battery

Abstract

A battery, comprising a positive electrode sheet and an electrolyte, wherein in an XRD pattern of the electrode sheet, there are two diffraction peaks from 15° to 20° and from 40° to 43°, the peak intensity of the diffraction peak present from 15° to 20° is H1, and the peak intensity of the diffraction peak present from 40° to 43° is H2; the electrolyte comprises propylene carbonate, and with the total weight of the electrolyte as a reference, the weight content of the propylene carbonate is A; and the battery satisfies: H1 / H2+A≥0.6. The battery can reduce an interfacial reaction and improve the cycle stability and storage performance of the battery.

Description

Battery Technical Field

[0001] The present disclosure relates to the technical field of batteries, and in particular to a battery.

[0002] Background of the Invention

[0003] Sodium-ion batteries have broad application prospects due to their combined advantages of low cost, abundant resources, and environmental friendliness. Their operating principle is similar to that of lithium-ion batteries, primarily utilizing the intercalation and deintercalation of sodium ions between the positive and negative electrodes to store and release energy. However, the electrolyte in sodium-ion batteries reacts on the surface of the positive electrode. This is because conventional electrolytes are unable to form a good CEI film on the positive electrode, resulting in unstable cycling performance and poor storage performance.

[0004] Summary of the Invention

[0005] The present invention aims to overcome the above-mentioned problems existing in the prior art and provide a battery. The battery disclosed in the present invention can reduce interfacial reactions and improve the cycle stability and storage performance of the battery.

[0006] The present disclosure provides a battery, comprising a positive electrode sheet and an electrolyte. The XRD spectrum of the positive electrode sheet contains 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. The electrolyte comprises propylene carbonate, and the weight content of the propylene carbonate is A based on the total weight of the electrolyte. The battery satisfies the following condition: H1 / H2+A≥0.6.

[0007] Through the above technical solution, the present disclosure has at least the following advantages compared with the prior art:

[0008] The battery disclosed herein cooperates with the positive electrode sheet and the electrolyte, so that the electrolyte can form a CEI film on the surface of the positive electrode sheet, thereby reducing interfacial reactions and further improving the cycle stability and storage performance of the battery.

[0009] The endpoints of the ranges and any values ​​disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] FIG1 shows an XRD pattern of a positive electrode sheet provided in one embodiment of the present disclosure.

[0011] FIG2 shows an XRD pattern of a positive electrode sheet provided in a pair of ratios of the present disclosure. DETAILED DESCRIPTION

[0012] The following describes the specific embodiments of the present disclosure in detail. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present disclosure and are not intended to limit the present disclosure.

[0013] It should be noted that the numerical expressions such as "first" and "second" in this disclosure are only used to distinguish different substances or usage methods, and do not represent a difference in order.

[0014] The present disclosure provides a battery, comprising a positive electrode sheet and an electrolyte. In an XRD pattern of the positive electrode sheet, two diffraction peaks are present 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. The electrolyte comprises propylene carbonate, and the weight content of the propylene carbonate is A based on the total weight of the electrolyte. The battery satisfies the following condition: H1 / H2+A≥0.6.

[0015] The XRD spectrum of the positive electrode sheet shows two diffraction peaks at 15°~20° and 40°~43°, respectively. 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 spectrum of the positive electrode sheet indicates that the structural stability of the positive electrode sheet is relatively high, which can reduce the battery deactivation, expansion, rupture, and side reactions between the positive electrode sheet and the electrolyte (such as gas production, etc.) caused by temperature changes during charging and discharging, thereby improving the cycle stability of the battery.

[0016] 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 disclosure have discovered that when the positive electrode sheet and the electrolyte meet the above conditions, through the synergistic cooperation of the positive electrode sheet and the electrolyte, that is, the positive electrode of the present disclosure can promote the propylene carbonate (PC) in the electrolyte to form a good passivation film on the positive electrode surface, thereby reducing the particle breakage and crystal orientation transformation of the positive electrode material during the charge and discharge process, and at the same time can reduce interfacial reactions, thereby improving the cycle stability and storage performance of the battery.

[0017] In the present disclosure, the synergistic combination of the positive electrode and the electrolyte has enabled the battery to achieve better cycle stability and storage performance than the prior art. To further improve the effect, one or more of the technical features may be further optimized.

