FR3040823B1 - LITHIUM ALLOY CELL COMPRISING SOLID ELECTROLYTE FOR BATTERY MANUFACTURE - Google Patents

Abstract

The invention relates to a lithium alloy cell comprising a solid electrolyte consisting of a lithium salt of formula LiX in which X represents a halogen optionally mixed with a ceramic additive, the anode consisting of a lithium alloy of formula LiM , in which M represents a metal, associated with the electrolyte and the cathode consisting of metal disulfide associated with the electrolyte. In this cell, the electrolyte has a particle size of less than 160 μm, the lithium alloy and the metal disulfide have a particle size of less than 250 μm, said cell being capable of providing a constant voltage of the order of 1.5 V for at least ten days in a volume of a few cubic centimeters at an operating temperature between 25 and 350 ° C. Application to the manufacture of batteries.

Description

The technical field of the present invention is that of lithium alloy cells consisting of cells comprising a solid electrolyte for making batteries.

Today, there are batteries that operate either below 180 ° C or at temperatures above 350 ° C. The need for a technology working from ambient to 350 ° C is not covered and no battery exists for this temperature range. Current needs in different fields (geothermal, oil, ...) are becoming more and more pressing for this temperature range

Much research has been done to achieve this type of batteries.

Thus, to solve this problem two recent publications have proposed the use of sodium batteries incorporating a low temperature fuse electrolyte. The document US2015 / 0086826 for example proposes a battery operating at a temperature of 160 to 220 ° C and the document US2015 / 0147619 also a sodium battery operating at a temperature of 100 to 200 ° C. However, the risks associated with the use of a sodium compound are neither mentioned nor resolved.

In a document published by CERAMETEC, the characteristics of high temperature batteries were mentioned while considering a Li or LiBr solid electrolyte battery operating at a temperature between room temperature and 550 ° C. However, no characteristic is given on the constituents of this battery, in particular no electrochemical curve. In this document, there is provided a rechargeable battery whose electrolyte consists of LiI + Al2O3, the LiAl anode and the electrolyte and the FeS or FeS2 cathode and the electrolyte. However, it is indicated that this system has a high operating temperature without further specification.

The applicant has undertaken research to develop a cell operating at temperatures below 350 ° C in order to avoid the use of a sodium derivative and to carry out an in-depth study of the batteries. lithium despite the known obstacle of high operating temperature. This research led to the design of a lithium alloy cell whose characteristics of its components are carefully selected.

The object of the present invention is to provide a lithium alloy cell endowed with a discharge capacity spread over a very long period of time while operating at low temperature for making batteries. The subject of the invention is therefore a lithium alloy cell comprising a solid electrolyte consisting of a lithium salt of formula LiX in which X represents a halogen optionally mixed with a ceramic additive, the anode consisting of a lithium alloy of formula LiM, in which M represents a metal, associated with the electrolyte and the cathode constituted by metal disulfide associated with the electrolyte, characterized in that the electrolyte has a particle size of less than 160 μm, the lithium alloy and the metal disulphide has a particle size of less than 250 μm, said cell being capable of supplying a constant voltage of the order of 1.5 V for at least ten days in a volume of a few cubic centimeters at an operating temperature of between 25 and and 350 ° C.

According to a characteristic of the invention, the anode comprises from 30 to 100% by weight of lithium alloy and the cathode from 30 to 100% by mass of metal disulfide.

According to another characteristic of the invention, the lithium alloy is represented by LiM 'with M' = A1, B, or Si and the metal disulfide by M "S2 with M" = Fe, Co, Ni or Ti.

According to yet another characteristic of the invention, the ceramic additive of the electrolyte is represented by MgO, Al2O3fS1O2, Y2O3 or CaO.

Advantageously, a cell has a voltage of 1.5 volts.

A first advantage of the present invention lies in the fact that the modification of the particle size of the components of the cell allows commercial use thereof.

Another advantage of the invention lies in the very long discharge time, greater than 10 days, in a volume of a few cubic centimeters, at an operating temperature of between 25 and 350 ° C.

