A Te- and Ru-codoped FeS2 material, its preparation method and application

Abstract

The present invention relates to the field of new energy technologies, and discloses a Te- and Ru-codoped FeS2 material, a preparation method thereof, and an application thereof. The preparation method of the Te- and Ru-codoped FeS2 material comprises the following steps: S1, premixing ferrous sulfide powder and tellurium ruthenium powder under an inert gas to obtain a premix; the molar ratio of the ferrous sulfide powder to the tellurium ruthenium powder is 1-1.8:1; the tellurium ruthenium powder is a mixed powder of tellurium powder and ruthenium powder; S2, ball-milling the premix; S3, calcining the ball-milled material, and cooling the calcined product to ambient temperature to obtain the Te- and Ru-codoped FeS2 material. Mixing the Te- and Ru-codoped FeS2 material and a sulfide electrolyte in proportion and rolling and grinding; then further adding conductive carbon and ball-milling, and the obtained Te- and Ru-codoped FeS2 composite cathode has a high specific capacity, excellent cycle stability and rate performance, and can effectively improve the performance of all-solid-state batteries.

Description

Technical Field

[0001] The present invention relates to the field of new energy technologies, and particularly to a Te- and Ru-codoped FeS2 material, a preparation method thereof, and applications thereof. Background Art

[0002] The replacement of liquid batteries by all-solid-state batteries is a major technological revolution. Compared with liquid batteries, all-solid-state batteries have higher energy density, a safer working environment, and broader application prospects.

[0003] The emergence of secondary rechargeable batteries has solved the problems of non-reusable resources and short service life of primary batteries. All-solid-state lithium metal batteries are currently mature energy batteries with established commercial layouts. Many researchers are committed to improving the energy density of batteries to match the current booming new energy power equipment. The most direct route is to select and modify the cathode to improve the energy density and cycle life of the battery. FeS2 primary batteries have long been commercialized, but they violate the concepts of resource utilization and sustainable development. Their irreversibility and insecurity have lost people's attention. However, as a cathode material, it has a higher theoretical specific capacity (894 mAh g 1 / 3 O2 (denoted as NMC) (<280 mAh g -1 ) than the mainstream Li(NiMnCo) -1 ). However, in liquid batteries, it is often affected by limited reversibility due to slow kinetics, harmful volume changes, and the insulating properties of reaction products. Similar to lithium-sulfur batteries, harmful dissolution of polysulfides may occur in lithium iron disulfide batteries, and a potential mitigation strategy may be used in solid-state batteries. In addition, as an active substance in the battery, during the redox reaction process, the rearrangement of the crystal structure caused by the thermal instability of Fe and the conversion to polysulfides caused by S together increase the volume expansion problem of the original molecule. This problem can be fundamentally alleviated by means of elemental doping substitution. Therefore, how to improve the insulating reaction products, lattice structure instability, interface contact problems caused by volume expansion, and slow reaction kinetics is a meaningful topic. Summary of the Invention

[0004] In view of this, the present invention provides a Te- and Ru-codoped FeS2 material, a preparation method thereof, and applications thereof. The problems in terms of conductivity, volume expansion, structural stability, energy density, and electrochemical conversion efficiency are improved and enhanced.

[0005] Te and S are in the same main group and have similar properties to S. However, as a semiconductor, Te has a higher conductivity than S (10 -7 S / m vs 10 -20S / m), and its conductivity can be further improved by doping or alloying. In addition, Te has a high valence state (such as Te 6+ ), doping in the cathode material helps to increase the redox potential of the material, which in turn helps to increase the energy density of the battery. And Te can form an ordered Te-Fe-Te structure with Fe, forming a finer structure, which can stabilize the crystal structure and slow down the grain pulverization problem caused by the crystal structure strain of FeS2. Moreover, Te has a relatively large size, which enables it to provide a larger layer spacing when forming a layered structure material (such as FeTe), facilitating the diffusion and transport of ions or molecules, and thus improving the reaction kinetics. Ruthenium (Ru) and iron (Fe) are both metal elements with excellent electrical conductivity. However, due to their different electronic structures and physical properties, Ru exhibits excellent electrocatalytic activity and thermal stability, showing the function of improving the charge-discharge efficiency and cycle stability of the battery in both fuel cells and lithium-oxygen batteries.

