High Performance LiFePO4 Research Articles

An unsaturated chain carbonate additive contributing to high-performance LiFePO4//graphite battery at broad temperature range

Vinylene carbonate (VC) electrolyte additive can extend the cycle life of lithium-ion batteries (LIBs) by the polymerization of CC bonds and ring opening at the electrode/electrolyte interface. However, the interface film produced by VC exhibits extremely high impedance at low temperatures (LT), leading to a rapid deterioration in battery performance. In this work, butyl 2-acetylene 1, 4-diethoxycarbonate (BAEC) additive, a chain carbonate with CC bond, is designed for the first time to overcome the fatal low-temperature defect of VC. The higher unsaturation CC bond endows BAEC with an elevated REDOX activity for film forming. When BAEC is collaborated with VC which has better cathodic compatibility, the LiFePO4//Graphite pouch cells demonstrate an ultrahigh capacity retention of 105.8 % after 300 cycles at 0 °C and 101.2 % after 130 cycles at −10 °C. In contrast, the VC system fails only after 10 cycles at 0 °C and cannot achieve normal charge and discharge at −10 °C. Moreover, BAEC + VC system exhibits an enhanced capacity retention of 85.7 % at the 500th cycle at 45 °C. Deep exploration reveals that in addition to the intrinsic factors of the higher unsaturation which are the guarantee of reactivity and uniformity for film generation, BAEC can regulate the initial Li+ solvation structure through steric hindrance and interaction with the solvent which contributes to preeminent interface film stability and conductivity. This work proves that unsaturated chain carbonates are worthwhile additives which can promote the development of LIBs with strong environmental adaptability.

Synthesis of LiFePO4 using adenosine triphosphate as a new organic phosphorus source and its solvothermal reaction process

LiFePO4 is prepared by hydrothermal method using phosphoric acid (named as LFP-a) or adenosine triphosphate (LFP-b) as phosphoric sources, respectively. The effects of two phosphorus sources on crystal structure, particle morphology and electrochemical properties of the materials are investigated. Meanwhile, the mechanism of adenosine triphosphate as phosphoric source to synthesis LiFePO4 is proposed. The results show that the phosphorus source has significant influence on the synthesized materials. Compared with LFP-a, LFP-b material has higher crystallinity, better particle uniformity and dispersion. This is the result of the slow release of Li3PO4 in the hydrothermal process of the ATP-dominated precursor solution, and the subsequent reaction is relatively ordered, resulting in excellent electrochemical performance: the reversible capacity at 1 C is 148.24 mAh g−1, 137.01 mAh g−1 after 100 cycles, and the capacity retention rate is 92.4 %. This work provides a reference for the preparation of high-performance LiFePO4 from organophosphorus sources.

Aliphatic Polycarbonate-Based Binders for High-Loading Cathodes by Solvent-Free Method Used in High Performance LiFePO4|Li Batteries.

The binder ratio in a commercial lithium-ion battery is very low, but it is one of the key materials affecting the battery's performance. In this paper, polycarbonate-based polymers with liner or chain extension structures are proposed as binders. Then, dry LiFePO4 (LFP) electrodes with these binders are prepared using the solvent-free method. Polycarbonate-based polymers have a high tensile strength and a satisfactory bonding strength, and the rich polar carbonate groups provide highly ionic conductivity as binders. The batteries with poly (propylene carbonate)-plus (PPC-P) as binders were shown to have a long cycle life (350 cycles under 1 C, 89% of capacity retention). The preparation of dry electrodes using polycarbonate-based polymers can avoid the use of solvents and shorten the process of preparing electrodes. It can also greatly reduce the manufacturing cost of batteries and effectively use industrial waste gas dioxide oxidation. Most importantly, a battery material with this kind of polycarbonate polymer as a binder is easily recycled by simply heating after the battery is discarded. This paper provides a new idea for the industrialization and development of a novel binder.

