KR20130035495A - Hybrid namoparticle of lithium iron phosphate with carbon and lithium phosphate and method for preparing the same - Google Patents

Abstract

PURPOSE: A manufacturing method of a hybrid nanoparticle is provided to obtain a hybrid nanoparticle with high-rate performance in a discharging rate of 2C and 20C without loss of capacity. CONSTITUTION: A manufacturing method of the hybrid nanoparticle of a lithium phosphate and carbon of LiFePO4 comprises a step of mixing a LiFePO4 and lithium phosphate precursor and a surfactant to a solvent; a step of obtaining powder by evaporating the solvent in the mixture; and a step of heat-treating the powder in a non-oxygen atmosphere. The surfactant is the triblock copolymer of polyethylene oxide and polypropylene. The weight ratio of the propylene oxide in the block copolymer is 10-90wt%.

Description

Hybrid Namoparticle of Lithium Iron Phosphate with Carbon and Lithium Phosphate And Method for Preparing the same

The present invention relates to a nano hybrid of LiFePO ₄ with carbon and lithium phosphate, and a method for preparing the same.

More particularly, the present invention relates to a hybrid nanoparticle of carbon and lithium phosphate of LiFePO ₄ having a high charge and discharge rate and usable as a cathode material of a lithium secondary battery, and a method of manufacturing the same.

Lithium secondary batteries (LiB) are being developed as an efficient electrical energy storage device for portable electronic devices. Recently, considerable demand for electric vehicles (EVs) or hybrid electric vehicles (HEVs) has facilitated considerable research into high performance batteries with both high energy and power density.

Olivine type LiFePO ₄ is a new cathode material with low cost, the most important factor for toxicity and commercialization, good thermal stability, excellent cycle stability, flat voltage profile and theoretical large capacity (~ 170mAh / g). It was introduced in 1997. However, due to the relatively low electrical ion conductivity, it showed low electrochemical performance as a cathode material.

Several attempts have been made to improve the mobility of electrons and lithium ions for high rate battery applications. For example, LiFePO ₄ was coated with an electrically conductive carbon layer, and metal cations (Zr, Nb, Mg, or Ti) were doped onto LiFePO ₄ to improve electronic conductivity. On the other hand, particle size and morphology were improved to improve lithium ion diffusion in LiFePO ₄ , and the crystal face on the particle surface was preferentially tuned to the (010) plane which is optimal for lithium ion transport.

Recently, lithium phosphate and carbon were simultaneously coated on the surface of LiFePO ₄ particles to achieve an amazing rate of discharge. However, to improve the transport properties of lithium ions and electrons, LiFePO ₄ It was necessary to develop a practical method for simultaneously controlling the surface coating layer as well as the particle internal structure.

Accordingly, an object of the present invention is to provide a novel material as a cathode material for a lithium secondary battery exhibiting a high rate of charge and discharge and a manufacturing method thereof.

In order to solve the above problems, the present invention is a method for producing a hybrid nanoparticles of carbon and lithium phosphate of LiFePO ₄ , including a surfactant, and carbonizing the surfactant through heat treatment under anoxic conditions It provides a method comprising the step of.

The surfactant may be a nonionic organic surfactant.

The surfactant may be an amphiphilic block copolymer.

The surfactant may be a triblock copolymer of polyethylene oxide and polypropylene oxide, and the weight ratio of propylene oxide in the block copolymer may be 10 to 90% by weight.

In addition, the present invention provides a method for producing a hybrid nanoparticle of LiFePO ₄ with carbon and lithium phosphate, LiFePO ₄ And mixing the precursor of lithium phosphate and the surfactant in a solvent; Evaporating the solvent to obtain a powder; And heat treating the powder in an oxygen-free atmosphere.

LiNO ₃ , Fe (NO ₃ ) ₃ 9H ₂ 0 and H ₃ PO ₄ may be mixed and used as precursors of the LiFePO ₄ and lithium phosphate.

The surfactant may be a nonionic organic surfactant.