[0006] The present invention provides a method for preparing a Te and Ru co-doped FeS2 material, comprising the following steps:

[0007] S1. Premix ferrous sulfide powder (FeS2) and tellurium ruthenium powder (Te&Ru) in an inert gas environment to obtain a premix, ensuring sufficient mixing of the two powders; the molar ratio of ferrous sulfide powder (FeS2) to tellurium ruthenium powder (Te&Ru) is 1 - 1.8:1; the tellurium ruthenium powder (Te&Ru) is a mixed powder of tellurium powder and ruthenium powder;

[0008] S2. Ball mill the premix;

[0009] S3. Calcinate the material after ball milling, and cool the calcined product to ambient temperature to obtain the Te-doped FeS2 material.

[0010] In step S1, in the tellurium ruthenium powder (Te&Ru), the molar ratio of tellurium powder to ruthenium powder is 1:2 - 2:1.

[0011] Preferably, in step S1, the molar ratio of the ferrous sulfide powder (FeS2) to the tellurium ruthenium powder (Te&Ru) is 1 - 1.5:1.

[0012] More preferably, in step S1, the molar ratio of the ferrous sulfide powder (FeS2) to the tellurium ruthenium powder (Te&Ru) is 1:1.

[0013] In step S1, the premixing is carried out by grinding with a mortar.

[0014] In step S2, mechanical ball milling is carried out using a planetary ball mill; the ball-to-material ratio is 3 - 5:1, and the ball milling conditions are: 350 - 450 rpm, and the ball milling time is 18 - 24 h. The ball milling medium is zirconia ball milling beads with a particle size of 3 - 5 mm.

[0015] In step S3, the calcination is carried out in a tube furnace.

[0016] In step S3, the calcination temperature is 800 °C to 950 °C, and the calcination time is 10 hours to 12 hours.

[0017] <Second aspect>

[0018] The present invention also provides a Te and Ru co-doped FeS2 material prepared by the preparation method as described above.

[0019] <Third aspect>

[0020] A preparation method of a Te and Ru co-doped FeS2 composite cathode material, comprising the following steps:

[0021] Step 1: Under a protective atmosphere, the Te and Ru co-doped FeS2 material as described above is mixed with a sulfide electrolyte in proportion and subjected to rolling milling;

[0022] Step 2: Conductive carbon is further added to the material in step 1 for ball milling to obtain the Te and Ru co-doped FeS2 composite cathode material.

[0023] In step 1, the rolling milling conditions are: the ball-to-material ratio is 2:1 - 5:1; the rotation speed is 200 - 500 rpm; the rolling milling method is intermittent rolling milling, and it stops for 5 - 10 min every 0.5 - 1 h of milling; a total of 8 - 10 times.

[0024] In step 2, the ball milling conditions are: the ball-to-material ratio is 2:1 - 5:1; the rotation speed is 300 - 500 rpm; the ball milling method is intermittent ball milling; it stops for 5 - 10 min every 0.5 - 1 h of ball milling; a total of 10 - 20 times.

[0025] The mass ratio of the Ru and Te co-doped FeS2 material, the sulfide electrolyte, and the conductive carbon is: 40~50:40~50:10~20.

[0026] The sulfide electrolyte includes Li 5.5 PS 4.5 X 1.5 、Li 10 MP2S 12 、at least one or more of 80 Li2S·20P2S5; wherein, M is selected from at least one of Ge, Si, or Sn; X is selected from at least one of F, Cl, Br, or I.

[0027] The conductive carbon is at least one of carbon nanofiber (VGCF) - coated carbon, carbon black, conductive graphite, and carbon nanotubes.

[0028] As an embodiment of the present invention, the preparation method of the Te and Ru co - doped FeS2 composite cathode material includes the following steps:

[0029] Step 1: Under a protective atmosphere, mix the Te and Ru co - doped FeS2 material and the sulfide electrolyte in a mass ratio of 40 - 50:40 - 50, and then perform ball milling for 4 - 10 h at a ball - to - material ratio of 2:1 - 5:1 and a rotation speed of 200 - 300 rpm; after the ball milling is completed, separate the balls from the material.

[0030] Step 2: Continuously add VGCF to the material after removing the abrasive in Step 1, and perform ball milling for 4 - 10 h at a ball - to - material ratio of 2:1 - 5:1 and a rotation speed of 300 - 500 rpm to obtain the Te and Ru co - doped FeS2 composite cathode material.

