Solid polymer electrolyte for lithium batteries

Abstract

The application belongs to the technical field of batteries, and particularly relates to a solid polymer electrolyte for a lithium battery. First, common coconut shell fibers are used as carriers, which are low in price and low in cost. Then, the adsorption capacity of the coconut shell fibers for lithium ions is enhanced in a porous manner. Finally, lithium ion-filled porous activated carbon powder is obtained through carbonization. The solid polymer electrolyte prepared in the application is added with the lithium ion-filled porous activated carbon powder, which can greatly improve the lithium ion transmission efficiency of the solid polymer electrolyte, thereby improving the ionic conductivity.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of batteries, and particularly relates to a solid polymer electrolyte for a lithium battery. BACKGROUND

[0002] The lithium ion battery electrolyte is mainly divided into electrolyte and polymer electrolyte. The electrolyte is mainly composed of high-purity organic solvent, lithium salt and some functional additives with modification effect. The positive and negative ions can be dissolved in the electrolyte and quickly migrate, so that the electrolyte has good conductivity. Therefore, the electrolyte is mainly used in commercial lithium batteries. However, the electrolyte also has some problems, such as: the electrolyte limits the shape of the lithium battery, cannot make a flexible battery, and limits the application range of the lithium ion battery; the electrolyte has high cost and is easy to leak, and will explode under impact and high temperature, which has serious safety hazards. In order to solve these problems of the electrolyte, scientists begin to study the polymer electrolyte which is safer and has better performance to replace the traditional electrolyte and prepare a practical polymer lithium ion battery.

[0003] The solid polymer electrolyte is a material that is widely studied and used in lithium ion batteries (Li-ion) and other high-energy density batteries. Compared with traditional liquid electrolytes, the solid polymer electrolyte has many advantages, such as higher safety, greater battery energy density, wider working temperature range, etc.

[0004] The main components of the polymer solid electrolyte include a polymer matrix and an alkali metal salt. The polymer electrolyte originated from the composite of polyethylene oxide (PEO) and alkali metal salt reported by Wright et al. in 1973. Subsequently, ionically conductive polymers have attracted widespread attention. In 1979, Amand et al. first reported a lithium ion polymer electrolyte based on PEO, and successfully prepared a polymer battery. Since then, the polymer solid electrolyte has made great progress in theoretical research and practical application, and different types of polymer electrolytes have also been gradually developed.

[0005] The polymer solid electrolyte can avoid the risk of leakage and electric leakage of the liquid electrolyte, and is relatively stable to metallic lithium. At the same time, the polymer solid electrolyte has flexibility and easy processing characteristics, and can be prepared into various shapes and films according to different needs. The polymer solid electrolyte has good plasticity, can maintain full contact with the electrode, and reduces the interfacial resistance of the electrolyte / electrode. However, the polymer solid electrolyte still has many problems at present. For example: the conductivity of the polymer solid electrolyte is low, and the thermal stability and electrochemical stability are poorer than those of inorganic solid electrolytes. In addition, the dendrite growth problem cannot be completely solved in the polymer solid electrolyte.

[0006] Current research directions and improvement methods for solid-state polymer electrolytes in lithium batteries:

[0007] Improving ionic conductivity: Increasing the ionic conductivity of solid-state electrolytes is a major research direction. This can be achieved by improving the chemical composition, structure of the electrolyte, or adding conductive fillers, etc. For example, exploring new high ionic conductivity materials, optimizing the lithium salt concentration of polymer electrolytes, etc. can improve ionic conductivity.

[0008] Improving mechanical stability: Solid-state electrolytes need to have sufficient mechanical stability to cope with the charge and discharge cycles and temperature changes of the battery. Researchers are committed to improving the mechanical properties of electrolytes in material design to reduce the cracking and damage of solid-state electrolytes.

[0009] Reducing the interfacial resistance of the electrolyte: The resistance between the solid-state electrolyte and the electrode material is an important limiting factor for battery performance. Improving the interface between the electrolyte and the electrode and reducing the interfacial resistance can improve the power performance and charge and discharge efficiency of the battery.

[0010] Extending the working temperature range: Solid-state electrolytes usually perform better at lower temperatures, but their performance decreases at high temperatures. Researchers are committed to expanding the working temperature range of solid-state electrolytes to adapt to various application scenarios.