The surfactant may be an amphiphilic block copolymer.

The surfactant may be a triblock copolymer of polyethylene oxide and polypropylene oxide, and the weight ratio of propylene oxide in the block copolymer may be 10 to 90% by weight.

An oxygen-free atmosphere is a H ₂ / Ar mixed gas atmosphere, the heat treatment can be made at 600 ~ 800 ℃.

The present invention also provides hybrid nanoparticles of LiFePO ₄ with carbon and lithium phosphate, and a cathode material for a secondary battery including the same.

The present invention provides a simple method for preparing hybrid nanoparticles of LiFePO ₄ with carbon and lithium phosphate. When using the prepared hybrid nanoparticles of the present invention as a cathode material for a secondary battery, there is no capacity loss at a high rate of charge and discharge.

1 is a schematic diagram showing the principle of the production of hybrid nanoparticles of carbon and lithium phosphate of LiFePO ₄ particles.
Figure 2 is a TEM photograph of (a) F108-LFP and (b) P123-LFP particles.
3 is an XRD pattern of (a) F108-LFP and (b) P123-LFP.
(The bar diagram below FIG. 3 shows the JCPDS card no. 00-0443 reference peak)
4 is an IV curve of (a) P123-LFP (b) F108-LFP (c) bulk LFP measured by a Physical Property Measurement System (9T-PPMS).
Figure 5 (a) is a diagram showing the discharge capacity for F108-LFP and P123-LFP between 2.0 and 4.3V voltage limits at 0.1 to 2C rate, (b) is the charge rate of 2C, discharge rate of 2C Shows the cycle characteristics for F108-LFP and P123-LFP between 2.0 and 4.3V voltage limits in (c), (108) (C) shows F108-LFP and P123 between 2.0 and 4.3V voltage limits at 20C charge rate and 2C discharge rate. A diagram showing the cycle characteristics for the LFP (arrow indicates maximum capacity at each electrochemical step).
FIG. 6 shows ⁷ Li MAS NMR spectra for (a) F108-LFP and (b) P123-LFP and ³¹ P MAS NMR spectra for (c) F108-LFP and (d) P123-LFP.
FIG. 7 is a view showing TEM images of porous structures of (a) F108 polymer and (b) P123 polymer after heat treatment at 400 ° C. FIG.
8 is a diagram showing (a) N2 adsorption / desorption isotherm (black and empty points respectively adsorption and desorption) at 77K of porous structure when (F) polymer is used (b) when P123 polymer is used (c) (D) Density Funtional Theory pore size distribution curve of porous structure.
9 is a diagram showing a porous structure XRD pattern when (a) F108 polymer is used (b) P123 polymer after heat treatment at 400 ° C, and (c) Li ₃ (PO ₄ ) phase (JCPDS Card no.03- 4221), (d) Li ₄ Fe _{3 .528} (PO ₄ ) ₄ Phase (JCPDS Card no. 25-0116) (e) LiFePO ₄ Phase (JCPDS Card no.00-0443) Reference peaks are shown in the bar diagram below. The figure shown.
10 shows Raman spectra of (a) F108-LFP and (b) P123-LFP.
11 is a diagram showing a TEM photograph of (a) bulk LFP and (b) XRD pattern.
12 is a diagram showing EDX ray analysis through STEM experiments for F108-LFP and P123-LFP.
(STEM dark field images of (a) F108-LFP and (b) P123-LFP, respectively, and the table below shows the molar ratios of phosphorus and iron elements in the numerical areas, and the green curve in the TEM picture shows a single LFP particle) Represents the carbon profile at, and the red line corresponds to the scanning route of the carbon profile in STEM mode)
FIG. 13 is an HRTEM photograph showing poor crystallized carbon layers of (a) single F108-LFP and (b) P123-LFP.

Although the terms used in the present invention have been selected as general terms that are widely used at present, there are some terms selected arbitrarily by the applicant in a specific case. In this case, the meaning described or used in the detailed description part of the invention The meaning must be grasped.