[0031] The protective gas is argon.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] 1. The present invention provides a modification method for multi - element co - doped active substances. By co - doping Te and Ru, the high conductivity and high valence state of Te are combined with the excellent electro - chemical catalytic activity and thermal stability advantages of Ru, comprehensively improving the energy density, charge - discharge efficiency, and cycle stability of FeS2. It inhibits the undesired volume expansion.

[0034] 2. The present invention provides a Te and Ru co - doped FeS2 material applied to sulfide - based all - solid - state lithium batteries. By adopting a doping method combining ball milling and calcination, it has the following enhancement effects: By using a simple ball - milling method, the particles of FeS2, Te, and Ru can be evenly distributed. The high - energy ball - milling method causes atomic rearrangement and exchange between crystals. Combining with the calcination method, the doped atoms can be incorporated by infiltration, ensuring the uniformity and stability of the new crystal size and structure while removing the un - successfully doped Te and Ru single elements. Through comparative research, it is found that in the case of single - mode doping, there will be crystal agglomeration, uneven size, and the existence of single - element Te and Ru in the product.

[0035] 3. The present invention also provides a Te- and Ru-codoped FeS2 composite cathode material, which is mechanically ball-milled from Te- and Ru-codoped FeS2 material, sulfide electrolyte, and conductive carbon. The addition of conductive carbon can improve the electronic conductivity of the composite material; the addition of sulfide electrolyte can provide particle-to-particle contact and improve the ion transport from the inside of the composite cathode to the cathode / electrolyte interface; the composite cathode prepared by the method of the present invention has a capacity of 508 mAh g after 588 cycles -1 and a super cycle stability with a capacity retention rate of 91%, and the rate performance is also improved.

[0036] 4. When preparing the Te- and Ru-codoped FeS2 composite cathode material, a combination of ball milling and rolling milling is adopted. The rolling milling method can ensure that FeS2 and sulfide electrolyte are in maximum contact with the ball milling medium (ball milling beads), improving the mixing efficiency and scale of the two. Ball milling can effectively provide high-energy impacts to break the gradient distribution of the components caused by the physical aggregation of the three components. This rolling milling method may result in the uneven distribution of conductive carbon inside and outside. The combination of the two can make the conductive carbon fully distributed inside and outside the composite material. Generally speaking, the pre-mixing and then mixing with conductive carbon are more sufficient, which is conducive to the uniform distribution of electrolyte and conductive carbon in the active material, ensuring the effective transport of ions and electrons inside the composite cathode. At the same time, the step-by-step mixing provides an opportunity to controllably monitor the particle size change and mixing degree, facilitating the full-process evaluation and design of the composite cathode. In the process of large-scale production practice, the output of the materials obtained in different ball milling stages can be efficiently controlled, improving the production efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Other features, objects, and advantages of the present invention will become more apparent by reading the detailed description of the non-limiting embodiments with reference to the following drawings:

[0038] Figure 1 is the SEM image of the FeRu 0.5 S2Te 0.5 material prepared in Preparation Example 1;

[0039] Figure 2 is the SEM image of the FeRu 0.5 S2Te 0.5 material prepared in Comparative Preparation Example 1;

[0040] Figure 3 is the XRD pattern of FeRu 0.5 S2Te 0.5 obtained in Preparation Example 1;

[0041] Figure 4 is the Raman spectrum of FeRu 0.5 S2Te 0.5 obtained in Preparation Example 1;

[0042] Figure 5 It is the comparison curve graph of the rate performance between Example 1 and Comparative Example 1;

[0043] Figure 6 It is the first charge-discharge curve graph of Example 1 and Comparative Example 2;

[0044] Figure 7 It is the comparison curve graph of the long cycle performance of the composite positive electrodes of Example 1 and Comparative Examples 3, 6, 7, and 8 with different doping amounts and different ball milling preparation methods;

[0045] Figure 8 It is the comparison curve graph of the long cycle performance of Example 1 and Comparative Examples 4 and 5;

[0046] Figure 9 It is the first charge-discharge curve graph of Examples 1-3;

[0047] Figure 10 It is the first charge-discharge curve graph of Comparative Example 2 and Comparative Example 4. Detailed implementation manners

[0048] The present invention will be described in detail below in conjunction with the embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but do not limit the present invention in any form. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several adjustments and improvements can still be made. These all belong to the protection scope of the present invention.

