Method of manufacturing a solid-state lithium battery and a battery manufactured by the method

The propose method of manufacturing a solid-state lithium battery consists of preparing an anode coated with a solid-state electrolyte precursor and a cathode unit coated with solid-state electrolyte, both precursors containing a predetermined amount of a redundant water. The thus prepared anode unit and cathode unit are pressed to each other through their respective electrolyte precursor layers in a closed chamber at a predetermined elevated temperature and under a predetermined mechanical pressure, whereby an integral pre-final solid-state battery unit is formed. The manufacture of the battery is completed by inserting the prefinal product into a casing that leaves parts of the metal current collectors of the prefinal product exposed for use as a battery anode and a battery cathode.

FIELD OF THE INVENTION

The present invention relates to the field of electric energy storage devices and, more particularly, to lithium batteries, specifically to lithium batteries that contain solid electrolytes. More specifically, the invention relates to a solid-state lithium battery and a method of manufacturing thereof.

DESCRIPTION OF PRIOR ART

A solid-state battery is a battery that uses solid electrodes and a solid electrolyte rather than the liquid or polymer gel electrolytes found in lithium ion or polymer lithium batteries. Recent developments in the field of solid-state batteries have revealed several components such as solid-state electrolytes that made it possible to significantly improve, as compared to previous solid-state batteries, such properties as safety, energy density, durability, sensitivity, and stability.

One of the promising trends in the development of solid-state electrolytes for lithium batteries is described in pending U.S. patent application Ser. No. 17/239,593 filed by Ali Sadeghi, et al. on Apr. 24, 2021, and entitled “A Solid-State Electrolyte for Lithium-Ion Battery and a Method of Synthesis thereof”.

U.S. Pat. No. 10,446,845 issued on Oct. 15, 2019, to Goodenough, et al. discloses an electrochemical cell with a high voltage cathode. The aforementioned patent describes a rechargeable electrochemical cell that consists of an electrolyte side, a cathode side, and a polymer/plasticizer. The electrolyte side includes a solid glass electrolyte including an electrolyte mobile cation and electric dipoles, as well as an anode including a metal of the electrolyte mobile cation and contacting the solid glass electrolyte at an “anode/solid glass” electrolyte interface. The cathode side contains a cathode that includes a cathode active material into which a cathode guest cation is reversibly extracted/inserted. The cathode active material has a voltage versus lithium (Li) metal of between 3V and 15V. The polymer/plasticizer contacts the solid glass electrolyte at a solid glass “electrolyte: polymer/plasticizer” interface and the cathode at a “polymer/plasticizer: cathode” interface. As a result, the cathode guest cation is confined to the cathode side, and the electrolyte mobile cation is confined to the anode side during charge and discharge of the electrochemical cell.

Further improvement in the method of manufacturing a solid-state lithium battery is disclosed in the aforementioned pending U.S. patent application Ser. No. 17/239,593 filed by Ali Sadeghi, et al. on Apr. 24, 2021. The improved method is based on synthesizing a solid-state electrolyte of Li3HaIO formula for use in a lithium-ion battery. The method consists of uniformly mixing at least LiOH and LiHaI in a stoichiometric quantity, heating the prepared mixture to a melting temperature and causing a reaction of formula (2LiOH+LiHaI=Li3HaIO+H2O) between the at least LiOH and LiHaI in a process free of forming a perovskite structure and at a temperature, at which H2O that forms at the aforementioned reaction is converted into a bound form, whereby a reaction product is obtained. According to another modification of the method, prior to the stage of melting the mixture, a reinforcement mesh is immersed into the mixture, whereby after mixture is solidified, a solid-state electrolyte reinforced with the mixture embedded into its material is obtained.

SUMMARY OF THE INVENTION

The present invention relates to a method of manufacturing electrical energy-storing devices, in particular, to manufacturing solid-state lithium batteries, and to solid-state lithium batteries produced by the aforementioned method.

The propose method of manufacturing a solid-state lithium battery consists of an anode coated with a solid-state electrolyte precursor and a cathode unit coated with solid-state electrolyte, both precursors containing a predetermined amount of a redundant water. The thus prepared anode unit and cathode unit are pressed to each other through their respective electrolyte precursor layers in a closed chamber at a predetermined elevated temperature and under a predetermined mechanical pressure, whereby an integral pre-final solid-state battery unit is formed. The manufacture of the battery is completed by inserting the prefinal product into a casing that leaves parts of the metal current collectors of the prefinal product exposed for use as a battery anode and a battery cathode.

