LiFePO4 Research Articles

High-Power Battery Electrodes Fabricated by Acupuncture-Inspired Microneedle Processing.

Advancing battery electrode performance is essential for high-power applications. Traditional fabrication methods for porous electrodes, while effective, often face challenges of complexity, cost, and environmental impact. Inspired by acupuncture, here we introduce an eco-friendly and cost-effective microneedle process for fabricating lithium iron phosphate electrodes. This technique employs commercial cosmetic microneedle molds to create low-curvature holes on electrode surfaces, significantly enhancing electrolyte infiltration and ion transport kinetics. The punctured electrodes were prepared and characterized, with comparisons to pristine electrodes conducted using scanning electron microscopy, 3D metallurgical microscopy, and detailed electrochemical evaluations. Our results show that the microneedle-processed electrodes exhibit superior rate performance and diffusion properties. Simulations and experimental data reveal that the low-curvature holes reduce Li-ion concentration polarization and improve Li-ion transport within the electrode. This enhancement leads to higher specific capacities and better rate capabilities in the punctured electrodes. The findings highlight the potential of this innovative microneedle technique for large-scale production of high-performance electrodes, offering a promising avenue for the development of high-power-density batteries.

Entangled S-doped LiFePO4 with carbon network for self-supporting cathode of flexible energy storage devices

This paper describes the development of a highly flexible self-supporting cathode incorporating a network of entangled carbon nanofibers (CNFs) and well-dispersed sulfur-doped lithium iron phosphate (SLFP) particles. Through a spin-on-dopant process, sulfur atoms were successfully incorporated into both the surface carbon layer and inner LFP particles. The resulting S-doped carbon@LFP (SLFP-CNF) flexible electrode featured a unique hybrid composite architecture in which the interconnecting CNF framework considerably enhanced both the physical and electrochemical properties. Notably, the SLFP-CNF electrode maintained its structural integrity even after 5000 flexibility cycles, demonstrating robust mechanical stability. The electrode exhibited a high ionic diffusion rate of 9.14 × 10–13 cm²/s, which is attributed to the expanded lattice constant of the S-doped LFP particles, which facilitates favorable Li-ion pathways. This contributes to a high specific capacity of 135.82 mAh/g and superior rate performance of 74.16 mAh/g after 1500 cycles (92.4 % retention rate) at a current density of 2000 mA/g. This enhanced performance is further supported by the conductive S-doped carbon layer, which enables rapid electron transport and ensures excellent cyclability. These results indicate that the SLFP-CNF flexible cathode is a promising candidate for next-generation flexible lithium-ion batteries.

A Room‐Temperature Lithium‐Restocking Strategy for the Direct Reuse of Degraded LiFePO4 Electrodes

The sustainable development of lithium iron phosphate (LFP) batteries calls for efficient recycling technologies for spent LFP (SLFP). Even for the advanced direct material regeneration (DMR) method, multiple steps including separation, regeneration, and electrode refabrication processes are still needed. To circumvent these intricacies, new regeneration methods that allow direct electrode reuse (DER) by rejuvenating SLFP electrodes without damaging its structure are desired. Here, a 0.1 M lithium triethyl borohydride/tetrahydrofuran solution, which has the proper reductive capability to reduce Fe3+ in SLFP to Fe2+ without alloying with the aluminum current collector, is selected as the lithiation/regeneration reagent to restock the Li loss and regenerate SLFP electrodes. By soaking the SLFP electrodes in the lithiation solution, we successfully rejuvenated the crystal structure and electrochemical activity of SLFP electrodes with structural integrity within only 6 minutes at room temperature. When being directly reused, the regenerated LFP electrodes deliver a high specific capacity of 162.6 mAh g‐1 even after being exposed to air for 3 months. The DER strategy presents significant economic and environmental benefits compared with the DMR method. This research provides a timely and innovative solution for recycling spent blade batteries using large‐sized LFP electrodes, boosting the closed‐loop development of LFP batteries.

A Room-Temperature Lithium-Restocking Strategy for the Direct Reuse of Degraded LiFePO4 Electrodes.

