JP2003511827A - Cathode active materials for lithium electrochemical cells - Google Patents

Abstract

(57) Abstract: The present invention relates to a novel single phase compound of molecular formula _{Li x Cr y Mn 2-y} O 4 + z (2.2 <x <4,0 <y <2 and Z ≧ 0. The compound Can be used as the active cathode material for secondary lithium ion batteries, and secondary lithium ion batteries having such cathodes have also been described.

Description

Detailed Description of the Invention

[0001] BACKGROUND OF THE INVENTION The present invention has the formula _{Li x Cr y Mn 2-y} O 4 + z (2.2 <x <4,0 <y <2, and z
≧ 0) and the use of this compound as a cathode material for lithium ion secondary batteries and lithium batteries.

The motivation for the present invention is that the demand for rechargeable batteries combining high specific energy density and volume energy density with low cost and thermal stability has increased in recent years.

Description of the Prior Art Lithium-ion batteries are rechargeable electrochemical cells in which the electrically active components of both the anode and cathode are lithium intercalation compounds. The intercalation compound acts as a host structure for lithium ions, which are either stored or released depending on the polarity of the externally applied potential. A lithium-ion battery consists of a lithium intercalation cathode having an oxidation potential and a lithium intercalation anode having a reduction potential.
Lithium intercalation materials are capable of reversibly storing and releasing lithium ions in response to an electrochemical potential. During discharge, lithium ions move from the anode to the cathode in the lithium-ion battery, thereby generating an electrochemical current. During charging, energy is consumed to move lithium ions from the cathode to the anode. The greater the potential difference between the cathode and the anode, the greater the electrochemical potential of the resulting cell.
The more lithium that can be stored reversibly in the cathode and the anode and that can be released from them, the greater the capacity. The discharge capacity of a battery is reflected in the period during which the battery can provide a given current. Typical anodes for lithium-ion batteries are made from carbonaceous materials such as graphite or petroleum cake. A typical cathode is made from a transition metal oxide or sulfide. To facilitate battery manufacture, lithium-ion batteries are usually assembled in a completely discharged state with lithium present only in the cathode and not in the anode. In this state, both the anode material and the cathode material are normally stable in air. Assembling a cell in the discharged state means that the final capacity of the cell depends on the amount of lithium initially present in the cathode. For example, in a LiMnO ₂ -based cathode, Li
It has a theoretical capacity twice that of the cathode based on Mn ₂ O ₄ .

In previous reports and patent specifications for cathodes for lithium-ion batteries, various mixed oxides of lithium, such as LiCoO ₂ , LiNiO ₂ , LiN, were used.
It proposes to use i _x Co _1-x O ₂ and LiMn ₂ O ₄ as active materials.

[0005]   LiMn in lithium secondary battery with metallic lithium anode_2-xCr_xO_4.35 (0.2 <x <0.4) and LiCr_xMn_2-yO_FourFor phases such as (0 <x <1)
Also known for use. For this, see “Solid State Ionics” by G. Pistoia et al. 58 , 285 (1992) and B. Wang et al., “Studies of LiCr_xMn_2-xO_Four for Secondary L
ithium Batteries ", Summary of the 6th International Conference on Lithium Batteries, Mann, Germany
See Star, May 10-15, 1992. (J. Power Source,43-44, 539-5
46 (1992)). In the latter, the material is shown as having a cubic lattice structure.
It Further, in the latter, further Li is electrochemically inserted. However,
0.4 mol equivalent of lithium is inserted into_1.4Cr_0.4Mn_1.6O_FourExpression
It is only given the oxide of.

Further, Li _q used in rechargeable electrochemical cell M _x Mn _y O _z (q is 0 to 1.3) Molecular formula Li is less lithium manganese spinel structure also, U.S. Patent No. 5,1
69,736.

[0007] Relatively recently, the amount of lithium in such mixed metal oxides has increased. In Applicant's U.S. Patent No. 5,370,949 of 1994 December _{6, Li 2 Cr y Mn 2-} x O 4 (0 <x <2) Molecular formula single phase compound of, and lithium Its use in ion secondary batteries is described. These materials were prepared by standard solid state technology and were 170 mAh at low current densities (3.6 mA / g).
It showed good repeatability of discharge capacity up to / g. Relatively large discharge capacities have been found in compositions where at least half of the transition metal component is manganese. However, a phase that contains significantly more manganese than chromium exhibits a voltage curve with two plateaus that are commercially less preferred in the initial or subsequent discharge. Further structural and electrochemical characteristics of these cathode materials are described in Journal of Pow.
er Source, two papers (Vol. 54, 205-208, 1995, and 81-82, 406-411, 1999).

Another material in this regard is Riley, US Pat. No. 4,5, Jan. 28, 1986.
67,031. Summary of this reference, the formula Li _x M _y O
A mixed metal oxide of z (M is at least one metal selected from the group consisting of titanium, chromium, manganese, iron, cobalt, and nickel) is described. It is noted that none of the possible structures contain Mn or Cr. Furthermore, there is no disclosure of the use of such compounds as cathodes in secondary batteries.

The preparation and characteristics of a material having a composition of Li ₂ Cr _x Mn _2-x O ₄ (1.0 ≦ x ≦ 1.5) are described by Dahn, Zheng and Thomas (J. Electrochem. Soc., 145 , 851 ~ 859, 1998
March of the year). These materials were made using the sol-gel technique, followed by heating to a temperature of 500-1,100 ° C in an inert atmosphere.
In this study, a sample of composition Li ₂ Cr _1.25 Mn _0.75 O ₄ prepared at a temperature of 700 ° C. showed a maximum discharge capacity of 150 mAh / g at a small current density (1.5 mA / g). Repeated testing of the same sample at 15mA / g gives approximately 137mAh / g
Capacity was shown. All materials prepared at 700 ° C. were shown by powder X-ray diffraction to have a layered structure such as LiCoO ₂ with hexagonal unit cell symmetry. The volume of the crystal unit _{cell, Li 2 Cr x Mn 2-} x O ₄ per unit was 68.6 to 71.9 Å.

US Pat. No. 5,858,324, dated December 12, 1999, describes Li _y
Disclosed is a process for preparing compounds of Cr _x Mn _2-x O _{4 + z} (y ≧ 2, 0.25 <x <2, and Z ≧ 0). The experimental examples shown in this disclosure are:
Figure 3 illustrates the use of these materials as the active cathode of rechargeable lithium-ion electrochemical cells. The Li _y Cr _x Mn _2-x O _{4 + z} sample was prepared by adding ammonium hydroxide as a gelling agent from chromium nitrate nonahydrate, manganese (II) acetate tetrahydrate, and lithium hydroxide monohydrate. Depending on the sol-gel process used, J. Electrochem. Soc
(145, 851-859, March 1998). The gel is
A Li _y Cr _x Mn _2−x O _{4 + z} compound was prepared by heat treatment at a temperature of 500 to 1100 ° C. in an inert atmosphere.

