A homogenization method for improving discharge voltage of lithium-chromium-based metal oxide batteries

Abstract

The application discloses a homogenizing method for improving discharge voltage of a lithium-chromium-based metal oxide battery, which adopts a high-DN-value solvent and a low-density conductive agent to modify a chromium-based metal oxide electrode; the chromium-based metal oxide is mixed with dry powder of the low-density conductive agent; PVDF powder is dissolved in DMSO, and then added into the mixed dry powder mixture after mixing, so as to prepare a slurry for coating electrode sheets. The application has the beneficial effect that the chromium metal oxide is treated by the solvent DMSO with high DN value and low boiling point, the interlayer spacing of the chromium metal oxide is increased, and the bond energy of the chromium-oxygen bond is reduced, so that the embedding of lithium ions and the subsequent conversion reaction are facilitated, and the discharge voltage of the battery is improved; meanwhile, the formed porous channel structure is also beneficial to the infiltration of electrolyte, and the electrochemical performance of the battery is improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of primary batteries, and particularly relates to a homogenizing method for improving the discharge voltage of a lithium-chromium-based metal oxide battery. BACKGROUND

[0002] With the development of human society, the demand of human beings for energy storage becomes more and more urgent. Among many energy storage devices, a lithium primary battery has been widely concerned due to its high specific energy and has been widely applied in many fields.

[0003] The chromium metal oxide material has a layered structure and has good rate performance based on the embedding-conversion mechanism. However, due to the existence of the conversion mechanism, the reaction kinetics is poor, and the polarization phenomenon is serious, which reduces the actual discharge voltage. SUMMARY

[0004] To solve the above technical problems, the application provides a homogenizing method for improving the discharge voltage of a lithium-chromium-based metal oxide battery.

[0005] The technical scheme adopted by the application is that the homogenizing method for improving the discharge voltage of a lithium-chromium-based metal oxide battery is used to modify the chromium-based metal oxide electrode by using a high-DN-value solvent and a low-density conductive agent.

[0006] Preferably, the chromium-based metal oxide and the low-density conductive agent are mixed uniformly in dry powder form; the PVDF powder is dissolved in DMSO, and after being mixed uniformly, the mixed dry powder is added to the mixed dry powder, and the slurry for coating the pole piece is prepared after being mixed uniformly.

[0007] Preferably, the low-density conductive agent is high-specific-surface-area carbon.

[0008] Preferably, the specific steps are as follows:

[0009] The dry powder of the chromium-based metal oxide and the high-specific-surface-area carbon is sequentially added to a ball mill tank, wherein the mass percentage of the high-specific-surface-area carbon is 5%-15%, and the mass percentage of the chromium-based metal oxide is 85%-95%, and the dry powder is uniformly mixed by using a ball mill;

[0010] The PVDF powder is dissolved in DMSO, heated and stirred at 45 DEG C, and the mass fraction of the PVDF is 6%-8%;

[0011] The PVDF solution is added to the dry powder mixture, and the mass percentage of the PVDF is 2-4%; and then DMSO is added to adjust the solid content of the slurry to 25%-35%, and the slurry is uniformly mixed by using a ball mill.

[0012] Preferably, the specific surface area of the high-specific-surface-area carbon is greater than 1200 m 2When mixing the dry powder, the ball mill speed is 230-270 r / min and the ball milling time is 1-1.5 h.

[0013] Preferably, the molecular weight of PVDF is 300,000-450,000, the magnetic spindle speed is 200-300 r / min, and the stirring time is 18-24 h.

[0014] Preferably, the preparation process is carried out in a dry environment with a dew point temperature not higher than -40°C.

[0015] Electrode coating slurry prepared by a homogenization method to improve the discharge voltage of lithium chromium-based metal oxide batteries.

[0016] Lithium-chromium-based metal oxide batteries, including those with electrode coating slurry.

[0017] The advantages and positive effects of this invention are as follows: Using DMSO, a solvent with a high DN value and a low boiling point, to treat chromium metal oxide increases the interlayer spacing of the chromium metal oxide and reduces the bond energy of the chromium-oxygen bond, thereby facilitating lithium-ion insertion and subsequent conversion reactions, thus improving the battery's discharge voltage. Simultaneously, the formed porous structure also facilitates electrolyte wetting, enhancing the battery's electrochemical performance. The introduction of high specific surface area VC significantly improves the electrode's conductivity, further enhancing the battery's electrochemical performance. The preparation method is simple in operation, requires simple equipment, and is easy to implement. Attached Figure Description

[0018] Figure 1 Optical images of the electrode sheets prepared in Example 1;

[0019] Figure 2 The discharge curves of batteries assembled using ordinary homogenization and the electrodes prepared in Example 1 are shown.

