Lithium primary battery

Abstract

This lithium primary battery is provided with a positive electrode, a negative electrode, and a non-aqueous electrolyte solution. The positive electrode contains manganese dioxide. The negative electrode includes a first lithium layer and an aluminum layer laminated on the first lithium layer. The first lithium layer is an alloy layer containing lithium and magnesium. The content of lithium in the alloy layer is from 89% by mass to 99.98% by mass (inclusive), and the content of magnesium in the alloy layer is from 0.02% by mass to 1.5% by mass (inclusive).

Description

Technical Field

[0001] This application relates to a primary lithium battery. Background Technology

[0002] Lithium-ion 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-ion primary battery uses materials such as manganese dioxide. The negative electrode uses, for example, sheet-like (foil-like) metallic lithium or lithium alloys.

[0003] Patent Document 1 discloses a non-aqueous electrolyte battery, characterized by comprising a positive electrode, a negative electrode, and a non-aqueous electrolyte. The negative electrode has a mixed alloy layer obtained by alloying the surface of a lithium alloy containing at least one metal element selected from In, Mg, Sn, Pd, Zn, Pb, Ni, Ag, and Ca, and Li with Al. The mixed alloy layer of the negative electrode is disposed opposite to the positive electrode. In Example 2 of Patent Document 1, a lithium alloy containing 2% by weight of Mg is used.

[0004] Patent document 2 discloses a cylindrical non-aqueous electrolyte primary battery, characterized by having an electrode assembly with a spiral structure obtained by winding a positive electrode containing manganese dioxide and a negative electrode with a spacer between them. The negative electrode has a lithium metal containing layer consisting of only one continuous layer on one side of the current collector. The lithium metal containing layer covers more than 85% of the area of ​​the surface on which the lithium metal containing layer is formed in the current collector. At least a portion of the surface of the lithium metal containing layer on the side opposite to the current collector is formed with a lithium-aluminum alloy.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent Application Publication No. 3-37964

[0008] Patent Document 2: Japanese Patent Application Publication No. 2012-138225 Summary of the Invention

[0009] The problem that the invention aims to solve

[0010] In primary lithium batteries, it is required to suppress the degradation of discharge characteristics.

[0011] Methods for solving problems

[0012] One aspect of this application relates to a lithium primary battery comprising a positive electrode, a negative electrode, and a non-aqueous electrolyte. The positive electrode comprises manganese dioxide, and the negative electrode comprises a first lithium layer and an aluminum layer stacked on the first lithium layer. The first lithium layer is an alloy layer comprising lithium and magnesium. The lithium content in the alloy layer is 89% by mass or more and 99.98% by mass or less, and the magnesium content in the alloy layer is 0.02% by mass or more and 1.5% by mass or less.

[0013] Invention Effects

[0014] According to this application, it is possible to suppress the degradation of the discharge characteristics of a lithium primary battery.

[0015] The novel features of the invention are set forth within the scope of the appended claims; however, the invention should be more fully understood, in both its composition and content, together with its other objects and features, by referring to the following detailed description of the accompanying drawings. Attached Figure Description

[0016] Figure 1 This is a front view obtained by making a cross-section of a portion of the lithium primary battery according to an embodiment of this application. Detailed Implementation

[0017] The following describes embodiments of this application by way of example; however, this application is not limited to the examples described below. In the following description, specific values ​​and materials are sometimes shown; however, other values ​​and materials can be applied as long as the effects of this application are achieved. In this specification, the phrase "value A to value B" includes both value A and value B, and can be changed to "value A or above and value B or below". In the following description, when lower and upper limits of values ​​relating to specific physical properties, conditions, etc., are shown, any of the shown lower limits and any of the shown upper limits can be arbitrarily combined, as long as the lower limit is not above the upper limit. When multiple materials are shown, one can be selected and used alone, or two or more can be used in combination.

