vue3项目中动态加载组件后element-plus的标签无法渲染

这样，请问要怎么操作才能使element-plus样式显示出来？

组件代码：

<template>
  <div class="test-box">
    <el-row class="p-nav-bar">
      <el-col :span="24">
          <el-row class="mb-4" justify="space-between">
            <el-col :span="20">
              <span class="btn p-name">testspan>
              <el-button type="primary" plain class="btn" @click="new_policy">button1el-button>
              <el-button type="primary" plain class="btn" @click="new_policy">button2el-button>
              <el-button type="primary" plain class="btn" @click="new_policy">button3el-button>
              <el-button type="primary" plain class="btn" @click="new_policy">button4el-button>
            el-col>
            <el-col :span="4">
              <el-button type="primary" :icon="Star" circle class="star right-btn">el-button>
            el-col>
          el-row>
      el-col>
    el-row>
  div>
template>

<script>
import {
  Check,
  Delete,
  Edit,
  Message,
  Search,
  Star,
} from '@element-plus/icons-vue'
import { h, resolveComponent } from "vue";
export default {
  created(){
    return () => {
      const _component_el_button = resolveComponent("el-button")

      return h(
        _component_el_button,
        {
          size: 'small',
          type: 'primary'
        },
        '按钮'
      )
    }
  }
}

组件js:

import { Component, createApp } from "vue";
import { h, resolveComponent } from "vue";
import t from "./test_component.vue";
var instance, unmount;
function mountComponent(RootComponent) {
    const app = createApp(RootComponent);
    const root = document.createElement('div');
    document.getElementById('app').appendChild(root);
    return {
        instance: app.mount(root),
        unmount() {
            console.log("unmount");
            document.body.removeChild(root);
        },
    };
}
// 创建一个组件
export function $add_component() {
    ({ instance, unmount } = mountComponent(t));
    console.log(instance);
}
// 销毁组件
export function $del_component() {
    instance && unmount();
}

调用组件：

<script>
import { $add_component, $del_component } from "@/components/test_component";
export default {
    name: "MainView",
    methods: {
    new_component(){
      $add_component();
      setTimeout(() => {
        // 卸载组件
        $del_component();
      }, 3000);
    }
  },
};
script>

结果：

// main.ts
import { createApp } from 'vue'
import ElementPlus from 'element-plus'
import 'element-plus/dist/index.css' #导入样式
import App from './App.vue'

const app = createApp(App)

app.use(ElementPlus)
app.mount('#app')