FeS2@C alkali metal ion battery negative electrode material and preparation and application thereof

Abstract

The application relates to FeS2@C alkali metal ion battery negative materials and preparation and application thereof, belongs to the field of alkali metal batteries, and particularly relates to sodium ion battery, lithium ion battery negative materials and potassium ion battery negative materials. The preparation method is divided into preparation of a FeS2@C composite precursor and synthesis of a FeS2@C composite material; the synthesized nitrogen-doped FeS2@C composite material is small FeS2 nanoparticle anchoring and dispersion on a nanoscale carbon base, and large FeS2 is distributed outside the carbon base and forms graphitized carbon around the catalyst. The FeS2@C composite can realize fast electron and ion transmission, and is more beneficial to the occurrence of electrochemical reactions. The composite material has good rate performance and large-rate cycle performance.

Description

Technical Field

[0001] This invention relates to the field of alkali metal batteries, and particularly to sodium-ion batteries, lithium-ion battery anode materials, and potassium-ion battery anode materials. Background Technology

[0002] As a replacement for lithium-ion batteries, sodium-ion batteries have attracted widespread attention in large-scale energy storage systems due to the abundance of sodium resources. The development requirements for safety, reliability, and high capacity have made conversion-type anode materials an important candidate. Among them, iron disulfide (theoretical capacity, 894.8 mAh g⁻¹) is a promising candidate. -1 Iron disulfide (Fe-X) batteries are particularly prominent due to their abundant resources and environmentally friendly characteristics. More importantly, the Fe-X bond (where X is a heteroatom) typically exhibits high catalytic activity through asymmetric electron spin density and strong hybridization coordination, benefiting from interfacial reactions. These combined characteristics allow for the rational design of interfacially catalytically active Fe-X electrodes, thereby achieving high-performance sodium-ion batteries. However, the poor reversibility of the conversion reaction leads to rapid capacity decay, which, despite significant efforts in previous work, remains a major challenge hindering its practical application.

[0003] While FeS2 boasts a high theoretical capacity, its large volume change and poor kinetics during discharge / charge lead to poor rate performance and rapid cycle capacity decay when used as an electrode material. Theoretically, constructing smaller FeS2 nanoparticles through appropriate nanostructure engineering can effectively reduce diffusion length, thereby improving ion and electron conduction rates and achieving high-rate sodium-ion battery performance. The preparation of carbon-metal compound composites with unique micro / nano structures has been shown to effectively improve the overall electrochemical performance of electrode materials. The carbon in the composite increases conductivity while suppressing the volume expansion of the metal compound. Simultaneously, the nanoscale metal compound can catalyze the formation of graphitized carbon from the surrounding carbon material, providing additional free space to buffer volume changes and offering more sodium-ion insertion / extraction sites. Therefore, the rational design and synthesis of FeS2@NC composites with unique structures is crucial for achieving high-performance sodium-ion batteries and provides important reference and guidance for the controllable preparation of transition metal sulfides. Summary of the Invention

[0004] A FeS2@C alkali metal ion battery anode material

[0005] 1) Preparation of the precursor for the FeS2@C complex:

[0006] First, dissolve 4-0g (preferably 1.5-0.5g, more preferably 1.0g) of F127 in 100mL of a mixture of water and ethanol (volume ratio of 1:0-0:1, preferably 1:1) to obtain a solution;

[0007] Then, under stirring conditions, 0.5808 g to 11.6166 g (preferably 0.58083 g to 5.8083 g, more preferably 5.8083 g) of soluble iron salt is added to the above solution to obtain a mixture solution; then, 1,3,5-benzenetricarboxylic acid with a molar ratio of 3:1 to 1:3 (preferably 2:1 to 1:2, more preferably 1:1) with metal ions is added to the above mixture solution, and the mixture is stirred for 30 (20-60 minutes) minutes. After centrifugation, the solid product is separated, washed with a mixture of water and ethanol in a volume ratio (1:0-0:1, preferably 1:1), and dried to obtain polymer balls;

[0008] Finally, the obtained polymer spheres were placed in an inert atmosphere at 0.1-6℃ for [time range missing]. -1 (Preferred temperature: 0.1-3℃min) -1 More preferably 1℃ min -1 The temperature is increased to 600-1000℃ (preferably 600-800℃, more preferably 600℃) by heating at a heating rate, and calcined at the calcination temperature for 1-10h (preferably 1-6h, more preferably 2-4h) to obtain the precursor particles of the FeS2@C composite.

