Electrolyte and electrochemical device of chloro-carboxylic ester lithium battery for high-maneuverability unmanned aerial vehicle

Abstract

The invention provides an electrolyte and an electrochemical device for a chlorinated carboxylic ester lithium battery of a high-maneuverability unmanned aerial vehicle, the electrolyte comprises an electrolyte salt and a solvent, the solvent comprises chlorinated carboxylic ester, the chlorinated carboxylic ester has a structural general formula shown as a formula (I), R1 is alkyl with a C atom number of 1-3, R2 is selected from chlorinated alkyl, R3 is selected from alkyl with a C atom number of 1-3, R4 is selected from alkyl with a C atom number of 1-3, and R4 is selected from alkyl with a C atom number of 1-3. The number of C atoms in R2 is 2-10, and the number of C atoms in R2 is greater than the number of C atoms in R1. As the electrolyte comprises the chloro-carboxylic ester of which the single side is introduced with chlorine atoms, the electrolyte has the advantages of low volatility, low inflammability, compatibility with positive and negative electrodes, excellent dynamic performance and the like, and the electrochemical device applying the electrolyte shows good electrochemical performance and relatively high safety.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of batteries, in particular to an electrolyte for a lithium battery based on chloro carboxylate for high-mobility unmanned aerial vehicles and an electrochemical device. BACKGROUND

[0002] At present, with the rapid development of high-mobility unmanned aerial vehicles, they are increasingly widely used in the fields of military reconnaissance, disaster relief, logistics transportation, etc. The lithium battery for high-mobility unmanned aerial vehicles has very high requirements for the rate performance of the battery, and there is a certain safety risk under high-rate charging and discharging, which may cause thermal runaway, leading to overheating, swelling and even burning of the battery.

[0003] In addition, when the unmanned aerial vehicle makes a sudden maneuver, the battery needs to provide extremely high power output (the instantaneous discharge rate can reach more than 5C) in a short time. The conventional electrolyte will have a serious concentration polarization problem when subjected to high-rate charging and discharging, resulting in a rapid increase in the internal resistance of the battery and a rapid decay of the power performance. SUMMARY

[0004] In view of this, in order to solve at least one of the above technical problems, the present application provides an electrolyte for a lithium battery based on chloro carboxylate for high-mobility unmanned aerial vehicles.

[0005] In addition, the present application also provides an electrochemical device applying the aforementioned electrolyte.

[0006] The present application provides an electrolyte for a lithium battery based on chloro carboxylate for high-mobility unmanned aerial vehicles, which comprises an electrolyte salt and a solvent, wherein the electrolyte salt comprises a lithium salt, and the solvent comprises a chloro carboxylate, and the chloro carboxylate has a general structure as shown in formula (I): (I), wherein R1 is an alkyl group with 1-3 carbon atoms, and R2 is selected from a chloroalkyl group, the number of carbon atoms in R2 is 2-10, and the number of carbon atoms in R2 is greater than that in R1.

[0007] In some possible embodiments, the chloro carboxylate is a linear chloro carboxylate.

[0008] In some possible embodiments, the chloro carboxylate comprises at least one of 3-chloropropyl acetate, 4-chlorobutyl acetate, 5-chloropentyl propionate and 6-chlorohexyl acetate.

[0009] In some possible embodiments, the solvent further comprises a fluoro carbonate.

[0010] In some possible embodiments, the fluoro carbonate is a cyclic fluoro carbonate.

[0011] In some possible embodiments, the fluorinated carbonate has a general structure as shown in formula (II): (II), wherein R3 and R4 are independently selected from one of hydrogen, fluorine and fluorinated alkyl, and R3 and R4 are not hydrogen at the same time.

[0012] In some possible embodiments, the fluorinated carbonate includes at least one of fluorinated ethylene carbonate and difluorinated ethylene carbonate.

[0013] In some possible embodiments, in the solvent, the volume ratio of the chlorinated carboxylic acid ester and the fluorinated carbonate is 1: (0.1-1).