[0020] Figure 3 This is a schematic diagram illustrating the interaction between the solvent DMSO and chromium metal oxide.

[0021] Figure 4 The XRD pattern of chromium metal oxide after DMSO treatment;

[0022] Figure 5 XPS spectra of chromium metal oxides after DMSO treatment. Detailed Implementation

[0023] The embodiments of the present invention will now be described with reference to the accompanying drawings.

[0024] The present application relates to a kind of homogenate method for improving lithium-chromium-based metal oxide battery discharge voltage, using high DN value solvent and low density conductive agent to modify chromium-based metal oxide electrode.Crushing chromium-based metal oxide and low-density conductive agent dry powder uniformly;Polyvinylidene fluoride (PVDF) powder is dissolved in DMSO, after mixing, it is added to the dry powder mixture, after mixing, the slurry for coating pole piece is prepared, the prepared slurry is coated on aluminum foil, after drying, lithium-chromium-based metal oxide pole piece can be obtained.The low-density conductive agent in some embodiments of the present application can be high specific surface area carbon.By introducing solvent with higher DN value, such as DMSO, in the homogenate process, part of the solvent molecules can be inserted into chromium metal oxide, thereby reducing the bond energy between chromium oxygen atoms and increasing the interlayer spacing of the material, thereby facilitating the insertion of lithium ions, and further improving the discharge voltage of the material.

[0025] The specific preparation method is as follows:

[0026] Step one: chromium-based metal oxide and high specific surface area carbon dry powder are added into a ball mill jar in sequence, wherein the mass fraction of high specific surface area carbon is 5%-15%, and the mass fraction of chromium-based metal oxide is 85%-95%, the dry powder is mixed uniformly by ball mill, the specific surface area of high specific surface area carbon is greater than 1200 m 2 / g, the rotation speed of ball mill is 230-270 r / min, and the ball milling time is 1-1.5 h;

[0027] Step two: PVDF powder is dissolved in DMSO, the molecular weight of PVDF is 300000-450000, heating is carried out at 45 DEG C by heating table, and stirring is carried out by magnetic stirrer, the rotation speed of magnetic stirrer is 200-300 r / min, the stirring time is 18-24 h, until PVDF is completely dissolved in DMSO, the mass fraction of PVDF is 6%-8%, and PVDF completely dissolved in DMSO forms a uniform and stable colloid;

[0028] Step three: the PVDF solution obtained in step two is added to the powder obtained in step one, the mass fraction of PVDF is controlled to be 2-4%, DMSO is further added to adjust the slurry, the solid content of the adjusted slurry is controlled to be 25%-35%, and the slurry is mixed uniformly by ball mill, the rotation speed of ball mill is 300-500 r / min, the stirring time is 10-12 h, until the final mixture is in uniform fluid state.

[0029] The preparation process of the above steps one to three is carried out in dry environment, and the dew point temperature is not higher than-40 DEG C.

[0030] The high specific surface area carbon with low density, high conductivity and high specific surface area is selected as the conductive agent of the electrode, and the mass ratio of the high specific surface area carbon is greatly increased, so that the active material and the conductive agent are more fully contacted, thereby ensuring the high conductivity of the electrode; meanwhile, the high DN value solvent DMSO is selected as the main solvent of the homogenate, the interlayer spacing of the chromium metal oxide is increased through the partial solvent embedding in the homogenization process, and the bond energy of the chromium-oxygen bond is effectively reduced through the induction effect, thereby being beneficial to the embedding of lithium ions and the fracture and recombination of the chromium-oxygen bond, and the discharge voltage of the battery is improved; similarly, the lower boiling point of DMSO relative to NMP makes it easier to remove from the pole piece, thereby having the advantage of energy saving, and the porous channel structure formed on the pole piece is also more conducive to the infiltration of the electrolyte on the pole piece.

