Dynamic covalent non-fluorinated dry electrode binder, dry electrode sheet, and method of making same

Abstract

The embodiment of the application discloses a kind of dynamic covalent non-fluorine dry method electrode binder, dry method electrode piece and preparation method thereof, the binder includes the following components by mass fraction: non-fluorine thermoplastic polymer matrix 40-95 parts;Dynamic covalent functional unit 0.5-30 parts;Multifunctional crosslinking or anchoring component 0.1-25 parts.The binder of the application keeps powder fluidity in dry mixing stage, dynamic bond exchange and topological rearrangement occur in dry hot calendering stage, and form interface anchoring network between active material, conductive agent and current collector.After calendering cooling, binder forms stable crosslinking structure, thereby improving the peel strength of dry method electrode, anti-powder capacity and cycle stability.The application can avoid fluorine-containing binder such as PTFE, and is suitable for the preparation of positive electrode or negative electrode of lithium ion battery, sodium ion battery, solid-state battery and supercapacitor.

Description

Technical Field

[0001] This invention relates to the field of electrode manufacturing technology, and in particular to a dynamic covalent non-fluorine dry electrode binder, a dry electrode sheet, and a method for preparing the same. Background Technology

[0002] Existing dry electrode processes often use PTFE as a binder, utilizing its fiberization under shear stress to form a bonded network. This method has advantages such as being solvent-free, having low energy consumption, and being suitable for thick electrode manufacturing, but it also has problems such as fluorine content, high cost, narrow processing window, insufficient interfacial chemical adhesion, and difficulty in recycling.

[0003] While non-fluorinated binders can avoid fluorine-related issues, they still have the following drawbacks in dry electrode applications: (1) It is easy to agglomerate during dry mixing and is difficult to distribute evenly between the active material and the conductive agent; (2) The binder cannot be fully rearranged at the particle contact point during calendering, resulting in powdering or insufficient peel strength; (3) Cyclic expansion and contraction in thick electrodes can cause debonding between particles; (4) The adhesive only provides mechanical bonding and lacks interfacial anchoring for oxides, silicon oxide materials, carbon materials and current collectors; (5) Thermoplastic adhesives are prone to creep after softening, while thermosetting adhesives are difficult to adapt to dry calendering and reprocessing.

[0004] Therefore, there is a need for a non-fluorinated binder system that is flowable, rearrangeable, and adhesive under dry calendering conditions, and has high strength, creep resistance, and debonding resistance under battery operating conditions. Summary of the Invention

[0005] The technical problem to be solved by the embodiments of the present invention is to provide a dynamic covalent non-fluorine dry electrode binder, a dry electrode sheet and its preparation method, so as to achieve flowability, rearrangement and adhesion under dry calendering conditions, and high strength, creep resistance and debonding resistance under battery working conditions.

[0006] To address the aforementioned technical problems, this invention provides a dynamic covalent non-fluorinated dry electrode binder, comprising the following components by mass: 40-95 parts of non-fluorinated thermoplastic polymer matrix; 0.5-30 copies of dynamic covalent functional units; 0.1-25 parts of multifunctional cross-linked or anchored components; The non-fluorinated thermoplastic polymer matrix includes one or more of SEBS, SBS, SIS, EVA, POE, polyurethane, polyester, polyether, polyacrylate, polyolefin graft, and polycarbonate. The dynamic covalent functional units include one or more of the following: borate esters, dioxoborane, β-hydroxy esters, transesterification groups, imine bonds, oxime bonds, acylhydrazone bonds, disulfide bonds, and Diels-Alder reversible structures; Multifunctional cross-linked or anchored components include one or more of polyols, catechols, dopamine derivatives, tannic acid, lignin derivatives, polyvinyl alcohol, hydroxylated silica, alumina, and boehmite.

[0007] Furthermore, the binder also includes 0-30 parts of inorganic interface conditioning filler, which includes one or more of hydroxylated SiO2, Al2O3, boehmite, graphene oxide, and carbon nanotube surface modifiers.

[0008] Furthermore, the adhesive also includes 0-20 parts of an ion-conducting component, which includes one or more of polyether segments, sulfonates, lithium salt immobilizing groups, and zwitterionic groups.

[0009] Furthermore, the binder is in the form of powder, granules, core-shell particles, microcapsule particles, or pre-coated particles, with a D50 particle size of 0.1-50 μm.

