Electrospun PAN membranes strengthened in situ–grown TiO2 particles for high-performance lithium-ion batteries

An in situ–grown TiO2 membrane was prepared by an electrospinning method using polyacrylonitrile as the spinning precursor, combined with the TiO2 hydrolysis mechanism. The performance of tetrabutyl titanate and isopropyl titanate as two titanium source precursors hydrolyzed under the inhibition of acrylic acid to produce TiO2 with different contents for lithium-ion batteries was compared. The experimental results showed that when both titanium sources were prepared at 3 wt%, the comprehensive performance of the separator manufactured with tetrabutyl titanate as the titanium source (PAN/TBT-3) and isopropyl titanate as the titanium source (PAN/TPT-3) was finest than that of the Celgard 2400 and the composite membrane with direct TiO2 addition (PAN/TiO2-3). The tensile strength of PAN/TPT-3 and PAN/TBT-3 membranes were 7.82 MPa and 4.03 MPa higher than that of Celgard 2400, and 17.03 MPa and 13.29 MPa higher than that of PAN/TiO2-3 separator, respectively. PAN/TPT-3 and PAN/TBT-3 membranes exhibited a discharge capacity of 107.72 mAh/g and 115.79 mAh/g at 2 C, and both the capacity retention rate was above 99.5% higher than 80.5% for Celgard 2400.


Introduction
With the gradual development of new energy, lithium-ion batteries were paid extensive attention to energy storage equipment in the market for LIB separators [1].However, there is an urgent demand for high-density, safe, and longcycle life high-energy storage equipment.The battery separator is a critical component isolating the anode and cathode, which holds a balancing role in safety.Celgard 2400, a common choice, showed serious shrinkage in unidirectional stretching under heating, causing safety accidents [2].In recent years, electrospinning technology, which can control the process characteristics such as fiber diameter, orientation, and structure, has become one of the most important means to prepare porous nanofiber membranes [3].Based on the simply staggered lap of electrospinning fibers, the mechanical strength was not ideal in batteries, which is a major problem for electrospinning separators.Inorganic particles to refine the fiber diameter and increase the specific surface area were currently a mainstream way to strengthen the fiber.However, how to make it uniformly dispersed is the main problem limiting its current development.Owing to its chemical stability, diversity in structure, and diversity in preparation methods, TiO 2 is a common addition for modified fibers, which are often used as a strength toughener for battery separators [4][5][6].Thus, we introduced the titanium source directly into the precursor and use the subsequent hydrolysis treatment to grow titanium dioxide in situ.Benefiting from the diversity of spinning a material selection of electrospinning characteristics, the addition of inorganic particles to the spinning precursor liquid can increase the strength of fibers [7][8][9].TiO 2 usually served as a photocatalyst and to improve strength, which was attributed to its chemical stability and strong polarity, directly introducing in situ growth of TiO 2 particles for PAN fiber strength modification, which greatly coped with the problem of agglomeration and realized the increase of fiber strength.At present, fiber membranes were prepared from polymers such as polyacrylonitrile (PAN) [10] and poly(vinylidenefluoride) (PVDF) [11] and polyurethanes (PUs) [12] obtained by free radical polymerization of acrylonitrile monomer.PAN molecular chain had a polar − CN group, and raw material chemical resistance and oxidation resistance were fine, combined with the merits of electrospinning technology with high porosity, large liquid absorption, small internal resistance, excellent battery charge, and discharge performance together prepared to meet applicant of batteries.Using in situ growth synthesis of inorganic particles not only addressed the issue of dispersion of inorganic particles but also was a simpler preparation method compared with other hydrothermal methods or CVD synthesis, and low-temperature preparation of inorganic particles can be achieved [13].
Herein, acrylic acid was used instead of hydrochloric acid as a hydrolysis corrosion inhibitor; the former organically combined with PAN, effectively promoting the reaction and reducing the amount of white flocculation.Isopropyl titanate and tetrabutyl titanate were explored as titanium sources for the synthesis of TiO 2 and discussed their impact on battery separators.The unsaturated surface atoms on the generated TiO 2 surface were prone to interact with polymer molecular chains, and most inorganic particles directly added to TiO 2 only adhere to PAN fibers, which improved the electrochemical performance of the electrospinning separators [14].