[0031] The solvent DMSO with high DN value and low boiling point is used to treat the chromium metal oxide, the interlayer spacing of the chromium metal oxide is increased, and the bond energy of the chromium-oxygen bond is reduced, thereby being beneficial to the embedding of lithium ions and the occurrence of the subsequent conversion reaction, thereby improving the discharge voltage of the battery; meanwhile, the porous channel structure formed is also conducive to the infiltration of the electrolyte, and the electrochemical performance of the battery is improved. The introduction of the high specific surface area carbon greatly improves the conductivity of the pole piece, thereby further improving the electrochemical performance of the battery. As shown in Figure 3 The schematic diagram of the interaction between the solvent DMSO and the chromium metal oxide, the mechanism of the interaction between DMSO and the chromium-based metal oxide, and the fact that DMSO reduces the bond energy between the edge trivalent chromium and the internal hexavalent chromium of the layered material and oxygen, thereby being beneficial to the embedding of lithium ions and the occurrence of the subsequent conversion reaction. Figure 4 and Figure 5 The XRD spectrum and the XPS spectrum of the chromium metal oxide treated by DMSO are shown in Figures 1 and 2, respectively; it can be seen from the XRD spectrum that the characteristic peaks of the chromium metal oxide treated by DMSO shift to the small angle direction, which indicates that the interlayer spacing of the material is increased after the treatment by DMSO, and it can be found from the XPS spectrum that the bond energy between the chromium-oxygen bonds (including trivalent chromium and hexavalent chromium) is reduced after the treatment by DMSO.

[0032] The experimental methods of the operation steps are not specifically described in the following description of the application scheme, and are performed according to the corresponding product instructions. The instruments, reagents and consumables used in the examples can be purchased from commercial companies if not specifically stated.

[0033] Example 1

[0034] Step one: dry powder of chromium-based metal oxide and high specific surface area carbon is added into a ball mill jar in sequence for ball milling, wherein the high specific surface area carbon is selected from VC, the mass ratio of VC is 5%, and the specific surface area of VC is 1200m 2 / g, the mass ratio of chromium-based metal oxide is 95%, the rotation speed of the ball mill is 230 r / min, and the ball milling time is 1.5 h until the dry powder is uniformly mixed.

[0035] Step two: dissolve the PVDF powder in DMSO, the mass fraction of PVDF is 6%, use the heating table to heat at 45°C, and use the magnetic sub to stir, the rotation speed of the magnetic sub is 200 r / min, and the stirring time is 24 h until the PVDF is completely dissolved in DMSO to form a uniform and stable colloid.

[0036] Step three: add the PVDF solution obtained in step two to the powder obtained in step one, the mass ratio of PVDF is 2%, and at the same time, add DMSO to adjust the solid content of the slurry to 35%, and use the ball mill to mix the slurry uniformly, the rotation speed of the ball mill is 300 r / min, and the stirring time is 12 h until the final mixture is in a uniform fluid state.

[0037] The obtained slurry is coated on aluminum foil, and dried at 150°C to obtain a lithium-chromium-based metal oxide electrode.

[0038] The prepared lithium-chromium-based metal oxide electrode has uniform active material distribution, and the electrode picture is as shown in Figure 1 As can be seen from the optical photograph of the prepared lithium-chromium-based metal oxide electrode, the active material is uniformly distributed on the aluminum foil.

[0039] Example 2

[0040] Step one: add the dry powder of chromium-based metal oxide and VC to the ball mill jar in sequence, wherein the mass ratio of VC is 10%, the specific surface area of VC is 1200 m 2 / g, the mass ratio of chromium-based metal oxide is 90%, the rotation speed of the ball mill is 270 r / min, and the ball milling time is 1 h until the dry powder is uniformly mixed.

[0041] Step two: dissolve the PVDF powder in DMSO, the mass fraction of PVDF is 6%, use the heating table to heat at 45°C, and use the magnetic sub to stir, the rotation speed of the magnetic sub is 300 r / min, and the stirring time is 18 h until the PVDF is completely dissolved in DMSO to form a uniform and stable colloid.

[0042] Step three: add the PVDF solution obtained in step two to the powder obtained in step one, the mass ratio of PVDF is 4%, and at the same time, add DMSO to adjust the solid content of the slurry to 25%, and use the ball mill to mix the slurry uniformly, the rotation speed of the ball mill is 500 r / min, and the stirring time is 10 h until the final mixture is in a uniform fluid state.