[0018] In one example, the battery satisfies: 0.6≤H1 / H2+A≤1.4.

[0019] In one embodiment, as shown in FIG1 , the XRD pattern of the positive electrode sheet exhibits two diffraction peaks at 15° to 20° and 40° to 43°, respectively. The peak intensity H1 of the diffraction peak at 15° to 20° and the peak intensity H2 of the diffraction peak at 40° to 43° satisfy the relationship 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 exhibits good structural stability, which can promote the electrolyte to form a good CEI film on the surface of the positive electrode sheet, reduce interfacial reactions, and thus improve the cycle stability and storage performance of the battery.

[0020] In one embodiment, H1 / H2 is 0.5 to 0.9 (e.g., 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 deintercalation, while also improving the structural stability of the CEI membrane, reducing the interfacial reaction between the positive electrode sheet and the electrolyte, and improving the long-term cycle performance and storage performance of the battery.

[0021] In one example, the electrolyte may include propylene carbonate (PC), and the weight content of the propylene carbonate is 10wt% to 50wt% (for example, 10wt%, 15wt%, 20wt%, 25wt%, 30wt%, 35wt%, 40wt%, 45wt%, 50wt%) based on the total weight of the electrolyte. 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 controlled within the above range, PC can form a good passivation film on the surface of the positive electrode material of the present invention, fully protecting the electrolyte from being decomposed in large quantities by the positive electrode. If the content is too low, the passivation film will be unevenly formed, but if the content is too high, the passivation film will be too thick and the impedance will be too large, thereby causing battery performance deviation.

[0022] In one embodiment, the weight content of the propylene carbonate is 15.4 wt% to 40.6 wt% based on the total weight of the electrolyte. By further controlling the range of the propylene carbonate content, the synergistic effect of the propylene carbonate and the positive electrode sheet can be further enhanced, thereby promoting higher stability of the CEI film formed on the surface of the positive electrode sheet, thereby further improving the long-term cycle performance and storage performance of the battery.

[0023] In one embodiment, the weight content of the propylene carbonate is 20 wt% to 35 wt% based on the total weight of the electrolyte. By further controlling the range of the propylene carbonate content, the synergistic effect between the propylene carbonate and the positive electrode sheet can be further enhanced, thereby promoting a higher stability of the CEI film formed on the surface of the positive electrode sheet, thereby further improving the long-term cycle performance and storage performance of the battery.

[0024] According to a specific embodiment, the positive electrode sheet includes a composite oxide, 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 (e.g., 0.7, 0.75, 0.8, 0.85, 0.9, 0.951, 1, 1.05), y satisfies 0≤y≤0.5 (e.g., 0, 0.05, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5), and a satisfies 0.3≤a≤1 (e.g., 0.3, 0.4, 0.5, 0.6, 0.7 , 0.8, 0.9, 1), b satisfies 0.1≤b≤0.5 (e.g., 0.1, 0.2, 0.3, 0.4, 0.5), c satisfies 0.1≤c≤0.5 (e.g., 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 disclosure, the positive electrode sheet including the composite oxide may satisfy H1 / H2≥0.5.

[0025] In the chemical formula of the composite oxide Na x Ni a Fe b Mn c A y In O2, the elements conform to the principle that the algebraic sum of the positive and negative valences of each element in the compound is zero.

[0026] In one example, x satisfies 0.9≤x≤1.03.

[0027] In one example, y satisfies 0.01≤y≤0.1.

[0028] In one embodiment, 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. Chemical formula: Na x Nia Fe b Mn c The relationship between the elements in O2 conforms to the principle that the algebraic sum of the positive and negative valences of the elements in the compound is zero.

[0029] In one embodiment, the composite oxide includes a doping element A. The composite oxide including the doping element A has higher positive electrode activity stability, prevents the dissolution of transition metal elements during charging and discharging, improves corrosion in the electrolyte, improves the stability of the positive electrode material, and makes the CEI film formed on the surface of the positive electrode sheet more stable and reduces interfacial reactions, thereby improving the long cycle performance and storage performance of the battery.

