CN109768326B - Electrolyte and electrochemical energy storage device - Google Patents
Electrolyte and electrochemical energy storage device Download PDFInfo
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Abstract
The application provides an electrolyte and an electrochemical energy storage device. The electrolyte comprises a cyclic sulfate compound additive, a cyclic sulfonate compound additive, a dinitrile compound additive, and a silicon-based phosphate compound additive or a silicon-based borate compound additive or a mixture of the two. The electrolyte can effectively inhibit the transition metal ions from dissolving out, protects the positive and negative electrode interfaces, remarkably reduces the interface impedance between the electrode and the electrolyte, improves the low-temperature discharge performance of the electrochemical energy storage device, and can also remarkably improve the cycle performance and the storage performance of the electrochemical energy storage device.
Description
Technical Field
The application relates to the field of energy storage devices, in particular to electrolyte and an electrochemical energy storage device.
Background
In recent years, with the growing concern about environmental problems, research and development efforts have been made on Electric Vehicles (EVs) and Hybrid Electric Vehicles (HEVs) that can replace gasoline vehicles and diesel vehicles using fossil fuels, and in particular, research on novel energy sources that can power EVs and HEVs has been actively conducted. In addition to considering the environmental issues, the requirement of new energy sources with high energy density and high safety also forces researchers to conduct more intensive research on the existing new energy sources. Among them, lithium ion batteries are receiving attention because of their characteristics such as high specific energy, long cycle life, less self-discharge, and good safety, and their applications are now in the aspects of daily life, such as cameras, notebook computers, and electric vehicles.
In the process of first charging and discharging of the lithium ion battery, the Electrolyte is reduced and decomposed at the negative electrode Interface, and the decomposed product is deposited on the surface of the negative electrode to form a layer of film, which is generally called a Solid Electrolyte Interface (SEI) film. The excellent SEI film can effectively prevent solvent molecules from continuously reducing on the surface of the negative electrode, and prevent solvated lithium ions from being inserted into graphite layers, so that the negative electrode can be protected. And a proper additive is added into the electrolyte to help form a high-quality SEI film on the surface of the negative electrode.
Therefore, there is a need to develop an additive or an additive combination capable of improving the comprehensive performance of a lithium ion battery, which can form a passivation film with good performance and low impedance on the positive and negative electrode interfaces of the lithium ion battery, so that the lithium ion battery has good cycle performance and storage performance.
Disclosure of Invention
In view of the problems in the background art, an object of the present application is to provide an electrolyte and an electrochemical energy storage device, where the electrolyte can effectively inhibit the dissolution of transition metal ions, protect positive and negative interfaces, significantly reduce the interface impedance between an electrode and the electrolyte, improve low-temperature discharge performance, and significantly improve cycle performance and storage performance.
In order to achieve the above objects, in one aspect of the present application, there is provided an electrolyte including an additive a, an additive B, an additive C, and an additive D. The additive A is selected from one or more compounds shown in formula 1, the additive B is selected from one or more compounds shown in formula 2, the additive C is selected from one or more compounds shown in formula 3, and the additive D is selected from one or more compounds shown in formula 4 and 5. In formula 1, R11Selected from H, halogen atom, C1-C6 alkyl or halogenated alkyl, C2-C6 alkenyl or halogenated alkenyl, in formula 2, m is an integer of 2-10, R21Selected from H, halogen atom, C1-C6 alkyl or halogenated alkyl, in formula 3, n is an integer of 1-10, in formula 4, R31、R32、R33、R34、R35、R36、R37、R38、R39Each independently selected from C1-C10 alkyl or haloalkyl, in formula 5, R41、R42、R43、R44、R45、R46、R47、R48、R49Each independently selected from C1-C10 alkyl or haloalkyl.
In another aspect of the present application, an electrochemical energy storage device is provided that includes an electrolyte according to one aspect of the present application.
Compared with the prior art, the application at least comprises the following beneficial effects:
the electrolyte can effectively inhibit the transition metal ions from dissolving out, protects the positive and negative electrode interfaces, remarkably reduces the interface impedance between the electrode and the electrolyte, improves the low-temperature discharge performance, and can remarkably improve the cycle performance and the storage performance.
Detailed Description
The electrolyte and electrochemical energy storage device according to the present application are described in detail below.
First, an electrolytic solution according to the first aspect of the present application is explained.
The electrolyte according to the first aspect of the present application comprises an additive a, an additive B, an additive C, and an additive D.