[0010] Furthermore, the binder maintains powder flowability during the dry mixing stage, undergoes dynamic bond exchange and topological rearrangement at a dry hot calendering temperature of 80-150°C, and forms a cross-linked network after cooling; the cross-linked network remains stable at a battery operating temperature of 25-60°C.

[0011] Accordingly, embodiments of the present invention also provide a method for preparing a dynamic covalent non-fluorinated dry electrode binder, comprising: Step 1: Dynamic covalent group grafting is performed on non-fluorinated thermoplastic polymers using dynamic covalent functional units to obtain functionalized polymers; Step 2: The functionalized polymer is melt-blended with multifunctional crosslinking or anchoring components or inorganic interface-modifying fillers, cryogenically pulverized or spray-granulated to obtain dynamic covalent non-fluorinated dry electrode binder powder.

[0012] Accordingly, embodiments of the present invention also provide a dry electrode sheet, comprising the above-described dynamic covalent non-fluorinated dry electrode binder.

[0013] Accordingly, embodiments of the present invention also provide a method for preparing a dry electrode sheet, comprising: Step 1: Dry mix the dynamic covalent non-fluorine dry electrode binder powder with active particles and conductive agent to obtain a mixed powder; Step 2: Dry film formation of the obtained mixed powder; Step 3: Hot calendering is performed at 60-180°C and 10-300 MPa to cause dynamic bond exchange and interfacial anchoring of the binder, resulting in a calendered dry electrode film. Step 4: Combine the calendered dry electrode film with the current collector to obtain the dry electrode sheet.

[0014] Furthermore, in step 1, the binder is pre-coated onto the surface of the active particles and conductive agent by means of mechanical fusion, airflow shearing, high-speed mixing or ball milling.

[0015] Furthermore, the active particles are silicon-based anode materials.

[0016] The beneficial effects of this invention are as follows: This invention does not contain PTFE, PVDF, or other fluoropolymers, reducing environmental and recycling pressures; This invention does not rely on PTFE fiberization, making the process window easier to adjust; The dynamic covalent bonds of this invention promote binder flow and interface rearrangement during the calendering stage; This invention forms a cross-linked network after cooling, improving peel strength and anti-dust removal ability; This invention can enhance the adhesion of oxides, silicon oxide materials, and current collectors through structures such as borate esters, polyhydroxyl groups, and catechols; This invention can alleviate stress concentration during the cycling process of thick electrodes or silicon-based anodes; This invention can be combined with mechanical pre-coating processes to improve the uniformity of dry electrodes and the film-forming ability under low binder content.

[0017] Existing non-fluorinated thermoplastic binders typically rely on physical adhesion through polymer chain entanglement or softening. However, during dry calendering, they struggle to simultaneously satisfy requirements for powder dry-mix flowability, calendering interface rearrangement, and resistance to debonding after cycling expansion of the silicon-based anode. This invention introduces 3-aminophenylboronic acid into maleic anhydride-grafted SEBS and constructs a dynamic borate ester / polyhydroxyl interface network with tannic acid and hydroxylated nano-silica. This allows the binder to undergo dynamic bond exchange and interface rearrangement during hot calendering, maintaining its cross-linked anchoring structure after cooling and at battery operating temperatures. This simultaneously improves the self-supporting film-forming properties, peel strength, anti-powdering ability, cycle thickness recovery, and capacity retention of the SiOx / graphite silicon-based dry anode. Attached Figure Description

[0018] Figure 1 This is a SEM image of the SiOx / graphite composite powder prepared in Example 5 of this invention at 2000x magnification.

[0019] Figure 2 This is a SEM image of the particle surface of the SiOx / graphite composite powder prepared in Example 5 of this invention at 5000x magnification.

[0020] Figure 3 This is a SEM image of the particle contact area of ​​the SiOx / graphite composite powder prepared in Example 5 of this invention at 5000x magnification.

[0021] Figure 4 This is a surface SEM image at 10,000x magnification of the dry negative electrode film obtained by hot rolling of the SiOx / graphite composite powder prepared in Example 5 of this invention.

[0022] Figure 5 This is a surface SEM image of the dry negative electrode film obtained by hot rolling of SiOx / graphite composite powder prepared in Example 5 of this invention, under another field of view at 10,000x magnification. Detailed Implementation

[0023] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0024] The dynamic covalent non-fluorinated dry electrode binder of this invention comprises the following components by weight: 40-95 parts of non-fluorinated thermoplastic polymer matrix; 0.5-30 parts of dynamic covalent functional unit; and 0.1-25 parts of multifunctional crosslinking or anchoring component.