[0030] In one embodiment, 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 1 / 3 Fe 1 / 3 Mn 1 / 3 Al 0.04 O2、NaNi 0.5 Fe 0.2 Mn 0.3 Al 0.01 O2、NaNi 0.5 Fe 0.2 Mn 0.3 O2 and NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 One or more of O2.

[0031] In one example, the positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer, wherein the positive electrode active material layer is located on one or both sides of the positive electrode current collector, and the positive electrode active material layer includes a positive electrode material, and the positive electrode material includes a composite oxide.

[0032] In one example, the positive electrode current collector includes aluminum foil or porous aluminum foil.

[0033] In one example, the positive electrode active material layer includes a composite oxide.

[0034] 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 92wt% to 99wt% (for example, 92wt%, 93wt%, 94wt%, 95wt%, 96wt%, 97wt%, 98wt%, 99wt%).

[0035] In one embodiment, 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 %.

[0036] The composite oxide can be prepared by the following method:

[0037] (1) mixing a soluble Ni salt, a soluble Fe salt, a soluble Mn salt, and a soluble salt containing an Al element, and adding the mixture to a solvent to obtain a mixed solution; adjusting the pH of the mixed solution to obtain a coprecipitate containing Ni, Fe, Mn, and Al, and performing solid-liquid separation (e.g., filtration) to obtain a composite precursor;

[0038] (2) drying the composite precursor, mixing it with sodium carbonate, and sintering it at high temperature.

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

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

[0041] In one example, the soluble Mn salt includes one or more of manganese sulfate and manganese nitrate.

[0042] In one embodiment, the soluble salt containing Al element includes one or more of aluminum nitrate.

[0043] In one example, the molar ratio of the soluble Ni salt, the soluble Fe salt, and the soluble Mn salt is a:b:c.

[0044] In one example, the solvent includes one or more of water, ethanol, acetone, toluene, and ether.

[0045] In one example, the pH of the mixed solution is adjusted to 3-12 (eg, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12).

[0046] In one embodiment, the drying conditions are: temperature of 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 time of 1h to 20h (for example, 1h, 3h, 5h, 8h, 10h, 13h, 15h, 18h, 20h).

[0047] In one example, the molar ratio of the sodium carbonate to the soluble Ni salt is x:a.

[0048] In one embodiment, the high-temperature sintering conditions are: a temperature of 770°C to 1000°C (for example, 770°C, 750°C, 800°C, 850°C, 900°C, 950°C, 1000°C), a sintering time of 10h to 40h (for example, 10h, 15h, 20h, 25h, 30h, 35h, 40h), and a sintering atmosphere of air atmosphere, compressed air atmosphere, N2 gas atmosphere, or oxygen atmosphere.

[0049] In one embodiment, the high temperature sintering conditions are: a temperature of 800° C. to 900° C., a sintering time of 20 h to 38 h, and a sintering atmosphere of N 2 gas.

[0050] According to a specific embodiment, the positive electrode active material layer further includes a positive electrode conductor and a positive electrode binder.

[0051] In one example, the positive electrode conductive agent includes one or more of conductive carbon black, acetylene black, Ketjen black, conductive graphite, conductive carbon fiber, carbon nanotubes, metal powder, and carbon fiber.

[0052] In one example, the positive electrode binder includes one or more of polyvinylidene fluoride, styrene butadiene rubber, styrene butadiene latex, polytetrafluoroethylene, and polyethylene oxide.

[0053] According to a specific embodiment, based on the total weight of the positive electrode active material layer, the weight content of the positive electrode conductor is 0.01wt% to 7wt% (for example, 0.01wt%, 0.05wt%, 0.1wt%, 0.5wt%, 1wt%, 3wt%, 5wt%, 7wt%), and the weight content of the positive electrode binder is 0.1wt% to 8wt% (for example, 0.1wt%, 0.5wt%, 1wt%, 3wt%, 5wt%, 8wt%).

[0054] In one example, based on the total weight of the positive electrode active material layer, the weight content of the positive electrode conductor is 0.1 wt% to 2.5 wt%, and the weight content of the positive electrode binder is 0.1 wt% to 5 wt%.

[0055] In one example, based on the total weight of the positive electrode active material layer, the weight content of the positive electrode conductor is 0.1 wt % to 2 wt %, and the weight content of the positive electrode binder is 0.1 wt % to 5 wt %.