Direct synthesis of a lithium carboxymethyl cellulose binder using wood dissolving pulp for high-performance LiFePO4 cathodes in lithium-ion batteries

Lithium carboxymethyl cellulose (CMC-Li) is a promising novel water-based binder for lithium-ion batteries. The direct synthesis of CMC-Li was innovatively developed using abundant wood dissolving pulp materials from hardwood (HW) and softwood (SW). The resulting CMC-Li-HW and CMC-Li-SW binders possessed a suitable degree of substitutions and excellent molecular weight distributions with an appropriate quantity of long- and short-chain celluloses, which facilitated the construction of a reinforced concrete-like bonding system. When used as cathode binders in LiFePO4 batteries, they uniformly coated and dispersed the electrode materials, formed a compact and stable conductive network with high mechanical strength and showed sufficient lithium replenishment. The prepared LiFePO4 batteries exhibited good mechanical stability, low charge transfer impedance, high initial discharge capacity (∼180 mAh/g), high initial Coulombic efficiency (99 %), excellent cycling performance (<3% loss over 200 cycles) and good rate capability, thereby outperforming CMC-Na and the widely used cathode binder polyvinylidene fluoride.

Correction: A sandwich-like CMC-based/graphene/CMC-based conductive agent prepared from needle coke for high-performance LiFePO4 batteries

Correction: A sandwich-like CMC-based/graphene/CMC-based conductive agent prepared from needle coke for high-performance LiFePO4 batteries

A sandwich-like CMC-based/graphene/CMC-based conductive agent prepared from needle coke for high-performance LiFePO4 batteries

A sandwich-like CMC-based/graphene/CMC-based conductive agent prepared from needle coke for high-performance LiFePO4 batteries

High-performance Na-doped LiFePO4 cathode material derived from acid-washed iron red for the simultaneous immobilization of multi-metals

High-performance Na-doped LiFePO4 cathode material derived from acid-washed iron red for the simultaneous immobilization of multi-metals

High performance LiFePO4 nanomaterial obtained by a tavorite-to-olivine phase transition at low-temperature

The main problem currently faced in the large-scale production of LiFePO4 by solid-phase methods is the high energy consumption caused by solid/melt-phase lithiation process. Herein, LiFePO4 nanoparticles are successfully obtained by a phase transition from the tavorite LiFePO4OH structure to the olivine LiFePO4 structure at low-temperature (550–600 °C). This desirable LiFePO4OH precursor is prepared via a wet pre-lithiation process, and its thermodynamic feasibility is demonstrated by thermodynamic calculation. The liquid-phase lithiation followed by a simple carbothermal reduction process (c.f., the solid/melt-phase lithiation process of the traditional solid-state method) results in a superior mass transfer efficiency and reaction uniformity. It therefore prevents the requirement for a higher temperature and longer sintering process. It is also indicated that on the premise of the lattice perfection, a lower crystallization temperature is not only conducive to widening the effective ion diffusion channels of LFP, inhibiting further crystal growth, and shortening the diffusion path, but it also reduces the synthetic cost. As a result, a crystallization temperature of 600 °C (or 550 °C) is optimal, and the resulting LiFePO4 electrode can deliver an appealing high rate capacity of 147.7 mA h g−1 at 10 C. It is expected that this novel synthetic route could be employed for the large-scale commercial production of high performance LiFePO4 cathode materials at a low cost.

High-performance LiFePO4 and SiO@C/graphite interdigitated full lithium-ion battery fabricated via low temperature direct write 3D printing

Lithium-ion batteries (LIBs) composed of thin tape–casted electrodes face some intrinsic challenges especially the trade-off between energy density and power density. Three-dimensional (3D) structural batteries fabricated by 3D printing have the potential to overcome this challenge. Silicon oxide–based materials are promising candidates for the next-generation high-performance LIBs. In this study, interdigitated full batteries composed of comb-like LiFePO4 3D cathodes and comb-like SiO@C/graphite 3D anodes are fabricated via low temperature direct writing 3D printing process. The 3D printing at a low temperature of below −20 °C enables the 3D-printed SiO@C/graphite electrodes obtain a high porosity of ∼60% and tri-modally hierarchical porous microstructure. Comb-like 3D SiO@C/graphite anodes with the thickness of ∼418 μm, ∼692 μm, and ∼806 μm and corresponding mass loading of ∼39.2 mg cm-2, ∼60.9 mg cm-2, ∼84.3 mg cm-2, respectively, are fabricated to evaluate their electrochemical performance. These thick 3D electrodes display impressive areal capacities of ∼17.9, ∼26.7, and ∼33.2 mA h cm-2 @ 0.3 C depending on their electrode thickness. Coupled with comb-like LiFePO4 3D cathodes, interdigitated full batteries with two N/P ratios of 0.91 and 0.82 are fabricated. These full batteries exhibit high energy density, high power density, and stable cycling performance.