[0025] The non-fluorinated thermoplastic polymer matrix provides dry-mix powder film-forming properties, flexibility, and a calendered continuous phase. The non-fluorinated thermoplastic polymer matrix includes one or more of SEBS, SBS, SIS, EVA, POE, polyurethane, polyester, polyether, polyacrylate, polyolefin grafts, and polycarbonate.

[0026] Dynamic covalent functional units undergo exchange and network rearrangement during the hot calendering stage. These dynamic covalent functional units include one or more of the following: borate esters, dioxolane, β-hydroxy esters, transesterification groups, imine bonds, oxime bonds, acylhydrazone bonds, disulfide bonds, and Diels-Alder reversible structures.

[0027] The dynamic covalent network of the dynamic covalent functional unit of the present invention includes a thermoplastic continuous phase, a dynamic exchange phase, and an interface anchoring phase. The thermoplastic continuous phase ensures dry mixing dispersion and calendering film formation; the dynamic exchange phase undergoes topological rearrangement during hot calendering, causing the binder to migrate to the particle contact points; the interface anchoring phase forms reversible or semi-reversible interfacial interactions with the active material, conductive agent, and current collector.

[0028] Preferably, the dynamic covalent functional unit is a borate ester or dioxoborane structure. This structure can exchange or coordinate with the hydroxyl groups on the surface of polyols, catechols, polyphenols, or oxides, thereby forming an in-situ bonded network at the calendering interface of the dry electrode.

[0029] Multifunctional crosslinking or anchoring components are used to enhance the adhesion of binder particles, conductive agents, and current collectors at the interface. These components include one or more of the following: polyols, catechols, dopamine derivatives, tannic acid, lignin derivatives, polyvinyl alcohol, hydroxylated silica, alumina, and boehmite.

[0030] In one embodiment, the binder further includes 0-30 parts of inorganic interface modifier filler, which provides dynamic bond exchange points and interface enhancement points. The inorganic interface modifier filler includes one or more of hydroxylated SiO2, Al2O3, boehmite, graphene oxide, and carbon nanotube surface modifiers.

[0031] In one embodiment, the binder further includes 0-20 parts of an ion-conducting component. The ion-conducting component improves ion transport in thick electrodes. The ion-conducting component includes one or more of polyether segments, sulfonates, lithium salt immobilizing groups, and zwitterionic groups.

[0032] In one embodiment, the binder is in the form of powder, granules, core-shell particles, microcapsule particles, or pre-coated particles, with a D50 particle size of 0.1-50 μm, preferably 0.5-15 μm.

[0033] In one embodiment, the binder maintains powder flowability during the dry mixing stage. The binder has dynamic bond exchange capability in the range of 60-180°C, preferably undergoing dynamic bond exchange and topological rearrangement at a dry hot calendering temperature of 80-150°C, forming a cross-linked network after cooling; the cross-linked network remains stable at a battery operating temperature of 25-60°C.

[0034] The preparation method of the dynamic covalent non-fluorine dry electrode binder in this embodiment of the invention includes steps 1 and 2.

[0035] Step 1: Dynamic covalent group grafting is performed on non-fluorinated thermoplastic polymers using dynamic covalent functional units to obtain functionalized polymers containing borate esters, dioxoboranes, or transesterification groups.

[0036] Step 2: The functionalized polymer is melt-blended, cryogenically pulverized, or spray-granulated with multifunctional crosslinking or anchoring components (polyols, polyphenols, catechols) or inorganic interface-modifying fillers to obtain dynamic covalent non-fluorinated dry electrode binder powder.

[0037] The binder of this invention maintains powder flowability during the dry mixing stage and undergoes dynamic bond exchange and topological rearrangement during the dry hot calendering stage, forming an interfacial anchoring network between the active material, conductive agent, and current collector. After calendering and cooling, the binder forms a stable cross-linked structure, thereby improving the peel strength, anti-powdering ability, and cycle stability of the dry electrode.

[0038] The dry electrode sheet of this invention includes a dynamic covalent non-fluorine dry electrode binder, active particles, a conductive agent, and a current collector.

[0039] The method for preparing the dry electrode sheet according to the present invention includes steps 1 to 4.