[0056] In one embodiment, the electrolyte includes sodium bis(fluorosulfonyl)imide (NaFSi). The inventors of the present disclosure have discovered 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, reducing interfacial reactions. At the same time, PC in the electrolyte can also promote the dissociation of NaFSi, improving the film formation efficiency, thereby further improving the cycle stability and storage performance of the battery.

[0057] According to a specific embodiment, based on the total weight of the electrolyte, the weight content of the NaFSi is 0.1wt% to 10wt% (for example, 0.1wt%, 0.5wt%, 1wt%, 1.5wt%, 2wt%, 2.5wt%, 3wt%, 3.5wt%, 4wt%, 4.5wt%, 5wt%, 5.5wt%, 6wt%, 7wt%, 8wt%, 9wt%, 10wt%).

[0058] In one embodiment, based on the total weight of the electrolyte, the weight content of the NaFSi is 0.2 wt % to 6 wt %.

[0059] In one example, the electrolyte further includes ethylene carbonate (EC).

[0060] According to a specific embodiment, the weight content of ethylene carbonate is less than 5wt% based on the total weight of the electrolyte. While ethylene carbonate can promote the dissociation of NaFSi, its involvement in the dissociation process can cause reactions on the surface of the positive electrode sheet, affecting the components of the CEI membrane and thus deteriorating battery performance. By controlling the ethylene carbonate content in the electrolyte within the aforementioned range, the impact of ethylene carbonate on the CEI membrane components can be reduced, thereby minimizing its impact on battery performance.

[0061] In a preferred embodiment, the electrolyte does not include ethylene carbonate. When the electrolyte does not include ethylene carbonate, decomposition and volatilization of ethylene carbonate during the charge and discharge process of the battery can be avoided, reducing battery gas production, thereby improving the battery's cycle performance and storage performance.

[0062] In one embodiment, the electrolyte further comprises 1-hexylpyridinium tetrafluoroborate (HTL), wherein the 1-hexylpyridinium tetrafluoroborate has a structure as shown in formula (I):

[0063] 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, allowing current to be conducted in the sodium ion battery, which can improve the stability of the electrolyte and form a dense protective film on the surface of the sodium ion positive electrode.

[0064] According to a specific embodiment, based on the total weight of the electrolyte, the weight content of the 1-hexylpyridinium tetrafluoroborate is 0.1wt% to 3wt% (for example, 0.1wt%, 0.5wt%, 1wt%, 1.5wt%, 2wt%, 2.5wt%, 3wt%).

[0065] In one embodiment, based on the total weight of the electrolyte, the weight content of the 1-hexylpyridinium tetrafluoroborate is 0.5 wt % to 0.8 wt %.

[0066] When the positive electrode sheet meets the H1 / H2≥0.5, the HTL additive in the electrolyte can form a dense protective film on the positive electrode surface, significantly improving the cycle stability and storage performance of the sodium ion battery.

[0067] In one example, the electrolyte includes an electrolyte, an organic solvent, and an additive.

[0068] In one example, the electrolyte includes one or more of sodium hexafluorophosphate (NaPF6) and sodium bis(fluorosulfonimide) (NaFSi).

[0069] In one example, the additive includes one or more of vinylene carbonate (VC), vinyl sulfate, and 1,3-propane sultone.

[0070] In one example, the organic solvent includes one or more of diethyl carbonate (DEC), ethyl methyl carbonate, propylene carbonate, and ethylene carbonate.

[0071] In one embodiment, based on the total weight of the electrolyte, the weight content of the additive is 0 wt% to 15 wt%. When the weight content of the additive in the electrolyte is 0 wt%, it means that the electrolyte does not contain the additive.

[0072] According to a specific embodiment, based on the total weight of the electrolyte, the weight content of the electrolyte is 6wt% to 20wt% (for example, 6wt%, 8wt%, 10wt%, 12wt%, 15wt%, 18wt%, 20wt%), and the weight content of the additive is 1wt% to 15wt% (for example, 1wt%, 3wt%, 5wt%, 7wt%, 10wt%, 12wt%, 15wt%).

[0073] 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%.

