Lithium primary battery

Abstract

This lithium primary battery comprises a positive electrode, a negative electrode, and a nonaqueous electrolyte solution, wherein: the positive electrode contains at least one selected from the group consisting of manganese dioxide and graphite fluoride; the negative electrode contains at least one of lithium metal and a lithium alloy; and the nonaqueous electrolyte solution contains a solvent, a solute, and a magnesium salt, wherein the solvent contains dimethoxyethane, the magnesium salt contains at least one selected from the group consisting of a trifluoromethanesulfonate anion and a sulfonylimide anion, the volume fraction of dimethoxyethane in the solvent is 5 vol% to 90 vol% inclusive, and the mass fraction of the magnesium salt in the nonaqueous electrolyte solution is 7 mass% or less.

Description

Lithium primary battery Cross-reference of related applications

[0001] This disclosure claims priority with respect to Japanese Patent Application No. 2024-171075, filed with the Japan Patent Office on 30 September 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. The positive electrode of a lithium primary battery uses materials such as manganese dioxide or graphite fluoride. The negative electrode of a lithium primary battery uses, for example, sheet-like (foil-like) metallic lithium or a lithium alloy.

[0004] Patent Document 1 proposes "an electrolyte medium for lithium secondary batteries, comprising a low dielectric constant solvent, a lithium salt, and a polyvalent cationic salt, wherein the polyvalent cationic salt is contained in a dispersed particle state and in a fluid state without being immobilized, and does not contain a high dielectric constant solvent, or contains a content of 20% by mass or less." Furthermore, as the polyvalent cationic salt, "at least one selected from the group consisting of magnesium trifluoromethanesulfonate, magnesium oxide, magnesium bis(trifluoromethanesulfonyl)imide, calcium trifluoromethanesulfonate, calcium oxide, calcium bis(trifluoromethanesulfonyl)imide, aluminum trifluoromethanesulfonate, and aluminum oxide."

[0005] Patent Document 2 describes that magnesium trifluoromethanesulfonate can be used as an additive in which the content in the non-aqueous electrolyte is 0.01% to 5.0% by mass.

[0006] Japanese Patent Publication No. 2022-049787, International Publication No. 2022 / 158397

[0007] Lithium primary batteries are expected to be used under a wider range of conditions in the future, and further improvements in reliability are necessary to achieve this.

[0008] One aspect of the present disclosure relates to a lithium primary battery comprising a positive electrode, a negative electrode, and a non-aqueous electrolyte, wherein the positive electrode comprises at least one selected from the group consisting of manganese dioxide and graphite fluoride, the negative electrode comprises at least one of metallic lithium and a lithium alloy, the non-aqueous electrolyte comprises a solvent, a solute, and a magnesium salt, the solvent comprises dimethoxyethane, the magnesium salt comprises at least one selected from the group consisting of trifluoromethanesulfonic acid anion and sulfonylimide anion, the volume content of the dimethoxyethane in the solvent is 5% by volume or more and 90% by volume or less, and the mass content of the magnesium salt in the non-aqueous electrolyte is 7% by mass or less.

[0009] According to this disclosure, a highly reliable lithium primary battery can be obtained.

[0010] This is a front view showing a cross-section of a part of a lithium primary battery according to the embodiment of this disclosure.

[0011] 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.

[0012] The embodiments of this disclosure will be described below with examples, but this disclosure is not limited to the examples described below. In the following description, specific numerical values ​​and materials may be given as examples, but other numerical values ​​and materials may be applied as long as the effects of this disclosure are 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 "greater than or equal to numerical value A and less than or equal to numerical value B". In the following description, when lower and upper limits are given as examples for numerical values ​​of specific physical properties or conditions, either of the given lower limits and either of the given upper limits can be arbitrarily combined, as long as the lower limit does not exceed the upper limit. When multiple materials are given as examples, one of them may be selected and used alone, or two or more may be used in combination.

[0013] A lithium primary battery according to the embodiments of this disclosure comprises a positive electrode, a negative electrode, and a non-aqueous electrolyte. The positive electrode of the lithium primary battery includes at least one selected from the group consisting of manganese dioxide and graphite fluoride. The negative electrode of the lithium primary battery includes at least one of metallic lithium and a lithium alloy.