In the present invention, carbon and LiFePO ₄ It provides a simple method utilizing a surfactant to form a mesoscopic internal structure (hereinafter hybrid LFP) with particles of lithium phosphate.

That is, the present invention is a method for producing a hybrid nanoparticles of LiFePO ₄ with carbon and lithium phosphate, including a surfactant, comprising the step of carbonizing the surfactant through heat treatment under anoxic conditions It provides a method characterized in that.

The conductive network structure in the hybrid LFP can be obtained by carbonizing the self-assembled structure of the nonionic surfactant through an anoxic, high temperature heat treatment (see FIG. 1). The surfactant is formed in a low temperature aging process. As a structure directing agent, it acts as a carbon source in high temperature heat treatment and plays a decisive role in controlling the crystallinity of inorganic materials.

More specifically, the method for producing hybrid nanoparticles of carbon and lithium phosphate of LiFePO ₄ of the present invention is LiFePO ₄ And mixing the precursor of lithium phosphate and the surfactant in a solvent; Evaporating the solvent to obtain a powder; And heat-treating the powder in an oxygen-free atmosphere.

LiFePO ₄ And LiNO ₃ , Fe (NO ₃ ) ₃ 9H ₂ 0, and H ₃ PO ₄ may be used as a precursor of lithium phosphate.

As the surfactant, a nonionic organic surfactant may be used, and for example, both lipophilic block copolymers may be used. As the both lipophilic block copolymers, triblock copolymers of polyethylene oxide and polypropylene oxide may be used. The weight ratio of propylene oxide in the block copolymer may be 10 to 90% by weight, preferably propylene oxide is preferred for the high crystallinity of the hybrid nanoparticles obtained using at least 50% by weight, more preferably at least 70% by weight. Do.

The oxygen-free atmosphere may be used as long as oxygen is not present, but a H ₂ / Ar mixed gas atmosphere is preferable.

The heat treatment may be performed preferably at 600 to 800 ° C. rather than 550 to 850 ° C. to increase the crystallinity and to obtain excellent electrochemical properties. Through heat treatment, dense hybrid nanoparticles of carbon and lithium phosphate of LiFePO ₄ particles are finally obtained.

The present invention also provides a hybrid nanoparticle of LiFePO ₄ with carbon and lithium phosphate, and a cathode material for a high-rate secondary battery including the same.

Hereinafter, the technical structure of the present invention will be described in detail with reference to the accompanying drawings and preferred embodiments. However, the present invention is not limited to the embodiments described herein but may be embodied in other forms. Like reference numerals designate like elements throughout the specification.

As surfactants, two types of amphiphilic triblock copolymers, polyethylene oxide (PEO) and polypropylene oxide (PPO), namely F-108 (PEO-b-PPO-b-PEO, molecular weight = 14,600 g / mol, PPO: PEO = 2: 8) and P-123 (molecular weight = 5,750 g / mol, PPO: PEP = 7; 3) were used as nonionic surfactants.

The heat treatment finally yields a dense hybrid nanoparticle of carbon and LiFePO ₄ particles of lithium phosphate, and when F108 or P123 is used as the surfactant, respectively, it will be referred to as F108-LFP or P123-LFP, respectively.

Depending on the type of triblock copolymer the electrochemical performance can vary significantly. Through experiments, both have the expected performance as cathode materials for high-rate lithium-ion batteries. Preferably, P123-LFP using P123 having a higher content of propylene oxide as a surfactant is more preferable.

To synthesize hybrid nanoparticles, ethanol was heated to room temperature using LiNO ₃ , Fe (NO ₃ ) ₃ .9H ₂ 0, H ₃ PO ₄ , an amphoteric block copolymer (F-108 or P-123) and a solvent. After stirring by stirring in, the solvent was slowly evaporated and a powder was obtained.

