High-energy-density potassium ion battery realized by medium-entropy electrolyte suitable for alloy antimony / conductive carbon negative electrode

Abstract

The invention belongs to the field of organic electrolyte and potassium ion batteries, and particularly relates to a high-energy-density potassium ion battery realized by medium-entropy electrolyte applicable to an alloy antimony / conductive carbon negative electrode. The potassium ion battery comprises a Prussian blue (PB) positive electrode, an electrolyte and an antimony / conductive carbon (Sb / SP) negative electrode, and the electrolyte is a medium-entropy electrolyte of potassium bis (fluorosulfonyl) imide (KFSI). The obviously improved rate performance of the medium-entropy electrolyte and the Sb / SP developed by the invention is attributed to a balance solvation structure driven by a double-entropy effect and a weak solvation effect, and the structure provides a collaborative guarantee for enough interface stability and dynamic compatibility. Meanwhile, the electrochemical window of the ether-based electrolyte is widened, the PB positive electrode can stably circulate at 2.0-4.4 V, and the PBMSESb / SP total battery can achieve the high energy density of 194 Wh / kg under the current density of 50 mA / g (based on the total mass of PB and Sb / SP).

Description

A medium-entropy electrolyte suitable for alloyed antimony / conductive carbon anodes enables high-energy-density potassium-ion batteries. Technical Field

[0001] This invention belongs to the field of organic electrolytes and potassium-ion batteries, specifically relating to a medium-entropy electrolyte suitable for alloy antimony / conductive carbon anodes to achieve high energy density potassium-ion batteries. Background Technology

[0002] With the ever-increasing demand for clean energy, the development of low-cost, high-performance large-scale energy storage technologies is particularly important. Potassium-ion batteries (PIBs), with their abundant potassium resources, energy density comparable to lithium-ion batteries (LIBs), and excellent electrolyte ion transport kinetics, have become a promising energy storage technology. Regarding anode materials, although commercial graphite anodes can be applied to PIBs through a similar intercalation / delamination mechanism, their theoretical specific capacity is limited (only 279 mAh / g), and due to the high potassium ion (K... + The large radius of the cyclic material causes severe volume expansion and structural damage during cycling, resulting in poor cycling stability and limiting its large-scale application.

[0003] In contrast, antimony (Sb)-based alloy anodes are considered one of the most promising candidate anode materials due to their low operating potential, good ionic conductivity, and high theoretical specific capacity of 660 mAh / g. However, Sb-based anodes also face significant volume expansion during potassium intercalation and poor compatibility with conventional electrolytes, leading to high irreversible capacity loss and rapid capacity decay during cycling. To address these issues, existing technologies typically employ strategies such as nanostructuring, heterostructure design, composite material construction, and heteroatom doping. Among these, confining active Sb nanoparticles within a conductive carbon matrix (e.g., embedding them in hollow porous N-doped carbon nanotubes or MOF-derived carbon fibers) is a mainstream strategy. While this alleviates the volume effect and improves conductivity to some extent, structural optimization of the material itself alone cannot completely solve the interfacial side reaction problem.

[0004] Electrolyte compatibility design and solvation structure regulation are key to further improving the performance of Sb-based anodes, but existing technologies struggle to achieve both. Conventional dilute electrolytes (DEs) contain a large amount of free solvent, leading to an unstable SEI and poor cycle life. While high-concentration electrolytes (HCEs) improve interfacial stability by enhancing contact ion pairs (CIPs), their high viscosity results in low ionic conductivity, severely hindering transport kinetics. Further developments in locally high-concentration electrolytes (LHCEs) introduce inert diluents to reduce viscosity, but these diluents are typically expensive and have a limited selection, and their effect on improving ionic conductivity remains limited, failing to meet the practical requirements of high-performance batteries. Summary of the Invention

[0005] To address the shortcomings of existing potassium-ion battery electrolytes in balancing thermodynamic stability and ion transport kinetics, which leads to short cycle life and poor rate performance, and the fact that existing improvement strategies often involve high viscosity or high cost, this invention provides a medium-entropy electrolyte suitable for alloyed antimony / conductive carbon anodes to achieve high-energy-density potassium-ion batteries, thus solving the mismatch between ion kinetics and thermodynamics. In designing the multi-component ether-based electrolyte, the dual entropy effect and weak solvation effect achieve a balanced solvation structure of solvent-separated ion pairs (SSIPs) and CIPs, thereby enhancing ionic conductivity and lowering the desolvation energy barrier.