[0011] Reducing manufacturing costs: Achieving low-cost solid-state electrolyte preparation methods is an important research direction. This includes developing cheaper raw materials, simplifying the manufacturing process, and improving production efficiency.

[0012] Safety improvement: Solid-state electrolytes are of great interest due to their lower fire and explosion risk, but safety remains an important research direction. Researchers are looking for safer electrolyte materials and designing automatic power-off mechanisms to deal with abnormal situations.

[0013] Multi-level structure electrolyte: Some research teams apply multi-level structures to solid-state electrolytes to achieve better performance. These structures include nanoparticles, porous structures, and composite materials to enhance the conductivity and stability of the electrolyte.

[0014] How to further improve the conductivity and stability of solid-state electrolytes is a pressing problem. SUMMARY

[0015] In view of the defects in the prior art, a solid polymer electrolyte for lithium batteries is disclosed.

[0016] The specific technical solutions of the present application are as follows:

[0017] A preparation method of a solid polymer electrolyte for lithium batteries comprises the following steps:

[0018] Preparation of ceramic electrolyte nanoparticles, preparation of lithium ion filled porous activated carbon powder, mixing and uniformly dispersing the ceramic electrolyte nanoparticles and the lithium ion filled porous activated carbon powder in polyethylene oxide to obtain the solid polymer electrolyte for lithium battery.

[0019] Preferably, a preparation method of a solid polymer electrolyte for lithium battery comprises the following steps:

[0020] (1) Dissolve lithium nitrate, tetrabutyl titanate, zirconium oxychloride octahydrate and aluminum trichloride hexahydrate in a citric acid-ethylene glycol solution, stir to form a transparent solution, dry the solution to obtain a transparent gel, and calcine the transparent gel at high temperature to remove carbon therein to obtain ceramic electrolyte nanoparticles;

[0021] (2) After washing, drying and shearing, coconut fiber is pulverized and sieved to obtain coconut fiber powder; the obtained cellulose is treated with sodium hydroxide aqueous solution, and after filtration, washing and drying, activated cellulose powder is obtained;

[0022] (3) The activated cellulose powder obtained in step (2) is immersed in a copper chloride aqueous solution, stirred, filtered and oxidized to obtain copper oxide filled cellulose powder; the copper oxide filled cellulose powder is immersed in sulfuric acid and stirred, filtered, washed and dried to obtain porous cellulose powder;

[0023] (4) The porous cellulose powder obtained in step (3), lithium nitrate and water are mixed and stirred, filtered and dried to obtain lithium ion filled porous cellulose powder; the lithium ion filled porous cellulose powder is calcined in an oxygen-free environment to obtain lithium ion filled porous activated carbon powder;

[0024] (5) The ceramic electrolyte nanoparticles obtained in step (1) and the lithium ion filled porous activated carbon powder obtained in step (4) are mixed to obtain a mixed electrolyte; polyethylene oxide is dissolved in anhydrous acetonitrile, and then the mixed electrolyte is added, stirred and ultrasonicated repeatedly to ensure that the mixed electrolyte is fully dispersed, the obtained uniform suspension is coated on a polytetrafluoroethylene substrate, and is fully dried under vacuum conditions to obtain a solid polymer electrolyte for lithium battery.

[0025] Preferably, a preparation method of a solid polymer electrolyte for lithium battery comprises the following steps:

[0026] (1) 4-5 parts of lithium nitrate, 1-1.5 parts of tetrabutyl titanate, 1.5-2 parts of zirconium oxychloride octahydrate and 3-4 parts of aluminum chloride trihydrate are dissolved in 10-20 parts of a citric acid-ethylene glycol solution to form a transparent solution by stirring, and the solution is dried to obtain a transparent gel; the transparent gel is calcined at 600-700°C for 1-2 h to remove carbon therein, to obtain ceramic electrolyte nanoparticles;

[0027] (2) Coconut shell fibers are cleaned, dried, cut, ground, and sieved through a 180-200 mesh screen to obtain coconut shell fiber powder; the obtained cellulose is treated with 6-8 wt% sodium hydroxide aqueous solution for 1-2 h, filtered, washed, and dried to obtain activated cellulose powder;

