Active material for a positive electrode of a battery cell, positive electrode, and battery cell

Abstract

A positive active material for a positive electrode of a battery cell which includes a first component containing a compound of general formula: Li.sub.2-zNa.sub.zM.sup.1.sub.1-yM.sup.2.sub.yO.sub.3, where M.sup.1 and M.sup.2 are different from one another and stand for transition metal ions, 0<y<1, and 0z<2, with the condition that the compound is essentially free of manganese ions. Moreover, a positive electrode of a battery cell which includes the positive material, and a battery cell which includes at least one positive electrode, are also described.

Claims

1. A positive active material for a positive electrode of a battery cell, the positive active material including a first component containing a compound of general formula:
Li.sub.2-zNa.sub.zNi.sub.1-yCr.sub.yO.sub.3; wherein 0<y<1, and 0z2, with a condition that the compound is essentially free of manganese ions.

2. The positive active material as recited in claim 1, wherein the compound is Li.sub.2Ni.sub.0.5Cr.sub.0.5O.sub.3.

3. The positive active material as recited in claim 1, wherein 0.1z1.

4. The positive active material as recited in claim 1, wherein the positive active material includes a second component containing LiM.sup.3O.sub.2, M.sup.3 being a transition metal selected from the elements nickel (Ni), cobalt (Co), or manganese (Mn).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Specific embodiments of the present invention are explained in greater detail with reference to the drawings and the following description.

(2) FIG. 1 shows a schematic illustration of a battery cell.

(3) FIG. 2 shows a schematic illustration of a modification of the battery cell from FIG. 1.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

(4) A battery cell 2 is schematically illustrated in FIG. 1. Battery cell 2 includes a cell housing 3 having a prismatic design, in the present case a cuboidal design. In the present case, cell housing 3 has an electrically conductive design and is made of aluminum, for example. However, cell housing 3 may also be made of an electrically insulating material, for example plastic.

(5) Battery cell 2 includes a negative terminal 11 and a positive terminal 12. A voltage provided by battery cell 2 may be tapped via terminals 11, 12. In addition, battery cell 2 may also be charged via terminals 11, 12. Terminals 11, 12 are situated spaced apart from one another on a top surface of prismatic cell housing 3.

(6) An electrode winding which includes two electrodes, namely, a negative electrode 21 and a positive electrode 22, is situated within cell housing 3 of battery cell 2. Negative electrode 21 and positive electrode 22 each have a foil-like design, and are wound to form an electrode winding with a separator 18 situated in between. It is also possible to provide multiple electrode windings in cell housing 3. An electrode stack, for example, may also be provided instead of the electrode winding.

(7) Negative electrode 21 includes a negative active material 41 which has a foil-like design. Negative active material 41 contains silicon or a silicon-containing alloy as the base material.

(8) Negative electrode 21 also includes a current collector 31, which likewise has a foil-like design. Negative active material 41 and current collector 31 are placed flatly against one another and joined together. Current collector 31 of negative electrode 21 has an electrically conductive design and is made of a metal, for example copper. Current collector 31 of negative electrode 21 is electrically connected to negative terminal 11 of battery cell 2.

(9) In the present case, positive electrode 22 is a high-energy (HE) nickel-cobalt-manganese (NCM) electrode. Positive electrode 22 includes a positive active material (A) 42 which is present in particle form. Additives, in particular conductive carbon black and binder, are situated between the particles of positive active material (A) 42. Positive active material (A) 42 and the additives form a composite which has a foil-like design.

(10) Positive active material (A) 42 includes a first component (A1) containing Li.sub.2Ni.sub.0.5Mo.sub.0.5O.sub.3 or Li.sub.2Ni.sub.0.5Cr.sub.0.5O.sub.3, for example. First component (A1) may be additionally doped with sodium ions, so that a portion of the lithium ions is replaced by sodium ions.

(11) Positive active material (A) 42 also includes a second component (A2) containing an NCM compound, namely, LiM.sup.3O.sub.2. M.sup.3 is a transition metal selected in particular from nickel, cobalt, and manganese. Further components of positive active material (A) 42 are in particular PVDF binder, graphite, and carbon black.

(12) Positive electrode 22 also includes a current collector 32 which likewise has a foil-like design. The composite, made up of positive active material (A) 42 and the additives, and current collector 32 are placed flatly against one another and joined together. Current collector 32 of positive electrode 22 has an electrically conductive design and is made of a metal, for example aluminum. Current collector 32 of positive electrode 22 is electrically connected to positive terminal 12 of battery cell 2.

(13) Negative electrode 21 and positive electrode 22 are separated from one another by separator 18. Separator 18 likewise has a foil-like design. Separator 18 has an electronically insulating design, but is ionically conductive, i.e., is permeable for lithium ions.

(14) Cell housing 3 of battery cell 2 is filled with a liquid aprotic electrolyte composition 15 or with a polymer electrolyte. Electrolyte composition 15 surrounds negative electrode 21, positive electrode 22, and separator 18. Electrolyte composition 15 is also ionically conductive, and includes, for example, a mixture of at least one cyclic carbonate (for example, ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC)) and at least one linear carbonate (for example, dimethylene carbonate (DMC), diethyl carbonate (DEC), methylethyl carbonate (MEC)) as solvent, and a lithium salt (LiPF.sub.6, LiBF.sub.4, for example) as additive.

(15) FIG. 2 schematically illustrates a modification of battery cell 2 from FIG. 1. Modified battery cell 2 likewise includes a cell housing 3 which has a prismatic design, in the present case a cuboidal design. Battery cell 2 is very similar to battery cell 2 from FIG. 1. Therefore, in particular differences from battery cell 2 from FIG. 1 are discussed below.

(16) A coating 52 is applied to the particles of positive active material (A) 42. The particles of positive active material (A) 42 are enclosed by coating 52. Coating 52 thus envelops the particles of positive active material (A) 42.

(17) In the present case, coating 52 contains aluminum fluoride (AlF.sub.3). Coating 52 prevents or reduces contact of positive active material (A) 42 with electrolyte composition 15 contained in cell housing 3 of battery cell 2. Elutriation of transition metals from positive active material (A) 42 and migration of elutriated transition metals to negative electrode 21 of battery cell 2 are likewise prevented or reduced.

(18) Coating 52 may also contain carbon. A coating 52 of this type ensures homogeneous electronic contacting of positive electrode 22. Coating 52 may in particular have a multilayer design, and, for example, may contain a layer of aluminum fluoride (AlF.sub.3) and a layer of carbon.

(19) The present invention is not limited to the exemplary embodiments described here and the aspects highlighted therein. Rather, numerous modifications within the range set forth in the claims are possible which are within the scope of activities carried out by those skilled in the art.