CN109273771A - Secondary battery - Google Patents

Secondary battery Download PDF

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Publication number
CN109273771A
CN109273771A CN201810953328.3A CN201810953328A CN109273771A CN 109273771 A CN109273771 A CN 109273771A CN 201810953328 A CN201810953328 A CN 201810953328A CN 109273771 A CN109273771 A CN 109273771A
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China
Prior art keywords
secondary cell
battery
cathode
film layer
pole piece
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Granted
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CN201810953328.3A
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CN109273771B (en
Inventor
康蒙
申玉良
王家政
何立兵
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Contemporary Amperex Technology Co Ltd
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Contemporary Amperex Technology Co Ltd
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/058—Construction or manufacture
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2220/00—Batteries for particular applications
    • H01M2220/20—Batteries in motive systems, e.g. vehicle, ship, plane
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

Abstract

the invention relates to a secondary battery, in particular to a secondary battery which comprises a positive pole piece, a negative pole piece, an isolating membrane and electrolyte, wherein the negative pole piece comprises a negative current collector and a negative pole membrane layer which is coated on at least one surface of the negative current collector and contains a negative active material, the secondary battery meets the requirement that α/(β + gamma) is more than or equal to 0.12 and less than or equal to 0.6, wherein α represents the capacity excess coefficient of the battery, β represents the compaction density of the negative pole membrane layer, and the unit g/cm3(ii) a Gamma represents the capacitance per unit area of the negative electrode film layer, unit mAh/cm2. The secondary battery has the characteristics of high energy density, quick charge, long cycle life and the like.

Description

Secondary cell
Technical field
The invention belongs to electrochemical technology fields, it is more particularly related to a kind of secondary cell.
Background technique
New-energy automobile represents the direction of world car industry development.Secondary cell is as novel high voltage, high-energy The rechargeable battery of density has the prominent spies such as light-weight, energy density is high, pollution-free, memory-less effect, long service life Point, to be widely used in new-energy automobile.
However, it is one of the key factor for limiting new-energy automobile and quickly popularizing that the charging time is longer.Come from technical principle It says, cathode is affected to the rapid charging performance of battery, if the unbearable large current charge of cathode, in fast charge, cathode has gold Belong to and being precipitated, while can also generate a large amount of by-products in negative terminal surface, influences the cycle life and safety of battery.
In view of this, being able to solve the above problem, charging rate with higher simultaneously and energy it is necessory to provide one kind Keep the secondary cell of higher energy density and longer cycle life.
Summary of the invention
It is an object of the invention to: a kind of the features such as having both high-energy density, quick charge and long circulation life, is provided Secondary cell.
For achieving the above object, the present invention provides a kind of secondary cell, including anode pole piece, cathode pole piece, isolation Film and electrolyte, the cathode pole piece include negative current collector and coated at least one surface of negative current collector and containing The cathode film layer of negative electrode active material, it is characterised in that: the secondary cell meets following equation:
0.12≤α/(β+γ)≤0.6
Wherein,
The capacity excess coefficient (dimensionless) of α expression battery；
β indicates the compacted density of cathode film layer, unit g/cm3；
γ indicates the capacitance of cathode film layer unit area, unit mAh/cm2。
Compared with the existing technology, the present invention include at least it is as described below the utility model has the advantages that
The present invention passes through the capacitance of reasonably combined positive and negative electrode film layer, the compacted density of cathode film layer in battery design Etc. parameters, so that it is met particular kind of relationship formula, secondary cell can be made while having both good rapid charging performance, good cycle life With higher energy density.
Specific embodiment
The following detailed description of secondary cell according to the present invention.
Secondary cell of the invention, including anode pole piece, cathode pole piece, isolation film and electrolyte, the cathode pole piece Including negative current collector and coated at least one surface of negative current collector and the cathode film layer containing negative electrode active material, Be characterized in that: the secondary cell meets following equation:
0.12≤α/(β+γ)≤0.6
Wherein,
The capacity excess coefficient (dimensionless) of α expression battery；
β indicates the compacted density of cathode film layer, unit g/cm3；
γ indicates the capacitance of cathode film layer unit area, unit mAh/cm2。
Inventor has found that many design parameters of negative electrode active material, cathode film layer and battery are to electricity by numerous studies The cycle performance and fast charge ability in pond have a degree of influence.The design means of existing battery and pole piece need to undergo mostly It makes repeated attempts, but this trial has very big uncertainty, will cause huge waste to design cost.
