50results about How to "Increase gram capacity" patented technology

The invention provides a carbon-coated europium-doped sodium ferric sulfate positive electrode material and a preparation method thereof, a sodium ion battery and electric equipment, and relates to the field of sodium ion batteries. The carbon-coated europium-doped sodium ferric sulfate positive electrode material comprises an inner core and a carbon coating layer coating the inner core, wherein the inner core comprises europium-doped sodium ferric sulfate; the chemical formula of the carbon-coated europium-doped sodium ferric sulfate positive electrode material is Na < 2.4 > Fe < 1.8-3x > Eux (SO4) 3 / C, and x is more than 0 and less than or equal to 0.1. The sodium ferric sulfate is subjected to carbon coating and europium doping, so that the specific discharge capacity and the rate capability of the positive electrode material can be effectively improved.

The invention provides a positive pole piece, a preparation method thereof and a battery, and aims to solve the technical problems that the capacity of LMFP is difficult to effectively exert and the cycle life of the battery is poor. The positive pole piece comprises a current collector and a first active material layer and a second active material layer which are arranged on the current collector, and the first active material layer and the second active material layer are sequentially distributed in the direction away from the current collector; the first active material layer and the second active material layer both contain lithium manganese iron phosphate; the first active material layer further comprises a first conductive agent and a first lithium supplement agent, and the second active material layer further comprises a second conductive agent and a second lithium supplement agent; wherein the gram volume K1 of the first lithium supplement agent is greater than the gram volume K2 of the second lithium supplement agent; the mass percentage D1 of the first conductive agent in the first active material layer is greater than the mass percentage D2 of the second conductive agent in the second active material layer.

The invention provides a preparation method and application of a lithium ion battery negative electrode plate, the lithium ion battery negative electrode plate comprises a negative electrode current collector, the surface of the negative electrode current collector comprises a first active material layer and a second coating layer, the first active material layer is prepared by a magnetron sputtering method, and the second coating layer is prepared by a magnetron sputtering method. The second coating layer is coated on the first active substance layer, the first active substance layer comprises a silicon-based thin film prepared by vacuum magnetron sputtering, and the second coating layer comprises a graphite active substance, a conductive agent, a dispersing agent and a binder. The internal aperture structure of the negative plate inhibits the expansion of the silicon-based material and improves the cycle stability of the battery.

The invention relates to the technical field of lithium ion battery negative electrode materials, in particular to a silicon-carbon negative electrode material, a preparation method thereof, a negative electrode plate and a lithium ion battery. The silicon-carbon negative electrode material comprises a composite fiber, wherein the composite fiber comprises a core layer and a carbon coating layer; the core layer has a pore structure and comprises a carbon skeleton and a silicon material; in the cross section of the composite fiber, the area of the pore structure is S pore, the area of the silicon element is S silicon, the area of the carbon element is S carbon, and 0.5 < = S pore / (S silicon + S carbon) < = 2. The silicon material in the core layer can provide higher gram volume, and the carbon skeleton can provide mechanical strength and enhance the conductivity of the material; the core layer has a pore structure and can provide a buffer space when the silicon material is charged, so that the cycle performance is improved; the carbon coating layer can effectively reduce the specific surface area of the material, avoids direct contact between the silicon material and an electrolyte, and improves the initial coulombic efficiency; the silicon material can be ensured to have enough buffer space by meeting the relational expression, and the cycle performance can be further improved.

The invention discloses a hard carbon material and a preparation method thereof, a hard carbon negative pole piece and a sodium ion battery, and relates to the technical field of batteries. The preparation method of the hard carbon material comprises the following steps: sequentially carrying out primary screening, crushing, carbonization, secondary crushing, grinding and impurity removal on hemp stalks to obtain a hard carbon precursor; and sequentially carrying out secondary grinding, primary sintering, secondary sintering, washing and drying on the hard carbon precursor to obtain the hard carbon material. The preparation operation is relatively simple, the price is relatively low, the cost of the hard carbon material can be reduced, meanwhile, the hard carbon material can be obtained from linen manufacturers on a large scale, and large-scale collection is facilitated; besides, the hard carbon material taking the hemp stalks as the raw material is applied to the negative pole piece of the sodium-ion battery, and the gram volume of the hard carbon material is relatively high, so that the energy density of the sodium-ion battery is favorably improved.

