Battery cell, secondary battery, and electric device

Abstract

The application provides a battery cell, a secondary battery and an electric device. The battery cell comprises a plurality of positive electrode units and negative electrode units arranged in sequence and a separator between the positive electrode units and the negative electrode units, the positive electrode unit comprises a positive electrode current collector and a non-sodium-supplemented positive electrode active layer and a sodium-supplemented positive electrode active layer arranged on both sides of the positive electrode current collector, the negative electrode unit comprises a negative electrode current collector, a first negative electrode sheet and a second negative electrode sheet arranged on both sides of the negative electrode current collector and a negative electrode sodium-supplemented layer, the negative electrode sodium-supplemented layer is arranged on the side of the first negative electrode sheet away from the negative electrode current collector, the negative electrode sodium-supplemented layer is arranged towards the non-sodium-supplemented positive electrode active layer in the positive electrode unit, and the sodium-supplemented positive electrode active layer is arranged towards the second negative electrode sheet in the negative electrode unit. The sodium-supplemented mode improves the overall performance of the battery cell and the battery.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of batteries, in particular to an electrode, a secondary battery and an electric device. BACKGROUND

[0002] The abundant reserves of sodium make sodium-ion batteries an environmentally friendly and relatively low-cost battery technology. Sodium supplementation is considered a key technology to improve the energy density and life of the battery. By supplementing sodium, the active sodium consumption of the first film formation of the negative electrode can be compensated for, significantly improving the energy density of the battery. At the same time, due to the presence of excess active sodium in the negative electrode, the continuous loss of active sodium during the cycle process can be compensated for, thereby effectively improving the cycle and storage life of the battery.

[0003] Although the positive electrode sodium supplement is simple to operate and has high compatibility with the current production line, due to the low specific capacity (about 200-400 mAh / g) of sodium chromate (NaCrO2), sodium nickelate (Na2NiO2), sodium oxalate (Na2C2O4) and other positive electrode sodium supplement materials, and the obvious gas production during decomposition and subsequent cycle process. For the hard carbon system with low first efficiency and high specific capacity, the conventional positive electrode sodium supplement method needs to add a higher proportion (generally more than 5%) of sodium supplement to compensate for the active sodium consumed by the first film formation, and the negative electrode basically has no pre-stored sodium. Therefore, simply supplementing sodium in the positive electrode cannot effectively supplement sodium for the hard carbon negative electrode system and improve the cycle life of the hard carbon negative electrode, and due to the large number of added parts, it brings problems of residual sodium supplement and gas production. Although the negative electrode sodium powder and sodium foil supplement sodium have high sodium supplement specific capacity (the specific capacity of metallic sodium is as high as 1166 mAh / g) and adjustable sodium supplement surface density, they can be applied to various systems such as soft carbon, hard carbon and graphite, but the process of negative electrode sodium supplement is complex and has high safety risks. When double-sided negative electrode sodium supplement is performed on the carbon negative electrode, due to the solid-phase insertion of sodium, the pole piece becomes brittle and hard and generates obvious heat, the flatness of the pole piece is poor, and as the amount of sodium supplement increases, this problem becomes more serious, which brings serious challenges to the safe flow of the pole piece and the subsequent process. Therefore, the conventional pre-sodium technology has the obvious shortcomings of limited application range and difficulty in mass production. SUMMARY

[0004] The present application aims to at least partially solve one of the problems in the related art. To this end, one object of the present application is to provide an electrode which can effectively meet the sodium supplement demand and has a long service life.

[0005] In one aspect of the present application, the present application provides an electric core. According to an embodiment of the present application, the electric core comprises a plurality of positive electrode units and negative electrode units arranged in sequence and a separator between the positive electrode units and the negative electrode units, the positive electrode unit comprises a positive electrode current collector and a non-sodium-supplemented positive electrode active layer and a sodium-supplemented positive electrode active layer arranged on both sides of the positive electrode current collector respectively, the negative electrode unit comprises a negative electrode current collector, a first negative electrode sheet and a second negative electrode sheet arranged on both sides of the negative electrode current collector respectively, and a negative electrode sodium-supplemented layer, the negative electrode sodium-supplemented layer is located on the side of the first negative electrode sheet away from the negative electrode current collector, wherein the negative electrode sodium-supplemented layer is arranged towards the non-sodium-supplemented positive electrode active layer in the positive electrode unit, and the sodium-supplemented positive electrode active layer is arranged towards the second negative electrode sheet in the negative electrode unit. In the electric core with the above structure, only one side of the positive electrode unit and the negative electrode unit is provided with sodium-supplemented material, and the side of the first negative electrode sheet with the negative electrode sodium-supplemented layer corresponds to the side of the non-sodium-supplemented positive electrode active layer, and the side of the second negative electrode sheet without the sodium-supplemented layer corresponds to the side of the sodium-supplemented positive electrode active layer to be laminated or wound to form a sodium-supplemented electric core. The above sodium-supplementing method overcomes the problems of low sodium-supplementing capacity and large amount of addition when supplementing sodium on both sides of the positive electrode alone, and the same amount of sodium supplementing agent can be achieved when supplementing sodium on one side of the positive electrode, and only half of the mass of the positive electrode active layer is supplemented with sodium, so that the proportion of the sodium supplementing agent can be increased under the condition of unchanged mass, higher sodium supplementing demand can be achieved, the active sodium consumed by the first film formation of the negative electrode is compensated, and the cycle life of the battery is improved due to the presence of additional active sodium in the negative electrode. At the same time, the disadvantages of obvious heating of the negative electrode sheet, poor flatness of the negative electrode sheet, and brittleness of the negative electrode sheet leading to unquantifiable production after supplementing sodium on both sides of the negative electrode can be overcome. Therefore, the above positive and negative electrode sodium supplementing method of the present application fully utilizes the advantages of positive and negative electrode sodium supplementing and can be mass-produced, which has practical significance for the realization of high-energy-density long-life batteries.

[0006] According to an embodiment of the present application, only one layer of sodium-supplementing structure is included between the adjacent two positive electrode current collectors and the negative electrode current collector, and the sodium-supplementing structure is the sodium-supplemented positive electrode active layer or the negative electrode sodium-supplemented layer.

[0007] According to an embodiment of the present application, the sodium supplementing agent in the sodium-supplemented positive electrode active layer comprises at least one of Na2NiO2, NaC r O2, Na2C2O4, Na3N, Na2S, Na3P, Na2CO3, NaNO2, Na2C4O4, Na2C6O6, and Na2C6H2O6, and the negative electrode sodium-supplemented layer is a sodium foil and / or a sodium powder.

[0008] According to an embodiment of the present application, the content of the sodium supplementing agent in the sodium-supplemented positive electrode active layer is less than or equal to 40% in terms of mass percentage based on the total mass of the non-sodium-supplemented positive electrode active layer and the sodium-supplemented positive electrode active layer.

[0009] According to an embodiment of the present application, the content of the sodium supplement agent in the sodium supplement positive active layer is 1.5-10% by mass percentage, relative to the total mass of the non-sodium-supplement positive active layer and the sodium supplement positive active layer.

[0010] According to an embodiment of the present application, the surface density of the sodium supplement agent is 1 g / m 2 2-18 g / m 2 .

[0011] According to an embodiment of the present application, the surface density of the sodium supplement agent is 4 g / m 2 2-16 g / m 2 .

[0012] According to an embodiment of the present application, the surface density of the negative electrode sodium supplement layer is 0.5 g / m 2 2-10 g / m 2 .

[0013] According to an embodiment of the present application, the surface density of the negative electrode sodium supplement layer is 1 g / m 2 2-6 g / m 2 .

[0014] According to an embodiment of the present application, the effective active substance in the non-sodium-supplement positive active layer and the sodium supplement positive active layer is at least one of transition metal oxide Na e M02, Prussian blue compound Na f M1[M2(CN)6] and polyanion compound Na d M g (X a O b ) c Z h , wherein M, M1 and M2 are one or more of transition metal atoms, X is one or more of Si, S, P, As, B, Mo, W and Ge, and Z is one or more of F and OH; and the effective active substance of the first negative electrode sheet and the second negative electrode sheet is at least one of natural graphite, artificial graphite, soft carbon, hard carbon, mesocarbon microbead, nano-carbon, carbon fiber, silicon negative electrode material and sodium-embedded alloy.

[0015] In another aspect of the present application, the present application provides a secondary battery. According to an embodiment of the present application, the secondary battery comprises the above-mentioned battery cell. Therefore, the service life of the secondary battery is longer. Those skilled in the art can understand that the electric device has all the features and advantages of the above-mentioned battery cell, which will not be described in detail here.

[0016] In still another aspect of the present application, the present application provides a power consuming device. According to an embodiment of the present application, the power consuming device includes the secondary battery as described above. Thus, the power consuming device has a long service life. Those skilled in the art will understand that the power consuming device has all the features and advantages of the secondary battery as described above, and thus will not be described in more detail here. BRIEF DESCRIPTION OF DRAWINGS

[0017] The above and / or additional aspects and advantages of the present application will become apparent and more readily appreciated from the following description of embodiments, taken in conjunction with the accompanying drawings in which:

[0018] Figure 1 is a structural schematic diagram of an electric cell in one embodiment of the present application. DETAILED DESCRIPTION

[0019] The scheme of the present application will be explained below with reference to the embodiments. Those skilled in the art will understand that the following embodiments are only for illustrating the present application, and should not be considered as limiting the scope of the present application. In the embodiments, the specific techniques or conditions not mentioned are performed according to the techniques or conditions described in the literature in the art or according to the product manual. The reagents or instruments not mentioned are all the conventional products available in the market.

