A battery

Abstract

The present invention relates to the technical field of batteries, and particularly to a battery. The battery includes a positive electrode plate and an electrolyte. In the XRD pattern of the positive electrode plate, there are two diffraction peaks at 15° - 20° and 40° - 43°. The peak intensity of the diffraction peak at 15° - 20° is H1, the peak intensity of the diffraction peak at 40° - 43° is H2, and the electrolyte includes propylene carbonate. Based on the total weight of the electrolyte, the weight content of propylene carbonate is A. Then, the battery satisfies: H1 / H2 + A ≥ 0.6. The battery of the present invention can reduce interfacial reactions and improve the cycle stability and storage performance of the battery.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and particularly to a battery. Background Art

[0002] Sodium-ion batteries have broad application prospects due to their comprehensive advantages such as low cost, rich resources, and environmental friendliness. Their working principle is similar to that of lithium-ion batteries, mainly using the back-and-forth insertion and extraction of sodium ions between the positive and negative electrodes to achieve energy storage and release. However, the electrolyte of sodium-ion batteries will react on the surface of the positive electrode sheet because the usual electrolyte cannot form a good CEI film on the positive electrode, resulting in unstable cycling performance and poor storage performance of sodium-ion batteries. Summary of the Invention

[0003] An object of the present invention is to overcome the above problems existing in the prior art and provide a battery. The battery of the present invention can reduce interfacial reactions and improve the cycling stability and storage performance of the battery.

[0004] The present invention provides a battery, which includes a positive electrode sheet and an electrolyte. In the XRD pattern of the positive electrode sheet, there are two diffraction peaks at 15° - 20° and 40° - 43°. The peak intensity of the diffraction peak at 15° - 20° is H1, and the peak intensity of the diffraction peak at 40° - 43° is H2. And the electrolyte includes propylene carbonate. Based on the total weight of the electrolyte, the weight content of propylene carbonate is A. Then the battery satisfies: H1 / H2 + A ≥ 0.6.

[0005] In one example, the battery satisfies: 0.6 ≤ H1 / H2 + A ≤ 1.4.

[0006] In one example, the peak height H1 of the diffraction peak at 15° - 20° and the peak height H2 of the diffraction peak at 40° - 43° satisfy: H1 / H2 ≥ 0.5.

[0007] In one example, the positive electrode sheet includes a composite oxide, and the chemical formula of the composite oxide is Na x Ni a Fe b Mn c A y O2, where x satisfies 0.7 ≤ x ≤ 1, y satisfies 0 ≤ y ≤ 0.5, and A includes one or more of Li, Mg, Zn, Co, Ca, Ba, Sr, Al, B, Cr, V, Zr, Ti, Sn, Mo, Ru, Si, Sb, Nb, and Te.

[0008] Through the above technical solutions, the present invention has at least the following advantages compared with the prior art:

[0009] The battery of the present invention enables the electrolyte to form a CEI film on the surface of the positive electrode sheet through the synergistic cooperation of the positive electrode sheet and the electrolyte, thereby reducing the interfacial reaction and further improving the cycle stability and storage performance of the battery. Description of the Drawings

[0010] Figure 1 Shown is the XRD pattern of the positive electrode sheet provided by an embodiment of the present invention.

[0011] Figure 2 Shown is the XRD pattern of the positive electrode sheet provided by a comparative example of the present invention. Detailed Description of the Invention

[0012] The following provides a detailed description of the specific embodiments of the present invention. It should be understood that the specific embodiments described herein are only for explaining and illustrating the present invention and are not used to limit the present invention.

[0013] The present invention provides a battery, the battery includes a positive electrode sheet and an electrolyte. In the XRD pattern of the positive electrode sheet, there are two diffraction peaks at 15° - 20° and 40° - 43°. The peak intensity of the diffraction peak at 15° - 20° is H1, the peak intensity of the diffraction peak at 40° - 43° is H2, and the electrolyte includes propylene carbonate. Based on the total weight of the electrolyte, the weight content of propylene carbonate is A, then the battery satisfies: H1 / H2 + A ≥ 0.6.

[0014] In the XRD pattern of the positive electrode sheet, it shows that there are two diffraction peaks at 15° - 20° and 40° - 43° respectively. Among them, the diffraction peak at 15° - 20° is the diffraction peak of the (003) crystal plane, and the diffraction peak at 40° - 43° is the diffraction peak of the (104) crystal plane. The presence of the diffraction peaks of the above two crystal planes in the XRD pattern of the positive electrode sheet indicates that the structural stability of the positive electrode sheet is relatively high, which can reduce the battery inactivation, expansion, rupture, and side reactions (such as gas generation, etc.) between the positive electrode sheet and the electrolyte due to temperature changes during the charge and discharge process, thereby improving the cycle stability of the battery.