[0006] The purpose of this invention is to provide a medium-entropy electrolyte suitable for alloy antimony / conductive carbon anodes to achieve high energy density potassium-ion batteries.

[0007] The technical solution to achieve the purpose of this invention is:

[0008] The aforementioned medium-entropy electrolyte for achieving high energy density potassium-ion batteries using an alloy antimony / conductive carbon anode is characterized in that the potassium-ion battery comprises a Prussian blue cathode, an electrolyte, and an antimony / conductive carbon anode; the electrolyte is a medium-entropy electrolyte of potassium bis(fluorosulfonyl)imide (KFSI).

[0009] The aforementioned medium-entropy electrolyte for high-energy-density potassium-ion batteries using an alloy antimony / conductive carbon anode is characterized by the preparation of the antimony / conductive carbon (Sb / SP) composite material via a one-step ball milling method. Specifically, 2.1 g of antimony powder and 0.9 g of conductive carbon (Super P) are placed in a ball mill jar and milled at 700 rpm for 10 hours. To prevent antimony oxidation, the entire ball milling process is conducted under a nitrogen atmosphere, yielding black Sb / SP powder.

[0010] The aforementioned medium-entropy electrolyte for high-energy-density potassium-ion batteries using antimony alloy / conductive carbon anodes is characterized by the preparation of Prussian blue: Prussian blue (PB) is synthesized via a co-precipitation method. An aqueous solution (100 mL) containing potassium citrate (16 mmol) and ferrous sulfate heptahydrate (4 mmol) is added dropwise to an aqueous solution (100 mL) containing potassium hexacyanoferrate (4 mmol) at room temperature, stirred for 12 h, aged for 12 h, centrifuged, and dried under vacuum at 100 °C for 12 h to obtain PB.

[0011] The aforementioned medium-entropy electrolyte for high-energy-density potassium-ion batteries using antimony alloy / conductive carbon anodes is characterized by the use of a straight-chain ether-based ternary mixed solvent: dimethyl ether (DME), diethylene glycol dimethyl ether (G2), and tetraethylene glycol dimethyl ether (G4) as solvents, with a volume ratio of 1:1:1 for the three solvents in the mixed solvent.

[0012] The method for creating a high-energy-density potassium-ion battery using a medium-entropy electrolyte suitable for an alloy antimony / conductive carbon anode is characterized by the following electrolyte preparation: In an argon-filled glove box (water and oxygen content < 0.01 ppm), a certain amount of KFSI is added to a ternary mixed solvent, and after mixing and stirring evenly, a potassium-ion battery electrolyte is obtained: 3 mol / L (M) KFSI / DME+G2+G4 ​​(MSE).

[0013] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0014] The electrolyte of this invention, through a special solvation structure design, significantly improves ionic conductivity while effectively reducing the desolvation energy barrier of potassium ions. This balanced design ensures both rapid ion transport kinetics and thermodynamic stability of the electrode interface.

[0015] To address the problems of significant volume expansion and poor ion / electron transfer during cycling that are common in Sb-based K-storage anodes, resulting in high irreversible capacity and severe capacity degradation, this invention prepares an Sb / SP composite anode material using commercial antimony powder and SP conductive agent through a simple one-step ball milling process.

[0016] This invention, through the regulation of the electrolyte, when applied to the Sb / SP alloy anode, can effectively suppress the negative impact of volume expansion, while improving the interfacial stability and potassium storage kinetics of the Sb / SP anode.

[0016] This invention improves upon the limitations of conventional ether-based electrolyte voltage windows through an electrolyte optimization strategy. The optimized electrolyte enables the PB cathode to cycle stably at 2.0-4.4V.

[0017] This invention achieves long cycle life and excellent rate performance of PB||Sb / SP full cells, resulting in an energy density of 194Wh / kg for the full cells. Attached Figure Description

[0018] Figure 1. Adjustment of potassium ion transport number, ionic conductivity, and desolvation energy of electrolyte.

[0019] Figure 2. Raman spectra of the electrolyte with respect to FSI-.

[0020] Figure 3. Compatibility test of electrolyte with potassium metal.

[0021] Figure 4. X-ray diffraction pattern and thermogravimetric analysis diagram of the synthesized Sb / SP composite material.

[0022] Figure 5 shows the charge-discharge curves of the Sb / SP anode in different electrolytes and the performance comparison at a current density of 50 mA / g.