[0020] The present application will be described below with reference to specific embodiments, and it should be noted that these embodiments are merely illustrative, and should not be considered as limiting the present application in any way.

[0021] In one aspect of the present application, the present application provides a secondary battery. According to an embodiment of the present application, the secondary battery includes a cathode, an anode, and an electrolyte. The cathode includes a cathode active material, a cathode binder, and a cathode conductive agent. The anode includes an anode active material, an anode binder, and an anode conductive agent. The electrolyte includes an electrolyte solvent, an electrolyte salt, and an electrolyte additive. Thus, the secondary battery has a long service life. Figure 1The secondary battery comprises a plurality of positive electrode units 10 and negative electrode units 20 arranged in sequence and a diaphragm 30 between the positive electrode units 10 and the negative electrode units 20, the positive electrode unit 10 comprises a positive electrode current collector 13 and a non-sodium-supplemented positive electrode active layer 12 and a sodium-supplemented positive electrode active layer 11 arranged on both sides of the positive electrode current collector 13 respectively, the negative electrode unit 20 comprises a negative electrode current collector 23, a first negative electrode sheet 21 and a second negative electrode sheet 22 arranged on both sides of the negative electrode current collector 23 respectively and a negative electrode sodium-supplemented layer 24, the negative electrode sodium-supplemented layer 24 is located on the side of the first negative electrode sheet 21 away from the negative electrode current collector 23, wherein, in the laminated structure of the positive electrode unit and the negative electrode unit, the negative electrode sodium-supplemented layer 24 is arranged on the side of the non-sodium-supplemented positive electrode active layer 12 in the positive electrode unit 10, and the sodium-supplemented positive electrode active layer 11 is arranged on the side of the second negative electrode sheet 22 in the negative electrode unit 20, that is, only one side of the positive electrode unit and the negative electrode unit is provided with a sodium-supplemented material, the sodium-supplemented positive electrode active layer 11 in the positive electrode unit 10 is arranged opposite to the negative electrode sodium-supplemented layer 24 in the negative electrode unit 20, or in other words, the side of the first negative electrode sheet 21 with the negative electrode sodium-supplemented layer 24 corresponds to the side of the non-sodium-supplemented positive electrode active layer 12, and the side of the second negative electrode sheet 22 without the negative electrode sodium-supplemented layer 24 corresponds to the side of the sodium-supplemented positive electrode active layer 11, and the laminated or wound to form a sodium-supplemented secondary battery.

[0022] According to the embodiments of the present application, referring to Figure 1 , only one layer of sodium-supplemented structure is included between the two adjacent positive electrode current collectors 13 and negative electrode current collectors 23, and the sodium-supplemented structure is the sodium-supplemented positive electrode active layer 11 or the negative electrode sodium-supplemented layer 24.

[0023] As understood by those skilled in the art, the non-sodium-supplemented positive electrode active layer 12 means that the positive electrode active layer does not contain a sodium-supplementing agent, and the sodium-supplemented positive electrode active layer 11 means that the positive electrode active layer contains a sodium-supplementing agent; in the negative electrode unit, the negative electrode sodium-supplemented layer is arranged on the side of the first negative electrode sheet arranged on the negative electrode current collector, and the negative electrode sodium-supplemented layer is not arranged on the side of the second negative electrode sheet.

[0024] According to the embodiments of the present application, the above-mentioned sodium-supplemented structure has at least the following technical effects:

[0025] First, the design of sodium supplement on both sides of the positive active material layer, this positive active material layer unilateral sodium supplement, can realize greater sodium supplement dosage ratio without affecting other performances (such as energy density, gas production and other electrochemical performances) under the premise of not affecting other performances (such as energy density, gas production and other electrochemical performances), thereby widening the application of the positive electrode sodium supplement scheme. Because of the limited specific capacity of the positive electrode sodium supplement agent (the sodium supplement specific capacity of Na2NiO2 is about 386 mAh / g, the sodium supplement specific capacity of Na2CrO2 is about 230 mAh / g, and the sodium supplement specific capacity of Na2C2O4 is about 380 mAh / g), the conventional positive active material double-side sodium supplement is generally used in combination with high first-effect negative electrodes such as graphite, which limits its application in high specific capacity and low first-effect negative electrode materials (such as hard carbon). In the present application, the positive active material is supplemented with sodium on one side, so the proportion of the sodium supplement agent in the single-side active material is increased, thereby the sodium supplement design can be realized in combination with various negative electrode systems such as hard carbon, silicon-carbon and sodium-embedded alloy. At the same time, due to the single-side sodium supplement, the gas production during the battery cycle process can be significantly reduced.

[0026] Second, the negative electrode active material is supplemented with metal sodium on both sides. Due to the high activity of metal sodium, the negative electrode sheet will have obvious heating phenomenon after pre-sodium. The heating of the negative electrode sheet after pre-sodium (i.e. sodium supplement) leads to safety risks. In addition, the surface density difference between the two sides of the pre-sodium is usually large, which not only may cause the actual negative electrode sheet state to be inconsistent with the theoretical design, leading to possible surface density unevenness, sodium precipitation and other adverse risks, but also leads to the unevenness of the negative electrode sheet due to the inconsistent sodium-embedded expansion stress, thereby bringing risks to the later assembly. Moreover, the accumulation of the sodium-embedded expansion stress of the high pre-sodium negative electrode sheet will lead to the brittleness and hardness of the electrode sheet, which also brings great challenges to the later die cutting assembly. The pre-sodium of the negative electrode current collector single-side active material in the present application can significantly reduce the heating phenomenon of the negative electrode sheet after pre-sodium (compared with the double-side sodium supplement of the negative electrode sheet), avoid the inconsistency of the surface density of the double-side pre-sodium, improve the consistency of the surface density of the negative electrode sodium supplement layer, and obviously alleviate the brittleness and hardness of the negative electrode sheet due to the pre-sodium on one side, thereby significantly reducing the safety risks and the assembly capacity of the later stage.

[0027] Third, the above-mentioned sodium supplement scheme of the present application not only combines the respective advantages of the positive and negative electrode sodium supplement, realizes better sodium supplement effect, and overcomes the respective disadvantages of the above-mentioned two sodium supplement methods (positive active material layer double-side sodium supplement and negative active material layer double-side sodium supplement), significantly improves the yield and feasibility of the battery cell and the secondary battery process, and is helpful to widen the application range of the positive and negative electrode sodium supplement, thereby improving the performance and safety of the battery cell.

[0028] Fourthly, the above-mentioned sodium supplement method overcomes the problem of low sodium supplement capacity and large addition amount when supplementing sodium on both sides of the positive electrode alone. The same sodium supplement dose can be achieved when supplementing sodium on one side of the positive electrode, and only half of the mass of the positive electrode active layer is supplemented with sodium. Therefore, the proportion of the sodium supplement agent can be increased under the condition of unchanged mass, higher sodium supplement demand can be achieved, the active sodium consumed by the first film formation of the negative electrode is compensated, and the cycle life of the battery is improved due to the presence of additional active sodium in the negative electrode. At the same time, the problem of obvious heating of the negative electrode sheet, poor flatness of the negative electrode sheet, and brittleness of the negative electrode sheet that leads to the inability to mass-produce can be overcome after supplementing sodium on both sides of the negative electrode. Therefore, the above-mentioned positive and negative sodium supplement method of the present application fully utilizes the respective advantages of positive and negative sodium supplement and can achieve mass production, which has practical significance for the realization of high-energy-density long-life batteries.

[0029] In the embodiments of the present application, the specific number of layers of the positive electrode unit and the negative electrode unit in the above-mentioned battery cell has no special requirements, and those skilled in the art can make flexible choices according to the actual situation of the battery cell size and battery cell design. According to some specific embodiments, the positive electrode unit and the negative electrode unit can each be 120 layers.

[0030] According to some embodiments of the present application, the sodium supplement agent in the sodium supplement positive electrode active layer includes Na2NiO2, NaC r O2, Na2C2O4, Na3N, Na2S, Na3P, Na2CO3, NaNO2, Na2C4O4, Na2C6O6, Na2C6H2O6. The specific capacity of the above-mentioned sodium supplement agent is preferably effective for supplementing sodium in the battery cell, the material is easy to purchase, and will not have adverse chemical reactions with the effective active material in the positive electrode active layer. In some preferred embodiments, the sodium supplement agent in the sodium supplement positive electrode active layer includes sodium nickelate (Na2NiO2) and sodium oxalate (Na2C2O4), which has a high specific capacity (the sodium supplement specific capacity of Na2NiO2 is about 285 mAh / g, and the sodium supplement specific capacity of Na2C2O4 is about 380 mAh / g), which can achieve better sodium supplement effect and better improve the energy density and service life of the battery.

[0031] According to some embodiments of the present application, the content of the sodium supplement agent in the sodium-supplemented positive active layer is less than or equal to 40% by mass percentage, for example, 40%, 35%, 30%, 25%, 20%, 15%, 10%, 5%, 1%, 0.5%, 0.1%, etc., based on the total mass of the non-sodium-supplemented positive active layer and the sodium-supplemented positive active layer. The sodium supplement agent in the above content can effectively and uniformly achieve good sodium supplement effect, and will not affect the performance of the positive active layer. According to some specific embodiments of the present application, the content of the sodium supplement agent in the sodium-supplemented positive active layer is 1.5-10% by mass percentage, for example, 1.5%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, etc., based on the total mass of the non-sodium-supplemented positive active layer and the sodium-supplemented positive active layer. The sodium supplement agent in the above content range can make the battery have better comprehensive performance, for example, while ensuring good sodium supplement effect, it ensures good performance of the positive electrode, improves the cycle performance, battery capacity and other performances of the battery.

