CN116565143A - Positive electrode lithium supplementing pole piece, battery core and lithium ion battery - Google Patents

Abstract

The invention discloses a positive electrode lithium supplementing pole piece, a battery core and a lithium ion battery. The positive electrode lithium supplementing pole piece comprises: the positive electrode material, the first positive electrode lithium supplementing agent and the second positive electrode lithium supplementing agent are mixed in the positive electrode lithium supplementing pole piece; the first charge gram capacity of the first positive electrode lithium supplementing agent is larger than the first charge gram capacity of the second positive electrode lithium supplementing agent, and the first charge gram capacity of the second positive electrode lithium supplementing agent is larger than the first charge gram capacity of the positive electrode material; the first discharge gram capacity of the positive electrode material is larger than the first discharge gram capacity of the first positive electrode lithium supplementing agent, and the first discharge gram capacity of the positive electrode material is larger than the first discharge gram capacity of the second positive electrode lithium supplementing agent; the first charge-discharge efficiency of the positive electrode material is greater than the first charge-discharge efficiency of the second positive electrode lithium supplement agent, and the first charge-discharge efficiency of the second positive electrode lithium supplement agent is greater than the first charge-discharge efficiency of the first positive electrode lithium supplement agent. The technical scheme of the embodiment of the invention can improve the energy density and the cycle life of the lithium ion battery.

Description

A kind of positive electrode replenishing lithium pole piece, battery cell and lithium ion battery

technical field

The embodiments of the present invention relate to the technical field of lithium-ion batteries, and in particular to a positive lithium supplementary pole piece, a battery cell and a lithium-ion battery.

Background technique

With the rapid development of electric vehicles, the lithium-ion battery industry has also maintained a rapid growth trend, and industry innovation has continued to accelerate.

However, in the manufacturing process of lithium-ion batteries, the Coulombic efficiency of the first charge-discharge cycle of lithium-ion batteries is generally low, which reduces the capacity and energy density of lithium-ion batteries. In response to this problem, lithium-ion batteries can be pre-lithiated, that is, lithium supplementation, to increase the capacity and energy density of lithium-ion batteries. Lithium supplementation methods include positive electrode lithium supplementation and negative electrode lithium supplementation. However, due to the cumbersome process of negative electrode lithium supplementation, it is difficult to apply in actual production. Therefore, the prior art mostly adopts the method of positive electrode lithium supplementation.

In the existing positive electrode lithium supplementation method, by mixing the pre-lithium material and the redox shuttle agent material into the positive electrode material of the lithium-ion battery as additives, the delithiation voltage of the pre-lithium material can be effectively reduced, and the redox shuttle reaction generated The thermal energy makes the lithium supplementing effect of the pre-lithium material more fully play, effectively compensates for the loss of lithium ions formed by the solid-electrolyte interface film (SEI film) of the positive electrode material during the first charge and discharge, and achieves the effect of increasing the energy density. However, after the pre-lithium material is completely delithiated during the first charge-discharge cycle, it cannot continue to replenish lithium in the later cycle charge-discharge process, resulting in a weak ability to improve the cycle life of lithium-ion batteries.

Contents of the invention

The invention provides a positive electrode supplementary lithium pole piece, a battery cell and a lithium-ion battery, so as to realize the improvement of the energy density when the lithium-ion battery is charged and discharged for the first time, and to continuously supplement lithium during the later charge-discharge cycle, thereby improving the lithium-ion battery. cycle life.

According to one aspect of the present invention, there is provided a positive electrode lithium replenishing pole piece, comprising: a positive electrode material, a first positive electrode lithium replenishing agent and a second positive electrode lithium replenishing agent;

The positive electrode material, the first positive electrode lithium supplement agent and the second positive electrode lithium supplement agent are mixed in the positive electrode lithium supplement pole piece; wherein, the first charge gram capacity of the first positive electrode lithium supplement agent is greater than the The first charge gram capacity of the second positive electrode lithium supplement agent, the first charge gram capacity of the second positive electrode lithium supplement agent is greater than the first charge gram capacity of the positive electrode material; the first discharge gram capacity of the positive electrode material is greater than the first charge gram capacity The first discharge gram capacity of a positive electrode lithium supplement, and the first discharge gram capacity of the positive electrode material is greater than the first discharge gram capacity of the second positive electrode lithium supplement;

The first charge-discharge efficiency of the positive electrode material is greater than the first charge-discharge efficiency of the second positive electrode lithium supplement agent, and the first charge-discharge efficiency of the second positive electrode lithium supplement agent is greater than the first charge-discharge efficiency of the first positive electrode lithium supplement agent efficiency.

Optionally, the positive electrode material occupies a first mass content percentage, the first positive electrode lithium supplementing agent occupies a second mass content percentage, and the second positive electrode lithium supplementing agent occupies a third mass content percentage;

The sum of the first mass content percentage, the second mass content percentage and the third mass content percentage is 1.

