Classifications

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  • H01M4/36—Selection of substances as active materials, active masses, active liquids
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  • H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
  • H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
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  • C01G45/12—Manganates manganites or permanganates
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  • C01G45/1221—Manganates or manganites with a manganese oxidation state of Mn(III), Mn(IV) or mixtures thereof
  • C01G45/1278—Manganates or manganites with a manganese oxidation state of Mn(III), Mn(IV) or mixtures thereof of the type [Mn2O7]n-, e.g. (Sr2-xNdx)Mn2O7, Tl2Mn2O7
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  • C01G45/1221—Manganates or manganites with a manganese oxidation state of Mn(III), Mn(IV) or mixtures thereof
  • C01G45/1285—Manganates or manganites with a manganese oxidation state of Mn(III), Mn(IV) or mixtures thereof of the type [Mn2O5]n-
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  • H01M10/05—Accumulators with non-aqueous electrolyte
  • H01M10/052—Li-accumulators
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  • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
  • H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
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  • H01M4/362—Composites
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  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M4/36—Selection of substances as active materials, active masses, active liquids
  • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
  • H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
  • H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
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  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M4/36—Selection of substances as active materials, active masses, active liquids
  • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
  • H01M4/5825—Oxygenated metallic salts or polyanionic structures, e.g. borates, phosphates, silicates, olivines
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  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M4/36—Selection of substances as active materials, active masses, active liquids
  • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
  • H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
  • H01M4/587—Carbonaceous material, e.g. graphite-intercalation compounds or CFx for inserting or intercalating light metals
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  • C01P2002/70—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data
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• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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  • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
  • Y02E60/10—Energy storage using batteries

Definitions

• the technical field of the invention is that of electrochemically active materials intended to be used in the positive electrode (or cathode) of a rechargeable electrochemical element (or accumulator) of the lithium-ion type.
• a lithium-ion electrochemical element The operation of a lithium-ion electrochemical element is based on the principle of the reversible insertion of lithium into a host structure of an electrochemically active material.
• the electrochemically active material of the positive electrode oxidizes and disinserts from its structure of lithium while the electrochemically active material of the negative electrode is reduced and lithium is inserted into its structure.
• the electrochemically active material of the positive electrode is reduced and inserts in its structure of lithium while the electrochemically active material of the negative electrode oxidizes and lithium is disinserts from its structure.
• Graphite is commonly used as the electrochemically active material of the negative electrode of a lithium-ion element.
• a passivation layer is formed by decomposition of the electrolyte contained in the element on the surface of the negative electrode. The formation of this is necessary because it avoids the exfoliation of graphite, leading to a high irreversible capacity, preventing the co-intercalation of solvent.
• This passivation layer consumes lithium which will no longer be used for insertion and disinsertion and therefore will not participate in subsequent discharges. It is at the origin of an irreversible capacity of the negative electrode.
• lithium-ion electrochemical cells are characterized by an irreversible capacity of the negative electrode greater than that of the positive electrode.
• the electrochemical elements comprising a negative electrode based on graphite and a positive electrode based on L1COO2, or based on lithiated oxide of nickel, manganese and cobalt (NMC), or on the basis of lithiated oxide of nickel, cobalt and aluminum (NCA), or based on LiFePO 4 or
• the positive electrode and the negative electrode have the same total capacitance but have different irreversible capacitances.
• the positive electrode has an irreversible capacitance lower than that of the negative electrode. Since the discharge of the electrochemical element is limited by the electrode having the lowest reversible capacitance, the discharge of the element will stop when the reversible capacitance of the negative electrode has been completely used. Therefore, there is in the positive electrode a fraction of electrochemically active material that will not be used during the discharge of the electrochemical element. This unused fraction corresponds to the difference in area of the two hatched surfaces. This fraction of positive active material not exploited represents a certain mass and a certain volume of the positive electrode. It therefore penalizes the mass capacity and the volume capacity of the electrochemical element.
• Li 2 Ni0 2 which has a total capacity of 350 mAh / g. This active ingredient is described in Chem. Mater. 2010, 22, 1263-1270.
• Li 5 FeO 4 which has a capacity of 700 mAh / g. This active ingredient is described in Electrochemica Acta 108, 2013, 591-595.
• WO 2015/011883 discloses a sacrificial positive active ingredient of formula Li 6 MnO 4, that is (Li 2 O) o, 75 (MnO) o, 2.
• the disadvantage of this active ingredient is that it must be loaded with a high potential, that is to say greater than 4.4 V relative to the lithium metal.