[0049] In the following examples and comparative examples:

[0050] The conductive agent used is VGCF; the protective gas is argon.

[0051] Preparation Example 1

[0052] FeRu 0.5 S2Te 0.5 Preparation of materials

[0053] 1. In a glove box, mix ferrous sulfide powder (FeS2) and ruthenium telluride powder (Te&Ru) in a molar ratio of 1:(0.5:0.5). Use a mortar and pestle to premix and grind the mixed powder for 30 minutes to ensure that the two powders are fully mixed;

[0054] Among them, the ruthenium telluride powder (Te&Ru) is a mixed powder of tellurium powder and ruthenium powder in a molar ratio of 1:1; the molar ratio of ferrous sulfide powder (FeS2) and ruthenium telluride powder (Te&Ru) is 1:1.

[0055] 2. The premixed powder is transferred to a zirconia ball milling jar, and a certain amount of zirconia ball milling beads are added. Mechanical ball milling is carried out using a planetary ball mill, with a ball-to-material ratio of 5:1, a ball milling speed of 450 rpm, and a ball milling time of 18 hours.

[0056] 3. After ball milling is completed, the ball milling beads and the material are separated, and then the material is placed in a sealed container for calcination. The calcination is carried out in a tube furnace, with the temperature controlled at 900 °C and the calcination time of 11 hours. After the calcination is completed, the mixture is allowed to cool naturally to room temperature to complete the entire preparation process.

[0057] Figure 1 For the FeRu 0.5 S2Te 0.5 prepared in Preparation Example 1; this figure shows FeRu 0.5 S2Te 0.5 The particles are evenly distributed, and the crystal particle size is small and uniform, indicating that pre-grinding and ball milling have a positive effect on the size distribution of the material and the particle size.

[0058] Figure 3 For the FeRu 0.5 S2Te 0.5 obtained in Preparation Example 1; this figure shows the obtained FeRu 0.5 S2Te 0.5 There is no presence of Te and Ru elemental substances in the substance, and the synthesized material has a high purity. Judging from the sharpness of the peaks, the crystallinity of the substance is good.

[0059] Figure 4 For the FeRu 0.5 S2Te 0.5 obtained in Preparation Example 1; this figure can illustrate that the target chemical bond exists in the prepared substance and there are no impurity peaks.

[0060] Comparative Preparation Example 1

[0061] The difference between this Comparative Preparation Example and Preparation Example 1 is that: there is no ball milling process. After grinding for 30 minutes, the calcination step is directly carried out.

[0062] Figure 2 For the FeRu 0.5 S2Te 0.5 prepared in Comparative Preparation Example 1; this figure shows FeRu 0.5 S2Te 0.5 The particles show a large degree of aggregation, and the particle size distribution is dispersed, indicating that the precursor raw materials are not fully mixed, resulting in an unsatisfactory crystal formation process.

[0063] Comparative Preparation Example 2

[0064] The difference between this comparative preparation example and Preparation Example 1 is that the molar ratio of iron disulfide powder (FeS2) to tellurium ruthenium powder (Te&Ru) is 2:(0.5:0.5). The remaining steps are the same, and FeRu is obtained. 0.25 S2Te 0.25 .

[0065] Comparative Preparation Example 3

[0066] The difference between this comparative preparation example and Preparation Example 1 is that in Step 1, tellurium ruthenium powder (Te&Ru) is replaced with single ruthenium powder, and the molar ratio of iron disulfide powder (FeS2) to ruthenium powder (Ru) is 1:1. The remaining steps are the same, and FeRuS2 is obtained.

[0067] Comparative Preparation Example 4

[0068] The difference between this comparative preparation example and Preparation Example 1 is that in Step 1, tellurium ruthenium powder (Te&Ru) is replaced with ruthenium dioxide, and the remaining steps are the same, and FeS2·RuO2 is obtained.