In the electrolyte according to the first aspect of the present application, the additive a is a cyclic sulfate compound, and may be specifically selected from one or more compounds represented by formula 1. In formula 1, R11Selected from H, halogen atoms, alkyl or halogenated alkyl of C1-C6, alkenyl or halogenated alkenyl of C2-C6. Preferably, R11Selected from H, F, methyl, ethyl, propyl, butyl or vinyl.
In the electrolyte according to the first aspect of the present application, the additive B is a cyclic sulfonate compound, and may be specifically selected from one or more compounds represented by formula 2. In formula 2, m is an integer of 2 to 10, R21Selected from H, halogen atoms, C1-C6 alkyl or halogenated alkyl. Preferably, m is 3 or 4, R21Selected from H or methyl.
In the electrolyte according to the first aspect of the present application, the additive C is a dinitrile compound, and may be specifically selected from one or more compounds represented by formula 3. In formula 3, n is an integer of 1 to 10. Preferably, n is 4, 5 or 6.
In the electrolyte according to the first aspect of the present application, the additive D is a silicon-based phosphate compound, a silicon-based borate compound, or a mixture of the two, and specifically may be one or more selected from the compounds represented by formula 4 and the compounds represented by formula 5. In formula 4, R31、R32、R33、R34、R35、R36、R37、R38、R39Each independently selected from C1-C10 alkyl or haloalkyl. In formula 5, R41、R42、R43、R44、R45、R46、R47、R48、R49Each independently selected from C1-C10 alkyl or haloalkyl.
In the electrolyte according to the first aspect of the present application, the cyclic sulfate compound may participate in film formation with the positive and negative electrode interfaces during formation and cyclic storage of the electrochemical energy storage device, the main component of the film forming on the positive electrode interface is an organic lithium compound of alkyl lithium sulfate class, the main component of the film forming on the negative electrode interface is lithium sulfite and a polymer similar to polyethylene oxide (PEO), therefore, the film forming impedance of the positive and negative electrode interfaces can be reduced, the migration resistance of ions on the positive and negative electrode interfaces is reduced, meanwhile, the probability of side reaction of the electrolyte on the positive and negative electrode interfaces can be reduced, but the film forming quality of the electrolyte on the positive electrode interface is generally poor, the side reaction of the electrolyte on the positive electrode interface can not be effectively inhibited, in addition, the thermal stability of the cyclic sulfate compound is poor, decomposition is easy to occur at high temperature, and decomposition products are deposited on the positive and negative electrode interfaces, so that film formation of the positive and negative electrode interfaces can be damaged. The cyclic sulfonate compound can also participate in film formation of positive and negative interfaces in the formation and cyclic storage processes of an electrochemical energy storage device, the film formation quality is good, the side reaction of the electrolyte on the positive and negative interfaces can be effectively inhibited, and the formed passive film has high impedance. Cyano (-CN) in the dinitrile compound structure has negative charge and can be complexed with transition metal ions in the positive active material, so that the dissolution of the transition metal ions is inhibited in the circulating storage process of the electrochemical energy storage device, the structure of the positive active material is stabilized, the oxidative decomposition of electrolyte at the positive electrode is reduced, the gas production rate in the circulating storage process is reduced, but the side reaction is easy to occur at the negative electrode to damage the negative electrode interface, and the interface impedance of the positive electrode is obviously deteriorated when the content is more. The silicon-based phosphate compound and the silicon-based borate compound can also participate in film formation at the positive electrode interface in the formation and circulating storage processes of the electrochemical energy storage device, so that the oxidative decomposition of the electrolyte at the positive electrode is reduced, the positive electrode interface impedance is obviously reduced, and compared with other impedance-reducing additives, the impedance-reducing range of the positive electrode interface is larger, and the other electrochemical properties cannot be obviously deteriorated; in addition, in the discharging process, especially in the low-temperature discharging process, the positive electrode interfacial impedance becomes a main factor for restricting the improvement of the performance of the electrochemical energy storage device, and the reduction of the positive electrode interfacial impedance is beneficial to the rapid removal of ions from a positive electrode active material, namely, the ions can be rapidly released from the source, so that the low-temperature discharging performance of the electrochemical energy storage device can be remarkably improved by the silicon-based phosphate compound and the silicon-based borate compound.