[0009] 2) Synthesis of FeS2@C composite material:

[0010] The precursor particles synthesized in step 1) and the sulfur source were mixed at a mass ratio of 1:1-1:4 (preferably 1:1-1:2, more preferably 1:1) and then placed in an inert atmosphere at 2°C for 1 minute. -1 (Preferred temperature: 0.1-6℃ min) -1 More preferably 0.1-3℃ min -1 The FeS2@C can be obtained by heating the FeS2@C to a calcination temperature of 200-800℃ (preferably 300-600℃, more preferably 400-500℃) at a heating rate and calcining it at the calcination temperature for 1-8 hours (preferably 3-6 hours, more preferably 2-4 hours).

[0011] The soluble iron salts are one or more of the following: Fe(NO3)3·9H2O, Fe(NO3)3, FeCl3, Fe2(SO4)3, FeSO4, Fe(NO3)2, and FeCl2.

[0012] The sulfur source is one or more of sulfur powder and thiourea;

[0013] The inert atmosphere gas is one or more of Ar and N2.

[0014] A FeS2@C alkali metal ion battery anode material prepared by the aforementioned preparation method.

[0015] An application of the aforementioned material as a negative electrode active material in an alkali metal ion battery.

[0016] Alkali metal ion batteries include lithium-ion batteries, sodium-ion batteries, or potassium-ion batteries.

[0017] The technical problem to be solved by this invention (the purpose of the invention)

[0018] 1. Commercial sodium-ion batteries often use expensive hard carbon, while Fe and S are abundant and inexpensive elements found in the Earth's crust. Doping carbon materials with a certain amount of FeS2 can both improve the theoretical specific capacity and reduce costs.

[0019] 2. Commercially available hard carbon composites have low specific capacity and poor rate and cycle performance, but the composite material synthesized in this invention shows significant improvements in rate performance and cycle performance.

[0020] 3. In the FeS2@NC composite material of the present invention, the minimum size of FeS2 is about 10 nm. This size can shorten the ion transport path and increase the reaction rate, while catalyzing the formation of graphitized carbon around it to inhibit volume expansion. Therefore, it can exhibit high electrochemical activity.

[0021] Beneficial effects of the technical solution of this invention

[0022] 1. The synthesized nitrogen-doped FeS2@NC composite material features small FeS2 nanoparticles anchored and dispersed on a nanoscale carbon substrate, while larger FeS2 particles are distributed outside the carbon substrate and form graphitized carbon around the catalyst. The FeS2@NC composite material enables rapid electron and ion transport, which is more conducive to the occurrence of electrochemical reactions.

[0023] 2. This composite material exhibits good rate capability and high-rate cycling performance. Attached Figure Description

[0024] Figure 1 XRD pattern of FeS2@C;

[0025] Figure 2 ac: SEM image of FeS2@C; df: TEM image of the synthesized FeS2@C;

[0026] Figure 3 Electron diffraction patterns of different regions of FeS2@C;

[0027] Figure 4 The graph shows the rate performance of FeS2@C at different temperatures;

[0028] Figure 5 For FeS2@C at 10 A·g -1 Long cycle plot at current density. Detailed Implementation

[0029] Example 1

[0030] Preparation of FeS2@C:

[0031] Step 1: Synthesis of Polymer Nanoparticles: First, a precursor for the FeS2@C composite was prepared. First, 1.0 g of F127 (an addition polymer of polypropylene glycol and ethylene oxide) was dissolved in 100 mL of a mixture of water and ethanol (volume ratio 1:1) and stirred vigorously at room temperature to obtain a clear solution. Then, 5.8083 g of Fe(NO3)3·9H2O was added to the solution at a stirring rate of 500 rpm to form a clear solution. After stirring for 30 minutes, 3.0212 g of 1,3,5-benzenetricarboxylic acid was added to the above mixture, and the reaction was continuously stirred for 30 minutes. After centrifugation, the separated product was washed three times with a 1:1 volume ratio mixture of water and ethanol and dried to obtain polymer microspheres. Finally, the obtained polymer microspheres were incubated in an Ar atmosphere at 1 °C for 1 min. -1 The precursor of the FeS2@C complex can be obtained by heating to 600℃ and calcining for 2 hours.

[0032] Step 2: Synthesis of nitrogen-doped FeS2@C composite material (FeS2@C): To obtain the FeS2@C composite, the precursor particles synthesized in step 1) and the sulfur source (sulfur powder) were ground and mixed at a mass ratio of 1:1 and placed in a ceramic boat. Then, the mixture was in an Ar atmosphere at 2℃ for 1 minute. -1 FeS2@C can be obtained by heating the product to 450℃ and calcining it for 3 hours.

[0033] Product characterization description: Results are as follows Figure 1 and 2 As shown, FeS2 nanoparticles are loaded onto a C support. FeS2 comprises two crystal forms: orthorhombic FeS2 particles and cubic FeS2 particles, with corresponding particle sizes of 3-5 nm and 50-100 nm, respectively. The cubic FeS2 particles are located on the surface of the C support, and the outer surface of the FeS2 particles is coated with a C layer of approximately 5 nm thickness, while the orthorhombic FeS2 particles are embedded inside the C support.

