A positive electrode material, a preparation method and application thereof

Abstract

The application discloses a positive electrode material, which comprises a lithium iron phosphate base doped with rhodium and a first coating layer comprising indium tin oxide coated on at least part of the surface of the lithium iron phosphate base. The positive electrode material can improve the electrochemical performance of LFP at low temperature, and improve the low-temperature cycle stability and capacity retention rate of the battery.

Description

Technical Field

[0001] This application relates to the field of lithium-ion battery technology, and in particular to a cathode material, its preparation and application. Background Technology

[0002] Currently, lithium-ion batteries play a crucial role in portable electronics, transportation, and large-scale energy storage due to their advantages such as high energy density, high power density, and long lifespan, especially in the electric vehicle sector. However, the application of lithium-ion batteries in transportation and large-scale energy storage has brought both development opportunities and new challenges. In addition to energy density, power density, fast charging capability, lifespan, and safety, there are also urgent requirements regarding the operating temperature of lithium-ion batteries.

[0003] Lithium-ion batteries have low ionic and electronic conductivity, and their electrochemical performance deteriorates significantly, especially at low temperatures, resulting in significant energy and power losses, charging difficulties, reduced lifespan, and safety issues. This has become one of the biggest challenges facing lithium-ion batteries. Specifically, this manifests in the following aspects: (1) Capacity reduction: At -20°C, traditional lithium batteries with LiFePO4 as the cathode only provide 40% to 60% of their room temperature capacity; (2) Capacity degradation: Traditional lithium batteries with LiFePO4 as the cathode experience rapid capacity degradation at low temperatures; (3) Safety issues: Low-temperature charging affects the LiFePO4 cathode capacity. + The diffusion kinetics of Li lead to + Lithium iron phosphate (LFP) batteries cannot fully insert into the graphite anode and form dendrites. As these lithium dendrites grow, they can pierce the separator between electrodes, causing internal short circuits. The poor low-temperature performance of LFP batteries is a bottleneck limiting their application in cold environments. In cold regions, the reduced driving range of new energy vehicles, causing user anxiety, is a major factor affecting the purchase of new energy vehicles in these areas. Furthermore, relevant departments have set technical requirements for the low-temperature range degradation of new energy vehicles, requiring the degradation rate to not exceed 35%. Therefore, improving the performance of LFP batteries at low temperatures is of great significance.

[0004] For methods to improve low-temperature performance, the first approach is to nanoscale the particles to enhance their kinetics. However, excessively small particle sizes can lead to large specific surface areas, making processing difficult and exacerbating interfacial side reactions. The second approach is to carbon-coat the LFP surface to improve conductivity, thereby increasing conductivity at low temperatures. However, this does not improve intrinsic ion diffusion. The third approach may involve doping with some metallic substances to improve the stability of the crystal lattice and thus increase conductivity. This only partially improves conductivity, resulting in limited improvement in low-temperature capacity. Overall, the improvement in low-temperature performance is not significant and is not conducive to industrial production.

[0005] Other improvement solutions include placing a layer of insulation cotton on the outside of the battery cell or using other structural methods to reduce heat loss. However, heating cotton takes too long to heat up, has limited effectiveness, and is also costly. Alternatively, one could improve the electrolyte by developing one with high conductivity and low viscosity at low temperatures. However, the electrolyte composition is complex and requires adaptation to specific systems, resulting in poor versatility and limited research findings.

[0006] The bottleneck in low-temperature kinetics lies in the significant increase in charge transfer impedance at low temperatures, and the modification methods are relatively limited. Therefore, developing low-temperature lithium iron phosphate composite interface layers can help reduce interface impedance and break through the traditional single modification strategy. Developing low-temperature lithium iron phosphate materials is therefore necessary. Summary of the Invention The purpose of this invention is to provide a cathode material, its preparation and application, which can improve the electrochemical performance of LFP at low temperatures and enhance the low-temperature cycle stability and capacity retention of the battery.

[0007] To achieve the objectives of this invention, the following technical solution is adopted: On one hand, the present invention provides a positive electrode material, the positive electrode material comprising: A lithium iron phosphate matrix, wherein the lithium iron phosphate matrix is ​​doped with rhodium; and A first coating layer comprising indium tin oxide and covering at least a portion of the surface of the lithium iron phosphate substrate.

[0008] In an embodiment of the present invention, the rhodium concentration in the lithium iron phosphate matrix is ​​0.5 to 5 wt%.

[0009] In an embodiment of the present invention, the average particle size Dv50 of the lithium iron phosphate matrix is ​​0.8~1.2μm.

[0010] In an embodiment of the present invention, the molar ratio of indium oxide to tin oxide in the indium tin oxide is 7-9:1.

[0011] In an embodiment of the present invention, the thickness of the first coating layer is 10~30nm.

[0012] In an embodiment of the present invention, the positive electrode material further includes: a second coating layer, the second coating layer comprising a doped conductive polymer composite material and coating at least a portion of the surface of the first coating layer.

[0013] In an embodiment of the present invention, the conductive polymer material in the doped conductive polymer material composite includes at least one of polyaniline, polypyrrole, and polyvinyldioxythiophene.

[0014] In an embodiment of the present invention, the dopant in the doped conductive polymer composite includes at least one of camphor sulfonic acid, dodecyl sulfonic acid, dodecylbenzene sulfonic acid, toluene sulfonic acid, p-toluene sulfonic acid, and naphthalene sulfonic acid.

[0015] In an embodiment of the present invention, the doped conductive polymer composite is a camphor sulfonic acid-doped polyaniline composite; wherein, the molar ratio of a single repeating unit of the polyaniline to the camphor sulfonic acid is 1.5~2.5:1.

[0016] In an embodiment of the present invention, the thickness of the second coating layer is 20-40 nm.

[0017] On the other hand, the present invention also provides a method for preparing a positive electrode material, which includes the following steps: S1. The lithium iron phosphate precursor is ball-milled and mixed with a lithium source and a rhodium source, and then spray-granulated to form a spherical precursor; the spherical precursor is sintered and crushed to obtain a rhodium-doped lithium iron phosphate matrix; S2. Mix the indium source, tin source, and lithium iron phosphate matrix, add a precipitant dropwise, and perform a hydrothermal reaction to make In³ + and Sn 4+ The material is co-precipitated and adsorbed on the surface of the lithium iron phosphate matrix, and then dried and annealed to obtain a cathode material with a first coating layer. S3. The conductive polymer monomer and dopant are mixed with the cathode material having the first coating layer, and an in-situ polymerization reaction is carried out under the action of an initiator to obtain a cathode material with a double coating layer.