[0040] Step 1: Dry mix the dynamic covalent non-fluorine dry electrode binder powder with active particles and conductive agent to obtain a mixed powder.

[0041] Step 2: Dry film formation of the obtained mixed powder.

[0042] Step 3: Hot-calendering at 60-180°C and 10-300 MPa causes dynamic bond exchange and interfacial anchoring of the binder, resulting in a calendered dry electrode film. The hot-pressing triggered rearrangement of this invention: the binder remains a solid powder during the dry mixing stage; during the calendering stage, dynamic covalent bond exchange occurs after heating and pressure, causing polymer chain segments to rearrange at particle contact points.

[0043] In-situ anchoring at the interface: Borate esters, catechols, polyhydroxy or polyphenol structures can form dynamic covalent or coordination interactions with hydroxyl / metal sites on the surface of NCM, LFP, LMFP, SiOx, Al foil, Cu foil or inorganic coatings.

[0044] Step 4: Combine the calendered dry electrode film with the current collector to obtain a dry electrode sheet. Crosslinking and shaping after cooling: After calendering, the exchange rate of the dynamic network decreases at lower temperatures, forming a stable crosslinked network that is resistant to peeling and powder shedding.

[0045] In one implementation, in step 1, the binder is pre-coated onto the surface of the active particles and the conductive agent by means of mechanical fusion, airflow shearing, high-speed mixing or ball milling.

[0046] In one embodiment, the active particles are silicon-based anode materials, and the dry-process electrode sheet is a dry-process anode film. The current collector is aluminum foil, copper foil, carbon-coated aluminum foil, carbon-coated copper foil, stainless steel foil, foamed metal, or a porous conductive substrate. This invention avoids fluorine-containing binders such as PTFE and is suitable for the preparation of positive or negative electrodes for lithium-ion batteries, sodium-ion batteries, solid-state batteries, and supercapacitors. Positive electrode: LFP, LMFP, NCM, NCA, LCO, lithium-rich manganese-based, sodium-ion layered oxide, Prussian blue-based materials. Negative electrode: graphite, hard carbon, soft carbon, silicon-carbon, SiOx, lithium metal composite negative electrode, sodium-ion hard carbon negative electrode.

[0047] The dry electrode sheet of the present invention features adaptive cyclic stress: during the charging and discharging process, the dynamic bonds in the local high-stress region can be slowly rearranged, reducing interfacial debonding caused by particle expansion.

[0048] The present invention is non-fluorinated and recyclable: it does not rely on PTFE fiberization, avoids fluorinated binders, and has the potential for thermosetting or repair.

[0049] The pre-coating synergistic enhancement of this invention: when combined with mechanical pre-coating process, it can improve the utilization rate of binder and the uniformity of dry electrode.

[0050] The following examples and comparative examples focus on SiOx / graphite silicon-based anodes. Unless otherwise specified, all groups used the same batch of raw materials. The dry-process anode films comprised, by mass percentage, 74.5% artificial graphite, 20.0% SiOx, 1.0% conductive carbon black, 0.5% carbon nanotubes, and 4.0% corresponding binder, totaling 100%. All groups used the same target areal density, the same compaction density, and the same battery assembly and formation conditions to ensure that the test results could be compared across groups.

[0051] The general binder preparation conditions are as follows: After vacuum drying of each raw material, maleic anhydride-grafted SEBS and 3-aminophenylboronic acid are mixed at 170°C and 80 r / min for 8 min under nitrogen protection; the temperature is adjusted to 140°C, tannic acid and hydroxylated nano-silica are added, and the mixture is continued to be mixed at 60 r / min for 6 min; after cooling, the material is subjected to low-temperature cryogenic pulverization to obtain binder powder with D50 of 6-12 μm and D90 not higher than 30 μm.

[0052] The general electrode preparation conditions are as follows: artificial graphite, SiOx, conductive carbon black, carbon nanotubes and binder are premixed at 600 r / min for 5 min, and then mixed at 1800 r / min for 12 min; the resulting mixed powder is rolled three times in stages at a roller temperature of 110°C and a linear speed of 0.3 m / min, with roller gaps of 420 μm, 280 μm and 200 μm respectively, to form a self-supporting negative electrode film; the negative electrode film is thermally bonded to carbon-coated copper foil at 110°C and 2.0 MPa for 60 s.

[0053] Example 1: Silicon-based dry anode with low dynamic connection density.

