Lithium-ion batteries are expected to have a global market value of $47 billion by 2023. They are used in numerous applications, because they offer relatively high energy density (storage capacity), high operating voltage, long shelf life and little "memory effect"—a reduction in a rechargeable battery's maximum capacity due to incomplete discharges in previous uses. However, factors such as safety, charge-discharge cycling and operating life expectancy continue to limit the effectiveness of lithium-ion batteries in heavy-duty applications, such as for powering electric vehicles.