阅读说明：本技术 一种快充型高能量密度锂离子电池 (Quick-charging type high-energy-density lithium ion battery ) 是由 孙翠平 马华 于 2020-06-29 设计创作，主要内容包括：本发明提供了一种快充型高能量密度锂离子电池,包括正极极片、负极极片、隔膜和电解液,所述正极极片包括正极材料；正极材料包括正极导电剂,正极导电剂为Super P、KS-6、VGCF或CNTs中的两种或两种以上的混合物；所述负极极片包括负极材料；负极材料包括人造石墨,石墨颗粒为一次颗粒和二次颗粒的混合体；电解液为低阻抗型电解液。本发明所述的快充型高能量密度锂离子电池,具备3C快充能力,循环性能优良。(The invention provides a quick-charging type high-energy-density lithium ion battery, which comprises a positive pole piece, a negative pole piece, a diaphragm and electrolyte, wherein the positive pole piece comprises a positive pole material; the positive electrode material comprises a positive electrode conductive agent, and the positive electrode conductive agent is a mixture of two or more of Super P, KS-6, VGCF or CNTs; the negative pole piece comprises a negative pole material; the negative electrode material comprises artificial graphite, and the graphite particles are a mixture of primary particles and secondary particles; the electrolyte is a low impedance electrolyte. The quick-charging high-energy density lithium ion battery provided by the invention has 3C quick-charging capability and excellent cycle performance.)

1. The utility model provides a fill type high energy density lithium ion battery soon, includes positive pole piece, negative pole piece, diaphragm and electrolyte, its characterized in that: the positive pole piece comprises a positive pole material; the positive electrode material comprises a positive electrode conductive agent, and the positive electrode conductive agent is a mixture of two or more of Super P, KS-6, VGCF or CNTs;

the negative pole piece comprises a negative pole material; the negative electrode material comprises artificial graphite, and the graphite particles are a mixture of primary particles and secondary particles;

the electrolyte is a low impedance electrolyte.

2. The fast-charging high energy density lithium ion battery of claim 1, wherein: the positive electrode material also comprises a positive electrode active substance and a positive electrode binder; the mass percentage of each component in the anode material is as follows: 95-97% of positive electrode active substance, 2-3% of positive electrode conductive agent and 1-3% of positive electrode binder;

preferably, the positive electrode active material is lithium nickel cobalt manganese oxide.

3. The fast-charging high energy density lithium ion battery of claim 2, wherein: the positive electrode binder is selected from polyacrylic acid or PVDF or a mixture of SBR and CMC.

4. The fast-charging high energy density lithium ion battery according to any one of claims 1 to 3, characterized in that: the positive pole piece also comprises a positive current collector, the positive material is coated on the positive current collector, and the coating surface density of the positive material is 34-36mg/cm²The compacted density is 3.2-3.5g/cm³；

Preferably, the positive electrode current collector is an aluminum foil.

5. The fast-charging high energy density lithium ion battery of claim 1, wherein:

the negative electrode material also comprises a negative electrode conductive agent and a negative electrode binder, and the negative electrode material comprises the following components in percentage by mass: 94-96% of artificial graphite, 0.5-1.5% of negative electrode conductive agent and 2.5-5% of negative electrode binder.

6. The fast-charging high energy density lithium ion battery of claim 5, wherein: the negative electrode conductive agent is one or a mixture of more than two of Super P, KS-6, VGCF or CNTs;

preferably, the negative electrode binder is selected from polyacrylic acid or PVDF, or a mixture of SBR and CMC.

7. The fast-charging high energy density lithium ion battery of claim 1, 5 or 6, wherein: the negative pole piece also comprises a negative current collector, and a negative material is coated on the negative current collector;

the coating surface density of the negative electrode material on the negative electrode current collector is 21-23mg/cm²The compacted density is 1.4-1.6g/cm³；

Preferably, the negative electrode current collector is a copper foil.

8. The fast-charging high energy density lithium ion battery of claim 7, wherein: the particle size of the primary particles is 8-12 μm, the average particle size D50 of the secondary particles is 12-16 μm, and the mass percentage of the secondary particles in the graphite particles is 20-50%;

preferably, the primary particles and the secondary particles are subjected to surface coating modification, and the coating material is one of soft carbon or hard carbon; the coating material of the primary particles accounts for 0.5-5% of the mass of the primary particles, and the coating material of the secondary particles accounts for 0.5-5% of the mass of the secondary particles.