The sustainable development of lithium iron phosphate (LFP) batteries calls for efficient recycling technologies for spent LFP (SLFP). Even for the advanced direct material regeneration (DMR) method, multiple steps including separation, regeneration, and electrode refabrication processes are still needed. To circumvent these intricacies, new regeneration methods that allow direct electrode reuse (DER) by rejuvenating SLFP electrodes without damaging its structure are desired. Here, a 0.1 M lithium triethyl borohydride/tetrahydrofuran solution, which has the proper reductive capability to reduce Fe3+ in SLFP to Fe2+ without alloying with the aluminum current collector, is selected as the lithiation/regeneration reagent to restock the Li loss and regenerate SLFP electrodes. By soaking the SLFP electrodes in the lithiation solution, we successfully rejuvenated the crystal structure and electrochemical activity of SLFP electrodes with structural integrity within only 6 minutes at room temperature. When being directly reused, the regenerated LFP electrodes deliver a high specific capacity of 162.6 mAh g-1 even after being exposed to air for 3 months. The DER strategy presents significant economic and environmental benefits compared with the DMR method. This research provides a timely and innovative solution for recycling spent blade batteries using large-sized LFP electrodes, boosting the closed-loop development of LFP batteries.

Improving the Performance of LiFePO4 Cathodes with a Sulfur-Modified Carbon Layer

LiFePO₄ (LFP) cathodes are popular due to their safety and cyclic performance, despite limitations in lithium-ion diffusion and conductivity. These can be improved with carbon coating, but further advancements are possible despite commercial success. In this study, we modified the carbon coating layer using sulfur to enhance the electronic conductivity and stabilize the carbon surface layer via two methods: 1-step and 2-step processes. In the 1-step process, sulfur powder was mixed with cellulose followed by heat treatment to form a coating layer; in the 2-step process, an additional coating layer was applied on top of the carbon coating layer. Electrochemical measurements demonstrated that the 1-step sulfur-modified LFP significantly improved the discharge capacity (~152 mAh·g−1 at 0.5 C rate) and rate capability compared to pristine LFP. Raman analyses indicated that sulfur mixed with a carbon source increases the graphitization of the carbon layer. Although the 2-step sulfur modification did not exceed the 1-step process in enhancing rate capability, it improved the storage characteristics of LFP at high temperatures. The residual sulfur elements apparently protected the surface. These findings confirm that sulfur modification of the carbon layer is effective for improving LFP cathode properties, offering a promising approach to enhance the performance and stability of LFP-based lithium-ion batteries.

Lithium-ion comb—artificial self-regulating lithium-storage film on aluminum anode enabling long cycles of batteries

Al anode can increase battery energy density, but its non-wettability and high Li nucleation hindrance cause uneven Li nucleation to deteriorate the anode structure. Herein, we present a novel in-situ synthesis method for the deposition of molybdenum oxide nanospheres (NMO) onto the surface of Al foil, that is, molybdenum oxide/aluminum (M-Al), which demonstrates a two-stage propulsion effect on Li-ion migration to address the issue at hand. The high wettability and low Li nucleation hindrance of the NMO layer drive the first stage of Li-ion migration. NMO acted as a comb to deliver Li ions uniformly with minor volume expansion. Subsequently, the formation of Li2O-rich solid electrolyte interphase (SEI) film with exceptional desolvation capability, facilitated by the NMO layer and electrochemically activated M-Al to Li molybdate/aluminum (Li-M-Al), represents the second stage in the advancement of Li−ion migration. The embedding of lithium ions makes molybdenum oxide evolve into lithium molybdate, thereby enabling Mo to regulate the storage of Li ions through the valence state. Hence, the Li nucleation overpotential of M-Al is decreased by 0.32 V, leading to a significant enhancement in the cycling performance of the Li-M-Al||LiFePO4 (LFP) battery, with a capacity retention rate of 78.5 % after 400 cycles at 1C.

In Situ-Constructed Multifunctional Composite Anode with Ultralong-Life Toward Advanced Lithium-Metal Batteries.

Metallic lithium is the most competitive anode material for next-generation high-energy batteries. Nevertheless, the extensive volume expansion and uncontrolled Li dendrite growth of lithium metal not only cause potential safety hazards but also lead to low Coulombic efficiency and inferior cycling lifespan for Li metal batteries. Herein, a multifunctional dendrite-free composite anode (Li/SnS2) is proposed through an in situ melt-infusion strategy. In this configuration, the 3D cross-linked porous Li2S/Li22Sn5 framework facilitates the rapid penetration of electrolytes and accommodates the volume expansion during the repeated Li-plating process. Meanwhile, the lithiophilic Li2S phases with a low Li+ transport barrier ensure preferential Li deposition, effectively avoiding uneven electron distribution. Moreover, the Li22Sn5 electron conductors with appropriate Li+ bonding ability guarantee rapid charge transport and mass transfer. Most importantly, the steady multifunctional skeleton with sufficient inner interfaces (Li2S/Li22Sn5) in the whole electrode, not only realizes the redistribution of the localized free electron, contributing to the decomposition of Li clusters, but also induces a planar deposition model, thus restraining the generation of Li dendrites. Consequently, an unprecedented cyclability of over 6500h under an ultrahigh areal capacity of 10mAhcm-2 and a current rate of 20mAcm-2 is achieved for the prepared Li2S/Li22Sn5 composite anode. Moreover, the assembled Li/SnS2||LiFePO4 (LFP) pouch full-cells also demonstrate remarkable rate capability and a convincing cycling lifespan of more than 2000 cycles at 2 C.