[0032] According to some embodiments of the present application, the surface density of the sodium supplement agent is 1 g / m 2 ~ 18 g / m 2 , for example, the surface density of the sodium supplement agent is 1 g / m 2 , 3 g / m 2 , 5 g / m 2 , 8 g / m 2 , 10 g / m 2 , 12 g / m 2 , 15 g / m 2 , 18 g / m 2 , etc. The sodium supplement agent in the above surface density can effectively and uniformly achieve good sodium supplement effect, and will not affect the performance of the positive active layer, ensuring good cycle performance and capacity of the battery. According to some specific embodiments of the present application, the surface density of the sodium supplement agent is 4 g / m 2 ~ 16 g / m 2 . The sodium supplement agent in the above surface density range can make the battery have better comprehensive performance, for example, while ensuring good sodium supplement effect, it ensures good performance of the positive electrode, improves the cycle performance, battery capacity and other performances of the battery.

[0033] According to some embodiments of the present application, the negative sodium supplement layer is sodium foil and / or sodium powder. Metal sodium has high activity, and using metal sodium for sodium supplement can achieve better sodium supplement effect. In some specific embodiments, the negative sodium supplement layer is sodium powder, and the powdered sodium supplement agent can better and more conveniently adjust the amount of sodium supplement, which helps to improve the uniformity of sodium supplement dispersion.

[0034] According to some embodiments of the present application, the surface density of the negative sodium supplement layer is 0.5 g / m 2~10 g / m 2 For example, the areal density of the sodium supplement agent is 0.5 g / m 2 , 1 g / m 2 , 2 g / m 2 , 3 g / m 2 , 4 g / m 2 , 5 g / m 2 , 6 g / m 2 , 7 g / m 2 , 8 g / m 2 , 9 g / m 2 , 10 g / m 2 , etc. The negative electrode sodium supplement layer with the above areal density can well supplement the sodium of the battery cell, compensate for the consumption of active sodium of the negative electrode during the first film formation, significantly improve the energy density of the battery, and well compensate for the continuous loss of active sodium during the cycle process, thereby effectively improving the cycle and storage life of the battery, and ensuring the good function of the negative electrode unit. According to some specific embodiments of the present application, the areal density of the negative electrode sodium supplement layer is 1 g / m 2 ~ 6 g / m 2 . Thus, the sodium supplement effect of the battery is good, and the cycle and energy density of the battery are further ensured.

[0035] According to the embodiments of the present application, the effective active substances in the non-sodium-supplement positive electrode active layer and the sodium-supplement positive electrode active layer are at least one of transition metal oxides Na e MO2, Prussian blue compounds Na f M1[M2(CN)6], and polyanion compounds Na d M g (X a O b ) c Z h , wherein M, M1 and M2 are one or more of transition metal atoms, X is one or more of Si, S, P, As, B, Mo, W, Ge elements, and Z is one or more of F and OH, wherein M, M1 and M2 can be the same element or different elements.

[0036] In some embodiments, in addition to the effective active material, the non-sodium-supplemented positive electrode active layer and the sodium-supplemented positive electrode active layer further comprise a conductive agent (the conductive agent can comprise at least one of super conductive carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers), a binder (the binder can comprise at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorine-containing acrylic ester resin), and the like. The proportions of the raw materials are not particularly limited, and can be adjusted as needed by those skilled in the art.

[0037] In some embodiments of the present application, the effective active material of the first negative electrode sheet and the second negative electrode sheet is at least one of natural graphite, artificial graphite, soft carbon, hard carbon, mesocarbon microbeads, nano-carbon, carbon fiber, silicon negative electrode material, and sodium-embedded alloy. As can be seen, the above-mentioned sodium-supplemented technical solution of the present application can be applied to various different sodium ion battery systems.

[0038] In some embodiments, in addition to the effective active material, the first negative electrode sheet and the second negative electrode sheet further comprise a conductive agent (the conductive agent can comprise at least one of super conductive carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers), a binder (the binder can be at least one of styrene butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS)), and the like. The proportions of the raw materials are not particularly limited, and can be adjusted as needed by those skilled in the art.

[0039] According to some embodiments of the present application, the specific material of the positive electrode current collector and the negative electrode current collector is not particularly limited, and can be selected as needed by those skilled in the art, for example, the positive electrode current collector can be an aluminum foil, and the negative electrode current collector can be a copper foil.

[0040] According to the embodiments of the present application, the specific material of the above-mentioned separator is not particularly limited, and can be selected as needed by those skilled in the art. The material of the separator can be at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film, and is not particularly limited. When the separator is a multi-layer composite film, the materials of the layers can be the same or different, and are not particularly limited.

[0041] In another aspect of the present application, the present application provides a secondary battery. According to an embodiment of the present application, the secondary battery comprises the aforementioned battery cell. Thus, the service life of the secondary battery is longer. It is appreciated by those skilled in the art that the electric device has all the features and advantages of the aforementioned secondary battery, which will not be repeated here.

[0042] According to an embodiment of the present application, the aforementioned battery can be a stacked battery or a jelly-roll battery.

[0043] According to an embodiment of the present application, the aforementioned secondary battery further comprises a housing, which can be an aluminum case, a steel case, a soft package, or the like.

[0044] In another aspect of the present application, the present application provides an electric device. According to an embodiment of the present application, the electric device comprises the aforementioned secondary battery. Thus, the service life of the electric device is longer. It is appreciated by those skilled in the art that the electric device has all the features and advantages of the aforementioned secondary battery, which will not be repeated here.

[0045] According to an embodiment of the present application, the specific type of the electric device is not particularly required, and those skilled in the art can flexibly select it according to actual needs, such as a mobile device (e.g., a mobile phone, a notebook computer, or the like), an electric vehicle (e.g., a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, or the like), an electric train, a ship, a satellite, an energy storage system, or the like, but is not limited thereto.

[0046] Embodiments

[0047] Embodiment 1

[0048] The preparation method of the secondary battery comprises:

[0049] 1) Preparation of a non-sodium-supplemented positive electrode active layer: 100 parts by mass of iron-based Prussian white (Na2Fe[Fe(CN)6]), 2 parts by mass of a conductive agent, and 2.2 parts by mass of a binder are mixed by NMP dissolution to prepare a positive electrode slurry without a sodium supplementing agent. The slurry is coated on an aluminum foil, and the effective active material surface density of the coating is 180 g / m2. 2 The side of the non-sodium-supplemented positive electrode active layer is denoted as P n layer (without pre-sodium).

[0050] 2) Preparation of a sodium-supplemented positive electrode active layer: 97.8 parts by mass of iron-based Prussian white (Na2Fe[Fe(CN)6]), 2.2 parts by mass of a Na2NiO2 sodium supplementing agent, 2 parts by mass of a conductive agent, and 2.2 parts by mass of a binder are mixed by NMP dissolution to prepare a positive electrode slurry containing a sodium supplementing agent. The slurry is coated on the other side of the aluminum foil, and the active material surface density p (including the sodium supplementing agent) of the coating is 184 g / m2.2 wherein the sodium supplement agent areal density is 4.0 g / m 2 , and the effective active material areal density is 180 g / m 2 The side of the sodium supplement positive active layer is marked as P p layer (pre-sodiumization);

[0051] 3) Positive electrode sheet roll cutting: the positive electrode sheet coated with P n layer and P p layer is roll cut to form a positive electrode unit with single-sided sodium supplement, wherein the sodium supplement agent areal density accounts for x = 4.0 / 184 * 100% = 2.2% of the total effective active material (i.e. the content of sodium supplement agent in the sodium supplement positive active layer).

[0052] 4) Negative electrode sheet preparation: 100 parts by mass of hard carbon material, 1 part by mass of conductive agent, and 5 parts by mass of binder are uniformly mixed by dissolving in deionized water to form a negative electrode slurry. The slurry is coated on a copper foil, and the single-sided active material areal density of the coating is 95.8 g / m 2 , and the double-sided active material areal density is 191.6 g / m 2 .

[0053] 5) Single-sided sodium supplement of negative electrode sheet: sodium powder or sodium foil is used to supplement sodium on one side of the roll-cut negative electrode sheet, and the areal density s of the negative electrode sodium supplement layer is 1.5 g / m 2 The side containing the sodium supplement layer is marked as N p layer (pre-sodiumization), and the side without sodium supplement layer is marked as N n layer (without pre-sodiumization).

[0054] 6) Negative electrode sheet die cutting: the negative electrode sheet coated with N n and N p layers is die cut to form a negative electrode unit with single-sided sodium supplement.

[0055] 7) Stacking of positive and negative electrode units: the Pn layer of the positive electrode unit corresponds to the N p layer of the negative electrode unit, the P p layer of the positive electrode unit corresponds to the N n layer of the negative electrode unit, and a separator is added between the positive and negative electrode units to form a 7+8 layer soft pack small cell. After being packaged in an aluminum shell or aluminum plastic film, the secondary battery is subjected to first charge and discharge after liquid injection, and the designed capacity of the battery is 1527 mAh.

[0056] 9) Sodium supplement battery liquid injection and decomposition: the battery after liquid injection is subjected to formation using 0.05C constant current charging for 2h and 0.2C constant current charging for 3h to form SEI film. Then, the battery is further charged to 4.0V using 0.005C current to fully decompose and desodium the sodium supplement agent in the sodium supplement positive active layer, and the negative electrode side without sodium supplement layer is subjected to electrochemical sodium supplement.

[0057] 10) Sodium supplement battery sorting: After the battery is aged for 24 h after air extraction and sealing, it is sorted, and the sorting step is 1 / 3C constant current constant voltage charging to 4.0V, standing for 10 min, 1 / 3C constant current discharging to 2.0V, recording the discharge capacity at this time as C0, and recording the OCV of the battery after standing for 24 h.