[0014] The non-aqueous electrolyte contains a solvent and a solute. The solvent contains dimethoxyethane (hereinafter also referred to as "DME"). It is preferable to use 1,2-dimethoxyethane as the DME. The solute contains a magnesium salt as an additive.

[0015] Magnesium salts are trifluoromethanesulfonate anions (CF ３ SO ３ - It contains at least one selected from the group consisting of magnesium trifluoromethanesulfonate (Mg(TFS)2) and sulfonylimide anion (Mg(FSI)2). That is, the magnesium salt contains magnesium trifluoromethanesulfonate (Mg(TFS)2) and magnesium sulfonylimide (Mg(FSI)2) ２ It includes at least one selected from the group consisting of ).

[0016] Among them, magnesium salts include Mg(TFS) ２ It is preferable that it contains Mg(TFS)2. It is preferable that Mg(TFS)2 accounts for 80% or more by mass of the magnesium salt, and it may also be 100% Mg(TFS)2.

[0017] Smart meters that automatically transmit gas and water usage data use maintenance-free lithium primary batteries. When lithium primary batteries are used for extended periods, the pulse discharge voltage decreases as resistance increases, which can shorten the battery life beyond expectations. The pulse discharge output tends to decrease particularly in cold climates. In contrast, according to this disclosure, it is possible to suppress the decrease in low-temperature pulse discharge voltage from the initial stage to after high-temperature storage, thereby obtaining a highly reliable lithium primary battery.

[0018] The solvent in non-aqueous electrolytes generally includes a high dielectric constant solvent and a low viscosity solvent. DME is a low viscosity solvent. DME does not undergo oxidative decomposition at the positive electrode potential of a lithium primary battery. Furthermore, DME has high reduction resistance and does not undergo reductive decomposition even on a negative electrode containing highly reactive metallic lithium.

[0019] Furthermore, dimethoxyethane (DME) readily oxidizes and decomposes on the positive electrode within the operating potential range of a secondary battery, potentially leading to increased internal pressure and expansion due to the resulting gases, and is therefore undesirable for lithium secondary batteries.

[0020] A non-aqueous electrolyte containing DME at a predetermined concentration contains the aforementioned magnesium salt (e.g., Mg(TFS)) ２ When DME is dissolved, the ionized magnesium ions readily dissipate onto the negative electrode containing metallic lithium, forming a solid solution (alloy) of lithium and magnesium, which is thought to significantly modify the negative electrode surface. In this process, since DME is not easily reduced or decomposed, the alloying reaction between lithium and magnesium is not inhibited and is presumed to proceed rapidly. The alloying reaction between lithium and magnesium is thought to roughen the negative electrode surface and improve its durability. As a result, the decrease in low-temperature pulsed discharge voltage due to increased internal resistance is suppressed over a long period of time.

[0021] On the other hand, it is thought that the TFS anion or anion reacts with the solvent contained in the non-aqueous electrolyte on the Mg-containing negative electrode surface to form an organic-inorganic hybrid coating (SEI coating) on ​​the negative electrode surface. This coating is thought to have low resistance and excellent durability.

[0022] However, it is desirable that the volume content of DME in the solvent (hereinafter also referred to as "content C(DME)") be between 5% by volume and 90% by volume. If the content C(DME) is less than 5% by volume, the viscosity of the electrolyte increases, which increases the internal resistance, and the output, especially at low temperatures, decreases significantly. If the content C(DME) exceeds 90% by volume, the ionization ability of the solute decreases, the ionic conductivity of the electrolyte decreases, and it is difficult to suppress the increase in internal resistance. The content C(DME) is preferably between 10% by volume and 80% by volume, preferably between 20% by volume and 70% by volume, and more preferably between 20% by volume and 40% by volume.

[0023] Further, the mass content ratio of the magnesium salt in the non-aqueous electrolyte (hereinafter, also referred to as "content ratio C(Mg)") is 7% by mass or less, preferably 5% by mass or less. When the content ratio C(Mg) exceeds 7% by mass, the initial output decreases, the output decrease rate increases during long-term use, and it becomes difficult to suppress the increase in internal resistance. The range of the content ratio C(Mg) may be, for example, 0.01% by mass to 7% by mass (e.g., 5% by mass), 0.5% by mass to 7% by mass (e.g., 5% by mass), or 1% by mass to 7% by mass (e.g., 5% by mass).