Next, the powder was heat-treated at 700 ° C. in a H ₂ (5%) / Ar (95%) mixed gas atmosphere. Excess lithium and phosphate precursors were intentionally used in the synthesis to obtain the lithium phosphate phase. Were induced such that the lithium ion conductivity improvement in bulk by a lithium ion transport through the ^- (......... Li ⁺ PO) lithium phosphate phase electrostatic interactions (electrostatic interaction). During the heat treatment, the organic surfactant is partially carbonized and decomposed to induce volumetric shrinkage of the hybrid structure, which causes the particles to break up into particles due to the surface tension of non-porous composite particles of LiFePO ₄ , lithium phosphate and carbon (see FIG. 1, FIG. 1). In the transmission electron microscope (TEM) images, the average particle diameter of both cases is about 70 nm).

As shown in FIG. 2, the powder X-ray diffraction spectrum of the obtained LFP shows three distinct phase structures. The main peak can be defined as the orthorhombic olivine LiFePO ₄ phase (JCPDS Card no.00-0443). Some small peaks correspond to the triclinic Li ₄ (P ₂ O ₇ ) (JCPDSCardno.05-9243) and the tetragonal Li ₃ (PO ₄ ) phase (JCPDS Card no.05-0058). XRD data can be used to calculate that the ratio of lithium phosphate to LiFePO ₄ phase in the LFP is about 25%. From the (311) diffraction peaks, the average crystal sizes for F108-LFP and P123-LFP were calculated to be 42.4 nm and 51.0 nm, respectively, using the Debye-Scherrer equation. In order to investigate the intermediate structure of the hybrid nanoparticles, a microstructured TEM photograph with LFP organic compounds was attempted. However, due to the decomposition and evaporation of organic molecules, electron beam irradiation did not produce clear TEM pictures. To solve this problem, the H ₂ (5%) / Ar (95%) mixed gas and the sample were heat-treated at 400 ° C. for 5 hours and then at 400 ° C. to remove organic compounds from the block copolymer. Air was injected for 5 hours. The sample obtained showed a disordered mesoporous structure in both surfactants. (See FIG. 7) Surface area and pore size distributions for F108-LFP and P123-LFP were determined by gas sorption analysis using nitrogen gas. As shown in FIG. 8, the nitrogen adsorption and desorption isotherm results show typical mesoporous properties of type IV materials. BET surface area and pore size distribution obtained is 90.6m ² /g,20.7nm for 86.6m ² /g,23.4nm, and P123-LFP and the respective F108-LFP. After heat treatment at 400 ° C., the XRD spectra of mesoporous material were LiFePO ₄ (JCPDSCardno.00-0443), Li ₃ (PO ₄ ) (JCPDSCardno.03-4221), Li ₄ Fe _3.528 (PO ₄ ) ₄ (JCPDSCardno.25-0116) and mixtures of amorphous phases. This is because they are forming a hybrid structure with the olivine structure (see Fig. 9). Olivine LiFePO ₄ phase generally requires high temperatures in the range of 600 to 800 ° C for good crystallization to optimize electrochemical performance.

Through heat treatment at 700 ° C. for 2 hours with H ₂ / Ar mixed gas, the block copolymer was partially converted into graphitized carbon, thereby improving electron transfer. Raman spectra clearly showed carbon peaks at 1360 and 1603 cm ^{−1 due} to the D-band (disordered band) and G-band (order band) of carbon (see FIG. 10). The I _D / I _G ratio (0.898) of F018-LFP is slightly higher than that of P123-LFP (0.885). F108 and P123 consist of the same monomers (ethylene oxide and propylene oxide), with the weight ratio (70%) of propylene oxide (relatively more hydrophobic) of P123 being higher than F108 (18%). From this, more graphitized carbon is expected to form in P123 than in F108. Electron transport was measured by 9T Physical Property Measurement System (PPMS) at room temperature. As shown in FIG. 3, the currents of the F108-LFP and P123-LFP samples increased by more than one million times that of the bulk sample (see FIG. 11). In addition, it was confirmed that the P123-LFP has a current of 1.23 times higher than the F108-LFP in the voltage range of 0 ~ 10V. From these results, it can be concluded that P123-LFP contains more carbon with graphitization properties (which increases electron transport) than F108-LFP. This result is in good agreement with the Raman spectrum.