[0054] By weight, the binder comprises 96.5 parts maleic anhydride-grafted SEBS, 1.0 part 3-aminophenylboronic acid, 1.5 parts tannic acid, and 1.0 part hydroxylated nano-silica. A silicon-based dry-process negative electrode sheet was prepared according to general binder preparation conditions and general electrode preparation conditions.

[0055] Example 2: Silicon-based dry anode with central formulation.

[0056] By weight, the binder comprises 95.0 parts maleic anhydride-grafted SEBS, 2.0 parts 3-aminophenylboronic acid, 2.0 parts tannic acid, and 1.0 part hydroxylated nano-silica. A silicon-based dry-process negative electrode sheet was prepared according to general binder preparation conditions and general electrode preparation conditions.

[0057] Example 3: Silicon-based dry anode with high polyphenol anchoring components.

[0058] By weight, the binder comprises 94.0 parts maleic anhydride-grafted SEBS, 1.5 parts 3-aminophenylboronic acid, 3.5 parts tannic acid, and 1.0 part hydroxylated nano-silica. A silicon-based dry-process negative electrode sheet was prepared according to general binder preparation conditions and general electrode preparation conditions.

[0059] Example 4: Silicon-based dry anode containing polyether ion-conducting components.

[0060] By weight, the binder comprises 93.0 parts maleic anhydride-grafted SEBS, 1.5 parts 3-aminophenylboronic acid, 2.0 parts amino-terminated polyethylene glycol, 2.5 parts tannic acid, and 1.0 part hydroxylated nano-silica; the number average molecular weight of the amino-terminated polyethylene glycol is 1800-2200. During the first stage of mixing, the amino-terminated polyethylene glycol is added together with the maleic anhydride-grafted SEBS and 3-aminophenylboronic acid, and the remaining conditions are the same as in Example 2.

[0061] Example 5: Mechanically pre-coated silicon-based dry anode.

[0062] This embodiment uses the binder formulation from Example 2, with the electrode composition remaining unchanged. First, artificial graphite, SiOx, and the binder are added to a mechanical fusion apparatus and treated for 8 minutes at a rotor speed of 2500 r / min and a jacket temperature of 45°C. Then, conductive carbon black and carbon nanotubes are added, and the mixture is treated for 4 minutes at 1500 r / min. Subsequently, a silicon-based dry-process negative electrode sheet is prepared using the same hot-rolling and carbon-coated copper foil composite conditions as in Example 2.

[0063] The dynamic covalent non-fluorinated dry electrode binder of this embodiment comprises, by weight, 95 parts of maleic anhydride-grafted SEBS, 2 parts of 3-aminophenylboronic acid, 2 parts of tannic acid, and 1 part of hydroxylated nano-silica; the dry anode film comprises, by weight percentage, 74.5% artificial graphite, 20.0% SiOx, 1.0% conductive carbon black, 0.5% carbon nanotubes, and 4.0% of the above binder.

[0064] Comparative Example 1: SEBS-g-MA adhesive without dynamic functional components.

[0065] By weight, the binder comprises 99.0 parts maleic anhydride-grafted SEBS and 1.0 part hydroxylated nano-silica, without the addition of 3-aminophenylboronic acid and tannic acid. The mixture is kneaded at 140°C and 60 r / min for 6 min, then cooled and freeze-pulverized. Silicon-based dry-process negative electrode sheets are prepared using the same electrode composition and general electrode preparation conditions.

[0066] Comparative Example 2: SEBS-g-MA adhesive containing only tannic acid.

[0067] By weight, the binder comprises 97.0 parts maleic anhydride-grafted SEBS, 2.0 parts tannic acid, and 1.0 part hydroxylated nano-silica, without the addition of 3-aminophenylboronic acid. The mixture is kneaded at 140°C and 60 r / min for 6 min, then cooled and freeze-pulverized. Silicon-based dry-process negative electrode sheets are prepared using the same electrode composition and general electrode preparation conditions.

[0068] The test methods for the various embodiments and comparative examples of the present invention are as follows: To evaluate the processing performance, mechanical properties, silicon-based anode expansion failure, electrochemical performance, and interfacial kinetics characteristics of the embodiments and comparative examples of the present invention, the following methods were used for testing. Unless otherwise specified, at least three parallel tests were conducted on each group of samples, and the average value of the results was taken.