[0024] Incidentally, the smaller the content ratio C(DME), the relatively larger the content ratios of ethylene carbonate, propylene carbonate, etc., and the tendency is for the SEI (Solid Electrolyte Interface) film formed on the negative electrode surface to increase. On the other hand, since such an SEI film is not in a good state, it is preferable to use a relatively large amount of magnesium salt to modify the negative electrode surface.

[0025] The content ratio of the magnesium salt in the non-aqueous electrolyte is the mass content ratio of the magnesium salt with respect to the entire non-aqueous electrolyte. For example, it is desirable that the mass content ratio of the magnesium salt in the non-aqueous electrolyte is within the above range immediately after the manufacture of the battery (or at the time of preparation of the non-aqueous electrolyte). In a battery after a certain period has elapsed since manufacture, a part of the magnesium salt has been consumed for the formation of the SEI film. Therefore, even if a trace amount of magnesium salt is detected from the non-aqueous electrolyte, the above effects of the magnesium salt are recognized. In that case, the lower limit of the content ratio C(Mg) may be above the detection limit, and the range of the content ratio C(Mg) may be, for example, 0% by mass to 5% by mass, 0% by mass to 3% by mass, or 0% by mass to 1% by mass.

[0026] As the sulfonylimide (FSI) anion, a fluorine-containing sulfonylimide anion is preferable. Specifically, Mg(FSI) ２ is Mg(N(SO ２ Ra)(SO ２ Rb)) ２It can be represented by the formula. In the formula, Ra and Rb are each independently a fluorine atom or a fluoroalkyl group having 1 to 4 carbon atoms. The fluoroalkyl group may be linear or branched. Examples of the fluoroalkyl group include CF ３ 、C ２ F ５ 、C ３ F ７ 、C ４ F ９ and the like.

[0027] Specific examples of the fluorine-containing sulfonylimide anion include bis(fluorosulfonyl)imide anion ( - N(SO ２ F) ２ )(hereinafter, also referred to as "FSI anion"), bis(trifluoromethanesulfonyl)imide anion ( - N(CF ３ SO ２ ) ２ ) and the like. Among the fluorine-containing sulfonylimide anions, particularly, FSI anion is preferable.

[0028] For the analysis of the non-aqueous electrolyte, for example, liquid chromatography-mass spectrometry (LC / MS) or gas chromatography-mass spectrometry (GC / MS) can be used. Ultraviolet spectroscopic analysis (UV) may be performed together with nuclear magnetic resonance analysis (NMR), infrared absorption spectroscopic analysis (IR), and mass spectrometry (MS).

[0029] Hereinafter, the lithium primary battery of the present disclosure will be described more specifically.

[0030] [Lithium Primary Battery] (Positive Electrode) The positive electrode contains at least one selected from the group consisting of manganese dioxide and graphite fluoride as a positive electrode active material. As the manganese dioxide, that obtained by firing electrolytic manganese dioxide is preferably used. The positive electrode containing manganese dioxide exhibits a relatively high voltage and has excellent pulse discharge characteristics. The manganese dioxide may be in a mixed crystal state containing a plurality of crystal states. The positive electrode may contain a manganese oxide other than manganese dioxide. Examples of the manganese oxide other than manganese dioxide include MnO, Mn ３ O ４ 、Mn２ O ３ Mn ２ O ７ These are some examples. Preferably, the main component of the manganese oxide contained in the positive electrode is manganese dioxide. Here, "main component" means that the proportion of manganese dioxide in the manganese oxide is 50% by mass or more. The proportion of manganese dioxide in the manganese oxide may be 70% by mass or more, or 90% by mass or more.

[0031] The positive electrode comprises, for example, a positive electrode current collector and a positive electrode mixture layer held by the positive electrode current collector. The positive electrode mixture layer is formed, for example, by coating a wet positive electrode mixture onto the surface of a sheet-like positive electrode current collector or filling the positive electrode current collector with it, applying pressure in the thickness direction, and drying it.