Optionally, the first charge and discharge efficiency of the positive electrode is less than or equal to the first charge and discharge efficiency of the negative electrode;

Wherein, the first charge and discharge efficiency of the positive electrode is the ratio of the actual first discharge gram capacity of the positive electrode to the actual first charge gram capacity of the positive electrode; the actual first discharge gram capacity of the positive electrode is the actual first discharge gram capacity of the positive electrode material, the first The sum of the actual first discharge gram capacity of the positive electrode lithium supplement agent and the actual first discharge gram capacity of the second positive electrode lithium supplement agent; the actual first charge gram capacity of the positive electrode is the actual first charge gram capacity of the positive electrode material, the The sum of the actual initial charge gram capacity of the first positive electrode lithium supplement and the actual initial charge gram capacity of the second positive electrode lithium supplement.

Optionally, the actual first discharge gram capacity of the positive electrode material is the product of the first discharge gram capacity of the positive electrode material and the first mass content percentage; the actual first discharge gram capacity of the first positive electrode lithium supplement is The product of the first discharge gram capacity of the first positive electrode lithium supplement and the second mass content percentage; the actual first discharge gram capacity of the second positive lithium supplement is the first discharge of the second positive lithium supplement The product of the gram capacity and the third mass content percentage;

The actual first charge gram capacity of the positive electrode material is the product of the first charge gram capacity of the positive electrode material and the first mass content percentage; the actual first charge gram capacity of the first positive electrode lithium supplement is the first The product of the first charge gram capacity of the positive electrode lithium supplement agent and the second mass content percentage; the actual first charge gram capacity of the second positive electrode lithium supplement agent is the first charge gram capacity of the second positive electrode lithium supplement agent and the product The product of the third mass content percentage.

Optionally, the charging gram capacity of the positive electrode material ranges from 100 to 300mAh/g, and the first charge and discharge efficiency is greater than 80%;

The charge gram capacity range of the first positive electrode lithium supplement is 400-1200mAh/g, and the initial charge-discharge efficiency range is 0-10%;

The charging gram capacity of the second positive electrode lithium supplementing agent ranges from 200 to 500 mAh/g, and the initial charging and discharging efficiency ranges from 20% to 50%.

Optionally, the first positive electrode supplementary lithium agent is any one of lithium ferrite and lithium oxide;

The second positive electrode lithium replenishing agent is any one of lithium-rich lithium nickelate and lithium-rich lithium cobaltate.

Optionally, the positive electrode material is any one of lithium manganese iron phosphate and lithium iron phosphate.

Optionally, the positive lithium-supplementing pole piece also includes: a binder and a conductive agent;

The binder is used to mix the positive electrode material, the first positive electrode lithium supplement agent and the second positive electrode lithium supplement agent evenly, and the conductive agent is used to enhance the conductivity of the positive electrode lithium supplement pole piece .

According to another aspect of the present invention, a battery cell is provided, including: a separator, an electrolyte, a negative electrode sheet, a negative electrode current collector, a positive electrode current collector, and the positive lithium supplementary electrode sheet as described in the first aspect;

The positive lithium-supplementing pole piece is arranged on the surface of the positive electrode current collector, the negative electrode piece is arranged on the surface of the negative electrode current collector, and the diaphragm is arranged between the positive electrode current collector and the negative electrode piece.

According to another aspect of the present invention, there is also provided a lithium-ion battery, comprising: a casing and the battery cell as described in the second aspect.

In the embodiment of the present invention, a material with a high initial charge gram capacity and a low initial charge and discharge efficiency is selected as the first positive electrode lithium replenishing agent, and the first charge gram capacity is selected to be between the first charge gram capacity of the positive electrode material and the first positive electrode lithium replenishing agent. Charging gram capacity, and the first charge and discharge efficiency is between the first charge and discharge efficiency of the positive electrode material and the first charge and discharge efficiency of the first positive electrode lithium replenishing agent as the second positive electrode lithium replenishing agent, and the first positive electrode lithium replenishing agent 1. The second positive electrode lithium replenishing agent is mixed with the positive electrode material to make the positive electrode lithium replenishing pole piece, so that the lithium ion battery with the positive electrode lithium supplementing pole piece can realize the improvement of energy density in the first charge and discharge process, and at the same time, it can be charged later. Continuous lithium replenishment is realized during the discharge cycle, which improves the cycle life of the lithium-ion battery.

It should be understood that the content described in this section is not intended to identify key or important features of the embodiments of the present invention, nor is it intended to limit the scope of the present invention. Other features of the present invention will be easily understood from the following description.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings that need to be used in the description of the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention. For those skilled in the art, other drawings can also be obtained based on these drawings without creative effort.