[0023] Figure 6 Comparison of rate performance of Sb / SP anode material in different electrolytes

[0024] Figure 7. Charge-discharge curves and capacity differential curves of Prussian blue cathode material in MSE.

[0025] Figure 8 Comparison of long-cycle and rate performance of PB||Sb / SP full cells assembled with electrolyte control at 50 mA / g current density. Detailed Implementation

[0026] The present invention will be further described below with reference to specific embodiments.

[0027] Example 1

[0028] A medium-entropy electrolyte suitable for an alloyed antimony / conductive carbon anode is disclosed for achieving high-energy-density potassium-ion batteries. The potassium-ion battery comprises a Prussian blue cathode, an electrolyte, and an antimony / conductive carbon anode; the electrolyte is a medium-entropy electrolyte of potassium bis(fluorosulfonyl)imide (KFSI). The specific steps are as follows:

[0029] The preparation method of Prussian blue cathode includes the following steps:

[0030] (1) Solution A preparation: Dissolve 16 mmol potassium citrate and 4 mmol ferrous sulfate heptahydrate in 100 mL of aqueous solution. (2) Solution B preparation: Dissolve 4 mmol potassium hexacyanoferrate in 100 mL of aqueous solution. (3) Subsequently, under vigorous stirring, solution A was slowly added dropwise to solution B. After stirring for 12 h, the mixture was aged for 12 h and washed three times each with deionized water and anhydrous ethanol. The collected solid was dried in a vacuum drying oven at 100 degrees Celsius for 12 h.

[0029] A method for preparing an antimony / conductive carbon anode includes the following steps: 2.1 g of antimony powder and 0.9 g of conductive carbon (SuperP) are placed in a ball mill jar and ground at 700 rpm for 10 hours. To prevent antimony oxidation, the entire ball milling process is carried out under a nitrogen atmosphere, yielding a black powder Sb / SP.

[0030] Electrode preparation: The negative electrode is loaded on copper foil with a ratio of Sb / SP: conductive carbon (Sp.): polyvinylidene fluoride (PVDF) = 7:2:1; the positive electrode is loaded on aluminum foil with a ratio of Prussian blue: conductive carbon (Sp.): polyvinylidene fluoride (PVDF) = 6:3:1.

[0031] The preparation of the medium-entropy electrolyte is as follows:

[0032] In a glove box filled with Ar (with moisture and oxygen content both less than 0.01 ppm), 1 mL of DME+G2+G4 ​​ether-based mixed solvent was added to an electrolyte bottle, followed by 3 mmol of KFSI. After mixing thoroughly, the entropy electrolyte (MSE) for the 3MKFSI / DME+G2+G4 ​​potassium-ion battery was obtained.

[0031] The preparation of low-entropy electrolyte is as follows:

[0032] In a glove box filled with Ar (with moisture and oxygen content both less than 0.01 ppm), 1 mL of DME ether solvent and 3 mmol of KFSI were added to an electrolyte bottle and mixed thoroughly to obtain a 3M KFSI / DME potassium-ion battery entropy electrolyte (LSE).

[0031] The preparation of high-entropy electrolyte is as follows:

[0032] In a glove box filled with Ar (with moisture and oxygen content both less than 0.01 ppm), 1 mL of a mixed solvent of DME+G2+G4+diethoxyethane (DEE)+diethylene glycol ethyl methyl ether (DEME) was added to an electrolyte bottle, followed by 3 mmol of KFSI. After mixing thoroughly, a 3M KFSI / DME+DEE+G2+DEME+G4 potassium-ion battery high-entropy electrolyte (HSE) was obtained.

[0033] Figure 1 shows the transport number of the electrolyte. Ionic conductivity (σ) and desolvation energy: The ionic conductivity of the traditional LSE is 8.37 mS / cm, the ionic conductivity of the MSE is significantly increased to 9.54 mS / cm, while the ionic conductivity of the HSE increases slowly to 10.28 mS / cm. LSE's... The value was 0.36, and MSE and HSE significantly improved to 0.66 and 0.68, respectively. Furthermore, K was introduced. + New conductivity parameter To more accurately assess ion transport kinetics in HCE. From From a visual perspective, entropy modulation has a more significant effect on enhancing ion transport dynamics. LSE's The value was 3.01 mS / cm, the MSE value doubled to 6.30 mS / cm, and the HSE value slowly increased to 7.00 mS / cm. The MSE exhibited the lowest desolvation energy at 35.98 kJ / mol, while the LSE was 48.53 kJ / mol and the HSE was 39.07 kJ / mol, indicating that the optimized MSE significantly improved interfacial kinetics. The MSE contained high σ and high... The combination with low desolvation energy ensures K +Rapid transport within bulk electrolytes and at interfaces lays a solid foundation for promising K-storage kinetics.

