Preparation method of all-solid-state lithium-sulfur battery composite positive electrode material

Abstract

The invention relates to the technical field of lithium batteries, in particular to a positive electrode material of a sulfide-based solid-state lithium battery and the lithium battery comprising the positive electrode. According to the short name of the P4SX (X = 10-40) / (conductive carbon) composite positive electrode, respectively metering powder of P2S5, S and conductive carbon, and mixing to obtain a precursor mixture; performing dry ball milling on the precursor mixture to obtain precursor powder, and performing high-temperature sintering to obtain a composite positive electrode powder precursor; and sieving the composite positive electrode powder with a 200-mesh sieve, mixing the undersize powder with the sulfide electrolyte sieved with a 400-mesh sieve, and carrying out ball milling to obtain the all-solid-state lithium-sulfur battery composite positive electrode material. By using the positive electrode material, the electrochemical performance and the cycling stability of the positive electrode material can be improved, the interface stability between a sulfide solid electrolyte and a sulfur positive electrode can be improved, and the interface impedance is reduced, so that the all-solid-state lithium-sulfur battery using the positive electrode material has good electrochemical performance and cycling stability.

Description

Technical Field

[0001] This application relates to the field of lithium battery technology, and in particular to a cathode material for solid-state lithium batteries. Background Technology

[0002] Human society has relied on energy utilization since its inception. Therefore, developing efficient, safe, and clean energy storage systems is essential. Among various energy storage systems, secondary batteries stand out due to their high energy storage characteristics. However, existing conventional lithium-ion batteries (LIBs) are limited in meeting the demands for high energy density and large-scale energy storage devices due to their high manufacturing costs, low energy density, and inherent safety issues. Secondary batteries contain lithium metal (low density and high electronegativity) and sulfur (1675 mAh g⁻¹). -1 The combination of high theoretical capacity can form 2600Wh / kg. -1 Or 2800Wh L -1 The theoretical capacity density of liquid lithium-sulfur batteries far exceeds that of lithium-ion batteries. Unfortunately, the shuttle effect of intermediate polysulfides hinders the development of liquid lithium-sulfur batteries. Polysulfides formed during the sulfur reaction are highly soluble in liquid electrolytes and can be transferred to the anode side through the electrolyte, leading to loss of active material and low coulombic efficiency. Although this problem can be suppressed by designing carbon scaffolds to capture sulfur, replacing the liquid electrolyte with a solid electrolyte is the most promising strategy to eliminate it.

[0003] In recent years, various solid-state electrolytes have been developed, including polymer electrolytes, oxide electrolytes, halide electrolytes, and sulfide electrolytes. Polymer electrolytes typically exhibit low ionic conductivity at room temperature and have limited effectiveness in suppressing the "shuttle effect" in lithium-sulfur batteries. For oxide solid-state electrolytes, mechanical stiffness is detrimental to the fabrication of composite sulfur cathodes. For halide electrolytes, although these materials offer advantages such as high ionic conductivity and high voltage stability, the electrochemical reaction between the halide electrolyte and the lithium metal anode is considered the most significant drawback. Sulfide solid-state electrolytes retain high ionic conductivity among these solid-state electrolytes and exhibit high similarity to sulfur cathodes, resulting in good chemical compatibility. Furthermore, sulfide solid-state electrolytes typically exhibit flexible physical properties, allowing for dense and tight physical contact with composite cathode components through cold pressing, which is beneficial for practical electrode tuning. Based on these characteristics, sulfide solid-state electrolytes are considered the most promising solid-state electrolytes for all-solid-state lithium-sulfur batteries (ASSLSB).

[0004] Because the sulfur cathode in sulfide-based all-solid-state lithium-sulfur batteries exhibits low electronic conductivity and large volume changes during cycling, it leads to rapid capacity decay and deteriorates interfacial properties, resulting in poor solid-solid contact at the electrolyte / cathode interface. Although many studies have improved the cycle reversibility of lithium batteries by modifying the sulfur cathode, the large volume changes and the formation of "dead sulfur" during cycling still cause rapid capacity decay. Conversely, combining conductive carbon, phosphorus, and sulfur elements through simple solid-state sintering to obtain a new cathode material offers a two-pronged approach.

[0005] This invention proposes a simple strategy based on MSx (M = I, P, Br) compounds, which generates a P4S compound in situ by co-sintering conductive carbon material, P2S5, and S. x A novel cathode material coated with conductive carbon effectively improves the cycle reversibility of sulfur cathodes and the interfacial performance with electrolytes. Summary of the Invention

[0006] To address the issues of large volume changes in existing sulfur cathodes and direct contact between conductive carbon and sulfide electrolytes in composite cathodes, this invention provides a novel method for preparing a composite cathode for all-solid-state lithium-sulfur batteries and an all-solid-state lithium-sulfur battery using this cathode material. The use of this cathode material improves the electrochemical performance and cycle stability of the cathode material, and also improves the interfacial stability between the sulfide solid electrolyte and the sulfur cathode, reducing interfacial impedance. This results in all-solid-state lithium-sulfur batteries using this cathode material exhibiting excellent electrochemical performance and cycle stability.

