Lithium primary battery

Abstract

This lithium primary battery comprises: a positive electrode; a negative electrode; and a non-aqueous electrolyte solution. The positive electrode contains LixMnO2 (0 ≤ x ≤ 0.05). The negative electrode includes an alloy containing lithium, magnesium, and potassium. The content of lithium in the alloy is 89 mass% or more, the content of magnesium in the alloy is 0.01-10 mass%, and the content of potassium in the alloy is 400 mass ppm or less.

Description

Lithium primary battery Cross-reference of related applications

[0001] This disclosure claims priority with respect to Japanese Patent Application No. 2024-232048, filed with the Japan Patent Office on 27 December 2024, and the entirety of the said patent application is incorporated herein by reference.

[0002] This disclosure relates to lithium primary batteries.

[0003] Lithium primary batteries are used as power sources for many electronic devices due to their high energy density and low self-discharge. Manganese dioxide is used as the positive electrode of a lithium primary battery. For the negative electrode, for example, sheet-like (foil-like) metallic lithium or lithium alloy is used.

[0004] Patent Document 1 discloses a high-temperature lithium battery in which graphite fluoride is used as the positive electrode, a lithium alloy is used as the negative electrode, and an ionic liquid is used as the electrolyte, and the lithium alloy is disclosed to be Li-Al alloy, Li-Mg alloy, Li-B alloy, Li-B-Mg alloy, or Li-Si alloy.

[0005] Japanese Patent Publication No. 2011-192627

[0006] In lithium primary batteries, the internal resistance may increase towards the end of the discharge phase, causing a decrease in the pulse discharge voltage.

[0007] One aspect of this disclosure comprises a positive electrode, a negative electrode, and a non-aqueous electrolyte, wherein the positive electrode is Li ｘ MnO ２ The present invention relates to a lithium primary battery, wherein the negative electrode comprises an alloy containing lithium, magnesium, and potassium, the lithium content in the alloy being 89% by mass or more, the magnesium content in the alloy being 0.01% by mass or more and 10% by mass or less, and the potassium content in the alloy being 400 ppm by mass or less.

[0008] According to the present disclosure, it is possible to suppress a decrease in the pulse discharge voltage due to an increase in the internal resistance at the end of discharge of a primary lithium battery. The novel features of the present invention are described in the appended claims, but the present invention will be better understood with reference to the following detailed description in conjunction with the drawings, with respect to both the structure and the content, as well as other objects and features of the present invention.

[0009] It is a front view of a part of a primary lithium battery according to an embodiment of the present disclosure in cross-section.

[0010] Hereinafter, embodiments of the present disclosure will be described with examples, but the present disclosure is not limited to the examples described below. In the following description, specific numerical values and materials may be exemplified, but other numerical values and materials may be applied as long as the effects of the present disclosure can be obtained. In this specification, the description "numerical value A to numerical value B" includes numerical value A and numerical value B and can be read as "numerical value A or more and numerical value B or less". In the following description, when the lower limit and the upper limit are exemplified for specific physical properties and conditions and the like, any combination of any of the exemplified lower limits and any of the exemplified upper limits can be made as long as the lower limit is not more than the upper limit. When a plurality of materials are exemplified, one of them may be selected and used alone, or two or more of them may be used in combination.

[0011] The primary lithium battery according to an embodiment of the present disclosure includes a positive electrode, a negative electrode, and a non-aqueous electrolyte. The positive electrode contains Li ｘ MnO ２ (0 ≤ x ≤ 0.05). The negative electrode contains an alloy containing lithium (Li), magnesium (Mg), and potassium (K) (hereinafter, also referred to as "lithium alloy"). The Li content in the lithium alloy is 89% by mass or more. The Mg content in the lithium alloy is 0.01% by mass or more and 10% by mass or less. The K content in the lithium alloy is 400 ppm by mass or less (0.04% by mass or less). In the primary lithium battery according to an embodiment of the present disclosure, the pulse discharge voltage at the end of discharge (particularly, the pulse discharge voltage in a low-temperature environment) can be increased. The pulse discharge voltage is the voltage during pulse discharge.

[0012] By adding Mg to the negative electrode containing Li, the strength of the negative electrode is improved, and a decrease in the discharge voltage due to an increase in the internal resistance associated with the occurrence of cracks and partial defects in the negative electrode at the end of discharge is suppressed. On the other hand, since Mg is likely to alloy with Li, the movement of Li is easily inhibited at the end of discharge, thereby increasing the internal resistance and making the pulse discharge voltage likely to decrease.

[0013] Therefore, the inventors of the present invention conducted intensive studies to suppress the voltage drop at the end of discharge as described above. As a result, it was newly found that by adding K to a negative electrode (lithium alloy) containing Li and Mg at a specific content rate, the inhibition of the movement of Li at the end of discharge is suppressed, and a significant decrease in the pulse discharge voltage due to an increase in the internal resistance at the end of discharge is suppressed.

[0014] The effect of improving the strength of the negative electrode by adding Mg and the effect of suppressing the inhibition of Li movement when Mg is contained by adding K act together to significantly suppress the voltage drop at the end of discharge. In addition, K also plays a role in improving the chemical stability of the film formed on the surface of the lithium alloy (negative electrode) and suppressing side reactions due to contact between the negative electrode and the non-aqueous electrolyte. Here, the end of discharge means, for example, a case where the depth of discharge (DOD: depth of discharge) is 80% or more. The depth of discharge is the ratio of the discharge capacity to the rated capacity.

