Overheating batteries are a serious risk, in the worst cases leading to fires and explosion. A team has now developed a simple, cost-effective method to test the safety of lithium-ion batteries, which opens up opportunities for research into new and safer batteries for the future. The researchers created an intentionally unstable battery which is more sensitive to changes that could cause overheating. The battery is one-fiftieth the size of conventional batteries, so is less resource intensive and tests can be carried out in a smaller lab environment.