The profile of each atom of the hybrid nanoparticles was measured by scanning TEM, which clearly shows a phosphorus atom of 1.5 equivalents per iron precursor and well distributed phosphorus atoms for both particles (see FIG. 12). Energy dispersive X-ray spectroscopy (EDX) ray analysis shows a line profile of carbon atoms across a single LFP particle where the carbon L line increases from the outer wall towards the center of the particle, revealing the presence of carbon inside the particle. In addition, high-resolution TEM photographs confirm that the particles have a thin carbon layer with less crystallization on the surface (see FIG. 13).

To compare the rate capabilities of the P123-LFP and F108-LFP, their discharge capacities were measured between the voltage limits of 2.0 and 4.3V at different C rates, varying from 0.1 to 2C rates. . The discharge capacity at 2C for both positive electrode materials was about 98% of it at 0.1C (Fig. 4 (a)). Regardless of the 20-fold increase in discharge rate, only 2% capacity loss was observed for both structures, indicating high charge transfer and structural stability. The specific capacity of P123-LFP is about 5% higher than that of F108-LFP. Cycle characteristics of the electrode at the 2C charge / discharge rate are shown in FIG. 4B. The P123-LFP maintained a discharge capacity of 137 mAh / g for up to 50 cycles. However, for the F108-LFP, the discharge capacity gradually enjoyed up to 129 mAh / g, according to previous reports, because the capacity of the olivine structure gradually decreased during cycling due to the low mobility of lithium ions and electrons. This is because of poor carbon conductivity. To demonstrate that the cathode material of the present invention can be used as a cathode material for high performance batteries, cycling tests were conducted at higher charging rates. As shown in (c) of FIG. 4, the capacity of P123-LFP was maintained for up to 50 cycles at 20C charge rate and 2C discharge rate, at which time the discharge capacity was 102mAh / g. For the F108-LFP cathode material, it slowly decreased to 97% after a peak discharge capacity of 69mAh / g. This important difference (32%) in terms of the specific discharge capacity between P123-LFP and F018-LFP at high charging rate is probably due to the difference in charge mobility as the charge or discharge rate increases. This could affect the decline further. In the case of P123-LFP, the charge / discharge capacity reaches the plateaus much faster than the F018-LFP as shown in FIG. 4 (c), which contributes to high charge transfer and easy contact between the electrode and the electrolyte.

To support the difference in electrochemical performance between the measured F108 and P123, their XRD powder patterns and TEM photographs were examined. However, no particular difference was found in the structure. These are all olivine structures and have the same lithium alignment, but with different distributions of graphitized carbon and different electrical conductivity. In order to investigate the detailed local electron atmosphere around the resonance nuclei, MAS-NMR (magic angle spinning nuclear magnetic resonance) for ⁷ Li and ³¹ P was taken. FIG. 5 shows ⁷ Li and ³¹ P MAS-NMR spectra for P123-LFP and F018-LFP samples, with identical well-resolved NMR peaks in all samples. However, due to differences in the crystallinity and local atmosphere of the resonance nuclei, the NMR line width of P123-LFP was twice as sharp as that of F018-LFP. From this, it can be concluded that the relatively high crystallinity of P123-LFP further develops a crystal plane that significantly increases the conductivity of lithium ions.

It is known that heat treatment or sonication can control the crystallinity in inorganic materials because high thermal energy causes the components to be rearranged in bulk form for thermodynamic stability in the material. For the first time, however, we found that surfactant molecules can direct atomic alignment in inorganic materials, which plays an important role in ion or electron transport. This result leads to the belief that graphitized carbon and high atomic order regularity are derived from both lipophilic copolymers, which show high performance in reversible electrochemical lithium ion insertion / release processes even at high speeds.