Preparation of electrospun membranes
The preparation of titanium dioxide membranes was fabricated via electrospinning and was simply captioned as follows.First, the 8.7 g PAN was dissolved in 1.3 g DMF mixed with 13% homogenous precursor via magnetic stirring for 5 h at 50 °C.Thereafter, varying amounts of acrylic acid, as a hydrolysis reliever, were added into the PAN precursor and stirred until there was no white flocculent substance.Subsequently, the mixture was introduced, butyl titanate (TBT) and titanium tetraisopropanolate (TPT), and stirred at room temperature for 12 h.Finally, the PAN precursor carrying the different titanate sources was transferred into a syringe mounted in an electrospinning machine (E05, Foshan Lepton Precision Measurement and Control Technology Co. Ltd., China).At constant voltages of + 28 kV and -2 kV, a syringe mounted on a pusher pump injects spinning solution at 0.6 mL/h onto a receiver drum rotating at 300 rpm.Moreover, spinning at 25 °C and a humidity of 40 for 5 h, a uniform membrane of uniform thickness was obtained.Electrospun fibers were collected and placed at 80 ℃ for 24 h oven with sufficient deionized water for 24 h to ensure that the in situ growth reaction occurred completely to fully hydrolyze to generate TiO 2 and then evaporated to water and DMF at 80 ℃.The resultant electrospun membranes were cut into a circular shape with a diameter of 19.6 mm, and they were marked as PAN/TBT-x (titanate source from butyl titanate added), PAN/TiO 2 (directly TiO 2 particle added, PAN/TPT-x titanate source from titanium tetraisopropanolate addition), where x was 1, 2, 3, 4, and 5.
The principle of hydrolysis of tetrabutyl titanate as a titanium source to produce titanium dioxide was as follows: The principle of hydrolysis of tetraisopropyl titanate as a titanium source to produce titanium dioxide was as follows:

Electrolyte uptake
The membrane electrolyte uptake can be calculated using Eq. 1.
where W 0 was the initial weight of the dried membrane and W 1 was the weight of the separators after immersing 1 M LiPF 6 electrolyte solution (solvent was EC/DEC = 1:1 v/v) for 6 h.

Porosity
The membrane porosity was calculated using Eq. 2.
W a was the weight of the dried membrane, W b was the weight of the separators after soaking in n-butanol solution for 4 h, and ρ was the density of n-butanol.A was the membrane area, and h was its thickness.

Mechanical properties
The mechanical properties of different membranes were measured by using a universal stretching machine (SANS CMT6104, Meister Industrial Systems Co. Ltd., China) and were evaluated at a stretching speed of 10 mm/min and a gauge distance of 25 cm.

Crystalline structure
X-ray powder diffraction (XRD) (D2 PHASER, Bruker, Germany) was delivered to identify the crystalline structure of the composite membranes.

Thermal properties
Membrane samples were incised to form disks with the same diameter of 19.6 mm and were vacuum-dried at different temperatures (100-180 °C) for 2 h to determine the thermal shrinkage.The thermal stability was performed by thermogravimetric analysis-differential scanning calorimetry (TGA-DSC 200F3, Netzsch, Germany) at a heating rate of 10 ℃/min under N 2 from 30 to 800 °C and a frequency of 1 Hz.

Electrochemical window
The batteries were operated from a stainless-steel sheet (SS) and Li, which was measured by an electrochemical station (CHI660E, Shanghai Chenhua Instrument Co. Ltd., China) to judge the electrochemical stability at a scanning speed of 1 mV/s within a voltage window of 3-6 V.

Ionic conductivity
The ionic conductivity tests were measured by a symmetric battery assembled with two stainless steel electrodes under frequencies ranging from 1 to 100,000 Hz at an amplitude of 5 mV.The membrane bulk resistance (R b ) value was estimated by the intercept of curves in a Nyquist diagram on the x-axis, and the ionic conductivity (σ) was calculated by Eq. 3.
The membrane thickness and area were on behalf of h and S, respectively.

Interface impedance
The battery of interface impedance was obtained from the assembly of a symmetric lithium battery and was conducted by electrochemical impedance spectroscopy (EIS) tests at an amplitude of 5 mV within the frequency range of 1-100,000 Hz.

Electrochemical performance
The CR 2032 batteries coated on different separators (LiFePO 4 /separator/Li anode, 1 M LiPF6 of solvent was EC/ DEC = 1:1, v/v) were assembled in an argon-filled glove box (UN750S, Chengdu Delis Industrial Co. Ltd., China).The electrochemical performance of the CR 2032 batteries, in which the voltage ranged from 2.5 to 4.2 V, was evaluated at various current densities from 0.2 C, 0.5 C, 1 C, 2 C, and 0.2 C, using a Neware battery test system (BOA-BTS-7.431DS, Shenzhen Neware Electronics Co. Ltd., China).

