Organic electrolyte with hexagonal boron nitride and application thereof

Abstract

The invention relates to an organic electrolyte with hexagonal boron nitride and application thereof, and belongs to the technical field of energy storage materials, the organic electrolyte comprises hexagonal boron nitride h-BN, sodium perchlorate NaClO4, ethylene carbonate EC, propylene carbonate PC and fluoroethylene carbonate FEC. According to the invention, it is comprehensively considered that acidic solid particles can capture anions to form a space charge layer characterized by cation aggregation, so that a relatively high Na < + > transfer number is obtained, and even a relatively high total conductivity can be obtained in some cases. In addition, existing polar bonds can adsorb solvent molecules, so that the reaction activity of the material to a metal negative electrode is reduced. In conclusion, the concentration polarization is reduced, the dendritic crystal forming probability is reduced, compared with a traditional electrolyte, the desolvation energy barrier of the electrolyte is reduced, the internal dynamic process of the sodium ion battery is accelerated, and the problems of poor rate capability and cycle performance of the conventional electrolyte are solved; and the electrochemical performance of the sodium-ion battery at high and low temperatures is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of energy storage materials, and in particular relates to an organic electrolyte containing hexagonal boron nitride and application thereof. Background Art

[0002] Currently, rechargeable lithium-ion batteries (LIBs) have been widely used in portable electronic devices and electric vehicles due to their long life and high energy density. However, limited lithium reserves have hindered the development of lithium-ion batteries. Therefore, sodium-ion batteries (SIBs) have attracted widespread attention due to their high abundance and ubiquitous distribution of resources. Since SIBs are lower in cost and lower in energy density than LIBs, SIBs are undoubtedly promising candidates for grid-scale energy storage systems. However, the electrochemical properties of SIBs, including capacity, efficiency, and power density, deteriorate significantly when the temperature decreases / increases. The operating temperature has a significant effect on the electrochemical performance of SIBs. When the operating temperature drops below 0°C, the Na in the battery electrode material decreases. + The diffusion rate of Na2+ slows down, and the solvated Na2+ at the electrode / electrolyte interface + The desolvation process is slow, resulting in severe polarization of the electrode reaction. The battery can only provide limited discharge capacity and cannot even work under low temperature conditions. Under high temperature conditions, the ion diffusion rate increases, thereby achieving fast reaction kinetics and excellent rate performance. However, the thermal stability of the electrolyte, electrode materials, solid electrolyte interphase (SEI) and positive electrode electrolyte interphase (CEI) also poses a huge challenge to the exploration of high temperature operation. Traditional ester-based electrolytes will solidify at low temperatures, hindering the transmission of sodium ions, and there are many side reactions at high temperatures, which makes it difficult to meet the current requirements for wide-temperature sodium-ion batteries.

[0003] Therefore, a new technical solution is urgently needed to further solve the above problems. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide an organic electrolyte containing hexagonal boron nitride and its application, and a sodium ion battery prepared by using the organic electrolyte has high-rate performance in a wide temperature range.

[0005] An organic electrolyte with hexagonal boron nitride, comprising hexagonal boron nitride h-BN, sodium perchlorate NaClO 4 , ethylene carbonate EC, propylene carbonate PC and fluoroethylene carbonate FEC.

[0006] The sodium perchlorate NaClO 4 The concentration is 1 mol / L, the hexagonal boron nitride h-BN is 100 g / L, and the volume ratio of ethylene carbonate EC to propylene carbonate PC is 1:1.

[0007] The invention discloses an application of an organic electrolyte containing hexagonal boron nitride for preparing a sodium ion battery.

