CA2596239C - Lithium-based electrochemically active materials and preparation thereof - Google Patents

Abstract

The invention provides novel lithium-mixed metal materials which, upon electrochemical interaction, release lithium ions, and are capable of reversibly cycling lithium ions. The invention provides a rechargeable lithium battery which comprises an electrode formed from the novel lithium-mixed metal materials. Methods for making the novel lithium--mixed metal materials and methods for using such lithium--mixed metal materials in electrochemical cells are also provided. The lithium-mixed metal materials comprise lithium and at least one other metal besides lithium. Preferred materials are lithium-mixed metal phosphates which contain lithium and two other metals besides lithium.

Description

LITHIUM-BASED ELECTROCHEMICALLY ACTIVE MATERIALS AND
PREPARATION THEREOF

This is a divisional of Canadian Patent Application Seri_al. No. 2,460,875 filed on December 22, 2000, which is a divisional of Cariadian Patent Application Serial No.

2,394,318 filed on December 22, 2000.

Field of the Invention This invention relates to improved materials usable as electrode active materials and to their preparation.
Background of the Invention Lithium batteries are prepared from one or more lithium electrochemical cells containing electrochemically active (electroactive) materials. Such cells typically include an anode (negative electrode), a cathode (positive electrode), and an electrolyte interposed between spaced apart positive and negative electrodes. Batteries with anodes of metallic lithium and containing metal chalcogenide cathode active material are known. The electrolyte typically comprises a salt of lithium dissolved in one or more solvents, typically nonaqueous (aprotic) organic solvents. Other electrolytes are solid electrolytes typically called polymeric matrixes that contain an ionic conductive medium, typically a metallic powder or salt, in combination with a polymer that itself may be ionically conductive which is electrically insulating. By convention, during discharge of the cell, the negative electrode of the cell is defined as the anode.
Cells having a metallic lithium anode and metal chalcogenide cathode are charged in an initial condition. During discharge, lithium ions from the metallic anode pass through the liquid electrolyte to the electrochemical active (electroactive) materi-al of the cathode whereupon they release electr:i.cal- energy to an external circuit.
It has recently been suggesteci to replace the lithium metal anode with an insertion anode, such as a lithium metal chalcogenicie or lithiunl metal oxide.
Carbon anodes, Such as col:e anci graplii te, are also insertion materials. Such negative electrodes are used with lithiurn- containing insertion cathodes, in order to form an electroactive couple in a cell. Such cells, in an initial conclition, are not cl-iarged. In order to be used to deliver electrochemical energy, such cells must be charged in order to transfer lithiurn to the anode from the lithium- containing c<<thode. During discharge the lithium is trans ferrecl from the anocie bac}: to the cathode. During a:-;ub:.equent recharge, the lithium is transferrecl bac}: to the anode where it re-inserts. Upon subsequent charge and cli-charge, the lithiurn ions (Li') are transported between the electrodes. Such rechargeable batteries, having no free metallic species are called recharcJeable ion batteries or roc-}:ing chair batteries. See U.S. Patent Nos. -'-), ~18, 090; 4,464,447;
4, I94, 06?_; c-incl 5, 1'0, 21-1 .

Preferrecl positive electrode active niaterials include LiCoO,, LiMn_0.1, and LiNiO . The cobalt compounds are relatively expensive and the nickel compounds are difficult to synthesize. A relatively economical positive electr_ode is LiMn.O.1, for which methods of synthesis are known. 'I'he lithiuin cobalt oxicle (LiCoO2), the lithium manganose oxide (LiMn.O.,), ancl the lithium nickel oxide (LiNiO_) all have a common disacivantage in that the charge capacity of a cell comprising such cathodes suffers asignificant loss in capacity. That is, the initial capacity available (amp hours/gram) from LiMnzO,t, LiNiO; , and LiCoO i:, less than the -theoretical

3 capacity because sictnific._intly less than 1 atomic unit of lithium engages in the electrochemical reaction. Such an initial capacity value is significantly diminished during the first cycle operation and such capacity further diminishes on every successive cycle of operation. For LiNiO2 and LiCoO. only about 0.5 atomic: units of lithium is reversibly cycled during cell operation. Many attempts have been made to reduce capacity fading, for example, as described in U.S. Patent No. 4,928,834 by Nagaura et al. I-Iowever, the presently known and commonly used, alkali transition metal oxide compounds suffer from relatively low capacity. Therefore, there remains the difficulty of obtaining a lithium-containing electrode material having acceptable capacity without disadvantage of significant capacity loss when used in a cell.

4 Summary of the Invention The inventiori provides novel lithiuin-mixed metal materials which, upon electrochemical interaction, release lithium ions, and are capable of reversibly cycling lithium i_ons. The invention provides a rechargeable lithium battery which comprises an electrode formed from the novel lithium-mixed metal materials.
Methods for making the novel lithium-mixed metal materials and methods for using such lithium-mixed metal materials in electrochemical cells are also provided.
The lithium-mixed metal materials comprise lithium and at least one other metal besides lithium. Preferred materials are lithium-mixed metal phosphates which contain lithium and two other metals besides lithium.
Accordingly, the invention provides a rechargeable lithium battery which comprises an electrolyte; a first electrode having a compatible active material; and a second electrode comprising the novel materials. In one aspect, the novel materials are lithium-mixed metal phosphates which preferably used as a positive electrode active material, reversibly cycle lithium ions with the compatible negative electrode active material. Desirably, the lithium-mixed metal phosphate i::, represented by the nominal general formula Li.;MI,,MII,_(PQ),.. Such compounds include LiIMI,,MII1,PO4 and Li,MI;MII,,(PO.,) ,,; therefore, in an initial condition 0<_ a< 1 or 0< a S 3, respectively.
During cycling, x quantity of lithium is released where 0< x<_ a. In the general formula, the sum of b plus c is up to about 2. Specific examples are Li1MI,_yMIIYPO., ancl Li,MI__YMIIy,(PO.,) õ wherein "y" is defineci hereinafter.

In one aspect, MI and MIT are the same. In a preferred aspect, MI and MII are different from one J

another. At lea::;L one of MI and MII is ~in element capable of an oxidation state higher than that initially present in the lithium-rniYed meLal phosphate compound.

5 Correspondingly, at least orle of MI and MII has more than one oxidation state in the phosphate compound, and more than one oxidation state above the ground ;tate M . The term oxidation state and valerlce Jtate are used in the art interchangeably.
In another Jispect, both MI and MII may have more than one oxidation state anci both mi-ty be oxidizable from the state initially present in the phosphate compound. DesirEibly, MII is a metal or semi-metal having a+2 oxidation .:>tate, and is selected from Groups 2, 12 and 14 of the Periodic: Table. Desirably, MII is selected from non-transi tion metals L-tnci semi-metals. In one embodiment, MII has only orle oxidation state and is nonoxiclizable froin its o.vidation state in the lithium-mixed metal compound. In another embodirnent, MII has more than one oxidation state. I;xarnple, of semi-metals having more than one oxidation state are selenium and telluri_um; other noll-tran:;ition metals witli more than one oxidation sLate are tin anci lead. Prefer~tbly, MII is selecteci froin Mg (macrnesll1111) , Ca (calC1U111), Zn ( zinc) , Sr (strontium), Pb (le'ad), Cd (caclrniurn), Si-i ( tin) , Ba (bariunl), and Be (1)E?rylllLlm),and mixttlre:; thereof. . In another preferred aspect, MII is a metal having a +2 oxidation state ancl hcivine more thi-in one o::idation state, arld is oxidizable from iL:; oxiclaLion at,-lte :i.n l:i.thium-mixed metal compound.

Desir<<b1v, MI i.a selected f:rom Fe (iron), Co (cobalt), Ni (nic.l_el ) , Mn (manganese), Cu (copper), V
(vanadium), Sn (tin), Ti ( titalilurrt) , Cr (chromium), and

6 mixtures thereof. As can be seen, MI is preferably selected fronl the first row of transition metals and further includes tin, and MI preferably initially has a +2 oxidation state.

In one aspect, the product LiMI,_,.MIIYPOq may have an olivine structure and the product Li,MI,_;, (PO4), is a rhombohedral or monoclinic Nasicon structure. In another aspect, the term "nomi.nal formula" refers to the fact that the relative proportion of atomic species may vary slightly on the order of 2 percent to 5 percent, or more typically, 1 percent to 3 percent. In still another aspect, any portion of P (phosphorous) may be substituted by Si (silicon), S (sulfur), and/or As (arsenic); and any portion of 0 (oxygen) may be substituted by halogen, preferably F(fl.uor_ine). These aspects are also disclosed in U.S. Patent Application Serial Numbers 09/105,748 issued as U.S. 6,136,472 on October 29, 2000, 09/274,371 issued as U.S. 6,153,333 on November 28, 2000 and in U.S.
Patent No. 5,831,866 issued February 16, 1999; each of the listed applications and patents are co-owned by the assignee of the present invention.

The metal phosphate sare alternatively represented by the nominal general formulas such as Li1_KMI1_vMI I,, P0_, (0 i x ! 1), and Li,_.,MI _.,MI I;. ( PO,, ) 3 signifying capability Lo release and reinsert lithium.
The term "general" refers to a family of compounds, with M, x and y representing variations therein. The expressions 2-y and 1-y each signify that the relative amount of MI and MII may vary. In addition, as stated above, MI may be a mixture of inetal.s meeting the earlier stated criteria for MI. in addition, MII may be a mixture of inetal l ic elements meeti.nq the stated criteria

7 for MII. Preferably, where MII i_; a mixture, it is a mixture of 2 metallic elements; and where MI is a mixture, it is a mixtur.e of 2 metals. Preferably, each such metal and metallic element ha,, a+2 oxidation state S in the initial phosphate compound.

According to a preferred embodiment, the invention provides a compound represented by the nominal general formula Li,Fe,_. MõPO, wherein 0 < y < 1, t in aboutl 1, and M is at least one selected from the clroup consisting of Mg, Ca, Zn, Sr, Pb, Cd, Sn, Ba, Be, and mixtures thereof.
Another preferred embodiment of the invention is a compound having the nominal general formula LiaMII_yMIIyPO,j wherein MI is selected from the group consisting of Fe, V, Sn, Ti, Cr, and mixtures ther.eof, and MII is selected from the group consi s t inct of Mg, Ca, Zn, Sr, Pb, Cd, Sn, Ba, Be, and mixtures thereof, a is about 1, and wherein y is greater than zero and less than one.

Still another preferred embodiment of the invention is a compound having the nominal general formula Li,MII-YMIIYPOq wherein MI is at least one transition meta]. selected from Groups 4 to 11 inclusive of the Periodic Table and has a +2 valence state, MII is at least one metallic element which is selected from Groups 2, 12, and 11 of the Periodic Table and has a +2 valence state, a is about 1, and wherein 0 < y < 1, with the proviso that when MI is Co, Ni, or Mn, MII is not Ge, Mg or Zn, and with the proviso that when MI is Cu, MII is not Zn.

Another preferred embodiment of the invention is a compound having the nominal general formulji Li,MII_yMIIyPOq n wherein MI is selectecl from the gr.oup consisting of Fe, Co, Ni, Mn, Cu, V, Sn, Ti, Cr, cZncl 1Tl.l.xturE_'s thereof, and MII is selected from the cJroup consi~~ti.ng of Ca, Sr, Pb, Cd, Sn, Ba, Be, and mixtures thereof, a is I-rbout 1, and wherein y is gr.eaLer Ll-ian zero and less than orle.

Still another preferrecl ernbodiment of the invention is a compound having the nominal general formula Li,MI,_YMIIYPO, wherein MI is Sel.ected from the group consisting of Fe, Ni, Mn, V, Sn, Cr, and mixtures thereof, and MII is selected from the group consistincJ of Ca, Sr, Pb, Cd, Sn, Ba, Be, and mix.tures thereof, a is about 1, and wherein y is greater tlian zero and less than one.