Influence of acid type and amount on morphology and properties
However, preliminary experiments have evidenced that filaments prepared with acrylic acid (AA) as hydrolysis inhibitors are not strong enough and are prone to gel formation during spinning [15].Compared with HCl, which is commonly used but insoluble in organic systems, AA, as a monomer for the synthesis of polyacrylonitrile polymers, can be better embedded in the system and become a more satisfactory hydrolysis inhibitor.
The SEM morphology of membranes with different acids was given in Fig. 1.There are the fibers that showed an apparent difference in diameters and morphology.It can be clearly seen that the diameter is uneven from Fig. 1a and that the fibers were not stretched enough to form silk. Similarly, the addition of acetic acid easily caused brittle fibers and owned to insufficient tensile strength in Fig. 1c.The coarse subdivision of fibers prepared by acrylic acid as hydrolysis inhibitor is uniform, as shown in Fig. 1b, and in a good silk-forming state.The reason was mainly owing to the fact that organic acids such as acrylic acid can react with PAN to enhance solubility so that the bonding power of the fiber was also improved.Therefore, acrylic acid is well selected as an in situ growth inhibitor of TiO 2 in the PAN precursor.
Further experiment results suggested that the amount of inorganic salt caused the tangling and erection of fibers, which made it difficult to collect [16].Therefore, it was an urgent demand to tightly control the amount of acid to synthesize 3 wt% TiO 2 using tetrabutyl titanate as the precursor of titanium source.The bulk impedance of the membranes with different amounts of acrylic acid was depicted in Fig. 2a.Surprisingly, in both n-butyl titanate and isopropyl titanate, when the amount of acrylic acid added is 1 wt% of the total precursor compared to 2 wt%, it showed a smaller bulk resistance [17].A smaller bulk resistance indicated that the membranes behaved with superior ionic conductivity and have an improved electrochemical performance.Therefore, the amount of acrylic acid and 1 wt% of the total amount of precursors were selected for the in situ growth of titanium dioxide in subsequent experiments.
Under the above conditions, tetrabutyl titanate and isopropyl titanate as titanium sources were in situ growth TiO 2 was a membrane with a precursor content of 1 wt%, 2 wt%, 3 wt%, 4 wt%, and 5 wt%.The SEM morphology of PAN/TPT-x (Fig. 3), PAN/TBT-x (Fig. 4), and PAN/TiO2-3(Figs.2f or 3f) was displayed.As depicted in Figs.3a-e and 4a-e, fibers were stretched into silk under these conditions and, when the amount of addition was less or too much such as 1 wt% or 5 wt%, were not stretched sufficiently and had an uneven diameter distribution.While the synthesis amount was 2, 3, and 4 wt%, the uniform distribution of the filaments and the fine particles on the filaments can be seen.Comprehensive follow-up tests showed that when 3 wt% TiO 2 was synthesized, the fiber morphology and performance were excellent, compared with the electrospun diaphragm directly added with 3 wt% TiO 2 .Figure 3f found that the direct addition of 3 wt%, due to the addition amounts of uneven dispersing inorganic particles, resulted in more aggregates and defects in the fibers, where more stress concentration points occurred, resulting in reduced strength.
In summary, contrasted to the spectra of TiO 2 and a reference particle (PDF#21-1272) in Fig. 5.The crystal structure of TiO 2 was not changed.PAN, as a semicrystalline polymer, was given a diffraction peak at 2θ = 16°, which was shown as the same diffraction peak in PAN/TBT-3 and PAN/TPT-3.TiO 2 does not vary the crystal structure of PAN; meanwhile, three main diffraction peaks were slightly shifted to 2θ = 25.28°,37.8°, and 48.05°, corresponding to the crystal planes (101), (004), and (200).A small number of particles were visible in Figs.3c and 4c, indicating that TiO 2 was indeed synthesized.But it was worth noting that the diffraction peaks were weaker, which mainly contributed to the rapid hydrolysis rate of tetrabutyl titanate, the imperfect crystal structure, and the unstable crystal form of the inorganic particles formed by it.At the same time, the subsequent weak peak was not obvious, mainly accounting for TiO 2 being mostly distributed inside the filament, and the overall amount of production was small, which made it difficult for X-rays to be fully transmitted.Figure 5b shows the Raman diagram of the TiO 2 septum, combined with the XRD spectrum, and confirms that rutile TiO 2 is indeed present in the fiber septum.And the TiO 2 crystalline formations formed due to isopropyl titanate are complete, and the strong peaks are more obvious.
High porosity determined electrolyte uptake by membranes, which together guaranteed the electrochemical performance of lithium-ion batteries.Excellent porosity and electrolyte uptake were attributed to providing more Li + channels and accelerating the migration of Li + through the membrane [18].The porosity and electrolyte uptake of PAN/TBT-x (Fig. 6a) and PAN/TPT-x (Fig. 6b) tended to increase.When x was 3 wt%, the porosity and electrolyte uptake of PAN/TBT-3 and PAN/TPT-3 membranes displayed superior to that of Celgard 2400 and PAN/TiO 2 -3 (Fig. 7a).However, with the excessive addition of inorganic salts, there will be a downward trend, as was shown in Fig. 6.The electrolyte uptake of PAN/TBT-3 and PAN/TPT-3 can reach 503% and 467%, respectively, which was 4.57 times and 4.24 times higher than that of Celgard 2400 and 2.87 times and 2.67 times higher.While those porosities reached 76% and 71%, respectively, it is 2.45 times and 2.30 times higher in that of Celgard 2400 and 1.95 times and 1.82 times higher in that of PAN/TiO 2 -3 separator.As indicated in Fig. 7a, adding 3 wt% TiO 2 covered too much pore area, which led to lower porosity and electrolyte uptake in the PAN/TiO 2 -3 membrane.
Poor strength of the electrospun separators limits the applicant in batteries [19,20].The intricate fiber structure not only improved the fibers' strength but also guaranteed excellent porosity.Adopting the in situ growth of TiO 2 and PAN molecular chain mosaic on the fiber matrix, under the action of external force, the particles will be difficult to come off the matrix.This way can better conduct the internal stress, increase the consumption of impact energy, and thus enhance the maximum tensile strength that the membranes can withstand.A maximum membrane strength is required to withstand puncture due to lithium dendrites, which was associated with the useful life of the membrane [21][22][23][24], as illustrated in Fig. 7b.The strength PAN/TBT-3 (18.55 MPa) exhibited a beetling performance, higher PAN/TPT-3 (22.28 MPa), and as higher as PAN/TiO 2 -3 (5.26 MPa).
Table 1 showed the tensile strength properties of two different titanium sources with different titanium dioxide contents and the tensile strength of directly added TiO 2 particles.The comparative analysis found that the excessive addition of inorganic salts (x = 4, 5) led to a brittle membrane and sharply decreased tensile strength, which proved that an appropriate addition can not only improve the mechanical performance but also prevent the membrane from becoming brittle.
The horizontal and longitudinal tensile strength of the Celgard 2400 varied greatly due to the production process, and the transverse tensile was generally 12 ~ 18 MPa, while the longitudinal tensile could arrive around 100 ~ 120 MPa [25].

