Energy storage battery cooling liquid composition and preparation method thereof

Abstract

The invention discloses an energy storage battery cooling liquid composition and a preparation method thereof, a mineral type cooling liquid is prepared from base oil and an antioxidant, a light stabilizer and an anti-foaming agent which are added, the mineral type cooling liquid has a high flash point and good low-temperature fluidity, the cooling performance is effectively improved, and meanwhile, the energy storage battery cooling liquid composition has a good application prospect. In addition, the cooling liquid also has good insulativity, biodegradability and chemical stability, is low in biotoxicity, and can be suitable for immersed direct cooling of an electrochemical energy storage system.

Description

Technical Field

[0001] The invention relates to the technical field of electrochemical energy storage, and in particular to an immersion mineral coolant composition for a lithium ion battery and a preparation method thereof. Background Art

[0002] As a carrier of electric energy, the energy storage system can be used for grid peak regulation, effectively smoothing the volatility caused by large-scale renewable energy power generation connected to the grid, and improving the safety, economy and flexibility of grid operation. Energy storage technology has become the core key to building smart grids and realizing renewable energy power generation. At present, energy storage methods are mainly divided into mechanical energy storage, electrochemical energy storage, electromagnetic energy storage and phase change energy storage. Due to the advantages of low investment, high efficiency and simple maintenance, electrochemical energy storage has gradually become the mainstream development direction of new energy storage systems.

[0003] As an important part of the container energy storage system, the battery pack directly affects the performance of the entire system. Inside the container energy storage system, thousands of batteries are closely arranged, and the heat dissipation space is very limited. When the system is running, the battery charging and discharging will generate a lot of heat, and uneven heat accumulation will occur, causing temperature differences between batteries. Large temperature differences will cause inconsistent internal resistance and capacity of each battery. As time accumulates, some batteries will eventually be overcharged or over-discharged, affecting the life and performance of the entire system.

[0004] At present, the mainstream energy storage systems in the market mostly use air cooling and cold plate liquid cooling with water / ethylene glycol as the medium for battery cooling. The air cooling of energy storage batteries mostly adopts a thermal management solution that combines air conditioning with cooling duct air supply. Among them, the cooling duct mainly plays a drainage role, that is, to reasonably transport the cooling medium to the battery pack that needs to be cooled, but the main cooling medium of air cooling is air with a low thermal conductivity, which leads to low battery energy density and poor temperature uniformity of air-cooled energy storage systems, and poor adaptability to harsh environments such as salt spray and sand. Cold plate liquid cooling transfers the heat of the battery to the cooling medium (such as a water / ethylene glycol mixture) in the cold plate through the cooperation of the battery and the cold plate, and then the cooling medium dissipates the heat through the radiator. However, due to the many links in heat transfer and the large thermal resistance, the battery energy density of the energy storage system cannot be effectively improved.

[0005] In addition to the above two cooling methods, in order to deal with the risk of battery combustion or explosion due to the large amount of heat generated during the charging and discharging of energy storage batteries, an immersion liquid-cooled battery energy storage system is designed. The working principle of this type of system is mainly to use battery coolants with good insulation properties, such as the thermostatic insulating liquid in Chinese patent CN114497802A, to conduct heat and isolate oxygen. However, the components of this type of battery coolant are generally fluorine-containing compounds (for example, the above-mentioned thermostatic insulating liquid is a fluorinated liquid), which is volatile, poorly biodegradable, expensive, and decomposes (temperature greater than 200°C) to produce highly toxic hydrogen fluoride and fluoroisobutylene. For this reason, Chinese patent CN115483430A uses flame-retardant oil in combination with the designed electrode connection circuit to achieve the flame retardant and explosion-proof effect of the battery pack, wherein the flame-retardant oil has thermal conductivity, air isolation, electrical insulation, and a ignition point above 300°C or a flash point above 265°C, and at least one of paraffin-based mineral oil, cycloalkane oil, and aromatic hydrocarbon oil is selected to constitute the flame-retardant oil. However, a higher flash point will affect the pumpability and low-temperature flow properties of flame retardant oils (refer to the 40°C kinematic viscosity and pour point of the corresponding refrigeration oils in CN105779078A and CN114317073A), and the selection of aromatic hydrocarbon oils will cause poor biodegradability and increased biotoxicity, limiting their application. At present, it is urgent to propose a mineral oil-based energy storage battery coolant with good low-temperature performance, low biotoxicity, safety and environmental protection. Summary of the invention

[0006] In view of the above problems and shortcomings of the prior art, the first object of the present invention is to provide an immersed mineral energy storage battery coolant composition mainly composed of a mineral base oil.

