A high-voltage, high-pseudocapacitance P2-type layered cathode material and its solid-state sodium battery

Abstract

The present invention discloses a P2-type layered cathode material with high voltage and high pseudocapacitance ratio and a solid-state sodium battery thereof. According to the chemical formula, the required amounts of Na2CO3, Li2CO3, NiO, Mn2O3, CaO, and TiO2 are added to a ball mill, ball milling beads are placed, and a ball mill is used to obtain a powder. The milled powder is pressed into pellets, placed in a muffle furnace, and calcined to obtain the cathode material Na 0.68 Li 0.10 Ni 0.25 Mn 0.63 Ca 0.01 Ti 0.01 The present invention adopts a simple solid phase method to synthesize the typical P2 type sodium battery positive electrode material Na 0.68 Ni 0.25 Mn 0.75 O2 is co-doped with Li, Ca, and Ti elements to obtain a P2-Na with high voltage resistance and high pseudocapacitance ratio. 0.68 Li 0.10 Ni 0.25 Mn 0.63 Ca 0.01 Ti 0.01 O2 layered positive electrode material. This material has a smoother particle surface and ultra-high pseudocapacitance, resulting in excellent rate and cycle performance in liquid batteries. The present inventors also used this material to fabricate solid-state sodium batteries, which exhibited more stable cycle performance than liquid batteries and were found to have better structural stability in solid-state batteries.

Description

Technical Field

[0001] The present invention belongs to the field of battery materials, and specifically relates to a P2-type layered positive electrode material with high voltage and high pseudocapacitance ratio and a solid-state sodium battery thereof. Background Art

[0002] Compared with lithium-ion batteries, sodium-ion batteries (SIBs) are considered to be a low-cost and more sustainable device. At the same time, solid-state sodium batteries (SSBs) have the advantages of high energy density and good safety, which can effectively overcome the key challenges of relatively low energy and cycle life. Compared with traditional organic liquid electrolytes, solid electrolytes not only improve safety, but also inhibit the growth of Na dendrites during the cycle, thereby improving the cycle stability. Most solid-state sodium battery studies use NaCrO2 or Na3V2(PO4)3 as the cathode, mainly due to their low operating voltage and excellent rate performance, which match various solid electrolytes. However, both materials have the problems of limited energy density and low operating voltage (most reported voltages are less than 4.0 V). Therefore, the development of SSBs with high energy density and high operating voltage remains a huge challenge, and the development of SSBs is urgently needed. Summary of the Invention

[0003] The object of the present invention is to provide a P2-type layered positive electrode material with high voltage and high pseudocapacitance ratio and a solid-state sodium battery thereof.

[0004] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0005] A high-voltage, high-pseudocapacitance P2-type layered cathode material Na 0.68 Li 0.10 Ni 0.25 Mn 0.63 Ca 0.01 Ti 0.01 The method for preparing O2 comprises the following steps:

[0006] 1) According to the chemical formula, add appropriate amounts of Na2CO3, Li2CO3, NiO, Mn2O3, CaO, and TiO2 into the ball mill, add appropriate amount of ball milling beads, and use a speed of 900~1100 r min -1 Ball mill for 0.4-0.6 h to obtain powder;

[0007] 2) The ball-milled powder was pressed into pellets at 7.5-8.5 MPa and placed in a muffle furnace at 4.5-5.5°C min -1 After the heating rate was raised to 900~1000℃ and calcined for 11~13 h, a P2-type layered cathode material Na with high voltage and high pseudocapacitance ratio was obtained. 0.68Li 0.10 Ni 0.25 Mn 0.63 Ca 0.01 Ti 0.01 O2(NM-L10CT).

