LKMNO cathode materials and method of production thereof

Abstract

LKMNO cathode materials based on a lithium-manganese spinel modified synergetically with potassium and nickel, and a method of production thereof are disclosed. The LKMNO cathode materials are characterised by a reversible gravimetric capacity in relation to lithium of at least 250 mAh/g after 80 operation cycles under a current load of 1 C, so that they are suitable for application in lithium-ion batteries with a high energy density.

Claims

1. A method of preparation of an LKMNO cathodic material Li.sub.1−xK.sub.xMn.sub.2−yNi.sub.yO.sub.4, where 0.01≤x≤0.15 and 0.01≤y≤0.2having a high energy density, wherein stoichiometric weighed amounts of lithium, potassium, manganese and nickel precursors are dissolved in a minimal amount of water ensuring a total dissolution of the substrates and simultaneously a protective atmosphere of an inert gas is used, and then, an ammonia solution having a concentration of 15-28% is introduced to the solution, until a pH value in the range of 8.5-11 is obtained, and next, after 30-60 min, the formed sol is subjected to polycondensation, aging and drying processes, until a xerogel is obtained, which is calcinated subsequently in the temperature range of 200-900° C.

2. The method according to claim 1, wherein a lithium precursor, lithium acetate, lithium nitrate (V), lithium hydroxide or lithium carbonate and hydrates thereof are used.

3. The method according to claim 1 wherein as a potassium precursor, potassium nitrate (V), potassium acetate, potassium hydroxide or potassium carbonate and hydrates thereof are used.

4. The method according to claim 1, wherein as a manganese precursor, manganese (II) acetate or manganese (II) nitrate (V) and hydrates thereof are used.

5. The method according to claim 1, wherein as a nickel precursor, nickel (II) acetate or nickel (II) nitrate (V) and hydrates thereof are used.

6. The method according to claim 1, wherein the steps up to the formation of the sol are carried out in the temperature range of 10-50° C. in an atmosphere of an inert gas selected from argon, nitrogen or helium.

7. The method according to claim 1, wherein the polycondensation, aging and drying processes are carried out in the atmosphere of air or synthetic air for 24-96 h at a temperature of 60-105° C.

8. The method according to claim 1, wherein the xerogel calcination process is carried out in two steps in the temperature range of 200-900° C. in the atmosphere of air or synthetic air.

9. An LKMNO cathodic material obtained by the method of claim 1.

Description

(1) The subject of the invention is described in more detail in the following embodiments.

Example 1 (Comparative)

(2) To obtain 10 g of the Li.sub.0.9K.sub.0.1Mn.sub.2O.sub.3.99S.sub.0.01 (LKMOS) spinel material, 4.9835 g of lithium acetate dihydrate, 0.5510 g of potassium nitrate(V), and 26.6166 g of manganese(II) acetate tetrahydrate were weighed. The weighed amounts of the substrates were transferred quantitatively to a reactor (atmosphere: Ar, 99.999%) and dissolved in approx. 50 ml of distilled water. After the dissolution of the substrates, 28.74 g of 25% ammonia solution earlier mixed with 188 μl of 20% ammonium sulphide solution, were added to the solution. After approx. 30 min, the formed sol was transferred to ceramic crucibles and dried at a temperature of 90° C. for 3-4 days. The obtained xerogel was calcined first at a temperature of 300° C. for 24 h (heating rate of 1° C./min), and the product of the first calcination was then calcined again at 650° C. for 6 h (heating rate of 5° C./min). Both calcinations were carried out in the atmosphere of air.

(3) The obtained spinel was characterised by a nanometric size of the crystallites (D.sub.XRD=32 nm). It was proved that an introduction of potassium and sulphur to the LMO spinel structure contributed into a stabilisation of the structure and elimination of an unfavourable phase transformation (characteristic for the stoichiometric LMO spinel) near room temperature, which was confirmed by differential scanning calorimetry (DSC) tests. The LKMOS material exhibited an electrical conductivity of 6.26.Math.10.sup.−4 S/cm at a temperature of 25° C., and an electrical conductivity activation energy E.sub.a=0.22 eV. Electrochemical tests showed that the obtained material is characterised by a gravimetric capacity in relation to lithium reaching 132 mAh/g—after 40 cycles of operation under a current load of 1 C.

Example 2 (Comparative)

(4) To obtain 10 g of the LiMn.sub.1.9Ni.sub.0.1O.sub.3.99S.sub.0.01 (LMNOS) spinel material, 5.6254 g of lithium acetate dihydrate, 25.6776 g of manganese(II) acetate tetrahydrate, and 1.3722 g of nickel(II) acetate tetrahydrate were weighed. The weighed amounts of the substrates were transferred quantitatively to a reactor (atmosphere: Ar, 99.999%) and dissolved in approx. 50 ml of distilled water. After the dissolution of the substrates, 29.37 g of 25% ammonia solution earlier mixed with 188 μl of 20% ammonium sulphide solution, were added to the solution. After approx. 30 min, the formed sol was transferred to ceramic crucibles and dried at a temperature of 90° C. for 3-4 days. The obtained xerogel was calcined first at a temperature of 300° C. for 24 h (heating rate of 1° C./min), and the product of the first calcination was then calcined again at 650° C. for 6 h (heating rate of 5° C./min). Both calcinations were carried out in the atmosphere of air.