[0058] Example 2

[0059] The preparation method of the secondary battery comprises:

[0060] 1) Preparation of a non-sodium-supplemented positive electrode active layer: 100 parts by mass of iron-based Prussian white (Na2Fe[Fe(CN)6]), 2 parts by mass of a conductive agent, and 2.2 parts by mass of a binder are mixed by NMP dissolution to prepare a positive electrode slurry without a sodium supplement agent, and the slurry is coated on an aluminum foil, and the effective active material surface density of the coating is 180 g / m 2 , and the non-sodium-supplemented positive electrode active layer on this side is denoted as P n layer (without pre-sodium);

[0061] 2) Preparation of a sodium-supplemented positive electrode active layer: 96.8 parts by mass of iron-based Prussian white (Na2Fe[Fe(CN)6]), 3.2 parts by mass of a Na2NiO2 sodium supplement agent, and 2 parts by mass of a conductive agent and 2.2 parts by mass of a binder are mixed by NMP dissolution to prepare a positive electrode slurry containing a sodium supplement agent, and the slurry is coated on the other side of the aluminum foil, and the active material surface density (including the sodium supplement agent) of the coating is 185.9 g / m 2 , wherein the sodium supplement agent surface density is 5.9 g / m 2 , and the effective active material surface density is 180 g / m 2 , and the sodium-supplemented positive electrode active layer on this side is denoted as P p layer (pre-sodium);

[0062] 3) Positive electrode sheet rolling and die cutting: the positive electrode sheet coated with the P n layer and the P p layer is rolled and die cut to form a positive electrode unit with single-sided sodium supplementation, wherein the proportion of the sodium supplement agent surface density to the total effective active material (i.e., the content of the sodium supplement agent in the sodium-supplemented positive electrode active layer) is x=5.9 / 185.9*100%=3.2%.

[0063] 4) Preparation of a negative electrode sheet: 100 parts by mass of a hard carbon material, 1 part by mass of a conductive agent, and 5 parts by mass of a binder are uniformly mixed by deionized water dissolution to prepare a negative electrode slurry, and the slurry is coated on a copper foil, and the single-sided active material surface density of the coating is 96.9 g / m 2 , and the double-sided active material surface density is 193.8 g / m 2 .

[0064] 5) Negative electrode tab single side sodium supplement: After rolling, the negative electrode tab on one side is supplemented with sodium powder or sodium foil. The surface density s of the negative electrode sodium supplement layer is 2.3 g / m 2 The side containing the sodium supplement layer is marked as N p The side without the sodium supplement layer is marked as N n The side without the sodium supplement layer is marked as N

[0065] 6) Negative electrode tab die cutting: The negative electrode tab coated with N n and N p layers is die cut to form a negative electrode unit with single side sodium supplement.

[0066] 7) Positive and negative electrode unit lamination: The Pn layer of the positive electrode unit corresponds to the N p layer of the negative electrode unit, the P p layer of the positive electrode unit corresponds to the N n layer of the negative electrode unit, and a separator is added between the positive and negative electrode units to form a 7+8 layer soft pack small cell. After being packaged in an aluminum shell or aluminum plastic film, a secondary battery is prepared. After being primed, the first charge and discharge is performed. The battery design capacity is 1578 mAh.

[0067] 9) Sodium supplement battery priming decomposition: The primed battery is subjected to formation using 0.05C constant current charging for 2h and 0.2C constant current charging for 3h. After the SEI film is formed, the battery is further charged to 4.0V using a current of 0.005C, so that the sodium supplement agent of the sodium supplement positive electrode active layer is fully decomposed and desodiated, and the negative electrode side without the sodium supplement layer is subjected to electrochemical sodium supplement.

[0068] 10) Sodium supplement battery sorting: After the battery is subjected to air extraction and sealing aging for 24h, it is subjected to capacity sorting. The capacity sorting step is 1 / 3C constant current constant voltage charging to 4.0V, standing for 10min, 1 / 3C constant current discharging to 2.0V, recording the discharge capacity at this time as C0, and recording the battery OCV after standing for 24h.

[0069] Example 3

[0070] The preparation method of the secondary battery comprises:

[0071] 1) Preparation of non-sodium supplement positive electrode active layer: 100 parts by mass of iron-based Prussian white (Na2Fe[Fe(CN)6]), 2 parts by mass of conductive agent, and 2.2 parts by mass of binder are mixed by NMP dissolution to prepare a positive electrode slurry without sodium supplement agent. The slurry is applied to an aluminum foil, and the effective active material surface density of the application is 180 g / m 2 The side of the non-sodium supplement positive electrode active layer is marked as P n layer (without pre-sodium).

[0072] 2) Preparation of sodium supplement positive electrode active layer: 95.8 parts by mass of iron-based Prussian white (Na2Fe[Fe(CN)6]), 4.2 parts by mass of Na2NiO2 sodium supplement agent, 2 parts by mass of conductive agent, and 2.2 parts by mass of binder are mixed by NMP dissolution to prepare a positive electrode slurry containing a sodium supplement agent, and the slurry is coated on the other side of the aluminum foil, with a coated active material surface density (including the sodium supplement agent) of 187.9 g / m 2 , wherein the sodium supplement agent surface density is 7.9 g / m 2 , and the effective active material surface density is 180 g / m 2 . The side of the sodium supplement positive electrode active layer is denoted as P p layer (pre-sodium).

[0073] 3) Positive electrode tab roll pressing and die cutting: the positive electrode tab coated with the P n layer and the P p layer is roll pressed and die cut to form a positive electrode unit with single-sided sodium supplement, wherein the sodium supplement agent surface density accounts for x = 7.9 / 187.9*100% = 4.2% of the total effective active material (i.e., the content of the sodium supplement agent in the sodium supplement positive electrode active layer).

[0074] 4) Negative electrode tab preparation: 100 parts by mass of hard carbon material, 1 part by mass of conductive agent, and 5 parts by mass of binder are uniformly mixed by deionized water dissolution to prepare a negative electrode slurry, and the slurry is coated on a copper foil, with a coated single-sided active material surface density of 99.0 g / m 2 and a double-sided active material surface density of 197.9 g / m 2 .

[0075] 5) Single-sided sodium supplement of negative electrode tab: sodium powder or sodium foil is used to supplement sodium to one side of the roll-pressed negative electrode tab, with a negative electrode sodium supplement layer surface density s of 3.1 g / m 2 . The side containing the sodium supplement layer is denoted as N p layer (pre-sodium), and the side without the sodium supplement layer is denoted as N n layer (without pre-sodium).

[0076] 6) Negative electrode tab die cutting: the negative electrode tab coated with the N n and N p layers is die cut to form a negative electrode unit with single-sided sodium supplement.

[0077] 7) Positive and negative electrode unit lamination: the Pn layer of the positive electrode unit corresponds to the N p layer of the negative electrode unit, and the P p layer of the positive electrode unit corresponds to the N n layer of the negative electrode unit.The 7+8 layer soft package small battery is made by laminating the layers and adding a separator between the positive and negative electrode units, and is made into a secondary battery by packaging the battery in an aluminum shell or an aluminum plastic film after the battery is filled with liquid and subjected to the first charge and discharge, and the design capacity of the battery is 1587 mAh;

[0078] 9) Sodium supplement battery liquid injection component decomposition: the battery after liquid injection is subjected to formation by using 0.05C constant current charging for 2h and 0.2C constant current charging for 3h, and after the SEI film is formed, the battery is further charged to 4.0V by using 0.005C current, so that the sodium supplement agent in the sodium supplement positive active layer is fully decomposed and desodiated, and the negative electrode side without the sodium supplement layer is subjected to electrochemical sodium supplement;

[0079] 10) Sodium supplement battery sorting: the battery is subjected to sorting after being subjected to air extraction and sealing for 24h, and the sorting step is 1 / 3C constant current charging to 4.0V, standing for 10min, 1 / 3C constant current discharging to 2.0V, and recording the discharge capacity at this time as C0, and recording the OCV of the battery after standing for 24h.

[0080] Example 4

[0081] The preparation method of the secondary battery comprises:

[0082] 1) Preparation of a non-sodium supplement positive active layer: 100 parts by mass of iron-based Prussian white (Na2Fe[Fe(CN)6]), 2 parts by mass of a conductive agent and 2.2 parts by mass of a binder are mixed by NMP dissolution to prepare a positive electrode slurry without a sodium supplement agent, and the slurry is applied to one side of an aluminum foil, and the effective active material surface density of the applied side is 180 g / m 2 The non-sodium supplement positive active layer on this side is denoted as P n layer (without pre-sodium);

[0083] 2) Preparation of a sodium supplement positive active layer: 94.3 parts by mass of iron-based Prussian white (Na2Fe[Fe(CN)6]), 5.7 parts by mass of Na2NiO2 sodium supplement agent, 2 parts by mass of a conductive agent and 2.2 parts by mass of a binder are mixed by NMP dissolution to prepare a positive electrode slurry containing a sodium supplement agent, and the slurry is applied to the other side of the aluminum foil, and the active material surface density (including the sodium supplement agent) p of the applied side is 191.0 g / m 2 , wherein the sodium supplement agent surface density is 11.0 g / m 2 , and the effective active material surface density is 180 g / m 2 The sodium supplement positive active layer on this side is denoted as P p layer (pre-sodium);

[0084] 3) Positive electrode sheet rolling and die cutting: the P n layer and the P pThe positive electrode sheet is rolled and die-cut to form a positive electrode unit with single-sided sodium supplement, wherein the surface density of the sodium supplement agent accounts for x = 11.0 / 191*100% = 5.8% of the total effective active material proportion (i.e. the content of the sodium supplement agent in the sodium-supplemented positive active layer).

