Lithium-ion batteries are used in multiple devices across several industries, including consumer electronics, medical equipment, transportation and mobile and wireless devices. Their broad appeal is due to the distinct advantages—like high energy density—they offer over conventional battery types. Yet that high energy density, while appealing, also presents safety concerns that manufacturers need to consider. Additionally, the safety and quality of chargers, end products and the interaction of both with the battery are important factors to keep in mind.
There is no one standard that regulates lithium-ion batteries safety and quality. UN 38.3 applies to lithium-ion battery transportation, and standards from IEC, CTIA, UN, SAE and UL regulate batteries specific to the industry where they are used. Certain products may also have additional regulations they must adhere to. Several certification schemes exist to illustrate compliance to industry standards; however, these are typically not mandatory. They generally act as a pre-requisite for acceptance by retailers, manufacturers and service providers. Finally, many OEMs have their own standards in place to mitigate safety risks.
Considering the various standards and certifications is an important first step in lithium-ion battery safety and quality, but it should not be the only one manufacturers take. As technology continues to evolve, and more industries and consumers embrace the use of lithium-ion batteries, it’s more important than ever for manufacturers to better ensure the quality and safety of the batteries, their chargers and end-products.
Failure Analysis
Failure analysis is the mechanical, physical and chemical investigation into the cause and sequence of events that contributes to a product failing to meet a specification or customer expectations or behaving in a manner inconsistent with its designed intent. During a failure analysis, experiments are conducted to gather information about a failed part. The scientific method is also used to hypothesize and evaluate in order to determine the cause and/or causes.
A thorough failure analysis is one of the best ways to check for the quality and safety of lithium-ion batteries, as they can identify failures that happen during development, production and assembly of the batteries, as well as chargers and finished products. When conducting a failure analysis for batteries, it is important to employ a systemic investigation approach, investigating everything from the design, paperwork and physical battery and device to determine the root cause of a failure and identify the means of correction.
Activities at this stage may include a situation appraisal to fully understand the failure and why it occurred, a review of the battery and electronic design, and critical examinations of supporting documents. It may also be important to dissect and analyze the failed cells, as well as other materials, through scans. Testing can also be used to verify the failure, while a technical manufacturing audit can identify deviations from industry design and process best practices.
Audits
Auditing is also an important step for manufacturers to take when it comes to assessing lithium-ion batteries. Technical manufacturing audits, or factory audits, can be helpful in identifying potential failures and mitigating risk. A technical manufacturing audit assesses how well the manufacturer understands and is applying industry standards and best practices. As such, the audit provides the chance to assess the severity and likelihood that deviations from best practices may result in product failures.
During a technical manufacturing audit, it’s important to use an open, questioning method that looks to understand, not critique, current practices. At this point, it’s also a good idea to review design and process failure mode and effect analyses (FMEAs) identified as critical to better assess them. Technical manufacturing audits also provide an opportunity to review scrap, field returns and customer complaints in an attempt to find answers.
System safety evaluation
In addition to looking at the battery and the potential for issues there, it’s also important to consider the entire system at play for a given device. Often times, issues with lithium-ion batteries can result because of a faulty charger or the interaction between battery, charger and device, which may lead to issues like overheating, shorting or fire. Thus, it’s important to evaluate the charger and the end product and examine how all three devices are interacting. This will include design and performance evaluations of the overall “system” (battery, charger and end product) to various national, international and industry standards.
Another important step in helping to ensure a lithium-ion battery functions properly and safely is to determine if the battery being used is appropriate for the device or application. If, during the design or production phase an inappropriate battery is chosen for the device, this will inevitably lead to issues down the road. Along these same lines, a charger that is appropriate for the battery and device will also be important. Keeping these applicability considerations will help ensure the safety and quality of the overall system.
Awareness
The lithium-ion battery space is constantly evolving. New issues continue to come to manufacturers’ attention, standards being revised and updated and emerging regulations. As such, it’s important to continue to stay informed of what is happening within various industries. Continuing education of this type plays an important role in the continued quality and safety of batteries and the devices they service.
The use of lithium-ion batteries offers distinct advantages over conventional battery types, however in order to mitigate the risks associated with their use, it’s important for designers and manufacturers to evaluate, test and analyze the devices and how they are used. As lithium-ion battery use continues to grow and evolved, continued steps like these can help get quality products to market and satisfy consumer demand, creating great opportunity for manufacturers across several industries.
Rich Byczek is the Global Technical Lead of Electric Vehicle and Energy Storage at Intertek, a Total Quality Assurance provider to industries worldwide.