[0015] The battery can satisfy: H1 / H2 + A ≥ 0.6 (for example, 0.6, 0.7, 0.8, 0.9, 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2). The inventors of the present invention found that when the positive electrode sheet and the electrolyte meet the above specific conditions, through the synergistic cooperation of the positive electrode sheet and the electrolyte, that is, the positive electrode of the present invention can promote the formation of a passivation film of PC in the electrolyte on the positive electrode surface, reduce the particle rupture and crystal orientation transformation of the positive electrode material during the charge and discharge process, and at the same time can reduce the interfacial reaction and improve the cycle stability and storage performance of the battery.

[0016] In the present invention, through the synergistic cooperation of the positive electrode sheet and the electrolyte, it has been possible to enable the battery to achieve better cycle stability and storage performance than the prior art. To further improve the effect, one or more technical features can be further optimized.

[0017] In one example, the battery satisfies: 0.6 ≤ H1 / H2 + A ≤ 1.4.

[0018] In one example, as Figure 1 described, in the XRD pattern of the positive electrode sheet, there are two diffraction peaks at 15° - 20° and 40° - 43° respectively. The peak intensity H1 of the diffraction peak at 15° - 20° and the peak intensity H2 of the diffraction peak at 40° - 43° satisfy: H1 / H2 ≥ 0.5. When H1 / H2 < 0.5, the structural stability of the positive electrode sheet is poor, and the electrolyte cannot form a good CEI film on the surface of the positive electrode sheet, resulting in poor cycle stability and storage performance of the battery; when H1 / H2 ≥ 0.5, the positive electrode sheet can have good structural stability, which can promote the formation of a good CEI film on the surface of the positive electrode sheet, reduce the interfacial reaction, and thus improve the cycle stability and storage performance of the battery.

[0019] In one example, H1 / H2 is 0.5 - 0.9 (for example, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9). By further limiting the value of H1 / H2, the positive electrode sheet can have higher structural stability and lithium ion insertion / extraction, and at the same time can improve the structural stability of the CEI film, reduce the interfacial reaction between the positive electrode sheet and the electrolyte, and improve the long cycle performance and storage performance of the battery.

[0020] In one example, the electrolyte may include propylene carbonate (PC). Based on the total weight of the electrolyte, the weight content of propylene carbonate is 10wt% - 50wt% (for example, 10wt%, 15wt%, 20wt%, 25wt%, 30wt%, 35wt%, 40wt%, 45wt%, 50wt%). When the weight content of propylene carbonate is lower than 10wt%, the cycle performance and storage performance deteriorate sharply; when the weight content of propylene carbonate is higher than 50wt%, the cycle performance and storage performance deteriorate sharply. When the weight content of propylene carbonate is limited within the above specific range, PC can form a passivation film on the surface of the positive electrode material in the present invention, fully protecting the electrolyte from being largely decomposed by the positive electrode. If the content is too low, the passivation film will not form evenly, but if the content is too high, the passivation film will be too thick and the impedance will be too large, resulting in poor battery performance.

[0021] In one example, based on the total weight of the electrolyte, the weight content of propylene carbonate is 15.4 wt% to 40.6 wt%. By further defining the content range of propylene carbonate, the synergistic effect between propylene carbonate and the positive electrode sheet can be further improved, promoting a higher stability of the CEI film formed on the surface of the positive electrode sheet, thereby further improving the long cycle performance and storage performance of the battery.

[0022] In one example, based on the total weight of the electrolyte, the weight content of propylene carbonate is 20 wt% to 35 wt%. By further defining the content range of propylene carbonate, the synergistic effect between propylene carbonate and the positive electrode sheet can be further improved, promoting a higher stability of the CEI film formed on the surface of the positive electrode sheet, thereby further improving the long cycle performance and storage performance of the battery.

[0023] According to a specific embodiment, the positive electrode sheet includes a composite oxide, and the chemical formula of the composite oxide is Na x Ni a Fe b Mn c A y O2, where x satisfies 0.7 ≤ x ≤ 1.05 (for example, 0.7, 0.75, 0.8, 0.85, 0.9, 0.951, 1, 1.05), y satisfies 0 ≤ y ≤ 0.5 (for example, 0, 0.05, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5), a satisfies 0.3 ≤ a ≤ 1 (for example, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1), b satisfies 0.1 ≤ b ≤ 0.5 (for example, 0.1, 0.2, 0.3, 0.4, 0.5), c satisfies 0.1 ≤ c ≤ 0.5 (for example, 0.1, 0.2, 0.3, 0.4, 0.5), and A includes one or more of Li, Mg, Zn, Co, Ca, Ba, Sr, Al, B, Cr, V, Zr, Ti, Sn, Mo, Ru, Si, Sb, Nb, and Te. In the present invention, the positive electrode sheet including the composite oxide can satisfy H1 / H2 ≥ 0.5.