[0018] The lithium primary battery of this application includes a positive electrode, a negative electrode, and a non-aqueous electrolyte. The positive electrode contains manganese dioxide. The negative electrode includes a first lithium layer and an aluminum layer (Al layer) stacked on the first lithium layer. The first lithium layer is an alloy layer containing lithium (Li) and magnesium (Mg). The Li content in the alloy layer is 89% by mass or more and 99.98% by mass or less, and the Mg content in the alloy layer is 0.02% by mass or more and 1.5% by mass or less. It should be noted that the above-described negative electrode is the negative electrode of the battery in its undischarged state (before use).

[0019] Hereinafter, alloys containing Li and Mg but substantially not containing Al will also be referred to as "Li-Mg alloys". Lithium alloys containing Li, Mg and Al will also be referred to as "Li-Mg-Al alloys". It should be noted that "substantially not containing Al" means that the Al content in the composition analysis of lithium alloys (such as ICP emission spectrophotometry, atomic absorption spectrometry, etc.) is less than the detection limit.

[0020] Because the alloy layer contains Mg, the strength of the negative electrode increases, and the breakage of the negative electrode at the end of the discharge (including local defects) is suppressed, thus suppressing the reduction in discharge characteristics caused by the decrease in strength.

[0021] On the other hand, Mg can exist in the alloy layer as a large solid solution (Mg block). The disordered arrangement of Li atoms around the Mg block causes electrons to travel along distorted paths, resulting in electron scattering, increased electrical resistance, and reduced discharge characteristics.

[0022] In contrast, in this application, an Al layer is stacked on top of an alloy layer containing Li and Mg. Therefore, during discharge, Al in the Al layer diffuses into the alloy layer and can alloy with Mg in the alloy layer. The Mg mass becomes smaller due to the presence of Al, the dispersion of Mg is improved, and the decrease in discharge characteristics (e.g., low-temperature pulsed discharge characteristics) caused by the increased resistance due to the disordered arrangement of Li atoms is suppressed.

[0023] However, when the Mg content is less than 0.02% by mass, the effect of Mg on increasing the strength of the negative electrode becomes smaller, and the discharge characteristics at the end of the discharge phase decrease. When the Mg content is greater than 1.5% by mass, the influence caused by the Mg block becomes larger, and even with an Al layer, it is difficult to suppress the disordered arrangement of Li atoms, resulting in decreased discharge characteristics. When the Li content in the alloy layer is less than 89% by mass, the amount of Li in the negative electrode (absolute Li amount) decreases, leading to decreased discharge characteristics.

[0024] (1st lithium layer)

[0025] The first lithium layer is an alloy layer comprising Li and Mg. The thickness of the first lithium layer is, for example, 50 to 400 μm. From the viewpoint of suppressing the breakage of the negative electrode at the end of discharge, the Mg content in the alloy layer is 0.02% by mass or more, preferably 0.1% by mass or more, and more preferably 0.5% by mass or more. From the viewpoint of suppressing the formation of Mg blocks and ensuring the amount of Li, the Mg content in the alloy layer is 1.5% by mass or less, preferably 1.0% by mass or less. The range of Mg content in the alloy layer can be, for example, 0.1% by mass or more and 1.5% by mass or less, or 0.5% by mass or more and 1.0% by mass or less.

[0026] From the perspective of ensuring sufficient Li content, the Li content in the alloy layer is 89% by mass or more, or it can be 90% by mass or more, or 95% by mass or more. Since the alloy layer contains 0.02% by mass or more of Mg, the Li content in the alloy layer is 99.98% by mass or less.

[0027] The alloy layer may contain metallic elements other than Li and Mg, with a Li content of not less than 89% by mass. Examples of such metallic elements include Al, Sn, Ni, Pb, In, and K.

[0028] Preferably, the alloy layer contains Al as a metallic element other than Li and Mg. The combined content of Mg and Al in the alloy layer is preferably greater than 0.02% by mass and less than 11% by mass, more preferably more than 0.1% by mass and less than 7% by mass, and even more preferably more than 0.5% by mass and less than 2% by mass. In this case, compared to Al contained in the Al layer, the diffusion path of Al contained in the alloy layer to the vicinity of Mg in the alloy layer is shorter, the energy loss due to diffusion is smaller, and the dispersion of Mg is easier to improve. It should be noted that the Al in the alloy layer mentioned here refers to the Al pre-contained in the alloy layer during the fabrication of the negative electrode, excluding Al from the aluminum layer.