[0028] (3) The activated cellulose powder obtained in step (2) is immersed in a 18-20 wt% copper chloride aqueous solution at a bath ratio of 1 g:(10-20) mL, stirred for 1-2 h, filtered, and oxidized at 100-120°C for 6-8 h to obtain copper oxide-filled cellulose powder; the copper oxide-filled cellulose powder is immersed in 10-16 wt% sulfuric acid at a bath ratio of 1 g:(10-20) mL, stirred for 15-30 min, filtered, washed, and dried to obtain porous cellulose powder;

[0029] (4) 5-10 parts of the porous cellulose powder obtained in step (3), 1.6-2 parts of lithium nitrate, and 40-50 parts of water are mixed and stirred for 1-2 h, filtered, and dried to obtain lithium ion-filled porous cellulose powder; the lithium ion-filled porous cellulose powder is calcined in an oxygen-free environment at 600-800°C to obtain lithium ion-filled porous activated carbon powder;

[0030] (5) The ceramic electrolyte nanoparticles obtained in step (1) and the lithium ion-filled porous activated carbon powder obtained in step (4) are mixed at a mass ratio of 1:(0.1-0.2) to obtain a mixed electrolyte; 8-12 parts of polyethylene oxide are dissolved in 90-100 parts of anhydrous acetonitrile, followed by addition of 1-1.5 parts of the mixed electrolyte, stirring and ultrasonicating for 40-60 min, and coating the obtained uniform suspension on a polytetrafluoroethylene substrate and drying at 50-70°C under vacuum to obtain a solid polymer electrolyte for lithium batteries.

[0031] The ultrasonic power in step (5) is 600-1000 W, and the frequency is 40-80 kHz.

[0032] The solid polymer electrolyte prepared by the method has the lithium ion filled porous activated carbon powder added, which can greatly improve the lithium ion transmission efficiency of the solid polymer electrolyte, thereby improving the ionic conductivity.

[0033] Advantages of the present application:

[0034] The common coconut fiber is used as the carrier in the present application, and the price is low and the cost is low, then the adsorption capacity of the coconut fiber to lithium ions is enhanced in a porous manner, and finally the lithium ion filled porous activated carbon powder is obtained by carbonization; the solid polymer electrolyte prepared by the present application has the lithium ion filled porous activated carbon powder added, which can greatly improve the lithium ion transmission efficiency of the solid polymer electrolyte, thereby improving the ionic conductivity. DETAILED DESCRIPTION

[0035] In the present application, all the equipment and raw materials can be purchased from the market or commonly used in the industry, and the methods in the following examples are conventional methods in the field unless otherwise specified.

[0036] Example 1

[0037] A preparation method of a solid polymer electrolyte for a lithium battery, comprising the following steps:

[0038] (1) 4.13 parts of lithium nitrate, 1.20 parts of tetrabutyl titanate, 1.61 parts of zirconium oxychloride octahydrate and 3.40 parts of aluminum chloride hexahydrate are dissolved in 16 parts of a citric acid-ethylene glycol solution according to the mass fraction, and stirred to form a transparent solution, and the solution is dried to obtain a transparent gel; the transparent gel is calcined at 600 DEG C for 2h to remove carbon therein, and ceramic electrolyte nanoparticles are obtained;

[0039] (2) The coconut fiber is cleaned, dried, cut and treated, then crushed and sieved through a 200 mesh screen to obtain coconut fiber powder; the obtained cellulose is treated with 7wt% sodium hydroxide aqueous solution for 1h, and after filtration, washing and drying, activated cellulose powder is obtained;

[0040] (3) The activated cellulose powder prepared in step (2) was immersed in a 20 wt% aqueous copper chloride solution at a bath ratio of 1 g:20 mL, stirred for 1 h, filtered, and oxidized at 100°C for 8 h to obtain copper oxide-filled cellulose powder; the copper oxide-filled cellulose powder was immersed in 12 wt% sulfuric acid at a bath ratio of 1 g:20 mL, stirred for 20 min, and filtered, washed, and dried to obtain porous cellulose powder;