[0085] 4) Preparation of negative electrode sheet: 100 parts by mass of hard carbon material, 1 part by mass of conductive agent and 5 parts by mass of binder are uniformly mixed by dissolving in deionized water to form a negative electrode slurry, which is coated on a copper foil. The single-sided active material surface density of the coating is 102.1 g / m 2 , and the double-sided active material surface density is 204.2 g / m 2 .

[0086] 5) Single-sided sodium supplement of negative electrode sheet: sodium powder or sodium foil is supplemented to one side of the negative electrode sheet after rolling. The surface density s of the negative electrode sodium supplement layer is 4.2 g / m 2 . The side containing the sodium supplement layer is marked as N p layer (pre-sodiumization), and the side without the sodium supplement layer is marked as N n layer (without pre-sodiumization).

[0087] 6) Die-cutting of negative electrode sheet: the negative electrode sheet coated with N n and N p layers is die-cut to form a negative electrode unit with single-sided sodium supplement.

[0088] 7) Assembly of positive and negative electrode units: the Pn layer of the positive electrode unit corresponds to the N p layer of the negative electrode unit, the P p layer of the positive electrode unit corresponds to the N n layer of the negative electrode unit, and a separator is added between the positive and negative electrode units to form a 7+8 layer soft-pack small battery cell, which is packaged in an aluminum shell or an aluminum-plastic film to form a secondary battery. After liquid injection, the first charge and discharge is performed, and the battery design capacity is 1595 mAh.

[0089] 9) Decomposition of sodium-supplemented battery after liquid injection: the battery after liquid injection is subjected to formation using 0.05C constant current charging for 2h and 0.2C constant current charging for 3h to form an SEI film. Then, the battery is further charged to 4.0V using a current of 0.005C, so that the sodium supplement agent in the sodium-supplemented positive active layer is fully decomposed and desodiated, and the negative electrode side without the sodium supplement layer is subjected to electrochemical sodium supplement.

[0090] 10) Sorting of sodium-supplemented battery: the battery is subjected to air extraction and sealing aging for 24h, and then is subjected to capacity sorting. The sorting process is as follows: 1 / 3C constant current and constant voltage charging to 4.0V, standing for 10min, 1 / 3C constant current discharging to 2.0V, recording the discharge capacity at this time as C0, and standing for 24h to record the OCV of the battery.

[0091] Example 5

[0092] The method for preparing a secondary battery comprises:

[0093] 1) Preparation of a non-sodium-supplemented positive electrode active layer: 100 parts by mass of iron-based Prussian white (Na2Fe[Fe(CN)6]), 2 parts by mass of a conductive agent, and 2.2 parts by mass of a binder are mixed by NMP dissolution to prepare a positive electrode slurry without a sodium supplement agent. The slurry is applied to one side of an aluminum foil, and the effective active material surface density of the applied side is 180 g / m 2 . The side of the non-sodium-supplemented positive electrode active layer is denoted as P n layer (without pre-sodium).

[0094] 2) Preparation of a sodium-supplemented positive electrode active layer: 93.3 parts by mass of iron-based Prussian white (Na2Fe[Fe(CN)6]), 6.7 parts by mass of a Na2NiO2 sodium supplement agent, 2 parts by mass of a conductive agent, and 2.2 parts by mass of a binder are mixed by NMP dissolution to prepare a positive electrode slurry with a sodium supplement agent. The slurry is applied to the other side of the aluminum foil, and the active material surface density (including the sodium supplement agent) of the applied side is 193 g / m 2 , wherein the sodium supplement agent surface density is 13.0 g / m 2 , and the effective active material surface density is 180 g / m 2 . The side of the sodium-supplemented positive electrode active layer is denoted as P p layer (pre-sodium).

[0095] 3) Positive electrode tab roll pressing and die cutting: the positive electrode tab coated with the P n layer and the P p layer is roll pressed and die cut to prepare a positive electrode unit with a single side sodium-supplemented positive electrode. The proportion of the sodium supplement agent surface density to the total effective active material (i.e., the content of the sodium supplement agent in the sodium-supplemented positive electrode active layer) is x = 13.0 / 193*100% = 6.7%.

[0096] 4) Preparation of a negative electrode tab: 100 parts by mass of a hard carbon material, 1 part by mass of a conductive agent, and 5 parts by mass of a binder are uniformly mixed by deionized water dissolution to prepare a negative electrode slurry. The slurry is applied to a copper foil, and the single-side active material surface density of the applied side is 104.2 g / m 2 , and the double-side active material surface density is 208.4 g / m 2 .

[0097] 5) Single-side sodium supplementation of a negative electrode tab: sodium powder or sodium foil is used to supplement sodium to one side of the roll-pressed negative electrode tab. The surface density s of the negative electrode sodium-supplemented layer is 5.0 g / m 2 . The side containing the sodium-supplemented layer is denoted as N p layer (pre-sodium), and the side without the sodium-supplemented layer is denoted as N n layer (without pre-sodium).

[0098] 6) Die cutting of a negative electrode tab: the negative electrode tab coated with the Nn and N p The negative electrode sheet with the negative single-sided sodium supplementing negative electrode unit is prepared after die cutting.

[0099] 7) Positive and negative electrode unit stack assembly: the Pn layer of the positive electrode unit corresponds to the N p layer of the negative electrode unit, the P p layer of the positive electrode unit corresponds to the N n layer of the negative electrode unit, and a separator is arranged between the positive and negative electrode units to form a 7+8 layer soft package small battery cell, which is packaged in an aluminum shell or an aluminum plastic film to form a secondary battery. After liquid injection, the first charge and discharge is performed, and the battery design capacity is 1604mAh;

[0100] 9) Sodium supplementing battery liquid injection decomposition: the battery after liquid injection is subjected to formation using 0.05C constant current charging for 2h and 0.2C constant current charging for 3h, and after the SEI film is formed, the battery is further charged to 4.0V using a current of 0.005C, so that the sodium supplementing agent of the sodium supplementing positive active layer is fully decomposed and desodiated, and the negative electrode side without the sodium supplementing layer is subjected to electrochemical sodium supplementing;

[0101] 10) Sodium supplementing battery sorting: the battery is subjected to air extraction and sealing aging for 24h, and then is subjected to sorting, and the sorting step is 1 / 3C constant current constant voltage charging to 4.0V, standing for 10min, 1 / 3C constant current discharging to 2.0V, recording the discharge capacity at this time as C0, and standing for 24h to record the OCV of the battery.

[0102] Example 6

[0103] The preparation method of the secondary battery comprises:

[0104] 1) Preparation of non-sodium supplementing positive active layer: 100 parts by mass of iron-based Prussian white (Na2Fe[Fe(CN)6]), 2 parts by mass of conductive agent and 2.2 parts by mass of binder are mixed by NMP dissolution to prepare a positive electrode slurry without sodium supplementing agent. The slurry is coated on an aluminum foil, and the effective active material surface density of the coated side is 180g / m 2 , and the non-sodium supplementing positive active layer is recorded as P n layer (without pre-sodium).

[0105] 2) Preparation of sodium supplementing positive active layer: 91.8 parts by mass of iron-based Prussian white (Na2Fe[Fe(CN)6]), 8.2 parts by mass of Na2NiO2 sodium supplementing agent, 2 parts by mass of conductive agent and 2.2 parts by mass of binder are mixed by NMP dissolution to prepare a positive electrode slurry containing sodium supplementing agent. The slurry is coated on the other side of the aluminum foil, and the active material surface density (including the sodium supplementing agent) of the coated side is 196g / m 2 , wherein the sodium supplementing agent surface density is 16.0g / m 2 , and the effective active material surface density is 180g / m2 The side-sodium-supplemented positive active layer is denoted as P p layer (pre-sodiumization) ;

[0106] 3) Positive electrode tab roll cutting: the positive electrode tab coated with P n and P p layers is roll cut to form a positive electrode unit with single-side sodium supplementation, wherein the sodium supplementing agent surface density accounts for x = 16.0 / 196*100% = 8.2% of the total effective active material proportion (i.e., the content of the sodium supplementing agent in the sodium-supplemented positive active layer).

[0107] 4) Negative electrode tab preparation: 100 parts by mass of hard carbon material, 1 part by mass of conductive agent, and 5 parts by mass of binder are uniformly mixed by dissolving in deionized water to form a negative electrode slurry, which is applied to a copper foil. The single-side active material surface density of the coating is 108.3 g / m 2 , and the double-side active material surface density is 216.6 g / m 2 .

[0108] 5) Single-side sodium supplementation of the negative electrode tab: sodium powder or sodium foil is used to supplement sodium to one side of the roll-cut negative electrode tab, and the surface density s of the negative electrode sodium-supplemented layer is 6.2 g / m 2 . The side containing the sodium-supplemented layer is denoted as N p layer (pre-sodiumization), and the side without the sodium-supplemented layer is denoted as N n layer (without pre-sodiumization).

[0109] 6) Negative electrode tab cutting: the negative electrode tab coated with N n and N p layers is cut to form a negative electrode unit with single-side sodium supplementation.

[0110] 7) Assembly of positive and negative electrode units: the Pn layer of the positive electrode unit corresponds to the N p layer of the negative electrode unit, the P p layer of the positive electrode unit corresponds to the N n layer of the negative electrode unit, and a separator is added between the positive and negative electrode units to form a 7+8-layer soft-pack small battery, which is then packaged in an aluminum shell or aluminum-plastic film to form a secondary battery. After liquid injection, the first charge and discharge are performed, and the battery design capacity is 1613 mAh.