[0074] The content of the organic solvent including one or more of diethyl carbonate (DEC), ethyl methyl carbonate, propylene carbonate, and ethylene carbonate can be adjusted within a wide range. For example, when the weight content of each of the above components in the electrolyte is less than 100%, the portion less than 100% can be supplemented with the organic solvent including one or more of diethyl carbonate (DEC), ethyl methyl carbonate, propylene carbonate, and ethylene carbonate.

[0075] In one example, the battery includes a negative electrode sheet and a separator.

[0076] 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, and the negative electrode active material layer includes a negative electrode material, a negative electrode conductive agent, a negative electrode binder, and a thickening agent.

[0077] In one example, the negative electrode current collector includes a copper foil or a porous copper foil.

[0078] 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.

[0079] In one example, the negative electrode 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.

[0080] In one example, the negative electrode binder includes one or more of polyvinylidene fluoride, styrene-butadiene rubber, polytetrafluoroethylene, and polyethylene oxide.

[0081] In one example, the thickening agent includes sodium carboxymethyl cellulose.

[0082] 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 92wt% to 99wt% (for example, 92wt%, 93wt%, 94wt%, 95wt%, 96wt%, 97wt%, 98wt%, 99wt%), the weight content of the conductive agent is 0.1wt% to 7wt% (for example, 0.1wt%, 0.5wt%, 1wt%, 3wt%, 5wt%, 7wt%), the weight content of the binder is 0.1wt% to 7wt% (for example, 0.1wt%, 0.5wt%, 1wt%, 3wt%, 5wt%, 7wt%), and the weight content of the thickener is 0.1wt% to 7wt% (for example, 0.1wt%, 0.5wt%, 1wt%, 3wt%, 5wt%, 7wt%).

[0083] In one example, based on the total weight of the negative electrode active material layer, the weight content of the negative electrode material is 94wt% to 98wt%, the weight content of the conductive agent is 0.5wt% to 2wt%, the weight content of the binder is 0.5wt% to 2wt%, and the weight content of the thickener is 0.5wt% to 2wt%.

[0084] According to a specific embodiment, the battery is a sodium ion battery.

[0085] 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.

[0086] The present disclosure will be described in detail below through examples. The examples described in this disclosure are only a portion of the examples of the present disclosure, not all of the examples. Based on the examples in this disclosure, all other examples obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this disclosure.

[0087] The following examples are used to illustrate the electrolyte and positive electrode sheet of the present disclosure.

[0088] Example 1

[0089] (1) Preparation of ingredients

[0090] Positive electrode: composite oxide (NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 Al 0.04 O2) 95 parts by weight; positive electrode conductive agent (carbon black) 2.5 parts by weight; positive electrode binder (polyvinylidene fluoride) 2.5 parts by weight; positive electrode current collector: aluminum foil;

[0091] 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 parts by weight of HTL; and 12.5 parts by weight of electrolyte (sodium hexafluorophosphate (NaPF6)).

[0092] (2) Preparation of composite oxides

[0093] 1) mixing a soluble Ni salt (nickel sulfate), a soluble Fe salt (ferric sulfate), a soluble Mn salt (manganese sulfate), and a soluble salt containing an Al element, aluminum nitrate, in a stoichiometric ratio (wherein the stoichiometric ratio of Ni / Fe / Mn is 1:1:1, and the stoichiometric amount of Al is 15% of the stoichiometric amount of iron), and adding the mixture to a solvent, H2O, to obtain a mixed solution; slowly adding an appropriate amount of ammonia water to the mixed solution while stirring, and adjusting the pH of the mixed solution to 11.5±0.2 to obtain a coprecipitate containing Ni, Fe, Mn, and M; and filtering to obtain a composite precursor;

[0094] 2) The composite precursor is washed with deionized water and dried, and then mixed with sodium carbonate according to a stoichiometric ratio and sintered at a high temperature, wherein the sintering temperature is 900°C, the time is 20 hours, the sintering atmosphere is N2, and the sintered product is ground to obtain NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 Al 0.04 O2, recorded as composite oxide A.

[0095] (3) Preparation of positive electrode sheet

[0096] The composite oxide A, conductive agent and binder are dispersed in an appropriate amount of N-methylpyrrolidone and fully stirred to form a uniform positive electrode slurry. The positive electrode slurry is coated on the positive electrode current collector, and then dried, rolled and cut to obtain a positive electrode sheet. In the XRD spectrum 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, so H1 / H2=0.7521.