Fig. 1 is a schematic cross-sectional structure diagram of an electric core provided according to an embodiment of the present invention.

Detailed ways

In order to enable those skilled in the art to better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only It is an embodiment of a part of the present invention, but not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts shall fall within the protection scope of the present invention.

It should be noted that the terms "first" and "second" in the description and claims of the present invention and the above drawings are used to distinguish similar objects, but not necessarily used to describe a specific sequence or sequence. It is to be understood that the data so used are interchangeable under appropriate circumstances such that the embodiments of the invention described herein can be practiced in sequences other than those illustrated or described herein. Furthermore, the terms "comprising" and "having", as well as any variations thereof, are intended to cover a non-exclusive inclusion, for example, a process, method, system, product or device comprising a sequence of steps or elements is not necessarily limited to the expressly listed instead, may include other steps or elements not explicitly listed or inherent to the process, method, product or apparatus.

An embodiment of the present invention provides a positive lithium-supplementing pole piece. The positive electrode lithium replenishing pole piece includes: positive electrode material, a first positive electrode lithium replenishing agent and a second positive electrode lithium replenishing agent.

The positive electrode material, the first positive lithium supplement and the second positive lithium supplement are mixed in the positive lithium supplement sheet; wherein, the first charge gram capacity of the first positive lithium supplement is greater than the first charge gram capacity of the second positive lithium supplement , the first charge gram capacity of the second positive electrode lithium supplement is greater than the first charge gram capacity of the positive electrode material; the first discharge gram capacity of the positive electrode material is greater than the first discharge gram capacity of the first positive electrode lithium supplement, and the first discharge gram capacity of the positive electrode material is greater than The first discharge gram capacity of the second positive electrode lithium supplement;

The first charge and discharge efficiency of the positive electrode material is greater than the first charge and discharge efficiency of the second positive electrode lithium supplement, and the first charge and discharge efficiency of the second positive lithium supplement is greater than the first charge and discharge efficiency of the first positive lithium supplement.

Among them, the gram capacity is the ratio of the electric capacity released by the active material inside the battery to the mass of the active material, which can be understood as the amount of electricity contained in a unit mass of the active material. The battery includes a variety of active materials, for example, various materials contained in the positive electrode sheet of the battery and/or various materials contained in the negative electrode sheet of the battery, and each material has a corresponding gram capacity. Charging gram capacity is the ratio of the electric capacity that the active material inside the lithium-ion battery can release during the charging process to the mass of the active material, and the discharge gram capacity is the electric capacity that the active material inside the lithium-ion battery can release during the discharge process ratio to the mass of the active substance. The first charge gram capacity is the ratio of the capacity released by the internal active material to the mass of the active material during the first charge of the lithium-ion battery, and the first discharge gram capacity is the internal active material during the first discharge of the lithium-ion battery. The ratio of the capacity that can be released to the mass of the active material. And the first charge gram capacity and the first discharge gram capacity of the active material inside the battery are only related to the material type of the active material, that is to say, when the material type of the active material is determined, the first charge gram capacity and the first discharge gram capacity are definite values , and remain unchanged, that is, the first charge gram capacity and the first discharge gram capacity are properties of the active material itself.

During the charge-discharge cycle of the lithium-ion battery, the first positive electrode lithium replenishing agent and the second positive electrode lithium replenishing agent can supplement lithium ions. According to the relationship between the first charge gram capacity and the first discharge gram capacity of different materials, appropriate materials are selected as the first positive electrode lithium supplement agent and the second positive electrode lithium supplement agent. By mixing the first positive electrode lithium supplement agent and the second positive electrode lithium supplement agent with the positive electrode material of the lithium-ion battery, the positive electrode lithium supplement sheet is made, which can improve the performance of the lithium-ion battery when the lithium-ion battery is charging and discharging. The role of energy density and cycle life.

Exemplarily, for the positive electrode material, the first positive electrode lithium supplement agent and the second positive electrode lithium supplement agent, a material with a high initial charging gram capacity and a low initial charge and discharge efficiency is selected as the first positive electrode lithium supplement agent, so that it can be used in lithium-ion batteries Sufficient lithium ions are provided during the first charge and discharge process to achieve an increase in energy density. Since the first positive electrode lithium supplementation agent removes all lithium ions during the first charge and discharge process, in the later charge and discharge cycle process, if only relying on the first positive electrode lithium supplementation agent, it will not be able to continuously provide lithium ions. Therefore, the lithium ion cannot be increased. Cycle life of ion batteries.

