CN101865978A

CN101865978A - Anode and cathode practical volume proportioning of iron-phosphate-based lithium-ion battery and evaluation method of formation condition

Info

Publication number: CN101865978A
Application number: CN201010185105A
Authority: CN
Inventors: 杨智宁; 陈先荣; 谷亦杰; 范建; 张小惠
Original assignee: CHONGQING DAILAIMIKE POWER SUPPLY Co Ltd
Current assignee: CHONGQING DAILAIMIKE POWER SUPPLY Co Ltd
Priority date: 2010-05-24
Filing date: 2010-05-24
Publication date: 2010-10-20

Abstract

The invention provides an anode and cathode practical volume proportioning of iron-phosphate-based lithium-ion battery and an evaluation method of formation condition, relating to the technical field of lithium-ion secondary battery manufacturing. The method comprises the following steps: obtaining the stable charging data of the standard and analyzed iron-phosphate-based lithium-ion battery; calculating the electric quantity/ voltage-voltage numerical value to constant current charging data, and respectively drawing a stable charging differential electric quantity curve; respectively determining the relative position relationship of the specific peak value on the standard and analyzed iron-phosphate-based lithium-ion battery, comparing, and determining the proportioning and formation situation. According to the electrochemistry principle, the method can accurately judge the anode and the cathode practical volume proportioning of an iron-phosphate-based lithium-ion battery, which is favourable for analyzing practical volume development of an anode and cathode material. In the development process of new products, the invention is easy and convenient to realize, saves experiment cost and shortens production periods. The method can judge the formation and side reaction performance level of the iron-phosphate-based lithium-ion battery so as to guide the building of the formation system, improve battery quality and save production cost.

Description

The evaluating method of ferric phosphate lithium cell both positive and negative polarity actual capacity proportioning and change situation

Technical field

The present invention relates to a kind of lithium rechargeable battery manufacturing technology, particularly ferric phosphate lithium cell positive and negative pole material capacity ratio and the evaluating method that changes into degree.

Background technology

At present, the ferric phosphate lithium ion secondary cell has widespread use with its good charge-discharge characteristic, high security and stable circulation performance in fields such as mine lamp, miniature power unit, hybrid vehicle, pure electronic big buses.But this kind cell positive material and lithium ion secondary battery anode material chemical property in the past, physical properties etc. differ greatly, perfect marketization not in addition, different manufacturers are because of the equipment of itself condition, technological level difference, in this battery different capabilities design is produced, design capacity and actual capacity differ bigger, battery plus-negative plate material actual capacity proportioning is difficult to evaluation and test, and can not correctly judge the battery degree of changing into, analysis of causes difficulty is complicated on the galvanochemistry, repeated experiments, cause the ferric phosphate lithium cell R﹠D costs to increase, the production cycle prolongs, and is unfavorable for commercial production.

Summary of the invention

In order to overcome ferric phosphate lithium cell positive and negative pole material actual capacity proportioning situation and battery are changed into the complicated deficiency of degree evaluation and test difficulty, the inventive method is by to accurately the determining of charging capacity ratio under relative position relation and the specific peaks between each peak value on the finished product lithium iron phosphate battery stable state charge capacity differential curve, can accurately evaluate and test the actual performance of positive and negative pole material capacity ratio situation and battery and change into degree, provide a kind of simple, evaluate and test the method for battery plus-negative plate material actual capacity proportioning intuitively, can better analyze positive and negative pole material capacity performance situation and battery and change into degree, save cost, shorten the production cycle.

The technical solution adopted for the present invention to solve the technical problems is as follows:

Determine stable state charging differential electric quantity curve: ferric phosphate lithium cell is comprised that the repeatedly charge-discharge test of first charge-discharge obtains capacity voltage tester data, and testing scheme is: in the constant-current charge stage, range of current is 0.05C ~ 1C; In the constant-voltage charge stage, voltage range is 3.65V ~ 3.8V, and constant voltage is to 0.01C; In the constant-current discharge stage, range of current is 0.05C ~ 1C, and lower voltage limit is 2.5V; Make differential electric quantity curve respectively with above-mentioned each circulation constant-current charge process data, and calculate the corresponding charging capacity C when finishing that charges; Calculate above-mentioned every corresponding charging capacity C1 in differential electric quantity curve upward peak 1 place; Calculate above-mentioned every curve C 1/C value; When above-mentioned adjacent two charge capacity differential curve C1/C values are identical, then this charge capacity differential curve as stable state charge capacity differential curve;

Determine specific peaks relative position relation on the stable state charging differential electric quantity curve: determine the normal battery stable state charging differential electric quantity curve of known both positive and negative polarity actual capacity proportioning with technique scheme, as the canonical reference curve; Determine the stable state charging differential electric quantity curve of identical both positive and negative polarity design capacity proportioning test battery with technique scheme, as analytic curve; Calculate the difference Δ U of reference curve and position, analytic curve upward

peak

2,1 place respectively _Reference, Δ U _Analyze

Described Δ U _Reference, Δ U _Analyze, as Δ U _Analyze＞Δ U _ReferenceThe time, analytic curve both positive and negative polarity capacity ratio is greater than reference curve both positive and negative polarity capacity ratio; As Δ U _Analyze＜Δ U _ReferenceThe time, analytic curve both positive and negative polarity capacity ratio is less than reference curve both positive and negative polarity capacity ratio; Δ U _Analyze=Δ U _ReferenceThe time, analytic curve both positive and negative polarity capacity ratio equals reference curve both positive and negative polarity capacity ratio.According to the proportioning situation, confirmed test battery plus-negative plate material capacity is brought into play situation relatively.