[0014] In some possible embodiments, the lithium salt includes at least one of Li2SO4, LiClO4, LiNO3, LiCl, LiCF3SO3, LiPF6, Li(FSO2)2N, LiBF4, LiDFOB, Li(CF3CF2SO2)2N and Li(CF3SO2)2N.

[0015] Embodiments of the present application also provide an electrochemical device, which includes a positive electrode sheet, a negative electrode sheet, a separator and the aforementioned electrolyte, and the separator is arranged between the positive electrode sheet and the negative electrode sheet.

[0016] Compared with the prior art, the electrolyte based on chlorinated carboxylic acid ester for high-maneuverable unmanned aerial vehicles provided by the embodiments of the present application can improve the flame retardancy of the electrolyte, effectively shorten the self-extinguishing time of the electrolyte, and the electrolyte can generate a solid-state electrolyte interface film (SEI film) containing LiCl at the negative electrode interface, the formed SEI film is dense and has high thermal stability, thereby effectively inhibiting the exothermic reaction of the electrolyte and the lithium-embedded negative electrode, and improving the safety performance of the electrolyte. Moreover, in the chlorinated carboxylic acid ester, the R2 side has a longer chain length than the R1 side, so that the Cl atom on the R2 side is relatively far away from the distance between the carbonyl oxygen, so that Li + has appropriate coordination ability with the carbonyl oxygen in the chlorinated carboxylic acid ester, thereby enhancing the solubility of the lithium salt, improving the lithium ion transference number in the electrolyte, and optimizing the interface structure of the electrolyte-electrode. The unique molecular structure of the chlorinated carboxylic acid ester solves the kinetic bottleneck in the fast charging process of the battery, which is beneficial to the rapid transmission and reaction of ions in the electrolyte, and improves the safety of the electrolyte. The electrolyte system provides a new idea for breaking the trade-off between safety and fast charging in high-energy-density batteries, and is especially suitable for extreme working condition application scenarios such as high-maneuverable unmanned aerial vehicles. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 FIG. 1 is a graph of the results of the electrolyte self-extinguishing test in Example 1 and Comparative Example 1 of the present application, and FIG. 2 is a graph of the results of the electrolyte negative electrode flame retardant test in Example 1 and Comparative Example 1 of the present application, wherein, Figure 1 FIG. 1 is a graph of the results of the electrolyte self-extinguishing test in Example 1 and Comparative Example 1 of the present application, and FIG. 2 is a graph of the results of the electrolyte negative electrode flame retardant test in Example 1 and Comparative Example 1 of the present application, wherein, Figure 1 FIG. 1 is a graph of the results of the electrolyte self-extinguishing test in Example 1 and Comparative Example 1 of the present application, and FIG. 2 is a graph of the results of the electrolyte negative electrode flame retardant test in Example 1 and Comparative Example 1 of the present application, wherein, Figure 1 FIG. 1 is a graph of the results of the electrolyte self-extinguishing test in Example 1 and Comparative Example 1 of the present application, and FIG. 2 is a graph of the results of the electrolyte negative electrode flame retardant test in Example 1 and Comparative Example 1 of the present application, wherein, Figure 1 FIG. 1 is a graph of the results of the electrolyte self-extinguishing test in Example 1 and Comparative Example 1 of the present application, and FIG. 2 is a graph of the results of the electrolyte negative electrode flame retardant test in Example 1 and Comparative Example 1 of the present application, wherein,

[0018] Figure 2 FIG. 3 is a graph of the full cell rate performance test of the battery prepared from the electrolyte in Example 1 and Comparative Example 1 of the present application.

[0019] Figure 3 FIG. 4 is a graph of the full cell fast discharge test of the battery prepared from the electrolyte in Example 1 and Comparative Example 1 of the present application. DETAILED DESCRIPTION

[0020] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all embodiments.

[0021] The present application provides an electrolyte for a chlorocarboxylate-based lithium battery of a high-maneuverable unmanned aerial vehicle, which has high rate capability and non-flammability. The electrolyte comprises an electrolyte salt and a solvent, wherein the solvent comprises a chlorocarboxylate, and the chlorocarboxylate has a general structure as shown in formula (I): (I), wherein R1 is an alkyl group with 1-3 carbon atoms, and R2 is selected from a chloroalkyl group, the number of carbon atoms in R2 is 2-10, and the number of carbon atoms in R2 is greater than the number of carbon atoms in R1.