[0007] This invention provides a method for preparing an all-solid-state lithium-sulfur battery composite cathode material, comprising the following steps: weighing P2S5 and S according to different molar ratios, and preparing P4S... X (X = 10~40) precursor powder, P4S X Precursor powder (X = 10~40) is mixed with conductive carbon powder to obtain a precursor mixture; the precursor mixture is then dry-ball-milled to obtain precursor powder, which is then sintered at high temperature to obtain composite cathode powder. The composite cathode powder is passed through a 200-mesh sieve, and the powder that passes through the sieve is mixed with sulfide electrolyte that has passed through a 400-mesh sieve and ball-milled to obtain the all-solid-state lithium-sulfur battery composite cathode material.

[0008] Preferably, the sintering temperature is 250℃-500℃ and the sintering time is 12-24h.

[0009] Preferably, the conductive carbon is one or a mixture of several of reduced graphene oxide (rGO), carbon nanotubes (CNT), acetylene black (AB), or vapor-grown carbon nanofibers (VGCF).

[0010] Preferably, the P4S XThe material is P4S 26 P4S 32 Or P4S 38 .

[0011] The conductive carbon and P4S X The mixing mass ratio of (X=10~40) is (1:9)-(4:6).

[0012] The ball milling speed is 200-500 rpm, and the ball milling time is selected from 20-60 min depending on the speed.

[0013] This invention also provides a method for preparing a solid-state lithium battery, the method comprising the following steps:

[0014] 1) Prepare all-solid-state lithium-sulfur battery composite cathode material according to the above method;

[0015] 2) Weigh a certain mass of sulfide electrolyte powder, place it in a mold, apply a pressure of 100-150 MPa, hold the pressure for 60-90 seconds, and make an electrolyte sheet;

[0016] 3) Then weigh a certain amount of the positive electrode powder obtained in step 1), place it in the mold in step 2), apply a pressure of 300-450 MPa, hold the pressure for 150-210 s, and form a positive electrode sheet on the surface of the electrolyte sheet.

[0017] 4) Attach the lithium metal anode sheet to the other side of the sulfide electrolyte sheet, and then place conductive connecting rods on both sides of the positive and negative electrodes of the battery to obtain a complete all-solid-state lithium-sulfur battery.

[0018] Preferably, the thickness of the electrolyte sheet is between 450-600 μm;

[0019] Preferably, the sulfide electrolytic powder is obtained by ball milling and mixing Li2S, P2S5, and LiCl in a certain proportion, sintering at 460°C, and then passing the mixture through a 400-mesh sieve.

[0020] Beneficial effects

[0021] P4S x As a cathode material in all-solid-state lithium-sulfur batteries, P4S maintains a stable electrochemical reaction during battery cycling. x It exhibits good chemical stability, which can improve the interfacial stability between the cathode and the sulfide solid electrolyte, significantly reducing the interfacial resistance. Furthermore, P4S... xBy isolating the sulfide electrolyte from direct contact with conductive carbon, reducing electron conduction between the conductive carbon and the electrolyte, minimizing the decomposition of the sulfide electrolyte, and suppressing side reactions at the interface, all-solid-state lithium-sulfur batteries using this cathode material exhibit excellent electrochemical performance and cycle stability. This cathode material effectively reduces various problems inherent in sulfur cathodes, and its synthesis process is simple, reducing the number of steps in cathode synthesis and facilitating preparation. It is expected to better promote the practical application of all-solid-state lithium-sulfur batteries. Attached Figure Description

[0022] Figure 1 P4S 26 @rGO, P4S 32 @rGO, P4S 38 @rGO's long loop performance

[0023] Figure 2 P4S 26 @rGO, P4S 32 @rGO, P4S 38 @rGO's scaling performance

[0024] Figure 3 P4S 32 Long loop performance of / rGO Detailed Implementation

[0025] Example 1:

[0026] S1: 0.4644g P2S5, 0.5891g S, and 0.1g GO were ball-milled and sintered at high temperature to obtain a composite cathode precursor powder. After mixing with 1.1g sulfide electrolyte powder, P4S was obtained. 26 / rGO-LPSCl composite cathode powder.

[0027] S2: Place 0.085g of LPSCl electrolyte powder into a polytetrafluoroethylene mold with a diameter of 10mm, apply a pressure of 100MPa, hold the pressure for 60s, and press it into an electrolyte sheet.