[0018] In an embodiment of the present invention, in step S1, the lithium source includes at least one of lithium carbonate, lithium dihydrogen phosphate, lithium hydroxide, lithium chloride, and lithium nitrate.

[0019] In embodiments of the present invention, the rhodium source includes at least one of rhodium chloride, rhodium nitrate, and rhodium acetylacetonate.

[0020] In an embodiment of the present invention, the molar ratio of the lithium source to the rhodium source is 1:0.045~0.5.

[0021] In this embodiment of the invention, the sintering is a two-stage sintering process carried out in a weakly reducing atmosphere; wherein, the first stage of sintering refers to holding at 300~500℃ for 2~4h; and the second stage of sintering refers to holding at 600~800℃ for 6~10h.

[0022] In an embodiment of the present invention, in step S2, the indium source includes at least one of indium nitrate, indium chloride, and indium hydroxide.

[0023] In embodiments of the present invention, the tin source includes at least one of tin tetrachloride, tin nitrate, and tin oxide.

[0024] In an embodiment of the present invention, the molar ratio of the indium source to the tin source is 7~9:1~3.

[0025] In embodiments of the present invention, the precipitant includes at least one of ammonia, urea, ammonium bicarbonate, and potassium hydroxide.

[0026] In this embodiment of the invention, the hydrothermal reaction refers to a reaction at 100~140℃ for 6~10 hours.

[0027] In this embodiment of the invention, the annealing treatment refers to holding at 400~600℃ for 2-4 hours.

[0028] In an embodiment of the present invention, in step S3, the initiator includes at least one of ammonium persulfate, potassium persulfate, ferric chloride, and potassium dichromate.

[0029] In an embodiment of the present invention, the conductive polymer monomer includes at least one of aniline, pyrrole, and 3,4-ethylenedioxythiophene.

[0030] In embodiments of the present invention, the dopant includes at least one of camphor sulfonic acid, dodecyl sulfonic acid, dodecylbenzene sulfonic acid, toluene sulfonic acid, p-toluene sulfonic acid, and naphthalene sulfonic acid.

[0031] In an embodiment of the present invention, the molar ratio of the conductive polymer monomer to the dopant is 1.5 to 2.5:1.

[0032] In an embodiment of the present invention, the in-situ polymerization reaction is carried out by reacting at 60-80°C for 8-12 hours.

[0033] In another aspect, the present invention also provides a lithium-ion battery comprising a positive electrode sheet comprising the positive electrode material as described above; and / or a positive electrode material prepared according to the preparation method described above.

[0034] Compared with the prior art, the beneficial effects of the present invention are as follows: The cathode material of this invention comprises a rhodium-doped lithium iron phosphate matrix and a first coating layer containing indium tin oxide (ITO). Rhodium doping widens ion channels and increases ion diffusion rate; the ITO coating not only enhances bulk conductivity, but the indium (In) element also suppresses rhodium segregation and improves doping efficiency. The cathode material of this invention improves the electrochemical performance of LFP at low temperatures, enhancing the battery's low-temperature cycle stability and capacity retention.

[0035] Furthermore, the cathode material of the present invention may further include a second coating layer, the second coating layer comprising a doped conductive polymer composite and coating at least a portion of the surface of the first coating layer; the doped conductive polymer composite not only increases electronic conductivity, but its elastic properties can also buffer the volume change of LFP particles; thus, by employing a dual strategy of "rhodium doping" and "multi-scale optimization of bulk phase-interface," the electrochemical performance of LFP at low temperatures is further improved, significantly enhancing the low-temperature cycle stability and capacity retention of the battery. This modification method forms a triple optimization mechanism at low temperatures, encompassing the particle interior, the particle bulk phase, and the particle interface, while simultaneously ensuring rapid electron and ion transport and significantly reducing impedance; the use of rhodium for bulk phase doping at the bulk phase and interface improves the bulk Li... + Diffusion kinetics ensures high capacity output and long-cycle stability at low temperatures. Attached Figure Description

[0036] Figure 1 This is a schematic diagram of the structure of the cathode material of the present invention; The attached figures are labeled as follows: 1: Lithium iron phosphate matrix; 2: Rhodium; 3: First coating layer; 4: Second coating layer.

[0037] Figure 2 This diagram illustrates the mechanism and effect of the rhodium doping, ITO (indium tin oxide) coating, and PANI-CAS polymer layer coating scheme of the present invention. Detailed Implementation

[0038] To better understand and implement this application, the technical solutions of this application will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are only some of the embodiments of this application, and not all of them.

[0039] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the specification of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of this application.

[0040] Unless otherwise stated, all numerical values ​​for the amounts of expressed components, reaction conditions, etc., used in the specification and claims are to be understood as being modified by the term "about". Therefore, unless otherwise indicated, the numerical parameters set forth herein are approximate values ​​that can be varied to obtain the desired performance.

[0041] For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range or individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0042] The word “and / or” as used in this article refers to one or all of the elements mentioned.

[0043] The terms "include" and "contain" as used in this article cover both cases where only the mentioned elements exist and cases where other unmentioned elements exist in addition to the mentioned elements.

[0044] The purpose of this invention is to provide a cathode material, its preparation, and its application. This cathode material can improve the electrochemical performance of LFP at low temperatures, and enhance the low-temperature cycle stability and capacity retention of the battery. The following is a detailed description of this application.

[0045] cathode materials like Figure 1 As shown, the present invention provides a positive electrode material, the positive electrode material comprising: Lithium iron phosphate substrate 1, wherein the lithium iron phosphate substrate 1 is doped with rhodium 2; and The first coating layer 3 comprises indium tin oxide and is coated on at least a portion of the surface of the lithium iron phosphate substrate.

[0046] The term "coating" is not limited to direct coating, but also includes indirect coating; that is, the coating layer can be directly coated on the lithium iron phosphate (LFP) substrate, and there can be one or more other structures between the coating layer and the lithium iron phosphate substrate; preferably, the coating layer is directly coated on the lithium iron phosphate substrate, that is, there are no other structures between the coating layer and the lithium iron phosphate substrate.

[0047] "Coating at least a portion of the surface of the lithium iron phosphate substrate" can mean coating the entire surface of the lithium iron phosphate substrate or coating a portion of the surface of the lithium iron phosphate substrate; preferably, "coating at least a portion of the surface of the lithium iron phosphate substrate" means coating the entire surface of the lithium iron phosphate substrate, that is, the coating layer completely covers the surface of the lithium iron phosphate substrate.