The compound has a Reitveld of crystalline unit cell dimensions based on powder X-ray diffraction data.
Characterized by analysis. The symmetries and space groups of the compounds have been found to depend on composition and processing temperature. Structural and chemical analyzes of the compositions studied are outlined in Table 1 of US Pat. No. 5,858,324. In this Table 1, a summary of structural and chemical analyzes is shown for the 37 samples studied. _{Two of the} Li _y Cr _x Mn _2-x O _{4 + z} examples presented here (Sample 2
2 and 23) alone, y is larger than 2.0. The value of x is 0.5 to 1.5
And the value of z is 0 as shown in Table 6.

Only the samples prepared at the lowest temperature such as 500 ° C. or 600 ° C.
It has a crystal unit cell volume per stoichiometric unit that is substantially less than 69.9 cubic Å of O ₂ . The electrochemical characteristics of these samples are described in US Pat. No. 5,858,32.
No. 4 is not shown. For the compositions Li _y Cr _x Mn _2-x O _{4 + z of} Examples 22 and 23 shown in Table 1 of this patent specification, y = 2.2 and x = 1.25. The crystal unit cell volume per stoichiometric unit of Example 22 prepared at 500 ° C was 68.
532 cubic liters, which is significantly smaller than the 69.9-74.3 cubic liters provided with the same compound as shown in Applicant's US Pat. No. 5,370,949. The electrochemical characteristics of Sample 22 are not given in US Pat. No. 5,858,324. The electrochemical evaluation of Example 23 of US Pat. No. 5,858,324 having a composition of Li _2.2 Cr _1.25 Mn _0.75 O ₄ and a standard unit cell volume of 69.81 cubic Å is summarized in Table 6. Has been done. The discharge capacity of this sample can be compared with the discharge capacity of Example 3-3 in the same table. Here, the sample of Example 3-3 has a composition of Li ₂ Cr _1.25 Mn _0.75 O ₄ and a standard crystal unit cell volume of 70.18 cubic Å
And tested under the same electrochemical conditions. Example 23 has a discharge capacity of 117
mAh / g, which was only slightly better than the discharge capacity of Example 3-3, which was 106 mAh / g. The slight difference in discharge capacity of the two examples is within the normal difference between cells with the same cathode.

US Pat. No. 5,858,324 describes PCT application (PCT International Publication WO
98/46528 and PCT application PCT / US98 / 04940).

[0014] Similar materials are disclosed in Japanese Publication No. 07-27 published October 20, 1995.
No. 2,765. In this reference, mixed oxides are sintered with vanadium compounds to make positive electrode materials for secondary batteries.

SUMMARY OF THE INVENTION It is an object of the present invention to provide new lithium oxide materials for use as active materials at the cathode of lithium ion electrochemical cells.

Another object of the present invention is to provide a secondary electrochemical cell with high energy density. The discharging / charging mechanism of this battery consists of L in the active material of the positive and negative electrodes.
It is based on the alternating insertion and extraction of i ⁺ ions.

A further object of the invention is to provide materials useful as cathodes in lithium-ion batteries that exhibit very high discharge and charge capacities.

A further object of the present invention is to provide good chemical resistance to electrolytes and high cyclic stability.

A further object of the present invention is to provide compounds containing relatively high amounts of lithium. Increasing the lithium content provides an additional path for the migration of lithium ions and increases the theoretical capacity of the cathode.

In one aspect of the present invention, the following new compounds of molecular formula (I) are provided. _{Li x Cr y Mn 2-y} O 4 + z (I) (2.2 <x <4.0,0 <y <2, and z ≧ 0)

It is preferred that x is from about 2.2 to about 4, and more preferably x is from 2.2 to 3.
It is 6.

Similarly, the value of y is in the middle to low value of this range, ie, about 0.1 to about 1.7.
Preferred values of 5, but the beneficial compounds of the present invention include a relatively large range of values, ie, up to about 1.9.

Further, it is preferable that z> 0, but more preferable that 0 <z ≦ 2.6.

The compound of formula (I) has a crystal unit cell volume smaller than that of LiCrO ₂ , that is, smaller than 104.9 cubic Å, assuming that the compound is hexagonal symmetric with respect to the R-3m structure. It can be further characterized by the fact that the average distance between the cation and the anion is smaller than that of LiCrO ₂ . This value is available from the literature.

Another aspect of the invention also provides the use of a compound of formula (I) as an active cathode material in a secondary lithium-ion electrochemical cell.

In yet another aspect of the invention, a lithium intercalation anode, a suitable non-aqueous electrolyte containing a lithium salt, a cathode of the compound of formula (I) shown above as the initial active material, and an anode and a cathode A secondary lithium-ion electrochemical cell having a separator between is provided.

In yet another aspect of the invention, several methods for making new compounds of molecular formula (I) are provided. Details of this method are shown below.

The anode of the present invention acts as a receptor for L ⁺ ions. Thus, the anode can be any intercalation compound. It is capable of intercalating lithium and has a sufficiently reducing electrode potential in the range of lithium intercalation to provide a suitable cell voltage. Specific examples include transition metal oxides such as MoO ₂ or WO ₂ ([Auborn and Barberio, J. Elec
trochem. Soc. 134 638 (1987)], which is incorporated herein by reference), transition metal sulfides (see US Pat. No. 4,983,476).
Or a carbon product obtained by thermal decomposition of an organic compound.
As will become apparent below, a variety of commercially available carbonaceous materials with defined structural properties have also been shown to be beneficial.

The cathode of molecular formula (I) above is an intercalation compound that has an anode at a sufficiently positive electrochemical potential to provide an overall useful voltage. The higher the potential, the higher the energy density obtained. The cathode generally acts as an initial carrier for lithium. The capacity of the cell is limited by the amount of lithium that is present in the cathode and that can be extracted from the layers. In most cases, only part of the lithium present during the manufacture of the cathode can be reversibly taken out of the layers.

