这是因为ngb-accordion是一个directive，不能通过innerHtml渲染。可以通过使用innerHTML属性配合TemplateRef来实现。示例代码如下：

HTML

    
        
            
                Panel content
            
        
        
            
                Panel content
            
        
    

Component

import { Component, ViewChild, ElementRef, OnInit } from '@angular/core';
import { NgbAccordion } from '@ng-bootstrap/ng-bootstrap';

@Component({
  selector: 'app-test',
  templateUrl: './test.component.html',
  styleUrls: ['./test.component.css']
})
export class TestComponent implements OnInit {
    @ViewChild('accordionTpl', { static: true }) accordionTpl: ElementRef;

    accordionHTML: string;

    constructor(private accordion: NgbAccordion) { }

    ngOnInit() {
        this.accordionHTML = this.accordionTpl.nativeElement.innerHTML;
        this.accordionTpl.nativeElement.remove();
    }

    ngAfterViewInit() {
        this.accordion = new NgbAccordion();
        this.accordion.collapseOtherPanels = true;
        this.accordion.toggleable = true;

        const accordionElement = this.accordionTpl.nativeElement.querySelector('ngb-accordion');
        accordionElement.insertAdjacentElement('afterend', this.accordion.ngbAccordion);
    }
}

通过上述方法，可以实现用innerHTML来渲染ngb-accordion的效果。