One reason is that the world's Lithium Ion (or Lithium-anything) plants have been at optimum capacity for years supplying, especially, the US forces in support of various wars. (Because their preference is for primary batteries, whereas others use rechargeables). It only takes a small glitch, like a quality failure, to run into supply problems. There have been numerous such failures, one after the other; notably the complete recall and destruction of both cheapo batteries you get in laptops (Dell, Sony, HP to name but three) and expensive ones used by the military. The notable example in the latter category was as a result of a huge fraud, whereby the company crimped the cases instead of welding them. Water got in. As they didn't pot the state of charge / management electronics inside, the water shorted them. The batteries blew up and injured many troops, leading to a total recall and 3 years to replace them. If you watch Blackhawk Down, there is a scene where, in the background, a radio operator experiences what looks like a huge firework going off in his hand. In the movie it is unexplained, but that is a Li-Ion battery being hit by a round. Water ingress has the same effect. Major injuries. Just one explanation from personal experience. Another will be the Japanese tsunami a couple of years ago. PC Hard Drives were similarly in short supply.