The non-aqueous electrolyte of the present invention may be liquid, pasty or solid. In particular, the electrolyte may be a solid or gelled polymer. Beneficial polymers for lithium battery electrolytes include fluorinated polyvinylidene (with or without copolymers).
PVDF) and polyethylene oxide (PEO). The electrolyte is typically
The liquid organic medium contains a lithium salt. Lithium salts useful for this purpose include LiAsF ₆ , LiPF ₆ , LiBF ₄ , LiClO ₄ , LiBr, LiAlC.
There may be mentioned l ₄ , LiCF ₃ SO ₃ , LiC (CF ₃ SO ₂ ) ₃ , LiN (CF ₃ SO ₂ ) ₂ and mixtures thereof. LiAsF ₆ is toxic and should be used with caution. Water-free solvents for these salts include propylene carbonate, ethylene carbonate, 2-methyltetrahydrofuran,
Tetrahydrofuran, dimethoxyethane, diethoxyethane, thimethylcarbonate, diethylcarbonate, methylacetate, methylformate, γ-butyrolacactone, 1,3-dioxane, sulfolane, acetonitrile, butyronitrile, trimethylphosphate, dimethylformamide, and other similar Organic solvents can be used alone or in a mixture with other organic solvents. The electrolyte solution may contain additives, for example 12-C-4,15-C- 5 and crown ethers such as 18-C-6, or immobilizing agents, such as inorganic gel-forming, such as SiO ₂ or Al ₂ O ₃ A compound or polyethylene oxide can also be included. This is, for example, as shown in US Pat. No. 5,169,736, the disclosure of which is hereby incorporated by reference.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention relates to an invention relating to a phase having a relatively high lithium content and optionally a high oxygen content. As will be apparent from the examples below, these phases exhibit both a large capacitance and a sloped flat portion of one voltage curve. These are synthesized at a temperature of 600 to 800 ° C. Since they are prepared at moderate temperatures, it is desirable to achieve a completely uniform mixture of precursors before firing. As a result, techniques known to be very effective in preparing a homogeneous mixture of fine powders are used. These can include co-precipitation, spray drying, and polymer complexation. All three of these techniques have been shown to work and are detailed in the examples below. The first two techniques are known to result in materials with very high capacity and specific capacity.

In particular, the material provided by the present invention shows a large discharge capacity in one voltage curve in a flat plate having a slope at a potential higher than 2.5 V which is the potential of metallic lithium.

The idea of these processes is to prepare a homogeneous mixture of finely divided metal salts. The metal salts here can function as precursors for the synthesis of lithiated transition metal oxides containing one or more transition metals. For example, in a spray drying process, for example, Mn (CH ₃ CO ₂ ) ₂ and Cr ₃ (OH
) ₂ (CH ₃ CO ₂ ) ₇ solution was used. However, any combination of water soluble metal salts that can be thermally decomposed to the metal oxide can be used. Other suitable salts may include metal nitrates, sulphates, hydroxides, acid hydroxides, formates, citrates and other organic salts. Lithium-containing precursors such as lithium hydroxide, lithium nitrate, lithium sulphate, lithium acetate, lithium carbonate, lithium oxide or lithium chloride should also be thoroughly mixed with the transition metal salt prior to thermal decomposition to oxides. You can also Alternatively, the lithium precursor can be reacted with a transition metal oxide prepared by thermal decomposition of the mixed metal oxide.

There are various methods for the preparation of fine homogeneous mixtures, which may be, for example, the sol-gel method, coprecipitation, freeze drying, spray drying and the like. Among these methods, coprecipitation is widely used in the field of Ni-MH batteries for the production of spherical type Ni (OH) ₂ powder. In order to apply this technique to a system of Li, first, by adding an alkaline aqueous solution to a mixed aqueous solution containing a chromium salt and a manganese salt, the chromium hydroxide and the manganese hydroxide are coprecipitated to contain Cr and Mn. Make a complex hydroxide. Thereafter, the lithium compound complex hydroxide, for example lithium hydroxide was mixed with lithium oxide or lithium carbonate, and was heat-treated at a specific temperature range in an atmosphere of argon, the cathode active material _{Li x Cr y Mn 2-y} O 4 _{+ z} (2.2 <x <4
, 0 <y <2 and z ≧ 0).

[0035] Using the coprecipitation method, it is possible to prepare the _{Li x Cr y Mn 2-y} O 4 + z materials in a predetermined range. The coprecipitation method begins by preparing a mixed metal hydroxide from a soluble metal salt such as nitrate, sulfate, acetate or chloride. The metal salt is dissolved in deionized water and mixed with an aqueous alkaline solution under conditions of controlled temperature, pH and concentration. The resulting metal hydroxide is mixed with a lithium source such as lithium oxide, lithium hydroxide or lithium carbonate and calcined at various processing temperatures in an inert atmosphere. Heat treatment is used to complete the reaction and control the oxidation state of each transition metal. The oxidation state of the transition metal is important with respect to the crystal structure and electrochemical properties of the material. The temperature of the heat treatment and the oxygen content in the reaction vessel influence the oxidation state of the transition metal.

For example, coprecipitation of Cr—Mn composite hydroxide can be performed as follows. An aqueous solution containing a mixture of water-soluble chromium and manganese salts, a mixture of chromium nitrate and manganese nitrate or a mixture of chromium sulfate hydroxide and manganese sulfate is prepared by mixing a transition metal salt and deionized water. The coprecipitation of Cr hydroxide and Mn hydroxide is performed by adding ammonium hydroxide, potassium hydroxide,
It is carried out by controlled addition of an alkali-containing aqueous alkali solution such as sodium hydroxide, lithium hydroxide or mixtures thereof. The Cr-Mn composite hydroxide is then collected by filtering the precipitate and rinsing with water. The obtained composite hydroxide is dried in an oven at 100 ° C. The dried double hydroxide is lithium oxide,
Mix with a lithium source such as lithium hydroxide or lithium carbonate, and 600-
Heat treatment was performed in argon at various temperatures of 1000 ° C. for 24 hours. The powder of the material prepared by the coprecipitation method is also line diffraction analysis and typical electrochemical data are
This is shown in Example 4. The material with the best electrochemical properties is 650-750
It is a material that has been heat treated at ℃.

[0037] In a typical synthesis of _{Li x Cr y Mn 2-y} O 4 + z by the spray drying process,
The solution of metal salt is spray dried in a commercial spray dryer at 400-450 ° C.
It is thermally decomposed into oxides at the temperature of. Then, the dried metal oxide powder,
It was reacted with a lithium compound under controlled conditions. Suitable lithium compounds may include lithium oxide or any compound that can be thermally decomposed to an oxide, such as lithium hydroxide, lithium carbonate, lithium nitrate, lithium sulfate or lithium acetate. The mixture was carefully dried and calcined in air and heat treated in an argon atmosphere to make the active cathode material.

