Calcium ion battery and applications

Abstract

The application relates to the technical field of secondary batteries, in particular to a calcium ion battery and application. The calcium ion battery of the application comprises a positive electrode, a negative electrode, a diaphragm between the positive electrode and the negative electrode and a calcium salt electrolyte, the positive electrode comprises a sodium vanadate positive electrode active material, the sodium vanadate positive electrode active material is sodium ion pre-embedded crystal water-containing vanadate; and / or the calcium salt electrolyte is a calcium salt organic water hybrid electrolyte. The application further provides energy storage equipment and electric equipment, both of which contain the calcium ion battery and have high energy density and high power density. The calcium ion battery of the application uses crystal water-containing layered sodium vanadate with a large interlayer spacing as a positive electrode active material, greatly improves the capacity performance and energy density, and uses a calcium salt organic water hybrid electrolyte, greatly improves the ionic conductivity of the electrolyte, and brings better rate performance.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of secondary batteries, in particular to a calcium ion battery and application. BACKGROUND

[0002] In view of the current situation that raw materials for lithium ion batteries are scarce and the cost is rising sharply, calcium ion batteries as a potential alternative technology to lithium ion batteries have gradually attracted widespread attention in recent years, especially in large-scale energy storage applications, and it is urgent to develop low-cost battery technology. Calcium ion batteries mainly rely on the migration and deintercalation of divalent calcium ions in electrode materials to realize charge storage and release. In the research process, it is particularly important to develop positive electrode materials with excellent calcium ion storage performance and matching electrolytes.

[0003] The prior art discloses a calcium ion battery which is assembled by using CaV6O 16 2.8H2O (calcium vanadate) as a positive electrode material, Ca(TFSI)2 / G2 (calcium bis-trifluoromethanesulfonimide / diethylene glycol dimethyl ether) as an electrolyte, and active carbon cloth as a negative electrode. -1 The discharge capacity under a current density of 50 mA g -1 -1 is 175 mAh g -1 -1, and the capacity retention rate is 75% after 100 cycles under a current density of 50 mA g -1 -1. The discharge capacity under a current density of 1 A g -1 -1 is 41.2 mAh g -1 -1. Divalent calcium ions are the main body of deintercalation in electrode materials of calcium ion batteries. Due to the large ion radius and charge density, strong charging effects are caused, which leads to slow ion deintercalation kinetics, thereby resulting in poor rate performance and capacity performance. The existing calcium ion batteries generally have the problems of low capacity (the maximum specific capacity is less than 200 mAh g -1 -1) and poor rate performance (the tolerable current density is less than 2 A g

[0004] Therefore, it is urgent to research a new calcium ion battery, develop new positive electrode materials and electrolytes for matching, so as to solve the problems of poor rate performance and low capacity of the calcium ion battery, and realize a calcium ion battery with high energy density and high power density. SUMMARY

[0005] In order to overcome the above technical problems, the application provides a calcium ion battery and application, which aims to solve the problems of poor rate performance and low capacity of the existing calcium ion battery, realize a calcium ion battery with high energy density and high power density, and improve the performance of the calcium ion battery.

[0006] The application provides a calcium ion battery, comprising a positive electrode, a negative electrode, a separator and a calcium salt electrolyte between the positive electrode and the negative electrode, the positive electrode comprises a sodium vanadate positive electrode active material, the sodium vanadate positive electrode active material is a sodium ion pre-embedded crystalline water-containing vanadate; and / or the calcium salt electrolyte is a calcium salt organic water hybrid electrolyte.

[0007] Preferably, the chemical formula of the sodium vanadate positive electrode active material is Na x V y O z ·nH2O, wherein 0

[0008] Preferably, the chemical formula of the sodium vanadate positive electrode active material is Na2V6O 16 ·2H2O, or Na 1.2 V3O8·2.8H2O.