Still anoLl-iei: preferred ernbodimenL of the invention is a compound having the riominal general formtila LiaMI,_yMIIYPO4 wherein MI is selected from the group consi-Iting of Fe, Cu, V, Sn, Ti, Cr, and mixtures thereof, ancl MII is selected from the group consistin(j of Mcj, Ca, Sr, Pb, Cd, Sn, Ba, Be, anci rnixtures thereof, a is about 1, and wher_ein y is greater than zero and lesr than one.

In another aspect of tl-ie present invention, there is provided, in a preferred embodinient, an electrode comprising an active material represented by the nominal general formula Li,MI,_,,MII:.PO., wherein MI is selected from the group consistinci of Fe, V, Sn, Ti, Cr, and mixtures thereof, and MII is selected from the group consisting of Mg, Ca, Zn, Sr, Pb, Ccl, Sn, Ba, L;e, and mi::ture s thereof, a is about 1, ancl wherein y is greaLer thatz : ero and less than one.

Another preferrecl embocliment of tl-le inventiorl is an electrode comprising an active matlerial which is a compound having the nomin.-i1 general fortnula LiaMI,_õMII,,PO, wherein MI is selected From the cJr(:)up con~:i.stincJ of Fe, Co, Ni, Mn, Cu, V, Sn, Ti, Cr, and rnixtures thereof, and MII is selected froin the group consisting of Ca, Sr, Pb, Cd, Sn, Ba, Be, and mixtures thereof, a is about 1, and wherein y is greater than zero and less than one.
Still another preferred embodimeiit of the invention is an electrode comprising an active material which is a compound having the noniinal general formula LiaMI,_YMIIYPOa wherein MI is selected from the group consisting of Fe, Ni, Mn, V, Sn, Ti, Cr, and mixtures thereof, and MII is selected from the group consisting of Ca, Sr, Pb, Cd, Sn, Ba, Be, and mixtures thereof, a is about 1, and wherein y is greater than zero anci less than one.

Another preferreci embodiment of the invention is an electrode comprising an active material which is a compound having the nominal general formula Li,MI,_,,MII7POq wherein MI is selected from the group consisting of Fe, Cu, V, Sn, Ti, Cr, and mixtures thereof, and MII is selected from the group consisting of Mg, Ca, Sr, Pb, Cd, Sn, Ba, Be, and mixtures thereof, a is about 1, and wherein y is greater than zero and less than one.

In another aspect of this invention there is provided a lithium ion battery; a preferred embodiment of this aspect is a lithium ion battery comprising:
a first electrode having an active material represented by the nominal general formula Li,Fe,_.;M.,PO;
wherein 0 < y < 1, a is about 1, and M is at least one selecteci from the group consisting of Mg, Ca, Zn, Sr, Pb, Cd, Sri, Ba, Be, and mixtures thereof;
a second electrode which is a counterelectrode to said first electrode; and an electrolyte between said electrodes.

Another preferred enlbodiment of this invention is a lithium ion battery coinprising:
a first electrode having an active material represented by the nominal general formula Li,MI,_ 5 YMIIYPO4 wherein MI is selected from the group consisting of Fe, V, Sn, Ti, Cr, and mixtures thereof, and MII is selected from the group consisting of Mg, Ca, Zn, Sr, Pb, Cd, Sn, Ba, Be, and mixtures thereof, a is about 1, and wherein y is 10 greater than zero and less than one;
a second electrode which is a counterelectrode to said first electrode; anci an electrolyte between said electrodes.

A further aspect of the preferred embodiment of this invention is a lithium ion battery comprising:
a first electrode having an active material which is a compound represented by the nominal general formula Li,MI,_,MII,,PO, wherein MI is at least one transition metal selected from Groups 4 to 11 inclusive of the Periodic Table and has a +2 valence state, MII is at least one metallic element which is selected from Groups 2, 12, and 14 of the Periodic Table and has a +2 valence state, a is about 1, and wherein 0 < y < 1, with the proviso that when MI is Co, Ni, or Mn, MII is not Ge, Mg or Zn;
a second electrode which is a counterelectrode to said first electrode; ancl an electrolyte between said electrodes.
A further preferred embodiment of this invention is a lithium ion battery comprisiizg:
a first electrode having an active material which is a compound having the nominal general formula LiaMI,_ ,,MIIyPOa wherein MI is selected from the group consisting of Fe, Co, Ni, Mn, Cu, V, Sn, Ti, Cr, and mixtures thereof, ancl MII is selected from the group consisting of Ca, Sr, Pb, Cd, Sn, Ba, Be, and mixtures thereof, a is about 1, and wherein y is greater than zero and less than one, a second electrode which is a counterelectrode to said first electrode; ancl an electrolyte between said electrodes.

A further embodiment of this inveiltion is a lithium ion battery comprising:
a first electrode having an active material which is a compound having the nominal general formula Li,MI,_yMIIYPO.l wherein MI is selected from the group consisting of Fe, Ni, Mn, V, Sn, Ti, Cr, and mixtures thereof, and MII is selecteci from the group consisting of Ca, Sr, Pb, Cd, Sn, Ba, Be, and mixtures thereof, a is about 1, and wherein y is greater than zero and less than one;
a second electrode which is a counterelectrode to said first electrode; and an electrolyte between said electrodes.
Another aspect of the preferred embodiment of this invention is a lithiuin lon battery comprising:
a first electrode having an active material which is a compound having the nominal general formula Li,MI,_ yMIIYPOa wherein MI is selected from the group consisting of Fe, Cu, V, Sn, Ti, Cr, and mixtures thereof, and MII is selected from the group consisting of Mcq, Ca, Sr, Pb,. Cd, Sn, Ba, Be, anci mixtures thereof, a is about 1, and wherein y is greater than zero and less than one;
a second electrocle which is a counterelectrode to said first electrode; and an electrolyte between said electrodes.

The active material of the counter electrode is any material compatible witli the lithium-mixed metal phosphate of the invention. Where the lithium-mixed metal phosphate is used as a positive electrode active material, metallic lithium, lithium-containing material, or non-lithium-containing material may be used as the negative electrode active inaterial. The negative electrode is desirably a nonmetallic insertion material.
Desirably, the negative electrode comprises an active material from the group consisting of metal oxide, particularly transition metal oxide, metal chalcogenide, carbon, graphite, and mixtures thereof. It is preferred that the anode active material comprises a carbonaceous material such as graphite. The litliium-mixed metal phosphate of the invention may also be used as a negative electrode material.

In another embodiment, the present invention provides a rnethoci of preparing a compound of the nominal general formula Li;MI,,MI I,_ ( POa ),, where 0 < a<_ 3; the sum of b plus c is greater than zero and up to about 2; and 0 < d 5 3. Preferred compounds include Li,MIr,MII,(POa) 3 where b plus c is about 2; and LiMI,,MII,..POa where b plus c is about 1. The inethoci comprises providing starting materials in particle form. The starting (precursor) materials include a lithium-containing compound, one or more metal containing compounds, a compound capable of providing the phosphate (PO4)-' anion, and carbon.
Preferably, the 1.ithium-containing compound is in particle form, and an example is lithium salt.
Preferably, the phosphate-containing anion compound is in particle form, and examples include metal phosphate salt and diammonium hydrogen phosphate (DAHP) ancl ammonium dihydrogen phosphate (ADHP). The lithium compound, one or more metal compounds, and phosphate compound are included in a proportion which provides the stated nominal general formula. The starting materials are mixed together with carbon, which is included in an amount sufficient to reduce the metal ion of one or more of the metal-containing starting materials without full reduction to an elemental metal state. Excess quantities of carbon and one or more other starting materials (i.e., 5 to 10% excess) may be used to enhance product quality.
A small amount of carbon, remaining after the reaction, functions as a conductive constituent in the ultimate electrode formulation. This is an advantage since such remaining carbon is very intimately mixed with the product active material. Accordingly, large quantities of excess carbon, on the order of 1009, excess carbon are useable in the process. The carbon present during compound formation is thought to be intimately dispersed throughout the precursor and product. This provides many advantages, including the enhanced conductivity of the product. The presence of carbon particles in the starting materials is also thought to provide nucleation sites for the production of the product crystals.

The starting materials are intimately mixed and then reacted together where the reaction is initiated by heat and is preferably conducted in a nonoxidizing, inert atmosphere, whereby the lithium, metal from the metal compound(s), and phosphate combine to form the LiõMIbMII,,(PO4),, product. Before reacting the compounds, the particles are intermingled to form an essentially homogeneous powder inixture of the precursors. In one aspect, the precursor powders are dry-mixed using a ball mill, such as zirconia media. Then the mixed powders are pressed into pellets. In another aspect, the precursor powders are mixed with a binder. The binder is selected so as to not inhibit reaction between particles of the powders. Therefore, preferred binders decompose or evaporate at a temperature less than the reaction temperature. Examples include mineral oils (i.e., glycerol, or C-18 hydrocarbon mineral oil) and polymers which decompose (carbonize) to form a carbon residue before the reaction starts, or which evaporate before the reaction starts. In still anotlzer aspect, intermingling is conducted by forming a wet mixture using a volatile solvent and therl the intermingled particles are pressed together in pellet form to provide goocl grain-to-grain contact.
Although it is desired that the precursor compounds be present in a proportion which provides the stated general formula of the product, the lithium compound may be present in an excess amount on the order of 5 percent excess lithium compared to a stoichiometric mixture of the precursors. And the carbon may be present at up to 100% excess compared to the stoichiometric amount. The method of the invention may also be used to prepare other novel products, and to prepare known products. A number of lithium compounds are available as precursors, such as litlliurn acetate (LiO0CCH3) , lithium hydroxide, lithium nitrate (LiNO,), lithium oxalate (Li2C204) , lithium oxide (Li:O), lithium phosphate (Li3PO4) , lithium dillydrogen phosphate (LiH_PO.,), lithium vanadate (LiV01) , and lithium carbonate (LiCO,) . The lithium carbonate is preferred for the solid state reaction since it has a very high melting point and commonly reacts with the other precursors before melting.
Lithium carbonate has a melting point over 600 C and it decomposes in the presence of the other precursors and/or effectively reacts with the other precursors before melting. In contrast, lithium 1lydroxide melts at about 400 C. At some reaction temperatures preferr.eci herein of over 450 C the litliium hydroxide will rnelt before any significant r.eaction with the other precursors occurs to an effective extent. This melting renders the reaction very difficult to control. In addition, anl-lydrous LiOH
is highly hygroscopic and a significant quantity of water is released during the reaction. Such water needs to be removed from the oven anci the resultant product may need 5 to be dried. In one preferrecl aspect, the solid state reaction made possible by the present invention is much preferred since it is conducted at temperatures at which the lithium-containing cornpound reacts with the other reactants before melting. Therefore, lithium hydroxide 10 is useable as a precursor in the method of the invention in combination with some precursors, particularly the phosphates. The methoci of the invention is able to be conducted as an econornical carbotllerinal-based process with a wide variety of precursors and over a relatively 15 broad temperature range.

The aforesaid precursor compounds (starting materials) are gerierally crystals, granules, and powders and are generally r.eferrecl to as being in particle form.
Although many types of phosphate salts are known, it is preferred to use diammonium hydrogen phosphate (NH4)2,HPO.1 (DAHP) or ammonium dihydrogen phosphate (NI-I4) H,PO.4 (ADHP) Both ADHP and DAIIP meet the preferred criteria that the precursors decompose in the presence of one another or react with one another before meltinq of such precursor.
Exemplary metal compounds are Fe_0õ Fe10" V,O~,, VOõ
LiVO3, NH4VOõ Mg (OH) _., Cao, MgO, Ca (OH) ;, MnO,, Mn'031 Mn3 ( PO,)õ CuO, SnO, Sn0_, TiO., Ti ,0õ Cr,Oõ PbO., PbO, Ba (oII)õ BaO, Cd (OH) .. In addition, some starting materials serve as both the source of metal ion and phosphate, such as FeP().1, Fe, ( POa )_, Zn, ( PO., ),, and Mg3 (P04)2 . Still others contain both lithium ion and phosphate such as Li,PO; ancl Lil1_PO,,. Other exemplary precursors are 1-i,PO.1 (phosphoric acid) ; and P,O~, (P4010) phosphoric oxide; anci HPO, meta phosphoric acid, which is a decomposition procluct of P_0.,. If it is clesired to replace any of the oxygen with a halogen, such as fluorine, the starting materials further include a fluorine conlpound such as LiF. If it is desired to replace any of the phosphorous with silicon, then the starting materials further include silicon oxide (SiO2).
Similarly, ammonium sulfate in the starting materials is useable to replace phosphorus with sulfur.

