water electrolysis is mind numbingly inefficient + you still have the hydrogen embrittlement problem. Additionally, you then also need a hydrogen fuel cell which relies on some pretty expensive materials like paladium. Lithium ion batteries already are a better fit for small scale grid storage since all you need is the battery and a power management system. Sodium even if its not as good as lithium for density will still be a much better fit for the vast majority of use cases than electrolysis from a maintence and power efficiency perspective.