The invention provides a regenerated graphite composite negative electrode material, a preparation method of the regenerated graphite composite negative electrode material and a secondary battery. The preparation method of the regenerated graphite composite negative electrode material comprises the following steps: firstly, placing waste graphite in a strong alkali solution for pore-forming treatment to obtain porous regenerated graphite; then, in an inert atmosphere, depositing silane gas on the surface and in pores of the porous regenerated graphite to obtain a composite material; and mixing and granulating the composite material, a binder and a conductive agent, and performing post-treatment to obtain the regenerated graphite composite negative electrode material. According to the preparation method of the regenerated graphite composite negative electrode material provided by the invention, the regenerated graphite composite negative electrode material with relatively high gram volume, cycling stability and fast charging performance can be prepared.

The invention discloses a carbon composite titanium / fluorine double-doped composite sodium ferric phosphate composite material, the stoichiometric formula of which is Na < 4 > Fe < 3-2x > Ti < x > (PO4) < 2-y > F < 3 > y P < 2 > O < 7 > / C, xlt; 0 lt, 0.04, 0 lt; yt; Yt; 0.2 part; and the hollow bowl-shaped porous structure is formed. According to the invention, the intrinsic conductivity of the NFPP can be effectively improved, the problem of impurity phase of NaFePO4 can be controlled, and the gram capacity of the NFPP can be improved; when the carbon composite titanium / fluorine double-doped composite sodium ferric phosphate composite material is used as a sodium ion battery positive electrode material, relatively good rate capability, long cycle stability and the like can be shown; and the related preparation cost is low, the method is environment-friendly, and industrial application is facilitated.

The invention provides a positive electrode material of a sodium ion secondary battery, a preparation method of the positive electrode material, the sodium ion secondary battery and electric equipment, and relates to the field of sodium ion batteries. The chemical formula of the positive electrode material of the sodium ion secondary battery provided by the invention is NaaNixFeyMnzM1-x-y-zO2, wherein a is more than or equal to 0.9 and less than or equal to 1.05, x is more than 0 and less than 1.0, y is more than 0 and less than 1.0, z is more than 0 and less than 1.0, 1-x-y-z is more than 0 and less than 1, and the element M is a metal element of which the valence is more than or equal to 2. According to the positive electrode material of the sodium ion secondary battery provided by the invention, the positive electrode active material is doped with the metal element containing the valence of + 2, + 3, + 4, + 5 or + 6 to regulate and control the molar weight of O-ions in lattice oxygen relative to O < 2-> when the positive electrode material of a sodium ion O3 structure is in a full charge state, so that the bonding strength of the doped metal element and oxygen is improved, and the content of high-activity O-free oxygen is reduced; and the sodium-electric O3 structure has relatively high structural stability.

The preparation method comprises the following steps: S1, mixing a first lithium source, a first iron source, a first manganese source, a first phosphorus source, a first doped metal source, a first carbon source and a first solvent to obtain a first mixed slurry, and carrying out spray drying and first sintering to obtain a seed crystal; s2, mixing the seed crystal, a second lithium source, a second iron source, a second manganese source, a second phosphorus source, a second doped metal source, a second carbon source and a second solvent to obtain second mixed slurry, performing spray drying, and performing secondary sintering to obtain a lithium manganese iron phosphate composite material; the iron sources are + 3-valent iron sources, and the manganese sources are non-+ 2-valent manganese sources; and the ratio of the total amount of the iron element in the first iron source and the manganese element in the first manganese source to the mass of the first carbon source is 1mol: (3.0-7.5) g. By using the first carbon source, the gram volume of the lithium manganese iron phosphate composite material can be improved.

The invention relates to the technical field of batteries, in particular to a negative active material, a negative plate comprising the negative active material and a battery. The negative electrode active material comprises silicon-carbon composite particles; the particle size Dn10 of the silicon-carbon composite particles is 1-8 [mu] m; the average sphericity degree of the silicon-carbon composite particles is 0.6-1; the silicon-carbon composite particles have closed pores and open pores, and the volume V1 of the closed pores and the volume V2 of the open pores satisfy 0.2 < = V1 / V2 < = 2000. The negative electrode active material disclosed by the invention has relatively high ionic conductivity and electronic conductivity and relatively high structural stability while relatively high gram volume is ensured. Comprising the negative electrode active material disclosed by the invention can give consideration to relatively good initial coulombic efficiency, rate capability, low-temperature performance and cycling stability.