Inventor summarizes and proposes important relationship formula α relevant to battery design/(β+γ) by many experiments, sends out If the existing relational expression meets the requirement of specific value range, gained battery can have both good rapid charging performance, good circulation longevity Life and higher energy density.This will greatly promote the validity of battery design, time and cost needed for saving research and development.
Preferably, the secondary cell meets: 0.2≤α/(β+γ)≤0.4.
In relational expression α above/(β+γ), α indicates the capacity excess coefficient of battery, i.e., positive/negative plate of the same area is just The ratio of the capacitance of clock synchronization, the capacitance of cathode film layer and positive film layer, α=cathode film layer capacitance/anode film layer Capacitance, dimensionless；β indicates the compacted density of cathode film layer, unit g/cm3；The capacitor of γ expression cathode film layer unit area Amount, unit mAh/cm2。
In relation above formula, α indicates excess coefficient of the cathode pole piece with respect to anode pole piece capacity.When battery charging and discharging, just The active ion of pole is deviate from and is embedded into cathode, and capacity excess coefficient indicates what the receivable capacitance of cathode and anode were deviate from Relationship between capacitance.On the one hand the active ion of anode abjection will form SEI film in negative terminal surface, on the other hand remaining Active ion will be embedded among negative electrode material.The battery designed using different excess coefficients, Man Chongshi, cathode pole piece will be in not Same SOC state.Excess coefficient is bigger, and the SOC state of cathode is lower, and when cathode pole piece is in lower SOC state, expansion and pair are anti- Should be smaller, this will be helpful to the rapid charging performance and life performance of battery.But capacity excess coefficient is excessive to will lead to the energy content of battery Density is too small, meanwhile, in the case where other conditions are constant, cathode pole piece thickness increases, and is unfavorable for the rapid charging performance of battery.It is excellent Selection of land, the scope control of α is in 0.8≤α≤2.0, more preferably 1.0≤α≤1.3.
In relation above formula, β indicates the compacted density of cathode film layer.Positive and negative anodes pole piece is porous electrode, and battery fills Practical discharge process includes liquid phase conduction of the ion in porous electrode, therefore degree is enriched for direct shadow in the duct in porous electrode Ring the fast charge and life performance of battery.In the identical situation of other conditions, the compacted density β of cathode film layer is smaller, then its hole Road structure is more flourishing, is more conducive to the liquid phase conduction of active ion, especially undergoes the electricity repeated expansion of multiple charge and discharge in battery Under critical conditions.But compacted density is too small, will lead to cathode pole piece demoulding picking, and electronic conductance is poor and generate analysis when charging Lithium influences the fast charge and life performance of battery, while can also reduce the energy density of battery.Preferably, the scope control of β exists 0.8g/cm3≤β≤2.0g/cm3, more preferably 1.0g/cm3≤β≤1.6g/cm3。
In relation above formula, γ indicates the capacitance of cathode film layer unit area, i.e., cathode film layer when expression battery completely fills Receivable active ion total amount on unit area.Battery design capacity is identical, and when use a certain fixed multiplying power charging, if electric The capacitance of cathode film layer unit area used in core is bigger, represent the instantaneous activity reached on cathode film surface unit area from Subnumber mesh is more, and the rapid charging performance and cycle performance of battery are poorer；But the capacitance of cathode film layer unit area is bigger, generation Table can receive whole active ions from anode abjection compared with the cathode film layer of small area, and the energy density of battery is higher.It is preferred that Ground, the scope control of γ is in 1mAh/cm2≤γ≤7mAh/cm2, more preferably 2mAh/cm2≤γ≤5mAh/cm2。
Influence when the above analysis is based only upon each parameter individualism to battery, but in actual battery application process, with Upper three parameters be it is interrelated, it is inseparable.Specifically, during circulating battery, because cathode can constantly expand, The capacity of active material also can constantly lose, then α, β and γ parameter in battery design will always be in dynamic change, this hair Three is associated with by the bright relational expression provided, the fast charge and cycle performance of three's joint effect battery, meets 0.12≤α/(β+γ) ≤ 0.6 battery will be with excellent fast charge and cycle performance.If α/(β+γ), less than 0.12 or when being greater than 0.6, battery will It will appear dynamics deterioration, circulation is deteriorated.Preferably, meet 0.2≤α/(β+γ)≤0.4, battery comprehensive performance is more excellent at this time.
