Battery and energy storage device

Abstract

The application relates to the technical field of batteries, in particular to a battery and an energy storage device. The battery comprises: a battery cell; a termination adhesive tape, which is bonded to a termination position of the battery cell and comprises a base material and a bonding layer arranged on the base material, wherein the base material is a polyethylene terephthalate base material; and a non-aqueous electrolyte, which is used for infiltrating the battery cell with the bonded termination adhesive tape and comprises: sodium hexafluorophosphate with a concentration of 0.5-1.2 mol / L; an organic solvent, wherein the organic solvent comprises a first organic solvent and a second organic solvent, the first organic solvent comprises a carbonate and / or a carboxylic acid ester, the second organic solvent comprises an ether solvent, the mass percentage of the first organic solvent in the non-aqueous electrolyte is 45-70 wt%, and the mass percentage of the second organic solvent in the non-aqueous electrolyte is 15-40 wt%; and an additive, wherein the additive comprises a first additive, the first additive comprises sodium difluorophosphate, and the mass percentage of the first additive in the non-aqueous electrolyte is 0.4-1.2 wt%.

Description

Technical Field

[0001] This application relates to the field of battery technology, and in particular to a battery and energy storage device. Background Technology

[0002] Termination tape refers to the tape used in the battery manufacturing process to adhere to the termination parts of the battery cell, etc. It is usually used for insulation and fixation, and is an important structure to ensure the safe and stable transportation and use of the battery.

[0003] Current termination tapes are typically made by setting an adhesive layer on an organic substrate. However, the organic materials chosen for the substrate may decompose after being immersed in some organic solvent-based electrolytes for a period of time due to a reaction. This phenomenon can cause battery self-discharge, adversely affecting the battery's electrochemical performance, shortening its lifespan, and even posing potential safety hazards. Summary of the Invention

[0004] To address the aforementioned technical problems, this application discloses a battery and energy storage device to solve the problem of unstable termination tape using polyethylene terephthalate as the substrate and the resulting series of effects on the battery.

[0005] In a first aspect, this application provides a battery, the battery comprising:

[0006] Battery cell;

[0007] Termination tape, the termination tape being adhered to the termination portion of the battery cell, the termination tape comprising a substrate and an adhesive layer disposed on the substrate, the substrate being a polyethylene terephthalate substrate;

[0008] A non-aqueous electrolyte, used to impregnate the battery cell to which the termination tape is bonded, the non-aqueous electrolyte comprising:

[0009] Sodium salt, including sodium hexafluorophosphate, wherein the concentration of the sodium salt is 0.5 mol / L to 1.2 mol / L;

[0010] The organic solvent includes a first organic solvent and a second organic solvent, wherein the first organic solvent includes carbonates and / or carboxylic acid esters, and the second organic solvent includes ether solvents, wherein the first organic solvent has a mass percentage of 45 wt% to 70 wt% in the non-aqueous electrolyte, and the second organic solvent has a mass percentage of 15 wt% to 40 wt% in the non-aqueous electrolyte;

[0011] The additive includes a first additive, which includes sodium difluorophosphate, and the first additive is present in the non-aqueous electrolyte at a mass percentage of 0.4 wt% to 1.2 wt%.

[0012] Furthermore, the first additive is present in the non-aqueous electrolyte at a mass percentage of 0.4 wt% to 0.8 wt%.

[0013] Furthermore, the second organic solvent has a mass percentage of 15 wt% to 20 wt% in the non-aqueous electrolyte.

[0014] Optionally, the ether solvent includes one or more of tetrahydrofuran, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, diethylene glycol methyl ethyl ether, or diethylene glycol diethyl ether.

[0015] Preferably, the ether solvent is tetrahydrofuran.

[0016] Optionally, when the first organic solvent includes a carbonate, the carbonate includes one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, ethyl methyl carbonate, or diethyl carbonate.

[0017] Optionally, when the first organic solvent comprises a carboxylic acid ester, the carboxylic acid ester comprises one or more of methyl acetate, ethyl acetate, ethyl propionate, ethyl butyrate, propyl acetate, or methyl propionate.

[0018] Furthermore, in the non-aqueous electrolyte, the additive further includes a second additive, which includes one or more of fluoroethylene carbonate, vinylene carbonate, 1,3-propanesulfonate lactone, 1,3-propenesulfonate lactone, ethylene sulfate, or ethylene sulfite, and the mass percentage of the second additive in the non-aqueous electrolyte is 0.01 wt% to 10 wt%.

[0019] Optionally, the second additive includes fluoroethylene carbonate.

[0020] Furthermore, the termination tape is adhered to the middle region of the termination portion of the battery cell.

[0021] Secondly, embodiments of this application provide an energy storage device, the energy storage device comprising the battery as described in the first aspect.

[0022] Compared with the prior art, the beneficial effects of this application are as follows:

[0023] This application adds sodium difluorophosphate at a specific mass percentage as a first additive to the non-aqueous electrolyte of the battery. The organic solvents include not only carbonates and / or carboxylic esters but also ether solvents. Through the synergistic effect of the ether solvents and sodium difluorophosphate, the stability of the PET-based termination tape in the aforementioned non-aqueous electrolyte can be improved, thereby increasing battery life and reducing safety hazards during battery use. Furthermore, it also achieves good initial coulombic efficiency, superior low-temperature cycling performance, and rate performance. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 This is a schematic diagram of the structure of the battery cell in the embodiment of this application;

[0026] Figure 2 This is a schematic diagram of the structure of a residential energy storage system according to an embodiment of this application;

[0027] Figure 3 This is a schematic diagram of the structure of an energy storage system according to an embodiment of this application;

[0028] Figure 4 This is an image showing the appearance of the termination tape of the embodiments and comparative examples of this application after being immersed in a non-aqueous electrolyte for the first day;

[0029] Figure 5 This is an image showing the appearance of the termination tape of the embodiments and comparative examples of this application after being immersed in a non-aqueous electrolyte for 20 days.

[0030] Figure 6 This is a diagram of the battery cells after disassembling the battery in Example 1;

[0031] Figure 7 This is a diagram of the battery cells after disassembling the battery in Comparative Example 1;

[0032] Figure 8 This is a diagram of the battery cells after disassembling the battery in Comparative Example 2;

[0033] Figure 9 The graphs show the AC impedance curves of the cells from Comparative Example 1, Comparative Example 2, and Example 1.

