1187 results about "Lithium dendrite" patented technology

The invention discloses a lithium ion battery internal short circuit fault detection method based on time-frequency fusion, and the method comprises the steps: firstly constructing a fractional order equivalent circuit model fused with an electrochemical aging mechanism, and simulating the paths of conductivity reduction, active material loss and lithium inventory reduction in combination with an aging empirical formula; joint modeling of the aging process and the random internal short circuit is achieved, and multi-cycle voltage and current and electrochemical impedance spectroscopy data are obtained; secondly, extracting time domain features by using a time domain attention enhanced long-short-term memory network, and analyzing frequency domain information by using a multi-scale frequency sensing convolutional neural network; and then weighting and screening two types of modal features through a dynamic gating fusion module, introducing a cross attention mechanism to establish dependency mapping between time-frequency domain features, and finally outputting an internal short circuit fault detection result. The method can solve the problems that in the lithium ion battery aging process, due to lithium dendrite growth, the internal short circuit early fault is high in concealment, and single time-frequency characteristics are difficult to detect, and early high-precision recognition of the internal short circuit fault can be achieved.

The invention provides a diaphragm and a preparation method thereof and a lithium ion battery, the diaphragm comprises a porous support layer and a gradient functional layer, the porous support layer comprises a base membrane with the porosity of 45-60% and active groups modified on the surface of the base membrane, and the gradient functional layer comprises a heat conduction strengthening layer and an ion channel layer, the heat conduction strengthening layer comprises a first polymer and a modified boron nitride nanosheet, and the ion channel layer comprises a second polymer and a solid electrolyte nanowire. The porous supporting layer and the gradient functional layer are overlapped to form the composite diaphragm, so that high thermal stability, high wettability and high ion conductivity are synergistically realized, and formation of lithium dendrites can be inhibited.

The invention relates to a lithium ion battery thermal runaway early warning method and device and a medium, and the method comprises the steps: setting an AC excitation power supply parameter, and outputting a sine excitation current with a preset frequency and amplitude; injecting the polymer into a single battery through a four-probe method; synchronously acquiring an injection current signal and a response voltage signal; through fast Fourier transform analysis, the amplitude and the phase of a signal fundamental frequency component are extracted; and calculating the electrochemical impedance under the frequency. And in combination with an electrochemical impedance-thermal runaway precursor mapping database established by a pre-experiment, converting the impedance value into a corresponding thermal runaway risk level, and outputting corresponding early warning information. According to the method, lithium dendrite growth and internal micro short circuit signs can be captured in advance, and the early warning time efficiency is remarkably improved compared with traditional voltage / temperature monitoring.

The invention discloses a high-interface-stability composite solid electrolyte membrane as well as a preparation method and application thereof. The composite solid electrolyte membrane comprises a gradient aperture three-dimensional porous skeleton formed by sintering inorganic solid electrolyte particles, a polymer electrolyte filled in a pore channel, and a plastic interface stable layer positioned between the electrolyte membrane and an electrode. The preparation method comprises the following steps: preparing a gradient aperture porous framework through a pore-forming agent template method and a tape casting technology, dipping and filling a polymer electrolyte precursor solution in a solution, accelerating in-situ polymerization by adopting electric induction, and performing hot-pressing treatment. The composite solid-state electrolyte membrane has high ionic conductivity, excellent interface compatibility and high mechanical strength, can effectively inhibit the growth of lithium dendrites, can be applied to solid-state batteries such as lithium metal batteries, lithium sulfur batteries and lithium air batteries, and can remarkably prolong the cycle life and improve the safety performance of the batteries, and the preparation process is suitable for large-scale production.

The invention discloses an artificial SEI material and a preparation method thereof, an artificial SEI film and an artificial SEI film modified negative electrode. The artificial SEI material is an organic polymer brush (CNF-g-PSSX) prepared by grafting cellulose nanofibers with polystyrene sulfonate. The polymer brush is of a crystal structure and has a firm framework; and the side chain of polystyrene sulfonate has rich-SO3 functional groups which are matched with cations in sulfonate, so that a rapid ion transmission channel is provided, high-current-density circulation can be realized, and good interface contact is ensured. Due to a special molecular topological structure and a multi-component synergistic effect, when the organic polymer brush forms an artificial SEI film, high mechanical strength, high ionic conductivity and low interface impedance can be obtained at the same time, and through strong electrostatic repulsion between a negatively charged-SO3 group and the surface of a negatively charged lithium dendrite tip, the electrochemical performance of the artificial SEI film is improved. An obvious inhibition effect is shown on the continuous growth of dendritic crystals.