(5) The obtained spinel was characterised by a nanometric size of the crystallites (D.sub.XRD=48 nm). It was proved that an introduction of nickel and sulphur to the LMO spinel structure contributed into a stabilisation of the structure and elimination of an unfavourable phase transformation (characteristic for the stoichiometric LMO spinel) near room temperature, which was confirmed by differential scanning calorimetry (DSC) tests. The LMNOS material exhibited an electrical conductivity of 5.974.Math.10.sup.−5 S/cm at a temperature of 25° C. and an electrical conductivity activation energy E.sub.a=0.32 eV. Electrochemical tests showed that the obtained material is characterised by a gravimetric capacity in relation to lithium reaching 129 mAh/g—after 40 cycles of operation under a current load of 1 C.

Example 3 (Comparative)

(6) To obtain 10 g of the Li.sub.0.99K.sub.0.01Mn.sub.1.9Ni.sub.0.1O.sub.3.99S.sub.0.01 (LKMNOS) spinel material, 5.5598 g of lithium acetate dihydrate, 0.0557 g of potassium nitrate(V), 25.6352 g of manganese(II) acetate tetrahydrate and 1.3699 g of nickel(II) acetate tetrahydrate were weighed. The weighed amounts of the substrates were transferred quantitatively to a reactor (atmosphere: Ar, 99.999%) and dissolved in approx. 50 ml of distilled water. After the dissolution of the substrates, 29.33 g of 25% ammonia solution previously mixed with 188 μl of 20% ammonium sulphide solution, were added to the solution. After approx. 30 min, the formed sol was transferred to ceramic crucibles and dried at a temperature of 90° C. for 3-4 days. The obtained xerogel was calcined first at a temperature of 300° C. for 24 h (heating rate of 1° C./min), and the product of the first calcination was then calcined again at 650° C. for 6 h (heating rate of 5° C./min). Both calcinations were carried out in the atmosphere of air.

(7) The obtained spinel was characterised by a nanometric size of the crystallites (D.sub.XRD=49 nm). It was proved that an introduction of potassium, nickel and sulphur to the LMO spinel structure contributed into a stabilisation of the structure and elimination of an unfavourable phase transformation (characteristic for the stoichiometric LMO spinel) near room temperature, which was confirmed by differential scanning calorimetry (DSC) tests. The LKMNOS material exhibited an electrical conductivity of 4.26.Math.10.sup.−5 S/cm at a temperature of 25° C. and an electrical conductivity activation energy E.sub.a=0.32 eV. Electrochemical tests showed that the obtained material is characterised by a gravimetric capacity in relation to lithium reaching 108 mAh/g—after 30 cycles of operation under a current load of 1 C.

Example 4

(8) To obtain 10 g of the Li.sub.0.99K.sub.0.01Mn.sub.1.9Ni.sub.0.1O.sub.4 (LKMNO) spinel material, 5.5635 g of lithium acetate dihydrate, 0.0557 g of potassium nitrate(V), 25.6533 g of manganese(II) acetate tetrahydrate, and 1.3709 g of nickel(II) acetate tetrahydrate were weighed. The weighed amounts of the substrates were transferred quantitatively to a reactor (atmosphere: Ar, 99.999%) and dissolved in approx. 50 ml of distilled water. After the dissolution of the substrates 29.33 g of 25% ammonia solution were added to the solution. After approx. 30 min, the formed sol was transferred to ceramic crucibles and dried at a temperature of 90° C. for 3-4 days. The obtained xerogel was calcined first at a temperature of 300° C. for 24 h (heating rate of 1° C./min), and the product of the first calcination was then calcined again at 650° C. for 6 h (heating rate of 5° C./min). Both calcinations were carried out in the atmosphere of air.

(9) The obtained spinel was characterised by a nanometric size of the crystallites (D.sub.XRD=52 nm). It was proved that an introduction of potassium and nickel to the LMO spinel structure contributed into a stabilisation of the structure and elimination of an unfavourable phase transformation (characteristic for the stoichiometric LMO spinel) near room temperature, which was confirmed by differential scanning calorimetry (DSC) tests. The LKMNO material exhibited an electrical conductivity of 1.2240 S/cm at a temperature of 25° C. and an electrical conductivity activation energy E.sub.a=0.35 eV. Electrochemical tests showed that the obtained material is characterised by a gravimetric capacity in relation to lithium of at least 250 mAh/g after 80 operation cycles under a current load of 1 C.

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