[0041] (4) 8 parts of the porous cellulose powder prepared in step (3), 1.8 parts of lithium nitrate, and 50 parts of water were mixed and stirred for 2 h, filtered, and dried to obtain lithium ion-filled porous cellulose powder; the lithium ion-filled porous cellulose powder was calcined at 700°C in an oxygen-free environment to obtain lithium ion-filled porous activated carbon powder;

[0042] (5) The ceramic electrolyte nanoparticles obtained in step (1) and the lithium ion-filled porous activated carbon powder obtained in step (4) were mixed at a mass ratio of 1:0.16 to obtain a mixed electrolyte; 10 parts of polyethylene oxide were dissolved in 90 parts of anhydrous acetonitrile, followed by the addition of 1.2 parts of the mixed electrolyte, stirring and ultrasonicating for 50 min, and coating the obtained uniform suspension on a polytetrafluoroethylene substrate and drying at 60°C under vacuum to obtain a solid polymer electrolyte for lithium batteries.

[0043] The ultrasonic power in step (5) was 800 W, and the frequency was 60 kHz.

[0044] Example 2

[0045] A preparation method of a solid polymer electrolyte for lithium batteries, comprising the following steps:

[0046] (1) 4.13 parts of lithium nitrate, 1.20 parts of tetrabutyl titanate, 1.61 parts of zirconium oxychloride octahydrate, and 3.40 parts of aluminum chloride trihydrate were dissolved in 16 parts of a citric acid-ethylene glycol solution, and stirred to form a transparent solution; the transparent solution was dried to obtain a transparent gel; the transparent gel was calcined at 600°C for 2 h to remove carbon therein, to obtain ceramic electrolyte nanoparticles;

[0047] (2) Coconut shell fibers were cleaned, dried, cut, and ground to pass through a 200-mesh sieve to obtain coconut shell fiber powder; the obtained cellulose was treated with 7 wt% sodium hydroxide aqueous solution for 1 h, filtered, washed, and dried to obtain activated cellulose powder;

[0048] (3) 8 parts of the activated cellulose powder prepared in step (2), 1.8 parts of lithium nitrate, 50 parts of water were mixed and stirred for 2 h, and then filtered and dried to obtain lithium ion loaded cellulose powder; the lithium ion loaded cellulose powder was calcined in an oxygen-free environment at 700℃ to obtain lithium ion loaded activated carbon powder;

[0049] (5) The ceramic electrolyte nanoparticles obtained in step (1) and the lithium ion loaded activated carbon powder obtained in step (4) were mixed in a mass ratio of 1:0.16 to obtain a mixed electrolyte; 10 parts of polyethylene oxide were dissolved in 90 parts of anhydrous acetonitrile, then 1.2 parts of the mixed electrolyte was added, stirred and ultrasonicated for 50 min, and the obtained uniform suspension was coated on a polytetrafluoroethylene substrate and dried under vacuum at 60℃ to obtain a solid polymer electrolyte for lithium batteries.

[0050] The ultrasonic power in step (5) was 800 W and the frequency was 60 kHz.

[0051] Example 3

[0052] A preparation method of a solid polymer electrolyte for lithium batteries, comprising the following steps:

[0053] (1) 4.13 parts of lithium nitrate, 1.20 parts of tetrabutyl titanate, 1.61 parts of zirconium oxychloride octahydrate and 3.40 parts of aluminum chloride trihydrate were dissolved in 16 parts of a citric acid-ethylene glycol solution to form a transparent solution, and the solution was dried to obtain a transparent gel; the transparent gel was calcined at 600℃ for 2 h to remove carbon therein to obtain ceramic electrolyte nanoparticles;

[0054] (2) Coconut shell fibers were cleaned, dried, cut and then ground to obtain coconut shell fiber powder with a mesh size of 200; the obtained cellulose was treated with 7wt% sodium hydroxide aqueous solution for 1 h, and then filtered, washed and dried to obtain activated cellulose powder;

[0055] (3) The activated cellulose powder prepared in step (2) was immersed in a 20wt% copper chloride aqueous solution at a bath ratio of 1g:20mL, stirred for 1 h, filtered, and then oxidized at 100℃ for 8 h to obtain copper oxide filled cellulose powder; the copper oxide filled cellulose powder was immersed in 12wt% sulfuric acid at a bath ratio of 1g:20mL, stirred for 20 min, and then filtered, washed and dried to obtain porous cellulose powder;