DETAILED DESCRIPTION OF THE INVENTION

According to the present invention, a method of manufacturing a lithium battery consists of three processes, two of which are carried out separately in parallel or in sequence for obtaining a precursor-coated anode unit and a precursor-coated cathode unit. The third process consists of assembling the obtained precursor-coated units to complete the manufacture of the target lithium battery.

The first, second, and third processes will be further described with reference to the accompanying drawings, whereFIG.1is a flowchart of a lithium-battery manufacturing method according to one aspect of the invention, andFIG.3is a lithium-battery manufacturing method according to a second aspect of the invention, both methods being identical and differs only by methods of supply of reagents to the surfaces of the anode unit and cathode unit.

The method of manufacturing a solid-state lithium battery (hereinafter referred to as a “Li-battery”) consists of the following steps.

In a first process, which is shown inFIG.1in the form of sequential operations, the first step (Step1-1) consists of providing a metal current collector12, if necessary, one side of the metal current collector12is coated with a thin layer11of a conductive paste, and then a lithium-anode plate (Li-anode plate)10is placed onto the conductive paste layer11. The conductive paste layer11fulfills two functions: 1) provides the best electrical conduction between the Li-anode plate10and the metal current collector12; and 2) protects the contact surface of the Li-anode plate10from oxidation in subsequent battery manufacturing steps, i.e., Step (1-2), Step (1-3), and Step3. The conductive paste layer11has a thickness in the range of 10 micron to 40 micron. Then, the metal current collector together with the Li anode plate and the layer11is heated to a working temperature, whereby a heated anode unit14is obtained.

Here and hereinafter, the heating processes are shown by arrows. In Step1-1, the heating process is shown by arrows T1-1. The anode plate has a thickness in the range of tens of a micron to 0.5 mm. The current collector12is a metal plate or foil made of a material having high electric conductivity, such copper, aluminum, or stainless steel. The collector12has a thickness in the range of 20 microns to 100 microns. The anode plate10and the current collector12may have any suitable shape, e.g., a round shape with a diameter of conventional lithium batteries used in domestic appliances, instruments, TV remote controls, cameras, etc. Here and hereinafter, arrows designated by symbol F show transfer from sequential steps (F-1-1, F-1-2, and F1-3for the first process, F2-1, F2-2, and F2-3for the second process, and F3for the third process). The heating processes are shown by upwardly directed arrows and are designated as T1-1, T1-2, T1-3for the first process of the method, T2-1, T2-2, T2-3for the second process of the method, T3for the third process, and T4for the fourth process.

In Step1-2of the first process, the Li-anode plate10of the heated anode unit14is wetted with a (LiCl+H20) solution, whereby, as a result of a reaction of formulas (1)
2Li+2H2O=2LiOH+H2↑
2LiOH+LiCl=H2O ↑+Li3ClO,  (1)
a first solid-state electrolyte precursor18(here and hereinafter, the first SSE precursor) is formed on the heated anode unit.

The adsorption water (see formulas (1)) that is formed in the above reactions, is removed by thermal treatment at a temperature in the range of 90° C. to 130° C. Heat treatment at temperatures exceeding 130° C. leads to formation of non-uniform layers because of highly intensive emissions of gaseous hydrogen and water vapors (see reactions of formulas (1)).

However, some trace amounts of crystalline water still remain in the compounds (Li2(OH)Cl2, Li5(OH)2Cl3, Li2(OH)2Cl2, Li5(OH)3Cl2, Li3(OH)2Cl, Li4(OH)3Cl, which can be seen from the state diagram ofFIG.2. As can be seen from the same diagram ofFIG.2, these trace amounts of the crystalline water can be completely removed only at temperatures of 300° C. to 500° C. However, since the processes of the method of the invention are carried out at working temperatures of 90° C. to 130° C., they involve the formation of the aforementioned compounds through the entire thickness of the first SSE precursor18, and the content of these compounds varies in the thickness direction of the precursor18depending on the concentration of lithium. As has been found by the inventors herein, in the method of the invention the crystalline water plays a prevailing role in the conductivity of the first SSE precursor18.