[0034] Figure 2 shows the Raman spectra of the electrolyte after adjustment, as well as the ratio of solvated structures and the solvent coordination number obtained after fitting. From the necessary relationship between solvated structures and potassium storage performance, an appropriate amount of SSIPs can ensure rapid ion transport kinetics in the bulk electrolyte, while sufficient anion-rich CIPs and AGGs can guarantee interfacial stability during potassium storage. The MSE electrolyte designed in this invention, dominated by SSIPs and CIPs solvated structures, is expected to achieve a balance between kinetics and stability during potassium storage.

[0036] Example 2

[0037] K||K cells were assembled using LSE, MSE, and HSE to investigate the stability of potassium deposition / stripping behavior in the electrolyte.

[0038] Using LSE, MSE, and HSE, Sb / SP anode materials, and potassium metal as counter electrodes, potassium-ion half-cells were assembled to study the potassium storage performance of the Sb / SP anode materials.

[0039] Example 3

[0040] Using MSE, Prussian blue ||K half-cells were assembled to study the potassium storage performance of Prussian blue in this electrolyte.

[0041] Prussian blue ||Sb / SP full cells were assembled using LSE, MSE, and HSE, and the potassium storage performance of the full cells in this electrolyte was studied.

[0042] The experimental results of potassium storage performance of potassium-ion half-cells obtained in Examples 1-3 above are as follows:

[0043] Figure 3 shows the effect at 0.1 mA / cm 2 Current density and 0.1 mAh / cm 2 Significant differences were observed in the potassium deposition / stripping curves of symmetric K||K cells cycled at their capacities. Both LSE and MSE showed stable cycling for over 300 hours, while HSE exhibited a large overpotential from the initial stage and could not maintain stable cycling. Furthermore, the symmetric cell using LSE exhibited higher overpotential, more drastic fluctuations, and more severe asymmetry during cycling, indicating that MSE has stronger compatibility with the potassium deposition / stripping electrochemical reaction.

[0044] Figure 4 shows the X-ray diffraction pattern and thermogravimetric analysis (TGA) of the synthesized Sb / SP composite material. The X-ray diffraction pattern shows that antimony exists in the composite material in a metallic state and no impurities were detected. Based on reaction stoichiometry, the Sb content in the Sb / SP composite material can be calculated to be 64.1 wt.%.

[0045] Figure 5 shows the charge-discharge curves of the Sb / SP anode in different electrolytes and a performance comparison at a current density of 50 mA / g. Figure 5a shows the galvanostatic charge-discharge (GCD) curves of the Sb / SP anode in MSE, LSE, and HSE at a current density of 50 mA / g. A significant voltage plateau is observed in MSE, while the GCD curves of LSE and HSE show lower specific capacities and no significant plateau. Furthermore, the charge-discharge potential difference in MSE is smaller than that in LSE or HSE, indicating that MSE has low overpotential potassium storage characteristics. These optimized potassium storage characteristics enable a stable and reversible alloying / dealloying potassium storage process in the optimized MSE electrolyte, resulting in a potassium storage specific capacity as high as 454.3 mAh / g (336.5 mAh / g for LSE electrolyte and 356.6 mAh / g for HSE electrolyte). The long-term cycling performance of the Sb / SP anode further reveals the significant difference in the influence of electrolyte on potassium storage behavior. As shown in Figures 5b and 5c, the discharge specific capacity of the Sb / SP anode in LSE and HSE electrolytes significantly decays during long-term cycling. In contrast, the Sb / SP anode in MSE electrolyte maintains a high discharge specific capacity of 426.4 mAh / g after 486 cycles, with a capacity decay rate of only 0.014% / cycle from the second cycle onwards. The improved potassium storage stability of the Sb / SP anode in MSE electrolyte strongly demonstrates its high compatibility and matching performance with the MSE electrolyte, attributed to the balanced solvation structure driven by the double entropy effect and weak solvation effect.