• the charge potential indicated in FIG. 8 of document WO 2015/011883 is indeed 4.5 V. Such a potential is detrimental to the lifetime of the electrochemical element.
• this figure shows that for a charging voltage of 4.4 V, the charged capacity is less than 450 mAh / g. For a charging voltage of 4V, the charged capacity is less than 100 mAh / g, which is very low. It is therefore sought a sacrificial positive active material having a higher loaded capacity and for a charge potential relative to lithium not exceeding 4.4V.
• the invention provides novel compounds useful as a sacrificial positive active material. These compounds have a high irreversible capacity, preferably
• a first subject of the invention is a compound of formula
• M is selected from the group consisting of Fe, Co, Ni, B, Al, Ti, Si, V, Mo, Zr and a mixture thereof.
• This compound can crystallize in the cubic system.
• It may have an X-ray diffraction pattern in which the width at mid-height of the line at a 2theta angle between 40 ° and 45 ° is greater than 1 °, the wavelength used being Kalpha wave of copper.
• y z +/- 0.05.
• y ⁇ 0.2, preferably y 0 0, 1.
• z ⁇ 0.4 preferably z ⁇ 0.3, more preferably z ⁇ 0.2, more preferably z ⁇ 0.1.
• t 0.
• a second subject of the invention is a composite material comprising the compound as described above and a Li 2 0 crystalline phase.
• a third subject of the invention is an electrode comprising a first electrochemically active sacrificial material which is the compound as described above and at least one second electrochemically active material.
• the second electrochemically active material is selected from the group consisting of:
• M or M 'or M "or M” is selected from Mn, Co, Ni, or Fe;
• M, M ', M "and M" being different from each other; with 0.8 ⁇ x ⁇ l, 4; 0 ⁇ y ⁇ 0.5; 0 ⁇ z ⁇ 0.5; 0 ⁇ w ⁇ 0.2 and x + y + z + w ⁇ 2;
• the electrode comprises compound ii) and
• M is Ni
• M '" is selected from the group consisting of B, Mg, Al, Si, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Cu,
• the electrode comprises compound ii) and
• M is Ni
• the electrode comprises compound ii) and
• x 1; 0.6 ⁇ 2-x-y-z ⁇ 0.85; 0.10 ⁇ y ⁇ 0.25; 0.05 ⁇ z ⁇ 0.15.
• the electrode comprises compound ii) of formula LiCoO 2 .
• the electrode comprises compound iv).
• compound iv) has the formula LiFePO 4 .
• Compound iii) can have the formula LiMn 2 0 4 .
• the weight percentage of the compound as described above is less than or equal to 5% relative to the total weight of all the electrochemically active materials, preferably less than or equal to 2%.
• a fourth subject of the invention is an electrochemical element of lithium-ion type comprising a positive electrode as described above.
• the electrochemical element comprises:
• At least one negative electrode comprising a graphite-based active material
• At least one positive electrode comprising at least one of the compounds i) to v) described above, or a mixture thereof.
• the electrochemical element comprises:
• At least one negative electrode comprising an active material selected from the group consisting of tin, silicon, compounds based on carbon and silicon, compounds based on carbon and tin, compounds based on carbon , tin and silicon; compounds based on lithium titanium oxide, such as lithium titanate Li 4 Ti 5 0i 2
• At least one positive electrode comprising the compound according to the invention.
• a fifth subject of the invention is a process for manufacturing the compound as described above, said process comprising the steps of:
• Figure la shows schematically the capabilities of the positive electrode and the negative electrode of a lithium-ion electrochemical element according to the prior art in which the irreversible capacity of the negative electrode is greater than that of the positive electrode.
• FIG. 1b shows schematically the capabilities of the positive electrode and the negative electrode of a lithium-ion electrochemical element according to the invention in which the difference between the irreversible capacity of the positive electrode and the irreversible capacity of the electrode. negative has been reduced compared to the situation illustrated in Figure la.
• FIG. 2 is a ternary diagram (Li 2 0, MnO, MnO 2 ) showing the composition domain to which the compound according to the invention belongs and the position in this field of the compounds of the examples of Table 1 below.
• FIG. 3 is an X-ray diffraction pattern of a powder of the compound of Example 1 L1 9 MnO 6 according to the invention.
• FIG. 4 is an X-ray diffraction pattern of a powder of the compound of Example 7 LiMoMn 2 0 7 according to the invention.
• FIG. 5 represents the galvanostatic cycling curve of the compound of example 1 in half-stack versus lithium of Swagelok® type.
• Figure 6 shows the galvanostatic cycling curve of the compound of Example 7 half-stack versus lithium Swagelok® type.