Yet another advantage of the present invention is that the electrolyte of the cell does not undergo any fusion and retains its physical integrity.

Yet another advantage of the present invention lies in the production of a battery incorporating one or more cells according to the invention. Other features, advantages and details of the invention will be better understood on reading the additional description which will follow of embodiments given by way of example in relation to drawings in which FIGS. 1 to 10 illustrate curves. discharge at different temperatures.

The applicant was interested in lithium alloy cells to overcome the obstacle of the high operating temperature known to those skilled in the art and to manufacture a battery usable in the industry. After research on particle size, the applicant realized that by changing in a particular way the particle size of the components of this cell could lower the operating temperature.

The modification of the particle size allowed to reduce the thickness of the components of the cell causing an increase in the ionic activity of the electrolyte and thus allow the decrease of the operating temperature.

The proposed solution with a new solid electrolyte provides a cell delivering energy for several days when the operating temperature is between room temperature and 350 ° C. At present, the requirements for deep drilling for example are distinguished from earlier uses by lower voltages, 2.5 to 4 V for example, but over much longer periods, for example 10 to 20 days, with a temperature operating temperature below 300 ° C. It is to these difficulties that the applicant provides a solution with the cell according to the invention by proposing a cell that can be used during deep drilling, for example by limiting the self-discharge of the cell while ensuring sufficient ionic conductivity and low operating temperature.

The cell according to the invention, while implementing products known in this technical sector, makes it possible to achieve these performances, namely an operating temperature that does not lead to the melting of the electrolyte, a lower voltage, an very long operating time, while being rechargeable if necessary.

The realization of the cell is carried out as follows.

Preparation of the solid electrolyte

The lithium salt LiX (X = F, Cl, Br, I) is dried at a temperature of the order of 125 to 200 ° C. In the case where the lithium salt is combined with a ceramic additive, it is mixed after grinding and sieving in a conventional manner and is carried out at a temperature above the melting point of the lithium salt. Then grinding and sieving is carried out so as to select a particle size of less than 160 μm.

Preparation of the negative electrode (anode)

Mechanical mixing of the LiM (M = Al, Si or B) having a particle size of less than 250 μm and the electrolyte obtained above is carried out.

Preparation of the positive electrode (cathode)

A mechanical mixture of 100 g of metal disulphide, the particle size of which is less than 250 to 250 μm (iron, cobalt, nickel or titanium) and the electrolyte obtained above is made.

The compositions thus obtained are used to manufacture various powder compression cells.

A cell assembly consisting of a 1 gram disc of the material of the negative electrode, 1.65 gr of electrolyte and 2.40 gr of cathode is manufactured. We obtain a set of cells whose total thickness is 1.53 mm and a diameter ranging from 26 mm to 36 mm. To perform the discharge tests one can use a single cell or a set of cells.

The discharge protocol is as follows. The cell is placed between two voltage collectors in a neutral environment at 150 ° C. The collectors are the voltage outputs that are connected to an SP-240 galvanometer from Biologie. The cell is then discharged at a current of -0.25 mA without time limit with a relaxation of one minute every 30 minutes applied to measure the impedance of this cell.

Figure 1 illustrates the discharge test of the cell operating at 150 ° C and shows a constant voltage V of about 1.5 V for more than 10 days for a current of -0.25 mA.

FIG. 2 illustrates the capacity in mA.h of the cell always at the operating temperature of 150 ° C. as a function of the voltage V. It can be seen that this voltage remains constant at about 1.5 V, the capacitance is 23 mA. .h and the cell still works after 10 days.

An identical cell is available at about 250 ° C. and the same measurements are taken.

Figure 3 illustrates the discharge test of the cell operating at 250 ° C and shows a constant voltage V of about 1.6 V for more than 10 days for a current of -0.55 mA.

FIG. 4 illustrates the capacity in mA.h of the cell always at the operating temperature of 250 ° C. as a function of the voltage V. It can be seen that this voltage remains constant at about 1.6 V, the capacitance is 130 mA .h and the cell still works after 10 days.