[0045] Figure 6 shows a comparison of the rate performance of the Sb / SP anode material in different electrolytes. As the current density increases from 50 to 100, 300, 500, and 800 mA / g, the specific capacity of the Sb / SP anode in the MSE electrolyte slowly decreases from 418.6 mAh / g to 387.7, 327.4, 244.1, and 164.6 mAh / g, respectively. When the current density decreases to 50 mA / g, the capacity recovers to 416.7 mAh / g. In contrast, the Sb / SP anodes in HSE and LSE exhibit significant capacity decay with increasing current density. Specifically, at a high current density of 800 mA / g, only low specific capacities of 42.1 and 12.4 mAh / g can be maintained in HSE and LSE, respectively. The significantly improved rate performance of Sb / SP in the MSE electrolyte is attributed to the balanced solvation structure, which provides a synergistic guarantee of sufficient interfacial stability and kinetic compatibility.

[0046] Figure 7 discusses the charge-discharge curves and capacity differential curves of the Prussian blue cathode material in MSE. The GCD curve of the third cycle, shown in Figure 7a, at a current density of 50 mA / g, exhibits a clear voltage plateau, with a reversible discharge capacity reaching 80 mAh / g. The corresponding dQ / dV curve (Figure 7b) clearly shows two pairs of redox peaks, located at 3.51 / 3.18 V and 3.22 / 2.86 V, respectively, corresponding to low-spin and high-spin Fe²⁺ peaks. 2+ / 3+ The redox pairs indicate the existence of a two-electron transfer mechanism. Furthermore, these high-voltage platforms effectively ensure that the full cell achieves a competitive operating voltage, thereby realizing high energy density.

[0047] Figure 8 shows a comparison of the long-cycle and rate performance of PB||Sb / SP full cells assembled with different electrolytes at a current density of 50 mA / g. As shown in Figure 8a, the PB||MSE||Sb / SP cell exhibits excellent cycle stability, maintaining stable operation for over 400 cycles. In the LSE electrolyte, the full cell can only cycle stably for 300 cycles, after which the charge-discharge performance drops significantly; while in the HSE electrolyte, its cycle life is shortened to 20 cycles. These results indicate that MSE has higher compatibility with PB cathodes and Sb / SP anodes compared to LSE and HSE. As shown in Figure 8b, the rate performance of full cells using different electrolytes was also evaluated. At current densities of 50, 100, 200, 400, and 800 mA / g, the MSE electrolyte cells exhibited specific capacities of 70, 60, 46, 32, and 20 mAh / g, respectively. It is worth noting that when the current density drops to 50 mA / g, its capacity can recover to approximately 70 mAh / g. The MSE-based full cell achieves a high energy density of 194 Wh / kg at a current density of 50 mA / g (based on the total mass of PB and Sb / SP), and retains more than 50% of its energy density value even at a high current density of 400 mA / g.

Claims

1. A medium-entropy electrolyte suitable for alloy antimony / conductive carbon anodes to achieve high energy density potassium-ion batteries, characterized in that, The potassium-ion battery includes a Prussian blue cathode, an electrolyte, and an antimony / conductive carbon anode; the electrolyte is a medium-entropy electrolyte of potassium bis(fluorosulfonyl)imide (KFSI).

2. The high-energy-density potassium-ion battery using a medium-entropy electrolyte with an alloy antimony / conductive carbon anode as described in claim 1, characterized in that... Preparation of Antimony / Conductive Carbon (Sb / SP): Antimony / conductive carbon composite material was synthesized via a one-step ball milling method. Specifically, 2.1 g of antimony powder and 0.9 g of conductive carbon (Super P) were placed in a ball mill jar and milled at 700 rpm for 10 hours. To prevent antimony oxidation, the entire ball milling process was carried out under a nitrogen atmosphere, yielding a black powder, Sb / SP.

3. According to claim 1, the medium-entropy electrolyte for realizing a high-energy-density potassium-ion battery using an alloy antimony / conductive carbon anode is characterized in that... A straight-chain ether-based ternary mixed solvent was selected: dimethyl ether (DME), diethylene glycol dimethyl ether (G2), and tetraethylene glycol dimethyl ether (G4) as solvents, with a volume ratio of 1:1:1 for the three solvents in the mixed solvent.

4. The high-energy-density potassium-ion battery using a medium-entropy electrolyte with an alloy antimony / conductive carbon anode as described in claim 1, characterized in that... Preparation of electrolyte: In a glove box filled with argon (water and oxygen content < 0.01 ppm), a certain amount of KFSI was added to a ternary mixed solvent and mixed and stirred evenly to obtain potassium ion battery electrolyte: 3 mol / L (M) KFSI / DME+G2+G4 ​​(MSE).

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