In order to comprehensively consider, improve the other performance of battery, usually by the other parameters control of cathode pole piece following excellent It selects in range:
In general, the average grain diameter D50 of negative electrode active material is bigger, the gram volume of negative electrode active material is bigger, then negative electrode film Layer unit-area capacitance amount γ is bigger, and battery actual energy density can be higher, but the rapid charging performance of battery can be poorer.Preferably, The range of the average grain diameter D50 of negative electrode active material is 0.5 μm≤D50≤20 μm, further preferably 3 μm≤D50≤15 μm.
In general, cathode film layer unit area film weight CW is bigger, cathode film layer unit-area capacitance amount γ is bigger, battery Actual energy density can be higher, but the liquid phase conduction resistance of active ion can be bigger when charge and discharge, and the rapid charging performance of battery is poorer. Preferably, the range of the cathode film layer unit area film weight CW is 2mg/cm2≤CW≤18mg/cm2, further preferably Ground, 4mg/cm2≤CW≤10mg/cm2。
In general, the thickness L of cathode film layer is bigger when mono- timing of cathode film layer applied per area weight CW, then represent negative The compacted density of pole film layer is smaller, is more conducive to the liquid phase conduction of active ion when charge and discharge, and the rapid charging performance of battery can be better, But battery actual energy density can be lower.Preferably, the range of the cathode thicknesses of layers L on negative current collector is 0.01mm≤L ≤ 0.3mm, it is further preferred that 0.015mm≤L≤0.15mm.
Negative electrode active material used in cathode film layer of the invention can be various negative electrode active materials commonly used in the art Material, the present invention has no this specifically limited.For example, negative electrode active material used in cathode film layer of the invention can be graphite One or more of material, soft charcoal, hard charcoal, carbon fiber, carbonaceous mesophase spherules, silica-base material, tin-based material, lithium titanate.
The graphite material can be selected from least one of artificial graphite, natural graphite.The silica-base material can be selected from list One or more of matter silicon, silicon oxide compound, silicon-carbon compound, silicon alloy.The tin-based material can be selected from simple substance tin, tin oxygen One or more of compound, tin alloy.
In a preferred embodiment, the negative electrode active material includes graphite material.Wherein the graphite material accounts for The percentage of the negative electrode active material total weight can be higher than 50%, preferably higher than 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, or be about 100%.
In addition, in order to further increase the cyclical stability of negative electrode active material and/or rapid charging performance, in negative electrode active material It is most commonly seen and effective method that material surface, which carries out cladding,.For example, the surface coating layer of negative electrode active material can be soft charcoal, One of hard charcoal, lithium titanate, silica-base material, conductive carbon, polymer are a variety of.The covering material content accounts for graphite after cladding The 1%-20% of material, preferably 1%-10%.
The preparation method of these materials is well known, and can be obtained through commercial channels.Those skilled in the art can be with Appropriate selection is made according to practical service environment.
Various parameters involved in this specification have general sense well known in the art, can be by side well known in the art Method measures.For example, can be tested according to the method provided in an embodiment of the present invention.
The construction of secondary cell of the present invention and preparation method itself are well known.In general, secondary cell is mainly by positive pole Piece, cathode pole piece, isolation film and electrolyte composition, positive and negative anodes pole piece soak in the electrolytic solution, and ion is medium just using electrolyte It is moved between cathode, realizes the charge and discharge of battery.To avoid positive and negative anodes that short circuit occurs by electrolyte, needing will just with isolation film Cathode pole piece separates.The form of secondary cell for example can be using aluminum hull as shell, be also possible to soft-package battery.