[0032] The positive electrode mixture may include a positive electrode active material, a binder, a conductive agent, and the like. Examples of binders include fluororesins such as polytetrafluoroethylene, rubber particles, and acrylic resins. Examples of conductive agents include conductive carbon materials. Examples of conductive carbon materials include natural graphite, artificial graphite, carbon black, and carbon fibers.

[0033] Examples of materials for the positive electrode current collector include stainless steel, aluminum, and titanium. A perforated current collector is preferred for the positive electrode current collector. Examples of perforated current collectors include expanded metal, net, and punched metal.

[0034] 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 and drying a wet positive electrode mixture prepared by adding an appropriate amount of water to the positive electrode active material and additives.

[0035] 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.

[0036] (Negative electrode) The negative electrode may include, for example, at least one of metallic lithium and lithium alloy in foil form (also referred to as "lithium foil"). The lithium foil is formed into any shape and thickness depending on the shape, dimensions, and performance specifications of the lithium primary battery.

[0037] In the case of a cylindrical battery, the negative electrode may include a negative electrode current collector (e.g., copper foil) supporting a sheet-like lithium foil, but it may not include a negative electrode current collector. The sheet-like lithium foil can be obtained, for example, by extrusion molding. In the case of a coin-type battery, a hoop-shaped lithium foil may be punched out into a disc shape and used as the negative electrode.

[0038] The lithium alloy may contain Mg at a pre-existing content of 10% by mass or less. When the lithium alloy contains Mg, relatively strong Mg remains at the end of discharge, allowing the negative electrode to be constructed using only the lithium alloy without the need for 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 can occur when the negative electrode does not contain 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.

[0039] From the viewpoint of improving output characteristics during long-term use, the lithium alloy may further contain Al. From the viewpoint of reducing internal resistance and ensuring capacity, the Li content in the lithium alloy may be 89% by mass or more, 90% by mass or more, or 95% by mass or more.

[0040] From the viewpoint of effectively suppressing the deterioration of output characteristics during long-term use, the Mg content in the lithium alloy is preferably 0.01% by mass or more and 10% by mass or less, more preferably 0.05% by mass or more and 8% by mass or less, and even more preferably 0.1% by mass or more and 7% by mass or less.

[0041] Lithium alloys may contain other metallic elements besides Li, Mg, and Al. Examples of other metallic elements include Sn, Ni, Pb, In, Na, K, Ca, Fe, Ba, and Sr. From the viewpoint of ensuring discharge capacity and stabilizing internal resistance, the total content of metallic elements other than lithium in the lithium alloy is preferably 11% by mass or less.

[0042] The composition of lithium alloys can be determined by inductively coupled plasma (ICP) emission spectrometry or atomic absorption spectrometry (AAS).

[0043] (Non-aqueous electrolyte) The non-aqueous electrolyte contains a solvent and a solute. The solvent contains at least DME. The solvent other than DME can be any organic solvent that is commonly used in the electrolyte of lithium primary batteries. Examples of such solvents include ethers, carboxylic acid esters, and carbonate esters. Among these, carbonate esters are preferred.

[0044] As carbonate esters, cyclic carbonate esters such as propylene carbonate (PC) and ethylene carbonate (EC) are preferred because they are high dielectric constant solvents. Carbonate esters may be used individually or in combination of two or more.

[0045] The cyclic carbonate ester preferably contains at least one selected from the group consisting of PC and EC, and more preferably uses at least EC. However, the volume content of ethylene carbonate in the solvent (hereinafter also referred to as "C(EC)") is preferably 30% by volume or less, and more preferably 20% by volume or less, from the viewpoint of forming a better SEI film. The volume content of ethylene carbonate in the solvent C(EC) is preferably 5% by volume or more, and more preferably 10% by volume or more, from the viewpoint of forming a necessary and sufficient amount of a suitable SEI film.

[0046] When the solvent contains PC and EC, it is preferable that the volume content of PC in the solvent (hereinafter also referred to as "C(PC)") is greater than the volume content of EC in the solvent (hereinafter also referred to as "C(EC)"). The ratio of C(EC) to C(PC), C(EC) / C(PC), is preferably 1 / 8 to 1 / 1, and more preferably 1 / 2.5 to 1 / 1.5.