Therefore, in the electrolyte, a good interface passivation film can be formed on the positive and negative interfaces by using the cyclic sulfonate compound, side reactions of the electrolyte on the positive and negative interfaces are inhibited, the improvement of film formation impedance of the cyclic sulfonate compound is inhibited by using the cyclic sulfate compound, the silicon-based phosphate compound and the silicon-based borate compound, the structure of the positive interface is stabilized by using the dinitrile compound, the negative interface can be protected by using the cyclic sulfate compound and the cyclic sulfonate compound, the deterioration of the negative interface by the dinitrile compound is avoided, and the deterioration of the positive interface impedance by using the silicon-based phosphate compound and the silicon-based borate compound is inhibited. Under the combined action of the substances, a passive film with low impedance and good quality can be formed on the positive and negative electrode interfaces of the electrochemical energy storage device, the dissolution of transition metal ions in the positive electrode active material can be effectively inhibited, the positive and negative electrode interfaces are protected, the interface impedance between an electrode and electrolyte is remarkably reduced, the low-temperature discharge performance is improved, and the cycle performance and storage performance, particularly the cycle performance and storage performance in a high-temperature and high-pressure environment, can be remarkably improved.
In the electrolyte solution according to the first aspect of the present application, a halogenated cyclic carbonate compound, such as fluoroethylene carbonate (FEC), is not included in the electrolyte solution. The additive generates hydrogen fluoride in the electrolyte through side reaction, the hydrogen fluoride can erode the interface of the positive electrode, the high-temperature storage performance is greatly influenced especially in a high-nickel ternary positive electrode active material system, and the hydrogen fluoride also reacts with an organic solvent in the electrolyte, so that the components of the electrolyte are greatly damaged. Thus, in the electrolyte of the present application, a cyclic sulfonate compound and a cyclic sulfate compound are used in combination to replace the film forming effect of a halogenated cyclic carbonate (e.g., FEC).
In the electrolyte according to the first aspect of the present application, the mass relationships of the additive a, the additive B, and the additive C are as follows: additive A/additive B is not less than 1 and not more than 4, and additive A/additive C is not less than 1 and not more than 4. The additive A is oxidized at the positive electrode interface, the product of the oxidation reaction participates in the film formation at the positive electrode interface, the main component of the additive A is an alkyl lithium sulfate type organic lithium compound, the additive A can simultaneously perform a reduction reaction at the negative electrode interface, the product of the reduction reaction participates in the formation of the negative electrode interface SEI film, and the main component of the additive A is lithium sulfite and a polymer similar to polyethylene oxide (PEO), so that the additive A can enable the film formation impedance of the positive electrode interface and the negative electrode interface to be low, and can inhibit the side reaction of the electrolyte at the positive electrode interface to a certain extent, but the film formation quality at the positive electrode interface is generally poor, and the side reaction of the electrolyte at the positive electrode interface is difficult to be completely inhibited. The additive B has the main function of participating in film formation of a positive interface and a negative interface, has good film formation quality, can effectively inhibit the electrolyte from being oxidized and decomposed at the positive electrode, but can also be subjected to reduction reaction at the negative electrode, and the product is deposited on the surface of the negative electrode, so that the impedance of the negative electrode interface is easily increased, and the electrochemical performance is adversely affected. The mass ratio of the additive A to the additive B is controlled to be 1-4, when the content of the additive A is more than that of the additive B, the deterioration of the interface impedance of the negative electrode caused by the participation of the additive B in film forming of the negative electrode can be effectively inhibited, but when the content of the additive A exceeds 4 times of that of the additive B, the additive B is easy to decompose at high temperature due to poor thermal stability of the additive A, organic polymers generated by decomposition can be deposited on a positive interface and a negative interface, and an original interface film is damaged, so that the electrochemical performance of an electrochemical energy storage device can be deteriorated. The additive C has the functions of complexing with the transition metal ions of the positive electrode, protecting the structure of the active material of the positive electrode from being damaged, and inhibiting the electrolyte from being oxidized on the interface of the positive electrode, but the additive C is easy to reduce on the negative electrode, and damages the interface of the negative electrode to further deteriorate the electrochemical performance. The additive A can effectively participate in the film forming effect of the negative electrode, protect the negative electrode and inhibit the reduction effect of the additive C on the negative electrode. When the mass ratio of the additive A to the additive C is 1-4, the positive electrode structure can be effectively protected, dissolution of transition metal ions of the positive electrode can be inhibited, damage of the additive C to the negative electrode can be avoided, when the mass ratio of the additive A to the negative electrode is low, the additive A is insufficient in film formation and cannot protect the negative electrode structure, when the mass ratio of the additive A to the negative electrode is high, excessive additive A can be decomposed due to poor thermal stability of the additive A in the circulation process of the electrochemical energy storage device, decomposition products deposited on the negative electrode can damage a negative electrode interface passivation film, and the reduction of the additive C on the negative electrode cannot be effectively inhibited.