[0029] The Al content in the alloy layer can be 0.01% by mass or more and 8% by mass or less, preferably 0.01% by mass or more (or 0.1% by mass or more) and 5% by mass or less, more preferably 0.01% by mass or more (or 0.1% by mass or more) and 0.5% by mass or less. The mass ratio of Mg to Al in the alloy layer is, for example, Mg:Al = 100:5 to 50.

[0030] (Aluminum layer)

[0031] In the negative electrode, an aluminum layer (Al layer) is stacked on top of an alloy layer (first lithium layer). In this case, compared to the case where the alloy layer contains Al, it is easier and more efficient to obtain the improved dispersion of Mg due to Al on the surface of the alloy layer. In addition, the first lithium layer and the aluminum layer are electrochemically alloyed to form a Li-Al alloy, which is micronized, thereby increasing the surface area of ​​the negative electrode.

[0032] An Al layer is a layer containing at least Al. It can be an Al metal layer containing only Al, or an alloy layer containing Al and other metals besides Al (such as Cu, Fe, Si, Mn, Zn, etc.). From the viewpoint of promoting the alloying of Li and Al, it is desirable that the content of other metals besides Al in the Al layer is low. The Al content in the Al layer can be, for example, 99% by mass or more, or even 100% by mass. The thickness of the Al layer is, for example, 3–15 μm.

[0033] (2nd lithium layer)

[0034] The negative electrode may have a second lithium layer disposed between the first lithium layer and the aluminum layer. In this case, the aluminum layer is stacked on top of the first lithium layer with the second lithium layer in between. The second lithium layer preferably does not contain Mg. In this case, it is easier to alloy Li with Al compared to the case where the aluminum layer is directly stacked on the first lithium layer containing Mg. The second lithium layer is a layer containing at least Li, which may be a Li metal layer containing only Li, or an alloy layer containing Li and other metals other than Li (e.g., Sn, Ni, Pb, In, K, etc.). From the viewpoint of promoting the alloying of Li and Al, it is desirable that the content of other metals besides Li in the second lithium layer is low. The Li content in the second lithium layer may be, for example, 95% by mass or more, 98% by mass or more, or 100% by mass. The thickness of the second lithium layer is, for example, 30 to 100 μm.

[0035] The composition of the layers that constitute the negative electrode, such as the first lithium layer, can be determined using inductively coupled plasma (ICP) luminescence spectrophotometry or atomic absorption spectrometry (AAS).

[0036] The lithium primary battery of this application will be described in more detail below.

[0037] (positive electrode)

[0038] The positive electrode contains manganese dioxide as the positive electrode active material. In batteries with a positive electrode containing manganese dioxide, high-rate discharge is possible even at low temperatures, resulting in excellent low-temperature pulse discharge characteristics. Conversely, if the positive electrode active material is fluorinated graphite, pulse discharge characteristics cannot be achieved at extremely low temperatures of -40°C due to the increased viscosity of the non-aqueous electrolyte.

[0039] Electrolytic manganese dioxide can be used as manganese dioxide. Manganese dioxide can be in a mixed crystal state containing multiple crystalline states. The positive electrode can contain manganese oxides other than manganese dioxide. Examples of manganese oxides other than manganese dioxide include MnO, Mn3O4, Mn2O3, and Mn2O7. Preferably, the main component of the manganese oxide in the positive electrode is manganese dioxide. Here, "main component" means that manganese dioxide accounts for 50% or more of the manganese oxide. The proportion of manganese dioxide in the manganese oxide can also be 70% or more, or 90% or more.

[0040] The positive electrode may contain a positive electrode compound including a positive electrode active material, a binder, and a conductive agent. Examples of binders include fluoropolymers 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 fiber.

[0041] The positive electrode may further include a positive current collector that retains the positive electrode binder. Examples of materials that can be used as the positive current collector include stainless steel, aluminum, and titanium.