The startiiig materials are available from a number of sources_ The following are typical. Vanadium pentoxide of the formula V-,0.. is obtairiable from any number of suppliers including Kerr McGee, Johnson Matthey, or Alpha Products of Davers, Massachusetts.
Vanadium pentoxide has a CAS number of 1314-62-1. Iron oxide Fe1O, is a common and very inexpensive material available in powder form from the same suppliers. The other precursor materials meiitionecl above are also available from well known suppliers, such as those listed above.
The method of the invention may also be used to react starting materials in the presence of carbon to form a variety of other novel products, such as gamma-LiV20, and also to produce known products. I-Iere, the carbon functions to reduce nietal ion of a starting metal compound to provide a product containing such reduced metal ion. The method is particularly useful to also add lithium to the resultant product, which thus contains the metallic elenient ions, namely, the lithium ion and the other metal ion, thereby forming a mixed metal product.
An example is the reaction of vanadium pentoxide (V,O,) with lithium carbonate in the presence of carbon to form gamma-LiV20,. Here the starting metal ion V''.V'j is reduced to V'QV''' in the final product. A single phase gamma-LiV,O, product is not known to have been ciirectly and independently formed before.

As described earlier, it is desirable to conduct the reaction at a temperature where the lithium compound reacts before melting. The temperature should be about 400 C or greater, and desirably 450 C or greater, and preferably 500 C or greater, and generally will proceed at a faster rate at higher temperatures.
The various reactions involve production of CO or CO, as an effluent gas. The equilibrium at higher temperature favors CO formation. Some of the reactions are more desirably conducted at temperatures greater than 600 C;
most desirably greater than 650 C; preferably 700 C or greater; more preferably 750 C or greater. Suitable ranges for many reactions are about 700 to 950 C, or about 700 to 800 C.
Generally, the higher temperature reactions produce CO effluent anci the stoichiometry requires more carbon be used than the case where CO, effluent is produced at lower temperature. This is because the reducing effect of the C to CO, reaction is greater than the C to CO reaction. The C to CO, reaction involves an increase in carbon ox_idation state of +4 (from 0 to 4) and the C to CO reaction involves an increase in carbon oxidation state of +2 (from ground state zero to 2).
Here, liigher temperature generally refers to a range of about 650 C to about 1000 C and lower temperature refers to up to about 650 C. Temperatures higher than 1200 C
are not thought to be neecled.

In one aspect, the methoci of the invention utilizes the reclucing capabilities of carbon in a unique and controlled manner to produce desired products having structure and lithium content suitable for electrode active materials. The method of the invention makes it possible to procluce products containing lithium, metal and oxygen in an economical and convenient process. The ability to lithiate precursors, and change the oxidation state of a metal without causing abstraction of oxygen from a precursor is heretofore unexpected. These advantages are at least in part achieved by the reductant, carbon, having an oxide whose free energy of formation becomes more negative as temperature increases.
Such oxide of carbon is more stable at high temperature than at low temperature. This feature is used to produce products having one or more metal ions in a reduced oxidation state relative to the precursor metal ion oxidation state. The method utilizes an effective combination of quantity of carbon, time and temperature to produce new products and to produce known products in a new way.
Referring back to the discussion of temperature, at about 700 C both the carbon to carbon monoxide and the carbon to carbon dioxide reactions are occurring. At closer to 600 C the C to CO_ reaction is the dominant reaction. At closer to 800 C the C to CO
reaction is dominant. Since the reducing effect of the C
to C0, reaction is greater, the result is that less carbon is needeci per atomic unit of metal to be reduced.
In the case of carbon to carbon monoxide, each atomic unit of carbon is oxidized from ground state zero to plus 2. Thus, for each atomic unit of metal ion (M) which is being reduced by one oxidation state, one half atomic unit of carbon is required. In the case of the carbon to carbon dioxide reaction, one quarter atomic unit of carbon is stoichiometrically requireci for each atomic unit of metal ion (M) which is reduced by one oxidation state, because carbon goes from ground state zero to a plus 4 oxidation state. These same relationships apply for each such metal ion being reduced and for each unit reduction in oxiciation state desired.

It is preferred to heat the starting materials at a ramp rate of a f.raction of a degree to 10 C per minute and preferably about 2 C per minute. Once the desired reaction temperature is attained, the reactants (starting materials) are held at the reaction temperature for several hours. The heating is preferably conducted under non-oxidizing or inert gas such as argon or vacuum.
Advantageously, a reducing atmosphere is not required, although it may be used if desired. After reaction, the products are preferably cooled from the elevated temperature to ambient (room) temperature (i.e., 10 C to 40 C). Desirably, the cooling occurs at a rate similar to the earlier ramp rate, and preferably 2 C/minute cooling. Such cooling rate has been found to be adequate to achieve the clesired structure of the final product.
It is also possible to quench the products at a cooling rate on the order of about 100 C/minute. In some instances, such rapic3 cooling (quench) may be preferred.

The present invention resolves the capacity problem posed by widely used cathode active material. It has been found that the capacity and capacity retention of cells having the preferred active material of the invention are improved over conventional materials.
Optimized cells containing lithium-inixed metal phosphates of the invention potentially have performance improved over commonly used lithium metal oxide compounds.
Advantageously, the new method of making the novel lithium-mixed metal phosphate compounds of the invention is relatively economical anci readily adaptable to commercial production.

Another feature of one erribodiment of the invention includes an electrochemical cell or battery based on lithium-rnixeci metal phosphates. Still another feature is to pr_ovide an electrode active material which combines the advantages of good discharge capacity and capacity retention. It is also a ciesirable feature of the present invention to provide electrodes which can be manufactured economically. Yet another feature of one 5 embodiment is to provide a method for forming electrode active material which lends itself to commercial scale production for preparation of large quantities.

These and other objects, features, and 10 advantages will become apparent from the following description of the preferred embodiments, claims, and accompanying drawings.

Brief Description of the Drawings Figure 1 shows the results of an x-ray diffraction analysis, of the LiFePO., prepared according to the invention using CuKa radiation, A= 1.5405A.
Bars refer to simulated pattern from refined cell parameters, Space Group, SG = Pnma (62). The values are a= 10.2883A (0.0020), b = 5.9759A (0.0037), c = 4.6717A
(0.0012) 0.0072, cell volume = 287.2264A' (0.0685).
Density, p = 3.605 g/cc, zero = 0.452 (0.003). Peak at full width half maximum, PFWHM = 0.21. Crystallite size from XRD data = 704A.

Figure 2 is a voltage/capacity plot of LiFePO4-containing cathocle cycled with a lithium metal anode using constant current cycling at 0.2 milliamps per square centimeter in a range of 2.5 to 4.0 volts at a temperature of about 23 C. The cathode contained 19.0mg of the LiFePO4 active material, prepared by the method of the invention. The electrolyte comprised ethylene carbonate (EC) and dimethyl carbonate (DMC) in a weight ratio of 2:1 and included a 1 molar concentration of LiPF6 salt. The lithium-metal-phosphate containing electrode ancl the lithium metal counter electrode are maintained spaced apart by a glass fiber separator which is interpenetrated by the solvent and the salt.

Figure 3 shows multiple constant current cycling of LiFePO_, active material cycled with a lithium metal anode using the electrolyte as described in connection with Figure 2 and cyclecl, charge and discharge at 0.2 milliamps per square centimeter, 2.5 to 4.0 volts at two different temperature conditions, 23 C and 60 C. Figure 3 shows the excellent rechargeability of the lithium iron phosphate/lithium metal cell, and also L

shows the excellent cycling and specific capacity (mAh/g) of the active material.

Figure 4 shows the results of an x-ray diffraction analysis, of the LiFe,,..,Mg0 .,P0a prepared according to the invention, using CuKa racliation, 2~ _ 1.5405A. Bars refer to simulated pattern from refined cell parameters SG = Pnma (62). The values are a 10.2688A (0.0069), b= 5.9709A (0.0072), c = 4.6762A
(0.0054), cell volume = 286.7208A (0.04294), p = 3.617 g/cc, zero = 0.702 (0.003), PFWHM = 0.01, and crystallite = 950A.

Figure 5 is a voltage/capacity plot of LiFeo.,)Mgo,,P04-containing cathode cycled with a lithium metal anode using constant current cycling at 0.2 milliamps per square centimeter in a range of 2.5 to 4.0 volts. Other conditions are as described earlier with respect to Figure 2. The cathode contained 18.9mg of the LiFe0.9Mg0,,PO4 active material prepared by the method of the invention.

Figure 6 slzows multiple constant current cycling of LiFeo..,Mgo.,PO4 cycled with a litlzium metal anode using the electrolyte as described in connection with Figure 2 and cycled, charge and discharge at 0.2 milliamps per square centimeter, 2.5 to 4.0 volts at two different temperature conditions, 23 C anci 60 C. Figure 6 shows the excellent rechargeability of the lithium-metal-phosphate/litlzium metal cell, and also shows the excellent cycling and capacity of the cell.

Figure 7 is a voltage/capacity plot of LiFeo. Mgo.2PO4-containing cathode cyclecl with a lithium metal anode using constant current cycling at 0.2 milliamps per square centimeter in a range of 2.5 to 4.0 volts at 23 C. Other conditions are as described earlier with respect to Figure 2. The cathode contained 16mg of the LiFeo_OMgo,,POa active material prepared by the method of the invention.
Figure 8 shows the results of an x-ray diffraction analysis, of the LiFe,,..,Ca0.1PO~ prepared according to the invention, using CuKoc radiation, A=
1.5405A. Bars refer to simulateci pattern from refined cell parameters SG = Pnma (62). The values are a =
10.3240A (0.0045), b 6.0042A (0.0031), c= 9.G887A
(0.0020), cell volume = 290.6370A (0.1807), zero = 0.702 (0.003), p= 3.62 g/cc, PFWHM = 0.18, and crystallite =
680A.
Figure 9 is a voltage/capacity plot of Lireo.8Cao.2POa-containing cathode cycleci with a lithium metal anode using constant current cycling at 0.2 milliamps per square centimeter in a range of 2.5 to 4.0 volts at 23 . Other conditions are as described earlier with respect to Figure 2. The cathode contained 18.5mg of the LiFe0_PCa0__PO4 active material prepared by the method of the invention.

Figure 10 is a voltage/capacity plot of LiFeo_ Zno.2POa-containing cathode cycled with a lithium metal anode using constant current cycling at 0.2 milliamps per square centimeter in a range of 2.5 to 4.0 volts at 23 C. Other conciitions are as described earlier with respect to Figure 2. The cathode contained 18.9mg of the Lire0.,,Zn,,,_.PO., active material prepared by the method of the invention.

Figure 11 shows the results of an x-ray diffraction analysis of the gamma-Li V.,O,, (x = 1, gamma LiVZO5) prepared according to the invention using CuKoc radiation A= 1.5905A. The values are a = 9.687A (1), b = 3.603A (2), and c = 10.677A (3) ; phase type is gamma-LiXV20, (x = 1) ; symmetry is orthorhombic; and space group is Pnma.
Figure 12 is a voltage/capacity plot of gamma-LiV,O;-containing cathode cycled with a lithium metal anode using constant current cycling at 0.2 milliamps per square centimeter in a range of 2.5 to 3.8 volts at 23 C. Other conditions are as described earlier with respect to Figure 2. The cathode contained 21mg of the gamma-LiV205 active material prepared by the method of the invention.