In the electrolyte according to the first aspect of the present application, preferably, the additive a may be selected from one or more of the following compounds:
in the electrolyte according to the first aspect of the present application, when the content of the additive a is too low, it is difficult to form a complete passivation film on the positive and negative electrode interfaces, and when the content of the additive a is too high, the high temperature performance of the electrochemical energy storage device is deteriorated, and the cost of the electrolyte is increased to a large extent. Preferably, the content of the additive A is 0.01-3% of the total mass of the electrolyte.
In the electrolyte according to the first aspect of the present application, preferably, the additive B may be selected from one or more of the following compounds:
in the electrolyte according to the first aspect of the present application, when the content of the additive B is too low, the additive B does not significantly improve the quality of the optimized passivation film, and when the content of the additive B is too high, the passivation film formed on the positive and negative electrode interfaces is thicker, which increases the interface impedance of the positive and negative electrodes, and is not favorable for improving the performance of the electrochemical energy storage device. Preferably, the content of the additive B is 0.01-3% of the total mass of the electrolyte.
In the electrolyte according to the first aspect of the present application, preferably, the additive C may be selected from one or more of succinonitrile, glutaronitrile, adiponitrile, 1, 4-decanedionitrile.
In the electrolyte according to the first aspect of the present application, when the content of the additive C is too low, the additive C does not perform a function of complexing transition metal ions, so that the purpose of protecting the active material of the positive electrode cannot be achieved, and when the content of the additive C is too high, the viscosity of the electrolyte is increased, and excessive nitrile groups are attached to the surface of the positive electrode, so that the interface impedance of the positive electrode is increased, and the dynamic performance of the electrochemical energy storage device is deteriorated. Preferably, the content of the additive C is 0.01-3% of the total mass of the electrolyte.
In the electrolyte according to the first aspect of the present application, the additive D may be selected from one or more of tris (trimethylsilane) borate, tris (triethylsilane) borate, tris (tripropylsilane) borate, tris (tributylsilane) borate, bis (trimethylsilane) triethylborate, tris (trimethylsilane) phosphate, tris (triethylsilane) phosphate, tris (tripropylsilane) phosphate, tris (tributylsilane) phosphate, bis (trimethylsilane) triethylphosphate.
In the electrolyte according to the first aspect of the present application, when the content of the additive D is too small, the effect of reducing the interface impedance of the positive electrode cannot be achieved, and when the content of the additive D is too large, the passivation film formed on the positive and negative electrode interfaces is thick, which may increase the interface impedance of the positive and negative electrodes, which is not favorable for improving the performance of the electrochemical energy storage device. Preferably, the content of the additive D is 0.01-3% of the total mass of the electrolyte.
In the electrolyte according to the first aspect of the present application, the electrolyte may further include one or more of ethylene carbonate, lithium bis (oxalyldifluoroborate), and lithium bis (fluorosulfonylimide).
In the electrolyte according to the first aspect of the present application, the electrolyte further includes an organic solvent, and the type of the organic solvent is not particularly limited and may be selected according to actual needs. Preferably, a non-aqueous organic solvent is selected that has good thermal and electrochemical stability at higher temperatures and higher voltages. Specifically, the organic solvent may be one or more selected from dimethyl carbonate, diethyl carbonate, dipropyl carbonate, ethyl methyl carbonate, propyl ethyl carbonate, ethylene carbonate, propylene carbonate, butylene carbonate, gamma-butyrolactone, methyl formate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate and tetrahydrofuran. The organic solvent can provide a stable electrochemical environment for the electrochemical energy storage device with high voltage of 4.2V and above.
In the electrolyte according to the first aspect of the present application, the content of the organic solvent is not particularly limited, and may be selected according to actual needs. Preferably, the content of the organic solvent is 65-85% of the total mass of the electrolyte.
In the electrolyte according to the first aspect of the present application, the electrolyte further includes an electrolyte salt, and the kind of the electrolyte salt is not particularly limited and may be selected according to actual needs.
In the electrolyte according to the first aspect of the present application, the concentration of the electrolyte salt is not particularly limited, and may be selected according to actual needs. Preferably, the concentration of the electrolyte salt is 0.5M to 1.5M, and more preferably, the concentration of the electrolyte salt is 0.8M to 1.2M.
Next, an electrochemical energy storage device according to the second aspect of the present application will be described.
An electrochemical energy storage device according to the second aspect of the present application comprises an electrolyte according to the first aspect of the present application.
In the electrochemical energy storage device according to the second aspect of the present application, the electrochemical energy storage device further comprises a positive electrode sheet, a negative electrode sheet, a separator, a packaging case, and the like.