The compounds of formula (I) are further characterized by their X-ray diffraction patterns. More particularly, the powder X-ray diffraction pattern of the compound of formula (I) is similar to that of LiCrO ₂ . However, the reflection has moved to a relatively large diffraction angle, which corresponds to a relatively small crystal unit cell size. It is believed that the smaller the volume of the crystal unit cell, the higher the lithium content. The increase in lithium content must effectively replace some of the transition metal atoms with lithium atoms and be balanced by the partial oxidation of the remaining transition metal. When the transition metal atom is replaced by a lithium atom, for example, the oxidation state of manganese changes from +3 to +4.
May increase. This reduces the weight average ionic radius of the cations and consequently the crystal unit cell volume. This is Cr ³⁺ or Mn ³⁺ 1:
Substitution with a ratio of 2 Li ⁺ and Mn ⁴⁺ maintains charge balance and results in a relatively small average ionic radius.

The powder X-ray diffraction pattern of the compound of formula (I) is similar to that of LiCrO _{2 in} a hexagonal unit cell having a crystallographic structure belonging to the space group R-3m.
Although the crystallographic structure of the compound of formula (I) has not been determined in detail, the X-ray diffraction pattern can almost be demonstrated by a hexagonal crystal unit cell such as LiCrO ₂ . A comparison of crystallographic unit cell sizes between related structures provides information on relative bond lengths and oxidation states. A comparison of the volumes of related crystal structures is most informative between crystallographic structures that have the same number of atoms. _{Li x Cr y Mn 2-y} O 4 + z phase, there is no need to include a cation and an anion of the same number, by selecting the number of anionic and cationic sites in the crystal structure, to be made a comparison of volume I won't. When normalized for anionic sites of the same number, the crystal unit cell volume of the _{Li x Cr y Mn 2-y} O 4 + z compound is smaller than the volume of LiCrO _2.

[0040]   For example, LiCrO₂Is a = 2.899Å and c = 14.41TwoÅ (ICD
D card No. 24-600) hexagonal unit cell₃Cr_1.1Mn_0.9O_{Four .1} The powder X-ray diffraction pattern (from Example 2) is a = 2.87.6Å and c = 14.2
5ThreeIt can be shown that it is a hexagonal unit cell of Å. Corresponding crystal unit cell
The volume is LiCrO based on the hexagonal R-3m structure.₂Then 104.9ų as well as
Li₃Cr_1.1Mn_0.9O_4.1Then 102.1ų Is. Similarly, Li of Table 4 below _3.1 Cr_1.34Mn_0.66O_5.8Has a crystal unit cell volume of 102.92ų Is. This
On the contrary, Li having the same number of atomic sites₂CrMnO_FourThe crystal unit cell volume of
, 107.69ų(J. Power Sources, Vol. 81-82, p. 406-
411, 1999).

[0041]   The present invention has the formula Li_xCr_yMn_2-yO_{4 + z}(2.2 <x <4, 0 <y <2, and z
≧ 0) and an electrode composition containing the compound. With the active material of the electrode
Thus, in an embodiment of the invention using this compound, the initial composition has the formula Li_xCr_yMn _2-y O_{4 + z}(2.2 <x <4, 0 <y <2, and z ≧ 0), and
When using compounds, the composition varies from x to 0-4.

As mentioned above, the value of x is preferably on the large side of the range, ie about 2.2 to about 4, more preferably 2.5 to 3.6, in the middle of the range. Beneficial intermediate compounds from one x = about 2 to the smaller side of the range, near x = 0,
It is within the scope of the present invention.

As will become apparent below, these intermediate compounds charge and discharge a suitable battery starting at the cathode of a material of formula (I) wherein x is about 2.2 to about 4 (cycle To do).

In the use of materials as electrodes, structural changes may occur during the electrochemical cycle and the initial structure may not always be maintained. In the examples below, changes in the voltage distribution shape of the charge curve after the first charge suggest that substantial structural changes may occur.

As shown in the examples below, the compounds of the invention have very good chemical stability. Often, relatively good chemical stability promotes the safety of electrochemical cells. See, for example, U.S. Pat. Nos. 4,983,276, 4,956,248 and 4,110,696.

Preferred negative electrodes are based on carbonaceous products. Suitable carbonaceous materials include those mentioned above. (1) Carbonaceous material prepared by carbonization of furan resin having a d ₀₀₂ layer spacing of 3.70Å or less and a true density of 1.70 g / cm ³ or more, US Pat. No. 4,
, 959,281. (2) The above doped with 2 to 5% phosphorus and the carbonized carbon dioxide doped with 2 to 5% phosphorus and having the same d ₀₀₂ layer spacing and true density, European Patent Application Publication No. 0,418,514. (3) d ₀₀₂ obtained by thermal decomposition of a vapor-phase hydrocarbon or a hydrocarbon compound is 3
． 37 to 3.55Å carbon, according to US Pat. No. 4,863,814. (4) d ₀₀₂ Carbon made of mesophase fine spheres having a layer spacing of up to 3.45Å, according to US Pat. No. 5,153,082. (5) Commercial petroleum cake, US Pat. No. 4,943,497. (6) Isotropic graphite consisting of a mixture of graphite and carbonized pitch having a degree of graphitization of 0.4 or greater and heat treated fluid cake and commercial graphite, where the first electrochemical intercalation of lithium. Curation is according to US Pat. No. 5,028,500, which is carried out at a temperature of 50 ° C. or higher. (The descriptions of the six patent specifications referred to herein are included in the description of the present specification.)

[0047] Typical electrode hereof, 70 to 94% by weight of the active material, graphite carbon or the formula _{Li x Cr y Mn 2-y} O 4 + z, 5~20 wt% of the conductive promoter, For example, S
upper S carbon black and / or graphite, and 1 to 10% by weight
Of a binder such as poly (vinylidene fluoride) (PVDF) or Kynar Flex®.

Other conductivity enhancers, such as Shawinigan Acetylene Bl
It is also possible to use ack, graphite or other conductive materials. In addition, other binders such as Teflon®, ethylene propylene diene monomer (EPDM), polyolefins, or elastomers may be used in place of Kynar Flex.