[0009] Preferably, the preparation method of the sodium vanadate positive electrode active material is:

[0010] Vanadium pentoxide and sodium hydroxide are weighed according to a stoichiometric ratio, mixed and dissolved in deionized water;

[0011] The mixed solution is stirred, then transferred to a polytetrafluoroethylene reactor for hydrothermal reaction;

[0012] Cooling, washing with deionized water and ethanol, suction filtration and drying obtain the calcium ion battery sodium vanadate positive electrode active material.

[0013] Preferably, the molar ratio of vanadium pentoxide and sodium hydroxide is 1:1; the stirring time is 30 min; the temperature of the hydrothermal reaction is 160-250 DEG C, and the time is 24-72 h; the washing mode is centrifugation or suction filtration; and the drying mode is freeze drying or vacuum drying.

[0014] Preferably, the preparation method of the positive electrode is:

[0015] The sodium vanadate positive electrode active material, a conductive agent and a binder are weighed according to a proportion, mixed uniformly, ground into fine particles, added with an organic solvent dropwise, mixed into an ink-like slurry, coated on a current collector and dried to obtain the positive electrode.

[0016] Preferably, the preparation method of the calcium salt organic water hybrid electrolyte is:

[0017] The calcium salt is dissolved in a mixed liquid phase of an organic solvent and water, and stirred uniformly to obtain a uniform and stable calcium salt organic water hybrid electrolyte.

[0018] Preferably, the calcium salt is calcium perchlorate, with a chemical formula of Ca(ClO4)2·4H2O; the use amount ratio of the calcium salt to the mixed liquid phase of the organic solvent and water is 0.1 mol / L-2 mol / L; the organic solvent is at least one of propylene carbonate, dimethyl carbonate, acetonitrile, ethylene glycol dimethyl ether, dimethyl sulfoxide, and N,N-dimethylformamide; and the volume ratio of the organic solvent to water is 0.01:10-10:0.01.

[0019] The application further provides an energy storage device comprising the calcium ion battery.

[0020] The application further provides an electrical equipment comprising the calcium ion battery.

[0021] Compared with the prior art, the application has the beneficial effects that:

[0022] The calcium ion battery has the following advantages: the sodium vanadate with large interlayer spacing containing crystal water is used as the positive active material, the charge effect between the calcium ions and the lattice atoms is shielded by water molecules as much as possible, more calcium ions are allowed to be stored and higher stability is allowed in structure, the capacity performance and the energy density are greatly improved; the calcium salt organic water hybrid electrolyte is used, the desolvation energy is reduced by regulating the solvation structure of the calcium ions, compared with the pure organic solvent, the introduction of water not only has a certain flame retardant effect, but also greatly improves the ionic conductivity of the electrolyte, and the better rate performance is brought by the faster kinetics.

[0023] The energy storage device and the electrical equipment both have large capacity and excellent rate performance, and have high energy density and high power density. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 The XRD pattern of the sodium vanadate positive active material of the present embodiment 1;

[0025] Figure 2 The SEM pattern of the sodium vanadate positive active material of the present embodiment 1;

[0026] Figure 3 The rate performance diagram of the three-electrode battery (beaker battery) of the present embodiment 4;

[0027] Figure 4 The cycle performance diagram of the three-electrode battery (beaker battery) of the present embodiment 4. DETAILED DESCRIPTION

[0028] The application will be described in further detail below with reference to the drawings and specific embodiments. The following description is preferred embodiments of the application, it should be pointed out that for those skilled in the art, without departing from the principles of the embodiments of the application, can make several improvements and refinements, these improvements and refinements are also considered within the scope of protection of the application.

[0029] The application provides a calcium ion battery, comprising a positive electrode, a negative electrode, and a separator and a calcium salt electrolyte between the positive electrode and the negative electrode, the positive electrode comprises a sodium vanadate positive electrode active material, the sodium vanadate positive electrode active material is a sodium ion pre-embedded crystalline water-containing vanadate; and / or, the calcium salt electrolyte is a calcium salt organic water hybrid electrolyte.