Electrochemical Properties of Pristine and Vanadium Doped LiFePO4 Nanocrystallized Glasses

In our recent papers, it was shown that the thermal nanocrystallization of glassy analogs of selected cathode materials led to a substantial increase in electrical conductivity. The advantage of this technique is the lack of carbon additive during synthesis. In this paper, the electrochemical performance of nanocrystalline LiFePO4 (LFP) and LiFe0.88V0.08PO4 (LFVP) cathode materials was studied and compared with commercially purchased high-performance LiFePO4 (C-LFP). The structure of the nanocrystalline materials was confirmed using X-ray diffractometry. The laboratory cells were tested at a wide variety of loads ranging from 0.1 to 3 C-rate. Their performance is discussed with reference to their microstructure and electrical conductivity. LFP exhibited a modest electrochemical performance, while the gravimetric capacity of LFVP reached ca. 100 mAh/g. This value is lower than the theoretical capacity, probably due to the residual glassy matrix in which the nanocrystallites are embedded, and thus does not play a significant role in the electrochemistry of the material. The relative capacity fade at high loads was, however, comparable to that of the commercially purchased high-performance LFP. Further optimization of the crystallites-to-matrix ratio could possibly result in further improvement of the electrochemical performance of nanocrystallized LFVP glasses.

Rational Design of Effective Binders for LiFePO4 Cathodes.

Polymer binders are critical auxiliary additives to Li-ion batteries that provide adhesion and cohesion for electrodes to maintain conductive networks upon charge/discharge processes. Therefore, polymer binders become interconnected electrode structures affecting electrochemical performances, especially in LiFePO4 cathodes with one-dimensional Li+ channels. In this paper, recent improvements in the polymer binders used in the LiFePO4 cathodes of Li-ion batteries are reviewed in terms of structural design, synthetic methods, and working mechanisms. The polymer binders were classified into three types depending on their effects on the performances of LiFePO4 cathodes. The first consisted of PVDF and related composites, and the second relied on waterborne and conductive binders. Profound insights into the ability of binder structures to enhance cathode performance were discovered. Overcoming the bottleneck shortage originating from olivine structure LiFePO4 using efficient polymer structures is discussed. We forecast design principles for the polymer binders used in the high-performance LiFePO4 cathodes of Li-ion batteries. Finally, perspectives on the application of future binder designs for electrodes with poor conductivity are presented to provide possible design directions for chemical structures.

A High Performance LiFePO4 Cathode Material with 3D Conduction Network Connected by 1D helix-like Ag Nano-chains

A High Performance LiFePO4 Cathode Material with 3D Conduction Network Connected by 1D helix-like Ag Nano-chains

Microspherical LiFePO3.98F0.02/3DG/C as an advanced cathode material for high-energy lithium-ion battery with a superior rate capability and long-term cyclability

Regular spherical FePO4/3DG precursor with good dispersion, uniform morphology, and diameters of 2~3 μm was hydrothermally synthesized, followed by synthesizing LiFePO3.98F0.02/3DG/C material via a two-step carbothermal reduction technology with ascorbic acid and glucose as carbon sources. The morphology, structure, and carbon content of the material were characterized by SEM, XRD, XPS, TEM, and thermogravimetric analyzer (TGA). The electrochemical properties of material were systematically studied by means of constant current charge and discharge, electrochemical impedance spectroscopy (EIS), and cyclic voltammetry (CV). The results revealed that the initial discharge specific capacity of LiFePO0.98F0.02/3DG/C material was 158.7, 144.5, 130.4, 114.8, 96.8, and 80.3 mAh/g at 0.2 C, 0.5 C, 1 C, 2 C, 5 C, and 10 C, respectively, and the capacity retention rate still remained 98.9% after 100 cycles at 0.2 C, indicating excellent rate performance and cycle stability. Obviously, LiFePO3.98F0.02/3DG/C material exhibited remarkable improvement in comparison with the pristine LiFePO4 material. Therefore, the synergy of F− doping and 3DG coating was an effective method in synthesis of high electrochemical performance LiFePO4 composite material.