Described charging differential electric quantity curve C1/C ratio, when adjacent two charging differential electric quantity curve C1/C values were identical, Experimental cell changed into fully, on the contrary Experimental cell does not then change into fully.

The invention has the advantages that:

1, the battery charge test data obtain simply, reliable, the charging differential electric quantity curve is calculated and is drawn simply, it is definite accurate to survey the peak value relative position relation on the curve, be convenient to positive and negative pole material capacity performance situation analysis, reduce repeated experiments, reduce R﹠D costs, shorten the production cycle.

2, differential electric quantity curve C1/C ratio is accurate, and method is simple, and a situation arises intuitively to reflect in the battery formation process subsidiary reaction, accurately judges to change into degree, instructs production technology to formulate, and saves cost.

Description of drawings

Fig. 1 is a ferric phosphate lithium cell stable state charging differential electric quantity canonical reference curve synoptic diagram among the present invention;

Fig. 2 is a LiFePO4 Experimental cell stable state charging differential electric quantity analytic curve synoptic diagram among the present invention;

Embodiment

Below in conjunction with drawings and Examples the inventive method is further described:

Fig. 1 is a 4Ah ferric phosphate lithium cell stable state charging differential electric quantity curve for capacity, charging current is a constant current 1C multiplying power, this moment, adjacent two charging differential electric quantity curve C1/C values were identical, curve and area that horizontal ordinate encloses are C1=600mAh before the peak value 1, whole charging capacity C=4506mAh, calculate C1/C=13%, known this battery plus-negative plate capacity ratio is 0.85,

peak value

2,1 relative position relation Δ U _Reference=89.6mV.

Fig. 2 is a 9Ah LiFePO4 Experimental cell stable state charging differential curve for capacity, charging current is a constant current 1C multiplying power, this moment, adjacent two charging differential electric quantity curve C1/C values were identical, curve and area that horizontal ordinate encloses are C1=1050mAh before the peak value 1, whole charging capacity C=9998mAh, calculate C1/C=11%, known this battery plus-negative plate Capacity design proportioning is 0.85,

peak value

2,1 relative position relation Δ U _Analyze=105.4mV.

Δ U _Analyze=105.4mV＞Δ U _Reference=89.6mV, so Experimental cell both positive and negative polarity capacity ratio reality can be estimated the performance of Experimental cell negative pole relative capacity and bring into play relatively poor than the standard cell capacity of negative plates greater than 0.85.

As Experimental cell C1/C=11%, this moment, adjacent two charging differential electric quantity curve C1/C values were identical, and therefore, this ferric phosphate lithium cell changes at this moment fully.

Claims

1. the evaluating method of ferric phosphate lithium cell both positive and negative polarity actual capacity proportioning and change situation, it is characterized in that, may further comprise the steps: the determining of A, stable state charging differential electric quantity curve, ferric phosphate lithium cell is comprised that the repeatedly charge-discharge test of first charge-discharge obtains capacity-voltage tester data, testing scheme is: in the constant-current charge stage, range of current is 0.05C ~ 1C; In the constant-voltage charge stage, voltage range is 3.65V ~ 3.8V, and constant voltage is to 0.01C; In the constant-current discharge stage, range of current is 0.05C ~ 1C, and lower voltage limit is 2.5V; Make differential electric quantity curve respectively with above-mentioned each circulation constant-current charge process data, and calculate the corresponding charging capacity C when finishing that charges; Calculate above-mentioned every corresponding charging capacity C1 in differential electric quantity curve upward peak 1 place; Calculate above-mentioned every curve C 1/C value; When above-mentioned adjacent two charge capacity differential curve C1/C values are identical, then this charge capacity differential curve as stable state charge capacity differential curve, finish formation process situation evaluation and test; B, calculate the difference Δ U of stable state charging differential electric quantity curve reference curve and position, analytic curve upward peak 2,1 place respectively _Reference, Δ U _Analyze, compare Δ U _Reference, Δ U _AnalyzeSize is as Δ U _Analyze＞Δ U _ReferenceThe time, analytic curve both positive and negative polarity capacity ratio is greater than reference curve both positive and negative polarity capacity ratio; As Δ U _Analyze＜Δ U _ReferenceThe time, analytic curve both positive and negative polarity capacity ratio is less than reference curve both positive and negative polarity capacity ratio; Δ U _Analyze=Δ U _ReferenceThe time, analytic curve both positive and negative polarity capacity ratio equals reference curve both positive and negative polarity capacity ratio; According to the proportioning situation, confirmed test battery plus-negative plate material capacity is brought into play situation relatively, finishes the evaluation and test of battery actual capacity proportioning situation.