[0008] The positive electrode material Na 0.68 Li 0.10 Ni 0.25 Mn 0.63 Ca 0.01 Ti 0.01 Application of O2 in sodium ion batteries:

[0009] (1) Liquid battery assembly: The positive electrode material Na 0.68 Li 0.10 Ni 0.25 Mn 0.63 Ca 0.01 Ti 0.01 O2, polyvinylidene fluoride (PVDF) and carbon black conductive agent (SP) were mixed and ground in a mass ratio of 8:1:1 and then evenly coated on a 1 cm 2 The positive electrode was a carbon-coated aluminum foil, the negative electrode was metallic sodium, and the electrolyte was 0.8 M NaClO4 in propylene carbonate (PC) solvent (fluoroethylene carbonate (FEC) was an additive).

[0010] (2) Solid-state battery assembly: using Na3Zr2Si2PO 12 (NZSP) is a solid electrolyte with Na 0.68 Li 0.10 Ni 0.25 Mn 0.63 Ca 0.01 Ti 0.01 O2 is used as the positive electrode and metallic sodium is used as the negative electrode to assemble the NM-L10CT / NZSP / Na solid-state sodium battery. The battery assembly is carried out in a glove box under argon protection (oxygen and moisture content <1 ppm).

[0011] The present invention adopts the above technical solution and adopts a simple solid phase method to synthesize the typical P2 type sodium battery positive electrode material Na 0.68 Ni 0.25 Mn 0.75 O2 is co-doped with Li, Ca, and Ti elements to obtain a P2-Na with high voltage resistance and high pseudocapacitance ratio. 0.68 Li 0.10 Ni 0.25 Mn 0.63 Ca 0.01 Ti 0.01O2 layered cathode material. This material has a smoother particle surface and ultra-high pseudocapacitance (>90%), resulting in excellent rate and cycle performance in liquid batteries. The present inventors also used this material to fabricate solid-state sodium batteries, which exhibited more stable cycle performance than liquid batteries and were found to have better structural stability in solid-state batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 These are the XRD patterns of NM and NM-L10CT materials.

[0013] Figure 2 SEM images of NM (a) and NM-L10CT (b).

[0014] Figure 3 NM (a) and NM-L10CT (b) in the range of 0.1 to 1.0 mV s −1 CV curves at different scan rates; the percentage of capacitance contribution and diffusion contribution of NM (c) and NM-L10CT (d) in the charge storage process at different scan rates.

[0015] Figure 4 Electrochemical performance of NM and NM-L10CT at 2.0-4.3 V: (a) charge-discharge curve at 0.1 C, (b) rate curve, and (c) 1 C cycle curve.

[0016] Figure 5 Electrochemical performance of NM and NM-L10CT: 0.1 C charge-discharge curves: (a) 2.0-4.4 V, (b) 2.0-4.5 V; 1 C cycle curves: (c) 2.0-4.4 V, (d) 2.0-4.5 V.

[0017] Figure 6 Electrochemical performance of NM-L10CT / NZSP / Na solid-state sodium battery at 2.0-4.3 V: (a) 1 C charge-discharge curves at each cycle, (b) rate curve, (c) 1 C cycling curve. (d) Cycling curve of NM-LCT, (e) Cycling curve of NM-L10CT / NZSP / Na at 2.0-4.2 V.

[0018] Figure 7 XRD patterns of NM-L10CT and NM-L10CT / NZSP / Na electrodes before and after 200 cycles at 2.0-4.3 V.

[0019] Figure 8Liquid battery electrode after 200 cycles at 2.0-4.3 V: (a), (b) TEM image, (c) corresponding FFT image and solid-state battery electrode: (d), (e) TEM image, (f) corresponding FFT image. DETAILED DESCRIPTION

[0020] In the following embodiments, the typical P2 type sodium battery positive electrode material Na 0.68 Ni 0.25 Mn 0.75 O2 is abbreviated as NM, and the positive electrode material Na after NM is co-doped with Li, Ca, and Ti elements 0.68 Li 0.10 Ni 0.25 Mn 0.63 Ca 0.01 Ti 0.01 O2 is recorded as NM-L10CT. Example