[0034] Reference numerals: 1. Battery cell; 2. Termination tape; 100. Energy storage system; 10. Energy storage device; 20. Power conversion device; 30. First user load; 40. Second user load; 50. High-voltage cable; 60. First power conversion device; 70. Second power conversion device. Detailed Implementation

[0035] In this application, the terms "upper," "lower," "left," "right," "front," "rear," "top," "bottom," "inner," "outer," "middle," "vertical," "horizontal," "lateral," and "longitudinal" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. These terms are primarily for the purpose of better describing this application and its embodiments, and are not intended to limit the indicated device, element, or component to having a specific orientation, or to be constructed and operated in a specific orientation.

[0036] Furthermore, in addition to indicating location or positional relationship, some of the aforementioned terms may also have other meanings. For example, the term "above" may also be used in some cases to indicate a certain dependency or connection relationship. Those skilled in the art can understand the specific meaning of these terms in this application based on the specific circumstances.

[0037] Furthermore, the terms "installation," "setup," "equipped with," "connection," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral structure; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium, or an internal connection between two devices, components, or parts. Those skilled in the art can understand the specific meaning of these terms in this application based on the specific circumstances.

[0038] Furthermore, the terms "first," "second," etc., are primarily used to distinguish different devices, elements, or components (which may be the same or different in specific type and construction), and are not intended to indicate or imply the relative importance or quantity of the indicated devices, elements, or components. Unless otherwise stated, "a plurality of" means two or more.

[0039] The technical solution of this application will be further described below with reference to the embodiments.

[0040] In batteries, termination tapes are typically made by using polyethylene terephthalate (PET) as the substrate on an organic base material, and coating this substrate with an electrolyte-resistant adhesive layer. One type of organic base material is polyethylene terephthalate (PET), and this type of termination tape is widely used due to its good mechanical and electrical properties and reasonable cost.

[0041] However, during the research process, the applicant unexpectedly discovered that the PET-based termination tape was prone to reaction with certain types of electrolytes, leading to decreased stability of the PET-based termination tape. Specifically, after being soaked in a non-aqueous electrolyte using carbonates and / or carboxylic esters as organic solvents and sodium hexafluorophosphate as the sodium salt for a period of time, the PET-based termination tape exhibited flocculent fragmentation and discoloration. Further research revealed that the products generated during the film-forming reaction of carbonates and / or carboxylic esters in the non-aqueous electrolyte primarily caused the decomposition of the PET substrate, and the products generated during the hydrolysis of sodium hexafluorophosphate in the non-aqueous electrolyte also exacerbated the decomposition of the PET substrate.

[0042] Having creatively identified the root cause of the aforementioned problems, this application proposes an improved battery solution to address these issues. While using the aforementioned PET-based termination tape and a non-aqueous electrolyte employing carbonates and / or carboxylic esters as organic solvents and sodium hexafluorophosphate as the sodium salt, the electrolyte formulation is improved to specifically overcome the problem of the PET-based termination tape easily decomposing under the influence of carbonates and / or carboxylic esters and sodium hexafluorophosphate. This allows the PET-based termination tape to perform its adhesive function more stably, making this termination tape, with its superior mechanical and electrical properties and more reasonable cost, more widely applicable. Furthermore, the above improvements enable the battery to achieve good initial coulombic efficiency, low-temperature cycling performance, and rate performance, among other electrochemical properties.

[0043] Firstly, embodiments of this application provide a battery to improve the problem of insufficient stability of the PET substrate in the termination tape.

[0044] Combination Figure 1 As shown, Figure 1 This is a schematic diagram of the battery cell structure in the embodiment of the application. The battery in this embodiment includes a battery cell 1, a termination tape 2, and a non-aqueous electrolyte.

[0045] The battery cell 1 includes a positive electrode, a negative electrode, and a separator. The separator can be placed between the positive and negative electrode sheets. The battery cell 1 is manufactured through a winding process or a stacking process. Taking the battery cell 1 manufactured by the winding process as an example, the end of the winding can be understood as the termination part of the battery cell 1. At this termination part, termination tape 2 needs to be adhered to firmly fix the assembly of the positive electrode, separator, and negative electrode and provide a certain degree of insulation. In addition, this battery is preferably a sodium-ion battery.

[0046] The battery termination tape 2 includes a substrate and an adhesive layer disposed on the substrate. For example, an electrolyte-resistant polyacrylic adhesive layer is coated onto the substrate to obtain the termination tape 2. In this embodiment, the substrate of the termination tape 2 is a polyethylene terephthalate substrate, i.e., a PET substrate.

[0047] Since the battery cell with the termination tape is immersed in the electrolyte, the termination tape is inevitably also immersed in the electrolyte. As mentioned above, the applicant found that the termination tape using PET substrate is unstable after being immersed in a non-aqueous electrolyte using carbonate and / or carboxylic esters as organic solvents and sodium hexafluorophosphate as sodium salt, which can cause battery self-discharge, shorten battery life, and pose safety hazards. Therefore, the embodiments of this application have improved the non-aqueous electrolyte of the battery, so that the termination tape with PET substrate still has high stability after being immersed in a non-aqueous electrolyte using carbonate and / or carboxylic esters as organic solvents and sodium hexafluorophosphate as sodium salt, and on this basis, it also has good initial coulombic efficiency, better low-temperature cycling performance, and rate performance.

[0048] In this embodiment, a non-aqueous electrolyte is used to impregnate the battery cell bonded with termination tape. The non-aqueous electrolyte comprises:

[0049] Sodium salt, including sodium hexafluorophosphate, wherein the concentration of the sodium salt is 0.5 mol / L to 1.2 mol / L;

[0050] The organic solvent includes a first organic solvent and a second organic solvent, wherein the first organic solvent includes carbonates and / or carboxylic acid esters, and the second organic solvent includes ether solvents, wherein the first organic solvent has a mass percentage of 45 wt% to 70 wt% in the non-aqueous electrolyte, and the second organic solvent has a mass percentage of 15 wt% to 40 wt% in the non-aqueous electrolyte;

[0051] The additive includes a first additive, which includes sodium difluorophosphate, and the first additive is present in the non-aqueous electrolyte at a mass percentage of 0.4 wt% to 1.2 wt%.