[0042] In the case of a coin-shaped battery, the positive electrode can be formed by mounting an L-shaped annular positive current collector onto positive electrode particles, or the positive electrode can be formed using only positive electrode particles. For example, a moistened positive electrode mixture prepared by adding an appropriate amount of water to a positive electrode active material is compressed and dried to obtain positive electrode particles.

[0043] In the case of a cylindrical battery, a positive electrode comprising a sheet-like positive current collector and a positive electrode flux layer held by the positive current collector can be used. As the sheet-like positive current collector, a porous current collector is preferred. Examples of porous current collectors include stretched metal, mesh, and perforated metal. For example, the aforementioned wet positive electrode flux is coated onto the surface of the sheet-like positive current collector or filled into the positive current collector, pressurized along the thickness direction, and dried to obtain the positive electrode flux layer.

[0044] (negative electrode)

[0045] The negative electrode comprises a stack of a first lithium layer and an aluminum layer (or a stack of a first lithium layer, a second lithium layer, and an aluminum layer). For example, a foil or sheet substrate is used in the formation of each layer. The substrate is shaped into any shape and thickness according to the shape, size, specifications, and performance characteristics of the lithium primary battery.

[0046] The negative electrode can have a negative electrode current collector (e.g., copper foil) supporting a laminate. However, since the first lithium layer contains Mg, and there is a high residual Mg intensity at the end of discharge, the negative electrode can be constructed using only the laminate without using a negative electrode current collector. High energy density can be achieved by not using a negative electrode current collector. Because the first lithium layer contains Mg, the breakage of the negative electrode at the end of discharge is suppressed, and the Li in the negative electrode can be effectively utilized without any residue.

[0047] In the case of a coin-shaped battery, for example, an Al-containing foil can be pressed onto a disc-shaped Li-Mg alloy (or Li-Mg-Al alloy) to form the negative electrode. In the case of a cylindrical battery, for example, an Al-containing foil can be pressed onto a Li-Mg alloy foil (or Li-Mg-Al alloy foil) to form the negative electrode.

[0048] (Non-aqueous electrolyte)

[0049] Non-aqueous electrolytes may contain, for example, non-aqueous solvents and lithium salts. The concentration of lithium ions (total concentration of lithium salts) in the non-aqueous electrolyte may be, for example, 0.2 mol / L or more and 2.0 mol / L or less, or 0.3 mol / L or more and 1.5 mol / L or less.

[0050] Examples of non-aqueous solvents commonly used in non-aqueous electrolytes for primary lithium batteries include ethers, esters, and carbonates. Other non-aqueous solvents include dimethyl ether, γ-butyrolactone, propylene carbonate (PC), ethylene carbonate (EC), dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, 1,2-dimethoxyethane (DME), 1,2-diethoxyethane, methyl acetate, ethyl acetate, and propyl acetate. Non-aqueous electrolytes may contain one or more non-aqueous solvents.

[0051] From the viewpoint of improving the discharge characteristics of lithium primary batteries, the non-aqueous solvent preferably comprises a cyclic carbonate with a high boiling point and a linear ether with low viscosity at low temperatures. The cyclic carbonate preferably comprises at least one selected from PC and EC, with PC being particularly preferred. The linear ether preferably comprises DME.

[0052] Examples of lithium salts include those used as solutes in primary lithium batteries. Examples of such lithium salts include LiCF3SO3, LiClO4, LiBF4, LiPF6, LiRaSO3 (Ra is a fluoroalkyl group with 1 to 4 carbon atoms), LiFSO3, LiN(SO2Rb)(SO2Rc) (Rb and Rc are each independently a fluoroalkyl group with 1 to 4 carbon atoms), LiN(FSO2)2, LiN(SO2CF3)2, LiN(SO2F)(POF2), LiPO2F2, LiB(C2O4)2, and LiBF2(C2O4). From the viewpoint of stability relative to lithium alloys containing Mg, at least one of LiCF3SO3, LiBF4, and LiN(FSO2)2 is preferred. The non-aqueous electrolyte may contain one or more of these lithium salts.