Study on the Preparation of Lifepo4 by Hydrothermal Method

A simple hydrothermal process combined with carbon coating is attempted to prepare nano particle LiFePO4 cathode materials for Li-ion batteries. A carbon coating process with glucose is used to make LiFePO4/C composites. The structure, morphology and electrochemical properties of the materials are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and constant current charge/discharge. The X-ray diffraction pattern indicates that the pure phase LiFePO4 material could be prepared at different reaction temperatures, and the pure phase LiFePO4 material could not be prepared with the reaction time of 6 h. SEM test shows that the dispersion of LiFePO4 particles become better with the increase of reaction temperatures and the morphology is more regular with the increase of reaction temperature. But when the reaction temperature increases to 200 °C, LiFePO4 particles reaggregate severely. As the reaction time increases, the particles of the sample gradually grow. The electrochemical performance indicates that the sample synthesized at 180 °C for 10 h has the highest specific capacity of 139.5 mAh·g−1 at 0.1 C. This study shows that proposed process can be a potential promising way to prepare high performance LiFePO4 cathode materials.

Concentration-Controlled and Phytic Acid-Assisted Synthesis of Self-Assembled LiFePO4 as Cathode Materials for Lithium-Ion Battery

The olivine LiFePO4 with various morphologies and different growth lattice planes was prepared by a controllable hydrothermal method with changing precursor concentration and using phytic acid as phosphorus source. The microstructure, crystal orientation and electrochemical performance of the prepared samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HR-TEM) and charge–discharge tests. The results show that the morphologies of all samples change from spindle-like to hierarchical plate-like and then to long plate-like shape, and the main exposed facets transform from (100) to (001). This indicates that the precursor concentration and phytic acid play important roles in exposing facets and controlling the morphology of LiFePO4. In order to illustrate these phenomena, a reasonable assembly process is provided and the formation is explained. Li ion diffusion coefficient along [100] and [001] directions was calculated by using electrochemical impedance spectroscopy (EIS). The results show that the diffusion coefficient of (100) facet is higher than that of (001) facet, indicating a good electrochemical performance for (100) facet. In addition, the capacity test is carried out, which also confirms the above results. With the precursor concentration of 0.5[Formula: see text]M, the obtained LiFePO4 with self-assembled hierarchical structure, smaller size and (100) facet shows the best electrochemical performance: 162.1[Formula: see text]mAh/g at 0.1[Formula: see text]C and 112.4[Formula: see text]mAh/g at 10[Formula: see text]C. Using phytic acid as phosphorus source and controlling precursor concentration to prepare high performance LiFePO4 open up a new prospect for the production of cathode materials for lithium ion batteries.

Lithium Clustering during the Lithiation/Delithiation Process in LiFePO4 Olivine-Structured Materials.

Olivine-structured LiFePO4 is one of the most popular cathode materials in lithium-ion batteries (LIBs) for sustainable applications. Significant attention has been paid to investigating the dynamics of the lithiation/delithiation process in LixFePO4 (0 ≤ x ≤ 1), which is crucial for the development of high-performance LiFePO4 material. Various macroscopic models based on experimental evidence have been proposed to explain the mechanism of phase transition from LiFePO4 to FePO4, such as the shrinking core (i.e., core–shell) model, Laffont’s (i.e., new core–shell) model, domino-cascade model, phase transformation wave, solid solution model, many-particle models, etc. However, these models, unfortunately, contradict each other and their validity is still under debate. An atomistic model is urgently required to depict the lithiation/delithiation process in LixFePO4. In this article, we reveal the lithiation/delithiation process in LiFePO4 simulated by a computational model using the generalized gradient approximation (GGA + U) method. We find that the clustered configuration is the most energetically favorable, leading to co-operative Jahn–Teller distortion among the inter-polyhedrons that can be observed clearly from the bond patterns. This atomistic model not only offers answers to experimental results obtained at moderate or high rates but also gives the direction to further improve the rate capability of LiFePO4 cathode material for high-power LIBs.

