A kind of method in improve lithium ion battery useful life at low ambient temperaturesTechnical field
The invention belongs to cell art, particularly a kind of method in improve lithium ion battery useful life at low ambient temperatures.
Background technology
Along with the day by day exhausted of traditional energy and its pollution caused are day by day serious, national governments are more and more stronger to the expectation of new-energy automobile, expect that its appearance can alleviate the current increasingly serious energy, ambient pressure that we face.The thus referred important position of key technology-battery technology as new-energy automobile development.Be widely used due to the advantage of lithium-ion-power cell in energy density, power-performance etc.
The continuous expansion of lithium ion battery operation strategies, uses the requirement of condition also further harsh for it.The thing followed is that lithium battery industry must solve, and the stability of battery under how promoting lithium battery useful life at low temperatures and improving low temperature, this is the opportunities and challenges that the industry faces.
In order to solve the problem, lithium electrician author is at change battery active material, and collector thickness, and optimize the aspect such as bath composition and done a large amount of work, makes the high temperature performance of battery be very significantly improved.But also cause the raising of battery cost simultaneously, and make related process more complicated.In addition, on the basis not changing the original formula of lithium battery and structure, by the mode of external heat, battery system is carried out to the method for overall heating and thermal insulation, change the environment for use temperature of battery, also can reach certain effect of optimization.But the mode of external heat, is difficult to the uniformity ensureing often to prop up battery and single internal temperature of battery in battery system, causes stability test to be deteriorated.
Summary of the invention
The object of the invention is to propose on prior art basis a kind ofly to reduce lithium ion battery environment for use temperature, the method in improve lithium ion battery useful life at low ambient temperatures, take the mode of precharge, the method, by before low temperature environment uses, first applies pulse to promote battery own temperature to battery.Namely, before low temperature environment uses, first a certain amount of Pulse Electric is applied to battery, make the temperature that battery self reaches suitable uniformly.While not increasing battery design cost, improve the useful life under battery low temperature environment.
In order to achieve the above object, the present invention adopts following technical scheme:
Low temperature environment use before, first detect battery open circuit voltage (OCV) and temperature (T), then according to open circuit voltage and temperature determine to battery apply inceptive impulse parameter (different system battery parameter is slightly different, and battery parameter refers to Vcritical, R, K), when battery temperature raise 1 ~ 2 DEG C, again according to open circuit voltage and temperature adjustment pulse parameter, until battery temperature reaches suitable serviceability temperature.Although the battery low temperature environment confining spectrum of different system is different, general with 0 DEG C for separation, being below low temperature environment, is more than preference temperature.
The pulse applied can be constant current mode pulse or constant pressure type pulse.
The pulse applied is step by-step impulse.
When adopting constant pressure type pulse, the voltage selected be Vcritical.
Constant current mode pulse method, the electric current I selectedn=[(Vcritical n-OCVn)/Rn] * K, Vcriticalreferring to charge to battery in relevant temperature there is analysing the critical potential of lithium, and OCV is the starting voltage of battery, and R refers to that battery causes the resistance capabilities of polarization when initial state under relevant temperature, and K is current correction coefficient 0.5 ~ 2.0, n is natural number, wherein I1< I2< I3< ... < In.
The time of the individual pulse implemented is 1mS ~ 100S, is preferably 1mS ~ 1S.
The pulse implemented can be rechargeable, discharge type and charging/discharging type pulse, preferably when SOC(is determined by OCV) > 70% time, adopt discharge type; When 30%≤SOC≤70%, adopt charging/discharging type; As SOC < 30%, adopt rechargeable.
Said method is suitable for cell and battery system.
Beneficial effect of the present invention is:
After battery own temperature is brought up to suitable serviceability temperature by step by-step impulse charging/discharging thereof by the present invention, carry out normal discharge and recharge again, this kind of method carries out the selection of pulse current, and along with increasing progressively of battery temperature, pulse current is also corresponding to be increased progressively; Because this kind of method pulse fabric width is narrower, in the process of carrying out pulse, deterioration can not be caused to battery self performance; This kind of method can promote battery temperature within a short period of time, and battery self temperature rise uniformity is good, thus reduces the temperature of battery environment for use, improves battery useful life at low ambient temperatures.
Accompanying drawing explanation
Fig. 1: during the pulse of constant current charge-discharge formula, pulse current, cell voltage and time variations simulation curve (I1pulse current, t1one pulse time);
Fig. 2: during the pulse of constant current charge-discharge formula, stepping electric current and time variations simulation curve;
Fig. 3: constant current charge formula pulse current and time variations simulation curve;
Fig. 4: constant-current discharge formula pulse current and time variations simulation curve;
Fig. 5: battery surface temperature rise is change modeling curve in time;
Fig. 6: during the pulse of constant voltage charge formula, pulse current, cell voltage and time variations simulation curve;
Fig. 7: battery impedance collection of illustrative plates before and after pulse in embodiment 1.