• Figure 7 is a ternary diagram (Li 2 0, MnO, MnO 2 ) showing the position of the compounds of Table 3 below as counterexamples.
• FIG. 8a represents the cycling curve of a reference electrode A and an electrode B comprising the compound of example 1.
• the abscissa axis is graduated in mAh / cm 2 .
• FIG. 8b represents the cycling curve of a reference electrode A and an electrode B comprising the compound of example 1 under the same conditions as those of FIG. 8a.
• the x-axis is graduated in mAh / g.
• the compound according to the invention has the formula (Li 2 O) x (MnO 2 ) y (MnO) z (MO a ) t in which:
• M is selected from the group consisting of Fe, Co, Ni, B, Al, Ti, Si, V, Mo, Zr and a mixture thereof.
• This formula defines a domain of compositions. This range of compositions can be represented in a ternary diagram. Assuming that the element M is absent from the compound, the formula of the compound according to the invention can be rewritten as follows:
• Li 2 0, Mn0 2 and MnO are the three vertices of this ternary diagram.
• Criterion 1 x> 0.6
• Criterion 4 y + z> 0
• Criterion 5 1-x-y> 0
• Figure 2 shows the composition domain in the ternary diagram. This domain is delimited by a thick line. The points included in this area satisfy the five criteria above.
• x is preferably greater than or equal to 0.7, more preferably x is greater than or equal to 0 , 8, more preferably x is greater than or equal to 0.9.
• the compound according to the invention is generally nanostructured.
• the size of the crystallites is typically less than 50 nm, preferably less than or equal to 10 nm, more preferably less than or equal to 5 nm.
• This nanostructure can be demonstrated by using the X-ray diffraction technique.
• the X-ray diffraction diagram produced on a powder of the compound has a peak located at a 2 theta angle between 40 ° and 45 °, whose width at half height is greater than 1 °.
• the wavelength used for the measurement is the Kalpha wavelength of copper.
• the width at half height may be greater than or equal to 2 °, greater than or equal to 3 °. It has been observed that the width at half height of the peak increases when the size of the crystallites decreases.
• a peak mid-height width of the order of 2 ° corresponds to a crystallite size of the order of 5 nm.
• the compound according to the invention generally crystallizes in the cubic system.
• the cubic system can be evidenced using the Rietveld affine method which uses the X-ray diffraction technique.
• a second phase Li 2 0 is generally present with the compound of the invention.
• the X-ray diffraction pattern characteristic of the presence of the Li 2 0 phase has peaks at the following 2 theta angles: 34 °, 39 °, 56 °, 71 ° and 84 ° ⁇ 1 °, the angle being obtained by using the Kalpha wavelength of copper.
• the compound according to the invention is generally used in admixture with at least one second electrochemically active material.
• This second electrochemically active material may be selected from the group consisting of:
• M, M ', M "and M" being different from each other; with 0.8 ⁇ x ⁇ l, 4; 0 ⁇ y ⁇ 0.5; 0 ⁇ z ⁇ 0.5; 0 ⁇ w ⁇ 0.2 and x + y + z + w ⁇ 2;
• the compound according to the invention may be used in admixture with one or more electrochemically active substances which may form part of compounds i) to v) or which may not be part of it.
• the lithium ion electrochemical element comprises:
• At least one positive electrode comprising the compound according to the invention in a mixture with one or more of the compounds i) to v).
• the electrochemical element comprises: at least one negative electrode based on graphite,
• Compound iv) is advantageously LiFePC.
• the use of a compound according to the invention in an electrochemical element comprising a positive electrode comprising a compound of type iv) makes it possible to increase the energy density of the element by approximately 8 to 9%.
• the electrochemical element comprises:
• At least one positive electrode comprising the compound according to the invention mixed with another electrochemically active positive material.
• carbon is mixed with the compound according to the invention and with any other electrochemically active material present in the positive electrode.
• the mass proportion of carbon used generally represents 3 to 10% of the sum of the masses of the active active ingredients.
• the process used to obtain the compound according to the invention is a mechanosynthesis process.
• Mechanosynthesis is understood to mean all material techniques in which the activation energy of the chemical reaction between precursors is provided by mechanical means.
• the manufacturing process comprises the steps of:
• step f optionally grinding the mixture under an inert atmosphere if carbon has been added in step f).
• the heating step c) is carried out for a period ranging from 3 to 5 hours.
• step c) of heating the mixture is carried out at a temperature ranging from 850 to 950 ° C, preferably 900 ° C, for a period ranging from 3:30 to 4:30, preferably 4 hours.