Synergistic enhancement of lithium iron phosphate electrochemical performance by organic zinc source doping and crystalline carbon layer capping

In this study, lithium iron phosphate (LFP) is prepared as cathode material by hydrothermal synthesis method and the combined effect of doping and capping is applied to co-modify it. We thoroughly investigate how Zn2+ doping and PA capping layer affect the crystal structure, microscopic morphology, and electrochemical properties of LFP cathode materials. The experimental results show that when co-modified with 5 % Zn2+ doping combined with 7 % PA capping layer, the resulting cathode material exhibits a discharge specific capacity of 165.5 mAh g−1, and the capacity retention rate can still be maintained at a high level of 98.6 % after 200 charge–discharge cycles.

Effect of vanadium doping on electrochemical properties of lithium iron manganese phosphate

Abstract The low-cost lithium iron manganese phosphate anode material has a 15% higher energy density than lithium iron phosphate, and it has received wide attention in recent years. However, the poor electronic/ionic conductivity of lithium ferromanganese phosphate leads to poor power performance, which makes it difficult to meet the needs of practical applications. In this study, a V-doped LiMn0.2Fe0.8PO4(LFMP) material is designed and prepared, and every particle is coated by a uniform carbon layer. The V-doped LFMP material shows better rate performance and cycle performance. When the optimal vanadium doping amount is 0.01, the specific discharge capacity of the material is 164.0 mAh/g at 0.1 C.

In-depth approach and establishment from a structural perspective of LiFePO4 cathodes for lithium-ion batteries by a two-step sintering

Most synthesis of olivine LiFePO4 (LFP) studies have emphasized the importance of a two-step sintering process for the formation of a uniform carbon coating. However, in this study, it is found that, as an advantage of the two-step sintering process, stable carbonization not only improves lithium-ion conductivity by forming a coating layer but also increases the uniformity of the internal crystal structure. In addition to basic crystallinity and structure analysis using X-ray diffraction (XRD), in-depth calculations are performed to explain the formation mechanism of crystal structure according to the two-step sintering process and the temperature of the first sintering step. In particular, lattice defects and structural uniformity are closely investigated from the crystal structure perspective by comparing lattice micro-strain and dislocation density. Improvement in lithium-ion conductivity from structural uniformity is also demonstrated through cyclic voltammetry (CV) analysis. As a result, it is confirmed that LFP, which undergoes a high-temperature two-step sintering, has high capacity and excellent cycle retention at high rates. Furthermore, ex-situ XRD analysis demonstrates the performance difference according to lithium-ion mobility by comparing the LiFePO4/FePO4 two-phase transformation reaction of two-step sintered LFP and the plateau stability during charging.

Analysis of the inhibition effects of C6F12O and low-pressure carbon dioxide on 72 Ah LiFePO4 module under the overcharging abuse condition

Fire disasters that happened in the energy storage station of LiFePO4 (LFP) cells have been growing rapidly in recent years. To meet the urgent need for fire and explosion prevention caused by the abused LFP cells, the application of C6F12O and low-pressure carbon dioxide (LCD) is proposed. The inhibition effects are investigated quasi-quantitatively. While the average mass flow rate of LCD is 4 times higher than that of C6F12O, the economy of LCD far exceeds C6F12O (the quality unit price of C6F12O is about 10 times to LCD). In particular, the suppression time of LCD is 9 times shorter than C6F12O when they were all released at the side of the module box alone. LCD shows extraordinary module cooling ability on the overcharged LFP module. The pure C6F12O application makes it hard to prevent thermal runaway over long durations. The releasing position of C6F12O (directly above the safety valve and on the side of the LFP module) is also tested. It is easier to suppress the flame when C6F12O is released directly above the safety valve. Additionally, the re-ignition is observed due to the electrostatic spark generated by the charging wire during the suppression process.