The invention discloses a method for preparing a lithium-copper composite negative electrode by utilizing lithium slag and application, and the preparation method of the negative electrode comprises the following steps: adding the lithium slag with certain concentration after removing impurities such as Ca < 2 + >, Mg < 2 + > and Fe < 3 + > through acid treatment into metal lithium in a molten state, and fully stirring until the reaction is complete; and coating the molten metal lithium obtained after the reaction on a current collector to obtain the modified lithium metal negative electrode plate. The prepared lithium-copper composite negative electrode has a lithium-loving 3D frame structure, volume expansion in the circulation process can be inhibited, lithium oxide, lithium aluminum alloy and lithium silicon alloy existing on the 3D frame structure can serve as lithium-loving sites for uniform lithium ion deposition, lithium dendrite growth is inhibited, and long-term stable circulation of the lithium metal negative electrode is promoted.

The invention provides a fast-charging type solid-state lithium battery alloy negative electrode material, a preparation method and a solid-state lithium battery, and relates to the technical field of lithium batteries. The alloy negative electrode material comprises the following element components in percentage by mass: 30-38% of indium In, 30-35% of tin Sn, 28-35% of bismuth Bi and 0-1.5% of doping elements, crystal phases formed by the alloy negative electrode material of the fast-charging type solid-state lithium battery at least comprise two crystal phases, namely InSn4 and InBi. The alloy negative electrode material has relatively high surface capacity, lithium ion conductivity and lithium ion diffusion coefficient, lithium dendrites do not grow on a negative electrode when a solid-state lithium battery assembled by the alloy negative electrode material is charged and discharged under high current density, and the battery is high in energy density and long in cycle life.

The invention relates to a composite diaphragm with high ionic conductivity, a composite solid electrolyte and a preparation method thereof. The composite diaphragm is composed of a lithium lanthanum-based fluorine-doped solid electrolyte LLMOF and a base membrane, the chemical general formula of the LLMOF is Li < x > La < y > M < 1 > < z > M < 2 > < w > M < 3 > O < 6 > F, wherein M1 is a tetravalent cation, M2 is a pentavalent cation, and M3 is a hexavalent cation; 1 < x + 3y < 5, 0 < x < = 2, and 1 / 3 < y < 5 / 3; 0 < = z < = 2, 0 < = w < = 2, 0 < = u < = 2, z + w + u = 2; the base membrane is a large-aperture base membrane, and the aperture r is more than or equal to 200nm and less than or equal to 1mu m; the particle size D50 of the LLMOF is 50 nm to 1 [mu] m, and the particle size D50 of the LLMOF is less than or equal to the aperture r of the base film. According to the composite diaphragm disclosed by the invention, the LLMOF solid electrolyte with an ion channel function is introduced, so that efficient conduction of ions is realized; the particle size is matched with that of a large-aperture base membrane, the membrane can be uniformly embedded into membrane holes, a continuous conduction path is constructed, and the ionic conductivity is improved; meanwhile, the composite diaphragm has excellent thermal stability and interface wettability, interface impedance is effectively reduced, and growth of lithium dendrites is inhibited.

The invention belongs to the technical field of batteries, and particularly relates to a negative electrode material, a secondary battery and electric equipment. The second coating layer with the porous carbon material in the negative electrode material provides a sufficient buffer space for volume expansion of silicon, so that cracks and pulverization of the negative electrode material are effectively reduced, and the structural integrity of the negative electrode material is further ensured. And meanwhile, the solid electrolyte arranged in the second coating layer can maintain the smoothness of an ion transmission path in the silicon expansion process, so that the rate capability and the quick charge performance of the battery are ensured. Besides, a third coating layer (SEI film) formed by the ionic liquid has good ionic conductivity, and dynamic covalent bonds existing in some ionic liquids can be fractured and recombined under the action of external stress, so that a self-repairing function is realized. Therefore, when cracks are generated on the surface of the negative electrode material due to volume expansion, the third coating layer can quickly repair the cracks, prevent electrolyte permeation and lithium dendrite growth and inhibit side reactions.