9. The fast-charging high energy density lithium ion battery of claim 1, wherein: the battery electrolyte is low-impedance electrolyte, and the electrolyte comprises electrolyte, solvent and film-forming additive; the electrolyte is lithium hexafluorophosphate; the mixed solvent is a mixture of ethylene carbonate, diethyl carbonate and ethyl methyl carbonate; the film forming additive is three or four of vinylene carbonate, propylene sulfite, ethylene sulfate and LiBOB;

preferably, the concentration of the electrolyte is 1.0-1.3 mol/L; the volume ratio of the ethylene carbonate, the diethyl carbonate and the ethyl methyl carbonate in the mixed solvent is (23-26): (15-20): (40-45); the ethylene carbonate, the propylene sulfite, the ethylene sulfate and the LiBOB in the film forming additive respectively account for 0.2-1%, 0.5-1.5%, 1-2.5% and 0.1-0.5% of the total mass of the electrolyte.

10. The fast-charging high energy density lithium ion battery of claim 1, wherein: the upper limit voltage range of the battery cell is 4.3-4.4V, and the energy density of the battery cell is 230-250 wh/kg;

preferably, the diaphragm is a ceramic-coated diaphragm;

more preferably, the ceramic separator has a thickness of 12 to 18 μm and a porosity of 25 to 50%.

Technical Field

The invention belongs to the field of lithium ion power batteries, and particularly relates to a quick-charging type high-energy-density lithium ion battery.

Background

Since the birth of lithium ion batteries, lithium ion batteries have gained important applications in a plurality of fields. From the application field of the current lithium ion battery, the lithium ion battery not only can be widely applied to electronic products such as mobile phones and chargers, but also can make a certain breakthrough in the fields such as vehicle-mounted power supplies. From the demand of the current market for lithium ion batteries, the fast charging lithium ion batteries become an important development direction of the lithium ion batteries. Particularly, for pure electric buses with fixed running distances, operation-edition taxies and the like, the problem of insufficient operation mileage can be solved by improving the quick battery charging capacity and reducing the battery loading capacity.

From the demand of the current market for lithium ion batteries, the fast charging lithium ion batteries become an important development direction of the lithium ion batteries. In order to achieve more driving mileage, the energy density of the vehicle-mounted lithium ion battery is also continuously increased, because the lithium metal is separated out from the negative electrode of the rapid charging, the capacity and the cycle life of the battery are reduced, and the rapid charging technology under high energy density has great vacancy.

Disclosure of Invention

In view of this, the present invention is directed to a fast-charging high-energy density lithium ion battery, which overcomes the defects of the prior art and has a 3C fast-charging capability and excellent cycle performance.

In order to achieve the purpose, the technical scheme of the invention is realized as follows:

a quick-charging type high-energy-density lithium ion battery comprises a positive pole piece, a negative pole piece, a diaphragm and electrolyte, wherein the positive pole piece comprises a positive pole material; the positive electrode material comprises a positive electrode conductive agent, wherein the positive electrode conductive agent is a mixture of two or more than two of Super P (conductive carbon black), KS-6 (graphite powder), VGCF (vapor grown carbon fiber) or CNTs (carbon nano tubes);

the negative pole piece comprises a negative pole material; the negative electrode material comprises artificial graphite, and the graphite particles are a mixture of primary particles and secondary particles;

the electrolyte is a low impedance electrolyte.

Preferably, the positive electrode material further comprises a positive electrode active material and a positive electrode binder; the mass percentage of each component in the anode material is as follows: 95-97% of positive electrode active substance, 2-3% of positive electrode conductive agent and 1-3% of positive electrode binder.

Preferably, the positive electrode active material is lithium nickel cobalt manganese oxide.

Preferably, the positive electrode binder is selected from polyacrylic acid or PVDF (polyvinylidene fluoride), or a mixture of SBR (styrene butadiene rubber) and CMC (sodium carboxymethylcellulose).

Preferably, the positive pole piece further comprises a positive pole current collector, the positive pole material is coated on the positive pole current collector, and the coating surface density of the positive pole material is 34-36mg/cm²The compacted density is 3.2-3.5g/cm³。

Preferably, the positive electrode current collector is an aluminum foil.

Preferably, the negative electrode material further comprises a negative electrode conductive agent and a negative electrode binder, and the negative electrode material comprises the following components in percentage by mass: 94-96% of artificial graphite, 0.5-1.5% of negative electrode conductive agent and 2.5-5% of negative electrode binder.

Preferably, the negative electrode conductive agent is one or a mixture of more than two of Super P (conductive carbon black), KS-6 (graphite powder), VGCF (vapor grown carbon fiber) or CNTs (carbon nano tubes).

Preferably, the negative electrode binder is selected from polyacrylic acid or PVDF (polyvinylidene fluoride), or a mixture of SBR (styrene butadiene rubber) and CMC (sodium carboxymethylcellulose).

Preferably, the negative pole piece further comprises a negative current collector, and the negative material is coated on the negative current collector; the coating surface density of the negative electrode material on the negative electrode current collector is 21-23mg/cm²The compacted density is 1.4-1.6g/cm³。

Preferably, the negative electrode current collector is a copper foil.