[0015] However, if the Mg content rate in the lithium alloy is greater than 10% by mass, the proportion of Mg in the negative electrode increases, resulting in an increase in the negative electrode resistance and a possible voltage drop at the end of discharge. If the Mg content rate in the lithium alloy is less than 0.01% by mass, the effect of adding Mg becomes small, and the voltage may drop at the end of discharge.

[0016] If the K content rate in the lithium alloy is greater than 400 ppm by mass, the proportion of K in the negative electrode increases, resulting in an increase in the negative electrode resistance and a possible voltage drop at the end of discharge.

[0017] If the Li content rate in the lithium alloy is less than 89% by mass, the proportion of Li in the negative electrode decreases, resulting in a possible decrease in the discharge voltage.

[0018] (Lithium Alloy) A lithium alloy contains Li, Mg, and K. From the viewpoint of reducing internal resistance and ensuring capacity, the Li content in the lithium alloy is 89% by mass or more, may be 90% by mass or more, or may be 95% by mass or more. The Li content in the lithium alloy may be 99.98999% by mass or less. In a lithium alloy, elements other than Mg and K may be Li.

[0019] From the viewpoint of improving the strength of the negative electrode, the Mg content in the lithium alloy is 0.01% by mass or more, preferably 0.05% by mass or more, more preferably 0.1% by mass or 0.2% by mass or more, and may be 1% by mass or more. From the viewpoint of reducing the negative electrode resistance, the Mg content in the lithium alloy is 10% by mass or less, preferably 8% by mass or less, and more preferably 7% by mass or less or 4% by mass or less. The range of the Mg content in the lithium alloy may be, for example, 0.2% by mass or more and 7% by mass or less, or 0.2% by mass or more (or 1% by mass or more) and 4% by mass or less.

[0020] The lithium alloy contains 400 ppm by mass or less of potassium (K). Note that "containing K" in the lithium alloy means that the K content in the lithium alloy is above the detection limit of potassium in ICP emission spectroscopy (for example, 0.5 ppm by mass or more). From the viewpoint of suppressing the inhibition of Li migration by Mg addition, the K content in the lithium alloy may be 0.5 ppm by mass or more, 2 ppm by mass or more, 4 ppm by mass or more, 10 ppm by mass or more, or 40 ppm by mass or more. From the viewpoint of reducing negative electrode resistance, the K content in the lithium alloy is 400 ppm by mass or less, preferably 300 ppm by mass or less or 200 ppm by mass or less, and more preferably 100 ppm by mass or less or 50 ppm by mass or less. From the viewpoint of suppressing the decrease in pulse discharge voltage at the end of discharge, the range of K content in the lithium alloy may be, for example, 0.5 ppm or more and 400 ppm or less, 2 ppm or more and 400 ppm or less (or 200 ppm or less), or 4 ppm or more and 100 ppm or less. The molar ratio of K to Mg: K / Mg may be, for example, in the range of 0.000001 to 0.5.

[0021] Lithium alloys may contain other metallic elements besides Li, Mg, and K. Examples of other metallic elements include Al, Sn, Ni, Pb, In, Na, and Ca. The composition of lithium alloys can be determined by inductively coupled plasma (ICP) emission spectrometry or atomic absorption spectrometry (AAS).

[0022] Lithium alloys preferably further contain Al. Some of the Mg contained in the lithium alloy may be replaced with Al. In this case, the decrease in pulse discharge voltage at the end of discharge is further suppressed. The detailed reason for this is unknown, but it is presumed that the addition of Al makes it easier for Al and K to aggregate, and in the vicinity of these areas Li is less likely to alloy with Mg, thus further suppressing the inhibition of Li movement at the end of discharge when Mg is included. Furthermore, it is presumed that when Al is included along with Mg and K, a low-resistance coating is more easily and stably formed.

[0023] From the viewpoint of suppressing the decrease in pulse discharge voltage at the end of discharge, the Al content in the lithium alloy may be 0.01% by mass or more and 10% by mass or less, preferably 0.01% by mass or more (or 0.1% by mass or more) and 5% by mass or less, and more preferably 0.1% by mass or more and 2% by mass or less. From a similar viewpoint, the total content of Mg and Al in the lithium alloy is preferably 0.02% by mass or more and 10% by mass or less, and more preferably 0.2% by mass or more and 4% by mass or less. About half the mass of Mg (for example, in the range of 1 / 3 to 2 / 3) may be substituted with Al. The molar ratio of Al to Mg: Al / Mg may be, for example, in the range of 0.01 to 45.

[0024] (Additives for Non-Aqueous Electrolyte) The non-aqueous electrolyte preferably contains at least one additive selected from the group consisting of cyclic imide compounds, phthalate ester compounds, and isocyanate compounds. When the non-aqueous electrolyte contains the above additive, a composite film can be formed on the surface of the lithium alloy (negative electrode) containing components derived from the lithium alloy (Mg, K) and components derived from the additive. The formation of such a composite film reduces the negative electrode resistance (reaction resistance), further suppressing the increase in internal resistance at the end of discharge and the resulting voltage drop. In addition, the composite film has excellent chemical stability, and the lithium alloy is protected by the high-quality composite film.