[0056] (4) 8 parts of the porous cellulose powder prepared in step (3), 1.8 parts of lithium nitrate, 50 parts of water were mixed and stirred for 2 h, and then filtered and dried to obtain lithium ion filled porous cellulose powder;

[0057] (5) The ceramic electrolyte nanoparticles obtained in step (1) and the lithium ion filled porous cellulose powder obtained in step (4) are mixed in a mass ratio of 1:0.16 to obtain a mixed electrolyte; 10 parts of polyethylene oxide are dissolved in 90 parts of anhydrous acetonitrile, then 1.2 parts of the mixed electrolyte are added, stirred and ultrasonically treated for 50 min, the obtained uniform suspension is coated on a polytetrafluoroethylene substrate, and dried at 60°C under vacuum to obtain a solid polymer electrolyte for lithium batteries.

[0058] The ultrasonic power in step (5) is 800 W, and the frequency is 60 kHz.

[0059] Comparative Example 1

[0060] A preparation method of a solid polymer electrolyte for lithium batteries, comprising the following steps:

[0061] (1) 4.13 parts of lithium nitrate, 1.20 parts of tetrabutyl titanate, 1.61 parts of zirconium oxychloride octahydrate and 3.40 parts of aluminum chloride trihydrate are dissolved in 16 parts of a citric acid-ethylene glycol solution, stirred to form a transparent solution, and the solution is dried to obtain a transparent gel; the transparent gel is calcined at 600°C for 2h to remove carbon therein to obtain ceramic electrolyte nanoparticles;

[0062] (2) Coconut shell fibers are washed, dried, cut and then pulverized to obtain coconut shell fiber powder by passing through a 200-mesh sieve; the coconut shell fiber powder is calcined at 700°C in an oxygen-free environment to obtain carbon powder;

[0063] (3) The ceramic electrolyte nanoparticles obtained in step (1) and the carbon powder obtained in step (2) are mixed in a mass ratio of 1:0.16 to obtain a mixed electrolyte; 10 parts of polyethylene oxide are dissolved in 90 parts of anhydrous acetonitrile, then 1.2 parts of the mixed electrolyte are added, stirred and ultrasonically treated for 50 min, the obtained uniform suspension is coated on a polytetrafluoroethylene substrate, and dried at 60°C under vacuum to obtain a solid polymer electrolyte for lithium batteries.

[0064] The ultrasonic power in step (3) is 800 W, and the frequency is 60 kHz.

[0065] Comparative Example 2

[0066] A preparation method of a solid polymer electrolyte for lithium batteries, comprising the following steps:

[0067] (1) 4.13 parts of lithium nitrate, 1.20 parts of tetrabutyl titanate, 1.61 parts of zirconium oxychloride octahydrate and 3.40 parts of aluminum chloride trihydrate were dissolved in 16 parts of a citric acid-ethylene glycol solution, stirred to form a transparent solution, and the solution was dried to obtain a transparent gel; the transparent gel was calcined at 600°C for 2h to remove carbon therein, to obtain ceramic electrolyte nanoparticles;

[0068] (2) The coconut shell fiber was cleaned, dried, sheared, crushed, and sieved through a 200-mesh screen to obtain coconut shell fiber powder; the obtained cellulose was treated with 7wt% sodium hydroxide aqueous solution for 1h, and after filtration, washing and drying, activated cellulose powder was obtained;

[0069] (3) The activated cellulose powder obtained in step (2) was calcined in an oxygen-free environment at 700°C to obtain carbon powder;

[0070] (4) The ceramic electrolyte nanoparticles obtained in step (1) and the carbon powder obtained in step (3) were mixed in a mass ratio of 1:0.16 to obtain a mixed electrolyte; 10 parts of polyethylene oxide were dissolved in 90 parts of anhydrous acetonitrile, then 1.2 parts of the mixed electrolyte were added, stirred and ultrasonicated for 50min, the obtained uniform suspension was coated on a polytetrafluoroethylene substrate, and dried under vacuum at 60°C to obtain a solid polymer electrolyte for lithium batteries.