Preferably, the primary particles have a particle size of 8 to 12 μm, the secondary particles have an average particle size D50 of 12 to 16 μm, and the secondary particles are 20 to 50% by mass in the graphite particles.

Preferably, the primary particles and the secondary particles are subjected to surface coating modification, and the coating material is one of soft carbon or hard carbon; the coating material of the primary particles accounts for 0.5-5% of the mass of the primary particles, and the coating material of the secondary particles accounts for 0.5-5% of the mass of the secondary particles.

Preferably, the battery electrolyte is a low-impedance electrolyte, and the electrolyte comprises an electrolyte, a solvent and a film-forming additive; the electrolyte is lithium hexafluorophosphate; the mixed solvent is a mixture of ethylene carbonate, diethyl carbonate and ethyl methyl carbonate; the film forming additive is three or four of vinylene carbonate, propylene sulfite, ethylene sulfate and LiBOB.

Preferably, the concentration of the electrolyte is 1.0-1.3 mol/L; the volume ratio of the ethylene carbonate, the diethyl carbonate and the ethyl methyl carbonate in the mixed solvent is (23-26): (15-20): (40-45); in the film forming additive, vinylene carbonate, propylene sulfite, ethylene sulfate and LiBOB (lithium bis (oxalato) borate) respectively account for 0.2-1%, 0.5-1.5%, 1-2.5% and 0.1-0.5% of the total mass of the electrolyte.

Preferably, the upper limit voltage of the battery cell is in the range of 4.3-4.4V, and the energy density of the battery cell is 230-250 wh/kg.

Preferably, the separator is a ceramic coated separator.

More preferably, the ceramic separator has a thickness of 12 to 18 μm and a porosity of 25 to 50%.

Compared with the prior art, the quick-charging type high-energy-density lithium ion battery has the following advantages: by optimizing the anode and cathode systems and the formula of the electrolyte, the lithium ion battery has 3C quick charging capability and excellent cycle performance. More specifically:

(1) the positive electrode conductive agent is a mixture of two or more of Super P, KS-6, VGCF or CNTs, continuous contraction and expansion exist among the particles in the pole piece, the anode particles crack in the long-time circulation process and are easy to form an island, only a single granular or flaky conductive agent is used to easily generate the island effect, the active material is gradually isolated, the battery capacity is reduced, the cycle decay is accelerated, and the granular or flaky conductive agent composite linear conductive agent is filled in the pores of the active material, a continuous conductive network is formed in the electrode active material, which can improve the long-range electron transmission capability, the linear conductive agent is uniformly coated on the surface of the active material, even if the active material cracks in the later period of circulation, the formation of an island without electron transmission can be reduced to a great extent, and the circulation performance is improved.

(2) The graphite particles in the negative electrode material are a mixture of primary particles and secondary particles, the secondary particles can be selected to reduce expansion in the circulation process and improve the liquid absorption performance and the quick charge performance, and the primary particles can be selected to improve the circulation performance of the battery core and reduce the granularity of the primary particles and improve the quick charge performance; the primary particles and the secondary particles are coated products, the coating material is one of soft carbon or hard carbon, the electrochemical reaction impedance of the material can be greatly reduced through the coating of the soft carbon or the hard carbon, the polarization is reduced, and the quick charging performance of the material is improved.

(3) Through the optimal treatment of the electrolyte formula, the internal resistance of the battery can be greatly reduced, and the rapid charge-discharge and cycle performance of the battery can be improved. Specifically, the electrolyte is added with low-viscosity organic solvents of ethyl methyl carbonate EMC and diethyl carbonate DEC in a basic solvent of ethylene carbonate EC, so that free ions can move in the electrolyte more quickly, and the quick charging performance of the battery cell is improved. The low-impedance film forming additives VC, PS and DTD are added, the composition of an SEI film is improved, the stability of the SEI film is improved, the quick charging performance is improved, and the circulation can be improved by adding the negative electrode film forming additive LiBOB. The battery disclosed by the invention can greatly reduce the internal resistance of the battery and improve the rapid charge-discharge and cycle performance of the battery by optimally treating the electrolyte formula.

According to the quick-charging type high-energy-density lithium ion battery, under the condition of 3C quick charging, the total charging time is less than 35min, the 3C constant-current charging ratio is more than or equal to 83%, and the 3C constant-current charging time is less than 18 min.

Drawings

Fig. 1 is 3C/1C cycle data of a fast-charging high-energy density lithium ion battery cell according to embodiment 1 of the present invention.

Detailed Description

Unless defined otherwise, technical terms used in the following examples have the same meanings as commonly understood by one of ordinary skill in the art to which the present invention belongs. The test reagents used in the following examples, unless otherwise specified, are all conventional biochemical reagents; the experimental methods are conventional methods unless otherwise specified.