• the rise in temperature to the desired temperature is carried out gradually over a period ranging from 4 to 6 hours, preferably 5 hours.
• step d) of cooling to room temperature is carried out progressively over a period ranging from 4 to 6 hours, preferably 5 hours.
• step e) of grinding the mixture is carried out for a period ranging from 13 to 17 hours.
• step e) of grinding the mixture is carried out for a period of about 15 hours.
• step g) of grinding the mixture is carried out for a period ranging from 4 to 6 hours.
• the method according to the invention makes it possible to obtain a stabilization of the cubic phase as well as a nanostructuration of the compound.
• the Li 2 0, MnO, MnO 2 and MO precursors were ground in a stoichiometric ratio in a glove box under an argon atmosphere (total mass of precursors: 5 g). Then, heat treatment in sealed tube was carried out for 4 hours at 900 ° C. The rise in temperature up to 900 ° C occurred in 5 hours, likewise for the descent in temperature up to 25 ° C.
• the obtained material was then milled for 15 hours under an argon atmosphere, in 10 ml WC tungsten carbide bowls with 4 WC beads of 10 mm diameter, using a FRITSCH TM planetary mill.
• the milling speed is 700 rpm.
• the grinding was stopped and the walls of the bowl were scraped in a glove box to homogenize the powder which is compacted on the walls.
• 10 cycles of 30 minutes with 5 minutes pause were carried out, alternating the direction of rotation of the grinding bowls.
• FIG. 2 The position of the compounds 1-10 in a ternary diagram is shown in FIG. 2.
• a fourteenth example of a compound which is part of the invention but not synthesized is Li 1 O 10 Mn 50 O 2, 5 which has a theoretical mass capacity of 1500 mAh / g.
• Example 1 of formula Li 9 MnO 6 was studied from the point of view of its crystallographic structure.
• An X-ray diffraction pattern was made on a powder of this compound. It is reproduced in Figure 3.
• This figure shows a peak located at a 2 theta angle of 43.5 °. This peak has a width at mid-height of about 3 °, which indicates that the compound is nanostructured.
• Rietveld refinement of the diagram indicates that this compound crystallizes in the cubic system. It also indicates the presence of a Li 2 0 secondary phase.
• Example 7 of formula Li 10 Mn 2 O 7 was also studied from the point of view of its crystallographic structure.
• An X-ray diffraction pattern was made on a powder of this compound. It is reproduced in Figure 4.
• This figure shows a peak located at a 2 theta angle of 41.5 °. This peak has a width at half height of about 3 °. This indicates that the compound is nanostructured.
• the compound LieMnC ⁇ described in WO 2015/01 1883, cited in the discussion of the prior art, is not nanostructured. Indeed, if we refer to the FIG. 14 of WO2015 / 011883, it may be noted that the peak situated at a 2 theta angle between 40 and 45 ° has a half-height width of less than 0.3 °, which means that the size of the crystallites is greater than at 50 nm. Electrical Tests:
• the electrical tests were performed in electrochemical laboratory elements of Swagelok® type.
• the positive electrode has a surface of 1.14 cm 2 and consists of 20 to 30 mg of a mixture comprising 72% by weight of electrochemically active material and 28% by weight of carbon. The mixture was previously mixed with the FRITSCH TM planetary mill for 30 minutes at 450 rpm.
• the negative electrode consists of a lithium disk with a large excess of capacity relative to the positive electrode. The thickness of the lithium disk is 500 ⁇ . Both electrodes are electrically insulated by two layers of borosilicate fiberglass separators (Whatman TM).
• the electrolyte used is composed of 1M LiPF 6 dissolved in a mixture of ethylene carbonate and ethyl methyl carbonate EC: EMC in a mass proportion of 3: 7.
• the cutoff voltage of the first load is 4.4V and 1.2V for the discharge.
• the cutoff voltage of the second load is 4.6V and 1.2V for the discharge.
• the cutoff voltage of the third load is 4.8V and 1.2V for discharge.
• Table 2 shows that the compounds according to the invention have, for a charging voltage of 4.4V, a total capacity charged of at least 630 mAh / g, up to 1200 mAh / g.
• the galvanostatic cycling curve of the compound of Example 7 of formula Li 10 Mn 2 0 6 , in half-cell versus lithium (of Swagelok® type) is represented in FIG. 6.
• This figure shows that at a charging regime corresponding to the deinsertion of a lithium atom in 20 hours by compound formula, nearly 8.6 lithium atoms per formula of compound are extracted from the structure (797 mAh / g) in first charge and 2.8 lithium atoms per formula compound are reinserted when the discharge ere (260 mAh / g).