The invention discloses a lithium supplement material and a preparation method thereof, the lithium supplement material is lithium squarate or a lithium squarate-containing composite material, and the lithium supplement additive can effectively supplement the lithium content in a lithium battery and improve the capacity of the lithium battery in long-term circulation. The preparation method comprises the following steps: mixing squaric acid and a lithium source in a solvent, or mixing squaric acid, the lithium source and a composite material in the solvent, and carrying out spray drying on the mixed solution to obtain the lithium squarate material. The preparation method provided by the invention has the advantages of simple process, good environmental protection property and the like, and is suitable for industrial application of the lithium squarate material.

The present invention discloses a preparation method and application of pre-magnesium silicon oxide, belonging to the technical field of lithium ion batteries. The steps of the preparation method include: S1, weighing silicon oxide, magnesium source and carbon source according to the mass ratio, grinding and mixing to obtain a precursor; S2, placing the precursor on a carrier of a Joule heating device, connecting the power supply of the electrode in the Joule heat treatment device under a protective atmosphere, performing thermal shock treatment, and obtaining pre-magnesium silicon oxide. Rapid heating is achieved by Joule heating, and the reaction of magnesium source and silicon oxide is precisely controlled, so that the reaction is more sufficient and efficient, and the initial charge and discharge efficiency, charge and discharge rate performance and cycle stability of the battery capacity of the lithium battery are improved.

This invention provides a positive electrode active material and its application. The positive electrode active material of this invention comprises matrix particles including lithium metal oxide and a graphite coating layer covering at least a portion of the surface of the matrix particles; the lithium metal oxide has the structure shown in Formula 1; in the X-ray diffraction pattern, the lithium metal oxide is a cubic crystal system in space group Cmca, and has a 002 peak with a 2θ of 17.9°–18.1° and a 131 peak with a 2θ of 67.0°–67.5°; Li n‑y Na y Co 1‑a M a O2, Equation 1, where 0.6 ≤ n ≤ 0.8, 0 < y ≤ 0.05, 0 ≤ a < 0.2; and M is a doping element. The unique composition and crystal structure of this positive electrode active material help improve the battery's specific capacity and cycle performance, especially under high-voltage conditions, enabling the battery to maintain excellent performance.

The invention belongs to the technical field of sodium batteries, and particularly relates to a modified sodium ion battery positive electrode material and a preparation method and application thereof. The preparation method comprises the following steps: (1) mixing Prussian white with anhydrous oxalic acid, and carrying out dry ball milling under a vacuum condition to obtain mixed powder; (2) adding the mixed powder into a polytetrafluoroethylene-lined reaction kettle filled with ethanol, sealing the reaction kettle, and carrying out hydrothermal reaction in a muffle furnace; and (3) cleaning the powder obtained after the hydrothermal reaction in the step (2) by using a sodium carbonate solution, and after cleaning is completed, carrying out vacuum drying treatment on the powder to obtain the modified sodium ion battery positive electrode material after drying. The anhydrous oxalic acid is adopted as a modification additive, and a stable covalent bond network and a uniform surface coating layer are formed through a hydrothermal method, so that volume expansion and transition metal dissolution of the electrode material in the charging and discharging process can be effectively inhibited, and the cycle life of the battery is prolonged.

The invention discloses a lithium manganese iron phosphate positive electrode material and a preparation method thereof, and belongs to the technical field of lithium batteries, the preparation method of the lithium manganese iron phosphate positive electrode material comprises the following steps: dissolving a soluble iron source, a soluble manganese source and a complexing agent in 100 mL of deionized water, adjusting the pH value of the mixed solution to 2-4, and heating and stirring for 2-6 h to obtain xerogel; calcining the dry gel, taking out, cooling and grinding to obtain powder A; calcining the powder A in a nitrogen atmosphere, and grinding to obtain powder B; uniformly mixing the powder B, a lithium source, a phosphorus source, a carbon source and 70mL of deionized water, sanding, and spray-drying slurry after sanding to obtain powder C; and calcining the powder C in a nitrogen atmosphere, crushing, and sieving to obtain the lithium iron manganese phosphate positive electrode material. The lithium manganese iron phosphate positive electrode material prepared by the method has excellent conductivity and cycle performance.