It should be noted that the battery of the application can be for lithium ion battery, sodium-ion battery and any other use originally The secondary cell of invention.
Specifically, when battery is lithium ion battery:
Anode pole piece includes plus plate current-collecting body and is arranged at least one surface of plus plate current-collecting body and including positive-active The positive film layer of substance, positive active material can be selected from lithium and cobalt oxides, lithium nickel oxide, lithium manganese oxide, Li-Ni-Mn-O Object, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, transition metal phosphate, LiFePO4 etc., but the present invention is not limited to These materials can also use other to be used as the conventional known material of active substance of lithium ion battery anode.These are just One kind can be only used alone in pole active material, can also be used in combination of two or more.Preferably, positive electrode active materials are optional From LiCoO2、LiNiO2、LiMnO2、LiMn2O4、LiNi1/3Co1/3Mn1/3O2(NCM333)、LiNi0.5Co0.2Mn0.3O2 (NCM523)、LiNi0.6Co0.2Mn0.2O2(NCM622)、LiNi0.8Co0.1Mn0.1O2(NCM811)、LiNi0.85Co0.15Al0.05O2、 LiFePO4、LiMnPO4One or more of.
Specifically, when battery is sodium-ion battery:
Anode pole piece includes plus plate current-collecting body and is arranged at least one surface of plus plate current-collecting body and including positive-active The positive film layer of substance, positive active material can be selected from sodium iron compound oxide (NaFeO2), sodium cobalt composite oxide (NaCoO2), sodium chromium composite oxides (NaCrO2), sodium manganese composite oxide (NaMnO2), sodium ni compound oxide (NaNiO2)、 Sodium NiTi composite oxides (NaNi1/2Ti1/2O2), sodium nickel manganese composite oxide (NaNi1/2Mn1/2O2), sodium ferro manganese composite oxides (Na2/3Fe1/3Mn2/3O2), sodium cobalt-nickel-manganese oxide compound (NaNi1/3Co1/3Mn1/3O2), sodium iron phosphate cpd (NaFePO4)、 Sodium manganese phosphate cpd (NaMnPO4), sodium cobalt phosphate cpd (NaCoPO4), prussian blue material, polyanionic material (phosphorus Hydrochlorate, fluorophosphate, pyrophosphate, sulfate) etc., but the application is not limited to these materials, and the application can also use Other are used as the conventional known material of sodium-ion battery positive active material.These positive active materials can only individually Using one kind, can also be used in combination of two or more.
In the battery of another aspect of the present invention, the specific type and composition of isolation film and electrolyte be not by specific Limitation, can be selected according to actual needs.
Specifically, it is multiple to can be selected from polyethylene film, polypropylene screen, polyvinylidene fluoride film and their multilayer for the isolation film Close film.
It is molten usually using the lithium salts dissolved in organic solvent as nonaqueous electrolytic solution when battery is lithium ion battery Liquid.Lithium salts is, for example, LiClO4、LiPF6、LiBF4、LiAsF6、LiSbF6Equal inorganic lithium salts or LiCF3SO3、LiCF3CO2、 Li2C2F4(SO3)2、LiN(CF3SO2)2、LiC(CF3SO2)3、LiCnF2n+1SO3Organic lithium salts such as (n >=2).Make in nonaqueous electrolytic solution Organic solvent is, for example, the cyclic carbonates such as ethylene carbonate, propene carbonate, butylene, vinylene carbonate, The linear carbonates such as dimethyl carbonate, diethyl carbonate, methyl ethyl ester, the chains ester such as methyl propionate, the rings such as gamma-butyrolacton Shape ester, the chains ether such as dimethoxy-ethane, diethyl ether, diethylene glycol dimethyl ether, triglyme, tetrahydrofuran, 2- methyl four The cyclic ethers such as hydrogen furans, the mixture of the nitriles such as acetonitrile, propionitrile or these solvents.
Hereinafter, briefly explaining secondary cell of the invention by taking lithium ion secondary battery as an example.