The first charging gram capacity is selected between the first charging gram capacity of the positive electrode material and the first positive electrode lithium supplementing agent, and the first charging and discharging efficiency is between the first charging and discharging efficiency of the positive electrode material and the first positive electrode lithium supplementing agent. The material is used as the second positive lithium supplementary agent, and the product obtained after the delithiation of the second positive lithium supplementary agent in the first charge and discharge process still has certain reversibility, and lithium ions can be inserted into the positive lithium supplementary pole piece again, so that Continuous delithiation and lithium intercalation are achieved during the charge-discharge cycle, which improves the cycle life of lithium-ion batteries. However, since the second positive electrode lithium supplement gradually removes lithium ions during the charge-discharge cycle, if only relying on the second positive lithium supplement, a large amount of lithium ions cannot be released during the first charge-discharge process. The effect of the energy density of the battery.

To sum up, in this embodiment, the first positive electrode lithium supplement agent and the second positive electrode lithium supplement agent with the above two different properties are mixed with the positive electrode material, so that the lithium ion battery can achieve the effect of increasing the energy density and improving the cycle life.

In this embodiment, a material with a high initial charging gram capacity and a low initial charge and discharge efficiency is selected as the first positive electrode lithium replenishing agent, and the initial charging gram capacity is selected to be between the first charging gram capacity of the positive electrode material and the first charge of the first positive electrode lithium replenishing agent. gram capacity, and the first charge-discharge efficiency is between the first charge-discharge efficiency of the positive electrode material and the first charge-discharge efficiency of the first positive electrode lithium supplement material as the second positive electrode lithium supplement agent, and the first positive electrode lithium supplement agent, The second positive electrode lithium replenishing agent is mixed with the positive electrode material to make the positive electrode lithium replenishing pole piece, so that the lithium ion battery with the positive electrode lithium supplementing pole piece can realize the improvement of energy density in the first charge and discharge process, and at the same time, it can be charged and discharged in the later stage Continuous lithium supplementation is realized during the cycle, which improves the cycle life of the lithium-ion battery.

Optionally, on the basis of the above embodiments, the positive electrode material occupies the first mass content percentage, the first positive electrode lithium supplementing agent occupies the second mass content percentage, and the second positive electrode lithium supplementing agent occupies the third mass content percentage.

The sum of the first mass content percentage, the second mass content percentage and the third mass content percentage is 1.

Specifically, the first positive electrode lithium supplementing agent is mixed with the second mass content percentage, the second positive electrode lithium supplementing agent is mixed with the third mass content percentage, and the positive electrode material is mixed with the first mass content percentage, so as to make the positive electrode lithium supplementary electrode piece. In order to fully replenish lithium in the first charge and discharge process of lithium-ion batteries, and to sustain lithium replenishment in the later charge and discharge cycles, the mixed mass content percentages of the first positive lithium supplement, the second positive lithium supplement and the positive material A certain quantitative relationship needs to be satisfied. Because in the positive electrode supplementary lithium pole piece, the positive electrode material, the first positive pole lithium supplementary agent and the second positive pole lithium supplementary agent are the main lithium supplementary materials, which provide sufficient lithium ions, while other auxiliary materials in the positive pole lithium supplementary pole piece Lithium supplementation has little effect. Therefore, the content of other auxiliary materials does not affect the mass content percentage distribution of each lithium supplementary material. Set appropriate mass content percentages for the positive electrode material, the first positive electrode lithium supplementary agent, and the second positive electrode lithium supplementary agent. , and make the sum of the first mass content percentage, the second mass content percentage and the third mass content percentage be 1.

Optionally, on the basis of the foregoing embodiments, the first charge and discharge efficiency of the positive electrode is less than or equal to the first charge and discharge efficiency of the negative electrode.

Among them, the first charge and discharge efficiency of the positive electrode is the ratio of the actual first discharge gram capacity of the positive electrode to the actual first charge gram capacity of the positive electrode; The sum of the gram capacity and the actual first discharge gram capacity of the second positive electrode lithium supplement; The sum of the actual first charge gram capacity of the lithium supplement.

Specifically, the first charge and discharge efficiency of the positive electrode is the capacity loss of the positive active material, which mainly comes from the structural change of the active material in the positive electrode after the first discharge, which reduces the position where lithium can be intercalated, making it impossible for lithium ions to return to the original lithium intercalation. position, resulting in capacity loss. Exemplarily, the first-time charge-discharge efficiency of the positive electrode can be obtained from the quotient of the actual first-time discharge gram capacity of the positive electrode and the actual first-time charge gram capacity of the positive electrode.

Among them, the actual first-time discharge gram capacity of the positive electrode is the sum of the actual first-time discharge gram capacity of each active material contained in the positive electrode lithium-supplementing electrode sheet, that is, the actual first-time discharge gram capacity of the positive electrode can be obtained by combining the actual first-time discharge gram capacity of the positive electrode material, the second The actual initial discharge gram capacity of the first positive electrode lithium supplement and the actual first discharge gram capacity of the second positive electrode lithium supplement are calculated. Exemplarily, the actual first discharge gram capacity of the positive electrode material is the product of the first discharge gram capacity of the positive electrode material and the first mass content percentage; the actual first discharge gram capacity of the first positive electrode lithium supplement is the product of the first positive electrode lithium supplement The product of the discharge gram capacity and the second mass content percentage; the actual first discharge gram capacity of the second positive electrode lithium supplement is the product of the first discharge gram capacity of the second positive electrode lithium supplement and the third mass content percentage.

