| In recent years,with the rapid development of the new energy vehicle industry,the output of lithium batteries has been increasing.Existing lithium-ion batteries on the market will be retired in a few years.These retired waste lithium batteries contain a large amount of metal and organic matter,which will cause serious environmental pollution if discarded carelessly.If recycled and reused,these old lithium batteries are misplaced treasure trove,containing higher levels of Ni,Co,Li and other metals than natural mineral deposits.At present,the traditional waste lithium battery recovery process mainly includes pretreatment,secondary treatment and deep treatment,among which the first step of pretreatment is the discharge of waste lithium battery.Discharge treatment is mainly divided into physical discharge,chemical discharge and puncture discharge.In practical engineering,Na Cl solution immersion discharge is often used.Although this discharge method has a faster discharge rate,secondary pollution is more serious in the discharge process and after discharge.Therefore,it is of great significance to study the efficient,clean and economical discharge mode of waste lithium battery.In this paper,the immersion discharge of lithium battery was studied by means of comparative study,and four different solution systems were selected: chloride solution,alkaline solution,sulfate solution and organic acid solution.The feasibility of rapid discharge in different solution systems was studied by single factor experiment.The rapid discharge mechanism of different solutions was analyzed by observation and industrial CT.Through the orthogonal experiment of 3 factors and 5 levels,the parameters such as the type,concentration and temperature of discharge liquid were changed to explore the optimal discharge efficiency parameters.The release of heavy metals and fluoride in discharge process was studied by means of filtration membrane sampling/fluoride ion selective electrode method,ICP and GCMS.Finally,the economy of discharge of different solutions is evaluated.The results show that the chloride solution,alkaline solution and organic acid solution can destroy the battery structure in a short time,and make the lithium battery discharge quickly because of short circuit.However,the discharge mechanism of different solutions is different.The chloride solution corrodes the iron alloy shell and aluminum electrode of the battery anode through electrochemical action,so that the internal battery core is completely exposed to the salt solution,resulting in a short circuit of the battery and an instant release of battery voltage.The alkaline solution can dissolve the anode aluminum electrode of the battery,resulting in short circuit of the battery and safe discharge.The organic acid solution only dissolves the insulating gasket between the positive and negative electrodes of the battery shell,thus short-circuiting the battery.Comparing the advantages and disadvantages of the three solutions,it was found that,from the perspective of efficiency,KCl solution(chloride salt solution)of 1mol/L could achieve the fastest discharge at 60℃(2 hours),but it would release heavy metals and fluoride to the environment.From the point of view of environmental protection,the use of L-ascorbic acid solution(organic acid solution)as soon as 4 hours can achieve safe discharge,and cannot release heavy metals and fluoride to the outside world;From an economic point of view,using Na OH solution(alkaline solution)to treat the same number of lithium batteries can achieve safe discharge within 2.5 hours at the fastest,the cost is only 15% of KCl solution and L-ascorbic acid solution,and the release of heavy metals and fluoride is significantly lower than KCl solution.Finally,considering the efficiency,environment and economy,it is concluded that Na OH solution has a good industrial application prospect under the premise of ensuring safe production. |
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