[0034] Product application performance testing: FeS2@C prepared in Example 1 and metallic sodium were used as the positive and negative electrodes of a sodium-ion half-cell, respectively. Preparation of the FeS2@C positive electrode sheet: A slurry was prepared using FeS2@C as the electrode active material, super P as the conductive agent, and polyvinylidene fluoride (PVDF) as the binder, with a mass ratio of 8:1:1. Copper foil was used as the current collector, and the electrode was coated with a 100-micron thickness. After drying at 60°C, circular electrode sheets with a diameter of 1.4 cm were cut. A sodium sheet with a diameter of 1.6 cm was used as the negative electrode, a glass fiber membrane as the separator, 1M NaPF6 as the supporting electrolyte, and DGME as the solvent to assemble a sodium|FeS2@C half-cell. At 0.1 A g... -1 0.2A g -1 0.5A g -1 1A g -1 ,2A g -1 5A g -1 10A g -1 and 20A g -1 Charge-discharge performance tests were conducted at the following rates, and the results are as follows: Figure 3 As shown, the results indicate that at a test temperature of 25℃ and 20A g... -1 A capacity of 248.7 mAh g can be achieved under the test current. -1 The discharge capacity; at -20℃ and 20A g -1 A capacity of 64.6 mAh g can be achieved under the test current. -1 The discharge capacity.

[0035] In 10A g -1 High-current, long-cycle testing was conducted at a current density of [value missing]. The results are as follows: Figure 4 As shown, the results indicate that 482.9 mAh g remains after 10,000 cycles. -1 Reversible capacity.

[0036] The processes and conditions for Examples 1-24 and Comparative Examples 1-7 are the same as those for Example 1, with the differences shown in Tables 1-3 below:

[0037] Table 1

[0038]

[0039]

[0040] Comparative example:

[0041] Table 2

[0042]

[0043] Performance Comparison Chart 3

[0044] Results Statement

[0045] Utilizing the characteristics of F127, which has hydrophilic and hydrophobic groups at both ends and a long chain in the middle, the hydrophilic groups exhibit electronegativity and bind with ferric iron (Fe3+), causing the ferric ions to form micellar particles under stirring conditions. The micellar structure of the long chain and the hydrophobic group at the other end prevents binding with other micelles, avoiding aggregation and resulting in higher dispersibility. Fe(NO3)3·9H2O, as the iron and nitrogen source, first forms micellar particles with F127 through electrostatic interaction, and then undergoes coordination polymerization with 1,3,5-phenyltricarboxylic acid. 1,3,5-phenyltricarboxylic acid can promote micellar assembly through van der Waals forces interacting with the hydrophobic ends of the surfactant; it can also enter the micelles to coordinate and recombine with metal ions, thus effectively controlling the particle size. Replacing the template agent with PVP, which has a non-uniform molecular weight, will result in non-uniform particle size, leading to deterioration in performance.

[0046] The preferred surfactant in this invention is F127, but other surfactants such as polyvinylpyrrolidone (PVP) and sodium hexadecyl sulfonate may also have the same effect. When other surfactants are used, micelle particles may not form first, but they can still act as a dispersant and template, and the formed particles may be larger, resulting in poorer rate performance.

[0047] In this invention, the preferred ligand is 1,3,5-benzenetricarboxylic acid, with a preferred mass ratio of 3:1 to 1:3 to Fe(NO3)3·9H2O. In a further embodiment, one or more of terephthalic acid and dimethylimidazole are selected. Experimental results show that the proportion of FeS2 in the final composite mainly depends on the amount of ferric ions; adding excessive amounts of iron salts or ligands does not significantly affect the experimental results. When 1,3,5-benzenetricarboxylic acid is replaced with 1,3,5-trimethylbenzene, micellar particles are also formed initially. 1,3,5-trimethylbenzene also promotes micelle assembly through van der Waals forces and interactions with the hydrophobic ends of the surfactant. However, due to the lack of organic ligands for the iron ions in the micelle particles, the particle size cannot be well controlled, resulting in larger particles and poorer performance. Furthermore, when 1,3,5-benzenetricarboxylic acid is added to the solution first, or when Fe(NO3)3·9H2O is dissolved together with F127 and dopamine hydrochloride, it may not form uniform micelle particles initially, resulting in larger average particle size and poorer overall performance. When 1,3,5-benzenetricarboxylic acid is replaced with terephthalic acid, the symmetrical structure of terephthalic acid causes the organic framework formed with iron ions to increase in size, leading to larger FeS2 particles and consequently, poorer performance.

