Lithium batteries unfortunately aren't storage for a grid, they're...capacitors. They add buffer to stabilise the grid and allow transition between sources.
Without any form of meaningful storage (eg pumped hydro) the UK grid will be in trouble.
Still, powering a country though a cold dim calm winter is a lot of power; the UK uses around 800GWh/day of electricity, not counting gas/energy for heating. To store a week or a month or a winter of that is not a solved problem.
You are fundamentally incorrect and either do not understand what a capacitor is or are unwilling to use the correct language in an attempt to prove a point...which unfortunately undermines it. Additionally, smart grids are already capable of transitioning between sources and solar or wind with battery storage are more cost effective than fossil fuel generation today: https://cleantechnica.com/2023/04/15/wind-solar-power-now-th...
Sorry I should have said LIKE a capacitor in terms of function. You are correct they are not a capacitor in terms of design and function. I'd have expected people here be able to understand that.
Fundamentally, at a grid level, lithium batteries can't provide what the average person considers "storage", that is running the grid from said storage. When people hear lithium battery, they think of a phone or laptop - the battery is the sole source of power for 6-12 hours.
On a grid however, lithium batteries provide very short duration stabilisation from "noisy" supply, absorb spikes in generation and boost troughs.
You cannot cost effectivly power the grid from lithium batteries on a still night. Pumped hydro etc are needed to cover prolonged periods of low supply (and absorb prolonged periods of oversupply).
Without any form of meaningful storage (eg pumped hydro) the UK grid will be in trouble.