The invention relates to the technical field of new energy automobile and battery safety, and discloses a power battery thermal runaway risk early warning method, which comprises the following steps: synchronously acquiring battery internal resistance dynamic change, characteristic gas concentration and temperature gradient distribution through a multi-physics field coupling sensor network, and constructing an electrochemical-thermal-gas ternary early criterion; the internal resistance mutation rate is calculated through self-adaptive sliding window differential, the gas precipitation rate and the temperature space heterogeneity index are combined and input into a multi-branch fusion neural network containing a gating attention mechanism, the continuous thermal runaway risk probability is output, and corresponding early warning is triggered according to grading threshold values. The system comprises an internal resistance, gas and temperature monitoring module and a multi-modal fusion evaluation and grading early warning execution module. According to the method, the traditional early warning logic singly depending on a temperature threshold value is abandoned, a ternary early criterion system with the internal resistance abrupt change rate, the characteristic gas precipitation rate and the temperature space heterogeneity index as the core is constructed for the first time, and electrochemical and physical field anomalies caused by thermal runaway precursor events such as lithium dendrite piercing of a diaphragm and SEI membrane rupture can be effectively captured.

The invention discloses a negative pole piece, a secondary battery and a power utilization device, and belongs to the technical field of batteries, the negative pole piece comprises a negative current collector, and a metal layer and an insulating layer which are sequentially arranged on at least one surface of the negative current collector, and the insulating layer and the metal layer are provided with a plurality of pore structures. The lithium-containing metal layer and the insulating layer are provided with the pore structures, so that the quality and the thickness of the negative electrode plate can be effectively reduced, the energy density of the secondary battery can be effectively improved, pre-lithiation is not needed, a porous conductive substrate is not needed to be introduced, and the lithium-containing metal layer and the insulating layer can be effectively protected. According to the present invention, the negative electrode plate has characteristics of high lithium affinity and high utilization rate of the pore structure, can effectively reduce the volume expansion of the negative electrode plate, provides the sufficient space for the deposition of the lithium, ensures the deposition of the lithium in the pore structure, effectively avoids the occurrence of the internal lithium precipitation and the surface lithium precipitation, reduces the lithium dendrites, and effectively improves the cycle stability of the secondary battery.

The invention discloses a composite solid electrolyte and a preparation method and application thereof, and belongs to the technical field of solid lithium batteries. The composite solid electrolyte comprises a polymer matrix, a lithium salt and a lithium ion modified ionic metal organic framework (MOF) material. The metal center of the ion-conducting MOF material can be selected from Zr, Ti, Hf and the like, and the organic ligand can be selected from organic acids containing sulfydryl, sulfo groups and the like. The MOF material can effectively inhibit crystallization of a polymer matrix and increase the proportion of an amorphous region, Lewis acid sites on the surface of the MOF material can promote dissociation of lithium salt, and a lithium ion coordination channel formed in the MOF material can provide an extra rapid transmission path for lithium ions. When the electrolyte is applied to the solid-state lithium battery, the growth of lithium dendrites can be effectively inhibited, and the rate capability, the cycling stability and the safety of the battery can be remarkably improved.

The invention discloses a tantalum-doped lithium metal composite negative electrode and a preparation method thereof. The preparation method comprises the following steps: melting solid-state lithium metal into liquid-state lithium metal; the tantalum metal is added into the liquid lithium metal to be mixed and stirred, the tantalum-doped lithium metal composite material is obtained after standing and cooling, and the adding amount of the tantalum metal is 0.1-10 wt% of the mass of the liquid lithium metal; and rolling the tantalum-doped lithium metal composite material to obtain the tantalum-doped lithium metal composite negative electrode, so that the tantalum is introduced into the lithium metal through a melt doping process, and the formed tantalum-doped lithium metal composite negative electrode can inhibit the growth of lithium dendrites and prolong the cycle life of the battery.