Thermal performance
As shown in Fig. 8, the composite membranes are placed in a vacuum oven at 100, 140, and 180 °C for 2 h.The whole membranes retained their original dimensional at 80 °C, indicating safety at this temperature.Based on the reason that a notable difference in tensile strength in the transverse and longitudinal directions, Celgard 2400 was susceptible to heat and curling in one direction, as demonstrated at 140 °C and 180 °C shown in Fig. 8. Celgard 2400 curled in the longitudinal direction and shrink in dimension after 80 °C, which led to the positive and negative electrodes that tend to come in contact with each other, arousing short circuit [26,27].
Contrastively, the thermal property results of electrospun PAN/TBT-x and PAN/TPT-x membranes did not appear to shrink in dimension at high temperatures.Although for the case of PAN/TiO 2 -3, there was gentle area shrinkage but was still smaller than Celgard 2400.The thermal dimensional  stability of the battery separator played a matter impact in guaranteeing the safety of batteries [28].Therefore, excellent heat resistance and dimensional stability were critical to the safety of the battery.Overall, when x was 3 wt%, the PAN/TBT-3 and PAN/TPT-3 with excellent thermal stability were a superior choice for safety batteries.Due to the uniform interaction between stress points for absorbing most of the energy TiO 2 in the fibers inside the matrix, the overall thermodynamic properties of the composite were enhanced.Figure 9 depicted the DSC curves and TGA curves about PAN/TBT-3, PAN/TBT-3, PAN/TiO 2 -3, and Celgard 2400.Celgard 2400 had an endothermic peak at 161 ºC in Fig. 9a, which explained the shrinkage at 140 ºC and transparency at 180 ºC.Compared with the PAN membrane, PAN/TBT-3 and PAN/TPT-3 had a higher melting temperature for the preserver of TiO 2 .Accordingly, PAN/TPT-3 exhibited a slightly higher degradation temperature at 332 ºC, since TiO 2 crystals were more stable and easier to grow in situ in TPT systems [29,30].As was shown in Fig. 9b, the weight retention rate of PAN/TPT-3 (42.24%) was close to PAN (41.85%), while PAN/TBT-3 (50.03%) was as high as PAN, and the whole Celgard 2400 was higher (about 100%).Celgard 2400 beginning to thermally decompose at 410 ºC fails to sever as a separator to isolate the positive and negative electrodes when the mass loss reached 100% at 500 ºC, resulting in short-circuiting and thermal runaway and inducing safety accidents.A higher melting point can guarantee the stability of the membrane, which was conducive to ensuring the safety of batteries.