[0069] 1. Self-supporting film formation: The mixed powders obtained from each embodiment and comparative example were subjected to dry calendering under the same roll temperature, linear speed, and roll gap conditions. It was observed whether the resulting film could continuously pass through the calendering roll and form a self-supporting film. After the film was cut into 50 mm × 50 mm sample sizes, it was observed whether there were any cracks, edge cracks, local powder shedding, holes, or film surface discontinuities, and the film formation was evaluated accordingly.

[0070] 2. Membrane tensile strength and elongation at break: The dry-process negative electrode film was cut into strip-shaped specimens, with dimensions of 50 mm × 10 mm. Before testing, the specimen thickness was measured using a thickness gauge, and the average value at three locations was used as the basis for calculating the cross-sectional area. Tensile testing was performed using a universal testing machine with a clamp spacing of 30 mm and a tensile speed of 5 mm / min. The maximum load and fracture displacement at specimen breakage were recorded.

[0071] The tensile strength of the membrane is calculated using the following formula: Membrane tensile strength = maximum load / initial cross-sectional area of ​​the specimen; Elongation at break is calculated using the following formula: Elongation at break = Elongation at break / Initial clamping distance × 100%.

[0072] 3. Number of times the product is bent 180° until it cracks: The dry-process negative electrode film was cut into 50 mm × 10 mm samples and bent 180° back and forth using a 5 mm diameter rod as the bending axis. Each complete forward and reverse bend was recorded as one bend. The film surface was observed using an optical microscope or visually. When the film showed through cracks, obvious edge cracks, or continuous pulverization, the number of bends was recorded.

[0073] 4. 180° peel strength: The dry-process negative electrode film was thermally laminated with carbon-coated copper foil and then cut into samples with a width of 10 mm. A 180° peel test was performed, with one end of the current collector fixed and the other end of the electrode film peeled off at a speed of 50 mm / min. The average peel force within the stable peel range was recorded.

[0074] Peel strength is calculated using the following formula: Peel strength = Average peel force / Specimen width; The unit is N / m.

[0075] 5. Powder drop rate: The dry-process negative electrode sheet was cut into 50 mm × 50 mm samples, and the initial mass m0 was measured. 3M 600 transparent tape was applied to the electrode film surface and rolled back and forth with approximately 2 kg of adhesive once. After standing for 10 seconds, the tape was peeled off at a uniform speed in a 180° direction. This process was repeated three times. After removing the detached powder, the sample mass was weighed again and recorded as m1.

[0076] The powder loss rate is calculated using the following formula: Powder shedding rate = (m0 - m1) / m0 × 100%; The powder shedding rate test after cycling was conducted using an electrode sheet that had undergone 100 cycles. After disassembly, the electrode sheet was cleaned by DMC and vacuum dried before being tested using the method described above.

[0077] 6. Electrolyte wetting time: The electrode sheet was cut into 50 mm × 50 mm samples and placed on a horizontal platform. 5 μL of electrolyte was added dropwise using a micropipette. The electrolyte was 1 mol / L LiPF6, with EC / DEC / EMC as the solvent (volume ratio 1:1:1) and containing 10 wt% FEC. The time required for the droplet to spread completely or be absorbed from the electrode surface was recorded. A shorter wetting time indicates better electrolyte wettability.

[0078] 7. Electrode thickness and expansion rate: The electrode thickness is tested using a high-precision thickness gauge. The testing pressure remains consistent, for example, 0.5 MPa, or is performed according to the equipment's standard pressure. At least five locations are tested for each electrode, and the average value is taken.

[0079] The initial thickness is denoted as T0. After the battery completes formation, it is disassembled or its thickness is measured in situ during its first full charge, and the result is recorded as T0. c1 T was recorded after the first discharge. d1 After 50 and 100 cycles, T was recorded under full charge and discharge conditions, respectively. c50 T d50 T c100 T d100 .

[0080] The full charge expansion rate over 100 weeks is calculated using the following formula: 100-week full charge expansion rate = (T) c100 - T0) / T0 × 100%; The irreversible thickness growth rate over 100 weeks is calculated using the following formula: 100-week irreversible thickness growth rate = (T d100 - T0) / T0 × 100%; The thickness recovery rate over 100 weeks is calculated using the following formula: Thickness recovery rate over 100 weeks = (T) c100 - T d100 ) / (T c100 - T0) × 100%.