[0008] Through the above design scheme, the present invention can bring the following beneficial effects: the present invention provides an organic electrolyte with hexagonal boron nitride and its application, the prepared electrolyte is simple to prepare and the raw materials are cheap; in addition, considering that the acidic solid particles can capture anions to form a space charge layer characterized by cation aggregation, a higher Na + The number of transfers can be increased, and in some cases even a higher total conductivity can be obtained. In addition, the polar bonds present can adsorb solvent molecules and reduce their reactivity to the metal negative electrode. In summary, this not only means reduced concentration polarization and reduced probability of dendrite formation, but also reduces the desolvation energy barrier of the electrolyte compared to traditional electrolytes, accelerates the kinetic process inside the sodium ion battery, solves the problem of poor rate performance and cycle performance of conventional electrolytes, and improves the electrochemical performance of sodium ion batteries at high and low temperatures. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] The present invention is further described below with reference to the accompanying drawings and specific embodiments:

[0010] Figure 1 This is a performance diagram of an organic electrolyte with hexagonal boron nitride applied to a NVPF||Na metal battery at 25°C in a specific embodiment of the present invention, wherein a) rate performance; b) charge and discharge curve; c) long cycle performance.

[0011] Figure 2 The electrolyte prepared in Example 1 of the present invention is a specific implementation scheme of an organic electrolyte with hexagonal boron nitride. The electrolyte in Comparative Example 1 is applied to the performance graph of NVPF||Na metal battery at 40°C and 45°C. Among them, a) -40°C rate performance; b) -40°C cycle performance; c) -40°C charge and discharge curve; d) 45°C rate performance; e) 45°C cycle performance. DETAILED DESCRIPTION

[0012] The present invention will be described in detail below in conjunction with the accompanying drawings and embodiments. The described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0013] The preparation method is specifically described below in conjunction with the accompanying drawings and examples. However, it should be understood that the examples are only used to illustrate the present invention and do not limit the scope of protection of the present invention in any way.

[0014] Example 1

[0015] This example provides a NVPF||Na metal battery, using an organic electrolyte having hexagonal boron nitride, and the specific steps are as follows:

[0016] Step (1), preparation of electrolyte: prepare sodium ion battery electrolyte in a glove box filled with argon, weigh 100 mg h-BN, disperse it in FEC electrolyte (denoted as RCE) with a solvent of EC:PC ratio of 1:1, salt of 1 mol NaClO4, and additive of 5% by mass, and stir evenly to obtain 100 g / L h-BN+Blank sodium ion battery electrolyte (denoted as 100BN);

[0017] Step (2), preparation of the positive electrode sheet: sodium vanadium fluorophosphate (NVPF), acetylene black, and polyvinylidene fluoride (PVDF) are mixed in a mass ratio of 80:10:10 and fully ground, and N-methylpyrrolidone (NMP) is added to form a slurry, which is coated on the surface of the aluminum foil, and then placed in a vacuum drying oven at 120°C for 12 hours. Finally, the aluminum foil coated with the active material is cut into 14 mm discs to form a positive electrode sheet. The loading amount of the active material in the positive electrode sheet is about 1.5 mg / cm 2 ;

[0018] Step (3), assembly of NVPF||Na metal battery: assembling CR2032 button cells in a glove box filled with argon gas, using NVPF as the positive electrode, metallic sodium as the negative electrode, glass fiber as the separator and the electrolyte in this embodiment to assemble into a sodium ion battery;

[0019] Step (4), electrochemical performance test of sodium ion battery: The sodium ion battery in step (3) of this embodiment is placed in a constant temperature and humidity chamber at 25°C, -40°C and 45°C and subjected to rate charge and discharge test (1C = 128mAh / mg, voltage range 2-4.4V) on a blue power test system. The test results are shown in Figure 1 and Figure 2 .

[0020] Comparative Example 1

[0021] This example provides a NVPF||Na metal battery, and the specific steps are as follows:

[0022] Step (1), electrolyte preparation: weigh 0.5 mL EC and 0.5 mL PC, add 122 mg NaClO 4 , after dissolution, 5% FEC (denoted as RCE) was added according to the mass fraction;

[0023] Step (2), preparation of positive electrode sheet: NVPF, acetylene black, polyvinylidene fluoride (PVDF) are mixed in a mass ratio of 80:10:10 and fully ground, N-methylpyrrolidone (NMP) is added to form a slurry, coated on the surface of aluminum foil, and then placed in a vacuum drying oven at 120°C for 12 hours, and finally the aluminum foil coated with active material is cut into 14mm discs to form positive electrode sheets. The loading amount of active material in the positive electrode sheet is about 1.5mg / cm 2 ;