Figure 13 is a two-part graph based on multiple constant current cyclii7g of gamma-LiV,O~, cycled with a lithium metal anode using the electrolyte as described in connection with Figure 2 and cycled, charge and discharge at 0.2 milliamps per square centimeter, 2.5 to 3.8 volts. In the two-part graph, Figure 13 shows the excellent reclzargeability of the lithium-metal-oxide/lithium metal cell. Figure 13 shows the excellent cycling and capacity of the cell.

Figure 14 shows the results of an x-ray diffraction analysis of the Li,V,(POa), prepared according to the invention. The analysis is based on CuKcx radiation, A= 1.5405A. The values are a = 12.184A (2), b= 8.679A (2), c = 8.627A (3), and 90.457 (4).
Figure 15 shows the results of an x-ray diffraction analysis of Li,V_(POa), prepared according to a method described in U.S. Patent No. 5,871,866. The analysis is based on CuKa radiation, X = 1.5405A. The values are a = 12.155A (2), b = 8.711A (2), c 8.645A

(3) ; the angle beta is 90. 17 5(6) ; syrnmetry is Monoclinic; and space group is P2,/n.

Figure 16 is an EVS (Electrochemical Voltage 5 Spectroscopy) voltage/capacity profile for a cell with cathode material formed by the carbothermal reduction method of the invention. The cathode material is 13.8mg of Li3V, (POa) ,. The cell includes a lithiurn metal counter electrode in an electrolyte comprising ethylene carbonate 10 (EC) and dimethyl carbonate (DMC) in a weight ratio of 2:1 and including a 1 molar concentration of LiPF6 salt.
The lithium-metal-phosplzate containing electrode and the lithium metal counter electrode are maintained spaced apart by a fiberglass separator whicli is interpenetrated 15 by the solvent and the salt. The conditions are 10 mV
steps, between about 3.0 and 4.2 volts, and the critical limiting current density is less than or equal to 0.1 mA/ cm'.

20 Figure 17 is an EVS differential capacity versus voltage plot for the cell as described in connection with Figure 16.

Figure 18 shows multiple constant current 25 cycling of LiFeo,,MgO._POa cycled with a lithium metal anode using the electrolyte as described in connection with Figure 2 and cycled, charge and discharge at 0.2 milliamps per square centimeter, 2.5 to 9.0 volts at two different temperature conclitions, 23 C and 60 C. Figure 18 shows the excellent rechargeability of the lithium-metal-phosphate/lithium metal cell, and also shows the excellent cycling and capacity of the cell.

Figure 19 is a graph of potential over time for the first four complete cycles of the LiMgO.1FeO.9PO4/MCMB
graphite cell of the invention.

Figure 20 is a two-part graph based on multiple constant current cycling of LiFe,,..,Mgõ=,PO.1 cycled with an MCMB graphite anode using the electrolyte as described in connection with Figure 2 ancl cycled, charge and discharge S at 0.2 milliamps per square centimeter, 2.5 to 3.6 volts, 23 C and based on a C/10 (10 hour) rate. In the two-part graph, Figure 20 shows the excellent rechargeability of the lithium-metal-phosphate/graphite cell. Figure 20 shows the excellent cycling and capacity of the cell.

Figure 21 is a graph of potential over time for the first three complete cycles of the gamma-LiV~O;/MCMII
graphite cell of the invention.
Figure 22 is a diagrammatic representation of a typical laminated lithium-ion battery cell structure.
Figure 23 is a diagrammatic representation of a typical multi-cell battery cell structure.

Detailed Description of the Preferred Embodiments The present invention provides lithium-mixed metal-phosphates, which are usable as electrode active materials, for lithiurn (Li') ion removal and insertion.
Upon extraction of the lithium ions from the lithium-mixed-metal-phosphates, significant capacity is achieved.
In one aspect of the invention, electrochemical energy is provided when coinbined with a suitable counter electrode by extraction of a quantity x of lithiurn from lithium-mixed-metal-phosphates Li,,_,.MI,,MII,.(PO,,),,. When a quantity x of lithium is removed per formula unit of the lithium-mixed-metal phosphate, metal MI is oxidizecl. In another aspect, metal MII is also oxidized. Therefore, at least one of MI and MII is oxidizable from its initial condition in the phosphate compound as Li is removed.
Consider the following which illustrate the mixed metal compounds of the irlvention: LiFe,_õSn,PO.,, has two oxidizable elements, Fe and Sn; in contrast, LiFe1_,,MgyPO,1 has one oxidizable metal, the metal Fe.
In another aspect, the invention provides a lithium ion battery which comprises an electrolyte; a negative electrode having an insertion active material;
and a positive electrode comprising a lithium-mixed-metal-phosphate active material characterized by an ability to release lithium ion, for insertion into the negative electrocie active material. The lithium-mixed-metal-phosphate is desirably represented by the nominal general formula Li,,MI,,MII,(POa),,. Although the metals MI
and MII may be the same, it is preferred that the metals MI and MII are different. Desirably, in the phosphate compound MI is a metal selected from the group: Fe, Co, Ni, Mn, Cu, V, Sn, Ti, Cr and rnixtures thereof, and MI is most desirably a transition metal or mixture thereof selected from said group. Most preferably, MI has a +2 valence or oxidation state.

In another aspect, MII is selected from Mg, Ca, Zn, Sr, Pb, Cd, Sn, Ba, Be, and mixtures thereof. Most preferably, MII
has a +2 valence or oxidation state. The lithium-mixed-metal-phosphate is preferably a compound represented by the nominal general formula Li-_xMI,,MII, (PO4),,, signifying the preferred composition and its capability to release x lithium.
Accordingly, during cycling, charge and discharge, the value of x varies as x greater than or equal to 0 and less than or equal to a. The present invention resolves a capacity problem posed by conventional cathode active materials. Such problems with conventional active materials are described by Tarascon in U.S.
Patent No. 5, 425, 932, using LiMn1O,, as an example. Similar problems are observed with LiCoOZ, LiNiO2, and many, if not all, lithium metal chalcogenide materials. Other patents e.g.US
5, 869, 208, 5, 882, 821, 5, 670, 273, etc. reference or disclose electrodes, both cathode and anode, which contain the LiCoO2, LiMn.04 and LiNiOZmaterials, or are used in combination with other electrode compositions. Such prior art is representative of coiled electrodes, in which the cathode or anode (as the case may be) is constructed according to conventional techniques with cathodes having a film of a foil or metal wire net with a thickness of e.g. 5 pm - 100 pm. Other prior art also teaches 10-200 pm of film thickness for various types of batteries, e.g.
US 5,741,472. Ttie present invention demonstrates that significant capacity of the cathode active material is utilizable and maintained.
A preferred novel procedure for forming the lithium-mixed-ttiet'al-phosphate LiaMI~MII,(POQ),, compound active material will now be described. In addition, the preferred novel procedure is also applicable to formation of other lithium metal compounds, and will be described as such. The basic procedure will be described with reference to exemplary starting materials but is not limited thereby. The basic process comprises conducting a reaction between a lithium compound, preferably lithium carbonate (LizCO3)1 metal compound(s), for example, vanadium pentoxide (V205), iron oxide (Fe203), and/or manganese hydroxide, and a phosphoric acid derivative, preferably the phosphoric acid ammonium salt, diammonium hydrogen phosphate, (NH., ) H( PO., ). Each of the precursor I~

starting materials are available from a number of chemical outfits incluciing Aldrich Chemical Company and Fluka. Using the method described herein, LiFePO.1 and LiFea.,Mgo,,POa, Li.V_ (PO.,) , were prepared with approximately a stoichiometric amount of Li,COõ the respective metal compound, and (NH.,).HPOa. Carbon powder was included with these precursor materials. The precursor materials were initially intimately mixed and dry ground for about 30 minutes. The intimately mixecl compounds were then pressed into pellets. Reaction was conducted by heating in an oven at a preferred ramped heating rate to an elevated temperature, and held at such elevated temperature for several hours to complete formation of the reaction product. The entire reaction was conducted in a non-oxidizing atmosphere, under flowing pure argon gas. The flow rate will depend upon the size of the oven and the quantity needed to maintain the atmosphere. The oven was perniitted to cool down at the end of the reaction period, where cooling occurred at a desired rate under argon. Exemplary and preferred ramp rates, elevated reaction temperatures and reaction times are described herein. In one aspect, a ramp rate of 2 /minute to an elevated temperature in a range of 750 C
to 800 C was suitable along witli a dwell (reaction time) of 8 hours. Refer to Reactions 1, 2, 3 and 4 herein. In another variation per Reaction 5, a reaction temperature of 600 C was used along with a dwell time of about one hour. In still another variation, as per Reaction 6, a two-stage heating was conducted, first to a temperature of 300 C and then to a temperature of 850 .

The general aspects of the above synthesis route are applicable to a variety of starting materials.
Lithium-containing compounds include Li_0 (lithium oxide), LiH_PO.1 (lithiuril hydrogen phosphate), LizC204 (lithium oxalate), LiOH (lithium hyciroxide), LiOH.H20 (lithium hydroxide monohydride), and LiHCO3 (lithium hydrogen carbonate). The metal compounds(s) are reduced in the presence of the reducing agent, carbon.
The same considerations apply to other lithium-metal- and 5 phosphate-containing precursors. The thermodynamic considerations such as ease of reduction, of the selected precursors, the reaction kinetics, and the melting point of the salts will cause adjustment in the general procedure, such as, amount of carbon reducing agent, and 10 the temperature of reaction.

Figures 1 through 21 which will be described more particularly below show characterization data and capacity in actual use for the cathode materials 15 (positive electrodes) of the invention. Some tests were conducted in a cell comprising a lithium metal counter electrode (negative electrode) and other tests were conducted in cells having a carbonaceous counter electrode. All of the cells had an EC:DMC-LiPI't 20 electrolyte.

Typical cell configurations will now be described with r_eference to Figures 22 and 23; and such battery or cell utilizes the novel active material of the 25 invention. Note that the preferred cell arrangement described here is illustrative and the invention is not limited thereby. Experiments are often performed, based on full and half cell arrangements, as per the following description. For test purposes, test cells are often 30 fabricated using lithium metal electrodes. When forming cells for use as batteries, it is preferreci to use an insertion positive electrode as per the invention and a graphitic carbon negative electrode.

A typical laminated battery cell structure 10 is depicted in Figure 22. It comprises a negative electrode side 12, a positive electrode side 14, and an electrolyte/separator 16 there between. Negative electrode side 12 includes current collector 18, and positive electrode side 14 includes current collector 22.
A copper collector foil 18, preferably in the form of an open mesh grid, upon which is laid a negative electrode membrane 20 comprising an insertion material such as carbon or graphite or low-voltage lithium insertion compound, dispersed in a polymeric binder matrix. An electrolyte/separator film 16 membrane is preferably a plasticized copolymer. This electrolyte/separator preferably comprises a polyrneric separator and a suitable electrolyte for ion transport. The electrolyte/separator is positioned upon the electrode element and is covered with a positive electrode membrane 24 comprising a composition of a finely divided lithium insertion compound in a polymeric binder matrix. An aluminum collector foil or grid 22 completes the assembly.
Protective bagging material 40 covers the cell and prevents infiltration of air and moisture.

In another embodiment, a multi-cell battery configuration as per Figure 23 is prepared with copper current collector 51, negative electrode 53, electrolyte/separator 55, positive electrode 57, and aluminum current collector 59. Tabs 52 and 58 of the current collector elements form respective terminals for the battery structure. As used herein, the terms "cell"
and "battery" refer to an individual cell comprising anode/electrolyte/cathode and also refer to a multi-cell arrangement in a stack.