[0025] The additive content in the non-aqueous electrolyte is, for example, 0.01% by mass or more and 5% by mass or less. The additive content in the non-aqueous electrolyte is the mass ratio (percentage) of the additive to the total non-aqueous electrolyte. For example, it is desirable that the additive content in the non-aqueous electrolyte be within the above range immediately after battery manufacturing (or during preparation of the non-aqueous electrolyte). In contrast, in batteries that have been in use for a certain period after manufacturing, some of the additive is consumed in film formation, and the additive content in the non-aqueous electrolyte may be smaller than the above range. In this case, even if the additive content in the non-aqueous electrolyte is small (for example, close to the detection limit), the above-mentioned effect of the additive can still be observed. The same applies to the content of various compounds, such as cyclic imide compounds, which will be discussed later.

[0026] (Cyclic imide compounds) Examples of cyclic imide compounds include cyclic diacylamine compounds. A cyclic imide compound only needs to have a diacylamine ring (hereinafter also referred to as an imide ring). Another ring (hereinafter also referred to as a second ring) may be fused to the imide ring. A cyclic imide compound may be contained in a non-aqueous electrolyte in the form of an imide, or in the form of an anion or salt. When a cyclic imide compound is contained in a non-aqueous electrolyte in the form of an imide, it may be contained in a form having a free NH group, or in the form of a tertiary amine.

[0027] Examples of the second ring include aromatic rings, saturated or unsaturated aliphatic rings, etc. The second ring may contain at least one heteroatom. Examples of heteroatoms include oxygen atoms, sulfur atoms, and nitrogen atoms.

[0028] Examples of cyclic imide compounds include aliphatic dicarboxylic acid imide compounds and cyclic imide compounds having a second ring. Examples of aliphatic dicarboxylic acid imide compounds include succinimide. Examples of cyclic imide compounds having a second ring include imide compounds of aromatic or alicyclic dicarboxylic acids. Examples of aromatic or alicyclic dicarboxylic acids include those having carboxyl groups on two adjacent atoms constituting the ring. Examples of cyclic imide compounds having a second ring include phthalimide and hydrogenated phthalimide compounds. Examples of hydrogenated phthalimide compounds include cyclohexa-3-ene-1,2-dicarboxymide and cyclohexane-1,2-dicarboxymide.

[0029] The imide ring may be an N-substituted imide ring having a substituent on the nitrogen atom of the imide. Examples of such substituents include hydroxyl groups, alkyl groups, alkoxy groups, and halogen atoms. Examples of alkyl groups include C1 to C4 alkyl groups, and may also include methyl groups and ethyl groups. Examples of alkoxy groups include C1 to C4 alkoxy groups, and may also include methoxy groups and ethoxy groups. Examples of halogen atoms include chlorine atoms and fluorine atoms.

[0030] The cyclic imide compound is preferably at least one selected from the group consisting of phthalimides and N-substituted phthalimides. The substituent on the nitrogen atom of the N-substituted phthalimide can be selected from the substituents exemplified for the N-substituted imide ring. The N-substituted phthalimide preferably includes, for example, at least one selected from the group consisting of N-hydroxyphthalimide, N-(2-hydroxyethyl)phthalimide, N-(cyclohexylthio)phthalimide, and N-(phenylthio)phthalimide. The phthalimide and / or N-substituted phthalimide may account for 50% by mass or more, more specifically 70% by mass or more, or 90% by mass or more, of the cyclic imide compound.

[0031] The non-aqueous electrolyte may contain one cyclic imide compound or two or more. The content of the cyclic imide compound in the non-aqueous electrolyte may be 1% by mass or less, 0.001% by mass or more and 1% by mass or less, or 0.001% by mass or more and 0.8% by mass or less.

[0032] (Phthalate Ester Compounds) Phthalate ester compounds include phthalate esters and their derivatives. Derivatives may have substituents bonded to an aromatic ring derived from phthalic acid. Examples of such substituents include hydroxyl groups, alkyl groups, alkoxy groups, and halogen atoms. Examples of alkyl groups include C1-C4 alkyl groups, and may also include methyl groups and ethyl groups. Examples of alkoxy groups include C1-C4 alkoxy groups, and may also include methoxy groups and ethoxy groups. Examples of halogen atoms include chlorine atoms and fluorine atoms.

[0033] The phthalate ester compound may also be a phthalate monoester compound, but a phthalate diester compound is preferable from the viewpoint that the resulting film easily protects the surface of the Li alloy. As the alcohol constituting the ester with phthalic acid (or its derivative), a saturated or unsaturated aliphatic alcohol of C1 to C20 (preferably C1 to C6) is preferable.

[0034] Specific examples of phthalate diester compounds include dimethyl phthalate, diethyl phthalate, diallyl phthalate, dibutyl phthalate, diisobutyl phthalate, and bis(2-ethylhexyl) phthalate. These may be used individually or in combination of two or more. The phthalate diester compound may constitute 50% by mass or more, and more specifically, 70% by mass or more, or even 90% by mass or more, of the phthalate ester compound.

[0035] The non-aqueous electrolyte may contain one phthalate ester compound or two or more. The content of the phthalate ester compound in the non-aqueous electrolyte may be 1% by mass or less, or 0.1% by mass or more and 1% by mass or less.

[0036] (Isocyanate Compounds) An isocyanate compound, for example, has at least one isocyanate group and a C1-C20 aliphatic hydrocarbon group or a C6-C20 aromatic hydrocarbon group. The aliphatic hydrocarbon group and aromatic hydrocarbon group constituting the isocyanate compound may have substituents. The substituents may be any group that can exist stably, for example, a halogen atom or a nitrile group. The aliphatic group may be an alicyclic aliphatic group, or a linear or branched aliphatic group. The aromatic hydrocarbon group is a hydrocarbon group having one or more aromatic rings, and may be a group in which an aromatic ring and an aliphatic group are linked.