[0007] The coolant composition comprises a base oil, wherein the base oil is composed of no more than 40% of cycloalkyl mineral oil and no less than 60% of paraffin-based mineral oil by mass, or the base oil is composed of paraffin-based mineral oil; that is, in the base oil, the content of the paraffin-based mineral oil is 60wt% to 100wt%, and the content of the cycloalkyl mineral oil is 0 to 40wt%.

[0008] Preferably, the paraffin-based mineral oil is selected from a mineral oil having a kinematic viscosity of 8 to 15 mm at 40°C. 2 / s and one or more of the hydrorefined paraffin-based crude oil fractions having a pour point of less than or equal to -60°C.

[0009] Preferably, the paraffinic mineral oil is a lubricating oil fraction having a deeply hydrogenated paraffinic characteristic.

[0010] Preferably, the naphthenic mineral oil is selected from a mineral oil having a kinematic viscosity of 8 to 10 mm at 40°C. 2 / s, and one or more of the hydrorefined naphthenic crude oil fractions having a pour point of less than or equal to -60°C.

[0011] Preferably, the naphthenic mineral oil is a lubricating oil fraction having deeply hydrogenated naphthenic characteristics.

[0012] Preferably, the coolant composition further comprises an additive, and the additive is selected from at least one of an antioxidant, a light stabilizer, and an antifoaming agent.

[0013] Preferably, from the perspective of effect and economy, the antioxidant is 0.1% to 0.8% of the total mass of the base oil, and the antioxidant is a phenolic antioxidant, an amine antioxidant, or a complex of them (one or all of the first two). For example, the antioxidant can be selected from one or more of 2,6-di-tert-butyl-p-cresol, 4,4-methylenebis(2,6-di-tert-butylphenol), phenyl-α-naphthylamine, and alkyl diphenylamine.

[0014] Preferably, from the perspective of effect and economy, the light stabilizer is 0.01% to 0.1% of the total mass of the base oil, and the light stabilizer is selected from one or more of benzophenone, salicylic acid, benzotriazole, and hindered amine derivatives.

[0015] Preferably, the antifoaming agent is 0.0001% to 0.001% of the total mass of the base oil, and the antifoaming agent is a silicon-type, non-silicon-type or composite antifoaming agent (a composite of silicon-type and non-silicon-type). For example, the antifoaming agent can be selected from one or more of polyether-modified silicone oil, polydimethylsiloxane, polyacrylate, and polymethacrylate.

[0016] Preferably, the antifoaming agent is selected from one or more of polyether-modified silicone oil and silicone oil with an average molecular weight of more than 60,000.

[0017] Preferably, the mass ratio of the base oil (total mass) to the additive is 100:0.1-1.0.

[0018] Preferably, the kinematic viscosity of the coolant composition at 40°C is 8 to 12 mm 2 / s, if the kinematic viscosity of the coolant composition is too low, the flash point of the coolant composition is low, which makes the safety of the immersed liquid-cooled battery energy storage system have a greater risk; if the kinematic viscosity is too high, the viscosity of the coolant composition is high in low temperature areas, and it is more difficult to pump the coolant composition during system startup.

[0019] Preferably, the coolant composition has a flash point greater than 160°C, a pour point below -60°C, a breakdown voltage greater than 50 kV, a biodegradability (environmental performance) greater than 60%, an acute oral toxicity LD50 greater than 5000 mg / kg (low biological toxicity), and an initial distillation point greater than 300°C (indicating that the coolant composition is not easily volatile, and the increase in the initial distillation point has higher safety performance).

[0020] Preferably, the coolant composition is prepared by mixing the base oil and the additive under heating conditions.

[0021] The second object of the present invention is to provide a method for preparing a coolant composition for an immersed mineral energy storage battery, thereby being able to prepare the above-mentioned coolant composition.

[0022] The preparation method of the coolant composition comprises the following steps:

[0023] The cycloalkane mineral oil with a content of not more than 40% by mass and the paraffin-based mineral oil with a content of not less than 60% by mass are blended at 60-80° C. and then mixed with the additives, or the paraffin-based mineral oil is mixed with the additives at 60-80° C.

[0024] Preferably, the preparation method of the naphthenic mineral oil specifically comprises the following steps: performing atmospheric and vacuum distillation on naphthenic crude oil to obtain a fraction at 300-350°C, and performing hydrofining on the fraction to obtain naphthenic mineral oil, wherein the kinematic viscosity of the naphthenic mineral oil at 40°C is 8-10 mm 2 / s, and the pour point is less than or equal to -60°C.