[0048] The cathode material of this invention comprises a rhodium-doped lithium iron phosphate matrix and a first coating layer containing indium tin oxide (ITO). Rhodium doping widens ion channels and increases ion diffusion rate; the ITO coating not only enhances bulk conductivity, but the In element also suppresses rhodium segregation and improves doping efficiency. The cathode material of this invention improves the electrochemical performance of LFP at low temperatures, enhancing the battery's low-temperature cycle stability and capacity retention. Specifically, the mechanism of action of "rhodium doping" + "indium tin oxide coating" is as follows: (1) Lattice modulation mechanism of rhodium doping: Rhodium (Rh³) + Ionic radius 0.665 Å) and iron (Fe²⁺) + With an ionic radius of 0.78 Å, rhodium can stably occupy Fe sites without causing lattice distortion; the lithium-ion diffusion channel is widened: the Rh-O bond length (2.05 Å) is greater than the Fe-O bond (2.01 Å), slightly enlarging the c-axis of the lattice parameter, improving the ion diffusion rate, and improving the rate performance. Dual-vacancy cooperative mechanism: Rh³ + Replace Fe² + Lithium vacancies (V) are generated, while Rh... 4+ / Rh³ + Redox couples can reverse the transition to regulate electron concentration, enabling synergistic electron-ion conduction.

[0049] (2) ITO-coated bulk conduction design Coating the surface of lithium iron phosphate substrate with an indium tin oxide (In2O3:SnO2=90:10) layer can form a continuous conductive network, improve conductivity, and avoid the contact resistance problem of traditional mechanical mixing. (In2O3 alone has a certain conductivity, but it is generally weak. The incorporation of Sn significantly increases the carrier concentration, thereby greatly improving conductivity.)

[0050] Rhodium segregation suppression: Thermodynamically, the difference in electronegativity is relatively small: In 1.78, Rh 2.28, resulting in a lower distortion energy during solid solution formation, lower than the energy state of rhodium at grain boundaries, thus facilitating its formation. Kinetically, the stronger covalent nature of the In-O-Rh bond compared to Fe-O-Rh fixes it within the solid solution, preventing diffusion segregation. In ITO, In³⁺… + Priority over Rh³ + The formation of InRhO3 solid solution prevents rhodium segregation at grain boundaries, affects ion diffusion, and improves doping efficiency.

[0051] In this embodiment of the invention, the rhodium concentration in the lithium iron phosphate matrix is ​​0.5-5 wt% by weight. For example, the rhodium concentration by weight is 0.5 wt%, 1 wt%, 1.5 wt%, 2 wt%, 2.6 wt%, 3 wt%, 3.5 wt%, 4 wt%, 4.5 wt%, 5 wt%, etc. When the rhodium doping level is too high, it leads to significant capacity loss and easily causes lattice distortion, damaging the crystal structure and thus affecting low-temperature discharge capacity and low-temperature cycling performance. When the rhodium doping level is too low, it results in insufficient kinetic performance, and the diffusion rate improvement after doping is not significant, leading to poor low-temperature performance.

[0052] In this embodiment of the invention, the average particle size Dv50 of the lithium iron phosphate matrix is ​​0.8~1.2μm. Exemplarily, the average particle size Dv50 of the lithium iron phosphate matrix is ​​0.8μm, 0.85μm, 0.9μm, 1.0μm, 1.05μm, 1.1μm, 1.15μm, 1.2μm, etc. When the average particle size of the lithium iron phosphate matrix is ​​within the above range, compared with conventional LFP particles, it can maintain a smaller particle size range, thereby shortening the ion transport path at low temperatures, and avoiding agglomeration and difficulty in dispersion due to excessively small particle size during processing.

[0053] In this embodiment of the invention, the molar ratio of indium oxide to tin oxide in the indium tin oxide is 7-9:1. Exemplary examples include molar ratios of 7:1, 7.5:1, 7.8:1, 8:1, 8.2:1, 8.5:1, 8.8:1, and 9:1. When the molar ratio of indium oxide to tin oxide is within the above range, ITO can possess both high conductivity and structural stability, enhancing electron conduction and reducing impedance without hindering lithium-ion transport, thus improving the battery's low-temperature and cycle performance.

[0054] In this embodiment of the invention, the thickness of the first coating layer is 10-30 nm. For example, the thickness of the first coating layer is 10 nm, 12 nm, 15 nm, 20 nm, 22 nm, 25 nm, 28 nm, 30 nm, etc. When the ITO coating layer is too thin, inner layer cycle breakage is likely to occur; when the ITO coating layer is too thick, the excessively thick coating layer will lead to a significant loss of low-temperature discharge capacity.

[0055] In this embodiment of the invention, the cathode material further includes a second coating layer 4, which comprises a doped conductive polymer composite and coats at least a portion of the surface of the first coating layer 3. Thus, while the lithium iron phosphate matrix undergoes rhodium doping and ITO coating, it is further coated with a doped conductive polymer composite. This employs a dual-strategy modification approach of "synergistic electron-ion dual conductive network" and "multi-scale optimization of bulk-interface," significantly improving the slow kinetics of LFP at low temperatures, increasing conductivity, and thereby significantly improving problems such as low low-temperature capacity retention and poor rate performance.

[0056] In an embodiment of the present invention, the conductive polymer material in the doped conductive polymer material composite includes at least one of polyaniline, polypyrrole, and polyvinyldioxythiophene.

[0057] In an embodiment of the present invention, the dopant in the doped conductive polymer composite includes at least one of camphor sulfonic acid, dodecyl sulfonic acid, dodecylbenzene sulfonic acid, toluene sulfonic acid, p-toluene sulfonic acid, and naphthalene sulfonic acid.

[0058] In this embodiment of the invention, the doped conductive polymer composite is a camphor sulfonic acid-doped polyaniline composite (PANi-CSA); wherein the molar ratio of a single repeating unit of polyaniline to camphor sulfonic acid is 1.5~2.5:1. Exemplarily, the molar ratio of a single repeating unit of polyaniline to camphor sulfonic acid is 1.5:1, 1.6:1, 1.8:1, 2.0:1, 2.1:1, 2.2:1, 2.3:1, 2.5:1, etc. CSA can provide sufficient protons (H... + Effective protonation of the polyaniline backbone activates its conductive state, maintaining the material's conductivity at a high level. If there is too little CSA, the conductivity improvement will be limited due to insufficient doping. If there is too much CSA, it may lead to overdoping, causing structural distortion or phase separation, which in turn reduces carrier migration efficiency.

