The International Energy Storage Challenge, led by the Faraday Institution, accelerates the delivery of disruptive battery technologies to provide reliable and sustainable energy in developing and emerging economies with on-grid, significant off-grid, and weak grid populations. This is delivered through a research and development programme to reduce the cost and improve the performance of battery energy storage systems (BESS) technologies for use in developing country contexts. This Challenge is led by the Transforming Energy Access (TEA) platform