[0025] Preferably, the preparation method of the paraffin-based mineral oil specifically comprises the following steps: subjecting the paraffin-based crude oil to atmospheric and vacuum distillation to obtain a fraction at 300 to 360° C., and subjecting the fraction to hydrogenation refining to obtain the paraffin-based mineral oil, wherein the paraffin-based mineral oil has a kinematic viscosity at 40° C. of 8 to 15 mm 2 / s, and the pour point is less than or equal to -60°C.

[0026] The third object of the present invention is to provide an application of an immersed mineral energy storage battery coolant composition in an electrochemical energy storage system. By forced circulation of the coolant composition, the temperature difference between the energy storage batteries in the electrochemical energy storage system can be controlled, thereby achieving the purpose of improving the internal temperature uniformity of the system.

[0027] Preferably, the electrochemical energy storage system includes an energy storage battery disposed in the above-mentioned coolant composition (immersed in the coolant composition), and the heat generated by the energy storage battery (such as a battery cell) is conducted to the outside of the energy storage battery through the coolant composition.

[0028] Preferably, the electrochemical energy storage system is a lithium battery system.

[0029] The beneficial effects of the present invention are embodied in:

[0030] The coolant composition provided by the present invention uses mineral base oil as a main component, does not add synthetic oil, has low cost, and the base oil is easy to obtain, and can meet the needs of immersion direct cooling of electrochemical energy storage systems in low-temperature areas.

[0031] Furthermore, the present invention optimizes the selection of base oil (for example, blending cycloalkyl mineral oil with different kinematic viscosities with paraffin-based mineral oil) to make the coolant composition have a lower pour point and suitable viscosity, and at the same time have good insulation, biodegradability and chemical stability, and low biological toxicity.

[0032] Furthermore, the present invention improves the performance of the coolant composition by adding different types of additives to the base oil alone or in combination. For example, the additives may be antioxidants for improving thermal oxidation stability, light stabilizers for improving the color change of the coolant under light, or anti-foaming agents for inhibiting foaming and reducing operating noise.

[0033] The preparation method of the coolant composition provided by the present invention can prepare the coolant composition with the above-mentioned excellent performance, and has the advantage of simple process, which is conducive to actual industrial production.

[0034] The coolant composition provided by the present invention provides an effective solution for the thermal management of electrochemical energy storage systems in low-temperature areas. It improves the heat dissipation efficiency, reduces the temperature difference of the battery cells, and reduces energy consumption, thereby increasing the energy density of the energy storage battery. DETAILED DESCRIPTION

[0035] The present invention is further described in detail below in conjunction with the embodiments. Obviously, the embodiments are only used to explain the technical solutions of the present invention, rather than to limit the protection scope of the present invention.

[0036] The base oil component of the mineral coolant used in the embodiment of the present invention is at least one or two of cycloalkane mineral lubricating oil and / or paraffin-based mineral lubricating oil produced and sold by PetroChina Karamay Petrochemical Co., Ltd. through a combination of multiple hydrogenation and refining processes; the additives (antioxidants, light stabilizers, antifoaming agents) used are all commercially available industrial products, and there is no restriction on the additive manufacturer.

[0037] The specific preparation method of naphthenic mineral lubricating oil is as follows: naphthenic crude oil is first subjected to atmospheric and vacuum distillation (atmospheric pressure and vacuum distillation) to obtain a fraction with a distillation range of 300-350°C, and then the fraction is hydrotreated by adopting the process technology of "hydrogenation treatment-hydrodecondensation-supplementary refining-precision fractionation". The kinematic viscosity of the obtained naphthenic mineral lubricating oil at 40°C is between 8 and 10 mm 2 / s range, pour point is less than or equal to -60℃.

[0038] The specific preparation method of paraffin-based mineral lubricating oil is as follows: paraffin-based crude oil is first subjected to atmospheric and vacuum distillation (atmospheric pressure and vacuum distillation) to obtain a fraction with a distillation range of 300-360°C, and then hydrogenated and refined using the "hydrogenation treatment-isomerization dewaxing-supplementary refining" process technology. The resulting paraffin-based mineral lubricating oil has a kinematic viscosity of 8-15 mm at 40°C. 2 / s range, pour point is less than or equal to -60℃.