[0071] The ultrasonic power in step (4) was 800W and the frequency was 60kHz.

[0072] Comparative Example 3

[0073] A preparation method of a solid polymer electrolyte for lithium batteries, comprising the following steps:

[0074] (1) 4.13 parts of lithium nitrate, 1.20 parts of tetrabutyl titanate, 1.61 parts of zirconium oxychloride octahydrate and 3.40 parts of aluminum chloride trihydrate were dissolved in 16 parts of a citric acid-ethylene glycol solution, stirred to form a transparent solution, and the solution was dried to obtain a transparent gel; the transparent gel was calcined at 600°C for 2h to remove carbon therein, to obtain ceramic electrolyte nanoparticles;

[0075] (2) The coconut shell fiber was cleaned, dried, sheared, crushed, and sieved through a 200-mesh screen to obtain coconut shell fiber powder; the obtained cellulose was treated with 7wt% sodium hydroxide aqueous solution for 1h, and after filtration, washing and drying, activated cellulose powder was obtained;

[0076] (3) The activated cellulose powder prepared in step (2) was immersed in a 20 wt% aqueous copper chloride solution at a bath ratio of 1 g:20 mL, stirred for 1 h, filtered, and oxidized at 100°C for 8 h to obtain copper oxide-filled cellulose powder; the above copper oxide-filled cellulose powder was immersed in 12 wt% sulfuric acid at a bath ratio of 1 g:20 mL, stirred for 20 min, and filtered, washed, and dried to obtain porous cellulose powder;

[0077] (4) The above porous cellulose powder was calcined in an oxygen-free environment at 700°C to obtain porous activated carbon powder;

[0078] (5) The ceramic electrolyte nanoparticles obtained in step (1) and the porous activated carbon powder obtained in step (4) were mixed at a mass ratio of 1:0.16 to obtain a mixed electrolyte; 10 parts of polyethylene oxide were dissolved in 90 parts of anhydrous acetonitrile, followed by the addition of 1.2 parts of the mixed electrolyte, stirring and ultrasonicating for 50 min, and the obtained uniform suspension was coated on a polytetrafluoroethylene substrate and dried under vacuum at 60°C to obtain a solid polymer electrolyte for lithium batteries.

[0079] The ultrasonic power in step (5) was 800 W and the frequency was 60 kHz.

[0080] Comparative Example 4

[0081] A method for preparing a solid polymer electrolyte for lithium batteries, comprising the following steps:

[0082] (1) 4.13 parts of lithium nitrate, 1.20 parts of tetrabutyl titanate, 1.61 parts of zirconium oxychloride octahydrate, and 3.40 parts of aluminum chloride trihydrate were dissolved in 16 parts of a citric acid-ethylene glycol solution, and stirred to form a transparent solution; the transparent solution was dried to obtain a transparent gel; the transparent gel was calcined at 600°C for 2 h to remove carbon therein, to obtain ceramic electrolyte nanoparticles;

[0083] (2) 10 parts of polyethylene oxide were dissolved in 90 parts of anhydrous acetonitrile, followed by the addition of 1.2 parts of the ceramic electrolyte nanoparticles obtained in step (1), stirring and ultrasonicating for 50 min, and the obtained uniform suspension was coated on a polytetrafluoroethylene substrate and dried under vacuum at 60°C to obtain a solid polymer electrolyte for lithium batteries.

[0084] The ultrasonic power in step (2) was 800 W and the frequency was 60 kHz.

[0085] Test Example 1

[0086] A solid polymer electrolyte was placed between stainless steel electrodes, and then the ionic conductivity (δ) was measured using a VMP3 measuring device and a 4294 via AC impedance measurement in the 100MHz to 0.1Hz frequency band. The ionic conductivity (δ) was calculated as l / (R×A), where δ is the ionic conductivity (mS / cm), l is the electrolyte thickness (cm), R is the measured resistance (mS), and A is the electrolyte area (cm²). 2 ))

[0087] Table 1: Results of Ion Conductivity Test

[0088]

[0089]