[0022] The chlorocarboxylate exhibits unique molecular design advantages in terms of high safety and fast charging performance. The mechanism of action of the chlorocarboxylate mainly reflects the following two key dimensions: improvement of intrinsic safety characteristics and synergistic optimization of interface dynamics.

[0023] In terms of safety, the chlorinated carboxylate ester in the electrolyte of the present application achieves multiple protection mechanisms by introducing chlorine atoms into the molecular structure. First, because the bond energy of C-Cl bond (about 339 kJ / mol) is lower than that of C-H bond (about 414 kJ / mol) in typical organic solvents, the chlorinated carboxylate ester preferentially breaks and releases chlorine radicals at the initial stage of thermal runaway, which can effectively quench high-activity radicals such as H· and HO· in the chain combustion reaction, thereby interrupting the combustion chain reaction and shortening the self-extinguishing time of the electrolyte to within 3 s (ASTM D635 test), which is significantly lower than the self-extinguishing time of more than 30 s of traditional carbonate systems, effectively improving the flame retardant performance of the electrolyte. Second, the chlorinated carboxylate ester generates a chlorine-containing solid product LiCl (lattice energy about 853 kJ / mol) during thermal decomposition at the electrode interface, which can construct a dense and thermally stable interface protection layer SEI film (the activation energy of this SEI is greater than 120 kJ / mol, and the activation energy of a conventional SEI is only about 80 kJ / mol). The above-mentioned special interface chemical behavior not only inhibits the exothermic side reaction between the electrolyte and the electrode material, but also significantly increases the thermal runaway trigger threshold of the battery system.

[0024] In terms of interface dynamics, the special molecular structure of the chlorinated carboxylate ester on the R1 side and the R2 side regulates the solvation structure of lithium ions and the interface chemical behavior, and creatively solves the kinetic limitation in the fast charging process. In the chlorinated carboxylate ester, the R2 side has a longer chain length than the R1 side, so that the position of the Cl atom on the R2 side is relatively far from the carbonyl oxygen, making the Li + has a suitable coordination ability with the carbonyl oxygen in the chlorinated carboxylate ester, the coordination ability of the carbonyl oxygen in the chlorinated carboxylate ester with Li + is higher than that of the carbonyl oxygen in the disubstituted chlorinated carboxylate ester and the carbonyl oxygen in the monosubstituted chlorinated carboxylate ester with the Cl on the R2 side being closer to the carbonyl oxygen, and the coordination ability of the carbonyl oxygen in the chlorinated carboxylate ester with Li + is lower than that of the carbonyl oxygen in the unsubstituted carboxylate ester with Li + . On the one hand, this special molecular configuration makes the coordination ability of the carbonyl oxygen in the chlorinated carboxylate ester with Li + not too low, so as to moderately reduce the solvation energy barrier of lithium ions and enhance the solubility of lithium salt; on the other hand, this special molecular configuration makes the coordination ability of the carbonyl oxygen in the chlorinated carboxylate ester with Li + not too high, so as to keep the electrolyte with a relatively high ion transference number, overcoming the problem of the traditional carboxylate-based electrolyte that the solvation shell volume of Li + is too large due to the too strong coordination of the carboxylate with Li + . + + ​The migration speed is slowed down and the number of lithium ion migration is low. Therefore, the electrolyte can maintain excellent ion conduction characteristics in a wide temperature range. In addition, at the electrode interface, the SEI film layer formed by the decomposition of the chlorinated carboxylate ester has an ideal lithium ion transmission channel, which reduces the interface impedance during high-rate charging and discharging, and can effectively improve the lithium ion conductivity of the electrolyte, thereby improving the fast charging performance of the electrolyte.

