SOLID LITHIUM CELL, BATTERY COMPRISING SAID CELLS AND MANUFACTURING PROCESS FOR MANUFACTURING SAID BATTERY

Abstract

A solid lithium cell is formed by stacking an etched copper substrate, a layer of graphite, an electrolyte, and a layer of nickel, manganese, and cobalt oxides. The electrolyte is in contact with the graphite layer and the layer of nickel, manganese, and cobalt oxides. The copper substrate forms the anode of the cell. The layer of nickel, manganese and cobalt oxides forms the cathode of the cell. The electrolyte is a solid lithium-based electrolyte. The graphite layer has a first solid electrolyte interface produced during a pre-lithiation with a liquid lithium-based electrolyte and a second solid electrolyte interface produced during a pre-lithiation with the solid lithium-based electrolyte.

Claims

1-10. (canceled)

11. A solid lithium cell formed by stacking of an etched copper substrate, of a graphite layer, of an electrolyte, and of a layer of nickel, manganese and cobalt oxides, the electrolyte being in contact with the graphite layer and the layer of nickel, manganese and cobalt oxides, the copper substrate forming the anode of the cell, and the layer of nickel, manganese and cobalt oxides forming the cathode of the cell, in which the electrolyte is a solid lithium-based electrolyte and the graphite layer exhibits a first solid electrolyte interface produced during a prelithiation with a liquid lithium-based electrolyte and a second solid electrolyte interface produced during a prelithiation with the solid lithium-based electrolyte.

12. The solid lithium cell as claimed in claim 11, in which the solid lithium-based electrolyte is a porous membrane electrolyte made of poly(vinylidene fluoride)-poly(hexafluoropropylene) improved with lithium bis(trifluoromethylsulfonyl)imide.

13. The solid lithium cell as claimed in claim 11, in which the copper substrate and the graphite layer are rendered integral mechanically.

14. The solid lithium cell as claimed in claim 11, in which the layer of nickel, manganese and cobalt oxides is of formula LiNi.sub.xMn.sub.yCo.sub.zO.sub.2, where x, y, and z represent atomic percentage values and x is of between 0.3 and 0.8, y is of between 0.1 and 0.3, and z is of between 0.1 and 0.3.

15. A solid lithium battery comprising at least two of the solid lithium cells as claimed in claim 11, the cells being fitted in parallel.

16. A manufacturing process for manufacturing the solid lithium battery as claimed in claim 15, comprising the following stages: carrying out a wet etching of a copper substrate in order to obtain a relief pattern, placing a graphite layer on the etched copper substrate, assembling a first cell comprising the graphite layer on the etched copper substrate, a layer of nickel, manganese and cobalt oxides and a liquid lithium-based electrolyte in contact both with the graphite layer and with the layer of nickel, manganese and cobalt oxides, carrying out a prelithiation of the graphite layer of the first cell, withdrawing, from the first cell, the prelithiated graphite layer fixed to the etched copper substrate, assembling a second cell comprising the prelithiated graphite layer on the etched copper substrate, a layer of nickel, manganese and cobalt oxides and a solid lithium-based electrolyte in contact with the prelithiated graphite layer and with the layer of nickel, manganese and cobalt oxides, and assembling a solid lithium battery comprising at least two second cells in parallel.

17. The manufacturing process for manufacturing a solid lithium battery as claimed in claim 16, in which the prelithiation of the first cell is carried out with a discharge cycle, in a constant current and constant voltage mode at 0.05 C at ambient temperature and a voltage window of OCV-10 mV.

18. The manufacturing process for manufacturing a solid lithium battery as claimed in claim 16, in which the etching of the copper substrate comprises the following stages: applying a solution of FeCl.sub.3, HCl and H.sub.2O for 30 seconds, washing the copper substrate with an ammonium bicarbonate NH.sub.4HCO.sub.3 solution and then with water, and drying the copper substrate over a hot plate at 80° C.

19. The manufacturing process for manufacturing a solid lithium battery as claimed in claim 16, in which the solid lithium-based electrolyte is a dry polymer electrolyte.

20. The manufacturing process for manufacturing a solid lithium battery as claimed in claim 19, in which the solid lithium-based electrolyte is a porous membrane electrolyte made of poly(vinylidene fluoride)-poly(hexafluoropropylene) improved with lithium bis(trifluoromethylsulfonyl)imide.