Research on self-supporting flexible cathode materials with high LFP loading based on PAN in situ inorganic reaction

High loading flexible electrode material is a key component of flexible batteries. This article prepares a flexible electrode by using electrospinning technology that achieves high conductivity and self-supporting without adhesive and current collector. This structural advantage is attributed to the high compatibility and fibrosis of PAN (polyacrylonitrile) and LFP/CNF, which is transformed in situ by precursor conversion method into a flexible self-supporting composite electrode with continuous carbon fiber/CNF as the conductive phase and LFP(LiFePO4) as the lithium storage phase. These flexible materials achieving a specific capacity of 110.5 mAh/g at 0.1C, 92 mAh/g at 0.5C, and 58 mAh/g at 3C, further demonstrated reversible charge and discharge cycles after mechanical bending. These findings highlight the potential of LFP/CNF electrodes for flexible and high-performance energy storage applications.

Li‐ion Exchange‐Driven Interfacial Buffer Layer for All‐Solid‐State Lithium Metal Batteries

AbstractThe goal of achieving batteries with high energy density and high safety profile has been a driving force in developing all‐solid‐state lithium metal batteries (ASSLMBs). However, the complex issues arising from the interfacial interaction between lithium anode/cathode and solid‐state electrolytes (SSE) have hindered the progress of ASSLMBs. This study presents a strategy for constructing an organic/inorganic buffer layer via employing Li‐ion exchanging chemistry of H1.6Mn1.6O4 (HMO) with a flexible matrix of polyethylene oxide (PEO). The buffer layer shows a remarkable ion conductivity of 3.21 × 10−4 S cm−1 at 25 °C originating from the exceptional Li+‐H+ ion exchange capability of HMO. This PEO/HMO buffer layer not only establishes an intimate physical contact between the Li anode/cathode and the SSE but also functions as a dynamic Li+ transfer station to facilitate Li+ movement through the interfaces improving interfacial stability. By pairing with cathodes of LiFePO4 (LFP) and LiNi0.8Co0.1Mn0.1O2 (NCM811), the ASSLMBs feature high‐rate capability and stable cycling performance with low polarization. This marks the utilization of HMO as a superior interfacial material to replace conventional lithium salts, with improved ion transport, decreased polarization, and enhanced overall performances. This constitutes a significant advancement toward the next‐generation energy storage solutions for ASSLMBs.

3-Electrode Setup for the Operando Detection of Side Reactions in Li-Ion Batteries: The Quantification of Released Lattice Oxygen and Transition Metal Ions from NCA

Detecting parasitic side reactions is paramount for developing stable cathode active materials (CAMs) for Li-ion batteries. This study presents a method for the quantification of released lattice oxygen and transition metal ions (TMII+ ions). It is based on a 3-electrode cell design employing a Vulcan carbon-based sense electrode (SE) that is held at a controlled voltage against a partially delithiated lithium iron phosphate (LFP) counter electrode (CE). At this SE, reductive currents can be measured while polarizing a CAM working electrode (WE), here a LiNi0.80Co0.15Al0.05O2 (NCA), against the same LFP CE. In voltammetric scans, we show how the SE potential can be selected to specifically detect a given side reaction during CAM charge/discharge, allowing, e.g., to discriminate between lattice oxygen and dissolved TMs. Furthermore, it is shown via online electrochemical mass spectrometry (OEMS) that O2 reduction in the here-used LP47 electrolyte consumes ∼2.3 electrons/O2. Using this value, the lattice oxygen release deduced from the 3-electrode setup upon charging of the NCA WE is in good agreement with OEMS measurements up to NCA potentials >4.65 VLi. At higher potentials, the contributions from the reduction of TMII+ ions can be quantified by comparing the integrated SE current with the O2 evolution from OEMS.

Explosion characteristics of two-phase ejecta from large-capacity lithium iron phosphate batteries

Explosion characteristics of two-phase ejecta from large-capacity lithium iron phosphate batteries

Thermal runaway evolution of a 4S4P lithium-ion battery pack induced by both overcharging and unilateral preheating

To clarify the thermal runaway characteristics of lithium-ion battery pack, this study has established a thermal runaway experimental platform based on actual power battery pack. A 4 in series and 4 in parallel battery pack was assembled using 86 Ah lithium iron phosphate batteries, and the experiment of thermal runaway induced by overcharging and unilateral preheating was carried out. The behavior and characteristics including the temperature change characteristics of each cell, the heat generated and transfer paths during thermal runaway propagation, the voltage changes of each serial module and the total voltage, flame evolution behavior, gas generation characteristics, debris, and mass loss were investigated. The research results show that module 1 was the first to experience thermal runaway due to preheating. The redistributed current caused the batteries in the remaining modules to rapidly generate heat. Subsequently, the heat transfer from module 1 triggered thermal runaway in modules 2, 3, and 4 in sequence. The entire flame combustion process lasted for 38 min, with the maximum temperature reaching 937.1 °C, resulting in thermal runaway in all batteries. The sequence of thermal runaway has been clarified, with the flame generated by the ignition of the battery casing, connecting tabs, and combustible gases emitted from the batteries serving as the primary paths for heat transfer and thermal radiation. The experimental results provide valuable insights into the thermal engineering issues of large-scale lithium-ion battery pack.