[0047] The solute contains the aforementioned magnesium salt as an additive, and as the main electrolyte salt, for example, lithium trifluoromethanesulfonate (LiCF ３ SO ３ (i.e., LiTFS), LiClO ４ LiBF ４ LiRcSO ３ (Rc is a fluorine atom or a fluorinated alkyl group having 2 to 4 carbon atoms), and lithium salts such as lithium salts of the sulfonylimide anions described above (e.g., bis(fluorosulfonyl)imidolithium (i.e., LiFSI)). Among these, LiTFS and LiFSI are preferred, and LiTFS is more preferred. One lithium salt may be used alone, or two or more may be used in combination. LiTFS preferably accounts for 80% by mass or more of the lithium salt, and it may be 100% LiTFS.

[0048] The concentration of lithium ions (concentration of lithium salt) 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.

[0049] The non-aqueous electrolyte may contain additives, such as cyclic sulfonic acid esters (e.g., propane sultone), ethylene sulfite (e.g., ethylene sulfite), other cyclic carbonate esters (e.g., vinylene carbonate, fluoroethylene carbonate), nitrile compounds (e.g., adiponitrile, succinonitrile), isocyanates (e.g., hexamethylene diisocyanate, 1,3-bis(isocyanatomethyl)cyclohexane, isophorone diisocyanate), cyclic imides (e.g., phthalimide, hydroxyphthalimide), and phthalate esters (e.g., dimethyl phthalate, diethyl phthalate).

[0050] (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.

[0051] 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. The thickness of the separator is, for example, 5 μm or more and 100 μm or less.

[0052] 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.

[0053] Figure 1 shows a cross-sectional front view of a part of a cylindrical lithium primary battery according to one embodiment of the present disclosure. The lithium primary battery 10 has an electrode group in which a positive electrode 1 and a negative electrode 2 are wound around a separator 3, and this electrode group is housed in a battery case 9 together with an electrolyte (not shown). 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 battery case 9. In addition, to prevent internal short circuits, an upper insulating plate 6 and a lower insulating plate 7 are arranged at the top and bottom of the electrode group, respectively.

[0054] [Note] The above description of embodiments discloses the following technologies. (Technology 1) A lithium primary battery comprising a positive electrode, a negative electrode, and a non-aqueous electrolyte, wherein the positive electrode comprises at least one selected from the group consisting of manganese dioxide and graphite fluoride, the negative electrode comprises at least one of metallic lithium and a lithium alloy, the non-aqueous electrolyte comprises a solvent, a solute, and a magnesium salt, the solvent comprises dimethoxyethane, the magnesium salt comprises at least one selected from the group consisting of trifluoromethanesulfonic acid anion and sulfonylimide anion, the volume content of the dimethoxyethane in the solvent is 5% by volume or more and 90% by volume or less, and the content of the magnesium salt in the non-aqueous electrolyte is 7% by mass or less. (Technology 2) The lithium primary battery according to Technology 1, wherein the solvent further comprises ethylene carbonate. (Technology 3) The lithium primary battery according to Technology 2, wherein the volume content of ethylene carbonate in the solvent is 30% by volume or less. (Technical 4) The lithium primary battery according to Technical 2 or 3, wherein the solvent further comprises propylene carbonate. (Technical 5) The lithium primary battery according to Technical 4, wherein the volume content of the propylene carbonate in the solvent is greater than the volume content of the ethylene carbonate in the solvent.

[0055] [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.

[0056] 《Batteries A1-A13 and Batteries B1-B3》 (Preparation of positive electrode) 100 parts by mass of positive electrode active material 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. The positive electrode active material was electrolytic manganese dioxide (MnO2) or graphite fluoride ((CF)) fired at 400°C for 5 hours. ｎ ) was used.

[0057] Next, a positive electrode precursor was prepared by filling a positive electrode current collector made of expanded metal made of stainless steel with a thickness of 0.4 mm with the positive electrode mixture. Then, the positive electrode precursor was 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.

[0058] (Fabrication of the negative electrode) A negative electrode was obtained by cutting a metallic lithium 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 pressure ultrasonic welding.

[0059] (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.