In the electrochemical energy storage device according to the second aspect of the present application, it should be noted that the electrochemical energy storage device may be a lithium ion battery, a sodium ion battery, a zinc ion battery, a lithium metal battery, an all solid state lithium battery or an all solid state sodium battery. In the embodiments of the present application, only the embodiment in which the electrochemical energy storage device is a lithium ion battery is shown, but the present application is not limited thereto.
In the lithium ion battery, the positive plate includes a positive electrode current collector and a positive electrode active material layer disposed on the positive electrode current collector. The kind of the positive electrode active material is not particularly limited and may be selected according to actual needs. Preferably, the positive active material may be selected from lithium cobaltate (LiCoO)2) Lithium nickelate (LiNiO)2) And one or more of nickel cobalt lithium manganate ternary materials. Further preferably, the positive active material can be selected from nickel cobalt lithium manganate ternary materials with nickel content higher than 60%. The positive electrode sheet may further include a conductive agent and a binder. The kind of the conductive agent and the binder is not particularly limited and may be selected according to actual requirements.
In the lithium ion battery, the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer disposed on the negative electrode current collector. The kind of the negative electrode active material is not particularly limited and may be selected according to actual needs. Superior foodAlternatively, the negative active material may be selected from natural graphite, artificial graphite, mesocarbon microbeads (abbreviated as MCMB), hard carbon, soft carbon, silicon oxide, silicon-carbon composite, Li-Sn alloy, Li-Sn-O alloy, Sn, SnO2Spinel-structured lithiated TiO2-Li4Ti5O12And one or more of Li-Al alloy. Wherein, the silicon can be selected from one or more of silicon nanoparticles, silicon nanowires, silicon nanotubes, silicon films, 3D porous silicon and hollow porous silicon. The negative electrode tab may further include a conductive agent and a binder. The kind of the conductive agent and the binder is not particularly limited and may be selected according to actual requirements. The negative electrode sheet may also use lithium metal or a lithium metal alloy.
In the lithium ion battery, the electrolyte salt is a lithium salt, and the specific type of the lithium salt is not limited and can be selected according to actual requirements. Preferably, the lithium salt can be selected from one or more of lithium hexafluorophosphate, lithium bis (trifluoromethyl) sulfonimide, lithium tetrafluoroborate, lithium trifluoromethanesulfonate, lithium hexafluoroarsenate, lithium bis (oxalato) borate and lithium perchlorate. Further preferably, the lithium salt is selected from lithium hexafluorophosphate.
In the lithium ion battery, the kind of the separator is not particularly limited and may be selected according to actual needs, and specifically, the separator may be selected from a polyethylene film, a polypropylene film, a polyvinylidene fluoride film, and a multi-layer composite film thereof.
The present application is further illustrated below with reference to examples. It should be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the present application. In the embodiments, only the case where the electrochemical energy storage device is a lithium ion battery is shown, but the present application is not limited thereto.
The lithium ion batteries of examples 1 to 19 and comparative examples 1 to 12 were prepared as follows.
(1) Preparation of the electrolyte
The additives shown in tables 1 and 3 were added to a nonaqueous organic solvent (EC: DEC. about.30: 70, mass ratio) in an argon-filled glove box (water content < 10ppm, oxygen content < 1ppm), and mixed wellAfter homogenization, an appropriate amount of lithium salt (LiPF) is slowly added6) And after the lithium salt is completely dissolved, obtaining the electrolyte with the lithium salt concentration of 1 mol/L. In table 1, the respective additive contents are mass percentages calculated based on the total mass of the electrolyte.
(2) Preparation of positive plate
LiNi serving as a positive electrode active material0.8Co0.1Mn0.1O2The conductive agent Super P and the binder polyvinylidene fluoride (PVDF) are prepared into positive electrode slurry in N-methyl pyrrolidone (NMP). Wherein the solid content in the positive electrode slurry is 50 wt%, LiNi0.8Co0.1Mn0.1O2The mass ratio of Super P to PVDF is 8:1: 1. Coating the positive electrode slurry on a positive electrode current collector aluminum foil, drying at 85 ℃, cold-pressing, trimming, cutting into pieces, slitting, and drying at 85 ℃ for 4h to obtain the positive electrode plate.