From the examples below, it becomes clear that the compounds of the invention have the following distinguishing characteristics: They contain lithium in a greater molar fraction than previously known materials and therefore exhibit a relatively large theoretical capacity when used in lithium ion batteries. They are characterized by their composition, crystal unit cell size, x-ray diffraction pattern, and voltage curve shape. When used as a cathode in secondary lithium or lithium ion batteries, the compounds of the present invention exhibit significantly higher discharge capacity compared to conventional cathode materials. Moreover, secondary lithium or lithium ion batteries based on the compounds of the invention exhibit a relatively wide operating voltage range. A relatively wide operating voltage range results in a relatively fast recharge time and a relatively large current.

Example 1 For example, manganese acetate tetrahydrate (12.30) dissolved in 500 ml of deionized water.
g, 0.05mol) (Mn (CH 3 CO 2) 2 · 4H 2 O (Aldrich)) and chromium acetate hydroxide (10.05 g, about _{0.0167mol) (Cr 3 (OH)} 2 (
CH ₃ CO ₂ ) ₇ (Aldrich)) in a small commercial spray dryer (Buchi
190) and dried. The dried metal acetate mixture was calcined in air at 400 ° C. for 3 hours. 2.8 g of this oxide was slurried in 13 ml of 4M lithium hydroxide solution in deionized water and heat treated in an aluminum crucible in a tube furnace under air flow conditions. The heating conditions were controlled to slowly heat the sample to 450 ° C. for 5.5 hours, maintain at 450 ° C. for 2 hours, and allow the sample to cool slowly to room temperature in the furnace.

The sample was reground and 70% for 3 hours in argon gas flow conditions.
It was baked in a furnace at 0 ° C. FIG. 1 is an X-ray diffraction pattern of the sample after the heat treatment. This diffraction pattern can be compared to that of LiCrO ₂ shown by the bar graph below the diffraction pattern. Li _x Cr _y Mn _2-y diffraction pattern of O _{4 + z} sample is similar to the diffraction pattern of LiCrO _2, there are differences in the relative intensities of the peaks, also _{Li x Cr y Mn 2-y} O _{The 4 + z} peak shifts to a larger angle compared to LiCrO ₂ . Chemical diffraction of a sample by atomic absorption showed that the composition was Li (
3.30 ± 0.25) Mn (1.06 ± 0.08) Cr (0.94 ± 0.05)
It was shown to be O (5.54 ± 0.28). Here, the oxygen content was brought by the difference.

The material was cast into electrode sheets and tested in coin cell batteries. The electrode is 0.456g
Active material, 0.047 g Super S carbon black, and 0.049
It was prepared from a mixture of g of graphite (Lonza KS4). This mixture was mixed with 3% by weight of Kynar Flex in n-methylpyrrolidinone (NMP).
It was slurried with 1.206 g of binder solution containing 2801 and cast as a film on aluminum foil by the doctor blade method. The casting was dried on air on a hot plate with low heating and in a convection oven for 20 minutes at 110 ° C. Electrode disks with a diameter of 1.27 cm were stamped from the casting and each disk was compressed with 500 pounds of hydraulic pressure to densify. Typically, the electrode thickness after compression was 0.008-0.013 cm.

The electrochemical cycle was performed on 2325 coin cells. Here each cell holds internal springs and spacers to maintain the proper pressure on the stack of electrodes. The anode has a diameter of 1.65 cm and a thickness of 0.05 cm
Lithium (Foot Mineral) disk with 1: 1 electrolyte
1M LiPF ₆ in ethylene carbonate (EC) and dimethyl carbonate (DMC) (Mitsubishi Chemical).

The voltage distribution for the first 7 cycles of a cell cycled at 3.6 mA / g from 2.5 to 4.3 V is shown in FIG. The initial discharge capacity is 180mAh / g,
The average output pressure was 3.41V. A plot of discharge capacity vs. cycle number for this cell is shown in FIG. The discharge capacities of the other batteries cycled at 2.5 to 4.5 V are 187 to 200 mAh / g at 3.6 mA / g and 145 to 147 mAh at 14.4 mA / g, as shown in FIG. / G. 5 is initially 2
． Shown is a capacity vs. cycle number plot for a similar cell cycled from 5 to 4.3 V and then 2.5 to 4.5 V at 7.2 mA / g. This battery slowly reduces its capacity up to 75 cycles and has a discharge capacity of 179mA
up to h / g. FIG. 6 shows the discharge capacity vs. cycle number of a battery cycled at 3.6 mA / g, initially 2.5-4.3 V and then 2.5-4.5 V. The cells showed very good capacity retention for more than 30 cycles at discharge capacities above 195 mAh / g.

A portion of the sample was washed with water to remove all soluble residues and some of the material was cast into coin cells for testing. Atomic absorption analysis of the material after washing showed that Li (3.1
5 ± 0.32) Mn (1.11 ± 0.11) Cr (0.89 ± 0.06) O (5
． This corresponds to a composition of 00 ± 0.31). Here, the oxygen content was determined by the difference. FIG. 7 shows the powder X-ray diffraction patterns of the material before and after washing.

Electrodes were cast from the cleaned sample in the same manner as the uncleaned material. A cast of cleaned material was 0.406 g of active material, 0.050 g of Supe
r S, 0.054 g graphite, and 1.286 g Kyn in NMP
It contained a 3 wt% solution of ar Flex2801. Electrode disks were stamped from this cast and coin cells were tested as in the above example. This cast was used in a battery cycled at 2.5-4.5V at 7.2 mA / g.
In the first cycle, the discharge capacity of the cell was 182 mAh / g. FIG. 8 shows the distribution of the capacity and voltage of this battery. A voltage vs. capacity plot for another cell with a cathode stamped from the same casting is shown in FIG. The cell was cycled at 3.6 mA / g from 2.5 to 4.7 V in the first cycle and 2.75 to 4.7 V in the subsequent cycle. FIG. 10 shows a plot of discharge capacity vs. cycle number for the same cell. As can be seen from this figure, there is no significant decrease in the capacity and the discharge capacity of more than 185 mAh / g is maintained.
It was possible to cycle up to 4.7V over 0 cycles.

[0057] Both atomic absorption analysis of the washed sample and unwashed samples, they were shown to have a _{Li 2 Cr y Mn 2-y} O 4 phase relatively large containing lithium and oxygen. Comparison of the powder X-ray diffraction patterns of these samples against LiCrO ₂ clearly showed that the crystal unit cells were relatively small. The cycle up to 4.7V is
We have shown successful use of LiPF ₆ or LiBF ₄ electrolyte solutions.