[0097] (4) Preparation of electrolyte

[0098] In a glove box filled with argon (H2O < 0.1ppm, O2 < 0.1ppm), PC / DEC was mixed evenly, and then fully dried electrolyte (sodium hexafluorophosphate (NaPF6)) was added thereto. After dissolution, NaFSi and HTL were added and stirred evenly. After passing the moisture and free acid tests, the required electrolyte was obtained.

[0099] For the battery obtained in Example 1, H1 / H2+A=0.7521+0.2595=1.0116≥0.6.

[0100] Example 1-1

[0101] The same process was carried out as in Example 1, except that EC was added to the electrolyte and HTL was not added. For details, see Table 1.

[0102] Example 1-2

[0103] The same process was carried out as in Example 1, except that the weight of HTL in the electrolyte was changed. For details, see Table 1.

[0104] Example 2

[0105] The same method was used as in Example 1, except that HTL was not added to the electrolyte and the weight of NaFSi in the electrolyte was changed. See Table 1 for details.

[0106] Example 2-1

[0107] The process was carried out in accordance with Example 2, except that EC was added to the electrolyte. For details, see Table 1.

[0108] Example 2-2

[0109] The process was carried out in accordance with Example 2, except that HTL was added to the electrolyte. For details, see Table 1.

[0110] Example 3

[0111] The same process was carried out as in Example 2, except that the weight proportions of PC and NaFSi in the electrolyte were changed. For details, see Table 1.

[0112] Example 3-1

[0113] The process was carried out in accordance with Example 3, except that EC was added to the electrolyte. For details, see Table 1.

[0114] Example 3-2

[0115] The process was carried out in accordance with Example 3, except that HTL was added to the electrolyte. For details, see Table 1.

[0116] Example 4

[0117] The same process was carried out as in Example 2, except that the weight proportions of PC and NaFSi in the electrolyte were changed. For details, see Table 1.

[0118] Example 4-1

[0119] The process was carried out in accordance with Example 4, except that EC was added to the electrolyte. For details, see Table 1.

[0120] Example 4-2

[0121] The process was carried out in accordance with Example 4, except that HTL was added to the electrolyte. For details, see Table 1.

[0122] Example 4-3

[0123] The process was carried out in accordance with Example 4-2, except that EC was added to the electrolyte. For details, see Table 1.

[0124] Example 5

[0125] The same method as in Example 1 was used, except that the specific selection of the composite oxide was changed by adjusting the element ratio and the sintering temperature, and the content of PC in the electrolyte was adjusted. See Table 1 for details.

[0126] Example 5-1

[0127] The process was carried out in accordance with Example 5, except that the specific selection of the composite oxide was changed by adjusting the element ratio and the sintering temperature. See Table 1 for details.

[0128] Example 5-2

[0129] The process was carried out in accordance with Example 5, except that the specific selection of the composite oxide was changed by adjusting the element ratio and the sintering temperature. See Table 1 for details.

[0130] Example 6

[0131] Example 6-1

[0132] The process was carried out in accordance with Example 1-2, except that the content of HTL in the electrolyte was adjusted. For details, see Table 1.

[0133] Example 6-2

[0134] The process was carried out in accordance with Example 1-2, except that the content of HTL in the electrolyte was adjusted. For details, see Table 1.

[0135] Example 7 Group

[0136] Example 7-1

[0137] The same process was carried out as in Example 1-2, except that the content of PC in the electrolyte was changed and HTL was not added. For details, see Table 1.

[0138] Example 7-2

[0139] Refer to Example 1-2, except that the PC content in the electrolyte is changed. See Table 1 for details.

[0140] Example 7-3

[0141] The same process was carried out as in Example 1-2, except that the content of PC in the electrolyte was changed and HTL was not added. For details, see Table 1.

[0142] Example 7-4

[0143] Refer to Example 1-2, except that the content of PC in the electrolyte is changed. See Table 1 for details.

[0144] Example 8 Group

[0145] Example 8-1

[0146] The same process was carried out as in Example 1-2, except that the content of PC in the electrolyte was changed and HTL was not added. For details, see Table 1.