[0069] Example 1 FeRu for sulfide-based all-solid-state lithium batteries 0.5 S2Te 0.5 Preparation of composite cathode material

[0070] Step 1: Weigh zirconia beads in a zirconia ball mill according to a ball-to-material ratio of 3:1, dry them in an oven at 60 °C for four hours, and then transfer them to an argon glove box (the water content of the argon in the glove box is less than 1 ppm, and the oxygen content is less than 1 ppm); put 400 mg of Fe 0.5 Ru 0.5 STe (prepared in Preparation Example 1) and 400 mg of Li 5.5 PS 4.5 Cl 1.5 into the ball mill, seal it with insulating tape; perform intermittent ball milling at a rotation speed of 200 rpm (ball milling for 1 h; stopping for 10 min; a total of 8 times); after ball milling is completed, transfer the ball mill to the glove box and perform ball-material separation;

[0071] Step 2: Add 200 mg of VGCF to the material separated in Step 1 in a mortar for premixing, and then transfer it to the ball mill. Perform intermittent ball milling according to a ball (zirconia bead)-to-material ratio of 5:1 at a rotation speed of 450 rpm (where the intermittent ball milling method is: ball milling for 30 min; stopping for 5 min, a total of 20 times). After ball milling is completed, perform ball-material separation to obtain FeRu 0.5 S2Te 0.5 composite cathode.

[0072] Example 2

[0073] Step 1: Weigh zirconia beads into a zirconia ball mill according to a ball-to-material ratio of 3:1. After drying in an oven at 60 °C for four hours, transfer them to an argon glove box (the water content of argon in the glove box is less than 1 ppm, and the oxygen content is less than 1 ppm). Place 400 mg of Fe 0.5 Ru 0.5 STe (prepared in Preparation Example 1) and 400 mg of Li 10 GeP2S 12 into the ball mill, and seal it with insulating tape. Carry out intermittent rolling milling at a rotational speed of 200 rpm (rolling milling for 30 min; stopping for 5 min; a total of 20 times). After the rolling milling is completed, transfer the ball mill to the glove box and perform ball-material separation;

[0074] Step 2: Add 200 mg of VGCF to the material separated in Step 1 in a mortar for premixing, and then transfer it to the ball mill. Carry out intermittent ball milling according to a ball (zirconia bead)-to-material ratio of 5:1 at a rotational speed of 450 rpm (where the intermittent ball milling method is: ball milling for 30 min; stopping for 5 min, a total of 20 times). After the ball milling is completed, perform ball-material separation to obtain FeRu 0.5 S2Te 0.5 composite cathode.

[0075] Example 3

[0076] Step 1: Weigh zirconia beads into a zirconia ball mill according to a ball-to-material ratio of 3:1. After drying in an oven at 60 °C for four hours, transfer them to an argon glove box (the water content of argon in the glove box is less than 1 ppm, and the oxygen content is less than 1 ppm). Place 400 mg of Fe 0.5 Ru 0.5 STe (prepared in Preparation Example 1) and 400 mg of 80Li2S·20P2S5 into the ball mill, and seal it with insulating tape. Carry out intermittent rolling milling at a rotational speed of 200 rpm (where the intermittent ball milling method is: rolling milling for 30 min; stopping for 5 min, a total of 20 times). After the rolling milling is completed, transfer the ball mill to the glove box and perform ball-material separation;

[0077] Step 2: Add 200 mg of VGCF to the material separated in Step 1 in a mortar for premixing, and then transfer it to the ball mill. Carry out intermittent ball milling according to a ball (zirconia bead)-to-material ratio of 5:1 at a rotational speed of 450 rpm (where the intermittent ball milling method is: ball milling for 30 min; stopping for 5 min, a total of 20 times). After the ball milling is completed, perform ball-material separation to obtain FeRu 0.5 S2Te 0.5 composite cathode.

[0078] Comparative Example 1

[0079] The difference between this comparative example and Example 1 is that in Step 1, FeRu 0.5S2Te 0.5 Replace it with FeRu prepared in Comparative Preparation Example 1 0.5 S2Te 0.5 .

[0080] Comparative Example 2

[0081] The difference between this comparative example and Example 1 is that: in Step 1, FeRu 0.5 S2Te 0.5 is replaced with commercial micron FeS2 (Iron disulfide|1309-36-0|Adamas|99.99%|RG|), and the rest of the operating steps are the same.

[0082] Other steps are the same as those in Example 1.

[0083] Comparative Example 3

[0084] The difference between this comparative example and Example 1 is that: in Step 1, FeRu 0.5 S2Te 0.5 is replaced with FeRu prepared in Comparative Preparation Example 2 0.25 S2Te 0.25 .