[0048] In this invention, the preferred heating rate for the first step is 0.1–6 °C / min. -1 Since the formed particles are bonded by weak bonds, their structure may be damaged if the heating rate is too fast, eventually leading to larger particles and deteriorated performance.

[0049] In this invention, the preferred calcination temperature in the first step is 600–1000°C. Due to the influence of the carbonization temperature of the surfactants and organic ligands in the particles, the carbonization temperature needs to be greater than 600°C. Increasing the calcination temperature only affects the degree of graphitization of the calcined carbon and the data on its surface oxygen-containing groups, without significantly affecting the FeS2 content; therefore, the overall performance remains largely unchanged.

[0050] In this invention, the preferred calcination time for the first step is 1–12 hours. If the calcination time is too long, FeS2 particles may agglomerate, thus deteriorating the overall performance.

[0051] In this invention, the preferred heating rate in the second step is 0.1–6 °C / min. -1 If the heating rate is too fast, it may damage the structure, eventually leading to larger particles and deteriorated performance.

[0052] In this invention, the preferred calcination temperature in the second step is 200–800°C. When the calcination temperature is too high, it only affects the degree of graphitization of the calcined carbon and the data of oxygen-containing groups on its surface, but does not significantly affect the FeS2 content, so the overall performance remains largely unchanged.

[0053] In this invention, the preferred calcination time for the second step is 1–8 hours. If the calcination time is too long, FeS2 particles may agglomerate, thus deteriorating the overall performance.

Claims

1. A preparation method of FeS2@C alkali metal ion battery negative electrode material, characterized in that: 1) preparation of FeS2@C composite precursor: first, 4-0 g of F127 is dissolved in a mixture of 100 mL of water and ethanol with a volume ratio of 1:0-0:1 to obtain a solution; then, 0.5808 g-11.6166 g of soluble iron salt is added to the above solution under stirring to obtain a mixture solution; 1,3,5-benzenetricarboxylic acid with a molar ratio of 3:1-1:3 to metal ions is added to the above mixture solution, and after stirring for 20-60 minutes, the separated solid product is obtained by centrifugation, washed with a mixture of water and ethanol with a volume ratio of 1:0-0:1, and dried to obtain a polymer ball; 2) synthesis of FeS2@C composite material:

2. The preparation method according to claim 1, characterized in that: the soluble iron salt is one or more of Fe(NO3)3·9H2O, Fe(NO3)3, FeCl3, Fe2(SO4)3, FeSO4, Fe(NO3)2, and FeCl2; the sulfur source is one or more of sulfur powder and thiourea; and the inert atmosphere gas is one or more of Ar and N2.

3. The preparation method according to claim 1, characterized in that: 1) preparation of FeS2@C composite precursor: first, 1.5-0.5 g of F127 is dissolved in a mixture of 100 mL of water and ethanol with a volume ratio of 1:1 to obtain a solution; then, 0.58083 g-5.8083 g of soluble iron salt is added to the above solution under stirring to obtain a mixture solution; 1,3,5-benzenetricarboxylic acid with a molar ratio of 2:1-1:2 to metal ions is added to the above mixture solution, and after stirring for 30 minutes, the separated solid product is obtained by centrifugation, washed with a mixture of water and ethanol with a volume ratio of 1:1, and dried to obtain a polymer ball; 2) synthesis of FeS2@C composite material:

4. A FeS2@C alkali metal ion battery negative electrode material prepared by the preparation method of claim 1 or 2.

5. An application of the material of claim 4 as a negative electrode active material in an alkali metal ion battery. The obtained polymer spheres are heated at a heating rate of 0.1-6°C min -1 in an inert atmosphere to a calcination temperature of 600-1000°C, and calcined at the calcination temperature for 1-10h to obtain the precursor particles of the FeS2@C composite. The alkali metal ion battery is a lithium ion battery, a sodium ion battery, or a potassium ion battery. The precursor particles synthesized in step 1) and a sulfur source are mixed in a mass ratio of 1:1-1:4, heated to a calcination temperature of 200-800°C at a heating rate of 0.1-6°C min -1 in an inert atmosphere, and calcined at the calcination temperature for 1-8h, to obtain FeS2@C. ​ ​ ​ ​ ​ ​ ​ ​ The obtained polymer spheres are heated at a heating rate of 0.1-3°C min -1 in an inert atmosphere to a calcination temperature of 600-800°C, and calcined at the calcination temperature for 1-6h to obtain the precursor particles of the FeS2@C composite. ​ The precursor particles synthesized in step 1) and a sulfur source are mixed in a mass ratio of 1:1-1:2, heated to a calcination temperature of 300-600°C at a heating rate of 0.1-3°C min -1 in an inert atmosphere, and calcined at the calcination temperature for 3-6h, to obtain FeS2@C. ​ ​ 6. Use according to claim 5, characterized in that: ​

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