The actual initial charge gram capacity of the positive electrode is the sum of the actual initial charge gram capacity of each active material contained in the positive electrode lithium-supplementing pole piece, that is, the actual initial charge gram capacity of the positive electrode can be obtained by combining the actual initial charge gram capacity of the positive electrode material, the first positive electrode The actual initial charge gram capacity of the lithium supplement agent and the actual initial charge gram capacity of the second positive electrode lithium supplement agent are calculated. Wherein, the actual first charge gram capacity of the positive electrode material is the product of the first charge gram capacity of the positive electrode material and the first mass content percentage; the actual first charge gram capacity of the first positive electrode lithium supplement is the first charge gram capacity of the first positive electrode lithium supplement The product of the capacity, the first charge and discharge efficiency and the second mass content percentage; the actual first charge gram capacity of the second positive electrode lithium supplement is the first charge gram capacity, the first charge and discharge efficiency and the third mass content percentage of the second positive electrode lithium supplement product of .

The first charge and discharge efficiency of the negative electrode is the capacity loss of the negative electrode active material. The main reason for the capacity loss is that the SEI film is formed on the surface of the negative electrode sheet during the charging process, which irreversibly consumes lithium ions. The first charge-discharge efficiency of the lithium-ion battery is the same as the lower one of the first charge-discharge efficiency of the positive electrode and the first charge-discharge efficiency of the negative electrode. The first charge-discharge efficiency of the lithium-ion battery is equal to the first charge-discharge efficiency of the positive electrode; if the first charge-discharge efficiency of the negative electrode is lower than the first charge-discharge efficiency of the positive electrode, the first charge-discharge efficiency of the lithium-ion battery is equal to the first charge-discharge efficiency of the negative electrode. For example, in an existing lithium-ion battery, the initial charge-discharge efficiency of the negative electrode is lower than the initial charge-discharge efficiency of the positive electrode, and the energy density when the lithium-ion battery is charged and discharged for the first time is relatively small. However, in this embodiment, by mixing the first positive electrode lithium supplement agent and the second positive electrode lithium supplement agent on the positive electrode, and respectively adjusting the mass content percentages of the positive electrode material, the first positive electrode lithium supplement agent and the second positive electrode lithium supplement agent, it is possible to The first charge and discharge efficiency of the negative electrode is greater than or equal to the first charge and discharge efficiency of the positive electrode, so as to achieve the effect of increasing the energy density during the first charge and discharge process of the lithium ion battery. Preferably, when the first-time charge-discharge efficiency of the positive electrode is equal to the first-time charge-discharge efficiency of the negative electrode, the first-time charge-discharge efficiency of the lithium-ion battery can be maximized, thereby achieving the maximum increase in energy density.

Exemplarily, the first discharge gram capacity of the positive electrode material can be expressed by C _{positive discharge} , the first charge gram capacity of the positive electrode material can be expressed by C _{positive charge} , then the first charge and discharge efficiency of the positive electrode material can be expressed by η _positive , and η _positive =C _{positive discharge} / C _{is positively charged} ; the first discharge gram capacity of the first positive electrode lithium supplement can be expressed by C ₁ , and the first charge gram capacity can be expressed by C _{1 charge} , then the first charge and discharge efficiency of the first positive electrode lithium supplement can be expressed by η ₁ , and η ₁ =C _{1 discharge} /C _{1 charge} ; the first discharge gram capacity of the second positive electrode lithium supplement can be expressed by C _{2 discharge} , the first charge gram capacity can be expressed by C _{2 charge} , then the first charge and discharge efficiency of the second positive electrode lithium supplement can be expressed by η ₂ , and η ₂ =C _{2 discharge} /C ₂ charge.

By adjusting the size of the first mass content percentage, the second mass content percentage, and the third mass content percentage, each mass content percentage needs to meet a certain quantitative relationship with the charge-discharge gram capacity of the corresponding material, so as to achieve the first charge-discharge efficiency of the positive electrode equal to The effect of the first charge and discharge efficiency of the negative electrode maximizes the energy density of the lithium-ion battery. Wherein, the quantitative relationship satisfied by each mass content percentage can be expressed by the following formula:

(X _positive × C _{positive discharge} + X ₁ × C _{1 discharge} + X ₂ × C _{2 discharge} ) / (X _positive × C _{positive charge} + X ₁ × C _{1 charge} + X ₂ × C _{2 charge} ) ≤ η _negative

Wherein, η _negative represents the first charge-discharge efficiency of the negative electrode, the first mass content percentage of the positive electrode material can be represented by X _positively , the second mass content percentage of the first positive electrode lithium replenishing agent can be represented by X ₁ , and the third mass content percentage of the second positive electrode lithium replenishing agent The mass content percentage can be represented by X ₂ .