[0090] As shown in Table 1, the solid polymer electrolyte for lithium batteries prepared in Example 1 of this invention has the highest conductivity. Compared with Comparative Example 4, its ionic conductivity has been significantly improved. This invention believes that this is because lithium-ion-filled porous activated carbon powder was added to the solid polymer electrolyte prepared in Example 1, which can greatly improve the lithium-ion transport efficiency of the solid polymer electrolyte, thereby increasing the ionic conductivity. This invention first uses common coconut shell fiber as a carrier, which is inexpensive and low-cost. Then, it is activated with sodium hydroxide to enable it to adsorb more metal ions. Next, copper ions are adsorbed and oxidized to cause the cellulose structure to expand, generating more active sites. Finally, copper ions are removed, and lithium ions are adsorbed to obtain lithium-ion-filled porous fibers. However, because cellulose has weak conductivity and strong water absorption, it not only affects the lithium-ion transport efficiency but also poses certain dangers to the battery. The fact that the conductivity of lithium-ion-filled porous cellulose powder directly added in Example 3 is much lower than that in Example 1 also proves this point. To further improve the ionic conductivity of the prepared solid electrolyte, the present invention performs high-temperature carbonization treatment on the prepared lithium-ion-filled porous cellulose powder to obtain porous activated carbon powder containing a large number of lithium ions, which can effectively form stable lithium-ion transport channels in the solid polymer electrolyte, greatly improving the electron transport efficiency of the prepared solid electrolyte.

[0091] A comparison of Examples 1 and 2 also reveals that in Example 2, without the coconut shell fiber undergoing porousification treatment, the lithium-ion-loaded activated carbon powder, when applied to the solid polymer electrolyte, exhibits a lower ionic conductivity than in Example 1. This indicates that porousification treatment is beneficial for improving the performance of lithium-ion-filled porous activated carbon powder. This invention suggests that porousification treatment firstly increases the adsorption rate of lithium ions by the coconut shell fiber, and secondly, the carbonization of the porous fiber helps improve charge transport capacity, thereby enhancing the lithium-ion transport performance of the solid polymer electrolyte.

[0092] It can be found from Comparative Example 1, Comparative Example 2, Comparative Example 3 and Comparative Example 4 that without loading lithium ions, directly carbonizing coconut shell fibers has little effect on the improvement of the ion conductivity of the solid polymer electrolyte, which indicates that lithium ions play a major role in the conduction.

[0093] Test Example 2

[0094] Assembly of the solid-state battery: the electrolyte wafer (20 μm in diameter) after cutting was pasted with a positive electrode wafer on one side and a lithium wafer (360 μm in thickness) of the same area on the other side, and the solid-state lithium metal battery was obtained after encapsulation. Among them, the positive electrode current collector was a carbon-coated aluminum foil, and the negative electrode current collector was a copper foil.

[0095] Under a current density of 1 mA / cm 2 , the battery was first charged to the cut-off voltage (1 V), and then discharged for 1 h until the end of the cycle, and the cycle number was 200 times.

[0096] Table 2: Cycle performance test results

[0097] Capacitance decrease rate % Example 1 0.67 Example 2 1.03 Example 3 7.36

[0098] As can be seen from Table 2, the stability of the solid electrolyte of Example 3 directly using lithium ion filled porous cellulose powder is obviously lower than that of Example 1 and Example 2, which is believed by the present application to be due to the strong water absorption of cellulose, which is not conducive to the stability of the solid polymer electrolyte.

Claims

1. A method for producing a solid polymer electrolyte for a lithium battery, characterized by, The method comprises the following steps: mixing and uniformly dispersing ceramic electrolyte nanoparticles and lithium ion filled porous activated carbon powder in polyethylene oxide to obtain the solid polymer electrolyte for lithium battery. The method for preparing the lithium ion filled porous activated carbon powder comprises the following steps: (1) coconut shell fibers are cleaned, dried, sheared, crushed, and sieved to obtain coconut shell fiber powder; the obtained cellulose is treated with a sodium hydroxide aqueous solution, filtered, washed, and dried to obtain activated cellulose powder; (2) the activated cellulose powder prepared in step (1) is immersed in a copper chloride aqueous solution, stirred, filtered, and oxidized to obtain copper oxide filled cellulose powder; the copper oxide filled cellulose powder is immersed in sulfuric acid and stirred, filtered, washed, and dried to obtain porous cellulose powder; (3) the porous cellulose powder prepared in step (2), lithium nitrate, and water are mixed and stirred, filtered, and dried to obtain lithium ion filled porous cellulose powder; the lithium ion filled porous cellulose powder is calcined in an oxygen-free environment to obtain lithium ion filled porous activated carbon powder.