• the validation of the invention was carried out by comparing two positive electrodes, one based on LiFePO 4 (electrode A) and the second one by replacing 2% of this compound with the compound Li 9 MnO 6 with a capacity of 1125 mAh / g (electrode B). This substitution makes it possible to create an irreversible capacity of approximately 20 mAh / g of positive active material.
• the reference electrode A was manufactured with the following mass composition: 77% LiFePO 4 /23% carbon.
• the electrode B according to the invention was manufactured with the following mass composition: 75.5% LiFePO 4 / 1.5% Li 9 MnO 6 /23% carbon.
• the mass of Li 9 MnO 6 represents approximately 2% of the sum of the masses of active active ingredients.
• the mixture of active material (s) and carbon is deposited on a current collector of the positive electrode at a rate of 12.65 mg / cm 2 .
• FIGS. 8a and 8b The charge-discharge curves of each of these electrodes have been plotted. They are represented in FIGS. 8a and 8b.
• Figure 8a shows that:
• the charged capacity of the electrode A is 1.85 mAh / cm 2 and the charged capacity of the electrode B is 2.15 mAh / cm 2 , ie an additional capacity of about 0.3 mAh / cm 2 for the electrode B containing the compound according to the invention.
• the capacity discharged according to the first charge is identical for electrode A and electrode B. It is approximately 1.85 mAh / cm 2 .
• FIG. 8b shows the cycling curve of the electrodes A and B under the same conditions as those of FIG. 8a, with the difference that the abscissa axis is graduated in mAh / g and that the starting points of the discharge curves of the electrodes A and B are not superimposed.
• the total capacity charged during the first charge for electrode A is 165 mAh / g and that of electrode B is 185 mAh / g.
• the capacity measured during the first discharge is identical for the two electrodes, which means that the irreversible capacitance has indeed been increased by 20 mAh / g as expected.
• the increase in the mass capacity of a lithium ion electrochemical element by the use of a compound according to the invention in the positive electrode can be verified by calculation. The assumptions used are as follows:
• a reference electrochemical element R comprises:
• a negative electrode containing an active material consisting of 100% of a C / Si composite a negative electrode containing an active material consisting of 100% of a C / Si composite.
• An electrochemical element I according to the invention comprises:
• a negative electrode containing an active material consisting of 100% of a C / Si composite a negative electrode containing an active material consisting of 100% of a C / Si composite.
• LiFeP0 4 used in the two elements R and I described above has a total mass capacity of 165 mAh / g, of which 9% is constituted by the irreversible mass capacity, 15 mAh of irreversible capacity.
• the C / Si composite used in the two elements R and I described above has a total mass capacity of 1266 mAh / g, 21% of which consists of the irreversible mass capacity, ie 266 mAh / g of irreversible capacity.
• the compound Li 9 MnO 6 has a total specific capacity of 1125 mAh / g.
• Table 4b indicates that the capacity of element I is 128 mAh per gram of positive and negative active substances while that of element R is only 115 mAh / g, a mass capacity gain of approximately 10 mA. %.
• the capabilities of the positive and negative electrodes of the reference element R are shown schematically in FIG.
• the positive electrode containing 1 gram of positive material has a total capacity of 165 mAh and an irreversible capacity of 15 mAh (left rectangle).
• the negative electrode has an identical total capacity of 165 mAh and an irreversible capacity of 35 mAh (right rectangle).
• the capacities of the positive and negative electrodes of the element I according to the invention are shown schematically in FIG.
• the irreversible capacity provided by LiFeP0 4 is 14.7 mAh, that provided by LigMnO6 is 20.3 mAh, a total irreversible capacity of 35 mAh.
• the total capacity of the positive electrode is increased to 185 mAh due to the increase in the capacity provided by Li9Mn0 6 (left rectangle).
• the irreversible capacitance of the negative electrode has increased from 35 mAh to 39 mAh, due to the increase in the total capacitance of the positive electrode and the assumption that the total capacitance of the negative electrode is kept at the same value as that of the positive electrode.
• the capacity of the negative electrode is shown on the right rectangle of FIG.
• FIG. 1b shows that the addition of only 2% of Li9MnO 6 compound has made it possible to very significantly reduce the difference between the irreversible capacity of the positive electrode and the irreversible capacity of the negative electrode.
• Table 4b above shows that this difference reduction is accompanied by an increase in the mass reversible capacity of the element (expressed per gram of positive and negative active materials) since the mass reversible capacity of the element I is increased by 10% compared to that of the element R. Therefore, the principle of the invention is well verified.

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• 2017
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