[0059] PANI-CSA enables interface optimization, and the specific improvement mechanism is as follows: (1) Polyaniline chain: provides an electronic conduction path through a π-π conjugated system (conductivity 1.5 S / cm); (2) Camphor sulfonic acid (CSA): The -SO3H group dissociates to release H+. + This activates the proton hopping conduction of polyaniline; (3) Flexible interface: The elastic properties of PANi-CSA buffer the volume change of LFP particles; The hydrophobicity of PANI-CSA (camphor sulfonic acid side chain) can reduce the decrease in wettability caused by the increase in electrolyte viscosity at low temperatures. Combined with the high stability of ITO, it can inhibit the overgrowth of SEI film.

[0060] Furthermore, rhodium doping, ITO (indium tin oxide) coating, and PANI-CAS polymer layer coating exhibit a synergistic effect, as detailed below: (1) The In element in ITO (indium tin oxide) suppresses the segregation of rhodium; (2) Chemical bonding at the ITO-PANi interface: The hydroxyl groups (-OH) on the surface of ITO condense with the primary amine groups (-NH2) of PANi to form a stable bond, which is much higher than physical adsorption, preventing the coating layer from falling off during the cycle (the hydroxyl groups generated on the surface of ITO through hydrothermal reaction have high reactivity, especially during annealing, the primary amine groups of PANi under acidic conditions, camphor sulfonic acid provides an acidic environment, promotes protonation, promotes condensation reaction, and ITO undergoes condensation ITO-OH+NH2-PANi→ITO-O-NH-PANi+H2O (gas)).

[0061] When using rhodium doping, ITO (indium tin oxide) coating, and PANI-CAS polymer layer coating schemes, the working mechanism and the achieved effects are as follows: Figure 2As shown, the electron transport chain and ion transport chain formed in this way are as follows: Electron transport chain: LFP lattice interior (Rh doping) → interparticle (ITO network) → electrode current collector; Ion transport chain: electrolyte → PANi-CSA sulfonic acid sites → ITO / LFP interface → lattice channel.

[0062] In this embodiment of the invention, the thickness of the second coating layer is 20-40 nm. This thickness is sufficient to cover the microscopic defects on the surface of LiFePO4 (LFP) particles, effectively blocking electrolyte erosion, suppressing side reactions and excessive SEI film growth, and improving cycle life; the 20-40 nm thin layer ensures sufficient active site density while avoiding the increased ion diffusion resistance caused by excessive thickness, ensuring the Li + It can quickly migrate to the ITO / LFP interface; at the same time, the thickness is moderate, so as not to over-coat and cause a decrease in reversible lithium intercalation, thereby reducing the discharge capacity loss; when the second coating layer is too thin, it is difficult to form a uniform coating layer, and it is easy to decompose continuously with electrolyte side reactions during cycling, thereby deteriorating the cycle performance; when the coating layer is too thick, more discharge capacity is lost.

[0063] Preparation method of positive electrode material On the other hand, the present invention also provides a method for preparing a positive electrode material, which includes the following steps: S1. The lithium iron phosphate precursor is ball-milled and mixed with a lithium source and a rhodium source, and then spray-granulated to form a spherical precursor; the spherical precursor is sintered and crushed to obtain a rhodium-doped lithium iron phosphate matrix; S2. Mix the indium source, tin source, and lithium iron phosphate matrix, add a precipitant dropwise, and perform a hydrothermal reaction to make In³ + and Sn 4+ The material is co-precipitated and adsorbed on the surface of the lithium iron phosphate matrix, and then dried and annealed to obtain a cathode material with a first coating layer. S3. The conductive polymer monomer and dopant are mixed with the cathode material having the first coating layer, and an in-situ polymerization reaction is carried out under the action of an initiator to obtain a cathode material with a double coating layer.

[0064] In an embodiment of the present invention, in step S1, the lithium source includes at least one of lithium carbonate, lithium dihydrogen phosphate, lithium hydroxide, lithium chloride, and lithium nitrate.

[0065] In embodiments of the present invention, the rhodium source includes at least one of rhodium chloride, rhodium nitrate, and rhodium acetylacetonate.

[0066] In this embodiment of the invention, the molar ratio of the lithium source to the rhodium source is 1:0.045~0.5. Exemplarily, the molar ratio of the lithium source to the rhodium source is 1:0.045, 1:0.1, 1:0.15, 1:0.2, 1:0.25, 1:0.3, 1:0.35, 1:0.4, 1:0.45, 1:0.5, etc. When the rhodium doping level is high, the high doping level leads to greater capacity loss and is prone to lattice distortion, affecting low-temperature discharge capacity and low-temperature cycling performance. When the rhodium doping level is low, it results in insufficient kinetic performance, thus leading to poor low-temperature performance.

[0067] In this embodiment of the invention, the sintering is a two-stage sintering process performed under a weakly reducing atmosphere; wherein, the first stage of sintering refers to holding at 300~500℃ for 2~4 hours; the second stage of sintering refers to holding at 600~800℃ for 6~10 hours. The purpose of the first stage of sintering is to remove water of crystallization; the purpose of the second stage of sintering is to promote the formation of crystalline phases. Preferably, the weakly reducing atmosphere refers to a reducing atmosphere with a N2 to H2 volume ratio of 95:5.

[0068] In an embodiment of the present invention, in step S2, the indium source includes at least one of indium nitrate, indium chloride, and indium hydroxide.

[0069] In embodiments of the present invention, the tin source includes at least one of tin tetrachloride, tin nitrate, and tin oxide.

[0070] In this embodiment of the invention, the molar ratio of the indium source to the tin source is 7~9:1~3. Exemplarily, the molar ratio of the indium source to the tin source is 7:1, 7:2, 7:3, 8:1, 8:2, 8:3, 9:1, 9:2, 9:3, etc.

[0071] In embodiments of the present invention, the precipitant includes at least one of ammonia, urea, ammonium bicarbonate, and potassium hydroxide.

[0072] In this embodiment of the invention, the hydrothermal reaction refers to a reaction at 100-140°C for 6-10 hours. For example, the hydrothermal reaction refers to a reaction at 100°C for 10 hours; for example, the hydrothermal reaction refers to a reaction at 120°C for 8 hours; for example, the hydrothermal reaction refers to a reaction at 140°C for 6 hours.

[0073] In this embodiment of the invention, the annealing treatment refers to holding at 400~600℃ for 2-4 hours. For example, the annealing treatment refers to holding at 400℃ for 4 hours; for example, the annealing treatment refers to holding at 500℃ for 3 hours; for example, the annealing treatment refers to holding at 600℃ for 2 hours.

[0074] In an embodiment of the present invention, in step S3, the initiator includes at least one of ammonium persulfate, potassium persulfate, ferric chloride, and potassium dichromate.

