Toyota unveils 8.7 kWh battery for residential applications
Honestly I'd rather a battery that's super reliable and NOT using any lithium ion inside it in my home.As it doesn't need to move, it can sit there in an unused space and be really heavy. Lead Acid Batteries are a very good fit here (traditionally used as the 12V battery in cars).In Australia you can buy a 12V 42AH (amp-hour) battery for ~$150AUD or $100USD.
20 of these will give you 10kWh @ 240VDC.Couple this with a 6kW solar system and you'd be almost entirely free from grid electricity, especially in summer.You can individually test out the batteries and swap out bad ones. The batteries themselves typically last >5years in a car and I imagine much longer at home where they aren't exposed to high engine temps and large continuous current discharges (engine cranking on start up).