The application provides a lithium iron phosphate composite material, a preparation method thereof, a positive electrode sheet and an energy storage device. The lithium iron phosphate composite material comprises a core, an amorphous carbon layer and a mesoporous carbon layer. The core is a lithium iron phosphate particle. The amorphous carbon layer is coated on the surface of the core. The mesoporous carbon layer is coated on the surface of the amorphous carbon layer away from the core. The lithium iron phosphate composite material provided by the application can be used as a positive electrode material, ensures high capacity and high compaction density of the positive electrode material, and solves the technical bottleneck that capacity and other key performances of the existing positive electrode material are difficult to balance.

This application belongs to the field of electrochemical technology, and specifically relates to a modified cathode material, its preparation method, and a cathode sheet, secondary battery, and electronic device containing the material. The modified cathode material includes: a ternary cathode material; and an oxide coating on the surface of the ternary cathode material, wherein the coating is an island-like coating, and the general chemical formula of the oxide is: Li. 2‑x A (1+x) / 3 B2O6F, 0.7≤x≤0.8; wherein A includes La and at least one of Mg, Ca, Sr, Ba, Al, Cd, Co, Cr, Cu, Fe, Mn, Ni, and Zn; wherein B includes Nb and at least one of Ti, Zr, V, Mo, W, Bi, Ta, and Hf; wherein the oxide content relative to the total mass of the modified cathode material is 0.6%~1.5%. The modified cathode material provided in this application has high capacity utilization, excellent rate performance, and good thermal safety properties. Applying the modified cathode material provided in this application to secondary batteries can effectively improve the energy density and heat resistance of secondary batteries.

The present application provides a method for preparing a high-capacity and high-rate negative electrode sheet, comprising: dissolving a silane coupling agent into an acidic solution to undergo a dicondensation reaction to obtain a mixed solution, wherein the silane coupling agent satisfies the chemical formula Y-R-Si(OR)3, Y represents an organic functional group, R represents an alkyl group, and the pH value of the acidic solution is 3-6, at least a hard carbon material is uniformly mixed into the mixed solution to obtain a slurry, the slurry is applied to a current collector, and a pole roll is obtained by drying, and the pole roll is heat-treated under an inert atmosphere, the heat treatment temperature is 500-900°C, and the heat treatment time is 1-2 hours to obtain a negative electrode sheet. The present application also provides a negative electrode sheet and a battery. The present application selects a silane coupling agent as a binder, and then performs a high-temperature treatment to cause the silane coupling agent to crack to form an inorganic material to solidify all particles in the negative electrode system, thereby improving the gram capacity, first charge efficiency, peel strength, swelling performance, charge rate and cycle performance of the negative electrode sheet, thereby helping to reduce the internal resistance of the battery.

The invention provides a negative electrode material as well as a preparation method and application thereof. The negative electrode material comprises an active substance, a binder and a conductive agent, the active substance comprises a silicon material, and the mass content of the silicon material in the negative electrode material is less than 20%; the mass content of the binder in the negative electrode material is 0.01 to 5 percent by weight; and the mass content of the conductive agent in the negative electrode material is 0-3wt%. According to the present invention, the negative electrode material contains the silicon material, the binder and the conductive agent, and the relationship between the content of the silicon material and the content of the binder and the conductive agent is designed, such that when the negative electrode material is used for the negative electrode plate, the high gram volume can be ensured, the expansion rate of the negative electrode plate can be reduced, and the excellent cycle performance can be provided.

The invention provides a positive electrode active material and a preparation method and application thereof, the positive electrode active material has a metal oxide with a chemical composition as shown in a formula 1, and in an X-ray diffraction pattern, the positive electrode active material has a (003) peak with a 2theta of 18.8-19.1 degrees, a (006) peak with a 2theta of 37.3-37.6 degrees, a (012) peak with a 2theta of 38.9-39.2 degrees, a (104) peak with a 2theta of 45.1-45.4 degrees and a superlattice structure characteristic peak with a 2theta of 18.2-18.5 degrees. The peak intensity of the characteristic peak of the superlattice structure is not higher than 3000, and the peak intensity ratio of the peak (003) to the peak (104) is greater than 1.2. The positive electrode active material has a special superlattice structure, so that the positive electrode active material is excellent in structural stability and gram volume.