According to the first aspect of the invention, wetting is carried out by dripping. In Step2-1, the drops are designated by reference numeral20. As mentioned above, the wetting process is accompanied by the formation of redundant water (the role of which was described above) and hydrogen-containing reaction products (see reactions (1)). Heating shown by arrows T2-1is continued. The heating time is within the range of 5 to 15 min. The aqueous (LiCl+H2O) solution may have different concentrations of LiCl up to or about 83 wt. %. The reaction that takes place on the lithium surface between the lithium and the solution also is accompanied by intensive emission of gaseous hydrogen and a redundant water vapors that do not participate in the reaction. The heating temperature on the lithium surface during the reaction is in range of 90° C. to 130° C.

One of the reaction products is Li3ClO. More specifically, L3ClO is formed as a result of the same reaction as one shown by formulas (1).

Removal of reaction products should be made under a pressure below the atmospheric and in the atmosphere of an inert gas, e.g., argon. Step1-3is removing extraneous and redundant H2O bonded products and H2-reaction products. Heating shown by arrows T3-1is continued. The main problem in conducting the aforementioned reaction is removal of free water and retaining it in the hydroxyl form, as well as removal of H2. Free water is left in a trace amount. However, the removal of H2at temperatures exceeding 130° C. may result in non-uniformity in the newly formed surface layer, i.e., the first SSE precursor18. In reality, the first SSE precursor18will also contain all compounds shown in the state diagram ofFIG.2. As a result, a precursor-covered lithium anode unit26is obtained. Heating is still maintained.

The following is a description of the second process of the Li-battery manufacturing method. The second process is manufacturing of a battery cathode unit. The process consists of Steps2-1,2-2, and2-3, which can be performed in parallel with or independently from the first process.

Step2-1is pressure forming of a cathode plate28from a compressed mixture of cathode-material powder and placing the obtained cathode plate28on a metal current collector30, whereby a cathode unit32is obtained. The obtained cathode unit32is heated to a temperature in the range of 90° C. to 130° C.

Although in the subsequent description the active component of the compressed mixture of cathode-material powder is exemplified by MnO2, other oxides such as LiMn2O4, LiCoO2, LiFePO4, Li4Ti5O12, LiNi0.5Mn1.5O4, or the like also can be used, e.g., in the form of oxide particles bounded with carbon particles. for improving conductivity of the cathode plate.

The heating process is shown by arrows T2-1. The powder mixture is a mixture of, e.g., a finely dispersed MnO2powder in an amount, e.g., up to 92 wt %, with a polyfluorotetraethylene (PTFE), e.g., in an amount of 5 wt. %, and finely dispersed carbon powder, e.g., in an amount of 3 wt %. Although the above composition and component ration of the powder mixture are those normally used in the manufacture of standard batteries, they are given only as examples, and a lot of other compositions and component ratios can be used for the purposes of the present invention.

The cathode plate28is formed from the powder under pressure, e.g., in the range up to 3000 kg/cm2, whereby the cathode plate, which normally has a thickness of 0.5 mm to 3 mm is obtained. The diameter of the cathode plate28is the same as the diameter of the lithium anode plate16. The cathode plate28is formed on the current collector plate30with a tight electrical contact, which is enhanced in the aforementioned pressure-forming operation.

In the next Step2-2, the obtained cathode unit32is maintained under an elevated temperature in the range of 90° C. to 130° C. and is subjected to wetting of the cathode plate28with a (LiCl+H20) solution, whereby a second SSE precursor, e.g., a precursor34is formed. A specific heating time at Step2-2, as well as at other heating processes, depends on many production parameters such as thickness of the precursors to be formed, concentration of solutions, etc., but, in general, the time lasts from 5 min to 15 min. The second SSE precursor34has a thickness in the range, e.g., of 20 microns to 150 microns. This range is given as an example, and the precursor34may be thicker than 150 microns.