[0025] More importantly, the safety performance of the electrolyte provided by the present application is improved without sacrificing the electrochemical performance, but through the unique molecular design of the chlorinated carboxylate ester, the safety and fast charging performance are simultaneously optimized. In addition, the electrolyte exhibits good compatibility with high-nickel positive electrode materials, which can not only resist oxidative decomposition under high voltage conditions, but also effectively inhibit the structural degradation of high-nickel positive electrode materials, providing an ideal electrolyte solution for developing advanced battery systems with high safety and fast charging performance, especially suitable for high-mobility unmanned aerial vehicle application scenarios with strict requirements for power characteristics and safety reliability.

[0026] In some embodiments, the chlorinated carboxylate ester can be a linear chlorinated carboxylate ester. The linear structure can moderately improve the coordination ability of the chlorinated carboxylate ester with lithium salt, thereby enhancing the solubility of lithium salt and improving the ionic conductivity of the electrolyte. The linear chlorinated carboxylate ester has lower volatility, further improving the thermal stability of the electrolyte. In addition, the linear chlorinated carboxylate ester also has lower viscosity, which can improve the ion transference number of the electrolyte, and still maintain good flowability at low temperature, improving the low temperature performance of the battery.

[0027] In some embodiments, the chlorinated carboxylate ester can include at least one of 3-chloropropyl acetate, 4-chlorobutyl acetate, 5-chloropentyl propionate, and 6-chlorohexyl acetate. The above-mentioned chlorinated carboxylate esters all have a molecular structure as formula (I).

[0028] In some embodiments, the solvent can also include a fluorinated carbonate, which is beneficial to further improve the interface stability of the electrolyte and the electrode. Further, the fluorinated carbonate can be a cyclic fluorinated carbonate, which is beneficial to promote the formation of a stable interface layer on the surface of the electrode material, further improving the interface stability and thermal stability of the battery.

[0029] Specifically, the fluorinated carbonate can have a structural general formula as shown in formula (II): (II), wherein R3 and R4 are independently selected from one of hydrogen, fluorine and fluorinated alkyl, and R3 and R4 are not hydrogen atoms at the same time. Further, the fluorinated carbonate can include at least one of fluorinated ethylene carbonate and difluorinated ethylene carbonate.

[0030] The volume ratio of chloro carboxylic acid ester and fluoro carbonate in the solvent of electrolyte can be 1:(0.1-1), which can make the electrolyte salt have good solubility and interface film forming performance, and further improve the battery performance and safety. For example, the volume ratio of chloro carboxylic acid ester and fluoro carbonate can be 1:0.1, 1:0.2, 1:0.25, 1:0.3, 1:0.4, 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9, 1:1 or any value within the range of any two values. Further, the volume ratio of chloro carboxylic acid ester and fluoro carbonate can be 1:(0.2-0.5).

[0031] In some embodiments, the lithium salt can include at least one of Li2SO4, LiClO4, LiNO3, LiCl, LiCF3SO3, LiPF6, Li(FSO2)2N, LiBF4, LiDFOB, Li(CF3CF2SO2)2N and Li(CF3SO2)2N, etc. It can be understood that the electrolyte salt includes but is not limited to the above lithium salt, and a suitable electrolyte salt can be selected according to different application requirements.

[0032] In some embodiments, the molar concentration of the electrolyte salt in the chloro carboxylic acid ester-based electrolyte can be 0.5 mol·L -1 ~3 mol·L -1 , which is beneficial to improve the conductivity and stability of the electrolyte. The molar concentration of the electrolyte salt in the chloro carboxylic acid ester-based electrolyte can be, for example, 0.5 mol·L -1 , 0.8 mol·L -1 , 1 mol·L -1 , 1.5 mol·L -1 , 1.8 mol·L -1 , 2 mol·L -1 , 3 mol·L -1 or any value within the range of any two values. The molar concentration of the electrolyte salt in the chloro electrolyte can be further 0.5 mol·L -1 ~2 mol·L -1 .

[0033] Compared with the prior art, the chloro carboxylic acid ester-based electrolyte provided by the embodiments of the present application has the following beneficial effects: 1. The chloro carboxylic acid ester in the electrolyte solvent has a unique molecular design, which introduces chlorine atoms in the relatively long side chain R2 of the carboxylic acid ester, improves the safety performance of the electrolyte, and improves the lithium performance of the electrolyte by adjusting the coordination ability of the carbonyl oxygen in the chloro carboxylic acid ester and Li + .