[0037] The isocyanate compound can be a monoisocyanate compound having one isocyanate group, but a diisocyanate compound having two isocyanate groups is preferable. Diisocyanate compounds are thought to form composite films with higher chemical stability than monoisocyanate compounds and lower resistance than triisocyanate compounds. Furthermore, diisocyanate compounds have a high ability to form composite films even in small amounts and exhibit excellent stability within the battery.

[0038] A specific example of a diisocyanate compound is OCN-C ｎ H ２ｎExamples include compounds represented by -NCO (where n is an integer from 1 to 10) (e.g., hexamethylene diisocyanate), compounds having an alicyclic diyl group (e.g., 1,3-bis(isocyanatomethyl)cyclohexane, dicyclohexylmethane-4,4'-diisocyanate, bicyclo[2.2.1]heptane-2,5-diylbis(methylisocyanate), bicyclo[2.2.1]heptane-2,6-diylbis(methylisocyanate), isophorone diisocyanate), 2,2,4-trimethylhexamethylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate, and hexyl isocyanate. Among these, at least one selected from the group consisting of hexamethylene diisocyanate, 1,3-bis(isocyanatomethyl)cyclohexane, and isophorone diisocyanate is preferred. These may account for 50% or more by mass of the isocyanate compound, and more specifically, 70% or more by mass, or even 90% or more by mass.

[0039] When diisocyanate compounds are added to a non-aqueous electrolyte, the diisocyanate compounds may react with each other within the battery (in the non-aqueous electrolyte) to form isocyanurate, urea, and biuret compounds. Therefore, when a battery is disassembled and the non-aqueous electrolyte is analyzed, isocyanurate, urea, and biuret compounds derived from the diisocyanate compounds may be detected.

[0040] The non-aqueous electrolyte may contain one isocyanate compound or two or more isocyanate compounds. The content of the isocyanate compound in the non-aqueous electrolyte may be 3% by mass or less, 0.01% by mass or more and 2% by mass or less, or 0.01% by mass or more and 1.5% by mass or less.

[0041] For the analysis of non-aqueous electrolytes (additives), for example, liquid chromatography-mass spectrometry (LC / MS) or gas chromatography-mass spectrometry (GC / MS) can be used. Ultraviolet spectroscopy (UV) may also be performed in conjunction with nuclear magnetic resonance analysis (NMR), infrared absorption spectroscopy (IR), and mass spectrometry (MS).

[0042] The lithium primary battery described in this disclosure will be explained in more detail below.

[0043] [Lithium primary battery] (Positive electrode) The positive electrode contains a positive electrode mixture. The positive electrode mixture contains manganese dioxide as a positive electrode active material. The positive electrode containing manganese dioxide exhibits a relatively high voltage and has excellent pulse discharge characteristics. As the manganese dioxide, the one obtained by firing electrolytic manganese dioxide is preferably used. The manganese dioxide may be in a mixed crystal state containing a plurality of crystal states. The positive electrode may contain manganese oxides other than manganese dioxide. Examples of the manganese oxides other than manganese dioxide include MnO, Mn ３ O ４ 、Mn ２ O ３ 、Mn ２ O ７ etc. It is preferable that the main component of the manganese oxide contained in the positive electrode is manganese dioxide.

[0044] The manganese dioxide contained in the positive electrode may be doped with a small amount of lithium. If the doping amount of lithium is small, a high capacity can be ensured. Manganese dioxide and manganese dioxide doped with a small amount of lithium can be represented by Li ｘ MnO ２ (0 ≤ x ≤ 0.05). Note that the average composition of the entire manganese oxide contained in the positive electrode may be Li ｘ MnO ２ (0 ≤ x ≤ 0.05). Note that the ratio x of Li may be 0.05 or less in the initial state of discharge of the lithium primary battery. Generally, the ratio x of Li increases as the discharge of the lithium primary battery progresses. The oxidation number of manganese contained in manganese dioxide is theoretically 4. However, due to the inclusion of other manganese oxides in the positive electrode or the doping of lithium into manganese dioxide, the oxidation number of manganese may increase or decrease slightly from 4. Therefore, in Li ｘ MnO ２ the average oxidation number of manganese is allowed to increase or decrease slightly from 4.

[0045] The positive electrode is Li ｘ MnO ２In addition, it may include other positive electrode active materials used in lithium primary batteries. Examples of other positive electrode active materials include graphite fluoride. The proportion of manganese dioxide in the total positive electrode active material is preferably 90% by mass or more.

[0046] Electrolytic manganese dioxide is preferably used as the manganese dioxide. By adjusting the firing conditions, the crystallinity of manganese dioxide can be increased, and the specific surface area of ​​electrolytic manganese dioxide can be reduced. Li ｘ MnO ２ The BET specific surface area is 5m ２ / g or more, 40m ２ It may be less than / g. Li ｘ MnO ２ If the BET specific surface area is within the above range, self-discharge is suppressed, and the deterioration of pulse discharge characteristics after storage can be further suppressed.

[0047] Li ｘ MnO ２ The BET specific surface area can be measured by a known method, for example, by measuring a specific surface area measuring device (e.g., manufactured by Mountec Co., Ltd.) based on the BET method. For example, Li separated from the positive electrode taken from a battery ｘ MnO ２ This can be used as the measurement sample.