[0030] The chemical formula of the sodium vanadate positive electrode active material is Na x V y O z ·nH2O, wherein 0 16 ·2H2O, or Na 1.2 V3O8·2.8H2O.

[0031] The preparation method of the sodium vanadate positive electrode active material is:

[0032] Vanadium pentoxide and sodium hydroxide are weighed according to the stoichiometric ratio, mixed and dissolved in deionized water;

[0033] The mixed solution is stirred, then transferred to a polytetrafluoroethylene reactor for hydrothermal reaction;

[0034] Cooling, washing with deionized water and ethanol, suction filtration, and drying to obtain the calcium ion battery sodium vanadate positive electrode active material.

[0035] The molar ratio of vanadium pentoxide and sodium hydroxide is preferably 1:1; the stirring time is preferably 30 min; the temperature of the hydrothermal reaction is preferably 160-250 DEG C, and the time is preferably 24-72 h; the washing method is preferably centrifugation or suction filtration, which is used to remove unreacted substances and reaction byproducts; and the drying method is preferably freeze-drying or vacuum drying, which is used to remove water and ethanol in the product.

[0036] The preparation method of the positive electrode is:

[0037] The sodium vanadate positive electrode active material, the conductive agent and the binder are weighed according to the proportion, mixed uniformly and ground into fine particles, organic solvent is added dropwise, mixed into an ink-like slurry, coated on the current collector, and dried to obtain the positive electrode.

[0038] The conductive agent includes but is not limited to Ketjen black, acetylene black, carbon nanotube, etc. The binder includes but is not limited to polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), etc. The organic solvent is preferably N-methyl pyrrolidone (NMP). The positive electrode current collector includes but is not limited to carbon fiber cloth, graphite paper, aluminum foil, copper foil, titanium foil, etc. The positive electrode material includes, by weight percentage, sodium vanadate positive electrode active material 60-90%, conductive agent 5-30%, and binder 5-10%.

[0039] The preparation method of the calcium salt organic water hybrid electrolyte is as follows:

[0040] The calcium salt is dissolved in a mixed liquid phase of an organic solvent and water, and stirred uniformly to obtain the uniform and stable calcium salt organic water hybrid electrolyte.

[0041] The calcium salt is preferably calcium perchlorate, and its chemical formula is Ca(ClO4)2·4H2O. The introduction of perchlorate enables some mutually insoluble organic phase and water phase (for example, propylene carbonate and water are not mutually soluble) to be combined, thereby obtaining a uniform and stable electrolyte, which is also the key to the application of the organic water hybrid electrolyte. The use amount ratio of the calcium salt to the mixed liquid phase of the organic solvent and water is preferably 0.1 mol / L-2 mol / L. The organic solvent is preferably at least one of propylene carbonate, dimethyl carbonate, acetonitrile, ethylene glycol dimethyl ether, dimethyl sulfoxide, N,N-dimethylformamide, etc. The volume ratio of the organic solvent to water is preferably 0.01:10-10:0.01, for example, 9.9:0.1, 8:2, 5:5, etc.

[0042] The calcium ion battery of the application uses sodium vanadate with large interlayer spacing containing crystal water as a positive electrode active material, and the water molecules shield the charge effect between calcium ions and lattice atoms as much as possible, so that more calcium ions can be stored and higher stability is allowed from the structure, which greatly improves the capacity performance and energy density. The calcium salt organic water hybrid electrolyte is used, and the solvation structure of calcium ions is regulated to reduce the desolvation energy. Compared with pure organic solvents, the introduction of water not only has a certain flame retardant effect, but also greatly improves the ionic conductivity of the electrolyte, and faster kinetics response brings better rate performance. The calcium ion battery of the application has large capacity and excellent rate performance, and has high energy density and high power density.

[0043] The application further provides an energy storage device including the calcium ion battery as described above, and thus has at least the same advantages as the calcium ion battery, has large capacity and excellent rate performance, and has high energy density and high power density.