[0034] 2. The addition of a small amount of fluorinated carbonate helps to further improve the stability of the SEI, effectively isolating direct contact between the electrolyte and the electrode material, improving the cycle performance, rate performance and overall thermal stability of the battery.

[0035] The application further provides an electrochemical device, comprising a positive electrode sheet, a negative electrode sheet, a separator and an electrolyte, wherein the electrolyte is the aforementioned chloro-carboxylate-based electrolyte. Specifically, the separator is arranged between the positive electrode sheet and the negative electrode sheet.

[0036] The electrolyte is the aforementioned electrolyte. Since the electrolyte has good fast-charging performance and safety performance, the electrochemical device using the aforementioned electrolyte also has good electrochemical performance and high safety. The application of the electrolyte provided by the application in the battery provides a new path for realizing the battery of the high-maneuverable unmanned aerial vehicle.

[0037] Specifically, the electrochemical device can be a lithium battery, the positive electrode sheet can include lithium iron phosphate, lithium manganese iron phosphate, lithium cobaltate, nickel-cobalt-manganese ternary positive electrode material, and nickel-cobalt-aluminum ternary positive electrode material, and the negative electrode sheet can be a graphite negative electrode, a lithium metal negative electrode, etc.

[0038] The aforementioned chloro-carboxylate-based electrolyte and electrochemical device are further described below through specific embodiments.

[0039] Embodiment 1 The embodiment provides a chloro-carboxylate-based electrolyte (CPE1) of a lithium battery for a high-maneuverable unmanned aerial vehicle, which comprises: an electrolyte salt, a chloro-carboxylate, and a fluorinated carbonate. The electrolyte salt uses Li(FSO2)2N, the chloro-carboxylate is 3-chloropropyl acetate, the fluorinated carbonate is fluorinated carbonate ethylene, and the concentration of Li(FSO2)2N in the electrolyte salt is 1 mol·L -1 .

[0040] The specific preparation method comprises the following steps, all of which are carried out in an argon-filled glove box: Step S1, weigh 0.001 mol of Li(FSO2)2N salt.

[0041] Step S2, dissolve the salt in 0.9 ml of 3-chloropropyl acetate + 0.1 ml of fluorinated carbonate ethylene to obtain electrolyte CPE1.

[0042] Embodiment 2 The embodiment provides a kind of electrolyte (CPE2) of chloro carboxylic acid ester base lithium battery for high maneuverability unmanned aerial vehicle, the electrolyte includes: electrolyte salt, chloro carboxylic acid ester, fluorinated carbonate.Electrolyte salt uses Li (FSO2) 2N, chloro carboxylic acid ester is 4-chlorobutyl acetate, fluorinated carbonate is fluoroethylene carbonate, the concentration of Li (FSO2) 2N in electrolyte salt is 1mol·L -1 .

[0043] Specific preparation method includes the following steps, the following steps are carried out in argon-filled glove box: Step S1, 0.001 mol Li (FSO2) 2N salt is weighed.

[0044] Step S2, the salt is dissolved in 0.9ml 4-chlorobutyl acetate+0.1 ml fluoroethylene carbonate, and electrolyte CPE2 is obtained.

[0045] Example 3 The embodiment provides a kind of electrolyte (CPE3) of chloro carboxylic acid ester base lithium battery for high maneuverability unmanned aerial vehicle, the electrolyte includes: electrolyte salt, chloro carboxylic acid ester, fluorinated carbonate.Electrolyte salt uses Li (FSO2) 2N, chloro carboxylic acid ester is 5-chloropentyl acetate, fluorinated carbonate is fluoroethylene carbonate, the concentration of Li (FSO2) 2N in electrolyte salt is 0.7mol·L -1 .

[0046] Specific preparation method includes the following steps, the following steps are carried out in argon-filled glove box: Step S1, 0.001 mol Li (FSO2) 2N salt is weighed.