[0048] Li ｘ MnO ２ The median particle size may be between 5 μm and 40 μm. When the median particle size is within the above range, self-discharge is suppressed, and the deterioration of pulse discharge characteristics after storage can be further suppressed.

[0049] Li ｘ MnO ２ The median particle size is, for example, the median of the particle size distribution obtained by quantitative laser diffraction / scattering (qLD) method. For example, Li separated from the positive electrode extracted from a battery. ｘ MnO ２ The sample to be measured should be [the sample shown]. For measurement, for example, the SALD-7500nano manufactured by Shimadzu Corporation can be used.

[0050] The positive electrode mixture may contain a binder in addition to the positive electrode active material. The positive electrode mixture may also contain a conductive agent.

[0051] Examples of binders include fluororesins, rubber particles, and acrylic resins.

[0052] Examples of conductive materials include conductive carbon materials. Examples of conductive carbon materials include natural graphite, artificial graphite, carbon black, and carbon fibers.

[0053] The positive electrode may further include a positive electrode current collector that holds the positive electrode mixture. Examples of materials for the positive electrode current collector include stainless steel, aluminum, and titanium.

[0054] In the case of a coin-type battery, the positive electrode may be constructed by attaching a ring-shaped positive electrode current collector with an L-shaped cross-section to a positive electrode mixture pellet, or the positive electrode may be constructed using only the positive electrode mixture pellet. The positive electrode mixture pellet can be obtained, for example, by compression molding a wet positive electrode mixture prepared by adding an appropriate amount of water to a positive electrode active material, and then drying it.

[0055] In the case of a cylindrical battery, a positive electrode can be used that comprises a sheet-shaped positive electrode current collector and a positive electrode mixture layer held by the positive electrode current collector. A perforated current collector is preferred as the sheet-shaped positive electrode current collector. Examples of perforated current collectors include expanded metal, net, and punched metal. The positive electrode mixture layer can be obtained, for example, by coating the above-mentioned wet positive electrode mixture onto the surface of the sheet-shaped positive electrode current collector or filling the positive electrode current collector with it, applying pressure in the thickness direction, and drying it.

[0056] The positive electrode preferably comprises a perforated current collector as described above and a positive electrode mixture filled in the current collector. In particular, it is preferable to use a current collector containing at least one material selected from the group consisting of SUS444, SUS430, and SUS316. By using such a current collector, side reactions with the non-aqueous electrolyte and corrosion of the current collector can be suppressed in the lithium primary battery, and an increase in internal resistance and gas generation can be suppressed. In particular, such a current collector and LiCF, which is typically used as a lithium salt in lithium primary batteries ３ SO ３and LiClO ４ When combined with a non-aqueous electrolyte containing at least one of the above, side reactions between the current collector and the non-aqueous electrolyte can be suppressed more effectively. The thickness of the positive electrode is, for example, 300 μm or more and 900 μm or less.

[0057] (Negative electrode) The negative electrode may include, for example, a foil-like (sheet-like) lithium alloy. The lithium alloy is formed into any shape and thickness depending on the shape, dimensions, and performance specifications of the lithium primary battery.

[0058] In the case of cylindrical batteries, the negative electrode may include a negative electrode current collector (e.g., copper foil) supporting a lithium alloy, but it may also be a foil-shaped (sheet-shaped) lithium alloy without a negative electrode current collector. If the lithium alloy contains Mg, relatively strong Mg remains at the end of discharge, so the negative electrode can be constructed using only a foil-shaped (sheet-shaped) lithium alloy without using a negative electrode current collector. By using a lithium alloy containing Mg, fracture or partial loss of the negative electrode at the end of discharge, which occurs when the negative electrode does not include a negative electrode current collector, is suppressed. The shape of the negative electrode (lithium alloy) is maintained even at the end of discharge, and the conductivity of the entire negative electrode is ensured even when a negative electrode current collector is not used.

[0059] In the case of coin-type batteries, a hoop-shaped lithium alloy punched into a disc shape may be used as the negative electrode. In the case of cylindrical batteries, a sheet-shaped lithium alloy may be used as the negative electrode. The sheet can be obtained, for example, by extrusion molding. More specifically, in cylindrical batteries, lithium alloy foil having a shape with a longitudinal direction and a transverse direction may be used.

[0060] (Non-aqueous electrolyte) Non-aqueous electrolytes are used in which lithium salts are dissolved as a solute in a non-aqueous solvent.

[0061] Examples of non-aqueous solvents include organic solvents commonly used in non-aqueous electrolytes for lithium primary batteries. Examples of non-aqueous solvents include ethers, esters, and carbonate esters. Examples of non-aqueous solvents that can be used include dimethyl ether, γ-butyl lactone, propylene carbonate, ethylene carbonate, and 1,2-dimethoxyethane. The non-aqueous electrolyte may contain one non-aqueous solvent or two or more non-aqueous solvents.

[0062] From the viewpoint of improving the discharge characteristics of lithium primary batteries, the non-aqueous solvent preferably contains a cyclic carbonate ester with a high boiling point and a chain ether that has low viscosity even at low temperatures. The cyclic carbonate ester preferably contains at least one selected from the group consisting of propylene carbonate (PC) and ethylene carbonate (EC), with PC being particularly preferred. The chain ether preferably has a viscosity of 1 mPa·s or less at 25°C, and is particularly preferably dimethoxyethane (DME). The viscosity of the non-aqueous solvent is determined by measurement using a Rheosens m-VROC micro-sample viscometer at 25°C with a shear rate of 10,000 (1 / s).