[0052] In the aforementioned non-aqueous electrolyte, a specific mass percentage of sodium difluorophosphate is added as the first additive. In addition to carbonates and / or carboxylic esters, the organic solvent also includes a specific mass percentage of ether solvents. Through the synergistic effect of these ether solvents and sodium difluorophosphate, the stability of the PET-based termination tape in the non-aqueous electrolyte can be improved, thereby increasing battery life and reducing safety hazards during battery use. Furthermore, it also exhibits good initial coulombic efficiency, superior low-temperature cycling performance, and rate performance.

[0053] On the one hand, the first additive, sodium difluorophosphate, can inhibit the hydrolysis of sodium hexafluorophosphate, thereby suppressing the decomposition of the PET substrate. The reason why the hydrolysis of sodium hexafluorophosphate affects the PET substrate is that its hydrolysis product, phosphorus pentafluoride, is a strong Lewis acid with high reactivity. It can catalyze the polymerization of olefins, generating fluorinated polymers, causing electrolyte discoloration and accelerating PET decomposition. Therefore, in this embodiment, by using the first additive, sodium difluorophosphate, to inhibit the hydrolysis of sodium hexafluorophosphate, the generation of phosphorus pentafluoride can be suppressed, thus effectively inhibiting the decomposition of the PET substrate.

[0054] On the other hand, ether solvents react with Na in non-aqueous electrolytes. + After combination, the LUMO energy level is significantly reduced, allowing ether solvents to preferentially participate in the film-forming reaction at both the positive and negative electrodes compared to ester solvents (carbonates and / or carboxylic esters). This preferential participation of ether solvents in film formation results in a dense SEI film, effectively suppressing the decomposition of the PET substrate caused by the reaction of carbonates and / or carboxylic esters. Furthermore, because the first additive, sodium difluorophosphate, has a lower redox potential than organic solvents and sodium hexafluorophosphate, it can participate in the formation of a more stable SEI film. Therefore, the combined effect of sodium difluorophosphate and ether solvents effectively inhibits the decomposition and film-forming reaction of carbonates and / or carboxylic esters, thereby suppressing the decomposition of the PET substrate.

[0055] The reason why carbonates and / or carboxylic esters affect PET substrates is that they decompose in the presence of trace amounts of water to produce alcohols, which are then reduced at the negative electrode to form sodium alkoxides. These alcohols and sodium alkoxides participate in the film-forming reaction at the negative electrode. However, the generation of alcohols and sodium alkoxides causes the PET substrate in the termination tape to depolymerize into esters containing benzene rings under their influence. For example, taking dimethyl carbonate as an example, its hydrolysis produces methanol and carbon dioxide, which are then reduced at the negative electrode to form sodium methoxide and carbon monoxide. Methanol and sodium methoxide promote the depolymerization of PET into dimethyl terephthalate. The newly formed dimethyl terephthalate can diffuse and shuttle between the positive and negative electrodes, transferring electrons through redox reactions. This causes sodium ions to transfer from the negative electrode to the positive electrode in the absence of external current, shortening battery life and posing serious safety hazards.

[0056] As can be seen, the embodiments of this application, through the combined action of ether solvents and sodium difluorophosphate, can inhibit the decomposition and film formation of carbonates and / or carboxylic esters, thereby inhibiting the generation of alcohols and sodium alkoxides, and effectively suppressing the decomposition of PET under the action of alcohols and sodium alkoxides. Furthermore, the inhibitory effect of sodium difluorophosphate on the hydrolysis of sodium hexafluorophosphate further improves the stability of the PET substrate of the terminating tape.

[0057] Building upon this foundation, this application introduces an appropriate amount of ether solvent and sodium difluorophosphate as the first additive to form a thin and dense solid electrolyte interface layer. This facilitates the reduction of charge transfer resistance and minimizes the consumption of other additives in the non-aqueous electrolyte. Furthermore, because sodium difluorophosphate inhibits the hydrolysis of sodium hexafluorophosphate and simultaneously provides anions that bind with organic solvent molecules, more sodium ions from the sodium salt can detach from the first solvation shell, enhancing the desolvation effect of the non-aqueous electrolyte. This results in higher initial coulombic efficiency, superior low-temperature cycling performance, and rate performance. In particular, increasing the amount of ether solvent effectively improves the battery's low-temperature cycling performance.

[0058] The first organic solvent has a mass percentage of 45 wt% to 70 wt% in the non-aqueous electrolyte, including any value within this range. For example, the mass percentage of the first organic solvent in the non-aqueous electrolyte is 45 wt%, 50 wt%, 55 wt%, 60 wt%, 65 wt%, or 70 wt%. The second organic solvent has a mass percentage of 15 wt% to 40 wt% in the non-aqueous electrolyte, including any value within this range. For example, the mass percentage of the second organic solvent in the non-aqueous electrolyte is 15 wt%, 18 wt%, 20 wt%, 25 wt%, 30 wt%, 35 wt%, or 40 wt%. The first additive has a mass percentage of 0.4 wt% to 1.2 wt% in the non-aqueous electrolyte, including any value within this range. For example, the first additive is present in the non-aqueous electrolyte at a mass percentage of 0.4 wt%, 0.5 wt%, 0.6 wt%, 0.7 wt%, 0.8 wt%, 0.9 wt%, 1.0 wt%, 1.1 wt%, or 1.2 wt%.

[0059] Preferably, the mass percentage of the first additive in the non-aqueous electrolyte is 0.4 wt% to 0.8 wt%. The amount of sodium difluorophosphate is further controlled within this range. This is because sodium difluorophosphate within this range has better solubility in the non-aqueous electrolyte system, and because it works better with ether solvents to inhibit the reaction of the PET substrate, thus improving the stability of the PET substrate in the termination tape. Furthermore, further controlling the mass percentage of the first additive in the non-aqueous electrolyte to 0.6 wt% to 0.8 wt% can optimize the battery's initial coulombic efficiency, low-temperature cycle stability, and rate performance, especially significantly improving the battery's rate performance.

