What is lithium pyroborate?
Lithium pyroborate ($\ce{Li2B4O7}$) is the salt of lithium ($\ce{Li}$) and pyroboric acid ($\ce{H2B4O7}$).



Nomenclature

The prefix ortho- designates an acid with the maximum number of hydroxyl ($\ce{OH}$) groups [reference]. For boron ($\ce{B}$), orthoboric acid is $\ce{H3BO3}$ (also written as $\ce{B(OH)3}$ to show that there are $3$ hydroxyl groups).

The prefix pyro- here seems to not match with the usual usage, so I will not be explaining the usual usage here. One common feature between this and the usual usage is that their molecular formulas are multiples of the ortho acid's molecular formulas, minus some water molecules:

$$\ce{4H3BO3 -&gt; H2B4O7 + 5H2O}$$



Gallery

Some proposed structures of lithium pyroborate:





Some proposed structures of pyroboric acid:





The above are modified from two proposed structures of sodium pyroborate, with the first one referenced here and the second one referenced here.