[0075] In an embodiment of the present invention, the conductive polymer monomer includes at least one of aniline, pyrrole, and 3,4-ethylenedioxythiophene.

[0076] In embodiments of the present invention, the dopant includes at least one of camphor sulfonic acid, dodecyl sulfonic acid, dodecylbenzene sulfonic acid, toluene sulfonic acid, p-toluene sulfonic acid, and naphthalene sulfonic acid.

[0077] In this embodiment of the invention, the molar ratio of the conductive polymer monomer to the dopant is 1.5 to 2.5:1. Exemplarily, the molar ratio of the conductive polymer monomer to the dopant is 1.5:1, 1.6:1, 1.8:1, 2.0:1, 2.2:1, 2.4:1, 2.5:1, etc.

[0078] In this embodiment of the invention, the in-situ polymerization reaction is carried out at 60-80°C for 8-12 hours. For example, the in-situ polymerization reaction is carried out at 60°C for 12 hours; for example, the in-situ polymerization reaction is carried out at 70°C for 10 hours; for example, the in-situ polymerization reaction is carried out at 80°C for 8 hours.

[0079] Lithium-ion batteries In another aspect, the present invention also provides a lithium-ion battery comprising a positive electrode sheet comprising the positive electrode material as described above; and / or a positive electrode material prepared according to the preparation method described above.

[0080] In embodiments of the present invention, the lithium-ion battery further includes a negative electrode, an electrolyte, and a separator. The separator is disposed between the positive and negative electrodes, and the electrolyte fills the pores of the separator and wets both the positive and negative electrodes. During battery charging and discharging, active ions repeatedly insert and extract between the positive and negative electrodes; the electrolyte acts as a conductor between the positive and negative electrodes; and the separator, disposed between the positive and negative electrodes, primarily prevents short circuits between the positive and negative electrodes while allowing ions to pass through. The present invention does not impose any particular limitations on the negative electrode, electrolyte, or separator, as long as the objective of this application is achieved.

[0081] The present invention will be further illustrated below with reference to the embodiments: Example 1 A method for preparing a positive electrode material includes the following steps: (1) Preparation of porous LiFePO4 (rhodium doped) by co-precipitation method: Iron salt FeSO4·7H2O (0.5 mol / L) and H3PO4 (0.55 mol / L) were mixed at a molar ratio of Fe:P = 1:1.1. Citric acid (iron ion to citric acid molar ratio of 1:2) was added as a complexing agent, and the reaction was maintained at pH 3 at 60℃ for 8 h. The product was washed and then hydrothermally treated at 200℃ for 12 h to obtain the lithium iron phosphate precursor. Lithium salt Li2CO3 (lithium salt to iron salt molar ratio of 1.05:1) and rhodium source RhCl3 (rhodium source to iron source molar ratio of 0.2:1) were added. The mixture was ball-milled at 400 rpm for 8 h using ethanol (alcohol solution) as the medium, and then spray-granulated. The slurry was spray-dried (inlet 180℃, outlet 100℃) to form spherical precursors with a particle size of 20 μm. The material was sintered in a tube furnace under a N2 / H2 (95:5) atmosphere in stages: the first stage of sintering was carried out at 400℃ for 2 hours (to remove water of crystallization); the second stage of sintering was carried out at 600℃ for 8 hours (to form crystal phase). The sintered material was then pulverized to Dv50 = 1μm to obtain Rh-LFP@ powder.

[0082] (2) ITO coating: Prepare a 100 ml mixed solution of 0.1 mol / L In(NO3)3 / SnCl4 (molar ratio In:Sn=9:1) to pH=4, mix with 5 g of Rh-LFP powder, ultrasonically disperse, add ammonia water (pH=9.0), stir at 80℃ for 3 h, hydrothermally react at 120℃ for 8 h, centrifuge and dry, and anneal at 600℃ for 2 h to obtain Rh-LFP@ITO powder with an ITO coating thickness of 20 nm.

[0083] (3) Polymer coating (PANi-CSA): A mixed solution of 0.1 mol / L 50 ml aniline and 50 ml 0.05 mol / L camphor sulfonic acid was prepared, 40 ml ethanol was added, followed by 50 g of the above Rh-LFP@ITO powder. The mixture was ultrasonically dispersed for 2 h, and polymerization was initiated by adding 15 ml of 0.1 M / L (NH4)2S2O8 at 60 °C for 8 h. The product was washed three times with ethanol to obtain the final product PANI-CSAC@ITO@Rh-LFP, with a PANI-CSAC coating layer thickness of 30 nm.

[0084] Example 2 The only difference between this embodiment and embodiment 1 is that in step (1), the molar ratio of the rhodium source and the iron source is 0.1:1.

[0085] Example 3 The only difference between this embodiment and embodiment 1 is that in step (1), the molar ratio of the rhodium source and the iron source is 0.3:1.

[0086] Example 4 The only difference between this embodiment and embodiment 1 is that step (2) is: ITO coating: A 0.1 mol / L In(NO3)3 / SnCl4 mixed solution (molar ratio In:Sn=9:1) was prepared to pH=4 and mixed with 2.5 g Rh-LFP powder. After ultrasonic dispersion, ammonia water (pH=9.0) was added dropwise. The mixture was stirred at 80℃ for 3 h, and then hydrothermally reacted at 120℃ for 8 h. After centrifugation and drying, the mixture was annealed at 600℃ for 2 h to obtain Rh-LFP@ITO with an ITO coating thickness of 30 nm.

[0087] Example 5 The only difference between this embodiment and embodiment 1 is that step (2) is: ITO coating: A 0.1 mol / L In(NO3)3 / SnCl4 mixed solution (molar ratio In:Sn = 9:1) was prepared and pH=4. This solution was then mixed with 10 g of Rh-LFP powder, ultrasonically dispersed, and ammonia water (pH=9.0) was added dropwise. The mixture was stirred at 80℃ for 3 h, followed by hydrothermal reaction at 120℃ for 8 h. After centrifugation and drying, the mixture was annealed at 600℃ for 2 h to obtain Rh-LFP@ITO. I The TO coating thickness is 10 nm.

[0088] Example 6 The only difference between this embodiment and Embodiment 1 is that step (3) is: polymer coating (PANI-CSA): A mixed solution of 0.1 mol / L 20 ml aniline and 50 ml 0.05 mol / L camphor sulfonic acid was prepared, 40 ml ethanol was added, followed by 50 g of the above Rh-LFP@ITO powder. The mixture was ultrasonically dispersed for 2 h, and polymerization was initiated by adding 15 ml of 0.1 M / L (NH4)2S2O8 at 60 °C for 6 h. The product was washed three times with ethanol to obtain the final product PANI-CSAC@ITO@Rh-LFP, with a PANI-CSAC coating layer thickness of 20 nm.