[0024] Step (3), assembly of NVPF||Na metal battery: assemble CR2032 button batteries in a glove box filled with argon gas, using NVPF as the negative electrode, metallic sodium as the negative electrode, glass fiber as the separator and the electrolyte in step (1) of this embodiment to assemble into a sodium ion battery;

[0025] Step (4), electrochemical performance test of sodium ion battery: The sodium ion battery in step (3) of this embodiment is placed in a constant temperature and humidity chamber at 25°C, -40°C and 45°C and subjected to rate charge and discharge test (1C = 128mAh / g, voltage range 2-4.4V) on a blue power test system. The test results are shown in Figure 1 and Figure 2 .

[0026] First, the battery was subjected to 1C, 5C, 10C, 20C, 30C and 40C (1C = 128 mA g -1 ) performance, the capacity of the sodium-ion battery constructed with 100BN electrolyte is generally higher than that of RCE electrolyte, with the capacities of 98 and 76 mA g at 40C, respectively. -1 The charge and discharge curves at different rates show that the first efficiency of the battery using 100BN electrolyte is 92%, the polarization potential is 0.2V, and the RCE is 90% and 0.5V ( Figure 1 a and 1b). Subsequently, the battery long cycle performance test was carried out using a current density of 5C. The battery using the RCE electrolyte decayed rapidly and failed after 1600 cycles, with a remaining capacity of 45 mAh g -1 The 100BN electrolyte has less free solvent and is highly compatible with sodium, so the battery using it has an ultra-long cycle performance (6200 cycles, with a residual capacity of 72 mAh g -1 )( Figure 1 c). The rate performance at -40°C was then investigated, with the rates being 0.1C, 0.2C, 0.4C, 0.8C and 1.2C. The 100BN battery has a capacity within this current density range, while the capacity of the RCE is almost zero at 0.8C and above ( Figure 2a). Then the battery cycle performance was tested at -40°C with a 0.1C cycle. The 100BN battery had extremely high stability and almost no attenuation after 100 cycles. However, the RCE battery attenuated faster and had a lower capacity ( Figure 2 b). This is because the intersolvent forces increase with decreasing temperature, which will lead to an increase in the desolvation energy of sodium ions, and ultimately the battery performance deteriorates. h-BN adsorbs solvent molecules, which can weaken the intersolvent forces, so the performance of 100BN is better than that of RCE electrolyte. Finally, the battery performance at 45°C was investigated, and the rate performance was tested at 1C, 5C, 10C, 20C, 30C and 40C. The RCE battery showed poor electrochemical performance, and the 40C capacity was only 48mAhg -1 , while 100BN is 112mAh g -1 , which is much larger than that of RCE electrolyte. The long cycle performance test was carried out at a current of 30C. The battery capacity of 100BN was 105mAh g after 920 stable cycles. -1 , the attenuation per turn is only 0.0067% ( Figure 2 d and 2e).

[0027] In summary, the present invention improves the high and low temperature electrochemical performance of sodium ion batteries by configuring an organic electrolyte with hexagonal boron nitride, so that the battery has stable cycle performance and high rate performance. Therefore, the electrolyte provided by the present invention has potential application value.

[0028] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to the embodiments will be apparent to one skilled in the art, and the general principles defined in the present invention may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. An organic electrolyte having hexagonal boron nitride, characterized in that: Including hexagonal boron nitride h-BN, sodium perchlorate NaClO4, ethylene carbonate EC, propylene carbonate PC and fluoroethylene carbonate FEC.

2. The organic electrolyte having hexagonal boron nitride according to claim 1, characterized in that: The concentration of sodium perchlorate NaClO4 is 1 mol / L, the concentration of hexagonal boron nitride h-BN is 100 g / L, and the volume ratio of ethylene carbonate EC to propylene carbonate PC is 1:

1.

3. An application of an organic electrolyte having hexagonal boron nitride, characterized in that: Used to prepare sodium ion batteries.

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