The hull of a linear code over finite fields is the intersection of the code and its dual, which was introduced by Assmus and Key to classify finite projective planes. A linear code C is called \(h_\ell \) -linear if C has \(\ell \) -dimensional hull. Recently, several papers were devoted to related LCD codes over finite fields with size greater than 3 to \(h_\ell \) -linear codes with \(\ell \ge 1\) . Therefore, the objective of this paper is to investigate an interesting but non-trivial problem, which is to study some properties of binary \(h_1\) -linear codes and establish their relation with binary LCD codes. Some interesting inequalities are thus obtained. Furthermore, we study the largest minimum distance \(d_{one}(n,k)\) among all binary \(h_1\) -linear [n, k] codes. We determine the largest minimum distances \(d_{one}(n,n-k)\) for \( k\le 5\) and \(d_{one}(n,k)\) for \(k\le 4\) or \(14\le n\le 24\) . We partially determine the exact value of \(d_{one}(n,k)\) for \(k=5\) or \(25\le n\le 30\) .