A stack is made of two cells with 9 packets in parallel. The battery is placed in an oven at the desired temperature (250 ° C) the time of discharge (greater than 10 days). The + and - poles of the battery are connected to a BCS-815 galvanometer from Biologie. The battery is discharged at a current of -0.9 mA with no time limit and relaxation is done for one minute every 30 minutes to take the impedance of the system.

FIG. 5 illustrates the voltage of the battery operating at 150 ° C. for a current of -0.9 mA and this voltage stabilizes at 3 V for more than 10 days.

Figure 6 illustrates the voltage of the battery operating at 150 ° C under the same conditions. It is found that the capacity measured in mA.h is 210 mA.h 10 days after and the battery still works.

A stack comprising two cells in series with 11 packets in parallel is manufactured. The battery is fully assembled and welded in a glove box under a neutral atmosphere and is placed in an oven at the desired temperature (150 ° C). The aforementioned galvanometer is used, but the battery is discharged at a current of -2.25 mA with no time limit and with a relaxation of one minute every 30 minutes to measure the impedance.

Figure 7 illustrates the voltage of the battery operating at 150 ° C for a current of -2.25 mA. The curve shows that voltage V stabilizes at about 2.8 V for more than 10 days.

Figure 8 shows the voltage under the same conditions. (Battery operating at 150 ° C) It is found that the capacity measured in mA.h is 500 mA.h 10 days after and the battery still works.

A stack is made comprising two cells in series with 13 packets in parallel. The battery is placed in an oven at the desired temperature (250 ° C). The galvanometer mentioned above is used, but the battery is discharged at a current of -1.72 mA with no time limit and with a relaxation of one minute every 30 minutes to take the impedance of the system.

Figure 9 illustrates the voltage of the battery operating at 250 ° C for a current of -1.72 mA. The curve shows that voltage V stabilizes at about 2.8 V for more than 19 days.

Figure 10 shows the voltage of the battery operating at 250 ° C under the same conditions. It is found that the capacity measured in mA.h is 650 mA.h 19 days after and the battery still works. Other tests were carried out at operating temperatures below 100 ° C and similar performance was demonstrated as indicated above.

The results provided above show all the interest of the cell according to the invention. Thus, for the first time, it is possible to manufacture a battery meeting the specificities required in the field of deep drilling by providing satisfactory operation for a very long time. By increasing the number of packets, we also see that the performance of the stack improves considerably. Thus, the invention opens a new way in the use of all-solid lithium alloy cells and cells without fusion of the electrolyte at operating temperatures between 25 and 350 ° C.

Claims (5)

A lithium alloy cell comprising a solid electrolyte consisting of a lithium salt of formula LiX in which X represents a halogen optionally mixed with a ceramic additive, the anode consisting of a lithium alloy of formula LiM ', in which M 'represents a metal, associated with the electrolyte and the cathode constituted by M "S2 metal disulfide associated with the electrolyte, characterized in that the electrolyte has a particle size of less than 160 μm, the lithium alloy and the metal disulphide having a particle size less than 250 μm, said cell being capable of supplying a constant voltage of the order of 1.5 V for at least ten days in a volume of a few cubic centimeters at an operating temperature of between 25 and 350 "C. 2. Lithium alloy cell according to claim 1, characterized in that the ceramic additive of the electrolyte is represented by MgO, Al2O3, SiO2, Ï2C3 or CaO. 3. Lithium alloy cell according to claim 1 or 2, characterized in that in the lithium alloy LiM 'the metal M' is represented by Al, B or Si and in the metal disulfide M "Sj the metal M" is represented by Fe, Co, Ni or Ti. 4. Use of the lithium alloy cell according to one of the preceding claims for the manufacture of cells comprising 2 cells with 11 packets in parallel. 5. Use of the lithium alloy cell according to one of claims 1 to 3 for the manufacture of cells comprising 2 cells with 13 packets in parallel.