[0047] Step S2, the salt is dissolved in 0.9ml 5-chloropentyl acetate+0.1 ml fluoroethylene carbonate, and electrolyte CPE3 is obtained.

[0048] Example 4 The embodiment provides a kind of electrolyte (CPE4) of chloro carboxylic acid ester base lithium battery for high maneuverability unmanned aerial vehicle, the electrolyte includes: electrolyte salt, chloro carboxylic acid ester, fluorinated carbonate.Electrolyte salt uses Li (FSO2) 2N, chloro carboxylic acid ester is 6-chlorohexyl propionate, fluorinated carbonate is fluoroethylene carbonate, the concentration of Li (FSO2) 2N in electrolyte salt is 0.7mol·L -1 .

[0049] Specific preparation method includes the following steps, the following steps are carried out in argon-filled glove box: Step S1, 0.001 mol Li (FSO2) 2N salt is weighed.

[0050] Step S2, dissolve the salt in 0.9 ml 6-chlorohexyl propionate + 0.1 ml fluoroethylene carbonate to obtain electrolyte CPE3.

[0051] Comparative Example 1 This comparative example provides an electrolyte, which comprises: an electrolyte salt and a carboxylate-based solvent. Among them, the electrolyte salt uses LiFSI, the carboxylate-based solvent is ethyl acetate and fluoroethylene carbonate, the volume ratio of ethyl acetate and fluoroethylene carbonate in the carboxylate-based electrolyte is 9:1, and the electrolyte salt concentration is about 1 mol·L -1 .

[0052] The specific preparation method comprises the following steps, all of which are carried out in an argon-filled glove box: Step S1, weigh 0.001 mol of LiFSI salt.

[0053] Step S2, dissolve the salt in 0.9 ml ethyl acetate + 0.1 ml fluoroethylene carbonate and mix uniformly.

[0054] The electrolytes obtained in Comparative Examples 1-4 and Comparative Example 1 are subjected to the following tests: (I) self-extinguishing test: the same mass of electrolyte is placed in a positive electrode shell, and a lighter is used for ignition experiment, and the self-extinguishing time of the electrolyte is tested. The self-extinguishing time (SET) refers to the time during which the electrolyte or battery can self-extinguish after being affected by an external heat source such as ignition or high temperature, which reflects the safety of the electrolyte. Self-extinguishing performance judgment standard: SET≤6s·g -1 represents that the electrolyte is not flammable; 6 s·g -1 <SET≤20 s·g -1 represents that the electrolyte has flame retardancy; SET>20 s·g -1 represents that the electrolyte is flammable.

[0055] (II) negative electrode flame retardant test: a certain amount of electrolyte and lithiated graphite negative electrode sheet are placed in a positive electrode shell, and a lighter is used for ignition experiment, and the self-extinguishing time (SET) is tested. Self-extinguishing performance judgment standard: SET≤6s·g -1 represents that the electrolyte has flame retardancy for the lithiated negative electrode; SET>6 s·g -1 represents that the electrolyte has no flame retardancy for the lithiated graphite.

[0056] (III) electrical performance test conditions are as follows: the amount of electrolyte added is 40-100 μL, LiNi 0.8 Co 0.1 Mn 0.1 O2 as the positive electrode material, and graphite as the negative electrode material, to prepare Gr|| LiNi 0.8 Co0.1 Mn 0.1 O2full cell.

[0057] The battery prepared above was subjected to cycle performance test, and the test conditions were as follows: 25°C, voltage range 2.4-4.4V, charge and discharge rate 0.5, 1C, 2C, 3C, 5C, 6C, 8C, 10C, and the charge and discharge specific capacity and coulombic efficiency of the battery were measured.

[0058] The battery prepared above was subjected to fast discharge test, and the test conditions were as follows: 25°C, voltage range 2.4-4.4V, 1C charge and 10C discharge, and the discharge curve of the battery was measured.