[0060] Preferably, the second organic solvent has a mass percentage of 15wt% to 20wt% in the non-aqueous electrolyte. Further controlling the amount of ether solvent within this range can better suppress the reaction of the PET substrate in the terminating tape, thus further improving the stability of the PET substrate in the terminating tape.

[0061] Optionally, the ether solvent includes one or more of tetrahydrofuran, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, diethylene glycol methyl ethyl ether, or diethylene glycol diethyl ether. These ether solvents, in synergy with sodium difluorophosphate, can preferentially participate in the film-forming reaction at the negative electrode before carbonates and / or carboxylic esters, forming a denser SEI film. This achieves the purpose of inhibiting carbonates and / or carboxylic esters from participating in the film-forming reaction and generating alcohols and sodium alkoxides.

[0062] Preferably, the ether solvent is tetrahydrofuran. Because tetrahydrofuran has a stronger desolvation effect, it can preferentially bind with sodium ions at the first solvation shell, serving as the main component in the formation of the SEI film, thereby more effectively inhibiting further reactions of carbonate and / or carboxylic acid ester solvents.

[0063] It is understood that the solvation shell refers to the solvent molecule adsorption layer formed on the electrode surface by solvent molecules in the battery. The layer of solvent molecules immediately adjacent to the electrode surface is the first solvation shell, and a second solvation shell exists outside the first. In the solvation shell, it is difficult for sodium ions in the non-aqueous electrolyte to detach from the solvent after binding with the solvent molecules. However, in this application embodiment, tetrahydrofuran is preferably used as an ether solvent, and its strong desolvation effect facilitates the release of sodium ions from the solvent. Thus, because tetrahydrofuran can preferentially contact sodium ions at the first solvation shell, it can preferentially participate in the reaction to form the SEI film on the negative electrode surface, thereby better suppressing the hydrolysis of carbonates and / or carboxylic esters. Through effective suppression of carbonate and / or carboxylic ester hydrolysis, the ultimate goal of inhibiting the reaction of the PET substrate and improving the stability of the PET substrate is achieved.

[0064] Optionally, when the first organic solvent includes a carbonate, the carbonate includes one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, ethyl methyl carbonate, or diethyl carbonate.

[0065] Optionally, when the first organic solvent includes a carboxylic acid ester, the carboxylic acid ester includes one or more of methyl acetate, ethyl acetate, ethyl propionate, ethyl butyrate, propyl acetate, or methyl propionate.

[0066] These ester-based organic solvents possess excellent solubility and stability, are effectively compatible with other components of non-aqueous electrolytes, and do not readily react with each other, thus exhibiting broad applicability and suitability for various batteries. Although the decomposition products of these ester-based organic solvents under trace amounts of water can lead to depolymerization of the PET substrate, the present application incorporates ether-based solvents as a second organic solvent in the non-aqueous electrolyte and uses a specific amount of sodium difluorophosphate as a first additive, thereby compensating for the shortcomings of these ester-based organic solvents and reducing the limitations on their application.

[0067] It should be noted that trace water refers to a very small amount of water contained in the electrolyte or battery. This water may be residual moisture from the raw materials or caused by moisture adsorption during the preparation process. Although various methods are used to remove moisture during the preparation of non-aqueous electrolytes, it is impossible to remove all moisture. Therefore, even for non-aqueous electrolytes, the presence of trace water is reasonable and unavoidable.

[0068] Furthermore, in the non-aqueous electrolyte of this application embodiment, the additive further includes a second additive, which includes one or more of fluoroethylene carbonate, vinylene carbonate, 1,3-propanesulfonate lactone, 1,3-propenesulfonate lactone, vinyl sulfate, or vinyl sulfite. The mass percentage of the second additive in the non-aqueous electrolyte is 0.01 wt% to 10 wt%. For example, the mass percentage of the second additive in the non-aqueous electrolyte is 0.01 wt%, 0.05 wt%, 0.1 wt%, 0.5 wt%, 1 wt%, 2 wt%, 3 wt%, 5 wt%, 8 wt%, 9 wt%, or 10 wt%. The above-mentioned second additive, as a film-forming additive, can assist the first additive and promote a better film-forming effect.

[0069] Preferably, the second additive comprises fluoroethylene carbonate.

[0070] When the first additive, sodium difluorophosphate, promotes the participation of ether solvents in the electrode film-forming reaction preferentially over carbonates and / or carboxylic esters, fluoroethylene carbonate can also participate in the film-forming reaction preferentially over carbonates and / or carboxylic esters. Therefore, it can further suppress the impact of carbonate and / or carboxylic ester decomposition on the PET substrate in the termination tape.

[0071] Furthermore, the battery cell in this embodiment can be packaged in a hard shell, such as a hard plastic shell, aluminum shell, or steel shell; or it can be a soft pack, such as a polypropylene plastic outer packaging. Preferably, the battery is a soft pack battery. Soft pack batteries are generally more flexible, and the PET-based termination tape has better matching toughness and adhesion to soft pack batteries, allowing the termination tape to adhere tightly to the termination part of the battery cell, providing effective insulation and protection. Therefore, the improvements to the non-aqueous electrolyte in this embodiment better meet the requirements for the use of PET-based termination tape in soft pack batteries.

[0072] Furthermore, there are several ways to apply the termination tape to the termination point of the battery cell. Taking a pouch battery as an example, in one optional embodiment, a complete strip of termination tape can be applied along the height of the cell to the termination point, thereby securing the termination point. In another optional embodiment, see [link to relevant documentation]. Figure 1 Multiple sections of termination tape 2 can be pasted onto the termination portion of the battery cell 1. For example, termination tape 2 can be pasted onto the middle, top, and bottom areas of the termination portion, with the pasting direction of the termination tape 2 perpendicular to the height direction of the battery cell 1. This pasting method can make the termination portion of the battery cell 1 more securely attached.