Firstly, preparing battery positive pole piece according to conventional method in that art.The present invention for used in anode pole piece just Pole active material is without limiting.In general, in above-mentioned positive electrode active materials, need to add conductive agent (such as carbons such as carbon black Material), binder (such as PVDF) etc..Optionally, other additives, such as PTC thermistor material etc. can also be added.It is logical Often these materials are mixed and are scattered in solvent (such as NMP), are coated uniformly on plus plate current-collecting body after mixing evenly, Anode pole piece is obtained after drying.The materials such as the metal foils such as aluminium foil or expanded metal can be used as plus plate current-collecting body.It is excellent Choosing uses aluminium foil.
Cathode pole piece of the invention can be prepared using the known method of this field.In general, by negative electrode active material And optional conductive agent (such as the carbon materials such as carbon black and metallic particles etc.), binder (such as SBR), other optional additions The materials such as agent (such as PTC thermistor material), which mix, to be scattered in solvent (such as deionized water), after mixing evenly It is coated uniformly on negative current collector, the cathode pole piece containing cathode film layer is obtained after drying.The metals such as copper foil can be used The materials such as foil or expanded metal are as negative current collector.It is preferable to use copper foils.
It is worth noting that, collector can be with double spread also with one side coating when preparing positive and negative anodes pole piece.When negative When the collector double spread of pole, parameter beta, parameter γ are measured both for some single side cathode film layer, and are appointed in two film layers It anticipates one and meets 0.12≤α/(β+γ)≤0.6, that is, think to fall within the scope of the present invention.Similarly, cathode film layer herein Unit area film weight CW and cathode thicknesses of layers L is also to measure for single face film.
Finally, anode pole piece, isolation film, cathode pole piece are folded in order, it is in isolation film between positive and negative anodes pole piece Play the role of isolation, then winding obtains naked battery core；Naked battery core is placed in outer packing shell, injects electrolyte after dry, is passed through The processes such as Vacuum Package, standing, chemical conversion, shaping are crossed, secondary cell is obtained.
Compared with traditional secondary cell, the present invention, which can permit secondary cell, is not reducing cycle life and/or energy Under the premise of density, improve the rapid charge characteristic of battery.Therefore, there is very important meaning for fields such as new-energy automobiles Justice.
Beneficial effects of the present invention are further illustrated with reference to embodiments.
Embodiment
In order to be more clear goal of the invention of the invention, technical solution and advantageous effects, with reference to embodiments The present invention is described in further detail.However, it should be understood that the embodiment of the present invention is of the invention just for the sake of explaining, and It is non-in order to limit the present invention, and the embodiment of the present invention is not limited to the embodiment provided in specification.It is not infused in embodiment The production of the routinely condition of bright specific experiment condition or operating condition, or made by the condition that material supplier is recommended.
One, the preparation for the battery of test
The battery of embodiment 1-16 and comparative example 1-8 are prepared by the following method:
A) the preparation of anode pole piece:
Positive electrode active materials (see Table 1 for details for ingredient), conductive agent (Super P), binder (PVDF) etc. are compared by 96: 2: 2 Example is mixed, and is added solvent (NMP), and stirring obtains anode slurry to system at transparent and homogeneous shape under de-airing mixer effect Material；Anode sizing agent is evenly applied on plus plate current-collecting body aluminium foil；The plus plate current-collecting body for being coated with anode sizing agent dries in the air in room temperature It is transferred to oven drying after dry, then obtains anode pole piece by processes such as cold pressing, cuttings.
B) the preparation of cathode pole piece:
By negative electrode active material (see Table 1 for details for ingredient), conductive agent (Super P), CMC (carboxymethyl cellulose), bonding agent (butadiene-styrene rubber) 94.5:1.5:1.5:2.5 in mass ratio is mixed, with solvent (deionized water) under de-airing mixer effect It is uniformly mixed and is prepared into negative electrode slurry, negative electrode slurry is coated uniformly on negative current collector copper foil, negative electrode slurry is coated with Negative current collector oven drying is transferred to after room temperature is dried, then by cold pressing, cutting etc. processes obtain cathode pole piece.
