus of research because they are eco-friendly, stable, high average voltage (3.5 V), and high theoretical capacity (170 mAh/g). However, LiFePO₄ has disadvantages such as low electrical conductivity (~10^-9 S/cm) and low lithium ion diffusion coefficient (~10^-14-10^-15 cm²/s) that can inhibit its application as a lithium ion battery cathode material. To increase the electronic conductivity of LiFePO₄, it can be done by adding carbon as a coating material, then doping gadolinium metal ions because it has a radius similar to Fe, and increasing sintering temperature. Optimizing the sintering temperature can control particle growth and research was study the sintering temperature of the electronic conductivity of LiFeGdPO₄/C and obtain the optimum sintering temperature at LiFeGdPO₄/C. The carbothermal reduction method used in synthesis, with a variation of sintering temperature of 800°C, 830°C, 850°C, 870°C, and 900°C using reagents LiH₂PO₄, Fe₂O₃, Gd₂O₃, and carbon black. Furthermore the samples were characterized using XRD, SEM-EDS, and four-point probes. The results of the study were expected to increase the conductivity of LiFePO₄. The results show the effect of sintering temperature can increase the electronic conductivity of LiFeGdPO₄/C. Samples with a sintering temperature 850°C have the highest conductivity among all temperature variations with a value of 1.11 × 10^-5 S cm^-1.

Abstract: Olivine-type LiFePO₄ is widely considered as a cathode for lithium-ion batteries owing to its environmental friendliness and low-cost, yet its applicability in the pristine state is limited due to poor electronic and ionic conductivity. To investigate the conductivity enhancement of LiFePO₄, first-principles method under the GGA+U framework is implemented to study effects of doping with Ti⁴⁺ at Fe²⁺ sites under the lithium-deficient environment. LiFePO₄ crystal and electronic structures as well as conductivity are investigated. Ti doping creates the impurity states at the acceptor level, which are normally degenerate states, but split into multiple states by the crystal field splitting. Doping under the lithium-deficient environment induces small hole polarons localizing at the Fe atoms and creates defect states located in the intermediate band. Both phenomena combine to facilitate charge carrier hopping. The climbing-image nudge elastic band (cNEB) calculation shows that Li hopping can be promoted by doping with high Ti concentration. This co-doping mechanism therefore can enhance both the electronic and ionic conductivities, which can be beneficial benchmark for cathode-material synthesis in the future.

Abstract: In the recent years, LiFePO₄ has been widely developed as a cathode for lithium ion batteries because it has high theoretical capacity (170 mAh/g), good stability and is also environmentally friendly. However, the poor electronic conductivity (~10^-9 S/cm) and low diffusion coefficient of lithium ion (~10^-15-10^-14 cm²/s) are limiting its application. Some solutions to overcome this problem are carbon coating and doping metal ions. This study aims to determine the effect of Gd³⁺ ion doping on the electronic conductivity of LiFePO₄/C. The synthesis method was used is carbothermal reduction with Fe₂O₃, Gd₂O₃, LiH₂PO₄ and carbon black reagents. The synthesized LiFe_1-xGd_xPO₄/C was characterized using XRD, SEM-EDS, and four point probes. The results obtained showed that gadolinium ion doping increased the conductivity of LiFePO₄/C from 1.8952 x10^-6 to 8.69x10^-6 Scm^-1 using 0.07 mol ion Gd³⁺.

Abstract: In this study, cathode and lithium-ion conducting solid electrolyte composite pellet with 1:1 wt. % composition of LiFePO₄ and Li_7-3XGa_xLa₃Zr₂O₁₂ (x = 0.1) (LiFePO₄|Ga-LLZO) was prepared via solid-state reaction. The aim of the study is to investigate the phase stability between LiFePO₄ cathode and Ga-LLZO solid electrolyte material when heat treated at 400 to 600 °C. The as-mixed LiFePO₄|Ga-LLZO composite was characterized by TG/DTA and the heat treated sample was then analyzed for its structure using XRD and compared to the just as-mixed composite. XRD patterns of the heat treated composite pellet showed that it retains its as-mixed phases of LiFePO₄ and Ga-LLZO when sintered below 500 °C under Ar gas flow environment. However, upon heat treatment at 600 °C, the sample already reacted and decomposed with the formation of other phases.

Abstract: In this study an investigation has been conducted on the effect of reduced graphene oxide (rGO) coating on increasing the value of Lithium Ferro Phosphate (LFP) electrical conductivity. This coating process uses a variation of the mass ratio of LiFePO₄/rGO by 90%:10%, 70%:20%, and 67%:33%. The LiFePO₄ precursor was prepared using the sol-gel rute from the main commercial materials, namely Li₂CO₃ powder as a source of lithium ions, FeCl₂.4H₂O as a source of iron and NH₄H₂PO₄ powder as a phosphate source. As for the coating used rGO extracted from coconut shell waste. The samples were calcined with temperature variations of 600°C, 650°C and 700°C in an argon environment for 10 hour. The phase purity and crystal structure of LiFePO₄ were analyzed using XRD. The analysis of data from XRD was done using the the Match!, Rietica, and MAUD software. Based on the results of XRD analysis, LiFePO₄ with high purity and good crystallinity was obtained when the sample was calcined at temperature of 700°C. The results of the MAUD analysis show that the best size of LiFePO₄ crystal is 86,54 nm. LiFePO₄/rGO nanocomposite was successfully synthesized by mechanical ultracentrifugation method. The characterization of the value of electrical conductivity, carried out using a four-point probe. The results show that the greater the percentage of rGO, the higher the value of electrical conductivity. The mass ratio of 67% LiFePO₄ and 33% rGO shows an increment in good conductivity values, from the original order of 10^-8 S/cm to the order of 10^-4 S/cm.

Abstract: Lithium iron phospate-carbon composite (LiFePO₄/C) was successfully synthesized with various sintering temperature in order to find best synthesis condition resulting high quality of LiFePO₄/C that can be applied for environmentally friendly of cathode in lithium ion battery. It is found that the specific capacity and the stability capacity of LiFePO₄/C were improved to 17.6 mAh and 40.3% of capacity loss, respectively.

Abstract: The cathode materials of LiFePO₄ batteries decreases due to the gradual loss of lithium content during use. In this paper, the spent cathode materials were recycled with a carbon layer coated. The samples were prepared by a high temperature impurity removal procession and a solid phase repairing method. The LiFePO₄ material obtained by the regeneration process has a discharge specific capacity of 105.4 mAh/g at 0.1 C after 10 cycles, and keeps it a considerable retention of 73.1 mAh/g at 1 C. This work provides a new routine in reusing lithium ion batteries.