(3) Preparation of negative plate
The negative electrode active material artificial graphite is uniformly mixed with a conductive agent Super P, a thickening agent CMC and a binding agent Styrene Butadiene Rubber (SBR) in deionized water to prepare negative electrode slurry. Wherein the solid content in the negative electrode slurry is 40 wt%, and the mass ratio of the graphite to the Super P to the CMC to the SBR is 89:6:3: 2. And coating the negative electrode slurry on a copper foil of a negative electrode current collector, drying at 85 ℃, then carrying out cold pressing, trimming, cutting and slitting, and drying for 12h at 120 ℃ under a vacuum condition to prepare the negative electrode sheet.
(4) Preparation of the separator
A16 μm thick Polyethylene (PE) film was used as the separator.
(5) Preparation of lithium ion battery
The positive plate, the isolation film and the negative plate are sequentially stacked, the isolation film is positioned between the positive plate and the negative plate to isolate the positive plate and the negative plate, a naked battery cell is obtained by winding, a tab is welded, the naked battery cell is placed in an outer package, the prepared electrolyte is injected into the dried battery cell, and the lithium ion battery is packaged, stood, formed, shaped, subjected to capacity test and the like to complete the preparation of the lithium ion battery.
Table 1: electrolyte parameters for examples 1-18 and comparative examples 1-11
Next, a test procedure of the lithium ion battery is explained.
(1) High temperature cycle performance testing of lithium ion batteries
At 45 ℃, charging the lithium ion battery to 4.2V at a constant current of 1C, then charging to 0.05C at a constant voltage of 4.2V, and then discharging to 2.8V at a constant current of 1C, which is a charge-discharge cycle, wherein the discharge capacity of the first cycle is the discharge capacity of the first cycle, and the discharge capacity of the first cycle is 100%, and the lithium ion battery is subjected to 300-cycle charge/discharge tests according to the method, and the discharge capacity of the 300 th cycle is obtained through detection.
The capacity retention (%) after the lithium ion battery was cycled 300 times at 45 ℃ was equal to the discharge capacity at 300 cycles/discharge capacity at the first cycle × 100%.
(2) High-temperature storage gas production test of lithium ion battery
Under the condition of room temperature, the lithium ion battery is charged to 4.2V at a constant current of 1C, then charged to 0.05C at a constant voltage of 4.2V, and after full charge, the volume of the lithium ion battery is tested by a drainage method and is marked as V0. And then storing the lithium ion battery at 80 ℃ for 24 hours, taking out the lithium ion battery, standing for 60min at room temperature, testing the volume of the lithium ion battery by a drainage method within 1 hour after cooling to the room temperature, and then performing storage test every 24 hours according to the steps until the storage is full of 30 days, wherein the volume of the lithium ion battery stored for 30 days is marked as V1.
The lithium ion battery has a volume expansion ratio (%) of (V1/V0) x 100% -1 after 30 days of storage at 80 ℃.
(3) High temperature storage capacity testing of lithium ion batteries
Charging the lithium ion battery to 4.2V at a constant current of 1C, then to 0.05C at a constant voltage of 4.2V, and then to 2.8V at a constant current of 0.5C at room temperature, and recording the discharge capacity D0; and (3) fully charging the lithium ion battery according to the charging mode, storing the lithium ion battery at 60 ℃ for 30 days, discharging the lithium ion battery to 2.8V at a constant current of 1C after the storage is finished, and recording the discharge capacity D1.
The capacity retention (%) of the lithium ion battery after storage at 60 ℃ for 30 days was (D1/D0) × 100%.
(4) Low-temperature discharge performance test of lithium ion battery
And (2) placing the lithium ion battery in a high-low temperature box, adjusting the furnace temperature to be 25 ℃, charging to 4.2V by using a 1C constant current after the surface temperature of the lithium ion battery is 25 ℃, charging to 0.05C by using a 4.2V constant voltage, then discharging to 2.8V by using a 1C constant current, recording the discharge capacity as C0, fully charging the lithium ion battery according to the charging mode, adjusting the high-low temperature box to be-30 ℃, discharging to 2.8V by using a 1C constant current after the surface temperature of the lithium ion battery is-30 ℃, and recording the discharge capacity as C1.
The low-temperature discharge capacity retention (%) of the lithium ion battery is C1/C0 × 100%.