Embodiment
The following examples can make those skilled in the art more fully understand the present invention, but do not limit the present invention in any way.
It is substantially identical that the lithium battery technique that the present invention mentions and instrument and traditional handicraft use, before battery low temperature uses, just take pulsed precharge from the method for heating, make the serviceability temperature that battery reaches suitable, and then improve battery useful life at low ambient temperatures.
First the manufacture craft of lithium ion battery is carried out:
1. the coating of positive pole: positive electrode, carbon black, KS-15, polyvinylidene fluoride (PVDF) are mixed according to a certain percentage, stir, then carries out positive pole coating;
2. the coating of negative pole: graphite, carbon black, LA-132, carboxymethyl cellulose (CMC) are mixed according to a certain percentage, stir, then carries out negative pole coating;
3. will 1., 2. gained positive/negative plate through overbaking, roll-in, cut-parts, combo, lamination, packaging technology, prepare battery;
4. liquid injection process, injects the electrolyte of 1.0mol/LLiPF6 (EC:DEC:DMC=1:1:1) type; 1.0mol/LLiPF6 (EC:DEC:DMC=1:1:1) refers to that LiPF6 is dissolved in the mixed solution of ethylene carbonate (EC), diethyl carbonate (DEC) and the dimethyl carbonate (DMC) that volume ratio is 1:1:1 and forms the electrolyte that concentration is 1mol/L;
5. carry out preliminary filling chemical synthesis technology and obtain resultant battery.
Main embodiment is as following scheme:
Embodiment
Embodiment 1: constant current mode discharge and recharge
Making capacity is according to the method described above the battery of 20Ah, and adopt the mode of stepping constant current charge-discharge pulse, carry out self preheating test to battery, totally 8 pace pulse flow processs from-15 DEG C, single step pulse time 0.6S, temperature interval is 2 DEG C, Vcriticalbe identified as 4.2V, OCV is 3.7V, K is 1.0, Rnknown, by In=[(Vfaceboundary n-OCVn)/Rn] * K calculates In, carrying out I1during pulse, detect battery temperature, when temperature reaches-13 DEG C, transfer I to2pulse, carries out step by-step impulse until battery temperature is greater than 0 DEG C according to following table electric current.
Parameter sees the following form:
By in upper table, t1calculate with pulse number: in 36min, battery temperature is evenly warming up to more than 0 DEG C by-15 DEG C.For whether checking pulse brings injury to battery, after repeating above-mentioned test 30 times, test battery impedance spectrum when OCV is 3.7V at 25 DEG C.As seen from Figure 7, apply pulse current in a short time to heating of battery, battery impedance has growth slightly, but changes not obvious, not can think and damage battery.
Embodiment 2: constant current mode is charged
Making capacity is according to the method described above the battery of 25Ah, and adopt the mode of stepping constant current charge pulse, carry out self preheating test to battery, totally 5 pace pulse flow processs from-10 DEG C, single step pulse time 0.05S, temperature interval is 2 DEG C, Vcriticalbe identified as 4.2V, OCVnfor 3.5V, K are 1.0, Rnknown, by In=[(Vcritical n-OCVn)/Rn] * K calculates In, carrying out I1during pulse, detect battery temperature, when temperature reaches-8 DEG C, transfer I to2pulse, carries out step by-step impulse until battery temperature is greater than 0 DEG C according to following table electric current.
Parameter sees the following form:
By in upper table, t1calculate with pulse number: in 13min, battery temperature is evenly warming up to more than 0 DEG C by-10 DEG C, battery SOC increases by 19.5%.
Embodiment 3: constant pressure type charges
Making capacity is according to the method described above the battery of 30Ah, and adopt the mode of stepping constant voltage charge pulse, carry out self preheating test to battery, totally 5 pace pulse flow processs from-10 DEG C, single step pulse time 0.1S, temperature interval is 2 DEG C, Vcritical 1be identified as 4.25V, OCV1for 3.5V, carry out Vcritical 1during pulse, detect battery temperature, when temperature reaches-8 DEG C, transfer V tocritical 2pulse, carries out step by-step impulse until battery temperature is greater than 0 DEG C according to following table electric current.
Parameter sees the following form:
By in upper table, t1calculate with pulse number: in 11min, battery temperature is evenly warming up to more than 0 DEG C by-10 DEG C, battery SOC increases by 15%.
The above; be only the present invention's preferably embodiment, but protection scope of the present invention is not limited thereto, is anyly familiar with those skilled in the art in the technical scope that the present invention discloses; the change that can expect easily or replacement, all should be encompassed within protection scope of the present invention.Therefore, protection scope of the present invention should be as the criterion with the protection range of claim.