If badly designed, lithium batteries, like all batteries, can be dangerous. However, we design all of our batteries to be safe and secure. All of our batteries have a Battery Management System (BMS) installed, which guards against danger. Our lithium batteries include an external short circuit, which lead batteries lack.
Additionally, in the unlikely event the cells themselves were shorted, externally pierced or crushed, the cells would not achieve a high enough temperature to combust, and any gases given off during this process would be inert. A high enough temperature could not be achieved if the cells were electrically damaged, for example by overvoltage charging, or charging at a low temperature (below freezing).
Our Battery Management System prevents low temperature charging or high voltage charging. On balance, lead batteries would normally be more dangerous since gases given off in fault conditions are explosive and there is no internal short circuit protection or BMS equivalent to protect them.