[0147] Example 8-2

[0148] The same process was carried out as in Example 1-2, except that the content of PC in the electrolyte was changed. For details, see Table 1.

[0149] Example 8-3

[0150] The same procedure was carried out as in Example 2, except that the content of NaFSi in the electrolyte was changed. For details, see Table 1.

[0151] Example 8-4

[0152] The process is carried out in accordance with Example 8-3, except that HTL is added to the electrolyte. For details, see Table 1.

[0153] Comparative Example 1

[0154] The process was carried out in accordance with Example 6, except that the high-temperature sintering temperature for preparing the composite oxide was adjusted to 650°C and the time was adjusted to 12 h. The composite oxide obtained was recorded as composite oxide B, wherein the two diffraction peaks in the XRD spectrum of the positive electrode sheet of composite oxide B were located at 16.9° and 42.1°, respectively, and 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° was H1 / H2=0.3912.

[0155] Comparative Example 2

[0156] The process was carried out in accordance with Comparative Example 1, except that HTL was added to the electrolyte. For details, see Table 1.

[0157] Table 1 * indicates the same as Example 1; - indicates absence.

[0158] Preparation Example

[0159] Batteries were prepared using the electrolytes and positive electrodes obtained in the examples and comparative examples in the following manners.

[0160] (1) Preparation of positive electrode sheet

[0161] The positive electrode sheets obtained in the above embodiments and comparative examples were used respectively.

[0162] (2) Preparation of negative electrode sheet

[0163] The negative electrode material (hard carbon), negative electrode conductive agent (carbon black), negative electrode binder (styrene-butadiene rubber), and thickener (sodium carboxymethyl cellulose) were weighed in a weight ratio of 90:2.5:5.0:2.5, dispersed in an appropriate amount of deionized water, and fully stirred to form a uniform negative electrode slurry. The negative electrode slurry was coated on the negative electrode current collector copper foil, and then dried, roll-pressed, and cut to obtain a negative electrode sheet.

[0164] (3) Electrolyte

[0165] The electrolytes obtained in the above-mentioned embodiments and comparative examples were used respectively.

[0166] (4) Preparation of sodium ion batteries

[0167] 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 tabs are welded and wound to obtain a roll core, which is then placed in an aluminum-plastic film packaging bag. Finally, the above-mentioned electrolyte is injected and the battery is vacuum sealed, allowed to stand, formed, and shaped to prepare a sodium ion battery.

[0168] Test Case

[0169] 1. The positive electrode sheets made of the composite oxides obtained in the examples and comparative examples were subjected to XRD testing.

[0170] An XRD test was performed on the positive electrode sheet prepared from the composite oxide of Example 1 to obtain the XRD spectrum of the positive electrode sheet of Example 1, as shown in Figure 1. 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.

[0171] The positive electrode sheet prepared from the composite oxide of Example 9 was subjected to XRD testing to obtain an XRD pattern of the positive electrode sheet of Comparative Example 1, as shown in FIG2 . 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° are as follows: wherein H1 / H2=0.3912.

[0172] 2. The batteries obtained in the examples and comparative examples were subjected to the following tests respectively.

[0173] (1) Cyclic performance test

[0174] The sodium-ion battery was placed at 25°C and charged at a constant current of 0.5C to the upper voltage limit (4.0V). It was then charged at a constant voltage of 4.0V to 0.05C and allowed to rest for 5 minutes. The battery was then discharged at a constant current of 0.5C to 1.5V and allowed to rest for 5 minutes. This constituted a charge-discharge cycle. The discharge capacity at the first cycle was recorded as Q1, and the discharge capacity at the 200th cycle was recorded as Q. The cycle capacity retention ratio was calculated as Q1 / Q*100%. See Table 2 for detailed results.

[0175] (2) Storage performance test

[0176] The sodium-ion battery was placed at 25°C and charged at a constant current of 0.5C to the upper voltage limit (4.0V). It was then charged at a constant voltage of 4.0V to 0.05C and allowed to rest for 5 minutes. It was then discharged at a constant current of 0.5C to 1.5V. The battery was then fully charged and stored at 60°C for 30 days. The battery was then subjected to one charge and discharge cycle at room temperature. The discharge capacity before storage was recorded as N1 and the discharge capacity after storage was recorded as N. The storage capacity retention rate = N1 / N*100%. See Table 2 for specific results.