C) the preparation of electrolyte:
Ethylene carbonate (EC), methyl ethyl carbonate (EMC), diethyl carbonate (DEC) are mixed according to volume ratio 1: 1: 1 It closes, then by sufficiently dry lithium salts LiPF6It is dissolved in mixed organic solvents according to the ratio of 1mol/L, is configured to be electrolysed Liquid.
D) isolation film:
Select 12 microns of polyethylene film.
E) the assembling of battery:
Above-mentioned anode pole piece, isolation film, cathode pole piece are folded in order, are in isolation film between positive and negative electrode pole piece Play the role of isolation, then winding obtains naked battery core；Naked battery core is placed in outer packing shell, by the above-mentioned electrolyte prepared In naked battery core after being injected into drying, by processes such as Vacuum Package, standing, chemical conversion, shapings, lithium ion secondary battery is obtained.
Two, the measurement of parameter
Test 1 battery capacity excess coefficient α
Step 1): the average discharge capacity test of positive film layer.The anode pole piece of the various embodiments described above and comparative example is taken, benefit The sequin of positive film layer is obtained with Lamination mould.It is to electrode with metal lithium sheet, Celgard film is isolation film, is dissolved with LiPF6The EC+DMC+DEC's (ethylene carbonate, dimethyl carbonate, the diethyl carbonate of volume ratio 1: 1: 1) of (1mol/L) Solution is electrolyte, and 6 identical CR2430 type button cells are assembled in the glove box of argon gas protection.Battery pack installs rear quiet 12h is set, constant-current charge is carried out under the charging current of 0.1C, until voltage arrival upper limit blanking voltage xV, then keeps voltage XV carry out constant-voltage charge, until electric current be 50uA, constant-current discharge is finally carried out under the discharge current of 0.1C, until voltage reach Low cutoff voltage yV records the discharge capacity recycled for the first time.The average value of 6 button cell discharge capacities is positive film layer Average discharge capacity.
In each embodiment of the application and comparative example:
When positive electrode active materials are LiFePO4 (LFP), upper limit blanking voltage xV=3.75V, low cutoff voltage yV =2V.
When positive electrode active materials are lithium nickel cobalt manganese oxide (NCM523/NCM811), upper limit blanking voltage xV=4.2V, Low cutoff voltage yV=2.8V.
Step 2): the average charge capacity test of cathode film layer.The cathode pole piece of the various embodiments described above and comparative example is taken, benefit Obtained and above-mentioned steps 1 with Lamination mould) in anode sequin area it is identical and include the sequin of cathode film layer.With lithium metal Piece is to electrode, and Celgard film is isolation film, is dissolved with LiPF6The EC+DMC+DEC of (1mol/L) be (volume ratio 1: 1: 1 Ethylene carbonate, dimethyl carbonate, diethyl carbonate) solution be electrolyte, argon gas protection glove box in assemble 6 CR2430 type button cell.Battery pack stands 12h after installing, and constant-current discharge is carried out under the discharge current of 0.05C, until voltage For 5mV, then carry out constant-current discharge with the discharge current of 50uA again, until voltage is 5mV, then with the discharge current of 10uA into Row constant-current discharge, until voltage is 5mV.Static 5 minutes, constant-current charge is finally carried out under the charging current of 0.05C, until most Whole voltage is 2V, records the charging capacity recycled for the first time.The average value of 6 button cell charging capacitys is the flat of cathode film layer Bulk charge capacity.
Step 3): according to α=above-mentioned cathode film layer average charge capacity (mAh)/above-mentioned positive film layer averaged discharge Battery capacity excess coefficient α is calculated in capacity (mAh).
Test compacted density β (the unit g/cm of 2 cathode film layers3)
Step 1): weighing cathode film quality by standard balance respectively, measure cathode pole piece spreading area by ruler, Then cathode film layer mass area ratio (g/cm can be calculated2)。
Step 2): real density β=cathode film layer unit area quality (g/cm is laminated according to negative electrode film2)/cathode film layer Negative electrode film lamination real density β is calculated in thickness (cm), and wherein cathode thicknesses of layers can be measured by tenthousandth micrometer.