[0044] The aforementioned energy storage devices refer to power storage devices that primarily use calcium-ion batteries as the power storage source, including but not limited to home energy storage systems or distributed energy storage systems. For example, in a home energy storage system, electricity is stored in calcium-ion batteries that serve as the power storage source, and the electricity stored in the calcium-ion batteries is consumed as needed to enable the use of various devices such as household appliances.

[0045] The present invention also provides an electrical device comprising the calcium ion battery described above, and thus having at least the same advantages as the calcium ion battery described above, having a large capacity and excellent rate performance, and having both high energy density and high power density.

[0046] The aforementioned electrical equipment includes, but is not limited to, electronic products, power tools, or electric vehicles. Electronic products are electronic devices that use calcium-ion batteries as their operating power source to perform various functions (e.g., playing music). Power tools are power tools that use calcium-ion batteries as their driving power source to move parts (e.g., drill bits). Electric vehicles are electric vehicles (including electric bicycles and electric cars) that rely on potassium-ion secondary batteries as their driving power source, and may also be vehicles equipped with other drive sources besides calcium-ion batteries, including hybrid vehicles.

[0047] The present invention will be further described in detail below with reference to embodiments and comparative examples.

[0048] Example 1

[0049] The preparation process of sodium vanadate positive electrode active material is as follows:

[0050] Weigh out vanadium pentoxide (V2O5) and sodium hydroxide (NaOH) in a molar ratio of 1:1, mix them, and dissolve them in 40 mL of deionized water;

[0051] Stir for 30 minutes, then transfer the mixture to a polytetrafluoroethylene reactor and hydrothermally heat at 200 degrees Celsius for 48 hours.

[0052] After cooling, the material was purified by centrifugation followed by filtration. During the process, it was washed 10 times with both deionized water and ethanol. The resulting solid was then vacuum-dried at 80°C for 12 hours to obtain sodium vanadate positive electrode active material (Na₂V₆O₂). 16 ·2H2O).

[0053] like Figure 1 The figure shows the XRD pattern of the sodium vanadate positive electrode active material of this embodiment. As can be seen from the figure, the sodium vanadate positive electrode active material of this embodiment is a layered material, and the interlayer spacing in the (001) direction is... like Figure 2As shown, the SEM image of the sodium vanadate positive electrode active material of the embodiment, from which it can be seen that the sodium vanadate positive electrode active material of the embodiment is a nanorod structure.

[0054] Example 2

[0055] The positive electrode tab is prepared as follows:

[0056] The sodium vanadate positive electrode active material (Na2V6O 16 2H2O) prepared in Example 1 is mixed uniformly with Ketjen black and polyvinylidene fluoride at a mass ratio of 6:3:1 and ground into fine particles, an appropriate amount of NMP (N-methyl pyrrolidone) solvent is added dropwise, mixed into an ink-like slurry, and coated on a carbon cloth current collector cut into about 1 cm x 1 cm, and then vacuum dried at 80°C for 12 h. The loading of the sodium vanadate positive electrode active material is in the range of 1.5-2.5 mg.

[0057] Example 3

[0058] The calcium salt organic aqueous hybrid electrolyte is prepared as follows:

[0059] The calcium perchlorate salt is dissolved in a mixed liquid phase of propylene carbonate and water (volume ratio of propylene carbonate to water is 4:1) at a proportion of 1 mol / L, and stirred uniformly to obtain a uniform and stable electrolyte.

[0060] Example 4

[0061] The three-electrode battery (beaker battery) is assembled as follows:

[0062] The dried positive electrode tab prepared in Example 2 is clamped on a platinum electrode clamp as a working electrode, a platinum sheet electrode is used as a counter electrode, and an Ag + / Ag electrode is used as a reference electrode, the calcium salt organic aqueous hybrid electrolyte prepared in Example 3 is added to the beaker so that the positive electrode tab is completely soaked, and the three-electrode battery (beaker battery) is obtained.