[0059] The above results show that: As shown in Figure 1 , compared with Comparative Example 1 (traditional carboxylate-based electrolyte), the chloro carboxylate-based electrolyte in Example 1 is more difficult to ignite, and the self-extinguishing time is 0 s·g -1 , while the self-extinguishing time of Comparative Example 1 is 48 s·g -1 , which indicates that the chloro carboxylate-based electrolyte in Example 1 is non-flammable, which helps to reduce the safety hazard when the battery overheats. When the ignition experiment is carried out by adding lithiated graphite negative electrode, compared with Comparative Example 1, the electrolyte in Example 1 is difficult to ignite, and the self-extinguishing time is 0 s·g -1 , while the self-extinguishing time of Comparative Example 1 is 63 s·g -1 , which indicates that the electrolyte in Example 1 has high flame retardancy and can effectively prevent ignition when combined with the lithiated negative electrode.

[0060] As shown in Figure 2 and Figure 3 , the batteries prepared using the electrolyte of Example 1 and Comparative Example 1 in the Gr||NCM811 full cell rate performance test and fast discharge test, the specific capacity and coulombic efficiency of Example 1 are better than those of Comparative Example 1, which indicates that the chloro carboxylate-based electrolyte in Example 1 has better rate performance.

[0061] Therefore, the solvent provided in Examples 1-4 of the present application contains chloro carboxylate, which has non-flammable characteristics, and the chloro carboxylate-based electrolyte not only has good safety, but also has good electrochemical performance, which can ensure the safety and stable circulation of the battery.

[0062] It can be understood that the above embodiments are only exemplary embodiments adopted for illustrating the principles of the present application, and the present application is not limited thereto. Various modifications and improvements can be made by those skilled in the art without departing from the spirit and essence of the present application, and these modifications and improvements are also considered to be within the protection scope of the present application.

Claims

1. An electrolyte for a chlorocarboxylic acid ester-based lithium battery used in a high-maneuverability unmanned aerial vehicle, characterized in that, The electrolyte comprises an electrolyte salt and a solvent, wherein the electrolyte salt comprises a lithium salt, and the solvent comprises a chlorocarboxylic acid ester having a general structural formula as shown in formula (I): （Ⅰ）， Wherein, R1 is an alkyl group with 1 to 3 carbon atoms, R2 is selected from chloroalkyl groups, R2 has 2 to 10 carbon atoms, and the number of carbon atoms in R2 is greater than the number of carbon atoms in R1.

2. The electrolyte according to claim 1, characterized in that, The chlorocarboxylic acid ester is a linear chlorocarboxylic acid ester.

3. The electrolyte according to claim 1, characterized in that, The chlorocarboxylic acid esters include at least one of 3-chloropropyl acetate, 4-chlorobutanol acetate, 1-butanol, 4-chloropropionate, and 1-pentanol, 5-chloro, 1-propionate.

4. The electrolyte according to claim 1, characterized in that, The solvent also includes fluorocarbonate.

5. The electrolyte according to claim 4, characterized in that, The fluorocarbonate is a cyclic fluorocarbonate.

6. The electrolyte according to claim 5, characterized in that, The fluorocarbonate has a general structural formula as shown in formula (II): （Ⅱ）， R3 and R4 are each independently selected from hydrogen, fluorine, and fluoroalkyl groups, and R3 and R4 are not both hydrogen atoms.

7. The electrolyte according to claim 4, characterized in that, The fluorocarbonate includes at least one of fluoroethylene carbonate and difluoroethylene carbonate.

8. The electrolyte according to claim 4, characterized in that, In the solvent, the volume ratio of the chlorocarboxylic acid ester to the fluorocarbonate is 1:(0.1~1).

9. The electrolyte according to claim 1, characterized in that, The lithium salt includes at least one of Li2SO4, LiClO4, LiNO3, LiCl, LiCF3SO3, LiPF6, Li(FSO2)2N, LiBF4, LiDFOB, Li(CF3CF2SO2)2N, and Li(CF3SO2)2N.

10. An electrochemical device, characterized in that, It includes a positive electrode, a negative electrode, a separator, and an electrolyte, wherein the separator is disposed between the positive electrode and the negative electrode, and the electrolyte is the electrolyte as described in any one of claims 1 to 9.

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