Lithium polyborate

A polyborate, LigBgOj, is obtained in crystalline form by heating lithium carbonate with excess of boric acid at 500° to 600° C. for a long time.6... 

Boric acid is a relatively weak acid compared to other conunon acids, as illustrated by the acid equilibrium constants given in Table 4. Boric acid has a similar acid strength to sihcic acid. Calculated pH values based on the boric acid equihbrium constant are significantly higher than those observed experimentally. This anomaly has been attributed to secondary equilibria between B(OH)3, B(OH)4, and polyborate species. Interestingly, the aqueous solubihty of boric acid can be increased by the addition of salts such as potassium chloride and sodium sulfate, but decreased by the addition of others salts, such as the chlorides of lithium and sodium. Basic anions and other nucleophiles such as fluorides and borates significantly increase boric acid solubility. 

The similar shapes of the envelopes of vibrations associated with trigonal (1300-1500-cm ) and tetrahedral (850-1100-cm ) borons in partially hydrolyzed lithium tetraborate (Fig. 37b) and the 120-72 hour product species (Fig. 37c) indicate that the polyborate species formed during the latter stages of aging are structurally similar to partially hydrolyzed lithium tetraborate. The strong bands at about 930 and 1175 cm , present only in the partially hydrolyzed lithium tetraborate spectrum, were assigned to B-O-H out-of-plane and in-plane bending, respectively, on the basis of D2O and H2 0 hydrolyses [185]. 

Zhu, Y.S., Xiao, S.Y., Shi, Y, Yang, Y.Q., Wu, Y.P. 2013. A trilayer poly(vinylidene fluoride)/polyborate/poly(vinylidene fluoride) gel polymer electrolyte with good performance for lithium ion batteries. 1 7790-7797. 

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