element-plus中，直接应用在页面样式上，

::v-deep .el-table{
    width: 100%;
}
::v-deep .el-table__header-wrapper table,::v-deep .el-table__body-wrapper table{
    width: 100% !important;
}
::v-deep .el-table__body,::v-deep .el-table__footer,::v-deep .el-table__header{
    table-layout: auto !important;
}

效果图：