2. The method for preparing a solid polymer electrolyte for lithium batteries as described in claim 1, characterized in that, The method for preparing ceramic electrolyte nanoparticles comprises the following steps: lithium nitrate, tetrabutyl titanate, zirconium oxychloride octahydrate, and aluminum trichloride hexahydrate are dissolved in a citric acid-ethylene glycol solution to form a transparent solution, the solution is dried to obtain a transparent gel, and the transparent gel is calcined at high temperature to remove carbon therein to obtain ceramic electrolyte nanoparticles.

3. The method for preparing a solid polymer electrolyte for lithium batteries as described in claim 2, characterized in that, The method for preparing ceramic electrolyte nanoparticles, The method for preparing ceramic electrolyte nanoparticles, 4. The method for preparing a solid polymer electrolyte for lithium batteries as described in claim 1, characterized in that, The method for preparing lithium ion filled porous activated carbon powder comprises the following steps: (1) coconut shell fibers are cleaned, dried, sheared, crushed, and sieved through a 180-200 mesh sieve to obtain coconut shell fiber powder; the obtained cellulose is treated with a 6-8wt% sodium hydroxide aqueous solution for 1-2h, filtered, washed, and dried to obtain activated cellulose powder; (2) the activated cellulose powder prepared in step (1) is immersed in a copper chloride aqueous solution with a concentration of 18-20wt% at a bath ratio of 1g:(10-20)mL, stirred for 1-2h, filtered, and oxidized at 100-120℃ for 6-8h to obtain copper oxide filled cellulose powder; the copper oxide filled cellulose powder is immersed in sulfuric acid with a concentration of 10-16wt% at a bath ratio of 1g:(10-20)mL, stirred for 15-30min, filtered, washed, and dried to obtain porous cellulose powder; (3) mixing 5-10 parts of the porous cellulose powder prepared in step (2), 1.6-2 parts of lithium nitrate and 40-50 parts of water by mass fraction, stirring for 1-2 hours, filtering and drying to obtain lithium ion filled porous cellulose powder; calcining the lithium ion filled porous cellulose powder in an oxygen-free environment at 600-800℃ to obtain lithium ion filled porous activated carbon powder.

5. The method for preparing a solid polymer electrolyte for lithium batteries as described in claim 1, characterized in that, comprising the following steps: mixing the ceramic electrolyte nanoparticles and the lithium ion filled porous activated carbon powder to obtain a mixed electrolyte; dissolving polyethylene oxide in anhydrous acetonitrile, then adding the mixed electrolyte, stirring and ultrasonicating repeatedly to ensure that the mixed electrolyte is fully dispersed, coating the obtained uniform suspension on a polytetrafluoroethylene substrate and drying under vacuum conditions to obtain a solid polymer electrolyte for lithium batteries.

6. The method for preparing a solid polymer electrolyte for lithium batteries as described in claim 5, characterized in that, comprising the following steps: mixing the ceramic electrolyte nanoparticles and the lithium ion filled porous activated carbon powder at a mass ratio of 1:(0.1-0.2) to obtain a mixed electrolyte; dissolving 8-12 parts of polyethylene oxide in 90-100 parts of anhydrous acetonitrile by mass fraction, then adding 1-1.5 parts of the mixed electrolyte, stirring and ultrasonicating for 40-60 minutes, coating the obtained uniform suspension on a polytetrafluoroethylene substrate and drying at 50-70℃ under vacuum conditions to obtain a solid polymer electrolyte for lithium batteries.

7. The method for preparing a solid polymer electrolyte for lithium batteries as described in claim 6, characterized in that, The ultrasonic power is 600-1000W and the frequency is 40-80kHz.

8. A solid polymer electrolyte for a lithium battery, characterized by, prepared by the preparation method of the solid polymer electrolyte for lithium batteries according to any one of claims 1-7.

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