[0089] Example 7 The only difference between this embodiment and Embodiment 1 is that step (3) is: polymer coating (PANI-CSA): A mixed solution of 0.1 mol / L 100 ml aniline and 50 ml 0.05 mol / L camphor sulfonic acid was prepared, and 40 ml ethanol was added. Then, 50 g of the above Rh-LFP@ITO powder was added and ultrasonically dispersed for 2 h. Polymerization was initiated by adding 15 ml of 0.1 M / L (NH4)2S2O8 at 60 °C for 10 h. The product was washed three times with ethanol to obtain the final product PANI-CSAC@ITO@Rh-LFP, with a PANI-CSAC coating layer thickness of 40 nm.

[0090] Example 8 The only difference between this embodiment and Embodiment 1 is that step (3) is: polymer coating (PPy-DSA): A mixed solution of 0.1 mol / L 50 mL pyrrole + 50 mL 0.05 mol / L dodecyl sulfonic acid was prepared, 40 mL ethanol was added, followed by 50 g of the above Rh-LFP@ITO powder. The mixture was ultrasonically dispersed for 2 h, and polymerization was initiated by dropping 15 mL of 0.1 M / L (NH4)2S2O8 at 60 °C for 8 h. The product was washed three times with ethanol to obtain the final product PPy-DSA@ITO@Rh-LFP, with a PPy-DSA coating layer thickness of 30 nm.

[0091] Example 9 The only difference between this embodiment and Embodiment 1 is that step (3) is polymer coating (PANi): A mixed solution of 0.1 mol / L 50 ml aniline was prepared, and 40 ml ethanol was added. Then, 50 g of the above Rh-LFP@ITO powder was added, and the mixture was ultrasonically dispersed for 2 h. The monomer was polymerized at 60 °C for 8 h by adding 15 ml of 0.1 M / L (NH4)2S2O8 dropwise. The product was washed three times with ethanol to obtain the final product PANi@ITO@Rh-LFP.

[0092] Example 10 The only difference between this embodiment and Embodiment 1 is that step (3) is polymer coating (CAS): Prepare 50 ml of a mixed solution of 0.05 mol / L cerebral sulfonic acid, add 40 ml of ethanol, then add 50 g of the above Rh-LFP@ITO powder, sonicate for 2 h, and initiate monomer polymerization at 60 °C for 8 h by adding 15 ml of 0.1 M / L (NH4)2S2O8 dropwise. Wash three times with ethanol to obtain the final product CSAC@Rh-LFP, with a PANi-CSAC coating thickness of 30 nm.

[0093] Example 11 The only difference between this embodiment and embodiment 1 is that step (3) is omitted.

[0094] Comparative Example 1 The only difference between this comparative example and Example 1 is that in step (1), no rhodium source RhCl3 was added.

[0095] Comparative Example 2 A method for preparing a positive electrode material includes the following steps: (1) Preparation of porous LiFePO4 (rhodium doped) by co-precipitation method: Iron salt FeSO4·7H2O (0.5 mol / L) and H3PO4 (0.55 mol / L) were mixed at a molar ratio of Fe:P = 1:1.1. Citric acid (iron ion to citric acid molar ratio of 1:2) was added as a complexing agent, and the reaction was maintained at pH 3 at 60℃ for 8 h. The product was washed and then hydrothermally treated at 200℃ for 12 h to obtain the lithium iron phosphate precursor. Lithium salt Li2CO3 (lithium salt to iron salt molar ratio of 1.05:1) and rhodium source RhCl3 (rhodium source to iron source molar ratio of 0.2:1) were added. The mixture was ball-milled at 400 rpm for 8 h using ethanol (alcohol solution) as the medium, and then spray-granulated. The slurry was spray-dried (inlet 180℃, outlet 100℃) to form spherical precursors with a particle size of 20 μm. The material was sintered in a tube furnace under a N2 / H2 (95:5) atmosphere in stages: the first stage of sintering was carried out at 400℃ for 2 hours (to remove water of crystallization); the second stage of sintering was carried out at 600℃ for 8 hours (to form crystal phase). The sintered material was then pulverized to Dv50 = 1μm to obtain Rh-LFP@ powder.

[0096] (2) Polymer coating (PANi-CSA): A mixed solution of 0.1 mol / L 50 ml aniline and 50 ml 0.05 mol / L camphor sulfonic acid was prepared, 40 ml ethanol was added, followed by 50 g of the above Rh-LFP@ powder. The mixture was ultrasonically dispersed for 2 h, and polymerization was initiated by adding 15 ml of 0.1 M / L (NH4)2S2O8 at 60 °C for 8 h. The product was washed three times with ethanol to obtain the final product PANI-CSAC @ Rh-LFP, with a PANI-CSAC coating thickness of 30 nm.

[0097] Comparative Example 3 The only difference between this comparative example and Example 1 is that step (2) is as follows: 10 mL of 0.1 mol / L In(NO3)3 solution is prepared to pH=4 and mixed with 5 g of LFP powder. After ultrasonic dispersion, ammonia water (pH=9.0) is added dropwise, stirred at 80℃ for 3 h, hydrothermally reacted at 120℃ for 8 h, centrifuged and dried, and then annealed at 600℃ for 2 h to obtain Rh-LFP@IN2O3 powder.

[0098] Accordingly, in step (3), the Rh-LFP@ITO powder is changed to Rh-LFP@IN2O3 powder, and the PANi-CSAC@ITO@Rh-LFP is changed to PANi-CSAC@IN2O3@Rh-LFP.

[0099] Comparative Example 4 A method for preparing a positive electrode material includes the following steps: Porous LiFePO4 (rhodium-doped) was prepared by co-precipitation: Iron salt FeSO4·7H2O (0.5 mol / L) and H3PO4 (0.55 mol / L) were mixed at a molar ratio of Fe:P = 1:1.1. Citric acid (iron ion to citric acid molar ratio of 1:2) was added as a complexing agent, and the reaction was maintained at pH 3 at 60℃ for 8 h. After washing, the product was hydrothermally treated at 200℃ for 12 h to obtain the lithium iron phosphate precursor. Lithium salt Li2CO3 (lithium salt to iron salt molar ratio of 1.05:1) and rhodium source RhCl3 (rhodium source to iron source molar ratio of 0.2:1) were added. The mixture was ball-milled at 400 rpm for 8 h using ethanol (alcohol solution) as the medium, and then spray-granulated. The slurry was spray-dried (inlet 180℃, outlet 100℃) to form spherical precursors with a particle size of 20 μm. The material was sintered in a tube furnace under a N2 / H2 (95:5) atmosphere in stages: the first stage of sintering was carried out at 400℃ for 2 hours (to remove water of crystallization); the second stage of sintering was carried out at 600℃ for 8 hours (to form crystal phase). The sintered material was then pulverized to Dv50 = 1μm to obtain Rh-LFP@ powder.