[0053] Non-aqueous electrolytes may further contain additives and other components. Examples of such components include propane sulpholactone, allyl sulpholactone, ethylene sulfite, 3,2-dioxane-2,2-dioxide, vinylene carbonate, ethylene ethylene carbonate, fluoroethylene carbonate, adiponitrile, succinic anhydride, etc. Other components may be lithium salts or components capable of generating lithium ions.

[0054] (spacer)

[0055] Lithium-ion primary batteries typically have a spacer sandwiched between the positive and negative electrodes. As a spacer, a porous sheet made of an insulating material that is resistant to the internal environment of the lithium-ion primary battery can be used. Specifically, examples include nonwoven fabrics made of synthetic resin, microporous membranes made of synthetic resin, or laminates thereof.

[0056] 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 copolymer. Microporous membranes may also contain inorganic particles as needed.

[0057] The thickness of the spacer is, for example, 5 μm or more and 100 μm or less.

[0058] There are no particular limitations on the structure of a primary lithium battery. A primary lithium battery can be a coin-shaped battery with a stacked electrode assembly consisting of a circular positive electrode and a circular negative electrode separated by a spacer. It can also be a cylindrical battery with a wound electrode assembly consisting of a strip-shaped positive electrode and a strip-shaped negative electrode separated by a spacer wound into a spiral shape.

[0059] Figure 1 The image shows a front view of a portion of a lithium primary battery according to one embodiment of this application, in cross-section. The lithium primary battery 10 houses an electrode assembly, consisting of a positive electrode 1 and a negative electrode 2 wound together with a spacer 3, along with a non-aqueous electrolyte (not shown), within a battery casing 9. A sealing plate 8 is installed at the opening of the battery casing 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 casing 9. Furthermore, an upper insulating plate 6 and a lower insulating plate 7 are respectively provided at the upper and lower parts of the electrode assembly to prevent internal short circuits.

[0060] Postscript

[0061] The following technology is disclosed through the description of the above embodiments.

[0062] (Technology 1)

[0063] A primary lithium battery comprising a positive electrode, a negative electrode, and a non-aqueous electrolyte.

[0064] The aforementioned positive electrode contains manganese dioxide.

[0065] The aforementioned negative electrode comprises a first lithium layer and an aluminum layer stacked on the first lithium layer.

[0066] The first lithium layer mentioned above is an alloy layer containing lithium and magnesium.

[0067] The lithium content in the aforementioned alloy layer is 89% by mass or more and 99.98% by mass or less.

[0068] The magnesium content in the alloy layer is 0.02% by mass or more and 1.5% by mass or less.

[0069] (Technology 2)

[0070] According to the lithium primary battery described in Technology 1, the aforementioned alloy layer comprises aluminum.

[0071] The total content of the magnesium and aluminum in the alloy layer is greater than 0.02% by mass and less than 11% by mass.

[0072] (Technology 3)

[0073] According to the lithium primary battery described in Technology 2, the aluminum content in the lithium alloy layer is 0.01% by mass or more and 0.5% by mass or less.

[0074] (Technology 4)

[0075] According to any one of the technologies 1 to 3, a primary lithium battery is provided, wherein the negative electrode includes a second lithium layer disposed between the first lithium layer and the aluminum layer.

[0076] [Example]

[0077] The present application will now be described in detail based on the embodiments and comparative examples; however, the present application is not limited to the following embodiments.

[0078] Examples 1-4 and Comparative Examples 1-3

[0079] (The production of the positive electrode)

[0080] To 100 parts by mass of electrolytic manganese dioxide (MnO2) used as the positive electrode active material, 5 parts by mass of Ketjen black used as a conductive agent, 5 parts by mass of polytetrafluoroethylene used as a binder, and an appropriate amount of pure water are added and mixed to prepare a wet positive electrode mixture.