[0081] 8. Electrochemical performance testing: The silicon-based dry-process negative electrode sheets prepared in the various examples and comparative examples were used as working electrodes, and lithium metal sheets were used as counter electrodes to assemble CR2032 coin cell half-cells. Celgard 2400 polyolefin membranes were used as separators, and the electrolyte was 1 mol / L LiPF6 with EC / DEC / EMC solvent in a volume ratio of 1:1:1, containing 10 wt% FEC. The electrolyte addition amount was 80 μL. The cells were allowed to stand for 12 h after assembly.

[0082] The test temperature was 25±2°C, and the test voltage range was 0.01-1.5 V. The first charge and discharge was performed at a rate of 0.1C, and the first charge specific capacity, first discharge specific capacity, and first coulombic efficiency were recorded.

[0083] The initial coulomb efficiency is calculated using the following formula: Initial coulombic efficiency = (Initial discharge specific capacity / Initial charge specific capacity) × 100%; In the rate performance test, charge and discharge at 0.5C or 1C rates and record the corresponding discharge specific capacity.

[0084] In the cycle performance test, the discharge capacity was recorded at 1C rate for 100 cycles, and the discharge capacity was recorded at the 1st, 50th and 100th cycles.

[0085] Capacity retention rate is calculated using the following formula: Capacity retention rate = discharge capacity in week n / discharge capacity in week 1 × 100%.

[0086] 9. AC impedance test: AC impedance testing was performed using an electrochemical workstation. Before testing, the battery was adjusted to 50% SOC and allowed to rest for 2 hours. The test frequency range was 100 kHz to 0.01 Hz, with a perturbation voltage of 5 mV. The test subjects were batteries after formation and batteries after 100 cycles.

[0087] Equivalent circuit fitting based on the Nyquist plot yields the ohmic internal resistance Rs and the charge transfer impedance Rct. Rs corresponds to the intersection of the high-frequency region and the real axis, while Rct corresponds to the diameter of the semicircle in the mid-to-high frequency range.

[0088] 10. Stress relaxation t50 test: The dry negative electrode film was cut into 30 mm × 5 mm samples and placed in the fixture of a dynamic thermomechanical analyzer or a universal testing machine. A constant strain of 5% was applied in tensile mode to bring the initial stress to a stable value σ0. Then, the strain was kept constant and the stress decay curve over time was recorded.

[0089] Tests were conducted at 25°C and 110°C, respectively. The time required for the stress to decay to 50% of the initial stress was defined as t50.

[0090] The shorter the t50, the faster the stress relaxation ability of the binder network at that temperature. If the t50 is longer at 25°C and significantly shorter at 110°C, it indicates that the binder remains stable at the battery operating temperature and has dynamic rearrangement ability near the hot calendering temperature.

[0091] 11. SEM morphology observation: The SiOx / graphite composite powder obtained in Example 5 was directly fixed onto conductive adhesive. After gold sputtering for 60 s, the surface morphology of the powder was observed using a scanning electron microscope. The SEM acceleration voltage was 15 kV, and the coating state, particle contact area, and pore structure of the composite powder were observed at 2000x and 5000x magnification, respectively.

[0092] The dry-process negative electrode film obtained in Example 5 was cut and fixed on a sample stage. After conductivity treatment, the surface morphology of the negative electrode film was observed at 10,000x magnification to evaluate particle packing, pore distribution, binder bonding, and film continuity. SEM images of the SiOx / graphite composite powder and negative electrode film prepared in Example 5 are shown below. Figures 1-5 .

[0093] 12. Peel strength and powder loss rate after cycling: After 100 cycles, the battery was disassembled in a discharged state, the negative electrode was removed, and the surface residual electrolyte was cleaned with DMC and dried under vacuum. The dried electrode sheets were then tested according to the 180° peel test method and the powder shedding rate test method described above to evaluate the interfacial adhesion retention ability and anti-powdering ability after cycling.

[0094] The dry processing and initial mechanical properties of the various embodiments and comparative examples of the present invention are shown in Table 1.

[0095] Table 1

[0096] Table 2 shows the expansion failure data of silicon-based anodes in various embodiments and comparative examples of the present invention.

[0097] Table 2

[0098] The thickness calculation formulas are as follows: full-fill expansion rate = (Tc100-T0) / T0×100%; irreversible thickness growth rate = (Td100-T0) / T0×100%; thickness recovery rate = (Tc100-Td100) / (Tc100-T0)×100%.