[0100] Performance testing 1. Battery fabrication and electrochemical performance testing Using the materials synthesized in Examples 1-11 and Comparative Examples 1-4 as positive electrode materials, to test the electrochemical performance of the lithium-ion positive electrode materials obtained in each example and comparative example, the positive electrode materials obtained in each example or comparative example, the binder polyvinylidene fluoride (PVDF), and the conductive agent SP were dissolved in N-methylpyrrolidone (NMP) at a mass ratio of 80:10:10 and stirred to form a uniform and stable slurry. The slurry was then coated onto aluminum foil, dried, and the positive electrode sheet was obtained. The positive electrode sheet was cut, weighed, and placed in a glove box. In the glove box, using a sodium metal sheet as the negative electrode, LiPF6 dissolved in diethylene glycol dimethyl ether as the electrolyte, and PP as the separator, CR2032 button cells were assembled. The button cells were then tested sequentially at a current density of 0.1 using the Land battery testing system within a voltage window of 2.5~3.65V, under the following test conditions: (1) First discharge capacity at room temperature: Charge and discharge at 0.2C constant current for 3 times (2.5-3.65 V) at 25℃, and record the first discharge capacity; (2) Low temperature test: The battery was placed in a high and low temperature test chamber (-20℃±0.5℃) and kept at a constant temperature for 10 h; First low-temperature charge-discharge capacity: The nominal specific capacity was set to 170mAh / g. The test was conducted at 0.2C with constant current charging to 3.65V and constant current discharging to 2.5V. The first low-temperature discharge capacity was recorded. (3) Low temperature cycle test: Under the set low temperature environment (-20℃±0.5℃), the constant current charging to 3.65 V and the constant current discharging to 2.5 V were performed at a rate of 0.1C to complete 300 cycles. The discharge capacity of the first cycle was used as the initial capacity, and the capacity retention rate of the 300th cycle was recorded and calculated.

[0101] Data processing: Capacity retention rate at week 300 = (capacity at week 300 / capacity at week 1) × 100%.

[0102] (4) EIS test: The battery was tested using an electrochemical workstation. Test frequency: 0.01Hz-100KHz; voltage perturbation: 5mV, and the charge transfer resistance value Rct was obtained.

[0103] 2. Test Results The electrochemical performance of the batteries made from the cathode materials of each embodiment and each comparative example was tested under the above test conditions, and the test results are shown in Table 1.

[0104] Table 1. Performance test results of the batteries corresponding to the cathode materials of each embodiment and comparative example.

[0105] As can be seen from the test results of Examples 1-8 and Comparative Examples 1-4 in Table 1, the cathode materials in Examples 1-8 adopted a triple synergistic design of rhodium doping combined with ITO and PANI-CAS double-layer coating. Compared with Comparative Examples 1-4, the cathode materials in Examples 1-8 have higher low-temperature discharge capacity, lower impedance values ​​in EIS tests, and higher low-temperature capacity retention, confirming that the triple synergistic design effectively improves the electrochemical performance of LFP at low temperatures and significantly enhances the low-temperature cycle stability and capacity retention of the battery. In particular, Example 1, with a double-layer coating configuration of 2wt% rhodium doping combined with ITO and PANI-CAS, can achieve a discharge capacity of 132.8 mAh / g at -20℃ / 0.2C; the EIS test shows a lower impedance value, indicating a significant improvement in kinetics; in terms of cycle stability, the capacity retention rate after 300 cycles reaches 93.2%, confirming that the triple synergistic design effectively suppresses structural degradation during low-temperature cycling. Comparing Examples 1-3, it can be seen that when the rhodium doping amount is high (corresponding to Example 3, the rhodium doping amount is 3wt%), the low-temperature discharge capacity, impedance value, and low-temperature capacity retention rate are worse. This is mainly because high doping amounts lead to greater capacity loss and are prone to lattice distortion, affecting the low-temperature discharge capacity and low-temperature cycling performance. When the rhodium doping amount is low (corresponding to Example 2, the rhodium doping amount is 1wt%), the low-temperature discharge capacity, impedance value, and low-temperature capacity retention rate are worse than in Example 1. This is mainly because low doping amounts lead to insufficient kinetic performance, resulting in poor low-temperature performance. Comparing Examples 2 and 3 confirms that rhodium doping can effectively improve intrinsic conductivity, but the cycling stability is still not good enough, and an appropriate doping amount is required to achieve the best effect.

[0106] Comparing Examples 1, 4, and 5, it can be seen that the thickness of the ITO coating layer has a significant impact on the electrochemical performance of the battery: when the ITO coating layer is thicker (corresponding to Example 5, the ITO coating layer thickness is 30 nm), the low-temperature discharge capacity, impedance value, and low-temperature capacity retention rate are worse. This is mainly because the thickness increases the distance of the ion transfer interface, and excessive thickness also increases the film transfer impedance. When the ITO coating layer is thinner (corresponding to Example 4, the ITO coating layer thickness is 10 nm), the low-temperature discharge capacity, impedance value, and low-temperature capacity retention rate are worse than in Example 1. This is mainly because when the ITO coating layer is too thin, uneven coating can easily lead to poor conductivity, resulting in inner layer cycle breakage, which in turn hinders lithium-ion transport and relatively increases charge transfer impedance.

[0107] Comparing Examples 1, 6, and 7, it can be seen that the thickness of the PANi-CAS coating layer has a significant impact on the electrochemical performance of the battery: when the PANi-CAS coating layer is thicker (corresponding to Example 7, the PANi-CAS coating layer thickness is 40 nm), the discharge capacity lost is greater; when the PANi-CAS coating layer is thinner (corresponding to Example 6, the PANi-CAS coating layer thickness is 20 nm), the low-temperature discharge capacity, impedance value, and low-temperature capacity retention rate are worse than in Example 1. This is mainly because when the coating layer is thinner, it is more difficult to form a uniform coating layer, which is more likely to decompose continuously during cycling due to electrolyte side reactions, thus affecting the cycling performance.