The invention discloses a preparation method and application of a composite PVDF-HFP and polylysine nanofiber diaphragm, and belongs to the technical field of lithium batteries. The composite material is prepared by blending polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP) and polylysine and then carrying out an electrostatic spinning process. The PVDF-HFP is utilized to provide excellent mechanical strength and chemical stability, rich polar amino functional groups in a polylysine molecular chain are utilized to improve the lyophilic property of the membrane, and anions in an electrolyte are fixed through an intermolecular acting force, so that the transference number of lithium ions is increased, and the lithium ions are induced to be uniformly deposited. The nanofiber membrane combines the characteristics of PVDF-HFP and polylysine, has high porosity, good thermal stability and excellent interface compatibility, can effectively inhibit the growth of lithium dendrites and prevent the diaphragm from being punctured, and can significantly prolong the cycle life and improve the safety performance of the lithium metal battery when being applied to the lithium metal battery.

The invention belongs to the technical field of all-solid-state sulfide lithium metal batteries, and relates to a lithium battery electrode containing an interface self-repairing coating as well as a preparation method and application of the lithium battery electrode. The electrode comprises a lithium metal negative electrode substrate and the interface self-repairing coating coated on the surface of the lithium metal negative electrode substrate, the interface self-repairing coating is internally provided with a dynamic reversible network, and the dynamic reversible network is constructed by disulfide bonds and hydrogen bonds. A layer of interface self-repairing coating is formed on the surface of a lithium metal negative electrode substrate to serve as a physical isolation barrier, metal lithium and sulfide electrolyte are isolated and prevented from being directly subjected to reduction reaction, and coating microcracks generated by volume change in lithium metal circulation can be repaired, so that the possibility of interface exposure caused by coating breakage is reduced, and the service life of the lithium metal negative electrode is prolonged. Meanwhile, good interface contact can be kept, the synergistic effect of stable interface impedance, lithium dendrite inhibition and long-term cycle performance improvement is achieved, and the long-term cycle stability of the all-solid-state lithium battery is improved.

The invention relates to the technical field of lithium ion batteries, in particular to a preparation method of a lithium negative electrode with an ion / electron mixed conductor framework and application of the lithium negative electrode in the lithium ion battery. In order to solve the problems of lithium dendrite growth, volume expansion, corrosion and the like of the existing lithium negative electrode material in the battery cycle process, the invention provides an innovative solution that a double-fiber network skeleton consisting of a LiB compound and VGCF is constructed through a mechanical rolling method and a processing regulation and control process so as to enhance the electrode structure stability and inhibit the generation of lithium dendrites. The rate efficiency, the cycle life and the mechanical property of the prepared lithium negative electrode material are evaluated through a symmetric battery test, microstructure and electrochemical property analysis is carried out through TEM, SEM, XRD and other means, and the lithium negative electrode material has excellent comprehensive mechanical property, can inhibit volume expansion, simplifies the processing flow, and is suitable for large-scale production. And the method is suitable for commercial production of new energy batteries. By implementing the invention, the development of a lithium ion battery technology is expected to be promoted, and the requirements of modern society on an efficient and safe energy storage system are met.

The invention belongs to the field of lithium batteries, and particularly discloses an electrolyte for lithium metal, a preparation method of the electrolyte and a lithium metal battery. The electrolyte for the lithium metal battery comprises the following components in percentage by mole: 0.05%-1.5% of a solvent regulator, 10%-40% of lithium salt, 0.5%-8% of a first additive, 0.1%-1% of a second additive and the balance of a solvent. The electrolyte provided by the invention can effectively construct a compact negative electrode SEI film rich in organic and inorganic components, so that the deposition of lithium on a negative electrode current collector is more uniform, the generation of dead lithium and the consumption of active lithium are reduced, and the coulombic efficiency and the cycle performance of the lithium metal battery are improved; meanwhile, the electrolyte can effectively inhibit generation of lithium dendrites, the defect that the reaction activity of a traditional ester solvent and lithium is too high is overcome, and the coulombic efficiency and the cycle performance of the lithium metal battery are further improved.