[0085] Other steps are the same as those in Example 1.

[0086] Comparative Example 4

[0087] The difference between this comparative example and Example 1 is that: in Step 1, FeRu 0.5 S2Te 0.5 is replaced with FeRuS2 prepared in Comparative Preparation Example 3.

[0088] Other steps are the same as those in Example 1.

[0089] Comparative Example 5

[0090] The difference between this comparative example and Example 1 is that: in Step 1, FeRu 0.5 S2Te 0.5 is replaced with FeS2·RuO2 prepared in Comparative Preparation Example 4.

[0091] Comparative Example 6

[0092] The difference between this comparative example and Example 1 is that: FeRu 0.5 S2Te 0.5 , Li 5.5 PS 4.5 Cl 1.5、 are mixed simultaneously and milled once.

[0093] Weigh zirconia beads into a zirconia ball mill tank according to a ball-to-material ratio of 3:1, dry them in an oven at 60 °C for four hours, and then transfer them to an argon glove box (the water content of the argon in the glove box is less than 1 ppm, and the oxygen content is less than 1 ppm); add 400 mg of FeRu 0.5 S2Te 0.5 (prepared in Preparation Example 1), 400 mg of Li 5.5 PS 4.5 Cl 1.5 and 200 mg of VGCF into the ball mill tank, and seal it with insulating tape; perform intermittent rolling milling at a speed of 200 rpm for 9 h 20 min (where the intermittent ball milling method is: roll mill for 30 min; stop for 5 min); after the rolling milling is completed, transfer the ball mill tank to the glove box and perform ball-material separation to obtain FeRu 0.5 S2Te 0.5 composite cathode.

[0094] Comparative Example 7

[0095] The difference between this comparative example and Example 1 is that: FeRu 0.5 S2Te 0.5 , Li 5.5 PS 4.5 Cl 1.5 and VGCF are mixed simultaneously and ball milled once.

[0096] Weigh zirconia beads into a zirconia ball mill tank according to a ball-to-material ratio of 5:1, dry them in an oven at 60 °C for four hours, and then transfer them to an argon glove box (the water content of the argon in the glove box is less than 1 ppm, and the oxygen content is less than 1 ppm); add 400 mg of FeRu 0.5 S2Te 0.5 (prepared in Preparation Example 1), 400 mg of Li 5.5 PS 4.5 Cl 1.5 and 200 mg of VGCF into the ball mill tank, and seal it with insulating tape; perform intermittent ball milling at a speed of 450 rpm for 9 h 20 min (where the intermittent ball milling method is: ball mill for 30 min; stop for 5 min); after the ball milling is completed, transfer the ball mill tank to the glove box and perform ball-material separation to obtain FeRu0.5S2Te0.5.

[0097] Comparative Example 8

[0098] The difference between this comparative example and Example 1 is that: in Steps 1 and 2, the mixing method adopts a continuous rolling milling / ball milling method, that is, continuous rolling milling / ball milling for 8 hours.

[0099] Application Performance Test:

[0100] Test method: In an argon glove box, 10 mg of the composite cathode and 100 mg of the electrolyte (Li 5.5 PS 4.5 Cl 1.5 ) prepared in Example 1 and Comparative Examples 1-6 were pressed into tablets in a pressure mold and assembled into a full cell with a lithium-indium alloy anode. The charge and discharge rates tested were 0.025 C - 1 C, and the charge and discharge cut-off voltages were 0.38 V to 2.38 V / 0.1 to 3 relative to LiIn / Li + . The charge and discharge capacities described in the present invention both refer to the specific capacity calculated based on the composite active material with a positive electrode of FeRu 0.5 S2Te 0.5 / FeS2 / FeRuS2 / FeS2·RuO2 / FeRu 0.25 S2Te 0.25 -based composite active material.

[0101] Figure 5 is a comparative curve graph of the rate performance of Example 1 and Comparative Example 1; this graph clearly shows that the composite cathode of Example 1 exhibits advantages in terms of capacity and rate compared to Comparative Example 1. The main reason is attributed to the differences in the crystallinity and crystal particle distribution of the FeRu 0.5 S2Te 0.5 material. Smaller-sized crystals can better contact the components of the composite cathode, and a more uniform particle distribution can alleviate the instability of the crystal phase. Therefore, the former can release more energy and have better stability at higher rates.