[0060] (Preparation of non-aqueous electrolyte) In a solvent with the composition shown in Table 1, lithium trifluoromethanesulfonate (LiTFS) and magnesium trifluoromethanesulfonate (Mg(TFS)) ２ A non-aqueous electrolyte was prepared by dissolving ) and . The concentration of LiTFS in the electrolyte was set to 0.5 mol / L. Mg(TFS) in the non-aqueous electrolyte ２ The mass content is shown in Table 1.

[0061] (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, after injecting electrolyte into the battery case, 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 lithium primary battery was manufactured. The battery immediately after assembly was discharged at 1 A for 1 minute, and then aged for 3 days in an atmosphere of 45°C. In Table 1, batteries A1 to A13 are examples, and batteries B1 to B3 are comparative examples.

[0062] The following pulse discharge characteristics (output characteristics) were evaluated for each of the batteries obtained in the examples and comparative examples.

[0063] [Evaluation] (Initial and post-storage output voltage) For the aged batteries, a pulse discharge of 200 mA for 1 second was performed at -30°C, and the lowest voltage at this time was determined as the initial output voltage X1. Subsequently, a constant current discharge of 2.5 mA was performed at 25°C until the depth of discharge (DOD) reached 75% (until the discharged amount reached 75% of the battery capacity). The discharged batteries were stored at 70°C for 120 days. For the stored batteries, the AC resistance (ACR) was measured using the two-terminal method at 25°C, and the post-storage internal resistance (IR) was determined. Furthermore, a pulse discharge was performed in the same manner as above, and the lowest voltage at this time was determined as the post-storage output voltage X2.

[0064] (Power Maintenance Rate) Using X1 and X2 obtained above, the power maintenance rate was calculated using the formula ΔX (%) = (X2) / X1 × 100.

[0065] The evaluation results are shown in Table 1. Note that the initial output (pulse discharge voltage) and IR after storage in Table 1 are expressed as relative values ​​(exponents) with the initial output of battery B1 in Comparative Example 1 set to 100.

[0066]

[0067] In batteries A1 to A13, which used a non-aqueous electrolyte containing DME at a predetermined volume content and a magnesium salt at a predetermined mass content, the deterioration of output characteristics after storage was suppressed, and the internal resistance IR after storage was kept low.

[0068] On the other hand, when the volume content of DME in the solvent was less than 5% by volume, both the retention rate of battery output after storage and the internal resistance (IR) increased. Furthermore, when the volume content of DME in the solvent was less than 5% by volume, the initial output of the battery decreased significantly.

[0069] When the mass content of magnesium salts in the non-aqueous electrolyte exceeded 5% by mass, the internal resistance (IR) after battery storage increased, or the output decreased significantly after storage.

[0070] 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.).

[0071] Although the present invention has been described in relation to preferred embodiments at present, such disclosure should not be interpreted restrictively. Various modifications and alterations will undoubtedly become apparent to those skilled in the art in the field to which the invention pertains by reading the above disclosure. Accordingly, the appended claims should be interpreted as encompassing all modifications and alterations without departing from the true spirit and scope of the invention.

[0072] 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. A lithium primary battery comprising a positive electrode, a negative electrode, and a non-aqueous electrolyte, wherein the positive electrode comprises at least one selected from the group consisting of manganese dioxide and graphite fluoride, the negative electrode comprises at least one of metallic lithium and a lithium alloy, the non-aqueous electrolyte comprises a solvent, a solute, and a magnesium salt, the solvent comprises dimethoxyethane, the magnesium salt comprises at least one selected from the group consisting of trifluoromethanesulfonic acid anion and sulfonylimide anion, the volume content of the dimethoxyethane in the solvent is 5% by volume or more and 90% by volume or less, and the mass content of the magnesium salt in the non-aqueous electrolyte is 7% by mass or less.

2. The lithium primary battery according to claim 1, wherein the solvent further comprises ethylene carbonate.

3. The lithium primary battery according to claim 2, wherein the volume content of ethylene carbonate in the solvent is 30% by volume or less.

4. The lithium primary battery according to claim 2, wherein the solvent further comprises propylene carbonate.

5. The lithium primary battery according to claim 4, wherein the volume content of propylene carbonate in the solvent is greater than the volume content of ethylene carbonate in the solvent.

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