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Method Of Making Active Materials For Use In Secondary Electrochemical Cells

a secondary electrochemical cell and active material technology, applied in the field of nanocrystalline vpo4 precursors, can solve the problem that materials are not always economical to produ

Inactive Publication Date: 2007-07-12
VALENCE TECH INC
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0030] Specific benefits and embodiments of the present invention are apparent from the detailed description set forth herein below. It should be understood, however, that the detailed description and specific examples, while indicating embodiments among those preferred, are intended for purposes of illustration only and are not intended to limit the scope of the invention.

Problems solved by technology

Although these compounds find use as electrochemically active materials these materials are not always economical to produce.

Method used

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  • Method Of Making Active Materials For Use In Secondary Electrochemical Cells
  • Method Of Making Active Materials For Use In Secondary Electrochemical Cells
  • Method Of Making Active Materials For Use In Secondary Electrochemical Cells

Examples

Experimental program
Comparison scheme
Effect test

example 1

Preparation of VPO4

[0090] VPO4 was prepared according to the following reaction:

½ V2O5+(NH4)2HPO4+1.0 C→VPO4+2 NH3+3 / 2 H2O+CO

9.1 g V2O5, 13.2 g of (NH4)2HPO4 and 1.32 g of carbon (10% mass excess) were used. Carbon was added to the reaction mixture so that the V5+ in the V2O5 was reduced to V3+ in the product which is an example of carbothermal reduction. The excess carbon in the product helps act as a conducting agent in the vanadium phosphate electroactive materials produced therefrom, which improves the electrochemical properties of such electroactive materials.

[0091] It has been found that it is necessary to use a homogenous starting material. This can be achieved using high energy milling methods, which can include ball milling and micronizing. The sample prepared herein were prepared using McCrone micronizers to obtain the starting materials.

[0092] The VPO4 materials prepared herein were prepared at a number of different temperatures in the range from about 650° C. to abou...

example 2

Preparation of LiVPO4F using VPO4

[0094] LiVPO4 was prepared according to the following reaction:

LiF+VPO4→LiVPO4F

The LiF (2.6 g) and VPO4 (1.46 g) were mixed and micronized. The amount of LiF added is dependent on the amount of residual carbon present in the VPO4. The stoichiometric amount of LiF is added based on the above reaction. An allowance can be made for the amount of residual carbon left over from the V—P—O / C synthesis. This is normally about 3 weight percent. The mixture was then heated in the temperature range of about 600° to about 700° C. for up to about 1 hour. At temperatures in excess of 700° C., it is believed that VF3 sublimation occurs which leads to the formation of Li3V2(PO4)3 (LVP-nasicon).

[0095]FIG. 3 shows an example of a powder pattern obtained for a sample of LiVPO4F. Refinement of the XRD data for the LiVPO4F samples was carried out using the Rietveld method. H. M. Rietveld, J. Appl. Crystallograph, 2, (1969) 65. R. A. Young in “The Rietveld Method”, Cha...

example 3

[0100] An electrode active material comprising LiV1−xAlxPO4F was made according to the following reaction scheme:

(1−x)VPO4+x AlPO4+LiF →LiV1−xAlxPO4F

[0101] The LiF, VPO4 and AIPO4 were mixed and micronized in the required amounts. If for example x=0.2

0.8 VPO4+0.2 AlPO4+LiF→LiVo0.8Al0.2PO4F

Then 1.167 g of VPO4 were mixed with 0.244 g AlPO4 and 0.259 g LiF. The mixture was then heated in the temperature range 600-700° C. for up to 1 hour.

[0102] An electrode is made with 84% of the active material, 6% of Super P conductive carbon, and 10% poly vinylidene difluoride. A cell with that electrode as cathode and a lithium anode is constructed with an electrolyte comprising 1 M LiPF6 dissolved in 2:1 by weight mixture of ethylene carbonate:dimethyl carbonate.

[0103]FIG. 7 shows the X-ray powder patterns for samples of LiV1−xAlxPO4F. The results shown in FIG. 7 show that high quality samples can be prepared relatively easily.

[0104]FIG. 8 is a plot of Al content versus unit cell volume, obt...

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Abstract

The present invention provides for the preparation of an “optimized” VPO4 phase or V—P—O / C precursor. The VPO4 precursor is an amorphous or nanocrystalline powder. The V—P—O / C precursor is amorphous in nature and contains finely divided and dispersed carbon. Throughout the specification it is understood that the VPO4 precursor and the V—P—O / C precursor materials can be used interchangeably to produce the final vanadium phosphates, with the V—P—O / C precursor material being the preferred precursor. The precursors can subsequently be used to make vanadium based electroactive materials and use of such precursor materials offers significant advantages over other processes known for preparing vanadium phosphate compounds.

Description

[0001] This application is a continuation-in-part of U.S. patent application Ser. No. 11 / 277,746 filed Mar. 28, 2006, which claims priority from U.S. provisional patent application 60 / 729,932 filed Oct. 25, 2005, which claims priority from U.S. provisional patent application 60 / 666,132 filed Mar. 28, 2005.FIELD OF THE INVENTION [0002] The present invention relates to the novel preparation of a nanocrystalline VPO4 precursor and in another embodiment to an amorphous V—P—O / C precursor (or V—P—O-carbon composite material / precursor). The invention further relates to the use of this VPO4 precursor or V—P—O / C precursor in methods for making vanadium phosphate compounds. Such methods for making vanadium phosphates are beneficial in that the methods proceed at faster reaction rates and at lower temperatures then known methods for making vanadium phosphates. Such precursors also produce a purer product. The vanadium phosphate compounds so prepared are electroactive and are useful in making e...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): C01B25/37H01M4/136H01M4/58
CPCC01B25/45C01B25/455H01M4/136Y02E60/122H01M10/052H01M10/0525H01M2004/021H01M4/5825Y02E60/10B82Y40/00C01B25/26H01M4/04H01M4/58
Inventor BARKER, JEREMYGOVER, RICHARDBURNS, PAULBRYAN, AIDEN
Owner VALENCE TECH INC
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