According to the relationship between the gram capacity of the first positive electrode lithium supplementing agent, the gram capacity of the second positive electrode lithium supplementing agent, and the gram capacity of the positive electrode material, and the first mass content percentage, the second mass content percentage and The quantitative relationship that the third mass content percentage satisfies, the following examples will exemplarily illustrate the numerical range of the gram capacity of each active material and the selection of the material.

Optionally, on the basis of the above-mentioned embodiments, the charging gram capacity of the positive electrode material ranges from 100 to 300mAh/g, and the initial charge and discharge efficiency is greater than 80%; the charging gram capacity of the first positive electrode lithium supplementing agent ranges from 400 to 1200mAh /g, the first charge and discharge efficiency range is 0-10%; the charge gram capacity range of the second positive electrode lithium supplement is 200-500mAh/g, and the first charge-discharge efficiency range is 20%-50%.

Specifically, the first positive electrode lithium-supplementing agent has a high initial charging gram capacity and a low initial charging and discharging efficiency, which can greatly increase the energy density of the lithium-ion battery. For example, when the first charge and discharge efficiency of the first positive lithium supplement agent reaches 0, it means that the first positive electrode lithium supplement agent can completely delithiate, that is, during the first charge and discharge process, all lithium ions are extracted, thereby increasing the energy density. The first charge gram capacity of the second positive electrode lithium supplement is between the first charge gram capacity of the positive electrode material and the first charge gram capacity of the first positive electrode lithium supplement, and the first charge and discharge efficiency of the second positive lithium supplement is also between The first charge-discharge efficiency of the first positive electrode lithium supplement and the first charge-discharge efficiency of the positive electrode material, therefore, the second positive electrode lithium supplement can slowly delithiate during the charge-discharge cycle of the lithium-ion battery, thereby making the lithium-ion battery Continuous lithium supplementation is achieved during the charging and discharging cycle, which effectively improves the cycle life.

Exemplarily, the material that satisfies the gram capacity range of the positive electrode material and the first charge and discharge efficiency can be lithium manganese iron phosphate or lithium iron phosphate, etc., for example, the chargeable capacity of lithium iron phosphate is 160mAh/g, and the first charge and discharge efficiency is 95 %; materials that meet the gram capacity of the first positive electrode lithium supplement and the first charge and discharge efficiency range can be selected from any one of lithium ferrite and lithium oxide. For example, the charging gram capacity of lithium-rich lithium ferrite is 750mAh/g, The first charge and discharge efficiency is 5%; the material that meets the gram capacity of the second positive electrode lithium supplement and the first charge and discharge efficiency range can be lithium-rich lithium nickelate or lithium-rich lithium cobaltate, for example, the charging of lithium-rich lithium nickelate The gram capacity is 400mAh/g, and the first charge and discharge efficiency is 40%.

An achievable embodiment, wherein, in the cells of the experimental group in which the positive electrode active material includes the positive electrode material, the first positive electrode lithium supplement and the second positive electrode lithium supplement, the selected positive electrode material has a charging gram capacity of 180mAh/g , the discharge gram capacity is 171mAh/g, the first charge and discharge efficiency is 95%; the charge gram capacity of the selected first positive electrode lithium supplement is 700mAh/g, the discharge gram capacity is 70mAh/g, and the first charge and discharge efficiency is 10%; The selected second positive electrode lithium supplement has a charge capacity of 400mAh/g, a discharge capacity of 160mAh/g, and an initial charge and discharge efficiency of 40%. From the selected corresponding positive electrode material, the first positive electrode lithium supplement agent and the second positive electrode lithium supplement agent, according to the calculation formula satisfied by the mass content percentage of each active material provided in the above examples, the first mass content percentage of the positive electrode material can be calculated. is 94%, the second mass content percentage of the first positive electrode lithium supplement is 2%, and the third mass content percentage of the second positive electrode lithium supplement is 4%. The energy density of the battery cell prepared according to the above-mentioned proportion of the positive electrode active material can reach 191wh/kg during the first charge and discharge process. And in the later continuous charge and discharge cycle process, when the capacity retention rate of the battery cell decays to 70%, the total number of cycles can reach 13,200 cycles. However, for the battery cells made of only positive electrode materials in the control group, the energy density in the first charge and discharge process was 175wh/kg, and when the charge and discharge cycles were continued until the battery capacity retention rate decayed to 70%, the total number of cycles was only for 9400 laps.