The invention belongs to the technical field of polymer electrolyte membrane materials, and particularly relates to a high-ionic-conductivity polymer electrolyte membrane and a preparation method thereof.The preparation method comprises the steps that 1, PEO and lithium salt are added into a polar aprotic solvent, and the mixture is rapidly and violently stirred to be completely dissolved; (2) adding a cross-linking agent and a photoinitiator into the mixed solution, and violently stirring to obtain a mixed solution; and (3) coating the mixed solution in a polytetrafluoroethylene template, heating to remove the solvent, and performing ultraviolet radiation. According to the invention, a three-dimensional cross-linked network is formed by photocuring of an acrylate group of the cross-linking agent, PEO chain segment crystallization is inhibited, and lithium salt anions (such as TFSI-) are physically embedded. A benzene ring structure in a cross-linked network endows the electrolyte membrane with flexibility, mechanical property deterioration caused by a plasticizer or a diluent is avoided, the compact structure of the electrolyte membrane can inhibit lithium dendrite growth, the ionic conductivity reaches 1.7 * 10 <-4 > S / cm, and the electrochemical window reaches 4.9 V. The method is simple in process and suitable for large-scale preparation of the high-energy-density solid-state lithium battery.

The invention provides a lithium ion battery diaphragm as well as a preparation method and application thereof, and relates to the technical field of lithium ion batteries. Specifically, the lithium ion battery diaphragm comprises a polyimide nanofiber substrate layer, a dynamic cross-linked polyurethane self-repairing layer and a ceramic coating which are connected in sequence, and the lithium ion battery diaphragm also comprises poly (N-isopropylacrylamide) microspheres embedded into the layers. The technical problems that a traditional lithium battery diaphragm is prone to failure at a high temperature, the lithium dendrite penetration risk is high, and the electrolyte wettability is poor can be solved at the same time, through collaborative innovation of materials, structures and functions, comprehensive improvement of safety and electrochemical performance of a lithium ion battery is achieved through the diaphragm layer, and the lithium ion battery diaphragm has good application prospects.

The invention relates to the technical field of lithium ion batteries, and provides a surface coating modified halide solid electrolyte as well as a preparation method and application thereof. The method comprises the following steps: preparing a halide solid electrolyte, mixing the halide solid electrolyte with a lithium salt, and carrying out ball milling to obtain the surface coated and modified halide solid electrolyte. The coating layer is directly constructed on the surface of the halide solid electrolyte by adopting a mechanochemical ball milling method, traditional high-energy-consumption processes such as vapor deposition and high-temperature sintering are abandoned, and in-situ modification of the surface of the halide electrolyte is realized. After the lithium salt is used for coating, the side reaction between the halide solid-state electrolyte and lithium metal and the growth of lithium dendrites can be effectively reduced, so that the lithium stability of the halide solid-state electrolyte is improved.

The present invention relates to a composite separator for a lithium metal battery, a preparation method for a composite separator, and a lithium metal battery. The composite separator for a lithium metal battery comprises a separator layer and an NF@MOF membrane layer, wherein the NF@MOF membrane layer is an NF membrane on which an MOF material is grown in situ. In the present invention, the separator layer is combined with the NF@MOF membrane layer, and the in-situ grown MOF material provides high ionic conductivity and low interfacial impedance, such that the prepared composite separator integrates high mechanical strength, high flexibility, high electrolyte wettability, a high liquid retention rate and excellent ionic conductivity; and the synergistic effect exerted by the components of the composite separator can promote the uniform deposition and stripping of lithium metal, suppress the growth of lithium dendrites, and prevent separator penetration that may lead to a short circuit or even fire and explosion accidents, thereby prolonging the cycle life of the lithium metal battery and improving the safety performance thereof. Thus, the composite separator of the present invention has broad application prospects in terms of lithium metal batteries.