[0063] The three-electrode battery (beaker battery) of the embodiment is subjected to electrochemical performance testing, and the positive electrode tab is subjected to characterization testing during the charging and discharging process. Figure 3 The rate performance graph of the three-electrode battery (beaker battery) of the embodiment, from which it can be seen that the reversible capacity is greater than 217 mAh / g at a current density of 0.5 A / g, and the reversible capacity is still 68.2 mAh / g at a large current density of 20 A / g. Figure 4 The cycle performance graph of the three-electrode battery (beaker battery) of the embodiment, the capacity is maintained above 90 mAh / g after 500 cycles at a large current density of 10 A / g.

[0064] In summary, compared with the prior art, the beneficial effects of the present application are that:

[0065] The calcium ion battery of the application adopts layered sodium vanadate with large interlayer spacing containing crystal water as a positive active material, shields the charge effect between calcium ions and lattice atoms by water molecules as much as possible, and structurally allows more calcium ions to be stored and higher stability, greatly improving the capacity performance and energy density; the calcium salt organic water hybrid electrolyte is used, the desolvation energy is reduced by regulating the solvation structure of calcium ions, compared with pure organic solvent, the introduction of water not only has a certain flame retardant effect, but also greatly improves the ionic conductivity of the electrolyte, and the faster kinetic response brings better rate performance. The calcium ion battery of the application has large capacity and excellent rate performance, has high energy density and high power density, and has a reversible capacity of more than 217mAh / g at a current density of 0.5A / g, a reversible capacity of 68.2mAh / g at a large current density of 20A / g, and a capacity retention of more than 90mAh / g after 500 cycles at a large current density of 10A / g.

[0066] The energy storage device and the power utilization device of the application both have large capacity and excellent rate performance, and have high energy density and high power density.

[0067] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the application, and not to limit them; although the application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement for part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the application.

Claims

1. A calcium-ion battery, comprising a positive electrode, a negative electrode, a separator and a calcium salt electrolyte between the positive and negative electrodes, characterized in that, The positive electrode includes a sodium vanadate positive electrode active material, which is a sodium ion pre-intercalated vanadate containing water of crystallization; and the calcium salt electrolyte is a calcium salt organic water hybrid electrolyte; The sodium vanadate positive electrode active material is Na2V6O. 16 ·2H2O, the preparation process is as follows: Weigh out vanadium pentoxide and sodium hydroxide in a molar ratio of 1:1, mix them, and dissolve them in 40 mL of deionized water; Stir for 30 minutes, then transfer the mixture to a polytetrafluoroethylene reactor and hydrothermally heat at 200 degrees Celsius for 48 hours. After cooling, the material was purified by centrifugation followed by filtration. During the process, the material was washed 10 times with deionized water and ethanol. The solid was obtained by filtration and then vacuum dried at 80°C for 12 hours to obtain sodium vanadate positive electrode active material. The positive electrode preparation method is as follows: Na2V6O 16 • 2H2O was mixed with Ketjen black and polyvinylidene fluoride in a mass ratio of 6:3:1 and ground into fine particles. An appropriate amount of NMP (N-methylpyrrolidone) solvent was added dropwise to form an ink-like slurry. This slurry was then coated onto a carbon cloth current collector cut into pieces of approximately 1cm × 1cm and subsequently dried under vacuum at 80°C for 12 hours. The loading of sodium vanadate positive electrode active material ranged from 1.5 to 2.5 mg. The calcium salt electrolyte is a calcium salt organic-water hybrid electrolyte, and its preparation process is as follows: Calcium perchlorate salt was dissolved in a mixed liquid phase of propylene carbonate and water at a ratio of 1 mol / L and stirred until homogeneous to obtain a uniform and stable electrolyte. The volume ratio of propylene carbonate to water in the mixed liquid phase was 4:

1.

2. An energy storage device, characterized in that, Including the calcium-ion battery as described in claim 1.

3. An electrical appliance, characterized in that, Including the calcium-ion battery as described in claim 1.

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