The wetting operation is dripping, where in Step T2-2drops are designated by reference numeral38. The heating process in Step2-3is carried out in a close space of a chamber Ch1. The heating is performed under low pressure of 50 to 250 mTorr until complete removal of reaction emission products generated in the chamber Ch1in Step2-3is achieved. The heating is continued until the content of moisture in the precursor34is reduced to a predetermined level at which a certain amount of free water remains. This is achieved by controlling the time and pressure at Step F2-3in the chamber Ch1). The parameters of the processes that occur in the chamber Ch1are given as examples. Then, thus obtained a precursor-covered cathode unit40is transferred to Step3(cathode-anode assembling operation

It is assumed, that Step F2-3occurs simultaneously or after Step F1-3(transfer of the precursor-coated anode unit26to assembling Step3) provided that the anode unit26remains in a heated state.

Upon completion of the first and second processes according to the first aspect of the invention, a third Li-battery manufacturing process begins. The third process consists essentially of two steps, i.e., Step3and Step4, which are conducted in a chamber Ch2. The chamber Ch2is provided with devices that allow to maintain the interior of the chamber under a predetermined pressure and an elevated temperature. The chamber Ch2is equipped with a mechanical press (which is not shown inFIG.1but the presence of which is shown by arrow44). The mechanical pressure developed in the chamber Ch2may reach a value of 1000 kg/cm2.

In Step3, the precursor-covered lithium anode unit26, obtained in the first process of the method is flipped over by 180° and placed onto the precursor-covered cathode unit40. This action is shown by arrows F1-3and F2-3. Thus, the surface of the precursor-covered lithium anode unit26is placed into contact with the wet surface of the second SSE precursor34of the precursor-covered cathode unit40. During assembling, the heating shown by arrows T3is continued. Arrows P1, P2, P3and P4show approaching of the precursor-coated Li-anode unit26toward the precursor-coated cathode unit40.

As a result, a pre-final solid-state battery unit42is obtained (FIG.1). The transfer from Step F1-3to Step3is shown by arrow F3. Arrow44shows application of the lithium unit26onto the cathode unit40under a high mechanical pressure, e.g., of about 1000 kg/cm2. However, a caution is needed to limit the pressure to a value at which the lithium tablet is not deformed or destroyed.

The extraneous reaction products such as water, residual solution, etc., are removed from the chamber Ch2. During assembling, temperature of the process is maintained in the range of 90° C. to 130° C., and an interior pressure in the chamber Ch2is reduced below the atmospheric to a level, e.g., below 100 mTorr. After interaction of the first SSE precursor18with the second SSE precursor34, an integral solid-state electrolyte45is formed.

Upon completion of the assembling, extraneous gaseous products are removed from the surfaces of the pre-final solid-state battery unit42. The latter is still maintained in a heated state for protecting its surfaces from interaction with atmospheric moisture. Alternatively, the unit42is retained in the atmosphere of an inert gas and under a pressure below the atmospheric. After release of the pressure, the pre-final solid-state battery unit42is still maintained in the chamber Ch2for a certain time under low internal pressure of about 100 mTorr and under the elevated temperature of, e.g., 90° C. Following this, the pressure is increased to the atmospheric and the temperature is reduced to room temperature.

The method of the invention according to the second aspect will now be described with reference toFIG.3. In general, the method of the second aspect of the invention is similar to the method described with reference toFIGS.1and2. Therefore, the steps, components, and operations of the second modification of the method are designated with the same reference numerals and symbols, which are identical to those of the first modification, but with an addition of a prime, i.e., the first step is designated as Step (1-1)′, the Li-anode plate is designated by reference numeral10′, the collector plate is designated by reference numeral12′, etc. Thus, the second solid SSE precursor will be designated by reference numeral18′ and the integral solid-state electrolyte by reference numeral45′. In Step (1-3)“, reference numeral CHM2adesignates a closed chamber for drying the precursor26” at a predetermined pressure and temperature to a predetermined content of water in the precursor26′.

Upon completion of the assembling, extraneous gaseous products are removed from the surfaces of a pre-final solid-state battery unit42′.