Table 2: results of Performance test of examples 1 to 18 and comparative examples 1 to 11
As can be seen from the test results of examples 1-18 and comparative examples 1-11, the comparative example 11 has no additive, and the lithium ion battery has poor performance, which is difficult to meet the actual use requirement. The performances of the embodiments 1 to 18 are greatly improved, which shows that the additive a, the additive B, the additive C and the additive D can effectively inhibit the dissolution of transition metal ions after combined use, form a relatively stable passivation film on the positive and negative electrode interfaces, protect the positive and negative electrode interfaces, not only significantly reduce the interface impedance between the electrode and the electrolyte, improve the low-temperature discharge performance, but also significantly improve the cycle performance and the storage performance. In the comparative example 6, only the additive A is added, although the additive A can form a film on the positive and negative electrode interfaces, the film forming quality of the additive A on the positive electrode interface is poor, in addition, in the high-temperature circulation and storage processes, transition metal ions on the surface of the positive electrode active material can be gradually dissolved out to damage the structure of the positive electrode active material, and the electrolyte generates more side reactions on the surface of the positive electrode, so that the performance of the lithium ion battery is poor; in comparative example 7, the additive a and the additive B are used in combination, and although the film can be formed on the positive and negative electrode interfaces to significantly inhibit the decomposition of the electrolyte, the dissolution of transition metal ions cannot be inhibited, the structure of the positive electrode active material is gradually destroyed in the high-temperature cycle and storage processes, the electrolyte generates more side reactions on the surface of the positive electrode, and the performance of the lithium ion battery is still poor. In the comparative example 8, the additive a, the additive C and the additive D are used in combination, and although the performance of the lithium ion battery can be improved, an interface passivation film with good performance cannot be formed on the positive and negative electrode interfaces, so that the improvement of the performance of the lithium ion battery is limited. Comparative example 9, in which additive a, additive B, and additive D were used in combination, although a film could be formed on the positive and negative electrode interfaces and the film formation resistance was also low, the dissolution of the transition metal ions from the positive electrode active material during charging could not be effectively suppressed, and the dissolved transition metal ions would directly cause the positive electrode active material structure to be destroyed, thereby deteriorating the electrochemical performance of the lithium ion battery. In comparative example 10, the additive B, the additive C, and the additive D are used in combination, although the performance of the lithium ion battery can be improved, the negative electrode has a high film formation impedance, and lithium precipitation is easily caused in the cycle and low-temperature discharge processes, which not only deteriorates the electrochemical performance of the lithium ion battery, but also may cause potential safety hazards.
In comparative example 1, the additives a, B, C and D were added in a large amount, the electrolyte had poor thermal stability, and gas was easily generated by thermal decomposition in a high-temperature environment, which deteriorated the capacity retention rate after high-temperature cycle and the capacity retention rate after high-temperature storage, and increased the gas yield after high-temperature storage.
In comparative example 2, the mass ratio of the additive a/the additive B is low, the additive a cannot effectively form a film on the positive and negative electrode interfaces, the deterioration of the impedance of the additive B on the negative electrode interface cannot be effectively inhibited, and the side reaction between the electrolyte and the positive and negative electrode interfaces cannot be effectively inhibited, so that the lithium ion battery has poor performance. In comparative example 3, the mass ratio of additive a/additive B is higher, and since additive a has poor thermal stability and is easily decomposed at high temperature, the interface passivation film formed by additive B is damaged by the by-product deposited on the interface of the positive electrode. In comparative example 4, the mass ratio of additive a/additive C was too low, resulting in insufficient film formation at the positive and negative electrode interfaces of additive a, and failure to inhibit reduction of additive C at the negative electrode. In comparative example 5, the additive a/additive C has a relatively high mass ratio, and is easily decomposed at high temperature due to poor thermal stability of the additive a, and the decomposition product deposited on the negative electrode interface may damage the SEI film on the negative electrode interface, so that the reduction of the additive C on the negative electrode may not be effectively inhibited, thereby deteriorating the electrochemical performance of the lithium ion battery.
Table 3: electrolyte parameters for example 19 and comparative example 12
Table 4: results of Performance test of example 19 and comparative example 12
As can be seen from tables 3 and 4, the electrochemical performance of the lithium ion battery is significantly deteriorated when FEC is contained in the electrolyte, because the FEC decomposes at high temperature to generate hydrogen fluoride, which is a corrosive gas, and the gas attacks the interface of the positive electrode, so that the electrolyte components are greatly destroyed, thereby deteriorating the overall electrochemical performance of the lithium ion battery. Therefore, FEC is not used in the electrolyte of the present application.