Electrochemical performance
Generally, the electrochemical stability of membrane separators assembled in a battery (SS/separator/Li) is determined by linear sweep voltammetry, which required its electrochemical window above 4.5 V to maintain better stability during use.It was known from Fig. 10a, b that the electrochemical stability window of the PAN/TBT-x and PAN/TPT-3 electrospun separator was higher than that of the Celgard 2400, mainly due to PAN as the supporting skeleton and TiO 2 surface oxygen combined with lithium ions, indicating composite separators owned better electrochemical stability.Moreover, the decomposition voltage of PAN/TBT-3 and PAN/TPT-3 composite separators can reach 4.7 V and 5.3 V, respectively, which was higher than the 4.1 V of the contrast membrane Celgard 2400 and the 4.37 V of the PAN/TiO 2 -3 separator.The string agglomerates on the fibers of the PAN/TiO 2 -3 separator made them prone to free inorganic particles and were considered insulating impurities, resulting in a narrow battery electrochemical stability window.Hence, the composite membranes had better electrochemical stability, which was sufficient for use in batteries.
The bulk independence (R b ) of PAN/TPT-x, PAN/TBT-x, PAN/TiO 2 -3, and Celgard 2400 membrane survived via EIS trial and was obtained from the intercept of AC impedance curves at the x-axis in Fig. 11c, d.Table 1 lists data on R b and the conductivity of different membranes.Introducing TiO 2 particles to electrospun membranes can indeed reduce R b .The R b of PAN/TBT-3 was 4.32 Ω while that of PAN/ TPT-3 was below 2.20 Ω, and both were lower than PAN/ TiO 2 -3 (6.74 Ω) and Celgard 2400 (6.91 Ω).
The lower R b of PAN/TBT-3 and PAN/TPT-3 guaranteed more excellent inion conductivity.At the same time, the high porosity of the membranes indicated that the porous fiber membrane could provide more mobile channels for lithium ions and enhance the ion migration rate.As listed in Table 1, the ionic conductivity of the PAN/TBT-3 separator was 3.12 mS/cm, and the PAN/TPT-3 separator was 8.03 mS/cm, which was 4.18 times and 1.63 times that of the Celgard 2400 and 3.63 times and 1.41 times that of the PAN/TiO 2 -3 separators.
The two different titanium sources were hydrolyzed into TiO 2 membranes at the current densities of 0.2 C, 0.5 C, 1 C, 2 C, and 0.2 C for 10 cycles, as shown in Fig. 11a,  b.The performance was unstable due to possibly insufficient electrolyte infiltration in the first ten turns, showing a trend of first rising and then fully infiltrating by electrolysis and then steadily declining.When the synthesis of titanium dioxide was 3 wt%, PAN/TBT-3 and PAN/TPT-3 separators showed excellent electrochemical performance at various rates.Moreover, the discharge-specific capacity of PAN/TBT-3 and PAN/TPT-3 separator can reach 140.99 mAh/g and 158.29 mAh/g at 0.2 C, which was higher than that of Celgard 2400 of 129.79 mAh/g, and higher than that of 129.72 mAh/g of PAN/TiO 2 -3 separators with more filament defects.With increasing charge rate, the discharge capacity of the batteries with different membrane separators decreased.After high current discharge, the membrane exhibited an outstanding reversible capacity that restored the charge to the initial low rate of 0.2 C to complete the test, and PAN/TBT-3 and PAN/ TPT-3 membranes still showed excellent rate performance.
The poor cycling performance of the latter two was mainly due to their porosity and liquid uptake, which cannot provide more Li + shuttle channels.The first discharge-specific capacity PAN/TBT-3 and PAN/TPT-3 batteries were not high with a current density at 2 C for 50 cycles, as depicted in Fig. 11c,  d, contributed to electrolyte infiltration problems in the early stage, and first slowly increased and then decreased to stability [11].The battery with PAN/TBT-3 and PAN/TPT-3 separator behaved with a discharge-specific capacity of 107.72 mAh/g and 115.79 mAh/g; meanwhile its capacity retention rate was above 99.5%.The electrospun separators added into TiO 2 can enhance the interface stability and avoid the formation of SEI film, whose capacity retention rate was higher than 80.5% of the commercial separator Celgard 2400, as well as also higher than the capacity retention rate of 97.86% of PAN/ TiO 2 -3 separator [31].
Figure 12 displayed the electrochemical impedance spectra of a symmetric Li/Li battery with PAN/TBT-3, PAN/TPT-3, PAN/TiO 2 -3, and Celgard 2400.TiO 2 particles with free oxygen-containing groups induced the electrospun membrane to have excellent wettability of electrolytes and promoted the efficiency of oxidation reaction between the electrolyte and lithium ions.However, the excessive addition of PAN/TiO 2 -3 separator had abundant interface impedance due to excessive free particle impurities.Thus, the interface resistance (Z′) of PAN/TPT-3 was 232 Ω, which was the lowest.PAN/TBT-3 was the next lowest (262 Ω), followed by Celgard 2400, with PAN/TiO 2 -3 (384 Ω) investigating the highest interface resistance of 364 Ω.The dominant interfacial compatibility of PAN/TPT-3 and PAN/TBT-3 met satisfactorily the three components in the battery, which was expected to reduce ohmic polarization to attain excellent ionic conductivity [32].