The relative weight proportions of the components of the positive electrode are generally: 50-90% by weight active material; 5-30'l, carbon black as the electric conductive diluent; and 3-20'e" binder chosen to hold all particulate materials in contact with one another without degrading ionic conductivity. Stated ranges are not critical, and the amount of active material in an electrocie may range from 25-95 weight percent. The negative electrode comprises about 50-95%
by weight of a preferred graphite, with the balance constituted by the binder. A typical electrolyte separator film comprises approximately two parts polymer for every one part of a preferred fumed silica. The conductive solvent comprises any number of suitable solvents and salts. Desirable solvents and salts are described in U.S. Patent Nos. 5,643,695 and 5,418,091.
One example is a mixture of EC:DMC:LiPI'c. in a weight ratio of about 60:30:10.
Solvents are selected to be used individually or in mixtures, and include dirnethyl carbonate (DMC), diethylcarbonate (DEC), dipropylcarbonate (DPC), ethylmethylcarbonate (EMC), ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate, lactones, esters, glymes, sulfoxides, sulfolanes, etc. The preferred solvents are EC/DMC, EC/DEC, EC/DPC and EC/EMC.
The salt content ranges from 5';', to 6501. by weight, preferably from 8;; to 35"i, by weight.
Those skilled in the art will understand that any number of inethocls are used to form films from the casting solution using conventional meter bar or doctor blade apparatus. It is usually sufficient to air-dry the films at moderate temperature to yield self-supporting films of copolymer composition. Lamination of assembled cell structures is accomplished by conventional means by pressing between metal plates at a temperature of about 120-160 C. Subsequent to lamination, the battery cell material may be stored either with the retained plasticizer or as a dry sheet after extraction of the plasticizer with a selective low-boiling point solvent.
The plasticizer extraction solvent is not critical, and methanol or ether are often used.

Separator membrane element 16 is generally polymeric and prepared from a composition comprising a copolymer. A preferred composition is the 75 to 92%
vinylidene fluoride with 8 to 2570 hexafluoropropylene copolymer (available commercially from Atochem North America as KYNAR FLEX"') and an organic solvent plasticizer. Such a copolymer composition is also preferred for the preparation of the electrode membrane elements, since subsequent laminate interface compatibility is ensured. The plasticizing solvent may be one of the various organic compounds commonly used as solvents for electrolyte salts, e.g., propylene carbonate or ethylene carbonate, as well as mixtures of these compounds. Higher-boiling plasticizer compounds such as dibutyl phthalate, dimethyl phthalate, diethyl phthalate, and tris butoxyethyl phosphate are particularly suitable.
Inorganic filler acijuncts, such as fumed alumina or silanized fumed silica, may be used to enhance the physical strength and melt viscosity of a separator membrane and, in some compositions, to increase the subsequent level of electrolyte solution absorption.

In the construction of a lithium-ion battery, a current collector layer of aluminum foil or grid is overlaid with a positive electrode film, or membrane, separately prepared as a coated layer of a dispersion of insertion electrode composition. This is typically an insertion compound such as LiMn,O., (LMO) , LiCoO,, or LiNiOz, powder in a copolymer matrix solution, which is dried to form the positive electrode. An electrolyte/separator membrane is formed as a dried coating of a composition comprising a solution containing VdF:HFP copolymer and a plasticizer solvent is then overlaid on the positive electrode film. A negative electrode membrane formecl as a dried coating of a powdered carbon or other negative electrode material dispersion in a VdF:HFP copolymer matrix solution is similarly overlaid on the separator membrane layer. A
copper current collector foil or grid is laid upon the negative electrode layer to complete the cell assembly.
Therefore, the VdF:HFP copolymer composition is used as a binder in all of the major cell components, positive electrode film, negative electrode film, and electrolyte/separator membrane. The assembled components are then heated under pressure to achieve heat-fusion bonding between the plasticized copolymer matrix electrode and electrolyte components, and to the collector grids, to thereby form an effective laminate of cell elements. This produces an essentially unitary and flexible battery cell structure.

Examples of forming cells containing metallic lithium anode, insertion electrodes, solid electrolytes and liquid electrolytes can be found in U.S. Patent Nos.
4, 668, 595; 4, 830, 939; 4, 935, 317; 4, 990, 413; 4, 792, 504;
5,037,712, 5, 262, 253; 5, 300, 373; 5, 435, 054; 5, 463, 179;
5,399,447; 5,482,795 and 5,411,820. Note that the older generation of cells contained organic polymeric and inorganic electrolyte matrix materials, with the polymeric being most preferred. The polyethylene oxide of 5,411,820 is an example. More modern examples are the VdF:HFP polymeric matrix. Examples of casting, lamination and formation of cells using VdF:HFP are as described in U.S. Patent Nos. 5,418,091; 5,460,904;
5, 456, 000; and 5, 540, 741; assigned to Bell Communications Research.

As described earlier, the electrochemical cell operated as per the invention, may be prepared in a variety of ways. In one embodiment, the negative electrode may be metallic lithium. In more desirable 5 embodiments, the negative electrode is an insertion active material, such as, metal oxides and graphite.
When a metal oxide active material is used, the components of the electrode are the metal oxide, electrically coiiductive carbon, and binder, in 10 proportions similar to that described above for the positive electrode. In a preferred embodiment, the negative electrode active material is graphite particles.
For test purposes, test cells are often fabricated using lithium metal electrodes. When forming cells for use as 15 batteries, it is preferred to use an insertion metal oxide positive electrode and a graphitic carbon negative electrode. Various methods for fabricating electrochemical cells and batteries and for forming electrode components are described herein. The invention 20 is not, however, limited by any particular fabrication method.

Formation of Active Materials EXAMPLE I

Reaction 1 (a) . LiFePO., formed from rePO, FePO4 + 0.5 Li,CO, + 0.5 C -> LiI'ePO.1 + 0.5 C0, , 0.5 CO
(a) Pre-mix reactants in the following proportions using ball mill. Thus, 1 mol FePO.4 150.82g 0.5 mol Li_C0,t 36.95g 0.5 mol carbon 6.Og (but use 100',; excess carbon -> 12.OOg) (b) Pelletize powder mixture (c) Heat pellet to 750 C at a rate of 2 /minute in flowing inert atmosphere (e.g. argon). Dwell for 8 hours at 750 C under argon.

(d) Cool to room temperature at 2 /minute under argon.

(e) Powderize pellet.

Note that at 750 C this is predominantly a CO
reaction. This reaction is able to be conducted at a temperature in a range of about 700 C to about 950 C in argon as shown, and also under other inert atmospheres such as nitrogen or vacuum.
EXAMPLE II

Reaction 1(b) . LiFePO.7 formed from Fe-.O00.5 Fe2O3 + 0.5 Li_CO, +(NHa),HPO4 + 0.5 C> LiFePOa +
0.5 C0, + 2 NII, + 3/2 I-i_O + 0.5 CO
(a) Premix powders in the following proportions 0.5 mol Fe,O, 79.85g 0.5 mol Li_C0, 36.95g 1 mol (NH4),HPOa 132 . 06g 0.5 mol carbon 6.OOg (use 100", excess carbon -> 12.OOg) (b) Pelletize powder mixture (c) Heat pellet to 750 C at a rate of 2 /minute in flowing inert atmosphere (e.g. argon). Dwell for Q hours at 750 C under argon.
(d) Cool to room temperature at 2 /minute under argon.

(e) Powderize EXAMPLE III

Reaction 1(c) . LiFePO4 - from Fe,(PO.,) Two steps:

Part I. Carbotllermal preparation of Fe, (P04)2 3/2 Fe2O3 + 2(NH.,) _HPOa + 3/2 C -> Fe3(PO.,): +
3/2 Co -t- 4NH, + 5/2 H,O
(a) Premix reactants in the following proportions 3/2 mol Fe,O2239.54g 2 mol (NHa)_ HPOa 269.12g 3/2 mol carbon 18.OOg (use 100% excess carbon -> 36.OOg) (b) Pelletize powder mixture (c) Heat pellet to 800 C at a rate of 2 /minute in flowing inert atmosphere (e.g. argon). Dwell for 8 hours at 750 C under argon.

(d) Cool to room temperature at 2 C/minute under argon.
(e) Powderize pellet.

Part II. Preparation of LirePO4 from the Fe, (P04) :!of Part I.
Li3PO4 + Fe3(POy)2 -4 LiFePOq (a) Premix reactants in the following proportions 1 mol Li,PO4 115.79g 1 mol Fe, (P0;) -= 357. 98g (b) Pelletize powder mixture (c) Heat pellet Lo 750 C at a rate of 2 /minute in flowing inert atmosphere (e.g. argon). Dwell for 8 hours at 750 C under argon.

(d) Cool to room temperature at 2 C/ininute under argon.

(e) Powderize pellet.
EXAMPLE IV

Reaction 2 (a) . LiFeõ_.,Mg,,.1PO4 (LiFe1_.,MgYPO.1) formed from FePO4 0.5 Li2CO3 + 0. 9 FePOa + 0. 1 Mg (OH) ,+ 0. 1(NH,)2HPOa +
0.45C -> LiFeo.,,Mg1,.,PO4 + 0.5C0-. + 0.45C0 + 0.2NH, +
0.25 H,0 IS
(a) Pre-mix reactants in the following proportions 0.50 mol Li_C0~ = 36.95g 0.90 mol FePO., = 135.74g 0.10 mol Mg(OH)2 = 5.83g 0.10 mol (NH4) _HPO4 = 1.32g 0.95 mol carbon = 5.40g (use 100 excess carbon -> 10.80g) (b) Pelletize powder mixture (c) Heat to 750 C at a rate of 2 /minute in argon.
Hold for 8 hours dwell at 750 C in argon (d) Cool at a rate of 2 /minute (e) Powderize pellet.

EXAMPLE V

Reaction 2(b) . LiFeo..,Mg1,.,PO4 (LiFe,_.,,Mg,,POa) formed from Fe203 5 0.50 Li:CO, + 0.45 Fe-.O, + 0.10 Mg (OH),+(NH4),HP04 +
0.45C -> Li Fe(,,,,Mg(,. 1 PO4 + 0. 5 CO_ + 0. 4 5 Co + 2 NH3 +
1. 6 H,0 10 (a) Pre-mix reactants in following ratio 0.50 rnol Li_CO> = 36.95g 0.45 mol Fe~O, = 71.86g 0.10 mol Mg(OH)-. = 5.83g 15 1.00 mol (NH4 )_HPOa = 132.06g 0.45 mol carbon = 5.40g (use 10006 excess carbon -> 10.80g) 20 (b) Pelletize powder mixture (c) Heat to 750 C at a rate of 2 /minute in argon.
Hold for 8 hours dwell at 750 C in argon 25 (d) Cool at a rate of 2 /minute (e) Powderize pellet.

EXAMPLE VI

Reaction 2(c) . LiI'e0,..,Mgõ_1PO., (LiFe,_,,MgYPOq) formed from LiH2PO.4 1. 0 LiH2PO4 + 0. 45 F'e=.03 + 0. 10 Mg (OH) _+ 0. 45C ->
LiFea.9)Mgo.1PO., + 0.45 CO + 1.1 H,0 (a) Pre-mix reactants in the following proportions 1.00 mol LiH_P0; = 103.93g 0.45 mol Fe_0, = 71.86g 0.10 mol Mg(OH)_ - 5.83g 0.45 mol carbon = 5.40g (use 10000 excess carbon -> 10.80g) (b) Pelletize powder mixture (c) Heat to 750 C at a rate of 2 /minute in argon.
Hold for 8 hours dwell at 750 C in argon (d) Cool at a rate of 2 /minute (e) Powderize pellet.

EXAMPLE VII

Reaction 3. Formation of LiFe,,..,Ca,,.,PO,, (LiI'e,_,,CaYP04) from Fe,O,.