[0024] In the chemical formula Na x Ni a Fe b Mn c A y O2 of the composite oxide, the elements conform to the principle that the algebraic sum of the positive and negative valences of the elements in the compound is zero.

[0025] In one example, x satisfies 0.9 ≤ x ≤ 1.03.

[0026] In one example, y satisfies 0.01 ≤ y ≤ 0.1.

[0027] In one example, when the composite oxide does not include the doping element A, that is, when y = 0, the chemical formula of the composite oxide is Na x Ni a Fe b Mn c O2. The chemical formula Na x Ni a Fe b Mn c O2 follows the principle that the algebraic sum of the positive and negative valence of each element in the compound is zero.

[0028] In one example, the composite oxide includes the doping element A. The composite oxide including the doping element A has higher positive electrode activity stability, avoids the dissolution of transition metal elements during charge and discharge, improves the corrosion in the electrolyte, improves the stability of the positive electrode material, and at the same time makes the CEI film formed on the surface of the positive electrode sheet more stable and the interfacial reaction less, thereby improving the long cycle performance and storage performance of the battery.

[0029] In one example, the composite oxide includes NaNi 0.8 Fe 0.1 Mn 0.1 O2, NaNi 0.6 Fe 0.2 Mn 0.2 O2, NaNi 0.6 Fe 0.25 Mn 0.15 O2, NaNi 0.5 Fe 0.2 Mn 0.3 Al 0.01 O 2， NaNi 0.5 Fe 0.2 Mn 0.3 O2 and NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 O2 and one or more of them.

[0030] In one example, the positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer. The positive electrode active material layer is located on one or both surfaces of the positive electrode current collector. The positive electrode active material layer includes a positive electrode material, and the positive electrode material includes a composite oxide.

[0031] In one example, the positive electrode current collector includes aluminum foil or porous aluminum foil.

[0032] In one example, the positive electrode active material layer includes a composite oxide.

[0033] According to a specific embodiment, based on the total weight of the positive electrode active material layer, the weight content of the composite oxide is 92 wt% to 99 wt% (for example, 92 wt%, 93 wt%, 94 wt%, 95 wt%, 96 wt%, 97 wt%, 98 wt%, 99 wt%).

[0034] In one example, based on the total weight of the positive electrode active material layer, the weight content of the composite oxide is 95 wt% to 98 wt%.

[0035] The composite oxide can be prepared by the following method:

[0036] (1) Mix a soluble Ni salt, a soluble Fe salt, a soluble Mn salt, and a soluble salt containing Al element, add them to a solvent to obtain a mixed solution; adjust the pH of the mixed solution to obtain a coprecipitate containing Ni, Fe, Mn, and Al, and obtain a composite precursor through solid-liquid separation (such as filtration).

[0037] (2) Dry the composite precursor, mix it with sodium carbonate after drying, and perform high-temperature sintering.

[0038] In one example, the soluble Ni salt includes one or more of nickel sulfate and nickel nitrate.

[0039] In one example, the soluble Fe salt includes one or more of iron sulfate and iron nitrate.

[0040] In one example, the soluble Mn salt includes one or more of manganese sulfate and manganese nitrate.

[0041] In one example, the soluble salt containing Al element includes one or more of aluminum nitrate.

[0042] In one example, the molar ratio of the soluble Ni salt, the soluble Fe salt, and the soluble Mn salt is a:b:c.

[0043] In one example, the solvent includes one or more of water, ethanol, acetone, toluene, and ether.

[0044] In one example, the pH of the mixed solution is adjusted to 3 to 12.

[0045] In one example, the conditions for drying are: the temperature is 100°C to 1000°C (for example, 100°C, 200°C, 300°C, 400°C, 500°C, 600°C, 700°C, 800°C, 900°C, 1000°C), and the time is 1 h to 20 h (for example, 1 h, 3 h, 5 h, 8 h, 10 h, 13 h, 15 h, 18 h, 20 h).

[0046] In one example, the molar ratio of the sodium carbonate to the soluble Ni salt is x:a.

[0047] In one example, the conditions for the high-temperature sintering are as follows: the temperature is 770°C to 1000°C (for example, 770°C, 750°C, 800°C, 850°C, 900°C, 950°C, 1000°C), the sintering time is 10 h to 40 h (for example, 10 h, 15 h, 20 h, 25 h, 30 h, 35 h, 40 h), and the sintering atmosphere is an air atmosphere, an air atmosphere with compressed air passed through, an N2 gas atmosphere, or an oxygen atmosphere.