Test capacitance γ (the unit mAh/cm of 3 cathode film layer unit areas2)
Step 1): the cathode film layer for taking in above-mentioned test 1 " the average charge capacity test method of cathode film layer " to measure Average charge capacity.The diameter d that button cell cathode sequin is measured using slide calliper rule, further according to formula π * (0.5*d)2Calculating is asked Obtain the area of button cell cathode sequin.
Step 2): according to capacitance γ=cathode film layer average charge capacity (mAh) of cathode film layer unit area/negative Area (the cm of minimum disk2), cathode film layer unit-area capacitance amount γ is calculated.
Three, battery performance test
Above-described embodiment 1-16 and comparative example 1-8 are tested into every battery performance in following manner.
The test of 1 dynamic performance
At 25 DEG C, the lithium ion battery that embodiment and comparative example is prepared completely is filled with 2.5C, completely puts repetition with 1C After 10 times, then lithium ion battery completely filled with 3C, then disassembles out cathode pole piece and observe the analysis lithium situation on cathode pole piece surface. Wherein, negative terminal surface analysis lithium region area be considered slightly analyse lithium less than 5%, negative terminal surface analysis lithium region area for 5% to 40% is considered that moderate analyses lithium, and negative terminal surface analysis lithium region area is greater than 40% and is considered seriously to analyse lithium.
The test of 2 cycle performances:
At 25 DEG C, the lithium ion battery that embodiment and comparative example is prepared is put with the charging of 2C multiplying power, with 1C multiplying power Electricity carries out full be full of and puts loop test, until the capacity attenuation of lithium ion battery records circulation time to the 80% of initial capacity Number.
3 actual energy density measurements
At 25 DEG C, the lithium ion battery that embodiment and comparative example is prepared completely is filled with 1C multiplying power, is expired with 1C multiplying power It puts, records actual discharge energy at this time；At 25 DEG C, weighed using electronic balance to the lithium ion battery；Lithium ion Battery 1C actual discharge energy and the ratio of lithium ion battery weight are the actual energy density of lithium ion battery.
Wherein, when actual energy density is less than the 80% of expected energy density, it is believed that battery actual energy density is very low； When actual energy density is more than or equal to the 80% of expected energy density and is less than the 95% of expected energy density, it is believed that battery is practical Energy density is relatively low；Actual energy density is more than or equal to the 95% of expected energy density and is less than the 105% of expected energy density When, it is believed that battery actual energy medium density；Actual energy density, which is more than or equal to the 105% of expected energy density and is less than, is expected Energy density 120% when, it is believed that battery actual energy density is higher；Actual energy density is the 120% of expected energy density When above, it is believed that battery actual energy density is very high.
Four, each embodiment, comparative example test result
It prepares the battery of embodiment 1-16 and comparative example 1-8 respectively according to the method described above, and measures various performance parameters, tie Fruit see the table below.
Table 1
From the test result of table 1 it can be seen that
Embodiment 1-11 and comparative example 1-2 has investigated living as positive electrode active materials, graphite as cathode using LiFePO4 When property material, the ratio cc/influence of (β+γ) for battery performance.It was found from the data of these embodiment and comparative examples: when 0.12 When≤α/(β+γ)≤0.6, battery have simultaneously good rapid charging performance (fast charge test in do not analyse lithium or only slightly analysis lithium) and Cycle performance (cycle-index is no less than 2000 times).As α/(β+γ)>0.6 or α/(β+γ)<0.12, such as 1,2 institute of comparative example Show, serious analysis lithium occurs in battery and cycle-index only has several hundred times.The α of embodiment 1,10,11/(β+γ) value close to critical value, They show slightly to analyse lithium when fast charge is tested, and cycle performance preferably (cycle-index is higher than 2000 times).In addition, from implementation Example 3-7 can be seen that when meeting 0.2≤α/(β+γ)≤0.4, and battery is without analysis lithium, and cycle life is excellent, and (cycle-index is higher than 4000 times), and actual energy medium density, battery comprehensive performance are best.Therefore, in order to guarantee battery rapid charging performance and cyclicity It can, it is necessary to ensure that 0.12≤α/(β+γ)≤0.6；When especially 0.2≤α/(β+γ)≤0.4, performance is best.