[0073] Preferably, a termination tape is bonded to the middle region of the termination portion of the battery cell. For termination portions requiring secure bonding, the middle region is the most important and crucial location. Only when the middle region is firmly bonded with the termination tape can the stability and reliability of the battery cell be guaranteed. Although the applicant discovered during research that the termination tape bonded to the middle region of the termination portion reacted more severely (e.g., more noticeable discoloration) after immersion in a non-aqueous electrolyte compared to the termination tape bonded to the top and bottom regions of the termination portion, the embodiments of this application incorporate an ether solvent as a second organic solvent in the non-aqueous electrolyte and use a specific amount of sodium difluorophosphate as a first additive. This ensures the performance stability of the PET-based termination tape in the middle region of the termination portion, thereby guaranteeing the reliability of the bonding to the middle region of the termination portion.

[0074] Secondly, embodiments of this application provide an energy storage device, which includes a battery as described in the first aspect.

[0075] Taking electrochemical energy storage as an example, this application provides an energy storage device. The energy storage device is equipped with a set of chemical batteries. It mainly uses the chemical elements in the batteries as energy storage medium. The charging and discharging process is accompanied by the chemical reaction or change of the energy storage medium. Simply put, the electrical energy generated by wind and solar energy is stored in the chemical batteries. When the use of external electrical energy reaches its peak, the stored electricity is released for use, or transferred to places with a shortage of electricity for use.

[0076] Current energy storage applications are quite widespread, including generation-side energy storage, grid-side energy storage, and consumption-side energy storage. The corresponding types of energy storage devices include:

[0077] (1) Large-scale energy storage power stations applied to wind power and photovoltaic power stations can assist renewable energy power generation in meeting grid connection requirements and improve the utilization rate of renewable energy. As a high-quality active / reactive power regulation power source on the power supply side, energy storage power stations can achieve load matching of power in time and space, enhance the absorption capacity of renewable energy, reduce instantaneous power changes, reduce the impact on the power grid, improve the absorption of new energy power generation, and are of great significance in power grid system backup, alleviating peak load power supply pressure and peak regulation and frequency regulation.

[0078] (2) Energy storage containers applied on the grid side mainly function as peak shaving, frequency regulation and grid congestion relief. In terms of peak shaving, they can realize peak shaving and valley filling of electricity load, that is, charging the energy storage battery when the electricity load is low and releasing the stored electricity during the peak electricity load period, thereby achieving a balance between power production and consumption.

[0079] (3) Small energy storage cabinets applied to the electricity consumption side mainly function as self-consumption of electricity, peak-valley price arbitrage, capacity cost management, and improvement of power supply reliability. Depending on the application scenario, electricity consumption side energy storage can be divided into industrial and commercial energy storage cabinets, household energy storage devices, energy storage charging piles, etc., which are generally used in conjunction with distributed photovoltaics. Industrial and commercial users can use energy storage for peak-valley price arbitrage and capacity cost management. In the electricity market implementing peak-valley pricing, by charging the energy storage system when the electricity price is low and discharging the energy storage system when the electricity price is high, peak-valley price arbitrage can be achieved, reducing electricity costs. In addition, industrial enterprises subject to two-part tariffs can use energy storage systems to store energy during off-peak hours and discharge during peak loads, thereby reducing peak power and the maximum demand declared, achieving the goal of reducing capacity charges. Household photovoltaics with energy storage can improve the level of self-consumption of electricity. Due to high electricity prices and poor power supply stability, the demand for household photovoltaic installations is driven. Given that photovoltaic power generation occurs during the day, while user load is generally higher at night, configuring energy storage can better utilize photovoltaic power, improve self-consumption levels, and reduce electricity costs. Furthermore, energy storage is needed in areas such as communication base stations and data centers for backup power.

[0080] Please see Figure 2 , Figure 2This is a schematic diagram of a residential energy storage system 100 according to an embodiment of this application. The residential energy storage system 100 includes a power conversion device 20 (photovoltaic panel), a first user load 30 (streetlight), a second user load 40 (e.g., household appliances such as air conditioners), and an energy storage device 10. The energy storage device 10 is a small energy storage box that can be wall-mounted to an outdoor wall. Specifically, the photovoltaic panel can convert solar energy into electrical energy during periods of low electricity prices, and the energy storage device 10 stores this electrical energy and supplies it to streetlights and household appliances during peak electricity prices, or provides power during power outages / power interruptions.

[0081] Please see Figure 3 , Figure 3 This is a schematic diagram of the structure of an energy storage system 100 according to an embodiment of this application, and this application Figure 6 The embodiments are illustrated using a shared energy storage scenario on the generation / distribution side as an example. The energy storage device 10 of this application is not limited to the energy storage scenario on the generation / distribution side.

[0082] This application provides an energy storage system 100, which includes a high-voltage cable 50, a first power conversion device 60, a second power conversion device 70, and the energy storage device 10 provided in this application. During power generation, the first power conversion device 60 and the second power conversion device 70 convert other forms of energy into electrical energy, which is then connected to the high-voltage cable and supplied to the power consumption side of the distribution network. When the power load is low and the first power conversion device 60 and the second power conversion device 70 generate excess power, the excess electricity is stored in the energy storage device 10, reducing wind and solar curtailment rates and improving the absorption of new energy power generation. When the power load is high, the power grid issues an instruction to transmit the electricity stored in the energy storage device 10, along with the high-voltage cable 50, in a grid-connected mode to supply power to the power consumption side. This provides various services for power grid operation, such as peak shaving, frequency regulation, and backup, fully leveraging the peak shaving function of the power grid, promoting peak shaving and valley filling, and alleviating the power supply pressure on the power grid.

[0083] Optionally, the first power conversion device 60 and the second power conversion device 70 can convert at least one of solar energy, light energy, wind energy, thermal energy, tidal energy, biomass energy and mechanical energy into electrical energy.

[0084] The number of energy storage devices 10 can be multiple, and the multiple energy storage devices 10 can be connected in series or in parallel. The multiple energy storage devices 10 are supported and electrically connected by an isolation plate (not shown). In this embodiment, "multiple" means two or more. An energy storage box can also be provided on the outside of the energy storage device 10 to house the energy storage device 10.

[0085] Optionally, the energy storage device 10 may include, but is not limited to, a single battery cell, a battery module, a battery pack, or a battery system. The actual application form of the energy storage device 10 provided in this application embodiment may be, but is not limited to, the listed products, and may also be other application forms. This application embodiment does not strictly limit the application form of the energy storage device 10. This application embodiment only uses a multi-cell battery as an example for illustration. When the energy storage device 10 is a single battery cell, the energy storage device 10 may be at least one of cylindrical batteries, prismatic batteries, etc.