0.50 Li,CO3 + 0. 45 re,0, + 0.1 Ca (OH) :+(NH,,) 2HP04 +
0.45C -> LiFe,,.,,Cao1,PO4 + 0.5 C0, + 0.45 CO + 2 NI-13 +
1 . 6 1-I, 0 (a) Pre-mix reactants in the following proportions 0.50 mol Li,CO, = 36.95g 0.45 mol Fe_03 = 71.86g 0.10 mol Ca(OH)_ = 7.41g 1.00 mol (NHa) ,HPOa = 132.06g 0.45 mol carbon = 5.4Og (100% excess carbon > 10.80g) (b) Pelletize powder mixture (c) Heat to 750 C at a rate of 2 /minute in argon.
Iiold for 8 hours dwell at 7SO C in argon (d) Cool at a rate of 2 /minute (e) Powderize pellet.
EXAMPLE VIII
Reaction 4. Formation of LiFer0..,Zn1;,,POa (LiFe,_yZn,POa) from Fe_0,.
0.50 LiZCO3 + 0.45 Fe,O, + 0.033 Zn, (P04) ,+
0. 933 (NH4 )2HPOa + 0.45 C> Li FeO,.,Zn,. IPOa + 0. 50 C02 +
0.95 CO -E- 1.866 NH, + 1.2 H_0 Pre-mix reactants in the following proportions 0.50 inol Li,CO, = 36.95g 0.45 mol Fe,O3 = 71.86g 0.033 mol Zn,(P04): = 12.74g 0.933 mol (NH4) _HPO4 = 123.21g 0.45 mol carbon = 5.40g (1000t excess carbon -> 10.80g) (b) Pelletize powder mixture (c) I-Ieat to 750 C at a rate of 2 /minute in argon.
Hold for 8 hours dwell at 750 C in argon (d) Cool at a rate of 2 /minute (e) Powderize pellet.

EXAMPLE IX

Reaction 5. Formation of gamma-LiV,O., (Y) V205 + 0.5 Li,CO, + 0.25 C -> LiV=.0~, + 3/4 CO2 (a) Pre-mix alpha V,Os, Li?CO, and Shiwinigan Black (carbon) using ball mix with suitable media.
Use a 25; . weight excess of carbon over the reaction amoutits above. For example, according to reaction above:

Need: 1 mol V,O" 181.88g 0.5 mol Li.CO3, 36.95g 0.25 mol carbon 3.OOg (but use 25"6 excess carbon > 3.75g) (b) Pelletize powder mixture (c) I-Ieat pellet to 600 C in flowing argon (or other inert atmosphere) at a heat rate of approximately 2 /minute. Hold at G00 C for about 60 minutes.

(d) Allow to cool to room temperature in argon at cooling rate of about 2 /minute.

(e) Powderize pellet using mortar and pestle This reaction is able to be conducted at a temperature in a raizge of about 900 C to about 650 C in argon as shown, and also under other inert atmospheres such as nitrogen or vacuum. This reaction at this temperature range is primarily C> CO,. Note that the reaction C> CO primarily occurs at a temperature over about 650 C (HT, high temperature); and the reaction C ->
CO2 primarily occurs at a temperature of under about 650 C (LT, low temperature) . The reference to about 650 C is approximate and the designation "primarily"
refers to the predominant reaction thermodynamically favored although the alternate reaction may occur to some extent.

EXAMPLE X

Reaction 6. Formation of Li.V_ (PO,,) :
VZO, + 3/2 Li,CO3 + 3(NHa) ,HP0.4 a- C-> Li3V-. (PO4) 3 + 2 CO
+ 3/2 CO_ 4- 6 NH3 + 9/2 N.0 (a) Pre-mix reactants above using ball mill with suitable mecdia. Use a 257. weight excess of carbon. Thus, 1 mol V_O.. 181.88g 3/2 mol Li_C03 110. B9g 3 mol (NH4)_HP04 396. 1Bg 1 mol carbon 12.01g !f (but use 25"0 excess carbon -> 15.O1g) (b) Pelletize powder mixture 5 (c) Heat pellet at 2 /minute to 300 C to remove C0.
(from Li,CO3) and to remove NHõ 11,0. Heat in an inert atmosphere (e.g. argon). Cool to room temperature.

10 (d) Powderize and repelletize (e) Heat pellet in inert atmosphere at a rate of 2 C/minute to 850 C. Dwell for 8 hours at 850 C
15 (f) Cool to room teinperature at a rate of 2 /minute in argon.

(e) Powderize 20 This reaction is able to be conducted at a temperature in a range of about 700 C to about 950 C in argon as shown, and also under other inert atmospheres such as nitrogen or vacuum. A reaction temperature greater than about 670 C ensures C -> CO reaction is 25 primarily carried out.
Characterization of Active Materials and Formation and Testing of Cells 30 Referring to Figure 1, the final product LiFePO41 preparecl from Fe-.0, metal compound per Reaction 1(b), appeared brown/black in color. This olivine material product included carbon that remained after reaction. Its CuKoc x-ray diffraction pattern contained 35 all of the peaks expected for this material as shown in Figure 1. The pattern evident in Figure 1 is consistent with the single phase olivine phosphate, LiFePO4. This is evidenced by the position of the peaks in terms of the scattering angle 2 0(theta), x axis. The x-ray pattern showed no peaks due to the presence of precursor oxides indicating that the solid state reaction is essentially entirely completed. Here the space group SG = pnma (62) and the lattice parameters from XRD refinement are consistent with the olivine structure. The values are a = 10.2883A (0.0020), b = 5.9759 (0.0037), c = 4.6717A
(0.0012) 0.0072, cell volume = 287.2264A' (0.0685).
Density, p = 3.605 g/cc, zero = 0.452 (0.003). Peak at full width lialf maximum, PFWHM = 0.21. Crvstallite size from XRD data = 704A.

The x-ray pattern demonstrates that the product of the invention was indeed the nominal formula LiFePOq.
The term "nominal formula" refers to the fact that the relative proportion of atomic species may vary slightly on the order of 2 percent to 5 percent, or more typically, 1 percent to 3 percent, and that some portion of P may be substitutecl by Si, S or As; and some portion of 0 may be substituted by halogen, preferably F.

The LiFePOa, prepared as described immediately above, was tested in an electrochemical cell. The positive electrode was prepared as described above, using 19.0mg of active material. The positive electrode contained, on a weight "L, basis, 85','1 active material, 10%
carbon black, anci 5'. EPDM. The negative electrode was metallic lithium. The electrolyte was a 2:1 weight ratio mixture of ethylene carbonate and climethyl carbonate within which was dissolved 1 molar LiPF,:. The cells were cycled between about 2.5 and about 4.0 volts with performance as shown in Figures 2 and 3.

Figure 2 shows the results of the first constant current cycling at 0.2 milliamps per square centimeter betweeii about 2.5 and 9.0 volts based upon about 19 milligrams of the LiI'ePO4 active material in the cathode (positive electrode). In an as prepared, as assembled, initial condition, the positive electrode active material is LiFePO4. The lithium is extracted from the LiFePOa during charging of the cell. When fully charged, about 0.72 unit of lithium had been removed per formula unit. Consequently, the positive electrode active material corresponds to Li,_;,L='eP04 where x appears to be equal to about 0.72, when the catlzode material is at 4.0 volts versus Li/Li'. The extraction represents approximately 123 milliamp hours per gram corresponding to about 2.3 milliamp hours based on 19 milligrams active material. Next, the cell is discharged whereupon a quantity of lithium is re-inserted into the LiFePO4. The re-insertion corresponds to approximately 121 milliamp hours per gram proportional to the insertion of essentially all of the lithium. The bottom of the curve corresponds to approximately 2.5 volts. The total cumulative capacity demonstrated during the entire extraction-insertion cycle is 244mAh/g.

Figure 3 presents data obtained by multiple constant current cycling at 0.2 milliamp hours per square centimeter of the LiFePO4 versus lithium metal counter electrode between 2.5 anci 4.0 volts. Data is shown for two temperatures, 23 C and 60 C. Figure 3 shows the excellent rechargeability of the LiFePO4 cell, and also shows good cycling and capacity of the cell. The performance shown after about 190 to 200 cycles is good and shows that electrocie formulation is very desirable.
Referring to Figure 4, there is sliown data for the final product LiFe1;..,MgO,1POa, prepared from the metal compounds Fe201 and Mg (OFi) _-> Mg (OH) , per Reaction 2(b) .
Its CuKec x-ray diffraction pattern contained all of the peaks expected for this material as shown in Figure 4.
The pattern evident in Figure 4 is consistent with the single phase olivine phosphate compound, LiFeo.,Mgo.1PO.1 _ This is evidenced by the position of the peaks in terms of the scattering angle 2 6(theta), x axis. The x-ray pattern showed no peaks due to the presence of precursor oxides indicatiiig that the solid state reaction is essentially entirely completed. Here the space group SG
= Pnma (62) and the lattice parameters from XRD
refinement are consistent with the olivine structure.
The values are a= 10.2688A (0.0069), b = 5.9709A
(0.0072), c 4.6762A (0.0054), cell volume = 286.7208A
(0.04294), p 3.617 g/cc, zero = 0.702 (0.003), PFWHM =
0.01, and crystallite = 950A.
The x-ray pattern demonstrates that the product of the invention was indeed the nominal formula L1Feo_9Mgo.,P0a, The term "nominal formula" refers to the fact that the relative proportion of atomic species may vary slightly on the order of 2 percent to 5 percent, or more typically, 1 percent to 3 percent, and that some substitution of P and 0 may be made while maintaining the basic olivine structure.

The LiFe,,..,Mg,,.1P0.4, prepared as described immediately above, was tested in an electrochemical cell.
The positive electrode was prepareci as described above, using 18.9mg of active materials. The positive electrode, negative electrode and electrolyte were prepared as described earlier and in connection with Figure 1. The cell was between about 2.5 ancl about 4.0 volts with performance as shown in Figures 4, 5 and G.

Figure 5 shows the results of the first constant current cycling at 0.2 milliamps per square centimeter between about 2.5 and 4.0 volts based upon about 18. 9. milligrarns of the LiFe,,.,,Mgo.,PO,, active material in the cathode (positive electrode). In an as prepared, as assembled, iilitial condition, the positive electrode active material is LiFe0.,,Mgo.1POa. The lithium is extracted from the LiFeõ_õMg0.1PO4 during charging of the cell. When fully charged, about 0.87 units of lithium have been removed per formula unit.
Consequently, the positive electrocie active material corresponds to Li,_,.Fe(,_.,Mg,,,POa where x appears to be equal to about 0.87, when the cathode material is at 4.0 volts versus Li/Li'. The extraction represents approximately 150 milliamp hours per gram corresponding to about 2.8 milliamp hours based on 18.9 milligrams active material.
Next, the cell is discharged whereupon a quantity of lithium is re-inserteci into the LiFe,.-,MgO_,PO.1 . The re-insertion corresponds to approximately 146 milliamp hours per gram proportional to the insertion of essentially all of the lithium. The bottom of the curve corresponds to approximately 2.5 volts. The total cumulative specific capacity over the entire cycle is 296 mAhr/g. This material has a much better cycle profile than the LiFePO4. Figure 5(LiFe.,,,Mg0,.1POa) shows a very well defined and sharp peak at about 150 mAh/g. In contrast, Figure 2(LiFePOa) shows a very shallow slope leading to the peak at about 123 mAh/g. The Fe-phosphate (Figure 2) provides 123 m11h/g compared to its theoretical capacity of 170 mAh/g. This ratio of 123/170, 72:', is relatively poor compared to the Fe/Mg-phosphate. The Fe/Mg-phosphate (Figure 5) provides 150 mAh/g compared to a theoretical capacity of 160, a ratio of 150/160 or 94"a.
Figure 6 presents data obtained by multiple constant current cycling at 0.2 milliamp hours per square centimeter of the Li Fe,,..,Mg,,., POQ versus l i t}iium metal counter electrode between 2.5 and 4.0 volts. Figure 6 shows the excellent rechargeability of the Li/LiFeo.9Mgo_,P04 cell, and also shows good cycling and capacity of the cell. The performance shown after about 150 to 160 cycles is very good and shows that electrode formulation LiFe..,,Mgo.1PO4 performed significantly better 5 than the LiFePO4. Comparing Figure 3(LiFePO.4) to Figure 6(LiFeo.9Mgo.,P04) it can be seen that the Fe/Mg-phosphate maintains its capacity over prolonged cycling, whereas the Fe-phosphate capacity fades significantly.