The invention discloses a preparation method for improving the cycle performance of a lithium negative electrode material, and relates to the technical field of lithium negative electrode materials. Lithium powder, Ti3C2Tx and polysiloxane are mixed and calcined to prepare the modified lithium metal material, Ti3C2Tx has a layered structure and provides a stable conductive frame, and the formation of the frame can provide electronic conductivity and effectively inhibit local current density in the charge-discharge process, so that deposition of lithium is limited in the structure, the defects of lithium dendrites are overcome, and the performance of the lithium metal material is improved. The functional group on the surface of the Ti3C2Tx has high binding energy with lithium metal, volume change of the pole piece in the long-time charging and discharging process can be reduced, due to introduction of polysiloxane, the surface energy of Li ion diffusion can be reduced through the Si-O functional group of polysiloxane, Li < + > is evenly distributed, the risk of SEI film breakage is reduced, and therefore the cycle performance of the battery end is improved.

The invention discloses a Sb-doped solid electrolyte, the chemical formula of the Sb-doped solid electrolyte is Li < 10 + 2x > P < 3-x > Sb < x > S < 12 > I, and x is more than or equal to 0.05 and less than or equal to 0.20. According to the invention, Sb with a specific content is doped to the P site of Li10P3S12I, and the Li content is increased, so that lattice distortion can be stabilized, the structural stability can be improved, and the lithium dendrite inhibition capability can be enhanced; a [SbS3] pyramid unit is formed, and a lithium ion transmission channel is widened, so that the solid electrolyte has good lithium ion migration capability; meanwhile, Sb ions and S < 2-> form strong covalent bonds, H2O erosion is inhibited, and air stability is enhanced. Therefore, the solid electrolyte disclosed by the invention has high ionic conductivity, interface stability, air stability and good inhibition capability on lithium dendrites. The solid electrolyte disclosed by the invention realizes a breakthrough in comprehensive performance, and is more suitable for industrialization requirements of solid-state batteries.

The application belongs to the technical field of lithium ion batteries, and relates to a solid-state electrolyte interface layer for a lithium metal negative electrode and an in-situ plasma construction method and application thereof. The core of the method is to use an organic-inorganic-alloy component precursor as a plasma reaction source, to control the mixing ratio and reaction conditions to perform plasma reaction on the surface of lithium metal, and to in-situ construct a unique gradient layered structure of an organic-inorganic-alloy composite artificial solid-state electrolyte interface layer. The outer layer of the solid-state electrolyte interface layer is a flexible organic phase, the middle layer is a rigid inorganic fast ion conductor, and the inner layer is a lithiumophilic alloy phase, which can synergistically inhibit lithium dendrite growth and significantly improve the interface stability of the lithium metal negative electrode. Meanwhile, the preparation method provided by the application is simple, rapid, efficient, environmentally friendly, mild in conditions and easy to control, significantly improves the cycle stability and coulombic efficiency of the lithium metal negative electrode, and is helpful to promote the development of high-energy-density lithium metal batteries.

The invention belongs to the field of lithium metal battery electrolytes, and particularly relates to a local high-concentration electrolyte, a preparation method of the local high-concentration electrolyte and application of the local high-concentration electrolyte in preparation of a lithium metal battery. The preparation method comprises the following steps: adding the lithium salt into the solvent, then adding the diluent, and stirring until the diluent is dissolved, so as to obtain the local high-concentration electrolyte. A certain proportion of DME cosolvent is introduced into the electrolyte, so that the concentration of the electrolyte can be diluted while an electrolyte solvation structure is added. When DME is added into an electrolyte solvation structure, a LiFSI-THF / DME-TTE local high-concentration electrolyte can be induced to form a solid electrolyte membrane (SEI) on a lithium metal negative electrode side, formation of lithium dendrites is inhibited, uniform deposition of lithium metal is induced, and the lithium deposition behavior is improved, so that the electrochemical performance of the battery is improved.

The invention belongs to the technical field of batteries, and particularly relates to a preparation method of coating slurry, a silver-carbon negative electrode plate, a preparation method of the silver-carbon negative electrode plate and a solid-state battery. Compared with the prior art, by controlling the agglomeration degree of the silver material in the negative electrode active coating, silver and carbon particles can be uniformly dispersed, and on the basis of avoiding the generation of lithium dendrites, attachment sites and spaces of the silver particles on the carbon particles are increased, so that the safety performance and the electrical performance of the battery are improved.