The invention discloses a production method of monocrystal lithium manganese aluminate, which belongs to the technical field of preparation of lithium ion battery cathode materials, and comprises the following steps: taking manganous-manganic oxide, lithium carbonate and an aluminum-containing raw material, with the molar ratio of lithium carbonate to manganous-manganic oxide being Li: Mn being 0.50-0.55, the molar ratio of lithium carbonate to the aluminum-containing raw material being Li: Al being 1.00-1.05, and at the same time, carrying out a reaction for 2-3 hours to obtain the monocrystal lithium manganese aluminate. Adding a doping agent accounting for 0.02%-2.0% of the theoretical product mass, and mixing to obtain a uniform raw material; sintering the raw materials in an oxygen-enriched atmosphere at 800-950 DEG C for 8-16 hours to obtain a lithium manganese aluminate semi-finished product; crushing and crushing the lithium manganese aluminate semi-finished product to obtain a crushed product; through the synergistic effect of aluminum element doping and oxygen-enriched high-temperature sintering, the structural stability of the material is fundamentally improved.

The application discloses a method for producing lithium manganese oxide as a positive material of lithium battery by dry mixing, which comprises the following steps: step one, uniformly mixing LiMnO4, manganese dioxide, nano niobium pentoxide, nano aluminum oxide, LiOH powder and boron trioxide at room temperature, and grinding to obtain a mixture; step two, stirring and mixing the mixture in step one and polyvinyl alcohol to obtain a powder mixture; step three, preparing an acidic solution by heating H2O and adding a mixture of prepared anhydrous ethanol and concentrated hydrochloric acid, and stirring to obtain the acidic solution; step four, taking part of the acidic solution and adding to the powder mixture in step two to obtain a suspension; step five, adding the remaining acidic solution into the suspension in step four, and heating to react in a sealed environment; after the reaction is completed, cooling the reaction product to obtain a crystal coated with emulsified glue; step six, sintering and screening the crystal in step five; and step seven, removing iron from the screened material to obtain a product.

The application provides a positive electrode active material with a core-shell structure, a preparation method of the positive electrode active material, a positive electrode sheet containing the positive electrode active material, a secondary battery, a battery module, a battery pack and a power utilization device. The positive electrode active material comprises an inner core and a shell covering the inner core. The inner core comprises Li 1+x Mn 1‑y A y P 1‑z R z O4. The shell comprises a first coating layer covering the inner core, a second coating layer covering the first coating layer and a third coating layer covering the second coating layer. The first coating layer comprises a crystalline pyrophosphate Li a MP2O7 and / or M b (P2O7) c P2O7 is electrically neutral. The second coating layer comprises a crystalline phosphate XPO4. The third coating layer is carbon.

The invention discloses a preparation method of a capacity type sodium ion battery hard carbon negative electrode material, which comprises the following steps: S1, raw material pretreatment: crushing, sieving and drying a hard carbon raw material to obtain a precursor raw material; s2, raw material impregnation: impregnating the precursor raw material obtained in the step S1 in a vacuum impregnation tank to obtain an impregnated raw material; s3, low-temperature carbonization: carrying out low-temperature carbonization on the impregnated raw material in a protective atmosphere to obtain a low-temperature carbonized material; s4, crushing and refining: crushing and refining the low-temperature carbonized material obtained in the step S3 to obtain a refined low-temperature carbonized material; and S5, performing high-temperature carbonization: performing high-temperature carbonization on the refined low-temperature carbonized material obtained in the step S4 in a protective atmosphere to obtain a finished product of the hard carbon negative electrode material. The preparation method of the hard carbon negative electrode material of the capacity type sodium-ion battery has the characteristics of low cost, high capacity and good graphitization degree.

The present invention discloses a lithium slurry battery electrode and a screening method and application of its component ratio, belonging to the field of batteries. The lithium slurry battery electrode includes the following components in mass percentage: 8% lithium iron phosphate slurry, 1% Ketjen black, 2% TX‑100 and 89% electrolyte. The screening method includes: first, determining the specific indicators for component ratio screening - conductivity, viscosity and gram capacity according to the electrochemical performance requirements and working mode of the lithium slurry battery; then obtaining the effect of different components such as active materials, conductive agents, dispersants, electrolytes on conductivity, viscosity and gram capacity; finally, completing the screening of the optimal ratio of electrode components based on a comprehensive evaluation of the three types of indicators. The present invention provides a systematic and scientific component ratio design and optimization mechanism, improves the selection efficiency of the electrode component ratio, and provides a scientific basis for determining the content of lithium slurry battery electrode components.

