锂离子电池自放电检测对评估单体锂离子电池或电池组的容量、循环特性和使用寿命具有重要作用。快速检测开路状态下锂离子电池存储电量自发消耗是目前该领域的研究热点。采用开路电压法，通过测量单位时间内锂离子电池的电压降，即自放电K值，表征其自放电程度，设计了锂离子电池自放电K值检测系统。该系统由上、下位机组成，两者之间采用Type-C方式连接，可对锂离子电池进行自放电率检测。以三元锂离子电池为测试对象，对其进行14 d的静置实验，检测静置过程中的自放电K值。测试结果表明该系统不仅缩短了锂离子电池自放电检测时间，而且可准确检测锂离子电池的自放电率。在锂离子电池20%、40%、60%、80%、100% 5种荷电状态，20、50、-20、-40 ℃ 4种温度条件下对锂离子电池进行自放电K值检测。依据K值测试结果，可分析荷电状态和自放电环境温度对锂离子电池自放电率的影响。

Lithium-ion battery self-discharge detection plays an important role in evaluating the capacity, cycle characteristics and service life of a single lithium-ion battery or battery pack. Rapid detection of the spontaneous consumption of stored power of lithium-ion batteries in open circuit conditions is currently a research hotspot in this field. The open-circuit voltage method was used to measure the voltage drop of lithium-ion batteries per unit time, namely the self-discharge K value, to characterize the degree of self-discharge. Additionally, a self-discharge K value detection system for lithium-ion batteries was designed. The system was composed of upper and lower computer computers, connected by Type-C mode, which allowed for the detection of the self-discharge rate of lithium-ion batteries. A ternary lithium-ion battery was used as the test object, and a 14-day standing experiment was conducted to detect the self-discharge K value during the standing process. The test results show that the system not only shortens the self-discharge detection time of lithium-ion batteries, but also accurately detects the self-discharge rate of lithium-ion batteries. The self-discharge K value of the lithium-ion batteries was detected under five states of charge: 20%, 40%, 60%, 80%, and 100%, and at four temperature conditions: 20 ℃, 50 ℃, -20 ℃, and -40 ℃. According to the K-value test results, the influence of state of charge and self-discharge ambient temperature on the self-discharge rate of lithium-ion batteries can be analyzed.