The invention discloses an energy storage battery internal short circuit prediction method and system based on dielectric frequency spectrum scanning, and belongs to the technical field of electric measurement and fault diagnosis. The method comprises the following steps: acquiring a dielectric constant change electric signal acquired by a preset sensor array and a multi-source environment electric signal acquired synchronously; dielectric spectrum electrical characteristic parameters are extracted based on the electrical signals; the electrical characteristic parameters and the multi-source environment electrical signals are fused, equivalent circuit model fitting is carried out, and electrical characterization signals of the volatility of the electrolyte and the growth state of the lithium dendrites are obtained; constructing a risk assessment model based on the electrical characterization signal; and monitoring the dynamic change of the electric signal in real time by using the risk assessment model, and predicting the internal short circuit risk. Multi-dimensional fusion and the AI algorithm are adopted, the short circuit risk in the energy storage battery can be accurately predicted in real time, active protection measures can be linked, and the prediction precision and the response speed are remarkably improved.

The invention relates to a covalent organic framework modified cellulose nanofiber composite diaphragm which is characterized in that cellulose nanofiber is used as a matrix, an amide type or amine type covalent organic framework layer is grown on the surface in situ, the loading capacity of a covalent organic framework is regulated and controlled, and a hierarchical pore structure with gradient pore diameter is constructed; the preparation method comprises the following steps: synthesizing a covalent organic framework precursor bonded with an imine bond on the surface of cellulose nanofiber in situ by a one-pot method under an acidic mixed solution and a heating condition, and regulating and synchronously reducing to convert into an amine type covalent organic framework; or after the imine bond bonded covalent organic framework is synthesized in two stages, the imine bond bonded covalent organic framework is selectively converted into an amide type covalent organic framework through oxidation modification; the obtained cellulose nanofiber compound coated with the covalent organic framework is subjected to the processes of film forming, solvent replacement, supercritical drying and the like, and the composite diaphragm is obtained; the diaphragm has excellent electrolyte wettability, high liquid absorption rate, good ionic conductivity and thermal stability, and can promote uniform transmission of lithium ions and inhibit growth of lithium dendrites.

The invention relates to the field of batteries, and particularly discloses a composite diaphragm of an asymmetric bifunctional coating, a preparation method of the composite diaphragm and a lithium ion battery. The lithium ion battery comprises a positive pole piece, a negative pole piece and a composite diaphragm with a bifunctional coating. Wherein the composite diaphragm with the dual-function coating comprises a base diaphragm, a positive electrode side functional layer and a negative electrode side functional layer, the positive electrode side functional layer comprises a metal organic framework (MOF) material, dissolution of metal ions of a positive electrode material can be effectively inhibited by virtue of an aperture effect, and electrolyte infiltration and liquid retention capabilities are improved; and the negative electrode side functional layer comprises MOF, a polymer and an inorganic filler, and can absorb electrolyte, regulate and control lithium ion distribution and inhibit lithium dendrite growth. The functional layers on the two sides can significantly improve the safety performance and lithium ion transmission dynamics of the diaphragm, and prolong the cycle life of the battery. Therefore, the lithium ion battery disclosed by the invention realizes high energy density, long cycle life and high safety.

The invention discloses a preparation method and application of an in-situ gel polymer electrolyte for a lithium-sulfur battery, and relates to a preparation method and application of a polymer electrolyte. The invention aims to solve the technical problems of rapid capacity attenuation and short cycle life of the existing lithium-sulfur battery. The method comprises the following steps: dissolving a lithium salt in a monomer or a solution formed by mixing the monomer and an ionic liquid, and then adding an initiator for polymerization to obtain the in-situ gel polymer electrolyte. The electrolyte can promote the formation of stable SEI, inhibit the growth of lithium dendrites, improve the ionic conductivity and accelerate the redox rate of positive electrode polysulfide, so that the cycle life of the lithium symmetric battery exceeds 1000h. The reversible specific discharge capacity of a lithium-sulfur battery assembled by using the electrolyte is 1242.0 mAh / g within the range of 1.7-2.8 V and under 0.2 C, the specific discharge capacity after 60 cycles is 953.7 mAh / g, the average coulombic efficiency is 97.5%, and the electrolyte can be used in the field of lithium-sulfur batteries.