Claims (9)
1. The electrolyte is characterized by comprising an additive A, an additive B, an additive C and an additive D;
the additive A is selected from one or more compounds shown in a formula 1;
the additive B is selected from one or more compounds shown in the formula 2;
the additive C is selected from one or more compounds shown in a formula 3;
the additive D is selected from one or more of compounds shown in formula 4 and compounds shown in formula 5;
in formula 1, R11Selected from H, halogen atom, alkyl or halogenated alkyl of C1-C6, alkenyl or halogenated alkenyl of C2-C6;
in formula 2, m is an integer of 2 to 10, R21Selected from H, halogen atom, C1-C6 alkyl or halogenated alkyl;
in formula 3, n is an integer of 1 to 10;
in formula 4, R31、R32、R33、R34、R35、R36、R37、R38、R39Each independently selected from alkyl or haloalkyl of C1-C10;
in formula 5, R41、R42、R43、R44、R45、R46、R47、R48、R49Each independently selected from alkyl or haloalkyl of C1-C10;
the mass relationship among the additive A, the additive B and the additive C is as follows: additive A/additive B is more than or equal to 1 and less than or equal to 4, and additive A/additive C is more than or equal to 1 and less than or equal to 4;
the content of the additive A is 1-3% of the total mass of the electrolyte;
the content of the additive B is 1-3% of the total mass of the electrolyte;
the content of the additive C is 0.5-2% of the total mass of the electrolyte;
the content of the additive D is 0.5-3% of the total mass of the electrolyte.
2. The electrolyte of claim 1,
the additive A is selected from one or more of the following compounds:
the additive B is selected from one or more of the following compounds:
the additive C is selected from one or more of succinonitrile, glutaronitrile, adiponitrile and 1, 4-decanedionitrile;
the additive D is selected from one or more of tri (trimethylsilane) borate, tri (triethylsilane) borate, tri (tripropylsilane) borate, tri (tributylsilane) borate, di (trimethylsilane) triethylborate, tri (trimethylsilane) phosphate, tri (triethylsilane) phosphate, tri (tripropylsilane) phosphate, tri (tributylsilane) phosphate and di (trimethylsilane) triethylphosphate.
3. The electrolyte according to claim 1, wherein the electrolyte further comprises an organic solvent, and the organic solvent is one or more selected from dimethyl carbonate, diethyl carbonate, dipropyl carbonate, ethyl methyl carbonate, propyl ethyl carbonate, ethylene carbonate, propylene carbonate, butylene carbonate, gamma-butyrolactone, methyl formate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate and tetrahydrofuran.
4. The electrolyte of claim 3, wherein the organic solvent is present in an amount of 65% to 85% by weight of the total electrolyte.
5. The electrolyte of claim 1, further comprising an electrolyte salt.
6. The electrolyte of claim 5, wherein the electrolyte salt is at a concentration of 0.5M to 1.5M.
7. The electrolyte of claim 5, wherein the electrolyte salt is at a concentration of 0.8M to 1.2M.
8. An electrochemical energy storage device comprising an electrolyte according to any one of claims 1 to 7.
9. An electrochemical energy storage device as in claim 8, wherein said electrochemical energy storage device is a lithium ion battery, a sodium ion battery, a zinc ion battery, a lithium metal battery, an all solid state lithium battery or an all solid state sodium battery.
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| CN110265718B (en) * | 2019-06-18 | 2021-01-12 | 桑顿新能源科技(长沙)有限公司 | Electrolyte additive, electrolyte and battery |
| CN112582673A (en) * | 2019-09-29 | 2021-03-30 | 比亚迪股份有限公司 | Lithium ion battery electrolyte and lithium ion battery |
| CN118231575A (en) * | 2019-12-26 | 2024-06-21 | 宁德新能源科技有限公司 | Electrolyte and electrochemical device |
| CN113130989A (en) * | 2019-12-30 | 2021-07-16 | 深圳市研一新材料有限责任公司 | Electrolyte and electrochemical device |
| CN111446501A (en) * | 2020-04-08 | 2020-07-24 | 青岛滨海学院 | Electrolyte containing-F and-B two-group compound and electrochemical device thereof |
| CN111682264B (en) * | 2020-06-05 | 2022-04-01 | 惠州锂威新能源科技有限公司 | Electrolyte additive, electrolyte and lithium ion battery |
| CN111653829A (en) * | 2020-07-20 | 2020-09-11 | 中航锂电技术研究院有限公司 | Lithium ion battery electrolyte and lithium ion battery |
| CN113036220B (en) * | 2021-03-05 | 2022-12-30 | 星恒电源股份有限公司 | Non-aqueous electrolyte with low impedance and long cycle performance and sodium ion battery |
| CN114069051A (en) * | 2021-11-23 | 2022-02-18 | 天津中电新能源研究院有限公司 | Fluoro-carboxylic acid ester based low-temperature electrolyte and sodium ion battery containing same |
| CN115411262B (en) * | 2022-09-13 | 2024-07-19 | 江苏正力新能电池技术有限公司 | Preparation method of positive electrode material and battery |
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