[0086] The solution of this application will be further described below with reference to specific embodiments and experimental data.

[0087] Example 1

[0088] This embodiment provides a battery, which is specifically manufactured as follows.

[0089] <Termination of Adhesive Tape Preparation>

[0090] A non-aqueous electrolyte-resistant polyacrylic acid adhesive layer is coated onto a PET substrate to obtain a termination tape. The termination tape has the following dimensions: thickness 0.05mm × width 5.00mm.

[0091] <Preparation of Non-Aqueous Electrolyte>

[0092] A non-aqueous electrolyte is prepared by dissolving sodium hexafluorophosphate, sodium difluorophosphate (first additive), and fluoroethylene carbonate (second additive) in an organic solvent under an environment with a water content of less than 10 ppm. The organic solvent includes a first organic solvent and a second organic solvent; the first organic solvent comprises ethylene carbonate and diethyl carbonate, and the second organic solvent is tetrahydrofuran.

[0093] In this non-aqueous electrolyte, the concentration of sodium hexafluorophosphate is 1.0 mol / L (accounting for approximately 14% of the mass percentage of the non-aqueous electrolyte), the first additive sodium difluorophosphate accounts for 0.6 wt% of the mass percentage of the non-aqueous electrolyte, the second additive fluoroethylene carbonate accounts for 2.0 wt% of the mass percentage of the non-aqueous electrolyte, the ethylene carbonate accounts for approximately 25.02 wt% of the mass percentage of the non-aqueous electrolyte, the diethyl carbonate accounts for approximately 41.70 wt% of the mass percentage of the non-aqueous electrolyte, and the tetrahydrofuran accounts for approximately 16.68 wt% of the mass percentage of the non-aqueous electrolyte.

[0094] <Preparation of Positive Electrode>

[0095] Lithium iron phosphate, acetylene black, and polyvinylidene fluoride were dissolved in an N-methylpyrrolidone solution at a weight ratio of 97:1:2 to form a positive electrode slurry. Aluminum foil was used as the positive electrode current collector, and the positive electrode slurry was coated onto the current collector. After drying, cold pressing, and die-cutting, the positive electrode sheet was obtained.

[0096] <Preparation of Negative Electrode Sheets>

[0097] Graphite, acetylene black, styrene-butadiene rubber, and sodium carboxymethyl cellulose were dissolved in deionized water in a weight ratio of 95:2:2:1 and stirred to obtain a negative electrode slurry. Copper foil was used as the negative electrode current collector, and the negative electrode slurry was coated onto the current collector. After drying, cold pressing, and die cutting, the negative electrode sheet was obtained.

[0098] <Separator Preparation>

[0099] A porous polyethylene polymer film with a thickness of 16 μm was used as the diaphragm.

[0100] <Battery Assembly>

[0101] The positive electrode, battery separator, and negative electrode prepared above are stacked in sequence, with the separator positioned between the positive and negative electrode to act as an separator. The cells are then wound to obtain a bare cell. At the end of the cell (i.e., the tail end), the middle, top, and bottom areas of the end area are respectively glued with the aforementioned termination tape. The cell is then packaged in a polypropylene plastic outer packaging and injected with electrolyte. After vacuum sealing, settling, formation, and shaping processes, a soft-pack battery is obtained.

[0102] This application provides multiple quantities of Example 1 batteries for different performance tests, such as battery disassembly, component analysis, and charge / discharge testing.

[0103] Examples 2 to 4

[0104] Except for adjusting the amounts of the first additive, the first organic solvent, and the second organic solvent according to Table 1 in the <Preparation of Non-Aqueous Electrolyte>, the rest is the same as in Example 1.

[0105] Examples 5 to 8

[0106] Except for adjusting the amounts of the second and first organic solvents according to Table 1 in the <Preparation of Non-Aqueous Electrolyte>, the rest is the same as in Example 1.

[0107] Examples 9 to 10

[0108] Except for adjusting the type of ether solvent according to Table 1 in the <Preparation of Non-Aqueous Electrolyte> section, the rest is the same as in Example 1.

[0109] Examples 11-12

[0110] Except for adjusting the type of the first organic solvent according to Table 1 in the <Preparation of Non-Aqueous Electrolyte>, the rest is the same as in Example 1.

[0111] Examples 13 to 16

[0112] Except for adjusting the type of the second additive according to Table 1 in the <Preparation of Non-Aqueous Electrolyte>, the rest is the same as in Example 1.

[0113] Comparative Example 1

[0114] Except for the absence of sodium difluorophosphate and tetrahydrofuran in the <Preparation of Non-Aqueous Electrolyte>, the rest is the same as in Example 1. This application provides multiple quantities of Comparative Example 1 batteries for various performance tests, including battery disassembly, component analysis, and charge-discharge testing.

[0115] Comparative Example 2

[0116] Except for the absence of sodium difluorophosphate in the <Preparation of Non-Aqueous Electrolyte>, the rest is the same as in Example 1. This application provides multiple numbers of Comparative Example 2 batteries for various performance tests, including battery disassembly, component analysis, and charge / discharge testing.

[0117] Comparative Example 3

[0118] Except for the fact that tetrahydrofuran was not used in the <Preparation of Non-Aqueous Electrolyte>, the rest is the same as in Example 1.

[0119] Comparative Examples 4 to 5

[0120] Except for the <Preparation of Non-Aqueous Electrolyte>, where the mass percentage of sodium difluorophosphate was adjusted according to Table 1, the rest was the same as in Example 1.

[0121] Table 1. Non-aqueous electrolyte formulations for each embodiment and comparative example.

[0122]

[0123]

[0124]

[0125] In Table 1, " / " indicates that the relevant parameter does not exist.

[0126] Performance testing

[0127] Test 1: Stability Test of Termination Tape

[0128] The termination tape of Example 1 was immersed in the non-aqueous electrolyte prepared in Example 1, Comparative Example 1, and Comparative Example 2 for 20 days, and the degree of reaction of the termination tape was observed.