Operando Stack Pressure Measurement of LFP/Graphite and LMFP/Graphite Cells to aid in State of Charge Prediction

Abstract One of the biggest issues facing electric vehicles with LiFePO4 (LFP) batteries is state of charge management. Over much of the state of charge window, the voltage of both LFP and LiMnxFe1-xPO4 (LMFP) batteries does not vary. Therefore, state of charge management for LFP batteries relies on coulomb counting, which requires frequent charging to 100% to remain accurate. We propose to use the signal from pressure sensors placed between prismatic cells in battery modules to help determine the state of charge of LFP and LMFP batteries. Using LFP and LMFP pouch cells to demonstrate this principle, the pressure vs. time profiles of cells constrained in fixed volumes reveal distinct and repeatable profiles, which can be used to determine the state of charge in combination with voltage monitoring. Additionally, a simulated LFP battery pack was constructed and the pressure vs. time profile was monitored in the presence of compliant material under low initial force loadings to demonstrate how this could work in an EV battery.

Inaccuracy principle and dissolution mechanism of lithium iron phosphate for selective lithium extraction from brines

The electrochemical lithiation/delithiation (ELD) method with the typical active materials being LiFePO4 and LiMn2O4, is the next generation technique for the selective lithium extraction from slat-lake brines owning to the advantages of high selectivity and excellent capacity and feasibility. However, the dissolution of LiFePO4/FePO4 (LFP/FP) during the ELD is seldom studied and an inaccurate measurement method for dissolution may result in obtaining an incorrect feasible application range for LFP/FP. Here, electrochemical workstation-electrochemical quartz crystal microbalance (EW-EQCM) is first utilized in the brine system to acquire the in-situ dissolution behavior of LFP/FP redox couple and verify the inaccuracy principle of the dissolution measurement. Both experimental results and thermodynamic calculations demonstrated that the accurate dissolution ratios can only be obtained by iron ions and phosphates at pH < 2.7 and pH < 5.3, respectively, which is induced by the narrow soluble range of iron ions and the formation of Ca5(PO4)3OH and Mg3(PO4)2 precipitation. In addition, the stable pH range of LFP and FP is 4 to 10 and 3 to 5, respectively, and the dissolution is caused by the formation of thermodynamically more stable metal ions, metal ion complexes, and metal ion hydroxides. At the optimum pH, the capacity can maintain 35 mg/g with average dissolution ratios of the cathode and anode lower than 0.1 %. This research sheds light on the accurate dissolution measurement range and method, dissolution mechanism and feasible application range of the LFP/FP redox couple.

Enhanced Electrochemical Performance of Lithium Iron Phosphate Cathodes Using Plasma-Assisted Reduced Graphene Oxide Additives for Lithium-Ion Batteries

One-dimensional lithium-ion transport channels in lithium iron phosphate (LFP) used as a cathode in lithium-ion batteries (LIBs) result in low electrical conductivity and reduced electrochemical performance. To overcome this limitation, three-dimensional plasma-treated reduced graphene oxide (rGO) was synthesized in this study and used as an additive for LFP in LIB cathodes. Graphene oxide was synthesized using Hummers’ method, followed by mixing with LFP, lyophilization, and plasma treatment to obtain LFP@rGO. The plasma treatment achieved the highest degree of reduction and porosity in rGO, creating ion transfer channels. The structure of LFP@rGO was verified through scanning electron microscopy (SEM) analysis, which demonstrated that incorporating 10.0 wt% of rGO into LFP resulted in successful coverage by the rGO layer, forming LFP@rGO-10. In half-cell tests, LFP@rGO-10 exhibited a specific capacity of 142.7 mAh g−1 at the 1.0 C-rate, which is higher than that of LFP. The full-cell exhibited 86.8% capacity retention after 200 cycles, demonstrating the effectiveness of rGO in enhancing the performance of LFP as an LIB cathode material. The outstanding efficiency and performance of the LFP@rGO-10//graphite cell highlight the promising potential of rGO-modified LFP as a cathode material for high-performance LIBs, providing both increased capacity and stability.

Inhibition Effect of Liquid Nitrogen on Suppression of Thermal Runaway in Large Lithium Iron Phosphate Batteries

Inhibition Effect of Liquid Nitrogen on Suppression of Thermal Runaway in Large Lithium Iron Phosphate Batteries