LFP particles were prepared without surfactants to investigate the effects on the phase, size, and shape of the LFP particles of the surfactant. (Prepared in the same manner as hybrid LFP except that no triblock copolymer is used in the synthetic conditions, the following is referred to as bulk LFP). As shown in FIG. 11 TEM and XRD analysis, bulk LFP particles differed from F108-LFP and P123-LFP in phase, size and shape. Bulk LFP particles are composed of tetragonal phase (LiPPO ₄ ) (JCPDS Card no.09-2198, space group Pnma (62) and lattice constant a = 10.329A, b = 6.0065A, c = 4.6908A), Li ₄ (P ₂ O ₇ ) has a tetragonal phase (JCPDS Card no.05-9243), and Li ₃ (PO ₄ ) has a tetragonal phase (JCPDS Card no.05-0058). Their particle size and distribution were much larger and wider than F108-LFP and P123-LFP, respectively, indicating that surfactants play a crucial role in controlling particle growth in size and size distribution.

Summary of key differences between F108-LFP and P123-LFP I _D / I _G electric current FWHM
( ⁷ LI NMR) FWHM
( ³¹ P NMR) F108-LFP 0.898 0.107 mA at 2.3 V
0.188 mA at 4.0 V 33.9 ppm 48.3 ppm P123-LFP 0.885 0.133 mA at 2.3 V
0.232 mA at 4.0 V 19.7 ppm 14.2 ppm

In summary, LiFePO ₄ hybrid nanoparticles of carbon and lithium phosphate have been synthesized by organic-inorganic co-assembly method, which is based on the synthesis of mesoporous material. That is, LiFePO ₄ hybrid nanoparticles of carbon and lithium phosphate were synthesized using an improved general method for mesoporous materials using triblock copolymers, thereby controlling particle size and crystallinity in inorganic nanostructures.

Interestingly, P123-LFP using P123 polymer with more hydrophobic moieties than F108 has more graphitized carbon and twice the crystallinity than F018-LFP. In addition, electrochemical analysis of P123-LFP as a cathode material shows excellent high rate performance without capacity loss at 20C charge rate and 2C discharge rate. The crystallization of graphitic walls and inorganic nanoparticles controlled by triblock copolymers plays an important role in greatly improving the electrochemical performance of batteries.

Experimental Example

LiNO ₃ (ReagentPlus, Aldrich), Fe (NO ₃ ) ₃ ㆍ 9H ₂ O (more than 98%, Aldrich), phosphoric acid (H ₃ PO ₄ , 85%, Junsei), triblock copolymer of PE0 and PPO ( P123, F108, Aldrich) and ethanol (99%, Junsei) were used without purification.

Synthesis of LFP

The synthesis of LFP modified the general approach for mesoporous structure. P123-type LFP was mixed with LiNO ₃ (2.76 g), Fe (NO ₃ ) ₃ ㆍ 9H ₂ O (8.08 g), phosphoric acid (2 mL), P123 (4 g) and ethanol (50) for 5 hours at room temperature. By stirring. Next, the solvent of the solution was concentrated in a dry oven at 60 ° C. for 14 days, milled and heated to 700 ° C. for 12 hours, and then mixed at H ₂ (5%) / Ar (95%) at 700 ° C. for 2 hours. Heat treatment. Synthesis of F108 type LFP is the same as that of P123-LFP except that F108 is used instead of P123.

Characterization

TEM photographs were measured on an Omega EM912 at 120 kV (low resolution) or on a Philips F20 Tecnai at 200 kV (high resolution). Scanning TEM analysis data were obtained from Philips F20 Tecnai. X-ray diffraction data were obtained with graphite-monochromatized Cu-Ka radiation at 40 kV, 120 mA using a Rigaku D / MAX-RB diffractometer at 12 kW. ⁷ Li and ³¹ P MAS NMR spectra were recorded on a Varian VNMR 500 spectrometer with a 3.2 mm Varian MAS probe head using a sample rotation rate of 20 kHz. Raman spectra were obtained on a high resolution Dispersive Raman Microscope (LabRAM HR UV / Vis / NIR, Horiba Jobin Yvon). Carbon content in LFPLCs was analyzed by Element Analyzer (FlashEA 1112, Thermo Finnigan) The pore structure of the sample was analyzed by nitrogen sorption (adsorption and desorption) with an ASAP2020 Micromeritics volumetric adsorption analyzer at 77K. Degassing at 120 ° C. for 24 hours in vacuum (less than 1 Pa) prior to analysis.