Example 2 In this example, the initial mixture of manganese and chromium salts was 24.677 g.
Manganese acetate (Aldrich) and 22.075 g of chromium acetate hydroxide (
It was prepared by spray drying a 1 liter solution containing Aldrich). The metal salt was calcined in air for 4 hours at 475 ° C. 4.0
An amount of 14 g of the calcined product was added to 20.85 ml of 4M LiOH (Anache).
Mia) Combined with the aqueous solution to make a slurry. The mixture was slowly heated to 450 ° C. in air and maintained at this temperature for 2 hours. After cooling,
Samples were hand ground using a pestle and pestle and placed under argon flow conditions to 7
Transferred to an alumina boat for final heat treatment at 00 ° C. for 4 hours. The X-ray diffraction pattern of this sample is shown in FIG. According to Rietveld analysis of the diffraction pattern, the crystal unit cell size is a for hexagonal symmetric cells.
And b directions 2.87 6 Å, it was calculated in the c-direction is 14.2 5 Å. The crystal unit cell volume was calculated to be 102.1 cubic Å, which is LiCrO ₂
Is significantly smaller than 104.9 cubic Å. Chemical analysis by atomic absorption showed that the composition of this sample was Li _2.95 Mn _0.91 Cr _1.09 O _4.11 .

After hand grinding again 0.465 g of active material was added to 0.051 g of Super.
S carbon black, 0.052 g graphite (Lonza KS4),
And 1.131 g of a 4 wt% Kynar Flex 2801 solution in NMP into an electrode casting. Cathode disks cut from this casting were tested in coin cell batteries similar to those described in the above example. Figure 1
2 shows the voltage vs. capacity distribution for cells with these cathodes cycled at the indicated current densities. For the batteries cycled at various current densities, the charge and discharge capacities at the 1, 15, 30, and 50th cycles are shown in Table 1 above.
Is shown in. Two SEM micrographs of the spray dried product are shown in FIG.

Table 1-Charge / discharge capacities at 1, 15, 30 and 50th cycles of batteries cycled at 2.5-4.5V at the indicated current densities

[Table 1]

Example 3 The effect of increasing the concentration of metallic Cr and Mn on a stoichiometry of 20 from Li _x Mn _1.5 Cr _0.5 O _{4 + z} to Li _x Mn _0.5 Cr _1.5 O _{4 + z ′.} Studied using a spray drying process.

Solutions of various concentrations of Mn (CH ₃ CO ₂ ) ₂ and Cr ₃ (OH) ₂ (CH ₃ CO ₂ ) ₇ were prepared, spray dried in a commercial Buchi spray dryer, and 450 ° C. Pyrolyzed. The dried oxide was mixed with 4 g of 1 g of oxide and 5.2 ml of LiOH solution.
Mixed with M LiOH solution. The resulting slurry is dried, calcined in air by slowly heating to 450 ° C, and 450 ° C for 2 hours.
Maintained at. Grind this material by hand using an agate pestle and pestle,
Transferred to an alumina crucible and then heated at 700 ° C. for 4-5 hours under blanket conditions of argon gas flow. The composition by targeting and chemical analysis is shown in Tables 2 and 3, respectively, for chromium-rich and manganese-rich materials. The chemical analysis was performed by atomic absorption, and the oxygen composition was determined by the difference. The uncertainty of chemical analysis by atomic absorption is about 5-8 mol%. The discharge capacities of the cells cycled from 2.5 to 4.5 V at a current density of 7.2 mA / g are shown in Tables 2 and 3 for cycles 1, 10 and 20.

[0063]   221 for cycles of phases with relatively high Cr concentrations (shown as Cr-rich phases)
Discharge capacity up to mAh / g was observed. Li_3.1Cr_1.05Mn_0.95O_5.4 Of the composition of
The cell with the cathode has 50 cells at 7.2 mA / g, as shown in FIG.
It showed a stable capacity close to 180 mAh / g over the lane. Li_3.1Cr_1.10Mn _0.90 O_5.1, Li_3.3Cr_1.20Mn_0.80O_4.9And Li_2.8Cr_1.46Mn_0.54O_5.2
A cell with a cathode of the composition of 180 and 170 mAh at the same current density
It showed a very stable capacity of / g. X-ray diffraction patterns of samples A to J rich in chromium
15 are shown overlaid on FIG.

[0064] The composition and the discharge capacity in Table 2-Cr-rich _{Li x Cr y Mn 2-y} O 4 + z

[Table 2]

The X-ray diffraction patterns for a series of manganese-rich Samples AJ are shown in FIG. The discharge capacity at the 1st, 10th and 20th cycles when the battery having the cathode based on the manganese-rich material was subjected to charge / discharge cycles at a current density of 7.2 mA / g at 2.5 to 4.5 V is shown in Table 1. 3 shows. The manganese-rich material showed a very stable discharge capacity over the first 20 cycles. The battery having a cathode having a composition of Li _3.1 Mn _1.07 Cr _0.93 O _6.6 showed a capacity of 175 mAh / g at the 20th cycle, and a cathode having a composition of Li _2.8 Mn _1.10 Cr _0.90 O _4.5 and Li _3.1 Mn _1.15 Cr _0.85 O _4.7. Batteries with 145 and 150mAh at 20th cycle
It showed a capacity of / g.

[0066] The composition and the discharge capacity in Table 3-Mn rich in _{Li x Cr y Mn 2-y} O 4 + z

[Table 3]

[0067] Example 4   The effect of increasing lithium content was studied using the spray drying method. Example 1 and
Two samples were prepared as shown in 2. However, here, the calcined metal salt
The proportion of the lithium hydroxide solution was increased. Atomic absorption analysis of first and second samples
Have a composition of Li_3.48Mn_0.96Cr_1.04O_4.80And Li_3.61Mn_0.97Cr _1.03 O_5.49It was shown that. Using these samples as electrodes, as in the previous example
Then, electrochemical evaluation was performed using a coin battery. FIG. 17 shows that at 3.6 mA / g
For the first three cycles of the battery cycled from 2.5 to 4.5V
, Shows a voltage vs. capacity plot for the first of these samples. The first three times
The discharge capacity of the cycle of 222, 237 and 233 mAh / g (active cathode material
The charge was in grams. FIG. 18 shows the discharge capacity vs. cycle number for the same battery.
It is a plot. As can be seen from the figure, the capacity close to 215 mAh / g is 40
Has been maintained over the cycle. The same sample is not
It was also evaluated with the coin type battery. FIG. 19 shows that at a current density of 14.4 mA / g.
The discharge capacity of the first 100 cycles of the battery cycled between 2.5 and 4.5V
I'm plotting. Discharge capacity close to 150mAh / g maintained at 100th cycle
It had been. The second sample was tested as in the previous example. Second sample caustic
2.5 to 4.5V cycle at 3.6mA / g with coin type battery
I went. As shown in Figure 20, the discharge capacity of the first 32 cycles is
After the icicle, it is fairly constant at about 210 mAh / g.