Description

[0034] A better understanding of the present invention will be obtained on studying the detailed description of a number of embodiments considered by way of entirely nonlimiting examples and illustrated by the appended drawings, in which:

[0035] FIG. 1 shows the main stages of a manufacturing process according to the invention, and

[0036] FIG. 2 shows the main parts of a double-layer SEI battery cell, according to the invention.

[0037] In order to solve the problem of the flaking of the graphite layer on the copper substrate, a chemical etching of the copper substrate is carried out before the formation of the graphite layer. This etching is designed to form a relief pattern, in particular via recesses at the surface of the copper substrate. During the coating of the graphite layer, the recesses are filled with graphite which makes possible the attachment of the graphite layer by mutual mechanical locking. In other words, the total surface area over which the adhesive forces can develop is increased.

[0038] The etching is carried out in the form of wet etching with a solution of FeCl.sub.3, HCl and H.sub.2O. The etching solution is applied for 30 seconds to the copper substrate. The copper substrate is subsequently washed consecutively with an ammonium bicarbonate NH.sub.4HCO.sub.3 solution and with water. The copper substrate is subsequently dried over a hot plate at 80° C.

[0039] In order to solve the SEI problem, a double-layer SEI was designed.

[0040] During a first stage, a stack of layers comprising a layer of nickel, manganese and cobalt (NMC) oxides, a graphite layer and a liquid lithium-based electrolyte between them is formed. The layer of nickel, manganese and cobalt oxides is of formula LiNi.sub.xMn.sub.yCo.sub.zO.sub.2, where x, y, and z represent atomic percentage values and x is of between 0.3 and 0.8, y is of between 0.1 and 0.3, and z is of between 0.1 and 0.3.

[0041] After the prelithiation of the graphite electrode, a first SEI is formed. The cell is subsequently cut in order to withdraw the liquid electrolyte/graphite electrode SEI.

[0042] During a second stage, a second cell is constructed with the liquid electrolyte/graphite electrode SEI withdrawn from the first cell. The second cell comprises a structure similar to that of the first cell but with a polymer lithium-based electrolyte instead of a liquid lithium-based electrolyte. After the prelithiation of the graphite layer in the second cell, a second SEI is formed at the interface between the liquid electrolyte SEI and the solid polymer electrolyte.

[0043] The double-layer SEI obtained makes possible a transfer of ions with the electrolyte to and from the graphite which is stable.

[0044] The process for the manufacture of the solid lithium battery comprises the following stages.

[0045] During a first stage 1, a copper substrate undergoes wet etching with a solution of FeCl.sub.3, HCl and H.sub.2O (FeCl.sub.3: 0.5-1 g, 36% HCl: 3-5 ml, H.sub.2O: 12-15 ml).

[0046] During a second stage 2, a graphite layer is applied to the etched copper substrate.

[0047] During a third stage 3, a first cell is assembled, comprising the graphite layer on the etched copper substrate, an NMC layer and a liquid lithium-based electrolyte in contact both with the graphite layer and with the NMC layer.

[0048] During a fourth stage 4, a prelithiation of the graphite layer is carried out in the first cell with a discharge cycle, in a constant current and constant voltage (CCCV) mode at 0.05 C at ambient temperature and a voltage window of OCV-10 mV.

[0049] During a fifth stage 5, the cell is opened and the prelithiated graphite layer which is on the etched copper substrate is withdrawn.

[0050] During a sixth stage 6, a second cell is assembled, comprising the prelithiated graphite layer on the etched copper substrate, an NMC layer and a solid lithium-based electrolyte in contact with the prelithiated graphite layer and with the NMC layer. The solid lithium-based electrolyte is a dry polymer electrolyte, such as a porous membrane electrolyte made of poly(vinylidene fluoride)-poly(hexafluoropropylene) (PVDH-HFP) improved with lithium bis(trifluoromethylsulfonyl)imide (LiTFSI), also known under the name of PVDF-HFP LiTFSI. A second solid electrolyte interface layer is formed during a first charging.

[0051] During a seventh stage 7, a solid lithium battery is assembled, comprising at least two second cells in parallel.

[0052] FIG. 2 represents a second cell obtained by means of the manufacturing process. A second cell 10 comprises an NMC layer 11, a solid lithium-based electrolyte 12, a double-layer SEI 13, a graphite layer 14 and a copper substrate 15. The double-layer SEI 13 comprises a liquid electrolyte SEI 17 in contact with the graphite layer 14 and a solid electrolyte SEI 16 in contact with the solid lithium-based electrolyte 12. The NMC layer 11 forms the cathode of the second cell, while the prelithiated graphite forms the anode.