Dunno about the power cube, but Fairfax ran an article recently...

Dunno about the power cube, but Fairfax ran an article recently on alternative tech energy storage solutions, including a graphite alloy block used to store heat:
https://www.s*m*h.com.au/business/companies/how-to-solve-our-looming-energy-storage-fix-these-companies-are-exploring-high-tech-solutions-20231211-p5eqmb.html
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“When heated to 653 degrees, they glow orange,” said Mark Croudace. The deputy chief executive of Newcastle-based MGA Thermal was talking about a heavy, rectangular 20-centimetre graphite and alloy block that the company has developed to store heat.
The patented blocks can be stacked and stored in an insulated building, and heated using cheap renewable electricity when it is plentiful in the middle of the day. The heat can be extracted at a later point and converted to high-pressure steam, powering multiple manufacturing processes.
Each block is about five litres in volume, weighs just under 10 kilograms and holds about 1.5 kilowatt-hours of energy.
"The vast bulk of the energy used by industry is in the form of heat,” Croudace said.
Corporate boards are increasingly facing pressure from investors to limit their company’s ongoing contribution to the global climate crisis. The need for rapid decarbonisation and the complexity of cutting carbon emissions from industrial processes is forcing big polluters to look at alternatives.
MGA is banking on a multi-trillion-dollar market emerging between now and 2040 for clean energy in the form of heat, and says it is getting strong interest from offshore manufacturers. Some 450,000 blocks stacked in a six-storey shed would deliver 500 megawatts or energy at a cost of around $100 million, the company estimates.
Industrial processes consume far more of Australia’s energy than residential users, said Croudace, but manufacturers don’t necessarily need decarbonised electricity from the grid – they’re more interested in clean heat or high-pressure steam for making food, chemicals or processing minerals.
“In terms of levelised cost of heat, it [the block technology] is more competitive than gas, electric or hydrogen boilers,” he said.
MGA is backed by venture capital firm Main Sequence and the Australian Renewable Energy Authority. It is building a demonstration plant that will be operational mid next year (2024) to prove the company’s technology can heat, store and discharge energy at scale.
“We are looking to be an Australian deep tech, manufacturing, decarbonisation export play,” Croudace said.

Some have cautioned about graphite losing market share in batteries through other materials such as silicon, though closer reading will show that the amount of graphite displaced in these cells is 10% only at this stage.
There is also sodium ion and solid state coming, but their suitability and ability to scale is questionable.
The downside of technology advances not requiring graphite may be balanced or more so from those that do, like the energy block article above.
Also, the sheer total amount of battery required in an electrified energy storage and transport world IMO means any reduced market share from traditional graphite-anode lithium ion cells will merely smooth the ramp of our material required as the market itself must expand exponentially