Conclusions
In summary, the discussion of the dispersion of inorganic particles was addressed by directly growing TiO 2 in situ in PAN precursor solution.The experiment found that the dosage had a great influence on the separator.When the production of TiO 2 was small, the properties of fiber membranes were gradually increasing, but with the excessive addition of inorganic salts, there was a downward trend.By comprehensive comparison, when synthesizing 3 wt% TiO 2 , the comprehensive properties of fibers membranes, called PAN/TBT-3 and PAN/TPT-3, had been improved to varying degrees compared with Celgard 2400 and PAN/ TiO 2 .Specifically, the mechanical properties of the separator can be increased to 18.55 MPa and 22.28 MPa, respectively.The outstanding porosity, nailing electrolyte uptake and excellent exceeding thermal dimensional stability, was obtained from PAN/TBT-3 and PAN/TPT-3.The decomposition voltage reached 4.7 V and 5.3 V, respectively higher than PAN/TiO 2 -3 and Celgard 2400.After 50 cycles at 2 C, the PAN/TBT-3 and PAN/TPT-3 separators had dischargespecific capacities of 107.72 mAh/g and 115.79 mAh/g, respectively, and their capacity retention rates were above 99.5%, while capacity retention rate of Celgard 2400 was only 80.5%.Compared with isopropyl titanate and tetrabutyl titanate, the slower hydrolysis rate of the former contributed to forming stable crystals of inorganic particles, inducing significant performance improvement.The synthesis of inorganic particles directly in the precursor liquid, contrasted to the direct lamp to add inorganic particle membranes, effectively addresses the problem of agglomeration and simple operation and had certain fiber reinforcement application prospects.

Fig. 1 Fig. 2
Fig. 1 SEM images of different membranes introduced by different hydrolysis inhibitors.a Without acid, b acrylic acid, and c hydrochloric acid

Funding
Author contribution LT and YW wrote the main manuscript text; ZL prepared Figs.1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, and 12; and YH and JC offered funding acquisition.All authors have read and approved the manuscript.This work received funding from the Scientific and Project of Sichuan Province (E10106093) and the Project of Zigong High-Tech Zone Science and Technology Service Industry Cluster Construction (2021KJFWY010).

Table 1
The membranes of ion conductivity and tensile strength