[0028] S3: Then add 0.015g of the composite cathode powder obtained in S1 to one side of the polytetrafluoroethylene mold in S2, apply a pressure of 400MPa, and hold for 180s.

[0029] S4: Attach the lithium metal negative electrode to the other side of the electrolyte sheet, and then place conductive connecting rods on both sides of the positive and negative electrodes of the battery to obtain an all-solid-state lithium-sulfur battery using the P4S26 / rGO-LPSCl composite positive electrode.

[0030] S5: Place the battery obtained in S4 into a stainless steel mold and apply an external pressure of 30MPa to obtain a complete all-solid-state lithium-sulfur battery.

[0031] Example 2:

[0032] S1: 0.3868g P2S5, 0.6746g S, and 0.1g rGO were ball-milled and sintered at high temperature to obtain a composite cathode precursor powder. After mixing with 1.1g sulfide electrolyte powder, P4S was obtained. 32 / rGO-LPSCl composite cathode powder.

[0033] S2: Place 0.085g of LPSCl electrolyte powder into a polytetrafluoroethylene mold with a diameter of 10mm, apply a pressure of 100MPa, hold the pressure for 60s, and press it into an electrolyte sheet.

[0034] S3: Then add 0.015g of the composite cathode powder obtained in S1 to one side of the polytetrafluoroethylene mold in S2, apply a pressure of 400MPa, and hold for 180s.

[0035] S4: Attach the lithium metal negative electrode to the other side of the electrolyte sheet, and then place conductive connecting rods on both sides of the positive and negative electrodes of the battery to obtain P4S. 32 All-solid-state lithium-sulfur battery with / rGO-LPSCl composite cathode.

[0036] S5: Place the battery obtained in S4 into a stainless steel mold and apply an external pressure of 30MPa to obtain a complete all-solid-state lithium-sulfur battery.

[0037] Example 3:

[0038] S1: 0.3313g P2S5, 0.7355g S, and 0.1g rGO were ball-milled and sintered at high temperature to obtain a composite cathode precursor powder. After mixing with 1.1g sulfide electrolyte powder, P4S was obtained. 38 / rGO-LPSCl composite cathode powder.

[0039] S2: Place 0.085g of LPSCl electrolyte powder into a polytetrafluoroethylene mold with a diameter of 10mm, apply a pressure of 100MPa, hold the pressure for 60s, and press it into an electrolyte sheet.

[0040] S3: Then add 0.015g of the composite cathode powder obtained in S1 to one side of the polytetrafluoroethylene mold in S2, apply a pressure of 400MPa, and hold for 180s.

[0041] S4: Attach the lithium metal negative electrode to the other side of the electrolyte sheet, and then place conductive connecting rods on both sides of the positive and negative electrodes of the battery to obtain P4S. 38 All-solid-state lithium-sulfur battery with / rGO-LPSCl composite cathode.

[0042] S5: Place the battery obtained in S4 into a stainless steel mold and apply an external pressure of 30MPa to obtain a complete all-solid-state lithium-sulfur battery.

[0043] Example 4:

[0044] S1: 0.3868g P2S5, 0.6746g S, and 0.1g CNT were ball-milled and sintered at high temperature to obtain a composite cathode precursor powder. After mixing with 1.1g sulfide electrolyte powder, P4S was obtained. 32 / CNT-LPSCl composite cathode powder.

[0045] S2: Place 0.085g of LPSCl electrolyte powder into a polytetrafluoroethylene mold with a diameter of 10mm, apply a pressure of 100MPa, hold the pressure for 60s, and press it into an electrolyte sheet.

[0046] S3: Then add 0.015g of the composite cathode powder obtained in S1 to one side of the polytetrafluoroethylene mold in S2, apply a pressure of 400MPa, and hold for 180s.

[0047] S4: Attach the lithium metal negative electrode to the other side of the electrolyte sheet, and then place conductive connecting rods on both sides of the positive and negative electrodes of the battery to obtain the P4S. 32 All-solid-state lithium-sulfur battery with CNT-LPSCl composite cathode.

[0048] S5: Place the battery obtained in S4 into a stainless steel mold and apply an external pressure of 30MPa to obtain a complete all-solid-state lithium-sulfur battery.

[0049] Example 5:

[0050] S1: 0.3868g P2S5, 0.6746g S, and 0.1g VGCF were ball-milled and sintered at high temperature to obtain a composite cathode precursor powder. After mixing with 1.1g sulfide electrolyte powder, P4S was obtained. 32 / VGCF-LPSCl composite cathode powder.

[0051] S2: Place 0.085g of LPSCl electrolyte powder into a polytetrafluoroethylene mold with a diameter of 10mm, apply a pressure of 100MPa, hold the pressure for 60s, and press it into an electrolyte sheet.