[0081] Next, the positive electrode filler is filled into a positive electrode current collector made of 0.1mm thick stainless steel (SUS444) mesh metal to create the positive electrode precursor. The positive electrode precursor is then dried, rolled using a roller press, and cut into dimensions of 3.5cm in length and 20cm in width to obtain the positive electrode. Next, a portion of the filled positive electrode filler is peeled off, and one end of the SUS444 positive electrode lead is resistance-welded to the exposed portion of the positive electrode current collector.

[0082] (Making the negative electrode)

[0083] An Al metal foil (200 mm long, 35 mm wide, 7 μm thick) was laminated onto a Li-Mg alloy foil (200 mm long, 37 mm wide, 220 μm thick) and then crimped. This yielded a negative electrode consisting of a Li-Mg alloy layer (first lithium layer) and an Al metal layer laminate. A nickel negative electrode lead was crimped to a specified location on the negative electrode. The Mg content in the Li-Mg alloy foil was set to the values ​​shown in Table 1. The alloy foil contained only Li, excluding Mg. The composition of the lithium alloy was determined using ICP-N (Inductively Coupled Plasma) emission spectrophotometry or atomic absorption spectrometry. It should be noted that "0% by mass" for Mg content indicates that Mg could not be detected using ICP-N or atomic absorption spectrometry.

[0084] (Fabrication of the electrode assembly)

[0085] The electrode assembly is fabricated by winding the positive and negative electrodes together with a spacer in between. The spacer is a microporous membrane made of polypropylene with a thickness of 25 μm.

[0086] (Preparation of non-aqueous electrolyte)

[0087] A non-aqueous electrolyte was prepared by dissolving LiCF3SO3 at a concentration of 0.5 mol / L in a mixed solvent of PC, EC and DME (volume ratio 3:2:5).

[0088] (Assembly of primary lithium batteries)

[0089] The electrode assembly is housed in a cylindrical battery casing that also serves as the negative terminal. The battery casing is made of iron (outer diameter 17 mm, height 45.5 mm). After injecting a non-aqueous electrolyte into the battery casing, the opening of the battery casing is sealed using a metal sealing plate that also serves as the positive terminal. The other end of the positive electrode lead is connected to the sealing plate, and the other end of the negative electrode lead is connected to the inner bottom surface of the battery casing. A primary lithium battery is thus manufactured. It should be noted that A1 to A4 in Table 1 are batteries from Examples 1 to 4, and B1 to B3 are batteries from Comparative Examples 1 to 3.

[0090] Comparative Example 4

[0091] Except that Li-Mg alloy foil was used as the negative electrode instead of Al foil, the battery B4 of Comparative Example 4 was made in the same manner as battery A2 of Example 2.

[0092] The batteries of the obtained examples and comparative examples were aged for 7 days at 45°C after assembly, and the following evaluations were performed.

[0093] [evaluate]

[0094] The aged battery was discharged at a constant current of 2.5mA at 20°C until the depth of discharge (DOD) reached 90% (the discharge capacity reached 90% of the rated capacity). Then, the battery with 90% DOD was subjected to a 1-second pulse discharge at 300mA at -40°C, and the lowest voltage at this point was determined.

[0095] The evaluation results are shown in Table 1.

[0096] [Table 1]

[0097]

[0098] Among batteries A1 to A4, the lowest voltage during low-temperature pulse discharge is high, resulting in excellent low-temperature pulse discharge characteristics.

[0099] In batteries B1 and B2, where the Mg content in the Li-Mg alloy foil is less than 0.02% by mass, and in battery B3, where the Mg content in the Li-Mg alloy foil is greater than 1.5% by mass, the low-temperature pulse discharge characteristics are reduced. In battery B4, the low-temperature pulse discharge characteristics are reduced because Al metal foil is not used in the fabrication of the negative electrode.

[0100] Examples 5-15 and Comparative Examples 5-8

[0101] In the fabrication of the negative electrode, a Li-Mg-Al alloy foil (200 mm in length, 37 mm in width, and 220 μm in thickness) was used instead of a Li-Mg alloy foil, resulting in a negative electrode composed of a Li-Mg-Al alloy layer (first lithium layer) and an Al metal layer. The Mg and Al contents in the Li-Mg-Al alloy foil were set to the values ​​shown in Tables 2 and 3, respectively. In the alloy foil, Li was present in addition to Mg and Al. Except as described above, batteries A5 to A15 of Examples 5 to 15 and batteries B5 to B8 of Comparative Examples 5 to 8 were fabricated and evaluated in the same manner as battery A1 of Example 1. The evaluation results are shown in Tables 2 and 3.