[0108] Examples 9 and 10 involved single polymer coating, while Example 11 involved no polymer coating. Comparing the Rct values ​​and low-temperature capacity retention of Examples 1 and 9-11 reveals that polymer coating improves low-temperature conductivity and cycling performance, primarily because it addresses bulk conductivity issues. Compared to single polymer coatings of PANi or CAS, the PANi-CAS polymer exhibits superior performance.

[0109] Comparing Example 1 with Comparative Example 2 (without ITO coating) and Comparative Example 3 (with only IN2O3 coating), when ITO is not added, although the initial capacity difference is not large, the low-temperature capacity retention rate is low. Compared with Comparative Example 3 with only IN2O3 coating, it was found that although IN2O3 can reduce the Rct value, the performance is still lower than that of complete ITO coating, indicating that ITO constructs an efficient electron channel.

[0110] Comparing Examples 1 and 11 with Comparative Examples 1 and 2, it was found that Example 1 showed a significant improvement in the initial low-temperature discharge capacity, a significant decrease in Rct, and a significant increase in cycle retention, indicating that the triple modification has a synergistic effect.

[0111] Comparing Example 11 and Comparative Example 4, it can be seen that ITO, as a highly conductive transparent oxide, forms a continuous conductive network on the particle surface, expanding the electron transport path from "Rh-doped LFP lattice conduction" to a highly efficient dual-channel mode of "lattice (Rh) → surface (ITO) → current collector," significantly improving rate performance. The In³⁺ in the ITO coating layer... + Can be used with Rh³ + Lattice interactions occur, effectively suppressing surface segregation and agglomeration of Rh during high-temperature sintering or long-term cycling, maintaining its uniform distribution in the LFP lattice, thereby ensuring cycling stability.

[0112] The technical means disclosed in this application are not limited to those disclosed in the above embodiments, but also include technical solutions composed of any combination of the above technical features. It should be noted that those skilled in the art can make several improvements and modifications without departing from the principles of this application, and these improvements and modifications are also considered to be within the scope of protection of this application.

Claims

1. A cathode material, characterized in that, The cathode material includes: A lithium iron phosphate matrix, wherein the lithium iron phosphate matrix is ​​doped with rhodium; and A first coating layer comprising indium tin oxide and covering at least a portion of the surface of the lithium iron phosphate substrate.

2. The cathode material as described in claim 1, characterized in that, In the lithium iron phosphate matrix, the rhodium concentration is 0.5-5 wt% by weight. And / or, the average particle size Dv50 of the lithium iron phosphate matrix is ​​0.8~1.2μm; And / or, in the indium tin oxide, the molar ratio of indium oxide to tin oxide is 7-9:1; And / or, the thickness of the first coating layer is 10~30nm.

3. The positive electrode material as described in claim 1, characterized in that, The cathode material also includes: A second coating layer comprising a doped conductive polymer composite material and coating at least a portion of the surface of the first coating layer.

4. The cathode material as described in claim 3, characterized in that, The conductive polymer material in the doped conductive polymer material composite includes at least one of polyaniline, polypyrrole, and polyvinyldioxythiophene. And / or, the dopant in the doped conductive polymer composite includes at least one of camphor sulfonic acid, dodecyl sulfonic acid, dodecylbenzene sulfonic acid, toluene sulfonic acid, p-toluene sulfonic acid, and naphthalene sulfonic acid.

5. The cathode material as described in claim 3, characterized in that, The doped conductive polymer composite is a camphor sulfonic acid-doped polyaniline composite. The molar ratio of a single repeating unit of the polyaniline to camphor sulfonic acid is 1.5~2.5:

1. And / or, the thickness of the second coating layer is 20-40 nm.

6. A method for preparing a positive electrode material, characterized in that, Includes the following steps: S1. The lithium iron phosphate precursor is ball-milled and mixed with a lithium source and a rhodium source, and then spray-granulated to form a spherical precursor; the spherical precursor is sintered and crushed to obtain a rhodium-doped lithium iron phosphate matrix; S2. Mix the indium source, tin source, and lithium iron phosphate matrix, add a precipitant dropwise, and perform a hydrothermal reaction to make In³ + and Sn 4+ The material is co-precipitated and adsorbed on the surface of the lithium iron phosphate matrix, and then dried and annealed to obtain a cathode material with a first coating layer. S3. The conductive polymer monomer and dopant are mixed with the cathode material having the first coating layer, and an in-situ polymerization reaction is carried out under the action of an initiator to obtain a cathode material with a double coating layer.

7. The method for preparing the cathode material as described in claim 6, characterized in that, In step S1, the lithium source includes at least one of lithium carbonate, lithium dihydrogen phosphate, lithium hydroxide, lithium chloride, and lithium nitrate. And / or, the rhodium source includes at least one of rhodium chloride, rhodium nitrate, and rhodium acetylacetone; And / or, the molar ratio of the lithium source to the rhodium source is 1:0.045~0.5; And / or, the sintering is a two-stage sintering process carried out in a weakly reducing atmosphere; wherein, the first stage of sintering refers to holding at 300~500℃ for 2~4h; and the second stage of sintering refers to holding at 600~800℃ for 6~10h.

8. The method for preparing the cathode material as described in claim 6, characterized in that, In step S2, the indium source includes at least one of indium nitrate, indium chloride, and indium hydroxide. And / or, the tin source includes at least one of tin tetrachloride, tin nitrate, and tin oxide; And / or, the molar ratio of the indium source to the tin source is 7~9:1~3; And / or, the precipitant includes at least one of ammonia, urea, ammonium bicarbonate, and potassium hydroxide; And / or, the hydrothermal reaction refers to a reaction at 100~140℃ for 6~10h; And / or, the annealing treatment refers to holding at 400~600℃ for 2-4 hours.

9. The method for preparing the cathode material as described in claim 6, characterized in that, In step S3, the initiator includes at least one of ammonium persulfate, potassium persulfate, ferric chloride, and potassium dichromate. And / or, the conductive polymer monomer includes at least one of aniline, pyrrole, and 3,4-ethylenedioxythiophene; And / or, the dopant includes at least one of camphor sulfonic acid, dodecyl sulfonic acid, dodecylbenzene sulfonic acid, toluene sulfonic acid, p-toluene sulfonic acid, and naphthalene sulfonic acid; And / or, the molar ratio of the conductive polymer monomer to the dopant is 1.5~2.5:1; And / or, the in-situ polymerization reaction is carried out by reacting at 60~80°C for 8~12 hours.

10. A lithium-ion battery, characterized in that, It includes a positive electrode sheet, which comprises the positive electrode material according to any one of claims 1 to 5; and / or, the positive electrode material prepared by the preparation method according to any one of claims 6 to 9.

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