[0129] like Figure 4 and Figure 5The figures show the appearance of the termination tapes of Example 1, Comparative Example 1, and Comparative Example 2 after immersion in a non-aqueous electrolyte for the first and twentieth days, respectively. As can be seen from the figures, the termination tapes of Comparative Example 1 and Comparative Example 2 showed significant discoloration after immersion in the non-aqueous electrolyte over time, while the termination tape of Example 1 of this application maintained good stability and did not show significant discoloration after immersion in the non-aqueous electrolyte.

[0130] The batteries prepared in Example 1, Comparative Example 1, and Comparative Example 2 were disassembled after formation and capacity testing to observe the degree of reaction of the termination tape.

[0131] like Figures 6 to 8 The figures show the appearance of the battery cells after disassembly of the batteries from Example 1, Comparative Example 1, and Comparative Example 2, respectively. As can be seen from the figures, the termination tape at the termination point of the battery cell in Example 1 did not show significant changes and remained firmly attached to the termination point. In Comparative Example 1, the termination tape at the termination point of the battery cell clearly changed from blue to brown and then black, and the termination tape at the end area of ​​the termination point had detached. In Comparative Example 2, the termination tape at the termination point of the battery cell also showed some discoloration, especially in the middle area of ​​the termination point, indicating that the PET substrate of the termination tape had also undergone a certain degree of decomposition. Therefore, by comparison, it can be seen that the batteries of this application can effectively improve the stability of the PET substrate in the termination tape.

[0132] Test 2: Electrolyte Composition Analysis Test

[0133] The battery cells were disassembled after being processed and the electrolyte composition was characterized by gas chromatography-mass spectrometry, ion chromatography, and elemental analysis.

[0134] Table 2: Composition test results of non-aqueous electrolytes in Comparative Examples 1, 2, and 1

[0135] Element Comparative Example 1 Comparative Example 2 Example 1 Ethylene carbonate Detected Detected Detected diethyl carbonate Detected Detected Detected Tetrahydrofuran Not detected Detected Detected Dimethyl terephthalate Detected Detected Not detected Ethylene glycol Detected Detected Not detected Fluoride ions / ppm 1158.01 1185.18 1195.67 Chloride ions / ppm 4.85 7.72 6.13 difluorophosphate (ppm) / / 242.93 hexafluorophosphate / ppm 127586.33 128766.89 127336.1

[0136] The test results in Table 2 show that in Comparative Examples 1 and 2, after charging and discharging, dimethyl terephthalate and ethylene glycol were detected in the non-aqueous electrolyte. This indicates that ethylene carbonate and diethyl carbonate not only underwent hydrolysis, but their hydrolysis products also reacted with the PET substrate in the termination tape to generate dimethyl terephthalate. This can lead to depolymerization of the PET substrate, shorten battery life, and pose safety hazards. In contrast, the test results in Example 1 only showed difluorophosphate, with no dimethyl terephthalate or ethylene glycol detected. This indicates that the addition of ether solvents and sodium difluorophosphate effectively inhibited PET depolymerization and improved the stability of the termination tape.

[0137] Test 3: Battery Electrochemical Performance Test

[0138] AC impedance testing: Sinusoidal AC signals of different frequencies and amplitudes were applied to the batteries of Comparative Example 1, Comparative Example 2, and Example 1, respectively. The impedance change with the frequency of the sinusoidal wave was measured to study the electrode process dynamics and the interface phenomena of the electrode materials. All battery impedance tests were performed in the charging state (i.e., after completing the pre-test steps, the batteries were allowed to stand in the charging state for more than 3 hours to allow the potential to stabilize before testing). The AC voltage amplitude was 5mV, and the frequency range was 0.01Hz to 100kHz.

[0139] like Figure 9 The figure shows the AC impedance curves of the cells from Comparative Example 1, Comparative Example 2, and Example 1. The figure shows that the cell from Example 1 has a lower impedance, indicating that adding ether solvents to the non-aqueous electrolyte does indeed help reduce the charge transfer impedance of the cell, and the further addition of sodium difluorophosphate can further reduce the charge transfer impedance.

[0140] Charge-discharge test: Used to study the electrochemical performance of the battery, including cycle performance and rate performance. The voltage test range was 1.5–3.5V. All batteries were cycled three times at 1C. The initial coulombic efficiency was the ratio of the first discharge during the capacity grading stage to the sum of the first charge during the formation and capacity grading stages. The cycle performance test was performed at 1C. The rate test involved one charge-discharge cycle at different rates (0.5C, 1C, 2C, 3C, 4C). The test subjects were batteries from Examples 1 to 16, and Comparative Examples 1 to 5. The test results are shown in Table 3.

[0141] Table 3: Charge-discharge test results of the examples and comparative examples

[0142] First Coulomb Efficiency / % Capacity retention rate (%) after 100 cycles at -10℃ Capacity retention rate / % Example 1 81.6 82.3 97.8 Example 2 81.2 82.1 97.5 Example 3 81.7 82.5 97.9 Example 4 81.5 82.2 97.7 Example 5 81.8 84.5 97.9 Example 6 82.0 86.7 98.0 Example 7 82.3 88.2 97.9 Example 8 82.5 89.7 98.0 Example 9 81.0 80.5 96.9 Example 10 81.1 79.8 96.7 Example 11 81.7 60.7 97.0 Example 12 79.3 90.1 98.1 Example 13 81.0 81.7 96.4 Example 14 81.1 80.6 95.2 Example 15 81.0 80.7 96.3 Example 16 78.6 85.4 96.8 Comparative Example 1 77.3 75.3 88.6 Comparative Example 2 78.5 78.3 88.9 Comparative Example 3 79.1 78.0 90.5 Comparative Example 4 80.0 79.2 91.0 Comparative Example 5 80.3 79.5 91.2

[0143] By comparing the test results of Example 1 and Comparative Examples 1 to 3, it can be seen that the initial coulombic efficiency, low-temperature cycling stability, and capacity retention of Example 1 are all better than those of Comparative Examples 1 to 3. This indicates that compared with the scheme of adding only ether solvents, or only sodium difluorophosphate, or neither to the non-aqueous electrolyte, the present application example, by adding both ether solvents and sodium difluorophosphate to the non-aqueous electrolyte, can improve the stability of the PET substrate of the termination tape while maintaining a better initial coulombic efficiency, good low-temperature cycling performance, and excellent rate performance. In particular, the capacity decay after charge-discharge tests at different rates is very small, and the rate performance is excellent.