[0102] Figure 6 is the first-cycle charge and discharge curve graph of Example 1 and Comparative Example 2; it can be seen from this graph that FeRu 0.5 S2Te 0.5 has a wider electrochemical window. Therefore, in the voltage window of 0.1 - 3 V, it can have a higher first-cycle discharge capacity than FeS2 (0.38 - 2.38 V).

[0103] Figure 7 is a comparative curve graph of the long-cycle performance of the composite cathode materials of Example 1 and Comparative Examples 3, 6, 7, and 8 with different doping amounts and different ball-milling preparation methods. This graph shows that the co-doping modification of Te and Ru elements and the preparation method of the composite cathode also directly and indirectly affect the overall stability of the composite cathode.

[0104] Figure 8It is the comparative curve graph of the long cycle performance of Example 1, Comparative Example 4 and Comparative Example 5. It can be seen from this graph that the doping of Te and Ru elements does not affect the crystal structure, and thus the capacity of the active material can be maximally exerted. However, the doping of single ruthenium element and ruthenium oxide has the situations of damaging the FeS2 matrix structure and being unable to be doped, resulting in impaired capacity. At the same time, from the comparative curve graph of the long cycle performance of Comparative Example 4 and Comparative Example 5, it can be indirectly reflected that the doping effect of single element is better than that of its oxide doping.

[0105] Figure 9 It is the first charge-discharge curve graph of Examples 1-3. It can be seen that the modified cathode has the characteristic of being compatible with the sulfide solid electrolyte, and the three electrolytes exhibit almost equally excellent transport effects in the composite cathode to ensure the maximum realization of capacity.

[0106] Figure 10 It is the first charge-discharge curve graph of Comparative Example 2 and Comparative Example 4. It can be seen that introducing Ru element doping into FeS2 can achieve the above-mentioned function of Ru in catalyzing the electrochemical oxidation-reduction reaction, and thus improve the charge-discharge efficiency of the battery (discharge specific capacity / charge specific capacity). It can be seen from the graph that the charge-discharge efficiency of FeRuS2 is much higher than that of FeS2.

[0107] The specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art can make various deformations or modifications within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A method for preparing a Te and Ru co-doped FeS2 composite positive electrode material for a sulfide-based all-solid-state lithium battery, characterized in that: The steps include: Step 1: Under a protective atmosphere, the Te and Ru co-doped FeS2 material is mixed with a sulfide electrolyte in proportion and rolled; Step 2: Continue to add conductive carbon to the material of step 1 and further ball mill to obtain the Te and Ru co-doped FeS2 composite positive electrode material; In step 1, the grinding conditions are as follows: ball-to-material ratio 2:1-5:1; rotation speed 200-500rpm; the grinding method is intermittent grinding, grinding for 1-2h and stopping for 5-10min; a total of 8-10 times of grinding; In step 2, the ball milling conditions are: ball-to-material ratio 2:1-5:1; rotation speed 300-500rpm; intermittent ball milling; each ball milling lasts 30-60min, and stops for 5-10min; a total of 10-20h; The preparation method of the Te and Ru co-doped FeS2 material comprises the following steps: S1. Premixing ferrous sulfide powder and tellurium ruthenium powder under inert gas to obtain a premix; the molar ratio of the ferrous sulfide powder to the tellurium ruthenium powder is 1-1.8:1; the tellurium ruthenium powder is a mixed powder of tellurium powder and ruthenium powder; in the tellurium ruthenium powder, the molar ratio of tellurium powder to ruthenium powder is 1:2-2:1; S2, ball milling the premix; mechanical ball milling is performed using a planetary ball mill; the ball-to-material ratio is 3-5:1, the ball milling conditions are: 350-450rpm, and the ball milling time is 18-24h; S3, calcining the ball-milled material, and cooling the calcined product to ambient temperature to obtain the Te and Ru co-doped FeS2 material; In step S3, the calcination temperature is 800° C. to 950° C., and the calcination time is 10 hours to 12 hours.

2. The method for preparing the Te and Ru co-doped FeS2 composite positive electrode material according to claim 1, characterized in that: The mass ratio of the Te and Ru co-doped FeS2 material, sulfide electrolyte, and conductive carbon is 40~50:40~50:10~20.

3. A Te and Ru co-doped FeS2 composite positive electrode material prepared by the preparation method as claimed in claim 1 or 2.

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