10 Figure 7 shows the results of the first constant current cycling at 0.2 milliamps per square centimeter between about 2.5 and 9.0 volts based upon about 16 milligrams of the LiFeo.kMgO.,P0a active material in the cathode (positive electrode). In an as prepared, 15 as assembled, initial condition, the positive electrode active material is LiFe,.õMgo.,POa. The lithium is extracted from the LiFeO.NMgO._PO.1 during charging of the cell. When fully charged, about 0.79 units of lithium have been removed per formula unit. Consequently, the 20 positive electrode active material corresponds to LiFeo8DMgo2ZPOa where x appears to be equal to about 0.79, when the cathode material is at 9.0 volts versus Li/Li'.
The extraction approximately 140 milliamp hours per gram corresponding to about 2.2 milliamp hours based on 16 25 milligrams active material. Next, the cell is discharged whereupon a quantity of lithium is re-inserted into the LiFeo.oMg0,2P04. The re-insertion corresponds to approximately 122 milliamp hours per gram proportional to the insertion of essentially all of the lithium. The 30 bottom of the curve corresponds to approximately 2.5 volts. The total cumulative specific capacity over the entire cycle is 262 mAhr/g.

Referring to Figure 8, there is shown data for 35 the final product LiFe0,..,Ca(,.1POa, prepared from Fe903 and Ca(OH)2 by Reaction 3. Its CuKa x-ray diffraction pattern contained all of the peaks expected for this material as shown in Figure B. The pattern evident in Figure 8 is consistent with the single pliase olivine phosphate compound, LiFe(,,.,Ca,,,,POa. This is evidenced by the position of the peaks in terms of the scattering angle 2 (theta), x axis. The x-ray pattern showed no peaks due to the presence of precursor oxides indicating that the solid state reaction is essentially entirely completed. Here the space group SG = Pnma (62) and the lattice parameters from XRD refinement are consistent with olivine. The values are a = 10.3290A (0.0045), b 6.0042A (0.0031), c= 4.6887A (0.0020), cell volume =
290.6370A (0.1807), zero = 0.702 (0.003), p = 3.62 g/cc, PFWHM = 0.18, and crystallite = 680A. The x-ray pattern demonstrates that the product of the invention was indeed the nominal formula LiFeo,.1Ca0 ,,,P04.

Figure 9 shows the results of the first constant current cycling at 0.2 milliamps per square centimeter between about 2.5 and 4.0 volts based upon about 18.5 milligrams of the LiFeO.s~Cao..PO,, active material in the cathode (positive electrode). In an as prepared, as assembled, initial condition, the positive electrode active material is LiFeO.,;Cao,=POa. The lithium is extracted from the LiFe,,,,,Cao._.POa during charging of the cell. When fully charged, about 0.71 units of lithium have been removed per formula unit.
Consequently, the positive electrode active material corresponds to LiFeo.nCa,,,PO.1 where x appears to be equal to about 0.71, when the cathode material is at 4.0 volts versus Li/Li'. The extraction represents approximately 123 milliamp hours per gram corresponding to about 2.3 milliamp hours based on 18.5 milligrams active material.
Next, the cell is discharged whereupon a quantity of lithium is re-inserted into the LiFe,,.FCa,,._P04. The re-insertion corresponds to approximately 110 milliamp hours per gram proportional to the insertion of nearly all of the lithium. The bottom of the curve corresponds to approximately 2.5 volts. The total specific cumulative capacity over the entire cycle is 233 mAhr/g.
.Figure 10 shows the results of the first constant current cycliizg at 0.2 milliamps per square centimeter between about 2.5 and 4.0 volts based upon about 18.9 milligrams of the LiFen.õZno,_P04 olivine active material in the cathode (positive electrode). In an as prepared, as assembled, initial condition, the positive electrode active material is LiFeo_,,ZnO,:POa1 prepared from Fe203 and Zn,,(PO~): by Reaction 4. The lithium is extracted from the LiFeO.;,Zno._PO., during charging of the cell. When fully charged, about 0.74 units of lithium have been removed per formula unit. Consequently, the positive electrode active material corresponds to Li,_ xFeO.IIZn0.2P04 where x appears to be equal to about 0.74, when the cathode material is at 4.0 volts versus Li/Li'.
The extraction represents approximately 124 milliamp hours per gram corresponding to about 2.3 milliamp hours based on 18.9 milligrams active material. Next, the cell is discharged whereupon a quantity of lithium is re-inserted into the LiFeO,pZnO_,PO4. The re-insertion corresponds to approximately 108 milliamp hours per gram proportional to the iilsertion of nearly all of the lithium. The bottom of the curve corresponds to approximately 2.5 volts.

Referring to Figure 11, the final product LiV2O5, prepared by Reaction 5, appeared black in color.
Its CuKa x-ray diffraction pattern contained all of the peaks expected for this material as shown in Figure 11.
The pattern evicient in Figure 11 is consistent with a single oxide compound gamma-LiV,O!~õ This is evidenced by the position of the peaks in terms of the scattering angle 2 (theta), x axis. The x-ray pattern showed no peaks due to the presence of precursor oxides indicating that the solid state reaction is esseiitially entirely completed.
The x-ray pattern demonstrates that the product of the invention was indeed the nominal formula gamma-LiV205. The term "nominal formula" refers to the fact that the relative proportion of atomic species may vary slightly on the order of 2 percent to 5 percent, or more typically, 1 percent to 3 percent.

The LiV_.O5 prepared as described immediately above, was tested in ari electrochemical cell. The cell was prepared as described above and cycled with performance as shown in Figures 12 and 13.

Figure 12 shows the results of the first constant current cycling at 0.2 milliamps per square centimeter between about 2.8 and 3.8 volts based upon about 15.0 milligrams of the LiV_O~, active material in the cathode (positive electrode). In an as prepared, as assembled, initial condition, the positive electrode active material is LiV:O~,. The lithium is extracted from the LiV2O5 during charging of the cell. When fully charged, about 0.93 unit of lithium had been removed per formula unit. Consequently, the positive electrode active material corresponds to Li,_:.:V_O, where x appears to be equal to about 0.93, wllen the cathode material is at 3.8 volts versus Li/Li'. The extraction represents approximately 132 milliamp hours per gram corresponding to about 2.0 milliamp hours based on 15.0 milligrams active material. Next, the cell is discharged whereupon a quantity of litliium is re-inserted into the LiV2O5. The re-insertion corresponcls to approximately 130 milliamp hours per gram proportional to the insertion of essentially all of the lithium. The bottom of the curve corresponds to approximately 2.8 volts.

Figure 13 preseiZts data obtained by multiple S. constant current cycling at 0.4 milliamp hours per square centimeter (C/2 rate)of the LiV,O,, versus lithium metal counter electrode between 3.0 and 3.75 volts. Data for two temperature conditions are shown, 23 C and 60 C.
Figure 13 is a two part graph with Figure 13A showing the excellent rechargeability of the LiV-.0-,. Figure 13B
shows good cycling and capacity of the cell. The performance shown up to about 300 cycles is good.

Referring to Figure 14, the final product Li3V2 (POa) õ prepared by Reaction 6, appeared green/black in color. Its CuKa x-ray diffraction pattern contained all of the peaks expected for this material as shown in Figure 14. The patterii evident in Figure 14 is consistent with a single phosphate compound Li1V,(PO4)3 of the monoclinic, Nasicon phase. This is evidenced by the position of the peaks in terms of the scattering angle 2 0(theta), x axis. The x-ray pattern showed no peaks due to the presence of precursor oxides indicating that the solid state reaction is essentially entirely completed.
The x-ray patterti demonstrates that the product of the invention was indeed the nominal formula Li3V2(PO4)3 , The term "nominal formula" refers to the fact that the relative proportion of atomic species may vary slightly on the order of 2 percent to 5 percent, or more typically, 1 percent to 3 percent; and that substitution of P and 0 may occur.

The Li,V,(PO.,),prepared as described immediately above, was tested in an electrochemical cell. The cell was prepared as clescribeci above, using 13.8mg of active material. The cell was prepared as described above and cycled between about 3.0 and about 4.2 volts using the EVS technique with performance as shown in Figures 16 and 17. Figure 16 shows specific capacity versus electrode 5 potential against Li. Figure 17 shows differential capacity versus electrode potential against Li.

A comparative method was used to form Li3V.1 (P04)3. Such method was reaction without carbon and 10 under H2-reducing gas as described in U.S. Patent No.
5,871,866. The final product, prepared as per U.S.
Patent No. 5,871,866, appeared green in color. Its CuKcx x-ray diffraction pattern contained all of the peaks expected for this material as shown in Figure 15. The 15 pattern evident in Figure 15 is consistent with a monoclinic Nasicon single phase phosphate compound Li3V2 (P04)3. This is evidenced by the position of the peaks in terms of the scattering angle 2 0(theta), x axis. The x-ray pattern showed no peaks due to the 20 presence of precursor oxides ii7dicating that the solid state reaction is essentially entirely completed.
Chemical analysis for lithium and vanadium by atomic absorption spectroscopy showed, on a percent by weight basis, 5.17 percent lithium and 26 percent vanadium. This 25 is close to the expected result of 5.11 percent lithium and 25 percent vanadium.

The chemical analysis and x-ray patterns of Figures 14 and 15 clemonstrate that the product of Figure 30 14 was the same as that of Figure 15. The product of Figure 14 was prepared without the undesirable H, atmosphere and was prepared by the novel carbothermal solid state synthesis of the invention.

35 Figure 16 shows a voltage profile of the test cell, based on the Li_,.V_(PO,1). positive electrode active material made by the process of the invention and as characterized in Figure 14. It was cyclecl against a lithium metal counter electrode. The data shown in Figure 16 is based on the Electrochemical Voltage Spectroscopy (EVS) technique. Electrochemical and kinetic data were recorded using the Electrochemical Voltage Spectroscopy (EVS) technique. Such technique is known in the art as described by J. Barker in Synth, Met 28, D217 (1989); Synth. Met. 32, 43 (1989); J. Power Sources, 52, 185 (1994); and Electrochemica Acta, Vol.
40, No. 11, at 1603 (1995). Figure 16 clearly shows and highlights the reversibility of the product. The positive electrode contained about 13.8 milligrams of the Li3V2 (P04) ,, active material. The positive electrode showed a performance of about 133 milliamp hours per gram on the first discharge. In Figure 16, the capacity in, and the capacity out are essentially the same, resulting in essentially no capacity loss. Figure 17 is an EVS
differential capacity plot based on Figure 16. As can be seen from Figure 17, the relatively symmetrical nature of peaks indicates good electrical reversibility, there are small peak separations (charge/discharge), and good correspondence between peaks above and below the zero axis. There are essentially no peaks that can be related to irreversible reactions, since all peaks above the axis (cell charge) have corresponding peaks below the axis (cell discharge), and there is essentially no separation between the peaks above and below the axis. This shows that the carbothermal method of the invention produces high quality electrode material.

Figure 18 presents data obtaiiled by multiple constant current cycling at 0.2 milliamp hours per square centimeter of the LiFe(,.nMgc)._.POa versus lithium metal counter electrode between 2.5 and 4.0 volts. Figure 18 shows the excellent rechargeability of the Li/LiFeo.flMgo.2P04 cell, and also shows good cycling and capacity of the cell. The perforinance shown after about 110 to 120 cycles at 23 C is very good and shows that electrode formulation LiFe,,.hMg(3.:POa performed significantly better than the LiFePO_1. The cell cycling test at 60 C was started after the 23 C test and was ongoing. Comparing Figure 3(LiFePOa) to Figure 18 (LiFeo,oMgo,2P04) , it can be seen that the Fe/Mg-phosphate maintains its capacity over prolonged cycling, whereas the Fe-phosphate capacity fades significantly.