[0048] In one example, the conditions for the high-temperature sintering are as follows: the temperature is 800°C to 900°C, the sintering time is 20 h to 38 h, and the sintering atmosphere is an N2 gas atmosphere.

[0049] According to a specific embodiment, the positive electrode active material layer includes a conductive agent and a binder.

[0050] In one example, the conductive agent includes one or more of conductive carbon black, acetylene black, Ketjen black, conductive graphite, conductive carbon fiber, carbon nanotube, metal powder, and carbon fiber.

[0051] In one example, the binder includes one or more of polyvinylidene fluoride, styrene-butadiene rubber, styrene-butadiene latex, polytetrafluoroethylene, and polyethylene oxide.

[0052] According to a specific embodiment, based on the total weight of the positive electrode active material layer, the weight content of the conductive agent is 0.01 wt% to 7 wt% (for example, 0.01 wt%, 0.05 wt%, 0.1 wt%, 0.5 wt%, 1 wt%, 3 wt%, 5 wt%, 7 wt%), and the weight content of the binder is 0.1 wt% to 8 wt% (for example, 0.1 wt%, 0.5 wt%, 1 wt%, 3 wt%, 5 wt%, 8 wt%).

[0053] In one example, based on the total weight of the positive electrode active material layer, the weight content of the conductive agent is 0.1 wt% to 2 wt%, and the weight content of the binder is 0.1 wt% to 5 wt%.

[0054] In one example, the electrolyte includes sodium bis(fluorosulfonyl)imide (NaFSi). The inventors of the present invention have found that when the electrolyte includes NaFSi, the composite oxide in the positive electrode sheet satisfying H1 / H2≥0.5 can promote the formation of a CEI film on the surface of the positive electrode sheet by the anions of NaFSi, reduce the interfacial reaction, and at the same time, PC in the electrolyte can also promote the dissociation of NaFSi, improve the film-forming efficiency, and thus further improve the cycle stability and storage performance of the battery.

[0055] According to a specific embodiment, based on the total weight of the electrolyte, the weight content of NaFSi is 0.1 wt% to 10 wt% (for example, 0.1 wt%, 0.5 wt%, 1 wt%, 1.5 wt%, 2 wt%, 2.5 wt%, 3 wt%, 3.5 wt%, 4 wt%, 4.5 wt%, 5 wt%, 5.5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt%).

[0056] In one example, based on the total weight of the electrolyte, the weight content of NaFSi is 0.2 wt% to 6 wt%.

[0057] In one example, the electrolyte further includes ethylene carbonate (EC).

[0058] According to a specific embodiment, based on the total weight of the electrolyte, the weight content of ethylene carbonate is less than 5 wt%. Ethylene carbonate can also promote the dissociation of NaFSi, but when ethylene carbonate participates in dissociation, it will cause a reaction on the surface of the positive electrode sheet, affecting the components of the CEI film, thereby deteriorating the battery performance. By limiting the content of ethylene carbonate in the electrolyte to the above specific range, the influence of ethylene carbonate on the components of the CEI film can be reduced, so that ethylene carbonate has a smaller impact on the battery performance.

[0059] In a preferred example, the electrolyte does not include ethylene carbonate. When the electrolyte does not include ethylene carbonate, it is possible to avoid the decomposition and volatilization of ethylene carbonate during the charge and discharge process of the battery, reduce the gas generation of the battery, and thus improve the cycle performance and storage performance of the battery.

[0060] In one example, the electrolyte further includes 1-hexylpyridinium tetrafluoroborate (HTL), and 1-hexylpyridinium tetrafluoroborate has the structure shown in formula (I).

[0061]

[0062] As can be seen from the structure shown in formula (I), 1-hexylpyridinium tetrafluoroborate (HTL) includes cations and anions. These ions can move in the electrolyte so that current can be conducted in the sodium-ion battery, which can improve the stability of the electrolyte and at the same time form a dense protective film on the surface of the sodium-ion positive electrode.

[0063] According to a specific embodiment, based on the total weight of the electrolyte, the weight content of 1-hexylpyridinium tetrafluoroborate is 0.1 wt% to 3 wt% (for example, 0.1 wt%, 0.5 wt%, 1 wt%, 1.5 wt%, 2 wt%, 2.5 wt%, 3 wt%).

[0064] In one example, based on the total weight of the electrolyte, the weight content of 1-hexylpyridinium tetrafluoroborate is 0.5 wt% to 0.8 wt%.