Example 5 A process for preparing Cr-Mn hydroxide by co-precipitation according to the present invention is described. A 2M aqueous chromium nitrate solution was prepared by adding a specific amount of manganese nitrate (depending on the target Cr / Mn ratio) to the solution and adjusting the final composition with water. The solution of concentrated transition metal nitrate was slowly poured into an aqueous caustic solution containing 6M sodium hydroxide, resulting in coprecipitation of Cr hydroxide and Mn hydroxide. The precipitation was completed when the pH of the mixed solution reached 10.

Cr-Mn double hydroxide was obtained by filtering the precipitate and rinsing with water.
The rinsing with water was performed while continuously measuring the pH until the pH value reached 6 to 7. The obtained double hydroxide was dried in air at 100 ° C. Other precursors such as chromium sulfate and manganese sulfate can also be used as Cr and Mn sources, respectively. Any combination of metal salts that can be in aqueous solution can be used. Potassium hydroxide, ammonium hydroxide, and lithium hydroxide can be used as the caustic solution.

The firing process using a Li compound is described below. As the Li compound,
Use lithium hydroxide. The Cr-Mn double hydroxide obtained by the coprecipitation method described above was mixed with lithium hydroxide, the mixture was placed in an alumina crucible and calcined in a horizontal tube furnace under argon gas flow conditions. The sample was calcined at 650-700 ° C for 24 hours. After calcination, the product was gradually cooled to room temperature, ground into powder and used as cathode active material.

After preparing a plurality of active materials having different Li / Cr / Mn ratios, each sample was examined by X-ray diffraction analysis. The cathode was 85 wt% active material in NMP, 10 wt% acetylene black and 5 wt% fluorinated polyvinylidene (PV
DF) was made by casting and drying a slurry. The substrate was Al foil and the diameter of the punched cathode was 10 mm. The anode was prepared by stamping a metallic lithium film, which was 0.8 mm thick and 12 mm in diameter. Immediately after the electrode, type number 2016
Selected to fit the commercial coin-cell battery cases of. Immediately after these coin type batteries were 20 mm and the height was 1.6 mm.

The cell stack is made up of a stack of three layers, a cathode, a cell separator and a lithium anode. The separator used was a polypropylene film. The electrolyte used was a 50/50 volume fraction mixture of ethylene carbonate and dimethyl carbonate containing 1 M LiPF ₆ . The cell was assembled and fixed in a helium-filled glove box. Coin type battery is 3.6mA
The current density and the voltage range of / g were 4.3 to 2.5 V, and the battery was charged and discharged.

FIG. 21 shows that Li _x Cr _y Mn _2-y O _{4 + z} (x = 2.65, y = 0.75, z = 1.
86) shows the X-ray diffraction pattern. FIG. 22 shows the charge and discharge curves for the active material of this formula. Table 4 shows the charge and discharge capacity results for various equations. The atomic ratio of Li, Cr and Mn was determined by atomic absorption analysis. The oxygen content was determined by the difference. Lattice parameters: a, b and c are in Angstroms and the unit cell volume is in cubic Angstroms.

[0074] Table 4-Typical examples of co-precipitation process

[Table 4] ( ^* No. 1 sample was heated at 800 ℃, ^** sample was made by solid process)

[0075] Example 6 other samples, instead of nitrate, using a chromium sulfate _{Cr 2 (SO 4) 3 xH} 2 O and manganese sulfate MnSO ₄ · H ₂ O, by coprecipitation process described in Example 5 Prepared. Precipitation of the mixed transition metal hydroxide was initiated by the limited addition of ammonium hydroxide. The mixed hydroxide was combined with lithium hydroxide monohydrate and heated at 650 ° C. for 24 hours under argon gas flow conditions.
The X-ray diffraction pattern of the product is shown in Figure 23.

A scanning electron micrograph comparing a sample prepared by the co-precipitation process using either nitrate or nitrate with a sample prepared by the solid state process at 1000 ° C. is shown in FIG.

FIGS. 25 and 26 show plots of discharge capacity vs. cycle number for four cells with cathodes made of compounds made by a coprecipitation process from nitrates or sulfates. All cells were cycled in the voltage range of 2.5-4.3V. The two shown in Figure 25 were cycled at 3.6 mA / g and the one in Figure 26 was tested at a current density of 14.5 mA / g. The compositions measured by atomic absorption are shown in Figures 24-26.

[Brief description of drawings]

[Figure 1]   3 is an X-ray diffraction pattern of a sample prepared according to Example 1.

[Fig. 2]   2 shows the specific capacity versus voltage of an electrochemical cell prepared according to Example 1.

[Figure 3]   2 shows the specific capacity versus cycle number of an electrochemical cell prepared according to Example 1.

[Figure 4]   2 shows the specific capacity versus voltage of an electrochemical cell prepared according to Example 1.

[Figure 5]   2 shows the specific capacity versus cycle number of an electrochemical cell prepared according to Example 1.

[Figure 6]   2 shows the specific capacity versus cycle number of an electrochemical cell prepared according to Example 1.

[Figure 7]   FIG. 4 is a superimposition of X-ray diffraction patterns of the sample described in Example 1.

[Figure 8]   1 shows the voltage distribution of an electrochemical cell prepared according to Example 1.

[Figure 9]   1 shows the voltage distribution of an electrochemical cell prepared according to Example 1.

FIG. 10 is a plot of capacity vs. cycle number for an electrochemical cell charged and discharged under the conditions shown in Example 1.

FIG. 11   3 shows an X-ray diffraction pattern for the sample of Example 2.

FIG. 12 shows the discharge voltage distribution of a battery assembled and tested as described in Example 2.

[Fig. 13]   3 shows an SEM micrograph of a sample prepared according to Example 2.

FIG. 14 shows a plot of specific capacity for cells prepared and tested as described in Example 3.

FIG. 15   The X-ray diffraction pattern of the sample prepared according to Example 3 is shown superimposed.

FIG. 16   The X-ray diffraction pattern of the sample prepared according to Example 3 is shown superimposed.

FIG. 17 shows the specific capacity as a function of voltage for an electrochemical cell prepared and tested according to Example 4.

FIG. 18 shows the specific capacity as a function of cycle number for an electrochemical cell prepared and tested according to Example 4.

FIG. 19 shows the specific capacity as a function of cycle number for an electrochemical cell prepared and tested according to Example 4.