[0111] 9) Sodium-supplemented battery liquid injection and decomposition: after liquid injection, the battery is subjected to formation using 0.05C constant current charging for 2h and 0.2C constant current charging for 3h to form an SEI film. Then, the battery is further charged to 4.0V using a current of 0.005C to fully decompose and desodium the sodium supplementing agent in the sodium-supplemented positive active layer, and the negative electrode side without the sodium-supplemented layer is subjected to electrochemical sodium supplementation.

[0112] 10) Sodium supplement battery sorting: After the battery is aged for 24 h after air extraction and sealing, it is sorted, and the sorting step is 1 / 3C constant current constant voltage charging to 4.0V, standing for 10 min, 1 / 3C constant current discharging to 2.0V, recording the discharge capacity at this time as C0, and recording the OCV of the battery after standing for 24 h.

[0113] Example 7

[0114] The preparation method of the secondary battery comprises:

[0115] 1) Preparation of a non-sodium-supplement positive active layer: 100 parts by mass of iron-based Prussian white (Na2Fe[Fe(CN)6]), 2 parts by mass of a conductive agent, and 2.2 parts by mass of a binder are mixed by NMP dissolution to prepare a positive electrode slurry without a sodium supplement agent, and the slurry is coated on an aluminum foil, and the effective active material surface density of the coating is 180 g / m 2 , and the side of the non-sodium-supplement positive active layer is denoted as P n layer (without pre-sodium).

[0116] 2) Preparation of a sodium-supplement positive active layer: 90.9 parts by mass of iron-based Prussian white (Na2Fe[Fe(CN)6]), 9.1 parts by mass of Na2NiO2 sodium supplement agent, 2 parts by mass of a conductive agent, and 2.2 parts by mass of a binder are mixed by NMP dissolution to prepare a positive electrode slurry containing a sodium supplement agent, and the slurry is coated on the other side of the aluminum foil, and the active material surface density (including the sodium supplement agent) of the coating is 198 g / m 2 , wherein the sodium supplement agent surface density is 18.0 g / m 2 , and the effective active material surface density is 180 g / m 2 , and the side of the sodium-supplement positive active layer is denoted as P p layer (pre-sodium).

[0117] 3) Positive electrode sheet rolling and die cutting: the positive electrode sheet coated with the P n layer and the P p layer is rolled and die cut to form a positive electrode unit with single-side sodium supplement, wherein the proportion of the sodium supplement agent surface density to the total effective active material (i.e., the content of the sodium supplement agent in the sodium-supplement positive active layer) is x = 18.0 / 198*100% = 9.1%.

[0118] 4) Preparation of a negative electrode sheet: 100 parts by mass of a hard carbon material, 1 part by mass of a conductive agent, and 5 parts by mass of a binder are uniformly mixed by deionized water dissolution to prepare a negative electrode slurry, and the slurry is coated on a copper foil, and the single-side active material surface density of the coating is 110.4 g / m 2 , and the double-side active material surface density is 220.8 g / m 2 .

[0119] 5) Negative electrode tab single side sodium supplement: After rolling, the negative electrode tab on one side is supplemented with sodium powder or sodium foil. The surface density s of the negative electrode sodium supplement layer is 7.0 g / m 2 The side containing the sodium supplement layer is marked as N p The side without the sodium supplement layer is marked as N n The side without the sodium supplement layer is marked as N

[0120] 6) Negative electrode tab die cutting: The negative electrode tab coated with N n and N p layers is die cut to form a negative electrode single side sodium supplement negative electrode unit.

[0121] 7) Positive and negative electrode unit lamination assembly: The Pn layer of the positive electrode unit corresponds to the N p layer of the negative electrode unit, the P p layer of the positive electrode unit corresponds to the N n layer of the negative electrode unit, and a separator is added between the positive and negative electrode units to form a 7+8 layer soft package small cell. After being packaged in an aluminum shell or an aluminum plastic film, a secondary battery is prepared. After being injected and subjected to the first charge and discharge, the battery design capacity is 1630 mAh.

[0122] 9) Sodium supplement battery liquid injection decomposition: The battery after injection is subjected to formation using 0.05C constant current charging for 2h and 0.2C constant current charging for 3h. After the formation of the SEI film, the battery is further charged to 4.0V using a current of 0.005C, so that the sodium supplement agent of the sodium supplement positive electrode active layer is fully decomposed and desodiated, and the negative electrode side without the sodium supplement layer is subjected to electrochemical sodium supplement.

[0123] 10) Sodium supplement battery sorting: The battery is subjected to air extraction and sealing aging for 24h, and then is subjected to sorting. The sorting step is 1 / 3C constant current and constant voltage charging to 4.0V, standing for 10min, 1 / 3C constant current discharging to 2.0V, recording the discharge capacity at this time as C0, and recording the OCV of the battery after standing for 24h.

[0124] Example 8

[0125] The preparation method of the secondary battery comprises:

[0126] 1) Preparation of non-sodium supplement positive electrode active layer: 100 parts by mass of iron-based Prussian white (Na2Fe[Fe(CN)6]), 2 parts by mass of conductive agent, and 2.2 parts by mass of binder are mixed by NMP dissolution to prepare a positive electrode slurry without sodium supplement agent. The slurry is coated on an aluminum foil, and the effective active material surface density of the coating is 180 g / m 2 The side of the non-sodium supplement positive electrode active layer is marked as P n layer (without pre-sodium).

[0127] 2) Preparation of sodium supplement positive electrode active layer: 99.4 parts by mass of iron-based Prussian white (Na2Fe[Fe(CN)6]), 0.6 parts by mass of Na2NiO2 sodium supplement agent, 2 parts by mass of conductive agent, and 2.2 parts by mass of binder are mixed by NMP dissolution to prepare a positive electrode slurry containing a sodium supplement agent, and the slurry is coated on the other side of the aluminum foil. The coated active material area density (including the sodium supplement agent) is 181.1 g / m 2 , wherein the sodium supplement agent area density is 1.1 g / m 2 , and the effective active material area density is 180 g / m 2 . The side of the sodium supplement positive electrode active layer is denoted as P p layer (pre-sodium).

[0128] 3) Positive electrode tab rolling and die cutting: the positive electrode tab coated with the P n layer and the P p layer is rolled and die cut to form a positive electrode unit with single-sided sodium supplement. The sodium supplement agent area density accounts for x = 1.1 / 181.1*100% = 0.6% of the total effective active material.

[0129] 4) Negative electrode tab preparation: 100 parts by mass of hard carbon material, 1 part by mass of conductive agent, and 5 parts by mass of binder are uniformly mixed by deionized water dissolution to prepare a negative electrode slurry, which is coated on a copper foil. The single-sided active material area density of the coated slurry is 95.8 g / m 2 , and the double-sided active material area density is 191.6 g / m 2 .

[0130] 5) Single-sided sodium supplement of negative electrode tab: sodium powder or sodium foil is used to supplement sodium on one side of the rolled negative electrode tab. The area density s of the negative electrode sodium supplement layer is 0.4 g / m 2 . The side containing the sodium supplement layer is denoted as N p layer (pre-sodium), and the side without sodium supplement layer is denoted as N n layer (without pre-sodium).

[0131] 6) Negative electrode tab die cutting: the negative electrode tab coated with the N n layer and the N p layer is die cut to form a negative electrode unit with single-sided sodium supplement.

[0132] 7) Assembly of positive and negative electrode units: the Pn layer of the positive electrode unit corresponds to the N p layer of the negative electrode unit, the P p layer of the positive electrode unit corresponds to the N n layer of the negative electrode unit, and a separator is added between the positive and negative electrode units to form a 7+8 layer soft pack small cell. After being packaged in an aluminum shell or aluminum plastic film, a secondary battery is prepared. After liquid injection, the first charge and discharge is performed. The battery design capacity is 1475 mAh.

[0133] 9) Sodium supplementing battery liquid injection decomposition: the battery after liquid injection is subjected to formation using 0.05C constant current charging for 2h and 0.2C constant current charging for 3h, after the formation of SEI film, the battery is further charged to 4.0V using 0.005C current, so that the sodium supplementing agent of the sodium supplementing positive active layer is fully decomposed and desodiated, and the negative electrode side without the sodium supplementing layer is subjected to electrochemical sodium supplementing;

[0134] 10) Sodium supplementing battery sorting: the battery is subjected to air extraction and sealing aging for 24h, and then is subjected to sorting, the sorting process is 1 / 3C constant current constant voltage charging to 4.0V, standing for 10min, 1 / 3C constant current discharging to 2.0V, recording the discharging capacity at this time as C0, and recording the OCV of the battery after standing for 24h.