[0065] When the HTL additive in the electrolyte meets the positive electrode sheet with H1 / H2≥0.5, it can form a dense protective film on the surface of the positive electrode, significantly improving the cycle stability and storage performance of the sodium-ion battery.

[0066] In one example, the electrolyte includes an electrolyte and an additive.

[0067] In one example, the electrolyte includes one or more of sodium hexafluorophosphate (NaPF6) and sodium bis(fluorosulfonyl)imide (NaFSi).

[0068] In one example, the additive includes one or more of ethylene carbonate (VC), vinylene sulfate, and 1,3-propane sultone.

[0069] According to a specific embodiment, based on the total weight of the electrolyte, the weight content of the electrolyte is 6 wt% to 20 wt% (for example, 6 wt%, 8 wt%, 10 wt%, 12 wt%, 15 wt%, 18 wt%, 20 wt%), and the weight content of the additive is 1 wt% to 15 wt% (for example, 1 wt%, 3 wt%, 5 wt%, 7 wt%, 10 wt%, 12 wt%, 15 wt%).

[0070] In one example, based on the total weight of the electrolyte, the weight content of the electrolyte is 9 wt% to 15 wt%, and the weight content of the additive is 2 wt% to 10 wt%.

[0071] In one example, the battery includes a negative electrode sheet and a separator.

[0072] The negative electrode sheet can be a conventional negative electrode sheet in the art. For example, the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer located on one or both sides of the surface of the negative electrode current collector. The negative electrode active material layer includes a negative electrode material, a conductive agent, a binder, and a thickener.

[0073] In one example, the negative electrode current collector includes a copper foil or a porous copper foil.

[0074] In one example, the negative electrode material includes one or more of artificial graphite, natural graphite, mesophase carbon microspheres, hard carbon, soft carbon, nanosilicon, silicon oxide material (SiO x (0 < x < 2)) and silicon-carbon materials.

[0075] In one example, the thickener includes one or more of sodium carboxymethyl cellulose and styrene-butadiene rubber.

[0076] According to a specific embodiment, based on the total weight of the negative electrode active material layer, the weight content of the negative electrode material is 92 wt% to 99 wt% (for example, 92 wt%, 93 wt%, 94 wt%, 95 wt%, 96 wt%, 97 wt%, 98 wt%, 99 wt%), the weight content of the conductive agent is 0.1 wt% to 7 wt% (for example, 0.1 wt%, 0.5 wt%, 1 wt%, 3 wt%, 5 wt%, 7 wt%), the weight content of the binder is 0.1 wt% to 7 wt% (for example, 0.1 wt%, 0.5 wt%, 1 wt%, 3 wt%, 5 wt%, 7 wt%), and the weight content of the thickening agent is 0.1 wt% to 7 wt% (for example, 0.1 wt%, 0.5 wt%, 1 wt%, 3 wt%, 5 wt%, 7 wt%).

[0077] In one example, based on the total weight of the negative electrode active material layer, the weight content of the negative electrode material is 94 wt% to 98 wt%, the weight content of the conductive agent is 0.5 wt% to 2 wt%, the weight content of the binder is 0.5 wt% to 2 wt%, and the weight content of the thickening agent is 0.5 wt% to 2 wt%.

[0078] According to a specific embodiment, the battery is a sodium ion battery.

[0079] The separator can be a conventional separator in the art. For example, the separator includes one or more of a polyethylene film and a polypropylene film.

[0080] The present invention will be described in detail below through examples. The examples described in the present invention are only a part of the examples of the present invention, rather than all the examples. All other examples obtained by those of ordinary skill in the art based on the examples in the present invention without creative efforts shall fall within the protection scope of the present invention.

[0081] The following examples are used to illustrate the electrolyte and the positive electrode sheet of the present invention.

[0082] Example 1

[0083] (1) Component preparation

[0084] Positive electrode sheet: Composite oxide (NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 Al 0.04 O2) 95 parts by weight; Conductive agent (carbon black) 2.5 parts by weight; Binder (polyvinylidene fluoride) 2.5 parts by weight; Positive electrode current collector: Aluminum foil;

[0085] Electrolyte: 59.95 parts by weight of diethyl carbonate (DEC), 25.95 parts by weight of propylene carbonate (PC), 1 part by weight of NaFSi; 0.6 part by weight of HTL; 12.5 parts by weight of electrolyte (sodium hexafluorophosphate (NaPF6)).