It can be seen that the battery cell mixed with the first positive electrode lithium supplement agent and the second positive electrode lithium supplement agent provided by the embodiment of the present invention can effectively improve the energy density of the lithium-ion battery at the time of the first charge and discharge, and the energy density in the continuous charge and discharge cycle Lithium supplementation can be continued during the process, thereby greatly improving the cycle life of lithium-ion batteries.

Optionally, on the basis of the above-mentioned embodiments, the positive lithium-supplementing pole piece further includes: a binder and a conductive agent.

The binder is used to mix the positive electrode material, the first positive electrode lithium supplement agent and the second positive electrode lithium supplement agent evenly, and the conductive agent is used to enhance the conductivity of the positive electrode lithium supplement pole piece.

Specifically, in addition to the positive electrode material and the lithium supplementary material, the positive electrode supplementary lithium electrode sheet also includes auxiliary functional materials, such as binders and conductive agents. The binder has a binding effect, and can bind the positive electrode material with a gram capacity, the first positive electrode lithium replenishing agent and the second positive electrode lithium replenishing agent together, and mix them uniformly. In addition, the binder can also withstand the swelling and corrosion of the electrolyte, withstand the electrochemical corrosion during charge and discharge, and remain stable within the working voltage range of the positive electrode. Exemplarily, the polymer material that can be selected for the binder includes polyvinylidene fluoride (Polyvinylidene fluoride, PVDF), styrene-butadiene rubber (Polymerized Styrene Butadiene Rubber, BR) emulsion and carboxymethyl cellulose (Carboxymethyl Cellulose, CMC), etc. , without limitation here.

The positive electrode active materials in lithium-ion batteries are mostly semiconductor materials or insulator materials, and the conductivity is poor. Therefore, it is necessary to add a conductive agent to increase the conductive contact between the active materials and improve the electronic conductivity. The micro-current is collected between the outer current collectors to reduce the contact resistance of the electrodes and accelerate the moving speed of electrons. The material, morphology, particle size and content of the conductive agent have different effects on lithium-ion batteries. For example, the commonly used conductive agent for lithium-ion batteries can be carbon black, conductive graphite, carbon nanotubes or graphene. This is not limited.

The embodiment of the present invention also provides a battery cell. Fig. 1 is a schematic cross-sectional structure diagram of an electric core provided by an embodiment of the present invention. As shown in FIG. 1 , the battery cell 01 includes: a separator 10 , an electrolyte, a negative electrode sheet, a negative electrode current collector, a positive electrode current collector, and the positive electrode lithium-replenishing electrode sheet as in the above-mentioned embodiments.

The positive lithium-supplementing electrode sheet is arranged on the surface of the positive electrode collector, the negative electrode sheet is arranged on the surface of the negative electrode collector, and the diaphragm is arranged between the positive electrode collector and the negative electrode sheet.

Wherein, referring to FIG. 1, the negative electrode 20 includes a stacked negative electrode sheet and a negative electrode current collector, and the positive electrode 30 includes a stacked positive electrode lithium supplementary electrode sheet and a positive electrode current collector; wherein, FIG. 1 does not show the details of the negative electrode sheet and the negative electrode current collector. structure, as well as the detailed structure of the positive lithium supplementary pole piece and the positive current collector.

During the first charging and discharging process of the battery cell provided in this embodiment, the positive lithium-supplementing pole piece can release a sufficient amount of lithium ions, which greatly improves the energy density of the battery cell. And in the later stage of the charge-discharge cycle, when charging, a certain amount of lithium ions can be extracted from the positive lithium-supplementing pole piece, which can be inserted into the negative pole piece through the electrolyte; The liquid is embedded in the positive lithium supplementary pole piece, so as to realize continuous lithium supplementation and improve the cycle life of the battery cell.

The embodiment of the present invention also provides a lithium ion battery. The lithium-ion battery includes: a casing and the battery core described in the above-mentioned embodiments.

The lithium-ion battery provided in this embodiment includes the cell described in the above embodiment, and has the same beneficial effect as the cell.

The above specific implementation methods do not constitute a limitation to the protection scope of the present invention. It should be apparent to those skilled in the art that various modifications, combinations, sub-combinations and substitutions may be made depending on design requirements and other factors. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims (10)