The main distinction of the method according to the second aspect from the first one resides in the operation of wetting of the Li-anode plate10′ of the heated anode unit14′ with a (LiCl+H2O) solution for the formation of the first SSE precursor18′ on the surface of the lithium anode plate10′. According to the second aspect of the invention, wetting is carried out by placing the unit into the solution medium, which is delivered in the form of a mist designated by reference numeral20′. Formation of the mist20′ and wetting of the of the Li-anode plate10′ are performed in a confined space of the closed chamber ChM1afor wetting of the anode plate10′ in Step (1-2)′, and in a confined space of the closed chamber ChM1bfor wetting of the cathode plate28′ in Step (2-2)′. The closed chambers are needed for maintaining the wetting process at predetermined temperature and pressure. Heating during assembling under mechanical pressure in a chamber Ch2is accompanied by the formation of an integral solid-state electrolyte45′.

Upon completion of the assembling, extraneous gaseous products are removed from the surfaces of the pre-final solid-state battery unit42′. The latter is still maintained in a heated state for protecting the surfaces of semi-product from interaction with atmospheric moisture. Alternatively, the pre-final solid-state battery unit42′ is retained in the atmosphere of inert gas.

FIG.4shows a sequence of battery manufacturing operations in accordance with a modified version of the first process, which is shown inFIG.1. According to this aspect of the invention, the units, and steps, which are identical to those shown inFIG.1in connection with the previous first process, are designated with the same reference numeral and symbols but with an addition of two primes. For example, Step (1-1) is designated as Step (1-1)“, Step (1-2) is designated as Step (1-2)”, etc. However, the method of the modified version ofFIG.4differs from one shown inFIG.1by the omissions of Steps (2-2) and (2-3). This means that the cathode-collector unit32″ is transferred directly to Step3″. However, the unit32″ is formed under different temperature-time conditions. More specifically, for the formation of the integral solid-state electrolyte45″ in subsequent Step4″ with both layers combined into an integral structure, the heating time of T(2-1)″ process is extended by about 15-25% as compared to the time of T(2-1) of the previous battery manufacturing process. In order not to violate the structure in the formed layers, the heating temperature should be in the range of 90° C. to 130° C., and the time of the process is selected depending on such a parameter as a desirable thickness of the integral solid-state electrolyte45″ obtained in Step4″.

In order to provide reliable contact between the surfaces of cathode-collector unit32″ and the first SSE precursor18″ of the heated anode unit”14″, the surface of the first SSE precursor18″ is polished, e.g., with a rotary polishing tool21″.

As mentioned above, upon completion of the assembling a pre-final solid-state battery unit42″ (as well as pre-final solid-state battery units42and42′), extraneous gaseous products are removed from the surfaces of the pre-final solid-state battery unit42″ (FIG.4). The latter is still maintained in a heated state for protecting the surfaces of the pre-final solid-state battery unit42″ from interaction with atmospheric moisture. Next, the pre-final solid-state battery unit is transferred to the battery completion operation.

FIG.5is a vertical sectional view of a solid-state lithium battery50produced by the method of the present invention in accordance with the first, second, and third aspects of invention. The solid-state lithium battery50consists of the pre-final solid-state battery unit42(42′ and42″), which is inserted into a cup-shaped casing52that has a current-conducting bottom52aand electrically isolated or non-conductive side wall52b. The current collector12of the anode unit26(FIG.1) is coated with a metal spacer plate54. The cup-shaped casing52with the inserted pre-final solid-state battery unit42is covered with a cup-shaped external casing56made of an electrically conductive material, which is fitted onto the non-conductive side wall52b, e.g., with a press fit, and a metallic Belleville spring58is placed between the bottom56aof the cup-shaped external casing56and the upper surface54aof the metal spacer plate54. The current-conducting bottom52ais maintained in electrical contact with the metal electrical current collector30(FIGS.1and5). The spring58is used for maintaining a reliable contact between the current conducting parts of the battery. The lithium battery50of the present invention is shown as a coin-type battery only as an example, but in any case, the final battery of the invention may have a shape and overall dimensions of any standard battery. For example, the batteries of the invention may have dimensions specified by the International Electrotechnical Commission (IEC) and American National Standards Institute (ANSI).

The invention was described and illustrated with reference to specific drawings. It is understood, however, that the description and the illustrated modifications should not be construed as limiting the scope of the invention and that any changes are possible provided that do not depart from the scope of the attached claims. For example, the use of the metal spacer is optional and the spring58may be in contact directly with the current collector12of the anode unit26. The method is applicable to manufacturing solid-state cathodes of any types for use in non-chargeable or rechargeable batteries.