[0039] The paraffin-based mineral lubricating oil and cycloalkyl mineral lubricating oil prepared above are blended according to the formula of Examples 2 to 5 or prepared separately according to Examples 1 and 6 to obtain base oil; then the required additives are added to the base oil (for example, antioxidants, light stabilizers, antifoaming agents are added in sequence), and then stirred and mixed to obtain a mineral type coolant. The blending temperature used in Examples 2 to 5 is 60°C to 80°C (this temperature range does not affect the performance of the coolant), and it is fully mixed; while the base oil of Examples 1 and 6 does not need to be blended, and the additives can be added directly after being heated to the specified temperature. The ingredients and amounts in the formula of each example are shown in Table 1.

[0040] Table 1. Base oil composition (mass fraction) and mass ratio of additives to base oil

[0041]

[0042] The properties of the mineral coolants in the above embodiments were tested, and the test results are shown in Table 2.

[0043] Table 2. Test indexes of mineral coolant properties

[0044]

[0045] It can be seen from Table 2 that the base oil components used in Examples 1 to 6 and the coolants formed therefrom have the advantage of low biological toxicity. Table 2 also shows that the coolants of Examples 1 to 5 have excellent oxidation stability, good low temperature performance (such as low temperature fluidity), good electrical insulation performance, high flash point, good thermal conductivity, and good biodegradability.

Claims

1. An immersion mineral energy storage battery coolant composition, characterized in that: The coolant composition comprises a base oil, wherein the base oil is composed of no more than 40% of naphthenic mineral oil and no less than 60% of paraffinic mineral oil by mass, or the base oil is composed of paraffinic mineral oil.

2. The immersion mineral energy storage battery coolant composition according to claim 1, characterized in that: The paraffin-based mineral oil is selected from a range of kinematic viscosity of 8 to 15 mm 2 / s and one or more of the hydrorefined paraffin-based crude oil fractions having a pour point of less than or equal to -60°C.

3. The immersion mineral energy storage battery coolant composition according to claim 1, characterized in that: The naphthenic mineral oil is selected from a group consisting of a petroleum ether having a kinematic viscosity of 8 to 10 mm 2 / s, and one or more of the hydrorefined naphthenic crude oil fractions having a pour point of less than or equal to -60°C.

4. The immersion mineral energy storage battery coolant composition according to claim 1, characterized in that: The coolant composition further comprises an additive, wherein the additive is selected from at least one of an antioxidant, a light stabilizer and an antifoaming agent.

5. The immersion mineral energy storage battery coolant composition according to claim 4, characterized in that: The mass ratio of the base oil to the additive is 100:0.1-1.

0.

6. The immersion type mineral energy storage battery coolant composition according to claim 4, characterized in that: The kinematic viscosity of the coolant composition is 8 to 12 mm 2 / s, flash point greater than 160℃, pour point below -60℃, breakdown voltage greater than 50kV, biodegradability greater than 60%, acute oral toxicity LD50 greater than 5000mg / kg, initial distillation point greater than 300℃.

7. A method for preparing a coolant composition for an immersed mineral energy storage battery, characterized in that: The following steps are involved: The cycloalkane mineral oil with a content of not more than 40% by mass and the paraffin-based mineral oil with a content of not less than 60% by mass are blended at 60-80° C. and then mixed with the additives, or the paraffin-based mineral oil is mixed with the additives at 60-80° C.

8. The method for preparing a coolant composition for an immersed mineral energy storage battery according to claim 7, characterized in that: The preparation method of the naphthenic mineral oil specifically comprises the following steps: distilling naphthenic crude oil to obtain a fraction at 300-350° C., and hydrofining the fraction to obtain naphthenic mineral oil, wherein the kinematic viscosity of the naphthenic mineral oil is 8-10 mm 2 / s, and the pour point is less than or equal to -60°C; the preparation method of the paraffin-based mineral oil specifically comprises the following steps: distilling the paraffin-based crude oil to obtain a fraction of 300 to 360°C, and hydrofining the fraction to obtain the paraffin-based mineral oil, wherein the kinematic viscosity of the paraffin-based mineral oil is 8 to 15 mm 2 / s, and the pour point is less than or equal to -60°C.

9. Use of a naphthenic mineral oil, a paraffinic mineral oil or an immersion mineral energy storage battery coolant composition as claimed in any one of claims 1 to 6 in an electrochemical energy storage system.

10. An electrochemical energy storage system, characterized in that: The invention comprises an energy storage battery arranged in the immersed mineral energy storage battery coolant composition as claimed in any one of claims 1 to 6.

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