[0063] Examples of lithium salts include LiCF ３ SO ３ LiClO ４ LiBF ４ LiPF ６ LiRaSO ３ (Ra is an alkyl fluoride with 1 to 4 carbon atoms), LiFSO ３ , LiN (SO ２ Rb) (SO ２ Rc) (Rb and Rc are each independently C1-C4 alkyl fluoride compounds), LiN (FSO) ２ ) ２ These are some examples. Lithium salts may be used individually or in combination of two or more types.

[0064] The concentration of lithium ions (total concentration of lithium salts) contained in the non-aqueous electrolyte is, for example, 0.2 mol / L or more and 2.0 mol / L or less, and may also be 0.3 mol / L or more and 1.5 mol / L or less.

[0065] The non-aqueous electrolyte may contain additives as needed. Examples of such additives include phthalimide, N-substituted phthalimide compounds, dimethyl phthalate, phthalate ester compounds, propane sultone, and vinylene carbonate. The total concentration of such additives in the non-aqueous electrolyte is, for example, 0.003 to 5 mol / L.

[0066] (Separator) Lithium primary batteries typically have a separator interposed between the positive and negative electrodes. As the separator, a porous sheet made of an insulating material that is resistant to the internal environment of the lithium primary battery may be used. Specifically, examples include nonwoven fabrics made of synthetic resin, microporous membranes made of synthetic resin, or laminates thereof.

[0067] Examples of synthetic resins used in nonwoven fabrics include polypropylene, polyphenylene sulfide, and polybutylene terephthalate. Examples of synthetic resins used in microporous membranes include polyethylene, polypropylene, and polyolefin resins such as ethylene-propylene copolymers. Microporous membranes may contain inorganic particles as needed.

[0068] The thickness of the separator is, for example, between 5 μm and 100 μm.

[0069] The structure of a lithium primary battery is not particularly limited. A lithium primary battery may be a coin-type battery equipped with a stacked electrode group formed by stacking a disc-shaped positive electrode and a disc-shaped negative electrode with a separator in between. A cylindrical battery equipped with a wound electrode group formed by spirally winding a strip-shaped positive electrode and a strip-shaped negative electrode with a separator in between may also be a cylindrical battery.

[0070] Figure 1 shows a cross-sectional front view of a cylindrical lithium primary battery according to one embodiment of the present disclosure. The lithium primary battery 10 contains an electrode group in which a positive electrode 1 and a negative electrode 2 are wound around a separator 3, together with a non-aqueous electrolyte (not shown) in a battery case 9. A sealing plate 8 is fitted to the opening of the battery case 9. A positive electrode lead 4 connected to the current collector 1a of the positive electrode 1 is connected to the sealing plate 8. A negative electrode lead 5 connected to the negative electrode 2 is connected to the case 9. In addition, an upper insulating plate 6 and a lower insulating plate 7 are arranged at the top and bottom of the electrode group, respectively, to prevent internal short circuits.

[0071] [Note] The above description of the embodiment discloses the following technology: (Technology 1) A positive electrode, a negative electrode, and a non-aqueous electrolyte, wherein the positive electrode is Li ｘ MnO ２A lithium primary battery comprising (0 ≤ x ≤ 0.05), wherein the negative electrode comprises an alloy containing lithium, magnesium, and potassium, the lithium content in the alloy is 89% by mass or more, the magnesium content in the alloy is 0.01% by mass or more and 10% by mass or less, and the potassium content in the alloy is 400 ppm by mass or less. (Technical 2) The lithium primary battery according to Technical 1, wherein the alloy contains aluminum, and the total content of magnesium and aluminum in the alloy is 0.02% by mass or more and 10% by mass or less. (Technical 3) Li ｘ MnO ２ The median particle size is 5 μm or more and 40 μm or less, a lithium primary battery as described in Technology 1 or 2. (Technology 4) Li ｘ MnO ２ The BET specific surface area is 5m ２ / g or more, 40m ２A lithium primary battery according to any one of Techniques 1 to 3, wherein the content of the cyclic imide compound in the non-aqueous electrolyte is 1% by mass or less. (Technology 5) A lithium primary battery according to any one of Techniques 1 to 4, wherein the non-aqueous electrolyte contains at least one additive selected from the group consisting of cyclic imide compounds, phthalate ester compounds, and isocyanate compounds. (Technology 6) A lithium primary battery according to Technique 5, wherein the cyclic imide compound contains at least one selected from the group consisting of phthalimide and N-substituted phthalimide. (Technology 7) A lithium primary battery according to Technique 6, wherein the N-substituted phthalimide contains at least one selected from the group consisting of N-hydroxyphthalimide, N-(2-hydroxyethyl)phthalimide, N-(cyclohexylthio)phthalimide, and N-(phenylthio)phthalimide. (Technology 8) A lithium primary battery according to any one of Techniques 5 to 7, wherein the content of the cyclic imide compound in the non-aqueous electrolyte is 1% by mass or less. (Technology 9) A lithium primary battery according to any one of Techniques 5 to 8, wherein the phthalate ester compound contains a phthalate diester compound. (Technical 10) The lithium primary battery according to Technical 9, wherein the phthalate diester compound comprises dimethyl phthalate. (Technical 11) The lithium primary battery according to any one of Technical 5 to 10, wherein the content of the phthalate ester compound in the non-aqueous electrolyte is 1% by mass or less. (Technical 12) The lithium primary battery according to any one of Technical 5 to 11, wherein the isocyanate compound comprises a diisocyanate compound. (Technical 13) The lithium primary battery according to Technical 12, wherein the diisocyanate compound comprises at least one selected from the group consisting of hexamethylene diisocyanate, 1,3-bis(isocyanatomethyl)cyclohexane, and isophorone diisocyanate. (Technical 14) The lithium primary battery according to any one of Technical 5 to 13, wherein the content of the isocyanate compound in the non-aqueous electrolyte is 3% by mass or less.