[0021] P2-type layered cathode material Na 0.68 Li 0.10 Ni 0.25 Mn 0.63 Ca 0.01 Ti 0.01 Preparation method of O2:

[0022] 1) According to the chemical formula, add appropriate amounts of Na2CO3, Li2CO3, NiO, Mn2O3, CaO, and TiO2 into a ball mill, add appropriate amount of ball mill beads, and use a rotation speed of 1000 r min -1 The mixture was ball milled for 0.5 h to obtain powder;

[0023] 2) The ball-milled powder was pressed into pellets at 8.0 MPa and placed in a muffle furnace at 5°C min -1 After the heating rate was raised to 900℃ and calcined for 12 h, the P2-type layered cathode material Na with high voltage and high pseudocapacitance ratio was obtained. 0.68 Li 0.10 Ni 0.25 Mn 0.63 Ca 0.01 Ti 0.01 O2 (NM-L10CT). Example

[0024] Application of cathode material NM-L10CT in sodium ion batteries:

[0025] (1) Liquid battery assembly: NM-L10CT, PVDF and SP were mixed and ground in a mass ratio of 8:1:1 and then evenly coated on a 1 cm 2The carbon-coated aluminum foil was used as the positive electrode, the negative electrode was metallic sodium, and the electrolyte was 0.8 M NaClO4 in PC solvent (FEC was an additive).

[0026] (2) Solid-state battery assembly: using Na3Zr2Si2PO 12 (NZSP) was used as the solid electrolyte, NM-L10CT was used as the positive electrode, and metallic sodium was used as the negative electrode to assemble the NM-L10CT / NZSP / Na solid-state sodium battery. The battery assembly was carried out in a glove box under argon protection (oxygen and moisture content <1 ppm).

[0027] Among them, Na3Zr2Si2PO 12 The preparation process of (NZSP) solid electrolyte is as follows: 1) Using the traditional solid phase method, Na2CO3, SiO2, ZrO2, and NH4H2PO4 are weighed according to the stoichiometric ratio and placed in a ball mill. Isopropyl alcohol is used as a grinding aid and the raw materials are ground at 600 r min. -1 2) After drying, the powder was heated in a muffle furnace at 900°C for 10 h, removed, and ball-milled again. The dried powder was pressed into pellets at 20 MPa and sintered in a high-temperature muffle furnace at 1200°C for 15 h to obtain the NZSP solid electrolyte.

[0028] Comparative Example 1

[0029] Cathode material Na 0.68 Ni 0.25 Mn 0.75 Application of O2 (NM) in sodium ion batteries:

[0030] Liquid battery assembly: NM, PVDF and SP were mixed and ground in a mass ratio of 8:1:1 and then evenly coated on a 1 cm 2 The carbon-coated aluminum foil was used as the positive electrode, the negative electrode was metallic sodium, and the electrolyte was 0.8 M NaClO4 in PC solvent (FEC was an additive).

[0031] Figure 1 The XRD patterns of NM and NM-L10CT materials show that both cathode materials have space groups of P63 / mmc The P2-type layered structure is characterized by the absence of impurity peaks, indicating that elements such as Li, Ca, and Ti are uniformly incorporated into the material. Furthermore, a zoomed-in XRD pattern from 15.5° to 17.0° reveals a rightward shift in the (002) diffraction peak of NM-L10CT, indicating a contraction of the material's lattice parameter, the c-axis, and a decrease in interlayer spacing.

[0032] Figure 2The SEM images of NM (a) and NM-L10CT (b) show that the surface of NM material is relatively rough, and there are secondary particles on the surface with a size of about 2-5 um, while the surface of NM-L10CT material is smoother and has a more obvious layered morphology with a size of about 1-3 um.