When embodiment 12-16 and comparative example 3-8 has investigated different positive electrode active materials, negative electrode active material combination, than Value α/the influence of (β+γ) for battery performance.It can be seen that formula α proposed by the present invention/(β+γ) from these experimental datas It is widely applicable for a variety of different anodes, negative electrode active material combination；As 0.12≤α/(β+γ)≤0.6, battery is simultaneously With good rapid charging performance and cycle performance；When especially 0.2≤α/(β+γ)≤0.4, performance is best.For example, embodiment 15 and comparative example 3-4 has been investigated using graphite as negative electrode active material, LiNi0.5Co0.2Mn0.3O2(NCM523) living as anode When property material, the ratio cc/influence of (β+γ) for battery performance.Embodiment 15 and comparative example 3-4 the experimental results showed that, it is above-mentioned Conclusion is still set up, in order to guarantee battery rapid charging performance and cycle performance, it is necessary to ensure that 0.12≤α/(β+γ)≤0.6；Especially When it is 0.2≤α/(β+γ)≤0.4, performance is best.Similarly, embodiment 14 with the comparison of comparative example 5-6, embodiment 16 with The comparison of comparative example 7-8, has still obtained same conclusions.
Also need supplementary explanation, the according to the above description announcement and guidance of book, those skilled in the art in the invention It can also make appropriate changes and modifications to the above embodiments.Therefore, the invention is not limited to be disclosed above and describe Specific real mode, some modifications and changes of the invention are also fallen into scope of protection of the claims of the invention.In addition, Although using some specific terms in this specification, these terms are merely for convenience of description, not to structure of the present invention At any restrictions.

Claims (10)

1. a kind of secondary cell, including anode pole piece, cathode pole piece, isolation film and electrolyte, the cathode pole piece includes negative Pole collector and coated at least one surface of negative current collector and the cathode film layer containing negative electrode active material, feature exist In: the secondary cell meets 0.12≤α/(β+γ)≤0.6；Wherein,
α indicates the capacity excess coefficient of battery, dimensionless；
β indicates the compacted density of cathode film layer, unit g/cm3；
γ indicates the capacitance of cathode film layer unit area, unit mAh/cm2。
2. secondary cell according to claim 1, it is characterised in that: secondary cell satisfaction 0.2≤α/(β+γ)≤ 0.4。
3. secondary cell according to claim 1, it is characterised in that: the range of the parameter alpha is 0.8≤α≤2.0, excellent Selection of land, 1.0≤α≤1.3.
4. secondary cell according to claim 1, it is characterised in that: the range of the parameter beta is 0.8g/cm3≤β≤ 2.0g/cm3, it is preferable that 1.0g/cm3≤β≤1.6g/cm3。
5. secondary cell according to claim 1, it is characterised in that: the range of the parameter γ is 1mAh/cm2≤γ≤ 7mAh/cm2, it is preferable that 2mAh/cm2≤γ≤5mAh/cm2。
6. secondary cell according to claim 1, it is characterised in that: the cathode thicknesses of layers L meet 0.01mm≤L≤ 0.3mm, preferably 0.015mm≤L≤0.15mm.
7. secondary cell according to claim 1, it is characterised in that: the cathode film layer unit area film weight CW's Range is 2mg/cm2≤CW≤18mg/cm2, it is preferable that 4mg/cm2≤CW≤10mg/cm2。
8. secondary cell according to claim 1, it is characterised in that: the average grain diameter D50's of the negative electrode active material Range is 0.5 μm≤D50≤20 μm, it is preferable that 3 μm≤D50≤15 μm.
9. secondary cell according to claim 1, it is characterised in that: the negative electrode active material be selected from graphite material, One or more of soft charcoal, hard charcoal, carbon fiber, carbonaceous mesophase spherules, silica-base material, tin-based material, lithium titanate.
10. secondary cell according to claim 9, it is characterised in that: the negative electrode active material includes graphite material, silicon One or more of sill.
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