[0177] The results are recorded in Table 2.

[0178] Table 2

[0179] As can be seen from Table 2, it can be seen from the comparative examples and the examples that the cycle capacity retention rate of the example battery is significantly improved, and the storage capacity retention rate is significantly improved, indicating that the battery disclosed in the present invention improves the cycle stability and storage performance of the battery through the coordinated cooperation of the positive electrode sheet and the electrolyte.

[0180] The preferred embodiments of the present disclosure are described in detail above, but the present disclosure is not limited thereto. Within the technical concept of the present disclosure, various simple variations of the technical solution of the present disclosure may be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be regarded as disclosed by the present disclosure and fall within the scope of protection of the present disclosure.

Claims

1. A battery, characterized in that: The battery includes a positive electrode sheet and an electrolyte. The XRD spectrum of the positive electrode sheet contains 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. The electrolyte includes propylene carbonate, and the weight content of the propylene carbonate is A based on the total weight of the electrolyte. Then the battery satisfies: H1 / H2+A≥0.

6.

2. The battery according to claim 1, wherein The battery satisfies: 0.6≤H1 / H2+A≤1.

4.

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

9.

4. The battery according to any one of claims 1 to 3, wherein Based on the total weight of the electrolyte, the weight content A of the propylene carbonate is 10wt% to 50wt%.

5. The battery according to any one of claims 1 to 4, wherein The positive electrode sheet includes a positive electrode active material, the positive electrode active material includes a composite oxide, and the chemical formula of the composite oxide is Na x Ni a Fe b Mn c A y O2, wherein x satisfies 0.7≤x≤1.05, y satisfies 0≤y≤0.5, and the doping element 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.

6. The battery according to claim 5, wherein 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 1 / 3 Fe 1 / 3 Mn 1 / 3 Al 0.04 O2、NaNi 0.5 Fe 0.2 Mn 0.3 Al 0.01 O2、NaNi 0.5 Fe 0.2 Mn 0.3 O2 and NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 One or more of O2.

7. The battery according to claim 5 or 6, 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% to 99wt%, preferably 95wt% to 98wt%.

8. The battery according to claim 7, wherein The positive electrode active material layer further comprises a positive electrode conductor and a positive electrode binder. Based on the total weight of the positive electrode active material layer, the weight content of the positive electrode conductor is 0.01wt% to 7wt%, and the weight content of the positive electrode binder is 0.1wt% to 8wt%; Preferably, based on the total weight of the positive electrode active material layer, the weight content of the positive electrode conductor is 0.1 wt% to 2 wt%, and the weight content of the positive electrode binder is 0.1 wt% to 5 wt%.

9. The battery according to any one of claims 1 to 8, wherein Based on the total weight of the electrolyte, the weight content of the propylene carbonate is 15.4wt% to 40.6wt%, preferably 20wt% to 35wt%.

10. The battery according to any one of claims 1 to 9, wherein The electrolyte includes NaFSi, and based on the total weight of the electrolyte, the weight content of the NaFSi is 0.1wt% to 10wt%, preferably 0.2wt% to 6wt%.

11. The battery according to any one of claims 1 to 10, wherein The electrolyte also includes 1-hexylpyridinium tetrafluoroborate; Preferably, based on the total weight of the electrolyte, the weight content of the 1-hexylpyridinium tetrafluoroborate is 0.1 wt% to 3 wt%, preferably 0.5 wt% to 0.8 wt%.

12. The battery according to any one of claims 1 to 11, wherein The electrolyte further comprises ethylene carbonate, and the weight content of the ethylene carbonate is less than 5wt% based on the total weight of the electrolyte.

13. The battery according to any one of claims 1 to 11, wherein The electrolyte does not include ethylene carbonate.

14. The electrolyte according to any one of claims 1 to 13 further comprises 1-hexylpyridinium tetrafluoroborate, wherein the 1-hexylpyridinium tetrafluoroborate has a structure as shown in formula (I):

15. The electrolyte according to claim 14, wherein Based on the total weight of the electrolyte, the weight content of the 1-hexylpyridinium tetrafluoroborate is 0.1wt% to 3wt%, preferably 0.5wt% to 0.8wt%. 。

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