[0135] Comparative Example 1

[0136] The preparation method of the secondary battery (without sodium supplementing for both positive and negative electrodes) comprises:

[0137] 1) Preparation of positive active layer: 100 parts by mass of iron-based Prussian white (Na2Fe[Fe(CN)6]), 2 parts by mass of conductive agent and 2.2 parts by mass of binder are mixed by NMP dissolution to prepare positive electrode slurry without sodium supplementing agent, the slurry is coated on both sides of aluminum foil, and the effective active material area density of the coating is 180g / m 2 , and the effective active material area density of both sides is 360g / m 2 ;

[0138] 2) Preparation of negative electrode sheet: 100 parts by mass of hard carbon material, 1 part by mass of conductive agent and 5 parts by mass of binder are uniformly mixed by deionized water dissolution to prepare negative electrode slurry, the slurry is coated on copper foil, and the single-side active material area density of the coating is 95.8g / m 2 , and the double-side active material area density is 191.6g / m 2 ;

[0139] 3) Positive and negative electrode sheet die cutting, lamination and assembly: the positive and negative electrode sheets are die cut, laminated with the separator to prepare 7+8 layer soft package small cells, which are packaged in aluminum shells or aluminum plastic films to prepare batteries, the batteries are subjected to first charging and discharging after liquid injection, and the design capacity of the battery is 1458mAh;

[0140] 4) Battery liquid injection decomposition: the battery after liquid injection is subjected to formation using 0.05C constant current charging for 2h and 0.2C constant current charging for 3h;

[0141] 10) Battery sorting: the battery is subjected to air extraction and sealing aging for 24h, and then is subjected to sorting, the sorting process is 1 / 3C constant current constant voltage charging to 4.0V, standing for 10min, 1 / 3C constant current discharging to 2.0V, recording the discharging capacity at this time as C0, and recording the OCV of the battery after standing for 24h.

[0142] Comparative Example 2

[0143] The preparation method of the secondary battery (sodium supplement on both sides of the positive electrode, no sodium supplement on the negative electrode) comprises:

[0144] 1) Preparation of the positive electrode sheet: 94.3 parts of iron-based Prussian white (Na2Fe[Fe(CN)6]), 5.7 parts of Na2NiO2 sodium supplement agent, 2 parts of conductive agent, and 2.2 parts of binder are mixed by NMP dissolution to prepare a positive electrode slurry containing the sodium supplement agent. The slurry is coated on both sides of an aluminum foil, and the single-sided active material density of the coating is 185.5 g / m2(the active material layer is 180 g / m2, and the sodium supplement agent is 5.5 g / m2). 2 (the active material layer is 360 g / m2, and the sodium supplement agent is 11 g / m2). 2 (the active material layer is 180 g / m2, and the sodium supplement agent is 5.5 g / m2). 2 (the active material layer is 360 g / m2, and the sodium supplement agent is 11 g / m2). 2 (the active material layer is 180 g / m2, and the sodium supplement agent is 5.5 g / m2). 2 (the active material layer is 360 g / m2, and the sodium supplement agent is 11 g / m2). 2

[0145] 2) Roll cutting of the positive electrode sheet: the positive electrode sheet with the sodium supplement agent added on both sides is roll cut to prepare a positive electrode sheet with sodium supplement on both sides, wherein the sodium supplement agent accounts for 3.0% of the total effective active material (i.e., the content of the sodium supplement agent in the sodium-supplemented positive active layer) x = 5.5 / 185.5*100% = 3.0%.

[0146] 3) Preparation of the negative electrode sheet: 100 parts of hard carbon material, 1 part of conductive agent, and 5 parts of binder are uniformly mixed by deionized water dissolution to prepare a negative electrode slurry. The slurry is coated on a copper foil, and the single-sided active material density of the coating is 102.1 g / m2, and the double-sided active material density is 204.2 g / m2. 2 2

[0147] 5) Roll cutting and stacking of the positive and negative electrode sheets: the positive and negative electrode sheets are roll cut and stacked with a separator to prepare a 7+8 layer soft package small cell. After being packaged in an aluminum shell or an aluminum plastic film, the battery is prepared. After being injected, the first charge and discharge is performed, and the design capacity of the battery is 1527 mAh.

[0148] 6) Liquid injection and decomposition of the sodium-supplemented positive battery: the battery after injection is subjected to formation by using 0.05C constant current charging for 2h and 0.2C constant current charging for 3h. After the formation of the SEI film, the battery is further charged to 4.0V by using 0.005C current, so that the sodium supplement agent in the sodium-supplemented positive active layer is fully decomposed and desodiated, and the battery is subjected to electrochemical sodium supplement.

[0149] ​​​10) Battery sorting: After the battery is aged for 24 h after air extraction sealing, it is sorted, and the sorting step is 1 / 3C constant current constant voltage charging to 4.0V, standing for 10 min, 1 / 3C constant current discharging to 2.0V, recording the discharge capacity at this time as C0, and recording the OCV of the battery after standing for 24 h.

[0150] Comparative Example 3

[0151] The preparation method of the secondary battery (sodium supplement on both sides of the positive electrode, no sodium supplement on the negative electrode) comprises:

[0152] 1) Positive electrode tab preparation: 90.0 parts of iron-based Prussian white (Na2Fe[Fe(CN)6]), 10.0 parts of Na2NiO2 sodium supplement agent, 2 parts of conductive agent, and 2.2 parts of binder are mixed by NMP dissolution to prepare a positive electrode slurry containing a sodium supplement agent. The slurry is coated on both sides of an aluminum foil, and the single-sided active material density of the coating is 190 g / m 2 (containing a sodium supplement agent), wherein the sodium supplement agent surface density is 10.0 g / m 2 , and the effective active material surface density is 180 g / m 2 ; the double-sided active material surface density is 380 g / m 2 (containing a sodium supplement agent), wherein the double-sided sodium supplement agent surface density is 20 g / m 2 , and the double-sided effective active material surface density is 360 g / m 2 .

[0153] 2) Positive electrode tab rolling and die cutting: the positive electrode tab with sodium supplement agent added on both sides is rolled and die cut to prepare a positive electrode tab with sodium supplement agent on both sides, wherein the sodium supplement agent surface density accounts for x = 10 / 190 * 100% = 5.3% of the total effective active material (i.e. the content of the sodium supplement agent in the sodium supplement positive active layer).

[0154] 3) Negative electrode tab preparation: 100 parts by mass of hard carbon material, 1 part by mass of conductive agent, and 5 parts by mass of binder are uniformly mixed by deionized water dissolution to prepare a negative electrode slurry. The slurry is coated on a copper foil, and the single-sided active material surface density of the coating is 112.5 g / m 2 , and the double-sided active material surface density is 225.0 g / m 2 .

[0155] 5) Positive and negative electrode tab die cutting and lamination assembly: the positive and negative electrode tabs are die cut and laminated with a separator to prepare a 7+8 layer soft pack small cell, which is then packaged in an aluminum shell or an aluminum plastic film to make a battery. After liquid injection, the first charge and discharge is performed, and the battery design capacity is 1595 mAh.

[0156] 6) The positive electrode sodium supplementing battery liquid injection decomposition: after the liquid injection, the battery is subjected to formation using 0.05C constant current charging for 2h and 0.2C constant current charging for 3h, after the formation of SEI film, the battery is further charged to 4.0V using 0.005C current, so that the sodium supplementing agent of the sodium supplementing positive electrode active layer is fully decomposed and desodiated, and the battery is subjected to electrochemical sodium supplementing;

[0157] 10) Battery sorting: after the battery is subjected to air extraction sealing and aging for 24h, the battery is subjected to sorting, the sorting step is 1 / 3C constant current constant voltage charging to 4.0V, standing for 10min, 1 / 3C constant current discharging to 2.0V, recording the discharging capacity at this time as C0, and recording the OCV of the battery after standing for 24h.

[0158] Comparative Example 4

[0159] The preparation method of the secondary battery (the positive electrode is not supplemented with sodium, and the negative electrode is supplemented with sodium on both sides) comprises the following steps:

[0160] 1) Positive electrode tab preparation: 100 parts of iron-based Prussian white (Na2Fe[Fe(CN)6]), 2 parts of conductive agent and 2.2 parts of binder are mixed by NMP dissolution to prepare positive electrode slurry, the slurry is coated on aluminum foil, the active material single-sided density of the coating is 180g / m 2 , and the double-sided active material density is 360g / m 2 , and the positive electrode tab is prepared after rolling and die cutting;

[0161] 2) Negative electrode tab preparation: 100 parts of hard carbon material, 1 part of conductive agent and 5 parts of binder are uniformly mixed by deionized water dissolution to prepare negative electrode slurry, the slurry is coated on copper foil, the active material single-sided density of the coating is 102.1g / m 2 , and the double-sided active material density is 204.2g / m 2 .

[0162] 4) Double-sided sodium supplementing of negative electrode tab: after rolling, the negative electrode is supplemented with sodium powder or sodium foil on both sides, the sodium supplementing single-sided density is 4.2g / m 2 , and the total double-sided density is 8.4g / m 2 .

[0163] 5) Positive and negative electrode tab die cutting and laminating assembly: after the positive and negative electrode tabs are die cut, the tabs are laminated with the separator to prepare 7+8 layer soft package small cells, which are packaged in aluminum shells or aluminum plastic films to prepare batteries, after liquid injection, the batteries are subjected to first-time charging and discharging, and the design capacity of the battery is 1527mAh;

[0164] 6) Battery liquid injection formation: the battery after liquid injection is subjected to formation using 0.05C constant current charging for 2h and 0.2C constant current charging for 3h;

[0165] 7) Battery sorting: After the battery is subjected to air extraction sealing aging for 24 h, it is subjected to capacity grading, and the capacity grading process is 1 / 3 C constant current constant voltage charging to 4.0 V, standing for 10 min, 1 / 3 C constant current discharging to 2.0 V, recording the discharge capacity at this time as C0, and recording the OCV of the battery after standing for 24 h.

[0166] Comparative Example 5

[0167] The preparation method of the secondary battery (sodium is not supplemented on the positive electrode, and sodium is supplemented on both sides of the negative electrode) comprises the following steps:

[0168] 1) Preparation of positive electrode sheet: 100 parts of iron-based Prussian white (Na2Fe[Fe(CN)6]), 2 parts of conductive agent and 2.2 parts of binder are mixed by NMP dissolution to prepare positive electrode slurry, the slurry is coated on aluminum foil, the active material single-sided density of the coating is 180 g / m 2 , and the double-sided surface density is 360 g / m 2 . After rolling and die cutting, the positive electrode sheet is prepared;

[0169] 2) Preparation of negative electrode sheet: 100 parts of hard carbon material, 1 part of conductive agent and 5 parts of binder are uniformly mixed by deionized water dissolution to prepare negative electrode slurry, the slurry is coated on copper foil, the active material single-sided density of the coating is 112.5 g / m 2 , and the double-sided active material surface density is 225.0 g / m 2 .

