Yes, you can change your Will at any time. If you are contemplating divorce, you should update your Will before the divorce so that your desires are in effect upon divorce.
If you do not update or have a Will, your surviving spouse may be named to manage your estate and may receive up to 100% of your property, even if you are separated from your spouse.
If you disinherit your spouse before divorce, without a Separation Agreement in place, your spouse may be able to successfully challenge your Will. However, if you and your spouse enter into a valid Separation Agreement that waives inheritance rights, your spouse cannot assert any elective share.
In addition, effective estate planning tools can remove substantial property from your estate to avoid estate claims.