[0072] [Examples] The present disclosure will be described below in detail based on examples and comparative examples, but the present disclosure is not limited to the following examples.

[0073] 《Batteries A1-A18, Batteries B1-B9》 (Preparation of positive electrode) As a positive electrode, 100 parts by mass of calcined electrolytic manganese dioxide was mixed with 3 parts by mass of Ketjenblack, a conductive agent, 5 parts by mass of polytetrafluoroethylene, a binder, and an appropriate amount of pure water to prepare a wet positive electrode mixture.

[0074] Next, a positive electrode precursor was prepared by filling a positive electrode current collector made of expanded metal (SUS444) with a thickness of 0.4 mm with the positive electrode mixture. The positive electrode precursor was then dried, rolled to a thickness of 0.5 mm using a roll press, and cut to a predetermined size to obtain the positive electrode. Subsequently, a portion of the filled positive electrode mixture was peeled off, and one end of a stainless steel positive electrode lead was resistance-welded to the portion of the positive electrode current collector that was exposed.

[0075] (Fabrication of the negative electrode) A negative electrode was obtained by cutting a lithium metal foil or lithium alloy foil (thickness 200 μm) to a predetermined size. One end of a nickel negative electrode lead was connected to a predetermined location on the negative electrode by ultrasonic welding.

[0076] The lithium alloy foil had the foil composition shown in Tables 1 to 3. In addition to lithium, the lithium alloy foil contained the metal elements (Mg, K, and / or Al) shown in Tables 1 to 3. The content of each metal element in the lithium alloy foil was as shown in Tables 1 to 3. A value of "0" in the content column in Tables 1 to 3 means that the content is below the detection limit in ICP emission spectrometry.

[0077] (Fabrication of electrode group) An electrode group was fabricated by winding a positive electrode and a negative electrode with a separator in between. A microporous film made of polypropylene with a thickness of 25 μm was used as the separator.

[0078] (Preparation of non-aqueous electrolyte) Propylene carbonate (PC), ethylene carbonate (EC), and 1,2-dimethoxyethane (DME) were mixed in a volume ratio of 4:2:4 to obtain a non-aqueous solvent. LiCF was added to the non-aqueous solvent. ３ SO ３ A non-aqueous electrolyte was prepared by dissolving it at a concentration of 0.5 mol / L.

[0079] (Assembly of Lithium Primary Battery) The electrode group was housed in a cylindrical battery case that also served as the negative electrode terminal. An iron case (outer diameter 17 mm, height 45.5 mm) was used for the battery case. Next, a non-aqueous electrolyte was injected into the battery case, and the opening of the battery case was closed using a metal sealing plate that also served as the positive electrode terminal. The other end of the positive electrode lead was connected to the sealing plate, and the other end of the negative electrode lead was connected to the inner bottom surface of the battery case. In this way, a cylindrical lithium primary battery was fabricated. The battery immediately after assembly was discharged at 2.4 A for 2 minutes, and then aged for 7 days in an atmosphere of 45°C. The positive electrode active material after aging was Li ｘ MnO ２ The formula is expressed as follows, and the x value indicating the lithium doping amount was in the range of 0 < x ≤ 0.05. In the table, batteries A1 to A18 are examples, and batteries B1 to B9 are comparative examples.

[0080] Furthermore, Li contained in the positive electrode mixture ｘ MnO ２ The median particle size is 21–23 μm, and the BET specific surface area is 14–15 m². ２ It was / g.

[0081] [Evaluation] The aged batteries were discharged to a depth of discharge (DOD) of 80%. For the batteries at the end of discharge, the internal resistance (frequency 1 kHz) was measured using an AC resistance meter at a temperature of 20°C. In addition, the batteries at the end of discharge were left standing for 2 hours at a temperature of -30°C, and then a pulse discharge of 300 mA for 1 second was performed at a temperature of -30°C, and the lowest voltage at this time was determined as the pulse discharge voltage.

[0082] The evaluation results are shown in Tables 1 to 3. In Tables 1 to 3, the internal resistance is expressed as a relative value when the internal resistance of battery B2 is set to 100. The pulse discharge voltage is expressed as a relative value when the pulse discharge voltage of battery B2 is set to 100.

[0083]

[0084]

[0085]

[0086] Batteries A1 to A18 exhibited low internal resistance and high pulse discharge voltage at the end of their discharge phase.

[0087] In batteries B1 to B5, the pulse discharge voltage at the end of discharge decreased because Li metal foil or Li alloy foil without Mg and / or K was used as the negative electrode. In battery B6, Li-Mg-K alloy foil was used, but the pulse discharge voltage at the end of discharge decreased because the Mg content was greater than 10 mass%. In battery B7, Li-Mg-K alloy foil was used, but the pulse discharge voltage at the end of discharge decreased because the K content was greater than 400 mass ppm. In batteries B8 to B9, Li-Mg-K-Al alloy foil was used, but the pulse discharge voltage at the end of discharge decreased because the Li content was less than 89 mass%.

