挥发除硼-硫酸锂重量法测定锂硼合金中锂

锂硼合金中锂元素的含量对电池的电化学性能起着决定性作用。而使用重量法测定锂时,流程较长,且大量共存的硼干扰锂的测定。试验探究了先使用甲醇除硼再采用硫酸锂重量法测定锂硼合金中锂的方法。样品经稀硝酸溶解后,加入2.0mL无水甲醇,于90℃左右恒温水浴锅中挥发除硼,然后加入2.0mL硫酸(1+1)和少量水溶解盐类,转移至铂坩埚中,高温加热至硫酸烟冒尽,将铂坩埚移入800℃马弗炉中灼烧3h,使锂生成硫酸锂并恒重、称量,并用电感耦合等离子体原子发射光谱法(ICP-AES)测定固体中的氧化硼和硫酸镁的含量以修正测定结果。方法用于测定3种锂硼合金实际样品中锂,结果的相对标准偏差(RSD,n=11)为0.34%～0.56%;加标回收率为98%～103%。

Determination of lithium in lithium-boron alloy by lithium sulfate gravimetry after boron removal via volatilization

The content of lithium in lithium-boron alloy plays a decisive role in the electrochemical performance of batteries. When lithium is determined by gravimetry, the process is long and the determination is interfered by a large number of coexisting boron. The determination method of lithium content in lithium-boron alloy by lithium sulfate gravimetry after removing boron with methanol was investigated in experiments. The sample was dissolved by dilute nitric acid. Then 2.0mL of anhydrous methanol was added. The solution was heated in thermostatic water bath at 90℃ to remove boron via volatilization. Then 2.0mL of sulfuric acid (1+1) and a small amount of water were added to dissolve the salts. The solution was transferred into platinum crucible and heated at high temperature until the sulfuric acid smoke was exhausted. The platinum crucible was transferred into muffle furnace at 800℃ and heated for 3h. Lithium was converted to lithium sulfate. After constant weight, the contents of boron oxide and magnesium sulfate in solid were determined by inductively coupled plasma atomic emission spectrometry to modify the determination results. The proposed method was applied for the determination of lithium content in three actual lithium-boron alloy samples. The relative standard deviations (RSD, n=11) of determination results were between 0.34% and 0.56%. The spiked recoveries were between 98% and 103%.