1. A positive electrode lithium replenishing pole piece, characterized in that, comprising: positive electrode material, a first positive electrode lithium replenishing agent and a second positive electrode lithium replenishing agent; The positive electrode material, the first positive electrode lithium supplement agent and the second positive electrode lithium supplement agent are mixed in the positive electrode lithium supplement pole piece; wherein, the first charge gram capacity of the first positive electrode lithium supplement agent is greater than the The first charge gram capacity of the second positive electrode lithium supplement agent, the first charge gram capacity of the second positive electrode lithium supplement agent is greater than the first charge gram capacity of the positive electrode material; the first discharge gram capacity of the positive electrode material is greater than the first charge gram capacity The first discharge gram capacity of a positive electrode lithium supplement, and the first discharge gram capacity of the positive electrode material is greater than the first discharge gram capacity of the second positive electrode lithium supplement; The first charge-discharge efficiency of the positive electrode material is greater than the first charge-discharge efficiency of the second positive electrode lithium supplement agent, and the first charge-discharge efficiency of the second positive electrode lithium supplement agent is greater than the first charge-discharge efficiency of the first positive electrode lithium supplement agent efficiency. 2. The positive electrode lithium replenishing pole piece according to claim 1, wherein the positive electrode material occupies a first mass content percentage, the first positive electrode lithium supplementing agent occupies a second mass content percentage, and the second positive electrode The lithium supplement occupies the third mass content percentage; The sum of the first mass content percentage, the second mass content percentage and the third mass content percentage is 1. 3. The positive electrode lithium-replenishing pole piece according to claim 2, characterized in that the first charge and discharge efficiency of the positive electrode is less than or equal to the first charge and discharge efficiency of the negative electrode; Wherein, the first charge and discharge efficiency of the positive electrode is the ratio of the actual first discharge gram capacity of the positive electrode to the actual first charge gram capacity of the positive electrode; the actual first discharge gram capacity of the positive electrode is the actual first discharge gram capacity of the positive electrode material, the first The sum of the actual first discharge gram capacity of the positive electrode lithium supplement agent and the actual first discharge gram capacity of the second positive electrode lithium supplement agent; the actual first charge gram capacity of the positive electrode is the actual first charge gram capacity of the positive electrode material, the The sum of the actual initial charge gram capacity of the first positive electrode lithium supplement and the actual initial charge gram capacity of the second positive electrode lithium supplement. 4. The positive electrode lithium-replenishing pole piece according to claim 3, wherein the actual initial discharge gram capacity of the positive electrode material is the product of the first discharge gram capacity of the positive electrode material and the first mass content percentage; The actual first discharge gram capacity of the first positive electrode lithium supplement agent is the product of the first discharge gram capacity of the first positive electrode lithium supplement agent and the second mass content percentage; the actual first discharge gram capacity of the second positive electrode lithium supplement agent The discharge gram capacity is the product of the first discharge gram capacity of the second positive electrode lithium supplement and the third mass content percentage; The actual first charge gram capacity of the positive electrode material is the product of the first charge gram capacity of the positive electrode material and the first mass content percentage; the actual first charge gram capacity of the first positive electrode lithium supplement is the first The product of the first charge gram capacity of the positive electrode lithium supplement agent and the second mass content percentage; the actual first charge gram capacity of the second positive electrode lithium supplement agent is the first charge gram capacity of the second positive electrode lithium supplement agent and the product The product of the third mass content percentage. 5. The positive electrode lithium-replenishing pole piece according to any one of claims 1-4, characterized in that the charging gram capacity of the positive electrode material ranges from 100 to 300mAh/g, and the initial charge and discharge efficiency is greater than 80%; The charge gram capacity range of the first positive electrode lithium supplement is 400-1200mAh/g, and the initial charge-discharge efficiency range is 0-10%; The charging gram capacity of the second positive electrode lithium supplementing agent ranges from 200 to 500 mAh/g, and the initial charging and discharging efficiency ranges from 20% to 50%. 6. The positive electrode lithium-replenishing pole piece according to claim 5, wherein the first positive electrode lithium-replenishing agent is any one of lithium-rich lithium ferrite and lithium oxide; The second positive electrode lithium replenishing agent is any one of lithium-rich lithium nickelate and lithium-rich lithium cobaltate. 7. The positive electrode lithium-replenishing pole piece according to claim 6, wherein the positive electrode material is any one of lithium manganese iron phosphate and lithium iron phosphate. 8. The positive lithium supplementary pole piece according to any one of claims 1-4, further comprising: a binder and a conductive agent; The binder is used to mix the positive electrode material, the first positive electrode lithium supplement agent and the second positive electrode lithium supplement agent evenly, and the conductive agent is used to enhance the conductivity of the positive electrode lithium supplement pole piece . 9. A battery cell, characterized in that it comprises: a separator, an electrolyte, a negative electrode sheet, a negative electrode current collector, a positive electrode current collector, and the positive lithium supplementary electrode sheet according to any one of claims 1-8; The positive lithium-supplementing pole piece is arranged on the surface of the positive electrode current collector, the negative electrode piece is arranged on the surface of the negative electrode current collector, and the diaphragm is arranged between the positive electrode current collector and the negative electrode piece. 10. A lithium ion battery, characterized in that it comprises: a shell and the battery cell according to claim 9.