In addition to the above cell tests, the active materials of the invention were also cycled against insertion anodes in non-metallic, lithium ion, rocking chair cells.

The lithium mixed metal phosphate and the lithium metal oxide were used to formulate a cathode electrode. The electrode was fabricated by solvent casting a slurry of the treated, enriched lithium manganese oxide, conductive carbon, binder, plasticizer and solvent. The conductive carbon used was Super P (MMM
Carbon). Kynar Flex 28010 was used as the binder and electronic grade acetone was used as a solvent. The preferred plasticizer was dibutyl phthalate (DPB). The slurry was cast onto glass and a free-standing electrode was formed as the solvent was evaporated. In this example, the cathode had 23.1mg LiFe0..,Mg0).1PO.1 active material. Thus, the proportions are as follows on a percent weight basis: 80?, active material; 811, Super P
carbon; and 125,1, Kynar binder.

A graphite counter electrode was prepared for use with the aforesaid cathode. The graphite counter electrode served as the anode in the electrochemical cell. The anode haci 10.8 mg of the MCMB graphite active material. The graphite electrode was fabricated by solvent castitlg a slurry of MCMB2528 graphite, binder, and casting solvent. MCMB2528 is a mesocarbon microbead material supplied by Alumina Trading, which is the U.S.
distributor for the supplier, Osaka Gas Company of Japan.
This material has a density of about 2.24 grams per cubic centimeter; a particle size maximum for at least 95% by weight of the particles of 37 microns; median size of about 22.5 microns and an interlayer distance of about 0.336. As in the case of the cathode, the binder was a copolymer of polyvinylidene difluoride (PVdF) and hexafluoropropylene (HFP) in a wt. ratio of PVdF to HFP
of 88:12. This binder is sold under the designation of Kynar Flex 2801(F), showing it's a registered trademark.
Kynar Flex is available from Atochem Corporation. An electronic grade solvent was used. The slurry was cast onto glass and a free standing electrode was formed as the casting solvent evaporated. The electrode composition was approximately as follows on a dry weight basis: 85% graphite; 122 binder; and 32 conductive carbon.

A rocking chair battery was prepared comprising the anode, the cathode, and an electrolyte. The ratio of the active cathode mass to the active anode mass was about 2.14:1. The two electrode layers were arranged with an electrolyte layer in between, and the layers were laminated together using heat and pressure as per the Bell Comm. Res. patents. In a preferred method, the cell is activated with EC/DMC solvent in a weight ratio of 2:1 in a solution containing 1 M LiPr,; salt.

Figures 19 and 20 show data for the first four complete cycles of the lithium ion cell having the LiFeo.9Mgo.1P04 cathode and the MCMB2528 anode. The cell comprised 23.1mg active LiFe0,.,,Mg0_1PO4 and 10.8mg active MCMB2528 for a ca.thode to anode mass ratio of 2.14. The cell was charged and discharged at 23 C at an approximate C/10 (10 hour) rate between voltage limits of 2.50 V and 3.60 V. The voltage profile plot (Figure 19) shows the variation in cell voltage versus time for the LiFeo.9Mgo11PO4/MCMB2528 lithium ion cell. The symmetrical nature of the charge-discharge is clearly evident. The small degree of voltage hysteresis between the charge and discharge processes is evidence for the low overvoltage in the system, which is very good. Figure 20 shows the variation of LiFeO,9,Mgõ_1PO.1 specific capacity with cycle number. Clearly, over the cycles shown, the material demonstrates good cycling stability.

Figure 21 shows data for the first three complete cycles of the lithium ion cell having the gamma-LiV20, cathode and the MCMB2528 anode. The cell prepared was a rocking chair, lithium ion cell as described above.
The cell comprised 29.1mg gamma-LiV_0~, cathode active material and 12.2mg MCMB2528 anode active material, for a cathode to anode mass ratio of 2.39. As stated earlier, the liquid electrolyte used was EC/DMC (2:1) and 1M
LiPF(;. The cell was charged and discharged at 23 C at an approximate C/10 (10 hour) rate between voltage limits of 2.50 V and 3.65 V. The voltage profile plot (Figure 21) shows the variation in cell voltage versus time for the LiV205/MCMB2528 lithium ion cell. The symmetrical nature of the charge-discharge is clearly evident. The small degree of voltage hysteresis between the charge and discharge processes is evidence for the low overvoltage in the system, which is very good.

In summary, the invention provides new compounds LidMI,,MII; (PO_,),, and gamma-LiV.O,, by new methods which are adaptable to commercial scale production. The Li,MI,_YMIIyPOq compounds are isostructural olivine compounds as demonstrated by XRD analysis. Substituted compounds, such as LiFe1_YMgYPOa show better performance than LiFePO4 unsubstituted compounds when used as electrode active materials. The method of the invention 5 utilizes the reducing capabilities of carbon along with selected precursors and reaction conditions to produce high quality products suitable as electrode active materials or as ion conductors. The reduction capability of carbon over a broad temperature range is selectively 10 applied along with thermodynamic and kinetic considerations to provide an energy-efficient, economical and convenient process to produce compounds of a desired composition and structure. This is in contrast to known methods.
Principles of carbothermal reduction have been applied to produce pure metal from metal oxides by removal of oxygen. See, for example, U.S. Patent Nos.
2, 580, 878, 2, 570, 232, 4, 177, 060, and 5,803,974.
Principles of carbothermal and thermal reduction have also been used to form carbides. See, for example, U.S.
Patent Nos. 3,8G5,745 and 5,384,291; and non-oxide ceramics (see U.S. Patent No. 5,607,297). Such methods are not known to have been applied to form lithiated products or to form products without oxygen abstraction from the precursor. The methods described with respect to the present invention provide high quality products which are prepared from precursors which are lithiated during the reaction without oxygen abstraction. This is a surprising result. The new methods of the invention also provide new compounds not known to have been made before.
For example, alpha-V_O~, is conventionally lithiated electrochemically against metallic lithium.
Thus, alpha-V,O!~ is not suitable as a source of lithium for a cell. As a result, alpha-V_0~, is not used in an ion cell. In the present invention, alpha-V,O., is lithiated by carbothermal reduction using a simple lithium-containing compound and the reducing capability of carbon to form a gamma-LiV_,0.,. The single phase compound, gamma-LiV.O,, is not known to have been directly and independently prepared before. There is not known to be a direct synthesis route. Attempts to form it as a single phase resulted in a mixed phase product containing one or more beta phases and having the formula LixV~O;
with 0 < x 5 0.49. This is far different from the present single phase gamma-Li~V_0,, with x equal to one, or very close to oiie. The flexibility of the process of the present invention is such that it can be conducted over a wide temperature range. The higher the temperature, the more quickly the reaction proceeds. For example, at 650 C, conversion of alpha-V_05, to gamma-LiV,05 occurs in about one hour, anci at 500 it takes about 8 hours.
Here, about one quarter (1/4) atomic unit of carbon is used to reduce one atomic unit of vanadium, that is, V45V45 to V''Vi". The predominate reaction is C to COZ
where for each atomic unit of carbon at ground state zero, a plus 4 oxidation state results. Correspondingly, for each 1/4 atomic unit of carbon, one atomic unit of vanadium is reduced from V'' to V'". (See Reaction 5).
The new product, gamma-LiV,O,, is air-stable and suitable as an electrode material for an ion cell or rocking chair battery.

The convenience and energy efficiency of the present process can also be contrasted to known methods for forming products under reducing atmosphere such as H, which is difficult to control, and from complex and expensive precursors. In the present invention, carbon is the reducing agent, anci simple, inexpensive and even naturally occurring precursors are useable. For example, it is possible to produce LiFePOa from Fe,O õ a simple common oxide. (See Reaction ib). The production of LiFePOa provides a good example of the thermodynamic and kinetic features of the method. Iron phosphate is reduced by carbon and lithiateci over a broad temperature range. At about 600 C, the C to C0: reaction predominates and takes about a week to complete. At about 750 C, the C to CO reaction predominates and takes about 8 hours to complete. The C to CO= reaction requires less carboii reductant but takes longer due to the low temperature kinetics. The C to CO reaction requires about twice as much carbon, but due to the high temperature reaction kinetics, it proceeds relatively fast. In both cases, the Fe in the precursor Fe203 has oxidation state +3 and is reduced to oxidation (valence) state +2 in the product LiFePOa. The C to CO reaction requires that 1,2 atomic unit of carbon be used for each atomic unit of Fe reduced by one valence state. The CO
to CO2 reaction requires that 1/4 atomic unit of carbon be used for each atomic unit of Fe reduced by one valence state.

The active materials of the invention are also characterized by being stable in an as-prepared condition, in the presence of air and particularly humid air. This is a strikiiig advantage, because it facilitates preparation of and assembly of battery cathodes and cells, without the requirement for controlled atmosphere. This feature is particularly important, as those skilled in the art will recognize that air stability, that is, lack of degradation on exposure to air, is very important for commercial processing. Air-stability is known in the art to more specifically indicate that a material does not hydrolyze in presence of moist air. Generally, air-stable materials are also characterized by Li being extracted therefrom above about 3.0 volts versus lithium. The higher the extraction potential, the more tightly bound the lithium ions are to the host lattice. This tightly bound property generally confers air stability on the material. The air-stability of the materials of the invention is consisteilt with the stability demonstrated by cycling at the conditions stated herein. This is in contrast to materials which insert Li at lower voltages, below about 3.0 volts versus lithium, and which are not air-stable, and which hydrolyze in moist air.
While this invention has been described in terms of certain embocliments tliereof, it is not intended that it be limited to the above description, but rather only to the extent set forth in the following claims.
The embodiments of the invention in which an exclusive property or privilege is claimed are defined in the following clainis.

Claims (11)

WHAT IS CLAIMED IS:

1. A composition, comprising:

a lithium-mixed metal compound represented by the nominal general formula Li a Fe1-y M y PO4;

wherein 0<y<1, a is about 1, and M is at least one selected from the group consisting of Mg, Ca, Zn, Sr, Pb, Cd, Sn, BA, Be, and mixtures thereof; and carbon associated with the lithium-mixed metal material, wherein the composition is prepared by a process which includes the step of reacting a lithium compound and a metal compound.

2. The composition of claim 1, wherein the reacting step comprises the steps of:

forming a mixture comprising starting materials in proportions to provide the active material, and carbon; and heating the mixture for a time and at a temperature sufficient to form the active material.

3. The composition of claim 1 or 2, wherein the mixture is heated in a non-oxidizing atmosphere.

4. The composition of claim 3, wherein the non-oxidizing atmosphere is selected from the group consisting of argon, nitrogen, a mixture of carbon-monoxide and carbon-dioxide generated by heating the carbon, and mixtures thereof.

5. The composition of any one of claims 1 to 4, wherein the carbon is present in an amount sufficient to reduce the oxidation state of the metal compound to an elemental state.

6. The composition of claim 1 or 2, wherein M is selected from the group consisting of Be, Mg, Ca, Sr, Ba, and mixtures thereof.

7. The composition of claim 1 or 2, wherein M is selected from the group consisting of Zn, Cd, and mixtures thereof.

8. The composition of claim 1 or 2, wherein M is selected from the group consisting of Sn, PB, and mixtures thereof.

9. The composition of any one of claims 1 to 8, wherein the lithium compound is selected from the group consisting of lithium acetate, lithium hydroxide, lithium nitrate, lithium oxalate, lithium oxide, lithium hydroxide monohydride, lithium hydrogen carbonate, lithium dihydrogen phosphate, and lithium carbonate.

10. The composition of any one of claims 1 to 10, wherein the composition is a single phase material.

11. The composition of claim 20, further including a composition according to claim 13.