[0043] Example 3

[0044] Step one: dry powder of chromium-based metal oxide and VC was added into a ball mill jar for ball milling, wherein the mass ratio of VC was 15%, the specific surface area of VC was 1200m 2 / g, the mass ratio of chromium-based metal oxide was 85%, the rotation speed of the ball mill was 270r / min, and the ball milling time was 1h until the dry powder was uniformly mixed.

[0045] Step two: PVDF powder was dissolved in DMSO, the mass fraction of PVDF was 6%, a heating table was used for heating at 45℃, and a magnetic stirrer was used for stirring at a rotation speed of 250r / min for 20h until the PVDF was completely dissolved in DMSO to form a uniform and stable colloid.

[0046] Step three: the PVDF solution obtained in step two was added to the powder obtained in step one, the mass ratio of PVDF was 2%, and DMSO was added to adjust the solid content of the slurry to 25%, and the slurry was uniformly mixed by a ball mill at a rotation speed of 4500r / min for 10h until the final mixture was in a uniform fluid state.

[0047] Example 4:

[0048] The slurry prepared in Example 1 was prepared into a lithium-chromium-based metal oxide battery, and the discharge test was carried out at room temperature at a current density of 1C. Compared with the battery prepared by the conventional homogenization method, the results are shown in Figure 2 , the battery prepared by the slurry of Example 1 has higher specific energy than the battery prepared by the conventional homogenization method.

[0049] From Figure 2 It can be seen that the lithium-chromium-based metal oxide battery obtained by the method of Example 1 has higher specific energy than the battery obtained by the conventional homogenization method, which is mainly because the high DN value solvent DMSO weakens the bond energy of chromium-oxygen bond and increases the interlayer spacing, thereby facilitating the diffusion of lithium ions and the occurrence of subsequent conversion reactions, thereby increasing the discharge voltage of the battery, and thus improving the specific energy of the battery. The use of high specific surface area VC can effectively improve the conductivity of the electrode and thus improve the specific energy of the material.

[0050] The above embodiments of the present application are described in detail, but the content described is only the preferred embodiment of the present application, and cannot be considered as limiting the scope of the present application. Any equivalent changes and improvements made within the scope of the present application should still be within the scope of the present application.

Claims

1. A homogenization method for increasing the discharge voltage of lithium-chromium-based metal oxide batteries, for preparing a slurry for coating the electrode sheets used in lithium-chromium-based metal oxide batteries, characterized by: The chromium-based metal oxide electrode is modified by using a high DN value solvent and a low-density conductive agent. The DMSO molecules of the high DN value solvent can be embedded into the chromium metal oxide, reduce the bond energy between chromium and oxygen atoms, be beneficial to the embedding of lithium ions and the fracture and recombination of chromium-oxygen bonds, increase the discharge voltage of the battery, and increase the interlayer spacing of the material, which is beneficial to the embedding of lithium ions. The low-density conductive agent is high specific surface carbon having a specific surface area of greater than 1200 m 2 / g; The chromium-based metal oxide and the dry powder of the low-density conductive agent are uniformly mixed, the PVDF powder is dissolved in DMSO, and the mixed dry powder mixture is added to the mixed dry powder mixture after being uniformly mixed to prepare the slurry for coating the pole piece. The preparation process is carried out in a dry environment, and the dew point temperature is not higher than-40 DEG C. The specific steps are as follows: The dry powder of the chromium-based metal oxide and the high specific surface area carbon is added to the ball mill jar in sequence, wherein the mass fraction of the high specific surface area carbon is 5%-15%, and the mass fraction of the chromium-based metal oxide is 85%-95%, and the dry powder is uniformly mixed by using a ball mill. The PVDF powder is dissolved in DMSO, the molecular weight of the PVDF is 300000-450000, the PVDF is heated and stirred at 45 DEG C, and the mass fraction of the PVDF is 6%-8%; the PVDF solution is added to the dry powder mixture, the mass fraction of the PVDF is 2-4%; DMSO is added to adjust the solid content of the slurry to 25%-35%, and the slurry is uniformly mixed by using a ball mill.

2. The pole piece coating slurry prepared by the uniform slurry method for improving the discharge voltage of the lithium chromium-based metal oxide battery according to claim 1.

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