Holey graphenes as the conductive additives for LiFePO4 batteries with an excellent rate performance

Graphene has been investigated and widely used as the high performance conductive additives in lithium ion batteries. Unfortunately, the LiFePO4 batteries with graphene additives present quite a low rate performance because the graphene with planar structure blocks the Li ion transportation. Herein, a binary conductive additive containing only 1 wt% holey graphene (HG) and 1 wt% Carbon Black such as Super-P (SP) has been developed, which achieves excellent high-rate performance for the LiFePO4 battery that is comparable to that of the battery with 10 wt% SP. The HG with large amount of holes and large specific surface area substantially enhances the electronic conductivity of LiFePO4 electrode, but not compromises the high efficient ionic transportation. A small content of SP as the supplement of long-range conductive network formed by HG can contact the LiFePO4 sufficiently for achieving excellent conductivity in the whole LiFePO4 electrode. A balance of electronic conductivity and ionic diffusivity can be achieved using the HG and SP simultaneously. The HG and SP with low content can synergistically construct an excellent ionic and electronic conductive network in LiFePO4 electrode. This study may promote the commercial applications of HG additives for high performance LiFePO4 batteries.

Facile strategies to utilize FeSO4·7H2O waste slag for LiFePO4/C cathode with high performances

This study proposes two economic and environmental-friendly strategies to synthesize LiFePO4/C composite as cathode for lithium ion battery, by utilizing the byproduct of industrial TiO2, FeSO4·7H2O waste slag, as one raw material. And divalent ferrous phosphate, Fe3(PO4)2·8H2O, plays a significant role of intermediate. By wet-mill and spray-drying method, monodisperse LiFePO4/C microspheres are obtained with a hierarchically porous structure. And the micro-spherical LiFePO4/C composite shows an excellent rate capability and cycle performance, with initial discharge capacities of 153.6, 132.9, and 115.1 mAh g−1 at 0.5 C, 5 C and 20 C, respectively. The capacity retention remains at 88.4% even after 1000 cycles at the high rate of 10 C. By an improved conventional method, a hybrid-crystalline precursor is prepared and the submicron-sized LiFePO4/C composite also exhibits comparable rate capability. Therefore, the FeSO4·7H2O waste slag can partially or totally replace analytically pure ones to manufacture high performance LiFePO4, which is a low-cost and promising option.

Regenerating the used LiFePO4 to high performance cathode via mechanochemical activation assisted V5+ doping

Abstract The wide usage of LiFePO4 batteries makes their recovery and recycling urgent. Here, a novel, efficient and environmentally friendly recycling process has been developed to recover high performance LiFePO4 nano composites from spent LiFePO4 materials. The process comprises an intensive mechanochemical activation through mixing with precursor mixture and one-step solid state heat treatment. Spent LiFePO4, V2O5, Li2CO3, and NH4H2PO4 are mixed according to the molar ratio of 1-xLiFePO4@xLi3V2(PO4)3 (x = 0, 0.005, 0.01, 0.03 and 0.1). In the typical process, the decomposition of self-contained binder and the conductive carbon provide a reducing environment as well as an in-situ coating carbon source. The SEM, XRD and XPS results illustrate that V5+ is doped in the Fe2+ site when x

A novel low-cost and simple colloidal route for preparing high-performance carbon-coated LiFePO4 for lithium batteries

Abstract Nanosized carbon-coated lithium iron phosphate (LiFePO4/C) particles were synthesized using a novel low-cost colloidal process with LiH2PO4, FeCl2 and anhydrous N-methylimidazole (NMI) as starting materials, following by a short annealing step at 600 °C. The ∼3–5 nm thick carbon coating comes from the carbonization of molten salt NMIH+Cl− derived from NMI; the resulting carbon contents of the LiFePO4/C powder is 2.53 wt.%. The materials were characterized by thermogravimetric and differential thermal analysis, differential scanning calorimetry, powder X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscopy, atomic absorption spectroscopy, Raman spectroscopy, four-point probe method, cyclic voltammetry and galvanostatic cycling experiments in coin cells. The LiFePO4 phase reveals agglomeration of semi-spherically particles with an average individual size of 35 ± 4 nm. Carbon-coated LiFePO4 posseses electronic conductivity of 1.4 × 10−3 S cm−1 at room temperature causing a markable increase in rate capability. Cycling the cells between 2.2 and 4.2 V vs. Li+/Li resulted in a discharge capacity of 164 mAh g−1 at the first cycle of C/20 and 162 mA hg−1 after 35 cycles, which corresponds to over 95% of the theoretical capacity of olivine LiFePO4.