[0088] When the negative electrode did not contain Mg, the improvement in the pulse discharge voltage at the end of discharge due to the addition of 20 ppm by mass of K was small (B1: 87 → B4: 89). In contrast, when the negative electrode contained Mg, the pulse discharge voltage at the end of discharge was significantly improved by the addition of 20 ppm by mass of K (B2: 100 → A4: 115). From this, it can be seen that the effect of suppressing the decrease in pulse discharge voltage at the end of discharge by adding K is significantly obtained when the negative electrode (lithium alloy) contains Mg.

[0089] As shown in Table 1, batteries A1 to A7, which have an Mg content of 0.5 mass% and a K content of 0.5 to 400 mass ppm, obtained a high voltage at the end of discharge. Batteries A8 to A13, which have a K content of 20 mass ppm and an Mg content of 0.01 to 10 mass%, also obtained a high voltage at the end of discharge.

[0090] As shown in Table 3, in batteries A14 to A18, which used Li-Mg-K-Al foil as the negative electrode, the pulse discharge voltage at the end of discharge was further increased. For example, in battery A11 (Li-Mg-K foil, Mg content: 1% by mass, K content: 20 ppm by mass), the pulse discharge voltage was 111. In contrast, in battery A16 (Li-Mg-K-Al foil, Mg content: 1% by mass, K content: 20 ppm by mass, Al content: 1%), the pulse discharge voltage was 114, showing a further improvement in the pulse discharge voltage at the end of discharge.

[0091] 《Batteries A19-A26》 In the preparation of the non-aqueous electrolyte, additives were further added to the non-aqueous electrolyte. The compounds used as additives were those shown in Table 4. The content (mass%) of the additives in the non-aqueous electrolyte was the value shown in Table 4. Except as described above, batteries A19-A26 were prepared and evaluated in the same manner as battery A3.

[0092] The evaluation results are shown in Table 4. In Table 4, the internal resistance is expressed as a relative value when the internal resistance of battery B2 is set to 100. The pulse discharge voltage is expressed as a relative value when the pulse discharge voltage of battery B2 is set to 100.

[0093]

[0094] As shown in Table 4, in batteries A19 to A26, which contained additives in the non-aqueous electrolyte, the end-of-discharge internal resistance was further reduced and the pulse discharge voltage was further increased.

[0095] The lithium primary battery of this disclosure is suitably used, for example, as a main power source and memory backup power source for various meters (e.g., smart meters for electricity, water, gas, etc.).

[0096] Novel features of the present invention are described in the appended claims, but the present invention, both in terms of structure and content, and in conjunction with other objects and features of the present invention, will be better understood by the following detailed description in conjunction with the drawings.

[0097] 1: Positive electrode, 1a: Positive electrode current collector, 2: Negative electrode, 3: Separator, 4: Positive electrode lead, 5: Negative electrode lead, 6: Upper insulating plate, 7: Lower insulating plate, 8: Sealing plate, 9: Battery case, 10: Lithium primary battery

Claims

1. The device comprises a positive electrode, a negative electrode, and a non-aqueous electrolyte, wherein the positive electrode is Li ｘ MnO ２ A lithium primary battery comprising (0 ≤ x ≤ 0.05), wherein the negative electrode comprises an alloy containing lithium, magnesium, and potassium, the lithium content in the alloy is 89% by mass or more, the magnesium content in the alloy is 0.01% by mass or more and 10% by mass or less, and the potassium content in the alloy is 400 ppm by mass or less.

2. The lithium primary battery according to claim 1, wherein the alloy contains aluminum, and the total content of magnesium and aluminum in the alloy is 0.02% by mass or more and 10% by mass or less.

3. Li ｘ MnO ２ The lithium primary battery according to claim 1, wherein the median particle size is 5 μm or more and 40 μm or less.

4. Li ｘ MnO ２ The BET specific surface area is 5m ２ / g or more, 40m ２ A lithium primary battery according to claim 1, wherein the value is less than or equal to / g.

5. The lithium primary battery according to claim 1, wherein the non-aqueous electrolyte contains at least one additive selected from the group consisting of cyclic imide compounds, phthalate compounds, and isocyanate compounds.

6. The lithium primary battery according to claim 5, wherein the cyclic imide compound comprises at least one selected from the group consisting of phthalimides and N-substituted phthalimides.

7. The lithium primary battery according to claim 6, wherein the N-substituted phthalimide comprises at least one selected from the group consisting of N-hydroxyphthalimide, N-(2-hydroxyethyl)phthalimide, N-(cyclohexylthio)phthalimide, and N-(phenylthio)phthalimide.

8. The lithium primary battery according to claim 5, wherein the content of the cyclic imide compound in the non-aqueous electrolyte is 1% by mass or less.

9. The lithium primary battery according to claim 5, wherein the phthalate ester compound comprises a phthalate diester compound.

10. The lithium primary battery according to claim 9, wherein the phthalate diester compound comprises dimethyl phthalate.

11. The lithium primary battery according to claim 5, wherein the content of the phthalate ester compound in the non-aqueous electrolyte is 1% by mass or less.

12. The lithium primary battery according to claim 5, wherein the isocyanate compound comprises a diisocyanate compound.

13. The lithium primary battery according to claim 12, wherein the diisocyanate compound comprises at least one selected from the group consisting of hexamethylene diisocyanate, 1,3-bis(isocyanatomethyl)cyclohexane, and isophorone diisocyanate.

14. The lithium primary battery according to claim 5, wherein the content of the isocyanate compound in the non-aqueous electrolyte is 3% by mass or less.

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