FIG. 20 shows the specific capacity as a function of cycle number for an electrochemical cell prepared and tested according to Example 4.

FIG. 21   6 shows an X-ray diffraction pattern of a sample prepared as described in Example 5.

FIG. 22 plots voltage versus capacity for an electrochemical cell assembled and tested according to Example 5.

FIG. 23   7 shows an X-ray diffraction pattern of a sample made according to Example 6.

FIG. 24   7 shows an SEM micrograph of the sample described in Example 6.

25 is a plot of specific capacity for an electrochemical cell assembled and tested as described in Example 6. FIG.

FIG. 26 is a plot of specific capacity for an electrochemical cell assembled and tested as described in Example 6.

─────────────────────────────────────────────────── ─── Continued front page    (81) Designated countries EP (AT, BE, CH, CY, DE, DK, ES, FI, FR, GB, GR, IE, I T, LU, MC, NL, PT, SE), OA (BF, BJ , CF, CG, CI, CM, GA, GN, GW, ML, MR, NE, SN, TD, TG), AP (GH, GM, K E, LS, MW, SD, SL, SZ, TZ, UG, ZW ), EA (AM, AZ, BY, KG, KZ, MD, RU, TJ, TM), AL, AM, AT, AU, AZ, BA, BB, BG, BR, BY, CA, CH, CN, CR, C U, CZ, DE, DK, DM, EE, ES, FI, GB , GE, GH, GM, HR, HU, ID, IL, IS, JP, KE, KG, KP, KR, KZ, LC, LK, L R, LS, LT, LU, LV, MA, MD, MG, MK , MN, MW, MX, NO, NZ, PL, PT, RO, RU, SD, SE, SG, SI, SK, SL, TJ, T M, TR, TT, TZ, UA, UG, US, UZ, VN , YU, ZW (72) Inventor Yo, Yong-chan             Ontario, Canada 2G 5C             -2, Nepeen, Center Point Dora             Eve 164 (72) Inventor Sun, Do-Youn             South Korea, Seoul, Schoog, Scho             Don, Shindo Inn-A, Apartment Men             To 7-1110 (72) Inventor Davidson, Isobel             Ontario K, Canada 4A 2D             Cox 7, Orleans, Delia Cresse             Nt 1569 F-term (reference) 4G048 AA04 AB02 AB06 AC06 AD06                       AE05 AE08                 5H029 AJ02 AJ03 AJ05 AK03 AL02                       AL04 AL06 AM00 AM02 AM03                       AM05 AM07 AM16 BJ03 BJ12                       DJ17 HJ02 HJ13                 5H050 AA02 AA07 AA08 BA17 BA18                       CA07 CB02 CB05 CB07 FA02                       FA19 HA02 HA13

Claims (22)

[Claims] 1. A compound represented by the following formula _{(I): Li x Cr y} Mn 2-y O 4 + z (I) (2.2 <x <4,0 <y <2, and z ≧ 0 ). 2. The method according to claim 1, wherein 2.2 <x <4 and 0.1 ≦ y ≦ 1.75.
The compound according to. 3. The compound according to claim 1, wherein 2.2 <x <3.6 and 0.1 ≦ y ≦ 1.75. 4. The standardized crystal unit cell volume is smaller than that of LiCrO ₂ when it is assumed to be hexagonal symmetrical with respect to the R-3m structure, that is, 104.9Å
The compound of claim 1, further characterized by being less than. 5. The compound according to claim 1, further characterized in that the average distance between the cation and the anion is smaller than that of LiCrO ₂ . 6. x = 2.8-3.4, y = 0.49-1.46 and z = 0.
The compound according to claim 1, which is 5 to 2.6. 7. x = 2.8 to 3.4, y = 1.01 to 1.46 and z = 0.
The compound according to claim 1, which is 9 to 1.9. 8. x = 2.8-3.3, y = 0.49-0.93 and z = 0.
The compound according to claim 1, which is 5 to 2.6. 9. x = 2.04 to 3.44, y = 0.51 to 1.34 and z =
The compound according to claim 1, which is 0.07 to 1.86. 10. x = 2.25-3.44, y = 0.98-1.34 and z.
The compound according to claim 1, wherein = 0.37 to 1.86. 11. x = 3.15-3.30, y = 0.89-1.09 and z
= 1.00-1.54, The compound according to claim 1. 12. standardized unit cell volume is 102.1 Å, and when as a hexagonal crystal unit cell, is a = 2.87 6 Å size, b = 2.87 6 Å, and further characterized in that c = 14.2 5 angstroms, x = 2.95, y = 1.09 and z =
A compound according to claim 1 of 0.11. 13. A cathode for use in a secondary lithium-ion battery, which comprises the compound (I) shown in claim 1 as an active material. 14. A secondary lithium comprising a lithium intercalation anode, a suitable non-aqueous electrolyte containing a lithium salt, the cathode of claim 13, and a separator between the anode and the cathode. Ion electrochemical battery. 15. The anode comprises a material selected from the group consisting of transition metal oxides, transition metal sulfides and carbonaceous materials, and the electrolyte comprises a liquid and a suitable organic solvent. 14. The compound according to 14. 16. The lithium salt is LiAsF ₆ , LiPF ₆ , or LiBF _4.
, LiClO ₄ , LiBr, LiAlCl ₄ , LiCF ₃ SO ₃ , LiC (CF ₃ S
_{O 2) 3, LiN (CF} 3 SO 2) 2, and are selected from the group consisting of mixtures, electrochemical cell of claim 15. 17. The organic solvent is propylene carbonate, ethylene carbonate, 2-methyltetrahydrofuran, tetrahydrofuran, dimethoxyethane, diethoxyethane, dimethyl carbonate, diethyl carbonate, methyl acetate, methyl formate, γ-butyrolactone, 1,3. The electrochemical cell according to claim 16, selected from the group consisting of: dioxolane, sulfolane, acetonitrile, butyronitrile, trimethyl phosphate, dimethylformamide and other similar organic solvents, and mixtures thereof. 18. The electrochemical cell according to claim 17, wherein the anode comprises a carbonaceous material. 19. The electrochemical cell of claim 18, wherein the anode comprises graphitic carbon. 20. The electrolyte according to claim 18, which is a solid or gel polymer.
The electrochemical cell according to. 21. The electrochemical cell of claim 18, wherein the electrolyte contains 1M LiPF ₆ in a 1: 1 mixture of ethylene carbonate and dimethyl carbonate. 22. The electrochemical cell according to claim 19, wherein x = 2.2-4, y = 0.1 to 1.75 and z ≧ 0.