[0086] (2) Preparation of composite oxide

[0087] 1) Mix soluble Ni salt (nickel sulfate), soluble Fe salt (iron sulfate), soluble Mn salt (manganese sulfate), and soluble aluminum salt containing Al element (aluminum nitrate) according to the stoichiometric ratio (where the stoichiometric ratio of Ni / Fe / Mn is 1:1:1, and the stoichiometry of Al is 15% of the stoichiometry of iron), add it to the solvent H2O to obtain a mixed solution; slowly add an appropriate amount of ammonia water to the mixed solution, keep stirring, and adjust the pH value of the mixed solution to 11.5 ± 0.2 to obtain a coprecipitate containing Ni, Fe, Mn, and M; filter to obtain a composite precursor;

[0088] 2) Wash the composite precursor obtained in step 1 with deionized water and dry it. After drying, mix it evenly with sodium carbonate according to the stoichiometric ratio, and carry out high-temperature sintering. Among them, the sintering temperature is 900 °C, the time is 20 h, the sintering atmosphere is N2, and grind the sintered product to obtain NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 Al 0.04 O2, denoted as composite oxide A.

[0089] (3) Preparation of positive electrode sheet

[0090] Disperse composite oxide A, conductive agent, and binder in an appropriate amount of N-methylpyrrolidone, stir well to form a uniform positive electrode paste, coat the positive electrode paste on the positive electrode current collector, and then dry, roll, and cut to obtain a positive electrode sheet. Among them, in the XRD pattern of the positive electrode sheet, there are two diffraction peaks at 16.7 and 41.7. The peak intensity H1 of the diffraction peak at 16.7 is 9458, and the peak intensity H2 of the diffraction peak at 41.7 is 12575, then H1 / H2 = 0.7521.

[0091] (4) Preparation of electrolyte

[0092] In a glove box filled with argon (H2O < 0.1 ppm, O2 < 0.1 ppm), mix PC / DEC evenly, then add a fully dried electrolyte (sodium hexafluorophosphate (NaPF6)) to it, dissolve it, add NaFSi and HTL, stir well, and after passing the water content and free acid detection, obtain the required electrolyte.

[0093] The battery obtained in Example 1: H1 / H2+A = 0.7521+0.2595 = 1.0116≥0.6.

[0094] Example 1-1

[0095] It was carried out with reference to Example 1, except that EC was added to the electrolyte and HTL was not added. See Table 1 for details.

[0096] Example 1-2

[0097] It was carried out with reference to Example 1, except that the weight fraction of HTL in the electrolyte was changed. See Table 1 for details.

[0098] Example 2

[0099] It was carried out with reference to Example 1, except that HTL was not added to the electrolyte and the weight fraction of NaFSi in the electrolyte was changed. See Table 1 for details.

[0100] Example 2-1

[0101] It was carried out with reference to Example 2, except that EC was added to the electrolyte. See Table 1 for details.

[0102] Example 2-2

[0103] It was carried out with reference to Example 2, except that HTL was added to the electrolyte. See Table 1 for details.

[0104] Example 3

[0105] It was carried out with reference to Example 2, except that the weight fractions of PC and NaFSi in the electrolyte were changed. See Table 1 for details.

[0106] Example 3-1

[0107] It was carried out with reference to Example 3, except that EC was added to the electrolyte. See Table 1 for details.

[0108] Example 3-2

[0109] It was carried out with reference to Example 3, except that HTL was added to the electrolyte. See Table 1 for details.

[0110] Example 4

[0111] It was carried out with reference to Example 2, except that the weight fractions of PC and NaFSi in the electrolyte were changed. See Table 1 for details.

[0112] Example 4-1

[0113] It was carried out with reference to Example 4, except that EC was added to the electrolyte. See Table 1 for details.

[0114] Example 4-2

[0115] It was carried out with reference to Example 4, except that HTL was added to the electrolyte. See Table 1 for details.

[0116] Example 4-3

[0117] It was carried out with reference to Example 4-2, except that EC was added to the electrolyte. See Table 1 for details.

[0118] Example 5

[0119] It was carried out with reference to Example 1, except that the specific selection of the composite oxide was changed by adjusting the element ratio and sintering temperature, and at the same time, the content of PC in the electrolyte was adjusted. See Table 1 for details.

[0120] Example 5-1

[0121] It was carried out according to Example 5, except that the specific selection of the composite oxide was changed by adjusting the element ratio and sintering temperature. See Table 1 for details.

[0122] Example 5-2

[0123] It was carried out according to Example 5, except that the specific selection of the composite oxide was changed by adjusting the element ratio and sintering temperature. See Table 1 for details.

[0124] Example 6 group

[0125] Example 6-1

[0126] It was carried out with reference to Example 1-2, except that the content of HTL in the electrolyte was adjusted. See Table 1 for details.

[0127] Example 6-2

[0128] It was carried out according to Example 1-2, except that the content of HTL in the electrolyte was adjusted. See Table 1 for details.