[0052] S3: Then add 0.015g of the composite cathode powder obtained in S1 to one side of the polytetrafluoroethylene mold in S2, apply a pressure of 400MPa, and hold for 180s.

[0053] S4: Attach the lithium metal negative electrode to the other side of the electrolyte sheet, and then place conductive connecting rods on both sides of the positive and negative electrodes of the battery to obtain P4S. 32All-solid-state lithium-sulfur battery with VGCF-LPSCl composite cathode.

[0054] S5: Place the battery obtained in S4 into a stainless steel mold and apply an external pressure of 30MPa to obtain a complete all-solid-state lithium-sulfur battery.

[0055] Example 6:

[0056] S1: 0.3868g P2S5, 0.6746g S, and 0.1g AB were ball-milled and sintered at high temperature to obtain a composite cathode precursor powder. After mixing with 1.1g sulfide electrolyte powder, P4S was obtained. 32 / AB-LPSCl composite cathode powder.

[0057] S2: Place 0.085g of LPSCl electrolyte powder into a polytetrafluoroethylene mold with a diameter of 10mm, apply a pressure of 100MPa, hold the pressure for 60s, and press it into an electrolyte sheet.

[0058] S3: Then add 0.015g of the composite cathode powder obtained in S1 to one side of the polytetrafluoroethylene mold in S2, apply a pressure of 400MPa, and hold for 180s.

[0059] S4: Attach the lithium metal negative electrode to the other side of the electrolyte sheet, and then place conductive connecting rods on both sides of the positive and negative electrodes of the battery to obtain P4S. 32 All-solid-state lithium-sulfur battery with AB-LPSCl composite cathode.

[0060] S5: Place the battery obtained in S4 into a stainless steel mold and apply an external pressure of 30MPa to obtain a complete all-solid-state lithium-sulfur battery.

[0061] Comparing Examples 1, 2, and 3, it can be found that P4S is sintered through solid-state sintering. X After being coated onto rGO, the battery's cycle performance was significantly improved; after 200 stable cycles, the battery still maintained 60% capacity retention; the synthesized P4S X After physical mixing with rGO through simple grinding, the assembled all-solid-state battery exhibited poor cycle reversibility, with a capacity decay rate of 50% after 30 cycles.

Claims

1. A method for preparing an all-solid-state lithium-sulfur battery composite cathode material, characterized in that: The process includes the following steps: Weighing P2S5 and S according to different molar ratios, and preparing P4S. X Precursor powder with X = 10-40, P4S X The precursor powder is mixed with conductive carbon powder to obtain a precursor mixture; the precursor mixture is dry ball milled to obtain precursor powder, which is then sintered at high temperature to obtain composite cathode powder. The composite cathode powder is passed through a 200-mesh sieve, and the powder that passes through the sieve is mixed with sulfide electrolyte that has passed through a 400-mesh sieve and ball milled to obtain the all-solid-state lithium-sulfur battery composite cathode material.

2. The method according to claim 1, characterized in that: The sintering temperature is 250℃-500℃, and the sintering time is 12-24h.

3. The method according to claim 2, characterized in that: The conductive carbon is one or a mixture of several of the following: reduced graphene oxide (rGO), carbon nanotubes (CNT), acetylene black (AB), or vapor-grown carbon nanofibers (VGCF).

4. The method according to claim 3, characterized in that: The P4S X The material is P4S 26 P4S 32 Or P4S 38 .

5. The method according to claim 4, characterized in that: The conductive carbon and P4S X The mixing mass ratio of X = 10 to 40 is (1:9)-(4:6).

6. The method according to claim 5, characterized in that: The ball mill rotates at 200-500 rpm and the milling time is 20-60 min.

7. A method for preparing a solid-state lithium battery, characterized in that: The method includes the following steps: 1) Prepare an all-solid-state lithium-sulfur battery composite cathode material according to the method of claim 1; 2) Weigh a certain mass of sulfide electrolyte powder, place it in a mold, apply a pressure of 100-150 MPa, hold the pressure for 60-90 seconds, and make an electrolyte sheet; 3) Then weigh a certain amount of the positive electrode powder obtained in step 1), place it in the mold in step 2), apply a pressure of 300-450 MPa, hold the pressure for 150-210 s, and form a positive electrode sheet on the surface of the electrolyte sheet. 4) Attach the lithium metal anode sheet to the other side of the sulfide electrolyte sheet, and then place conductive connecting rods on both sides of the positive and negative electrodes of the battery to obtain a complete all-solid-state lithium-sulfur battery.

8. The method according to claim 7, characterized in that: The thickness of the electrolyte sheet is between 450-600 μm.

9. The method according to claim 8, characterized in that: The sulfide electrolytic powder is obtained by ball milling and mixing Li2S, P2S5, and LiCl in a certain proportion, sintering at 460℃, and then passing it through a 400-mesh sieve.

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