Conductivity measurement

Samples were prepared by compressing the powder sample to about 2 kbar at room temperature to measure electrical transport. The sample is 2 mm wide, 9 mm long, and 0.3 mm thick, in the form of a rectangular parallelepiped. Since the resistance of the sample was large enough to neglect the contact resistance, the current flowing through the sample was measured by a two probe measurement technique. Current was measured with a Keithley 238 Source Measure Unit over a voltage range of 0 to 10V. The temperature dependence of the resistance was measured at 0.1 micro A using a physical characterization system (Quantum Design, PPMS) and an Agilent Nanovoltmeter (HP 34420A).

Electrochemical measurement

The electrochemical performance was evaluated by a Wonatec automatic battery cycler in a CR2016 type coin cell. The electrode was made into a slurry containing 80% by weight of active material, 10% by weight of conductive carbon black, and 10% by weight of polyvinylidene fluoride (PVDF) binder in N-methyl-2-pyrrolidone (NMP) as a solvent. Prepared. The aluminum foil current collector was applied as a doctor blade and dried at 120 ° C. for 12 hours in a vacuum oven. The coated cathode foil was pressed to form a uniform layer and punched in the form of a disk. In the argon-filled glovebox, use a composite electrode with metal lithium foil as the counter electrode, and dissolve 1M LiPF6 (99.99% of Aldrich) in ethylene carbonate / diethyl carbonate (EC / DEC, 1: 1 v / v) solution. Coin cells were made using the electrolyte. The cells were cycled galvanostatically compared to Li / Li + between 2 and 4.3V at various current densities at room temperature.

Electrochemical analysis of P123-LFP as cathode material in lithium ion batteries showed excellent high rate performance at 2C discharge rate and 20C charge rate without loss of capacity.

Claims (14)

In the method for producing a hybrid nanoparticle of LiFePO ₄ with carbon and lithium phosphate,
Use surfactants,
Carbonizing the surfactant through heat treatment under anoxic conditions. The method of claim 1,
The surfactant is a nonionic organic surfactant. The method of claim 1,
The surfactant is characterized in that both amphiphilic block copolymers, The method of claim 1,
The surfactant is a triblock copolymer (F108, P123) of polyethylene oxide and polypropylene oxide. 5. The method of claim 4,
The weight ratio of propylene oxide in the block copolymer is characterized in that 10 to 90% by weight. In the method for producing a hybrid nanoparticle of LiFePO ₄ with carbon and lithium phosphate,
LiFePO ₄ And mixing the precursor of lithium phosphate and the surfactant in a solvent;
Evaporating the solvent to obtain a powder; And
Heat-treating the powder in an oxygen-free atmosphere. The method according to claim 6,
LiFePO ₄ And LiNO ₃ , Fe (NO ₃ ) ₃ .9H ₂ 0 and H ₃ PO ₄ as a precursor of lithium phosphate. The method according to claim 6,
The surfactant is a nonionic organic surfactant. The method according to claim 6,
Wherein said surfactant is an amphiphilic block copolymer. The method according to claim 6,
The surfactant is a triblock copolymer of polyethylene oxide and polypropylene oxide. The method of claim 10,
The weight ratio of propylene oxide in the block copolymer is characterized in that 10 to 90% by weight. The method according to claim 6,
Oxygen-free atmosphere is a H ₂ / Ar mixed gas atmosphere, the heat treatment is characterized in that made at 600 ~ 800 ℃. Hybrid Nanoparticles of LiFePO ₄ with Carbon and Lithium Phosphate. A cathode material for a secondary battery comprising hybrid nanoparticles of LiFePO ₄ with carbon and lithium phosphate.

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