[0033] Figure 3 The speed CV curves of NM (a) and NM-L10CT (b) at different sweep numbers are shown. The formula i(V) = k1v + k2v is used. 1 / 2 Further quantitative determination of the pseudocapacitive behavior of the material shows that as the scan rate increases, the capacitance contribution also gradually increases (e.g. Figure 3 c, d), where it can be observed that the capacitance contribution of NM-L10CT exceeds 90% at any scan rate, indicating that it is a high pseudocapacitive cathode material with excellent sodium ion diffusion ability.

[0034] Depend on Figure 4 It can be seen from a that the charge and discharge curve of NM is a multi-voltage platform charge and discharge process, while the charge and discharge curve of NM-L10CT shows a solid solution charge and discharge process. In particular, NM has an extremely long voltage platform around 4.2 V. This is mainly because the TM layer is prone to P2-O2 phase transition in the deep Na-free state, and at this voltage, the ARRs reaction is triggered. Solid solution charge and discharge reduces the irreversible phase transition during the charge and discharge process, and it can be clearly seen that the ARRs reaction is suppressed. Figure 4 In b, the specific capacity of NM-L10CT at high rates of 5 C and 10 C increased from 66.9 mAh g of NM to 10. −1 , 49.7 mAh g −1 Increased to 102.88 mAh g −1 , 94.31 mAh g −1 At the same time, Figure 4 As can be seen from Figure c, the capacity retention rate of NM-L10CT after 200 cycles at 1 C is improved from 26.9% of NM to 78.9%, still showing excellent cycle stability.

[0035] Figure 5 The electrochemical performances of NM and NM-L10CT at 2.0-4.4 V and 2.0-4.5 V are shown. Figure 5c, d, NM-L10CT has a capacity retention rate of 72.6% after 200 cycles at 1 C at 2.0-4.4 V (67.3% at 2.0-4.5 V), which is significantly better than NM's capacity retention rate of 28.8% (24.8% at 2.0-4.5 V). Even at a high operating voltage of 2.0-4.5 V, NM-L10CT can still maintain good cycling stability, indicating that this material is also a high-voltage resistant positive electrode material.

[0036] Depend on Figure 6 It can be seen that in the voltage range of 2.0-4.3 V, the capacity at 1 C current rate is as high as 115.4 mAhg -1 , the capacity retention rate after 300 cycles is 74.2% ( Figure 6 c), which is significantly better than the retention rate of NM materials in liquid batteries (58.5%) Figure 6 d) By Figure 6 b shows that the average specific capacities at 0.1 C, 0.2 C, 0.5 C, 1 C, 2 C, 5 C, 10 C and 0.2 C are 120.9 mAh g -1 , 117.4 mAh g -1 、110.5 mAh g -1 、104.0 mAh g -1 , 102.2 mAh g -1 , 97.1 mAh g -1 , 74.5 mAh g -1 and 1116.2 mAh g -1 When the current density is switched from 10 C to 0.2 C, the SSBs also exhibit excellent rate performance with almost no capacity degradation (99.0% of the original capacity at 0.2 C), indicating their excellent reversibility and stable and reliable interface. The capacity retention rate can still be as high as 81.2% after 500 cycles at 1 C at 2.0-4.2 V ( Figure 6 e), showing excellent long-term cycling performance.

[0037] like Figure 7 It can be seen that the electrode still maintains the P2 type structure and no phase change occurs. Through the local magnification image of 15.5-17°, it can be seen that the electrode diffraction peaks after cycling are all shifted to low angles, indicating that the lattice parameter c becomes larger and the interlayer spacing expands. In addition, the shift of the solid-state battery after cycling is significantly smaller than that of the liquid battery, indicating that the NZSP solid electrolyte in the solid-state system further promotes the reversibility of the NM-L10CT material.