The application relates to a preparation method and application of a negative electrode material, and comprises the following steps: (1) under a protective atmosphere, heating reaction is carried out on silicon carbide nanoparticles and a silane coupling agent containing amino groups in the presence of a solvent to obtain amino-modified silicon carbide nanoparticles; after bitumen is heated and melted, an acid anhydride monomer and an initiator are added to carry out a first stirring reaction to obtain an acid anhydride bitumen melt; (2) the amino-modified silicon carbide nanoparticles are added into the acid anhydride bitumen melt to carry out a second stirring reaction, and after reaction, cooling and crushing, amino-modified nano silicon carbide bitumen powder is obtained; (3) graphite is uniformly mixed with the amino-modified nano silicon carbide bitumen powder, and carbonization treatment is carried out to obtain the negative electrode material. The carbon-coated layer of the negative electrode material prepared by the above method is uniformly doped with silicon carbide nanoparticles, which can effectively reduce the full-charging expansion of a negative electrode sheet and improve the cycle performance of a battery.

The present application discloses a lithium supplement additive and its preparation method and application. The loose bulk density BD of the lithium supplement additive in the present application is 0.45 g / cm 3 ‑0.85g / cm 3 , tap density TD is 0.8g / cm 3 ‑1.5g / cm 3 The lithium supplement additive has high capacity and lithium supplement effect as well as good storage stability and processing stability, and can reduce the stress on the electrode active material particles during the electrode rolling and compression process, prevent the electrode active material particles from deformation and rupture, and ensure the electrochemical properties of the electrode such as gram capacity. The preparation method can ensure that the prepared lithium supplement additive has a specific particle density and stable electrochemical properties.

The present invention provides a negative electrode active material and a lithium ion battery using the negative electrode active material. The negative electrode active material comprises a graphite negative electrode material, the graphite negative electrode material comprises graphite and silicon grains, the silicon content in the negative electrode active material is not less than 2500ppm; in the voltage dQ / dV differential curve of a button battery made of the negative electrode active material, the peak intensity in the range of 0.4 to 0.5V is less than 600mAh·g ‑1 ·V ‑1 The voltage dQ / dV differential curve is obtained by charging and discharging the button cell at a rate of 0.05C at 20-30°C, and obtaining the voltage dQ / dV differential capacity curve from the charging curve of the fifth cycle. The negative electrode active material provided by the present invention has a significantly improved gram capacity compared to the general graphite negative electrode material. At the same time, the above-mentioned negative electrode active material has better structural stability and good cycle characteristics.

The application discloses a positive electrode active material, a secondary battery and a power utilization device. The positive electrode active material comprises a core material and a shell layer distributed on the surface of the core material, the shell layer comprises at least one of an aluminum-containing oxide and a boron-containing oxide, and a fluoride. The aluminum-containing oxide and / or the boron-containing oxide can react with residual lithium compounds on the surface of the core material, thereby preventing the residual lithium compounds from reacting with a binder in a positive electrode slurry during homogenization, and helping to maintain the stability of the structure of the positive electrode active material. The fluoride can enable the shell layer to resist the attack of hydrofluoric acid in a fluorine-containing electrolyte, not only can maintain the stability of the structure of the positive electrode active material, but also can improve the passing property of electrons and ions, and improve the performance of the secondary battery, such as the specific capacity, the high-temperature cycle capability and the like.

The invention relates to a negative pole piece, a secondary battery and a device. The negative electrode piece comprises a negative electrode current collector and a negative electrode active material layer arranged on the negative electrode current collector, the negative electrode active material layer comprises a carbon-based material and a silicon-based material, and the silicon-based material comprises a pre-lithium silica material; the negative pole piece meets the condition that 1-D * (0.1 * S + 1.225) / 2.33 + X is more than or equal to 6.6% and less than or equal to 20.4%; wherein based on the total mass of the silicon-based material, the mass percent content of Li element is X; the full-filling expansion rate of the silicon-based material is S; and the compaction density of the negative pole piece is D, and the unit is g / cm < 3 >. Thus, the secondary battery of the present application has higher energy density, excellent cycle performance and calendar life.