[0099] The electrochemical performance data of each embodiment and comparative example of the present invention are shown in Table 3.

[0100] Table 3

[0101] The impedance, rheological and mechanistic characterization data of each embodiment and comparative example of the present invention are shown in Table 4.

[0102] Table 4

[0103] This invention uses a non-fluorinated thermoplastic elastomer as the continuous phase, a borate ester / dioxoborane dynamic bond as the rearrangeable crosslinking phase, and a polyhydroxy / catechol component as the interface anchoring phase. Topological rearrangement, interface anchoring, and cooling shaping occur during dry hot calendering, and local stress is released during cycling.

[0104] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A dynamic covalent non-fluorine dry electrode binder, characterized in that, The following components are included by mass: 40-95 parts of non-fluorinated thermoplastic polymer matrix; 0.5-30 copies of dynamic covalent functional units; 0.1-25 parts of multifunctional cross-linked or anchored components; The non-fluorinated thermoplastic polymer matrix includes one or more of SEBS, SBS, SIS, EVA, POE, polyurethane, polyester, polyether, polyacrylate, polyolefin graft, and polycarbonate. The dynamic covalent functional units include one or more of the following: borate esters, dioxoborane, β-hydroxy esters, transesterification groups, imine bonds, oxime bonds, acylhydrazone bonds, disulfide bonds, and Diels-Alder reversible structures; Multifunctional cross-linked or anchored components include one or more of polyols, catechols, dopamine derivatives, tannic acid, lignin derivatives, polyvinyl alcohol, hydroxylated silica, alumina, and boehmite.

2. The dynamic covalent non-fluorinated dry electrode binder as described in claim 1, characterized in that, The binder also includes 0-30 parts of inorganic interface conditioning filler, which includes one or more of hydroxylated SiO2, Al2O3, boehmite, graphene oxide, and carbon nanotube surface modifiers.

3. The dynamic covalent non-fluorinated dry electrode binder as described in claim 1, characterized in that, The adhesive further includes 0-20 parts of an ion-conducting component, which includes one or more of polyether segments, sulfonates, lithium salt immobilizing groups, and zwitterionic groups.

4. The dynamic covalent non-fluorinated dry electrode binder as described in claim 1, characterized in that, The binder is in the form of powder, granules, core-shell particles, microcapsule particles, or pre-coated particles, with a D50 particle size of 0.1-50 μm.

5. The dynamic covalent non-fluorinated dry electrode binder as described in claim 1, characterized in that, The binder maintains powder flowability during the dry mixing stage, undergoes dynamic bond exchange and topological rearrangement at dry hot calendering temperatures of 80-150°C, and forms a cross-linked network after cooling; the cross-linked network remains stable at battery operating temperatures of 25-60°C.

6. A method for preparing a dynamic covalent non-fluorinated dry electrode binder as described in any one of claims 1-5, characterized in that, include: Step 1: Dynamic covalent group grafting is performed on non-fluorinated thermoplastic polymers using dynamic covalent functional units to obtain functionalized polymers; Step 2: The functionalized polymer is melt-blended, cryogenically pulverized, or spray-granulated with multifunctional crosslinking or anchoring components or inorganic interface-modifying fillers to obtain dynamic covalent non-fluorinated dry electrode binder powder.

7. A dry-process electrode sheet, characterized in that, Includes the dynamic covalent non-fluorinated dry electrode binder as described in any one of claims 1-5.

8. A method for preparing a dry electrode sheet as described in claim 7, characterized in that, include: Step 1: Dry mix the dynamic covalent non-fluorine dry electrode binder powder with active particles and conductive agent to obtain a mixed powder; Step 2: Dry film formation of the obtained mixed powder; Step 3: Hot calendering is performed at 60-180°C and 10-300 MPa to cause dynamic bond exchange and interfacial anchoring of the binder, resulting in a calendered dry electrode film. Step 4: Combine the calendered dry electrode film with the current collector to obtain the dry electrode sheet.

9. The method for preparing a dry electrode sheet as described in claim 8, characterized in that, In step 1, the binder is pre-coated onto the surface of the active particles and conductive agent by means of mechanical fusion, airflow shearing, high-speed mixing or ball milling.

10. The method for preparing a dry electrode sheet as described in claim 8, characterized in that, The active particles are silicon-based anode materials, and the dry electrode sheet is a dry anode film.

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