[0144] Comparing the test results of Example 1, Comparative Example 4, and Comparative Example 5, it can be seen that Example 1 exhibits superior initial coulombic efficiency, low-temperature cycling stability, and rate performance, especially with a more significant improvement in rate performance. This indicates that controlling the amount of sodium difluorophosphate used in the non-aqueous electrolyte within the range specified in this application helps maintain the stability of the PET substrate and other electrochemical properties while significantly improving the rate performance of the battery. Further comparison of Examples 1 to 4 shows that as the proportion of sodium difluorophosphate as the first additive in the non-aqueous electrolyte increases, the initial coulombic efficiency, low-temperature cycling stability, and rate performance generally show a trend of first increasing and then decreasing. When the mass percentage of sodium difluorophosphate in the non-aqueous electrolyte is in the range of 0.6wt% to 0.8wt%, the overall electrical performance is even better.

[0145] Comparing the test results of Examples 1, 5 to 8, it is evident that increasing the amount of ether solvent primarily promotes improved cycle performance under low-temperature conditions. This indicates that an appropriate amount of ether solvent can not only synergistically improve the stability of the PET substrate's termination tape with sodium difluorophosphate, but also further enhance the battery's low-temperature cycle stability. However, considering both room-temperature and high-temperature cycle performance of the battery cell, the preferred amount of ether solvent in this application is controlled between 15wt% and 20wt%.

[0146] Comparing the test results of Examples 1, 9, and 10, it is evident that when using different types of ether solvents as the second organic solvent, tetrahydrofuran is superior in comprehensively improving the battery's electrochemical performance. Comparing the test results of Examples 1, 11, and 12, it is evident that using different types of ester solvents as the first organic solvent has a significant impact on low-temperature cycling performance, especially increasing the mass fraction of ethylene carbonate, which significantly reduces low-temperature performance. In Example 12, a carboxylic acid ester organic solvent was used. Although its dielectric constant is lower, and its solubility for sodium salts and conductivity are not as good as carbonate organic solvents, resulting in an initial coulombic efficiency slightly below 80%, the combination of carboxylic acid ester organic solvents and ether solvents exhibits good kinetic performance, thus significantly improving the battery's low-temperature cycling performance. Comparing the test results of Examples 1, 13 to 15, it is evident that using fluoroethylene carbonate as the second additive is more effective. Further analysis of the test results of Example 16 reveals that while the rate performance is maintained to some extent without the second additive, both the initial coulombic efficiency and low-temperature cycling performance decrease. This demonstrates that adding the second additive while using sodium difluorophosphate as the first additive can further improve the overall electrical performance of the battery, while enhancing the stability of the PET substrate termination tape.

[0147] In summary, the embodiments of this application, by adding an ether solvent as a second organic solvent and sodium difluorophosphate as a first additive to a non-aqueous electrolyte with carbonate and / or carboxylic acid esters as the first organic solvent and sodium hexafluorophosphate as the sodium salt, not only improve the stability of the termination tape using PET substrate, but also promote the comprehensive improvement of the battery's low-temperature cycle performance, rate performance, and other electrochemical performance.

[0148] The battery and energy storage device disclosed in the embodiments of this application have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of this application. The description of the above embodiments is only for the purpose of helping to understand the technical solution and core ideas of this application. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this application. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A battery, characterized in that, The battery is a sodium-ion battery, and the battery includes: Battery cell; Termination tape, the termination tape being adhered to the termination portion of the battery cell, the termination tape comprising a substrate and an adhesive layer disposed on the substrate, the substrate being a polyethylene terephthalate substrate; A non-aqueous electrolyte, used to impregnate the battery cell to which the termination tape is bonded, the non-aqueous electrolyte comprising: Sodium salt, including sodium hexafluorophosphate, wherein the concentration of the sodium salt is 0.5 mol / L to 1.2 mol / L; The organic solvent comprises a first organic solvent and a second organic solvent, wherein the first organic solvent comprises carbonates and / or carboxylic acid esters, and the second organic solvent comprises ether solvents; the first organic solvent comprises 45 wt% to 70 wt% of the non-aqueous electrolyte, and the second organic solvent comprises 15 wt% to 40 wt% of the non-aqueous electrolyte; The additive includes a first additive, which includes sodium difluorophosphate, and the first additive is present in the non-aqueous electrolyte at a mass percentage of 0.4 wt% to 1.2 wt%.

2. The battery according to claim 1, characterized in that, The first additive has a mass percentage of 0.4 wt% to 0.8 wt% in the non-aqueous electrolyte.

3. The battery according to claim 1, characterized in that, The second organic solvent has a mass percentage of 15 wt% to 20 wt% in the non-aqueous electrolyte.

4. The battery according to claim 1, characterized in that, The ether solvents include one or more of tetrahydrofuran, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, diethylene glycol methyl ethyl ether, or diethylene glycol diethyl ether.

5. The battery according to claim 4, characterized in that, The ether solvent is tetrahydrofuran.

6. The battery according to claim 1, characterized in that, When the first organic solvent includes a carbonate, the carbonate includes one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, ethyl methyl carbonate, or diethyl carbonate. When the first organic solvent includes a carboxylic acid ester, the carboxylic acid ester includes one or more of methyl acetate, ethyl acetate, ethyl propionate, ethyl butyrate, propyl acetate, or methyl propionate.

7. The battery according to any one of claims 1 to 6, characterized in that, In the non-aqueous electrolyte, the additive further includes a second additive, which includes one or more of fluoroethylene carbonate, vinylene carbonate, 1,3-propanesulfonate lactone, 1,3-propenesulfonate lactone, ethylene sulfate, or ethylene sulfite, and the second additive has a mass percentage of 0.01 wt% to 10 wt% in the non-aqueous electrolyte.

8. The battery according to claim 7, characterized in that, The second additive includes fluoroethylene carbonate.

9. The battery according to any one of claims 1 to 6, characterized in that, The termination tape is adhered to the middle area of ​​the termination part of the battery cell.

10. An energy storage device, characterized in that, The energy storage device includes a battery as described in any one of claims 1 to 9.

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