[0170] 4) Double-sided sodium supplementation of negative electrode sheet: after rolling, sodium powder or sodium foil is supplemented on both sides of the negative electrode, the single-sided sodium supplementation density is 8.0 g / m 2 , and the total double-sided sodium supplementation density is 16.0 g / m 2 .

[0171] 5) Die cutting, laminating and assembling of positive and negative electrode sheets: after die cutting, the positive and negative electrode sheets are laminated with the separator to prepare 7+8 layer soft package small cells, which are then packaged in aluminum shells or aluminum plastic films to prepare batteries. After liquid injection, the first charge and discharge are performed, and the design capacity of the battery is 1595 mAh;

[0172] 6) Battery liquid injection and formation: the battery after liquid injection is subjected to formation by using 0.05 C constant current charging for 2 h and 0.2 C constant current charging for 3 h;

[0173] 7) Battery sorting: after the battery is subjected to air extraction sealing aging for 24 h, it is subjected to capacity grading, and the capacity grading process is 1 / 3 C constant current constant voltage charging to 4.0 V, standing for 10 min, 1 / 3 C constant current discharging to 2.0 V, recording the discharge capacity at this time as C0, and recording the OCV of the battery after standing for 24 h.

[0174] The batteries obtained in the above examples and comparative examples are subjected to performance tests, and the test results are shown in Table 1 below, wherein,

[0175] The negative electrode sheet heat production measurement method is: taking a negative electrode sheet with a diameter of 2 mm, weighing it, and then performing DSC test heat production, the test conditions are: Ar atmosphere, from room temperature to 180°, the heating rate is 5 K / min, and the unit heat production Q of the negative electrode sheet is calculated;

[0176] Cycle number: at 25 degrees, the formed battery is tested for cycles, and the test steps are as follows: 1) rest for 10 min; 2) 0.5C CC-CV to 4.3V 0.05C cut-off; 3) rest for 10 min; 4) 0.5C CC to 2.0V; 5) cycle the above steps n times until the retention rate reaches 80%, and record the cycle number;

[0177] Gas production test method: using the drainage method to test the unit Ah gas production V(ml / Ah, 80%SOH) of the battery before and after cycling;

[0178] Pre-stored sodium proportion: the pre-stored sodium proportion is the design value, which is equal to the ratio of the active sodium capacity not discharged after discharging to the full discharge capacity of the positive active layer.

[0179] The measurement method of A in the table: A value is the difference between the surface capacity of the positive sodium supplement agent and the negative sodium supplement agent, which satisfies A = p * x * a - b * s, wherein the total surface density of the positive active material (including the sodium supplement agent) is p, the single surface sodium supplement agent proportion is x, the specific capacity of the sodium supplement agent is a (the specific capacity of Na2NiO2 is a = 386 mAh / g); the surface density of the negative sodium supplement layer is s, and the specific capacity is b (the specific capacity of Na is b = 1000 mAh / g). The value is obtained by using the discharge test to obtain the specific capacity of the sodium supplement agent of the positive and negative electrodes respectively. The value between -100 and +100 indicates that the sodium supplement amount of the positive and negative electrodes matches, and the battery design is reasonable.

[0180] Table 1

[0181]

[0182]

[0183] As can be seen from the data in the above table, the batteries in Embodiment 1 to Embodiment 8 of the present application have good battery capacity and cycle number, that is, the sodium supplement method of the present application does not cause adverse effects on the battery capacity and cycle number, and even a more appropriate sodium supplement amount can help to improve the battery capacity and cycle number, such as Embodiment 4 to Embodiment 7, etc. Compared with the negative electrode double-side sodium supplement scheme in Comparative Examples 4 and 5, the sodium supplement method of Embodiment 1 to Embodiment 8 can significantly reduce the heating phenomenon after pre-sodium of the negative electrode sheet. As can be seen from the comparison between Embodiment 4 and Comparative Example 4, the sodium supplement scheme of the present application on the single-side negative electrode can well reduce the heating phenomenon after pre-sodium of the negative electrode sheet. In addition, in Comparative Examples 1 to Comparative Example 3, no sodium supplement is arranged on both sides of the negative electrode, so there is almost no heating phenomenon after pre-sodium. Compared with the double-side positive electrode sodium supplement scheme in Comparative Examples 2 and 3, the sodium supplement method of Embodiment 1 to Embodiment 8 can significantly alleviate the adverse phenomenon of “gas production in the cycle process” caused by the positive electrode sodium supplement. In addition, in Comparative Examples 4 and 5, no sodium supplement is arranged on the positive electrode, so the gas production is extremely low. Further, as can be seen from the data of the positive and negative electrode lithium supplement surface capacity difference A in the above embodiments, the above sodium supplement amounts of the positive and negative electrodes of the present application are matched. The pre-stored sodium proportion in the above embodiments is between 0-20%, so the battery of the present application has a more appropriate pre-stored sodium proportion.

[0184] The terms "first", "second", "third", etc. are used herein only to describe different instances, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the technical features indicated. Therefore, the features defined with "first", "second" can explicitly or implicitly include one or more of the features. In the description of the present application, the meaning of "a plurality of" is two or more, unless otherwise specifically limited.

[0185] In the description of the present application, the illustrative description of the terms "one embodiment", "some embodiments", "an example", "a specific example", or "some examples" means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In the present application, the illustrative description of the above terms is not necessarily directed to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. Furthermore, the skilled person in the art can combine and combine the different embodiments or examples described in the present application and the features of the different embodiments or examples without contradiction.

[0186] Although the embodiments of the present application have been shown and described above, it should be understood that the above embodiments are exemplary and cannot be understood as limiting the present application, and those skilled in the art can make changes, modifications, replacements and variations to the above embodiments within the scope of the present application.

Claims

1. An electric cell, characterized by, The positive electrode unit comprises a positive electrode current collector and a non-sodium-supplemented positive electrode active layer and a sodium-supplemented positive electrode active layer arranged on both sides of the positive electrode current collector respectively, and the negative electrode unit comprises a negative electrode current collector, a first negative electrode sheet and a second negative electrode sheet arranged on both sides of the negative electrode current collector respectively, and a negative electrode sodium-supplemented layer, wherein the negative electrode sodium-supplemented layer is arranged towards the non-sodium-supplemented positive electrode active layer in the positive electrode unit, and the sodium-supplemented positive electrode active layer is arranged towards the second negative electrode sheet in the negative electrode unit.

2. The electric cell of claim 1, wherein, Only one sodium-supplemented structure is included between two adjacent positive electrode current collectors and negative electrode current collectors, and the sodium-supplemented structure is the sodium-supplemented positive electrode active layer or the negative electrode sodium-supplemented layer.

3. The electric cell of claim 1, wherein, The sodium-supplementing agent in the sodium-supplemented positive electrode active layer comprises at least one of Na2NiO2, NaCrO2, Na2C2O4, Na3N, Na2S, Na3P, Na2CO3, NaNO2, Na2C4O4, Na2C6O6, and Na2C6H2O6, The negative electrode sodium-supplemented layer is a sodium foil and / or a sodium powder.

4. The battery cell of any one of claims 1-3, wherein, The content of the sodium-supplementing agent in the sodium-supplemented positive electrode active layer is less than or equal to 40% in terms of mass percentage based on the total mass of the non-sodium-supplemented positive electrode active layer and the sodium-supplemented positive electrode active layer.

5. The electric cell of claim 4, wherein, The content of the sodium-supplementing agent in the sodium-supplemented positive electrode active layer is 1.5-10% in terms of mass percentage based on the total mass of the non-sodium-supplemented positive electrode active layer and the sodium-supplemented positive electrode active layer.

6. The electric cell of claim 4, wherein, For the sodium-supplementing positive electrode active layer, the areal density of the sodium supplementing agent is 1 g / m 2 ~ 18 g / m 2 .

7. The electric cell of claim 6, wherein, For the sodium-supplementing positive electrode active layer, the areal density of the sodium supplementing agent is 4 g / m 2 ~ 16 g / m 2 .

8. The battery cell of any one of claims 1-3, wherein, The face density of the negative sodium supplement layer is 0.5g / m 2 ~ 10g / m 2 .

9. The electric cell of claim 8, wherein, The face density of the negative sodium supplement layer is 1 g / m 2 ~ 6 g / m 2 .

10. The battery cell of any one of claims 1-3, wherein, The effective active material in the non-sodium-supplemented positive electrode active layer and the sodium-supplemented positive electrode active layer is a transition metal oxide Na e MO2, Prussian blue compound Na f M1[M2(CN)6] and polyanion compound Na d M g (X a O b ) c Z h at least one of, wherein M, M1 and M2 are one or more of transition metal atoms, X is one or more of Si, S, P, As, B, Mo, W, Ge elements, and Z is one or more of F and OH; The effective active material of the first negative electrode sheet and the second negative electrode sheet is at least one of natural graphite, artificial graphite, soft carbon, hard carbon, mesocarbon microbeads, nano-carbon, carbon fiber, silicon negative electrode material, and sodium-embedded alloy.

11. A secondary battery characterized by comprising: The battery cell comprises the battery cell according to any one of claims 1-10.

12. An electrical device, characterized by The secondary battery comprises the secondary battery according to claim 11.

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