[0038] Figure 8a, b, d, and e are TEM images of NM-L10CT material and liquid-solid electrode sheet, respectively. As can be seen from the figure, in the liquid battery system, the active material of the electrode is severely corroded, and the lattice is distorted, which seriously damages the Na + In contrast, in solid-state batteries, a uniform amorphous passivation layer of approximately 1.47 nm thick can be observed on the surface of the material, ensuring a very uniform interface between the electrode and the electrolyte. Furthermore, the layered structure of the active material in the electrode remains very intact, resulting in superior electrochemical performance in solid-state batteries. Figure 8 c, f are the lattice fringes of the (004) peak of the active material in the electrode and the corresponding Fourier transform image, respectively. It can be seen that the (004) peak interlayer spacing of the electrode in the solid-state battery is 0.28 nm, which is slightly smaller than the (004) peak interlayer spacing of the liquid state of 0.30 nm, which also corresponds to Figure 7 The diffraction peak of the liquid battery shifts to lower angles. Fourier transform images also reveal that in the liquid battery system, polycrystallization gradually occurs in the single crystal structure, while in the solid system, a very complete hexagonal single crystal layered structure is still maintained.

[0039] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made according to the scope of the patent application of the present invention should fall within the scope of the present invention.

Claims

1. A method for preparing a P2-type layered cathode material with high voltage and high pseudocapacitance ratio, characterized in that: The following steps are involved: 1) According to the chemical formula, the required amounts of Na2CO3, Li2CO3, NiO, Mn2O3, CaO, and TiO2 are added to a ball mill, ball mill beads are placed in the ball mill, and powder is obtained; 2) Press the milled powder into pellets and place them in a muffle furnace at 4.5-5.5°C min -1 After the heating rate was raised to 900~1000℃ and calcined for 11~13h, a P2-type layered cathode material Na with high voltage and high pseudocapacitance ratio was obtained. 0.68 Li 0.10 Ni 0.25 Mn 0.63 Ca 0.01 Ti 0.01 O2.

2. The method for preparing a P2-type layered cathode material with high voltage and high pseudocapacitance ratio according to claim 1, characterized in that: The ball mill has a rotation speed of 900-1100 r / min. -1 , the ball milling time is 0.4~0.6h.

3. The method for preparing a P2-type layered positive electrode material with high voltage and high pseudocapacitance ratio according to claim 1, characterized in that: The pressure for pressing the powder into pellets is 7.5~8.5Mpa.

4. The positive electrode material Na obtained by the preparation method according to any one of claims 1 to 3 0.68 Li 0.10 Ni 0.25 Mn 0.63 Ca 0.01 Ti 0.01 O2.

5. The cathode material Na as claimed in claim 4 0.68 Li 0.10 Ni 0.25 Mn 0.63 Ca 0.01 Ti 0.01 Application of O2 in sodium-ion batteries.

6. The use according to claim 5, characterized in that The positive electrode material Na 0.68 Li 0.10 Ni 0.25 Mn 0.63 Ca 0.01 Ti 0.01 O2 assembled into liquid batteries: the positive electrode material Na 0.68 Li 0.10 Ni 0.25 Mn 0.63 Ca 0.01 Ti 0.01 O2, PVDF and SP were mixed and ground in a mass ratio of 8:1:1 and evenly coated on a 1cm 2 The carbon-coated aluminum foil was used as the positive electrode, the negative electrode was metallic sodium, and the electrolyte was 0.8 mol / L NaClO4 in propylene carbonate solvent.

7. The use according to claim 5, characterized in that The positive electrode material Na 0.68 Li 0.10 Ni 0.25 Mn 0.63 Ca 0.01 Ti 0.01 O2 assembled into solid-state batteries: using Na3Zr2Si2PO 12 As solid electrolyte, Na 0.68 Li 0.10 Ni 0.25 Mn 0.63 Ca 0.01 Ti 0.01 O2 is used as the positive electrode and metallic sodium is used as the negative electrode to assemble the NM-L10CT / NZSP / Na solid-state sodium battery. The battery assembly is carried out in a glove box under argon protection, and the oxygen and moisture contents are both <1ppm.

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