[0129] Example 7 group

[0130] Example 7-1

[0131] It was carried out with reference to Example 1-2, except that the content of PC in the electrolyte was changed and HTL was not added. See Table 1 for details.

[0132] Example 7-2

[0133] It was carried out with reference to Example 1-2, except that the content of PC in the electrolyte was changed. See Table 1 for details.

[0134] Example 7-3

[0135] It was carried out with reference to Examples 1-2, except that the content of PC in the electrolyte was changed and HTL was not added. See Table 1 for details.

[0136] Example 7-4

[0137] It was carried out with reference to Examples 1-2. The difference was that the content of PC in the electrolyte was changed. See Table 1 for details.

[0138] Example 8 group

[0139] Example 8-1

[0140] It was carried out with reference to Examples 1-2. The difference was that the content of PC in the electrolyte was changed and HTL was not added. See Table 1 for details.

[0141] Example 8-2

[0142] It was carried out with reference to Examples 1-2. The difference was that the content of PC in the electrolyte was changed. See Table 1 for details.

[0143] Example 8-3

[0144] It was carried out with reference to Example 2. The difference was that the content of NaFSi in the electrolyte was changed. See Table 1 for details.

[0145] Example 8-4

[0146] It was carried out with reference to Example 8-3. The difference was that HTL was added to the electrolyte. See Table 1 for details.

[0147] Comparative Example 1

[0148] It was carried out with reference to Comparative Example 6. The difference was that the temperature of the high-temperature sintering for preparing the composite oxide was adjusted to 650 °C and the time was adjusted to 12 h. The obtained composite oxide was denoted as composite oxide B. In the XRD pattern of the positive electrode sheet including composite oxide B, two diffraction peaks were located at 16.9° and 42.1° respectively. The ratio of the peak height H1 of the diffraction peak at 16.9° to the peak height H2 of the diffraction peak at 42.1°, i.e., H1 / H2 = 0.3912.

[0149] Comparative Example 2

[0150] It was carried out with reference to Comparative Example 1. The difference was that HTL was added to the electrolyte. See Table 1 for details.

[0151] Table 1

[0152]

[0153]

[0154] * indicates the same as Example 1;

[0155] - means it does not exist.

[0156] Preparation Example

[0157] The electrolytes and positive electrodes obtained in the examples and comparative examples were used to prepare batteries in the following manners.

[0158] (1) Preparation of positive electrode

[0159] The positive electrode sheets obtained in the above-mentioned embodiments and comparative examples were used respectively.

[0160] (2) Negative electrode preparation

[0161] Weigh the negative electrode material (hard carbon), conductive agent (carbon black), binder (styrene-butadiene rubber), and thickener (sodium carboxymethyl cellulose) in a weight ratio of 90:2.5:5.0:2.5, disperse them in an appropriate amount of deionized water, stir them thoroughly to form a uniform negative electrode slurry, coat the negative electrode slurry on the negative electrode current collector copper foil, and then dry, roll and cut to obtain the negative electrode sheet.

[0162] (3) Electrolyte

[0163] The electrolytes obtained in the above-mentioned embodiments and comparative examples were used respectively.

[0164] (4) Preparation of sodium ion batteries

[0165] The positive electrode sheet of step (1), the negative electrode sheet of step (2) and the separator are stacked in order so that the separator is located between the positive electrode sheet and the negative electrode sheet, and then the electrode ears are welded and wound to obtain a winding core, and then the winding core is placed in an aluminum-plastic film packaging bag, and finally the above-mentioned electrolyte is injected and the sodium ion battery is prepared through vacuum sealing, standing, forming, shaping and other processes.

[0166] Test Case

[0167] 1. The positive electrode sheets made of the composite oxides obtained in the examples and comparative examples were subjected to XRD testing.

[0168] The positive electrode sheet prepared from the composite oxide of Example 1 was subjected to XRD testing to obtain the XRD spectrum of the positive electrode sheet of Example 1. Figure 1 As shown, it can be seen that in the XRD spectrum, there are two diffraction peaks at 16-17° and 41-42° respectively, the peak height H1 of the diffraction peak at 16-17° and the peak height H2 of the diffraction peak at 41-42°, wherein H1 / H2=0.7521 satisfies: H1 / H2≥0.5.

[0169] The positive electrode sheet prepared from the composite oxide of Example 9 was subjected to XRD testing to obtain the XRD image of the positive electrode sheet of Comparative Example 1. Figure 2As shown, it can be seen that in the XRD pattern, there are two diffraction peaks at 16 - 17° and 41 - 42° respectively. The peak height H1 of the diffraction peak at 16 - 17° and the peak height H2 of the diffraction peak at 41 - 42°, where H1 / H2 = 0.3912.