[0102] [Table 2]

[0103]

[0104] [Table 3]

[0105]

[0106] Excellent low-temperature pulse discharge characteristics were obtained in batteries A5 to A15. In battery B5, where the combined Mg and Al content in the Li-Mg-Al alloy foil is greater than 11% by mass, the low-temperature pulse discharge characteristics decreased due to the Li content being less than 89% by mass. Low-temperature pulse discharge characteristics also decreased in batteries B6 and B7, where the Mg content in the alloy foil is less than 0.02% by mass, and in battery B8, where the Mg content in the alloy foil is greater than 1.5% by mass.

[0107] Example 16

[0108] In the fabrication of the negative electrode, Li metal foil (200 mm long, 37 mm wide, 170 μm thick) and Al metal foil (200 mm long, 35 mm wide, 7 μm thick) were sequentially stacked and pressed together. This resulted in a negative electrode composed of a Li-Mg alloy layer, a Li metal layer, and an Al metal layer. The Mg content in the Li-Mg alloy foil was set to 0.5% by mass. Battery A16 was fabricated and evaluated in the same manner as battery A1, except as described above.

[0109] Example 17

[0110] In the fabrication of the negative electrode, Li foil (200 mm long, 37 mm wide, 170 μm thick) and Al foil (200 mm long, 35 mm wide, 7 μm thick) were sequentially stacked and pressed together. This resulted in a negative electrode composed of a Li-Mg-Al alloy layer, a Li metal layer, and an Al metal layer. The Mg content and Al content in the Li-Mg-Al alloy foil were set to 0.5% by mass and 0.2% by mass, respectively. Battery A17 was fabricated and evaluated in the same manner as battery A1, except as described above.

[0111] The evaluation results are shown in Table 4.

[0112] [Table 4]

[0113]

[0114] Excellent low-temperature pulse discharge characteristics were also obtained in batteries A16 and A17.

[0115] Industrial availability

[0116] The lithium primary battery of this application can be used as a main power source for various instruments (such as smart meters for electricity, tap water, gas, etc.) or as a backup power source for memory.

[0117] While the invention has been described with respect to preferred embodiments, such disclosure should not be interpreted as restrictive. Various modifications and alterations will be readily apparent to those skilled in the art upon reading the foregoing disclosure. Therefore, the scope of the appended claims should be interpreted as encompassing all modifications and alterations without departing from the true spirit and scope of the invention.

[0118] Explanation of reference numerals in the attached figures

[0119] 1 Positive electrode, 1a Positive current collector, 2 Negative electrode, 3 Spacer, 4 Positive lead, 5 Negative lead, 6 Upper insulating plate, 7 Lower insulating plate, 8 Sealing plate, 9 Battery casing, 10 Primary lithium battery.

Claims

1. A primary lithium battery comprising a positive electrode, a negative electrode, and a non-aqueous electrolyte. The positive electrode contains manganese dioxide. The negative electrode comprises a first lithium layer and an aluminum layer stacked on the first lithium layer. The first lithium layer is an alloy layer containing lithium and magnesium. The lithium content in the alloy layer is 89% by mass or more and 99.98% by mass or less. The magnesium content in the alloy layer is more than 0.02% by mass and less than 1.5% by mass.

2. The lithium primary battery according to claim 1, wherein, The alloy layer contains aluminum. The total content of magnesium and aluminum in the alloy layer is greater than 0.02% by mass and less than 11% by mass.

3. The lithium primary battery according to claim 2, wherein, The aluminum content in the alloy layer is more than 0.01% by mass and less than 0.5% by mass.

4. The lithium primary battery according to claim 1, wherein, The negative electrode has a second lithium layer disposed between the first lithium layer and the aluminum layer.

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