A quick-charging type high-energy-density lithium ion battery comprises a positive pole piece, a negative pole piece, a diaphragm and electrolyte. The positive plate comprises a positive current collector and a positive material coated on the positive current collector, and the negative plate comprises a negative current collector and a negative material coated on the negative current collector.

The positive active substance of the battery is nickel cobalt lithium manganate, and the negative material is artificial graphite.

The cathode material comprises the following substances in percentage by mass: 95% -97% of nickel cobalt lithium manganate, 2% -3% of positive conductive agent and 1% -3% of positive binder, wherein the positive conductive agent is a mixture of more than two of Super P (conductive carbon black), KS-6 (graphite powder), VGCF (VGCF) or CNTs (carbon nano tubes), during charging and discharging, continuous contraction and expansion exist among particles in a pole piece, positive particles crack in a long-time circulation process and are easy to form 'isolated islands', only a single granular or flaky conductive agent is easy to generate 'isolated island' effect, active materials are gradually isolated, the battery capacity is reduced, so that the circulation attenuation is accelerated, a granular or flaky conductive agent composite linear conductive agent is filled in pores of active materials to form a continuous conductive network in the electrode active materials, the long-range electron transmission capability can be improved, and the linear conductive agent is uniformly wrapped on the surface of the active materials, even if the active material cracks in the later period of circulation, the formation of an island without electron transmission can be reduced to a great extent, and the circulation performance is improved. The positive adhesive is selected from polyacrylic acid, PVDF or a mixture of SBR and CMC;

the negative electrode material comprises the following substances in percentage by mass: 94 to 96 percent of artificial graphite, 0.5 to 1.5 percent of negative electrode conductive agent and 2.5 to 5 percent of negative electrode binder. The graphite particles are a mixture of primary particles and secondary particles, the secondary particles can be selected to reduce expansion in the circulation process and improve the liquid absorption performance and the quick charge performance, and the primary particles can be selected to improve the circulation performance of the battery cell and reduce the granularity of the primary particles and improve the quick charge performance; the average particle size D50 of the primary particles is 8-12 mu m, the average particle size D50 of the secondary particles is 12-16 mu m, and the mass percentage of the secondary particles in the artificial graphite negative electrode is 20-50%. The primary particles and the secondary particles are coated products. The coating material is one of soft carbon or hard carbon, and the electrochemical reaction impedance of the material can be greatly reduced, the polarization is reduced, and the quick charging performance of the material is improved by coating the soft carbon or the hard carbon; the content of the coating material is 0.5-5% (namely the coating material of the primary particles accounts for 0.5-5% of the mass of the primary particles, and the coating material of the secondary particles accounts for 0.5-5% of the mass of the secondary particles). The negative electrode conductive agent is one or a mixture of more than two of Super P, KS-6, VGCF or CNTs, and the negative electrode binder is selected from polyacrylic acid, PVDF or a mixture of SBR and CMC.

The battery diaphragm is a ceramic coating diaphragm; the thickness of the ceramic diaphragm is 12-18 mu m, and the porosity is 25% -50%.

The battery electrolyte is low-impedance electrolyte and comprises electrolyte, solvent and film-forming additive. The electrolyte is lithium hexafluorophosphate, and the concentration of the electrolyte is 1.0-1.3 mol/L.

The solvent comprises the following substances in volume fraction: ethylene carbonate EC 23-26%, diethyl carbonate DEC 15-20%, and ethyl methyl carbonate EMC 40-45%.

The film forming additive comprises the following substances in parts by volume: the electrolyte is prepared by adding three or four of low-viscosity organic solvents of ethyl methyl carbonate EMC and diethyl carbonate DEC into a basic solvent of ethylene carbonate EC, so that free ions can move in the electrolyte more quickly, and the quick charging performance of a battery cell is improved. The low-impedance film forming additives VC, PS and DTD are added, the composition of an SEI film is improved, the stability of the SEI film is improved, the quick charging performance is improved, and the circulation can be improved by adding the negative electrode film forming additive LiBOB. The battery disclosed by the invention can greatly reduce the internal resistance of the battery and improve the rapid charge-discharge and cycle performance of the battery by optimally treating the electrolyte formula.

The coating of the anode material on the anode current collector of the quick-charging high-energy density lithium ion batteryThe cloth cover density is 34-36mg/cm²The compaction density is 3.2-3.5g/cm³(ii) a The coating surface density of the negative material on the negative current collector on the negative plate is 21-23mg/cm²The compaction density is 1.4-1.6g/cm³。

The upper limit voltage range of the electric core of the quick-charging type high-energy density lithium ion battery is 4.3-4.4V, and the energy density is 230-250 wh/kg.

The present invention will be described in detail with reference to the following examples and accompanying drawings.