[0170] 2. The batteries obtained from the examples and comparative examples were respectively tested as follows.

[0171] (1) Cycling performance test

[0172] The sodium - ion battery was placed at 25°C, charged at a constant current of 0.5C to the upper - limit voltage (4.0V), then charged at a constant voltage of 4.0V to 0.05C, and left standing for 5 minutes; then discharged at a constant current of 0.5C to 1.5V and left standing for 5 minutes. This is one charge - discharge cycle. Charge / discharge in this way, and record the discharge capacity of the first cycle as Q1 and the discharge capacity of the 200th cycle as Q respectively. The cycling capacity retention rate = Q1 / Q * 100%. The specific results are shown in Table 2.

[0173] (2) Storage performance test

[0174] The sodium - ion battery was placed at 25°C, charged at a constant current of 0.5C to the upper - limit voltage (4.0V), then charged at a constant voltage of 4.0V to 0.05C, and left standing for 5 minutes; then discharged at a constant current of 0.5C to 1.5V. Then the battery was fully charged and placed in a 60°C environment for 30 days. Then the battery was cycled for one week at room temperature. Record the discharge capacity before storage as N1 and the discharge capacity after storage as N respectively. The storage capacity retention rate = N1 / N * 100%. The specific results are shown in Table 2.

[0175] The results were recorded in Table 2.

[0176] Table 2

[0177]

[0178]

[0179] It can be seen from Table 2 that through the comparative examples and examples, it can be seen that the cycling capacity retention rate and storage capacity retention rate of the example batteries are significantly improved, indicating that the battery of the present invention, through the synergistic cooperation of the positive electrode sheet and the electrolyte, improves the cycling stability and storage performance of the battery.

[0180] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited thereto. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, including any other suitable combination of each technical feature. These simple modifications and combinations should also be regarded as the content disclosed by the present invention and fall within the protection scope of the present invention.

Claims

1. A battery, characterized in that, The battery includes a positive electrode sheet and an electrolyte. In the XRD pattern of the positive electrode sheet, there are two diffraction peaks at 15° - 20° and 40° - 43°. The peak intensity of the diffraction peak at 15° - 20° is H1, and the peak intensity of the diffraction peak at 40° - 43° is H2, where H1 / H2 ≥ 0.

5. And the electrolyte includes propylene carbonate. Based on the total weight of the electrolyte, the weight content A of propylene carbonate is 15.4wt% - 40.6wt%. Then the battery satisfies: 0.6 ≤ H1 / H2 + A ≤ 1.

4.

2. The battery according to claim 1, wherein, The peak intensity H1 of the diffraction peak at 15° - 20° and the peak intensity H2 of the diffraction peak at 40° - 43° satisfy: H1 / H2 is 0.5 - 0.

9.

3. The battery according to claim 1, wherein The positive electrode sheet includes a positive electrode active material, and the positive electrode active material includes Na x Ni a Fe b Mn c A y O2, where x satisfies 0.7 ≤ x ≤ 1.05, y satisfies 0 ≤ y ≤ 0.5, A includes one or more of Li, Mg, Zn, Co, Ca, Ba, Sr, Al, B, Cr, V, Zr, Ti, Sn, Mo, Ru, Si, Sb, Nb, Zr, and Te, where a satisfies 0.3 ≤ a ≤ 1, b satisfies 0.1 ≤ b ≤ 0.5, and c satisfies 0.1 ≤ c ≤ 0.

5.

4. The battery according to any one of claims 1-3, wherein, The positive electrode sheet includes a positive electrode active material layer, and the positive electrode active material layer includes a composite oxide. Based on the total weight of the positive electrode active material layer, the weight content of the composite oxide is 92wt% - 99wt%.

5. The battery according to claim 4, wherein, Based on the total weight of the positive electrode active material layer, the weight content of the composite oxide is 95wt% - 98wt%.

6. The battery according to claim 1, wherein, The electrolyte includes sodium bis(fluorosulfonyl)imide.

7. The battery according to claim 6, wherein, Based on the total weight of the electrolyte, the weight content of sodium bis(fluorosulfonyl)imide is 0.1wt% - 10wt%.

8. The battery according to claim 1, wherein, The electrolyte further includes 1 - hexylpyridinium tetrafluoroborate.

9. The battery according to claim 8, wherein, Based on the total weight of the electrolyte, the weight content of 1 - hexylpyridinium tetrafluoroborate is 0.1wt% - 3wt%.

10. The battery according to claim 9, wherein, Based on the total weight of the electrolyte, the weight content of 1 - hexylpyridinium tetrafluoroborate is 0.5wt% - 0.8wt%.

Images